Note: Descriptions are shown in the official language in which they were submitted.
~g;239
BACKGROU~D OF T~ TION
Laser scanning techniques for writing or print~ng
on~a medium sensitive to the laser beam ha~e been disclosed
in the prior art as shown, for example, in U. S. Patent
~o. 3,922,485. In general, the laser beam is intensity
modulated in accord~nce with information to be printed
o~ a receiv~ng medium, the modulated laser beam be~ng
directed to a ro~ating scanner, or reflector, such as a
multi-faceted polygon. The rotat~ng scanner in tusn
causes the ~odulated laser beam to scan, in sequence,
across a sensitive medium located a distance away from
the scanner. The ~formation conta~ned ~n the intensity
dulated laser beam can be directly written on the medium
if the medium is sensiti~e to the lases beam, or in an
alternative embodiment, the laser beam can selectively
, such as a photoconductor
discharge a chasged insulating or semiconducting surface/
in accordance with ~he intensity of the beam. In the
alt-rnative embodiment, the degree of charge dissipation
corresponds to the information contained in the intensity
of the laser beam. The areas of the medium which are not
dischar~ed by the laser beam are subsequontly developed,
for examp~e, by standard xerographic te~iques.
Present day copiers which are commercially
available which utilize the xerographic process incl~de
a platen upon which the document to be re~roduced is
placad, the platen being flat or curved. The document
is generally flood illuminated or scanned with light
and the raflections therefrom are imaged via a copy lens
to a charged photocon-duc.ive medium to discharse the
medium in accordance with the image fcrmed on the
document.
~he Telecopier~ 200, a facsimile transceiver
-2-
manufactured by the Xerox Corporation, Stamord,
Connecticut, directs re~lections from a laser scanned
document onto a photosensitive transducer, ~he electrical
signal output thereof being transmitted to another
location and used to modulate a laser beam to reproduce
the scanned document. ~owever, the Telecopier 200 is
generally not considered a copier type device since,
intOE alia, a sc G ing platen and other copier ~eatures
are not a~ailable.
Although copiers now commercially available are
not adapted to utilize scanning techniq~e to ~can a
document placed on the copier platen line by line to
produce a serial bit stream correspondlng to the scanned
information (i.e. a ra~ter type scann~ng system), it
would be advantageou~ if ~u~h copier~ could ~e modi~ied
to incorporate the laser printing technique disclosed,
for example, in the a~orementioned p~tent, the modified
copier ~hus re~uiring a system which provide~ ~or two-
d~men~ional raster input scanning. A system for two-
dimensional raater input scanning which utilizes a
laser, i9 d~scribed, for example, in U.S. Patent ~o.
3,970,359. U. S. Patent No. 4,012,585, issued
March 15, 1977 assigned to the a~signee of the
present invention, provides a flying spot scanning
sys~em which is capa~le o~ scanning an unmod~lated beam
to a reading station for reading a stationary document
and a modulated beam to an imaging station for, inter
alia, reproducing the scanned document thereat~
The availability of a copier which utilizes
two-dimensional input scanning, such as the raster-
type input scanning of a document placed on a
--3--
platen and laser scanning techni~ues for wri~lng on-a~
laser sensitive medium would pro~ide many advantages
inherent with the use of lasers and raster type input
scanning, such as increase~ copying speeds and reso-
lution. In particular, it would be advantageous if an
intermediate storage medium was provided between the
~nput and output scanning stations to allow ~or mani-
pulation and storage of the ~canned information, and,
in partic~lar, to provide for electronic precollation
which electronically arranges representations of images
to allGw collated set~ of documents to be reproduced.
Other desirable feature~ of such a copier would ~nclude
input scan reversal for alternate bound pzge3 during
bound volume scanning, synchronization of the system by
a clocX associated with the storage member, a synchronous
3~ system reducing the size and cost of a ~ buffer
a~sociated therewith, input/output interleaving with a
print interrupt feature, image centering and edge fadeout
for image reduction, and independent magnification~demagni-
fication by separately variable raster spacing.
SUMMA~Y OF ~ PRESENT I~VENTIO~
The present invention provides a reproduction
scanning system hav~ng intermediate storage between
lnput and output scann~ng stations wherein an input
document is scanned ln irst and second directions, the
first direction being orthogonal to said second direction,
and the electrical signals representation of information
on said scanned document being stored on an intermediate
storage member, preferably a magnetic disc, for manipulation,
storage, or other signal processing via a synchronizing
buffer. The information stored in the storaga member
lil~`239
may be read out via the synchronizing buffer and reproduced
on a reproducing medium which may, for example, be incor-
porated in a xerographic processor. Other system features
include input scan reversal for alternate bound pages
during bound volume scanning, synchronization of the entire
system by a clock associated with the storage member,
input/output interleaving with a print interrupt feature,
image centering and edge fadeout for image reduction and
independent magnification/demagnification by separately
variable raster spacing.
OBJECTS OF THE PRESENT INVENTION
It is an object of an aspect of the present
invention to provide a reproduction scanning system having
intermediate storage between input and output scanning
stations.
It is an object of an aspect of the present
invention to provide a reproduction scanning system having
a storage member for writing information thereon, said
input information being derived from an input scanning
station and directed to an output scanning station wherein
the information is reproduced.
It is an object of an aspect of the present
invention to provide a reproduction scanning system wherein
an input document is scanned in mutually orthogonal direc-
tions, the scanned information being stored in a storagemember, such as a magnetic disc memory via a synchronizing
buffer, the stored information being read out from the
storage member through the synchronizing buffer and directed
to an output scanning station wherein the information
is reproduced.
It is an object of an aspect of the present
_5_
239
invention to provide a system of the type described herein-
above wherein the input scan may be reversed, electro-
mechanically in one direction and electronically in the
other direction when an alternate page in a bound volume
is being input scanned.
It is an object of an aspect of the present
invention to provide a system of the type described here-
inabove wherein the system is synchronized by a clock
associated with the magnetic disc storage member.
It is an object of an aspect of the present
invention to provide a system of the type described here-
inabove wherein the reproduced image is centered by using
edge fadeout techniques when an input image is to be reduced
in size on an output medium, the reduced image being smaller
in size than the output medium.
It is an object of an aspect of the present
invention to provide for magnification or demagnification
in one scan direction which is independent of the magnific-
ation or demagnification in the other scan direction in
the system described hereinabove by separately varying
the spacing of the input scan i.e. variable raster spacing.
It is an object of an aspect of the present
invention to provide a system of the type described here-
inabove wherein input scanning of a first original (document)
and output printing (scanning) thereof is interleaved
and includes a print interrupt feature to allow a second
original to be input scanned.
Various aspects of the invention are as
follows:
~119Z39
A scanning system having the capability of scan-
ning originals having images formed thereon in either a
normal or inverted mode of operation such that electrical
signals r.epresenting the scanned images can be stored in
storage means such that when the scanning system reads
the stored representations of the images to reproduce the
images on a recording medium the reproduced images each
having the same image sense comprising: first means for
scanning said originals in a first direction in the
normal mode and in a second direction, opposite to said
first direction, in the inverted mode, second means for
scanning said originals in a third direction, which is
orthogonal to said first and second directions whereby
said originals are completely scanned with light, means
for converting the light reflected from said originals
into corresponding electrical signals as the originals are
scanned on a line to line basis, buffer memory means for
storing said electrical signals in the order in which the
electrical signals are generated, and means for unloading
said electrical signals stored in said buffer memory
means into said storage means in a se~uence determined
by whether the scanning system is in the inverted or
normal mode of operation.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention
as well as other objects and further features thereof,
reference is made to the following description which is
to be read in conjunction with the following figures
wherein:
-6a~
39
Figure 1 shows in simplfied form-~ an~optical:
arrangement which may be utilized in the present
invention
Figure 2 is a simplified block diagram of the
overall system of the present invention;
Figures 3A and 3B illustrate a dlsc surface and a
typical record~ng patte~n formed on the disc which may
be utilized in the present invention,
Figures 4A and 4B are m~re detailed block diagrams of
the system of ~he present invention:
Figure 5 illustrateq in more detail the
operatio~ of the synchronizing buffer which comprises
a portion of the system of the present invention,
' Figure 6 is a more detailed block diagram of an
output shi~t register which may be utilized in the
present invention, and
Figures 7A and 7B illustrate how a reduced image may be
centered on an output n~Ylium.
DESC~rPTIO~ OF I~IE P~LEElERURED EIIBODI~rE~rr
Referring now to Figure 1, a simpli~ied
representation of an optical system which may be
utilized in the present Ln~ention is shown. Light
sources 10 and 12 provide original beams 14 and 16,
respectively, for utilization by,the scanning system.
Light sources 10 and 12 are preerably lasers which provide
collimated beams of monochromatic light, laser la comprisins
a helium-cadmium laser which generates blue laser light
at a wavelength of 4416A and laser 12 com?rises a heli~m-
neon laser wnich generates red laser light at a wavelensth
of 6328A. The use of the t~o las~r beams ensures that
the document scanner is not insensitive at the wavelensths
-7-
~l~S?39
of lasers lO or 12 and hence, the system is suitable for
detecting light fluxes reflected from multi-colored documents
in addition to the fact that a choice of laser beams is avail-
able for forming information on a laser sensitive medium.
Light beam 14 is incident upon beam splitter 18 which
directs a portion of light beam 14 to dichroic mirror 20.
Light beam 16 is also incident on dichroic mirror 20, which
is positioned to reflect the flux in beam 14 as a combined
beam 22 (combined with transmitted beam 16). Beam 22 is
incident upon pre-image cylinder lens 24 which transmits
the beam to mirror 26 which directs the beam to a rotating
scanner 28 via a split doublet 30. The portion of beam 14
transmitted by beam splitter 18 is incident on modulator
32 which may either be an acousto-optic or electro-optic
type device, the output thereof being incident on scanner
28 via pre-image lens 34, mirror 36 and split doublet 30,
the split doublet 30 allowing the separate beams incident
thereon on the platen 62 or drum 76. Rotating scanner 28,
shown as comprising a polygon having a plurality of reflect-
ing facets 38, is driven by motor 40 via drive shaft 42.
Scanner 28 rotates in the direction of an arrow 44causing the lase. spot (combined laser beam) incident there-
on to deflect in the x- direction at mirror 43, the output
beam being directed to a movable scanning assembly 45,
shown in a simplified representational form, which
comprises mirror 46, cylinder lens 48, mirror 50,
bidirectional motor 52 having a stepped pulley 53 on its
output shaft, cables 54 and 55 and pulleys 56 and 57.
Elements 48 and 50 are rigidly affixed to cable 54,
--8--
X
111~3~39
element 46 being a~fixed to cable 55~element 46 bei~g
driven at 1/2 the speed of elements 48 and 50 to maintaLn
a constant focal length between the platen 62 and mirror
43. This techni~ue is generally referred to as 1/2 rate
mirror scan, such a technique being disclosed in ~.S.
Patent ~o. 3,970,359~
~ scan spot 58
i9 produced which moves along scan line 60, formed in
the x-direction at platen 62, as scanner 28 continue-
~to rotate. Although not shown in the figure, a document,
or a page in a bound volume, to be scanned is placed face
dcwn on the top sur~ace o~ transparent platen 62. Since ..
motor S2 is bidirectional, the direction of y scan is
~electable by an ~perator by appropriate activation of
bu.ttons formed on an operator's panel 92 (shown schem-
atically in Figure 2~ which in turn cause~ a system
controlli~g microprocessor 90 (Figure 2) to generate the
appropriate control signals. As will be set forth herein-
after, the partic~lar scan direction s~lected is determined
by the type of input being s~anned, alternate pages of a
bound volume generally re~uiring r~versal of the normal
scan direction~
When a document is placod face down on platen
62, it is scanned by the two color laser beam spots 22,
the document reflecting the incident radiation flux in
accordance with the document information being scannedO
A fraction o~ the reflected flux is detect-d by one or
more photom~lltiplier tubes (or other photosensiti~e
device) represented by a single photomultiplier tube 66
_9_
1119239
located under the platen 62 via mirror 64. The photo-
multipliers convert the variation in intensity of the
reflected laser beam into electrical information signals
which may be transmitted to an intermediate storage
device 96 via a synchronizing buffer 98 (shown in
Figures 2 and 4) and thence to a recording device via the
intermediate storage device, synchronizing buffer and mod-
ulator 32 for producing a copy of the document scanned
as will be explained hereinafter. The scanner 28 and scan
system 45 are arranged to scan the material on platen 62
in a manner whereby a plurality of scan lines 60 are gener-
ated across the width of platen 62 such that the material
on the transparent platen is completely scanned. In
essence, the scanning path is as follows. The beam
reflected from mirror 43 passes under elements 48 and 50,
is reflected by mirror 46 (approximately one-half the light
is reflected, the other half being lost) and passes through
lens 46 and is reflected by mirror 50 to platen 62, light
reflected from the document on platen 62 is incident on
mirror 50, passes through lens 48 and is incident on mirror
46, approximately half the light passing therethrough and
being incident on mirror 64. This light beam is then
reflected down to photomultiplier tube 64.
It should be noted that the present invention
can be adapted to utilize other input scanning techniques,
such as arrays of phototransistors, charge coupled devices
(CCD~ or MOS photodiodes. The use of either type array
(the reflections from the document on platen 62 being imaged
thereon) in image sensors has been disclosed in the prior
art as for example, in an article by R. Melen, in Electronics,
May 24, 1973, pages 106-111
Although the input scanning techniques described
-10-
'
111~;Z39
hereinabove are fixed platen scanners (document stationary
on platen) it is to be noted that the system can be arranged
such that the input document moves along the Y direction
of the platen 62, the input scanning mechanism thereby
being stationary.
As shown in Fig. l, the single beam reflected
from mirror 36 is also incident on the facets 38 of scanner
28 and caused to scan mirror 70 which directs the beam
to mirror 72, mirror 72 in turn scanning the incident beam
on cylinder lens 74. Cylinder lens 74 focuses the beam
on a recording member 76, such as a xerographic drum,
rotating in the direction of arrow 78. A plurality of
scan lines 80 are formed on the surface of drum 76 in a
similar spatial relationship (the reproduction not being
accomplished in time synchronism since the output from
the photomultiplier tubes are initially directed to the
intermediate storage device 96 via a synchronizing buffer
98 in the preferred embodiment) with the information
being scanned on platen 62 to thereby reproduce a copy
of the image on drum 76 in a manner as described in the
aforementioned Patent No. 3,922,485. A start of scan
detector 82 is provided adjacent to mirror 72 to provide
-lOa-
lllSZ3~
a signal when the scan on dru~ 76 ta portian o~ the~
xerographic processo~ 77 shown in Figure 2) is initiated
and end of scan detector 84 is provided adjacent mirror
72 to pro~ide a signal when each scan lLne is completed.
It should be noted that although a single polygon scanner
is shown for ~oth input and output scanning, separate
polygon scanners which are synchronously driven may be
utilized, Reference may be made to the teachings of the
afor2mentioned U. S. Patent No. 4,Ql~2,~85 .
which pro~ides, inter alia, for scanning an unmodulated
laser beam at a reading station for reading a stationary
document the~eat and directing a ~odulated laQer beam to
an imaging s~ation for reproducing the document image
thereat and which utilizes single sc nner element.
, ., , . ~ .
Figuré 2 is an optically simplified version o~
Figure 1 and further shows, in a simplified form, the
electronic input scanning signal procsssing, storage
and output s~anning functions of the present invention.
The speod of drum 76 of xerographic processor
77 is assumed to be 12"/second or purpases o~ the calcu-
latio~s ~o foll~w but is not intended to limit the scope
of the present invention. The paper feed for both
simplex (printing on one side of the output paper) and
duplex operation (duplex operation, printing on both
sides of the output paper) is provided, for example, by
the Xerox 4000 copier manufactured by the Xerox Corporation,
is initiated on demand under control o~ the system micro-
processor controller 90. It should be noted tnat the
-11- j
1119Z39
function of microprocessor 90 is that of syste~ manage-
ment and when properly programmed, controls the operat~ng
se~uenc~ ~ of the entire system of the present
invention. It also sets up the appropriate operating
parameters derived from uqer controls on panel 92, such
as magnification ratio, de of operation, normal or
reverse scanning mode, etc. In general, the sy~tem
/11 controller issues appropriate ~ xerographic
- proce~sor 77, receives status signals ~herefrom, issueq
scan and storage control parameters and the start of scan
sisnals, receives status signals from the rest of the
system and, of course, interacts with the user panel 92.
Any properly ~rogrammed microprocessor, such as the Intel
80~0 or the Motorola 6800 or minicomputers such as the -
Xova series manufactured by the Data General Corporation,
Sou~boro, Massachusetts, can perform these functions.
Since the present invention is directed to the general
interrelationship of t~e system elements, a specific
description of the microprocessor system controller
90 and the operating software therefor i~ not set forth
herein.
It should be noted that the dimensions and the
calculations that follow are approximate and are set
forth for illustration purposes only and are not intended
to limit the scope of the present invention.
In one embodLment, input scanning is
provided on a flat platen 62 (14"x17" for exam~le), the
~can mirrors moving across the short tl4 inch) dimension
of the platen a~ shown in Figure 1 to provide for y sc~nins.
The X direction scanning in the long (17 inch)
-12-
~19Z39
dimension in the preferred embodiment, is produced by a
multifaceted rotating polygon 28 having 26 facets. The
actual total length of scan is 17.85 inches, which provides
0.43 inches over scan at each end of the 17" platen which
allows the scan clock generator 94 to be resynchronized
prior to the start of the next scan line.
Resolution in the X and Y directions of scan
is assumed to be equal. That is, the bits/inch (pixels/
inch) in the X direction equals the lines/inch in the Y
direction for both input and output scanning.
For a given output paper size, the output scan
density (this refers to resolution and not with optical
density) is constant, with reduction in image size being
accomplished by reducing the input scan density (resolution),
the number of pixels per output page being independent
of the reduction ratio selected. Reducing the input scan
density in the Y direction is accomplished by increasing
the Y scan mirror velocity by operator selection of a
desired magnification value (the range, for example, being
from 1.0 to 0.61) the input scan density in the X direction
being reduced by decreasing the number of bits/inch in
the X-scan direction by varying the scan clock generator
94 by the magnification ratio selected. This allows inde-
pendent control over the reduction/magnification in the
X and Y directions if desired and makes good use of the
capacity and bandwidth of the storage system 96, the storage system
preferably utilizing a magnetic disc 97. In this regard,
it should be noted that alternate image storage media (and
associated readout systems) can be utilized in the present
invention. For example, a video or optical disc system
for recording and reading out information (wherein lasers
may be utilized to record information on the disc and wherein
-13-
l~lS239
lasers are utilized to read the information formed on the
disc) have been disclosed in the prior art and may be
utilized in the present invention. A read-write optical
disc memory is disclosed, for example, in an article by
D. Chen, Applied Optics, October, 1972, Vol. 11, No. 10,
Pages 2133-2139, the teachings of which may be adapted
to the present invention. In general, the output from
the input scanning device can be utilized directly to
modulate a laser, via synchronizing buffer 98, the laser
in turn writing the appropriate information on the optical
disc. The information read from the optical disc can be
stored in synchronizing buffer 98, manipulated or otherwise
processed and then coupled to the printing portion of the
disclosed system. Other alternate image storage media
may utilize magnetic bubbles or CCD technologies, for example.
Images scanned and readout by photodetector 66
are stored in uncompressed, binary, digital format prefer-
ably on a dual platter, 4 track parallel, moving arm
magnetic disc system 96 via synchronizing buffer 98, the
-13a-
111~239
imately 8 x 108 bits which allows storage ~8,
8-1/2 x 11" impressions ~pages) scanned at approximately
423 lines/inch. The average data bit rate to the disc
system 96 (the system includ~ng a magnetic disc 97,
positioning arms disc drive etc.)is assumed to be
23.59 megabits/second.
Synchronization in the scanning system of the
pr~sent invention is deriv~d from the disc system itself.
A primary clock rate of approx~mately 28.62 megabits/
sec~nd is ~ormed ~y the timer block 100 in conjunction
with the disc and ~s used to control the recording of
information thereon f~om buf~er 98. This clock rate,
which will also be synchronous with data read from the
disc 97 (since the 3econd disc is identical to disc 97,
only disc 97 will be referred to hereinafter~ is counted
d~wn Ln timer (or clock) 100, to produce appropriate
2-phase AC signals to drive a synchronous scanner tor
0, the Y scan mirror dri~e motor 52 and appropriate
cloc~ signal from
clocX signals to synchronizing buf~er 98. ~he/scan clocX
~enerator 94 (used to control the timing of data that
modulates the laser ~eam on output scanning and to sample
tho photod~tector signals on input scanning) is generated
in burst~, under the control of the start-of-scan and end-
o~-scan photodetectors 82 and 84, respectively. The scan
clock generator 94 is therefor slaved to the speed o~
polygon 28 which in turn is derived 'rom the disc system
6 the scanning systam timing therefor being synchron-
nput scan
ized with the disc speed. The/speed relationships are
chosen to cause da'a to be generated at an average rate
e~ual to the ability o~ tne disc 97 to store it. Ir the
rotational speed of disc 97 was to change slightly, the
scanner 28 and scan clock 94 will follow the change.
-14-
lllgZ39
This synchronous system .imLng method al}ows the size
of the synchronizing buffes 98 to be significantly
reduced in size ~and cost) and substantially less than
the capacity of one helical turn on the disc 97 (as
will be set forth herelnafter, one turn of the disc g7
is capable of stosing 4 (surface~) x 48 ~sectors per
turn) x 4096 (bits per sector), which is 48 times less
than the size of the synchronizing buffer which preferably
will be utilized~. Synchronizing buffer 98 is required
~ince the peak data rate during input scan i~ approx-
imately 38 meg2bits/second, which is higher than the
rate that disc 97 can accept the input data (approximately
28 megabits/second). The average bit rates over a number
of scan lines, however, will be approximately e~ual.
Further, synchronizing buffer 98 smooths out any gaps
between sectors on disc 97, the sectors including 4096
data bits, when the reproduction system is in the print
de, the system controller 90 preventing gaps (and
sector headings, labels, etc.~ from being stored in the
synchronizing buffer auring the print de of operation.
The tLme to scan an original on the input platen
62 (see Figure l) i8 selected to be the same as the time
~e~uired to e-~pose the xerographic drum 76 in xerographic
procsssor 77 to reduce the time required for output and
the ~ize of synchronizing buffer 98.
The following relationships are given to
provide an indication of ~ystem performance. The follow-
ing definitions are useful.
ABR = Avera~e bit rate for magnetic disc 97 (bits/sec)
BPS = Bits per scan line
3PP = Bits (p~xels) per page
CPPs = ClocX pulses per sector for the masnet~c disc ~7
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1119239
DBC. = Disc data capacity in bits
DPC = Disc data capacity in pages
DR = Divide ratio for generating ~olygon drive fre~uency
Lp = Output paper length (in.) (Parallel to æ is of
xerographic drum 76.
Ls 2 Input platen scan length including overscan tin.)
(As~umed to be 17.885 in.~
M = Magnification ra~io (1.0 to 0.61)
= ~umber of facets on the polygon scanner 20 (a=sumed
to be 26)
SDi = ~nput scan de~sity (lines~in~h or ~its/incn)
SDo = Output scan density (lines/inch or bits/inch)
S~S - Scan lines per second
SPBRi = Peak input scan bit rate (bits/sec)
Vd = Xerographic drum surface velocity (in/sec) (assumed
to be 12 ips)
Vp = Polygon a~gular velocity (rpm)
Vy = scan ~elocity (in/sec)
Wp = Output paper width (in.)
.~herefore, from the ge~metries and character-
istics of the system, the following is obtained:
(a) Output scan density
SDo - rABR~ d~ ~))] 1/2
(b) Polygon rpm re~uired for output scan
~p , 60(SDo) (Vd)/N'
(c) Bits (pixels per output page)
BPP = (SDo) Wp) (SDo) (Lp)
(d) Input scan density
SDi - tSDo) (M) or ~'I ~ SD;
(e) Input Y scan velocity
Vy = Vd/M or M ~ V SDi being ~nvers~ly
prooo~tional to Vv
Z39
.
(f) Scanner rpm re~uired for input scan
~/11 vp =6o(sLs)/~=6o(sDi) (V~ N=60 (SDo) (Vd)/~
(g) Scan lines per second
SLS = ~(Vp)/60 = 5SDo~ (Vd). ..
(h) Peak input scan bit rate
SPBRi - (SLS) (Lg) (SDi) = (~) (L5~ (Vd) (SDo) 2-
(i) The total number of pages that may be stored on
the disc
DPC = DBC/BPP = DBC/~SDo)2(Wp) (Lp)
~he following summzrizes some of the system
characteristics for 8-1/2 x 11" o~tput paper.
TABLE I
Average bit rate (m~ps) 23.59
Output scan density (lpi) as determined
by the speed of drum 76 and the disc clock
rate 422.77
Output scanner velocity (rpm) 11,707
Bits/ll" line 4,650.47
Megabits/output page 16.71
Storage Capacity of Disc in pages 48.19
Peak input rate ~mbs) 38.30
If a maximum reduction factor o~ 0.61 is
assumed, the Lnput scan denqity in lines/inch znd bits/ .
inch is reduced from 422.77 to 257.89. The output copy
from xerographic processor 77 is still produced at the
max~mum scan density of 422.77 scan lines per inch.
The~total number of pixels per output page is constant
and independent of magni~ication and therefore allows
ror a simple and eff_ctive way o~ controll~ng masnifl-
cation ~y controlling input scan density.
-~7-
39
The inpu~ Y direction scan mirror veioci.y is
increased from 12 inches/second to 19.67 inches/second
for the 0.61 magni~ication ratio. The peak input bit
scan rate accordingly dxops ~rom 38.30 megabits/sec~nd
to 23.36 megabits/second.
When larger output paper is used, the scan line
density and disc page storage caDacity are reduced.
Table II lists system characteristics wherein 10.12" x
14.33" output paper is~used, Note that s~nce the bit
rate is fixed and the paper area is larger than Ln the
Table I example, the output scan density will be-less.
TABLE II
Average bit rate (mbps) 23.59
Output scan density (lpi)370.41
Output scznner velocity ~rpm)10,257
Bits/14.33" line 5,307.91
Magabits/output page 19.89
; Storage capacity in pages40.47
PeaX input rate (mbs) 2g~40
At a reduction ratio of 0.61, the input scan
density becomes 225.95 lines/inch with output s~anning
rema~ning at 370.41 scan lLnes per inch.
Although the in~ention deccsibed here~n is
preferably utilized to provide for electronic pre-
collation (precollation being provided in simplex oper-
ation ~y copying the number of lnput originals in
se~uence onto the disc 97 and printing a pre~etermined
number of copies of each seouence via the xerographic
processor 77), it should be obvious tkat by c~anging
control parameters and the sor~ware used by the micro-
processor 90 that many additionzl features may be
-18-
lll~Z39
provided i.e. providing a small alphanumeric_dLsplay for:
interactive guidance for the system user; a small portion
on the large disc capacity can be used to store statistics
on sys.em use; the disc could be used to store software
diagnostic routines to be used by the microprocessor
90 for trouble diagnosis; a scan density compatible
with easy conversion to facsimile could be selected,-etc.
The disc 97 to be utilized with the present
invention is assumed to comprisa two platters (four
surfaceq) recorded and read ~n parallel, one sur~ace 99
of which is illustrated in simplifie~ form in Fisure 3.
The data is recorded, for e~ample, in 1024 discontinuous
sectors 101 withLn angular area 102, 48 such angular areas,
being formed in band area 103 around~the disc circumfe~ence
~approximately 50,000 sector~ thereby being provided).
Each sec~or 101 is subdivided into 3 main sections. The
first section contains a space 104 for a fixed header
identifying the sector number. ~he second section 105
is a rewritable control area of 12~ useful bits identi-
fied a3 "label". The third section 107, separated from
section 104 by gap 111, is the normal data area of 4096
aata bits. There are 48 such sectors per tur~, each
sector being separated by gaps 113. Information is
preferably recorded in a spiral (helical) pattern
(similar to a phonogxaph record) with a total of 1024
active data turns. The spiral type pattern (trac~) allows
data to be read continuously with the disc read/wri.e heads
//G
11J following ~he trac~ as in a phonograph reco~d. The
header area 104 of each sector may be arran5ed to contain
a patter~ that is usad to servo con~rol the radial
position of the recording-playbac~ head to allow it to
follow the spiral data path,
~he number of circ~mferential cloc~ periods
-19-' ' I
1119239
(not shown in ~he figure) re~uired Ln eac~-sector fo~
gaps, header and label (error detection and correction
bits may be provided if desired) i9 assumed to be 872.
There~ore, the total sector length is 4968 clocX periods.
Table III summarizes typical performa~ce characteristics
for the disc syst~m 96:
~ABLE III
Data bits/sector (each surface) 4,096
Clock periods/sector 4,968
Data bits/sector (4 surfaces) . 16,384
Sectors/turn 48
- ~urns/surface 1,024
Data bits/turn (on each surace) 196,608
Data bits/turn t4 surfaces~ 786,432
Average data ~it rate/surface (mbs~ . 5.89
~30 x 48 x 4096) wherein the disc
rotation rate is 30 revolutions per
second
Average bit rate for 4 tracks (mbs) 23.59
` Peak bit rate/susface ~mbs) 7.15
(30 x 4~) (4096 + 872)
Total peak bit rate (mbs) .28.61
~otal data capacity ~bits) 80~,306,365
- Althcugh not considered part of the present
invention, it should be noted that the large size of
the data bloc~s in this system make the use of isolated
and burst error detecting and correcting codes e'ficient
and attxactive.
The seek operation wherein the radial disc
arns seek the starting sector on the disc 9~ is def~ned
by specifying a uni~ue sector number out of the total o~
-~0- ~
lll9Z39
49,152 sectors along the spiral track by the-~system_ :
controller 90 and hav~ng a controller speciCied accoler-
ation motion to enable the disc arms to locate the correct
sector. ~ew information (represent~ng ~ages in this system)
is written directly over old data without a separate erase
pas3 to save system time.
Figure 4 is a more detailed bloc~ diagræm of
the present invention. It should be noted that si$nals
to and from the m crocode programmed microprooe~sor system
controller ~0 are indicated in the figures by circles
adjacent to a label of a function entering or coming from
a partic~lar electronic subsystem block.
Direction control device 121 receives an input
(Y scan drive fre~uency) on lead 122 from reduction counter
130, the system controlle~ 90 ~ntroduc~ng the signal l'start
scan" on lead 124. The velocity and direction of the Y
scan motor 52 are set up by the sys~em controller 90. The
scan velocity ~Y scan drive fre~uency) is determi~ed by
the "magnification ratio" control parameter on lead 128
3~0cified by an operator via panel 92 (Figure 2) which is
used to determine the clock fre~uency division ratio in
the system timLng counter 129 (logically a set of counters,
the coun~ ratio being changed by the selected magnifi-
cation ratio)and the reduction counter 130~ The magnifi-
cation ratio signal i~ applied to reduction counter 130
via lead 127 a reduced clocX sisnal being applied there~o
from syste~ timLng counter 129 via lead 119. The directio~
control device 121 causes a Y scan pass to be
after the "start scan" signal and direction ~nfor~ation a-
~provided by the syst~m controller 90 the direction ln~ormation
being initially set up by an operator via panel 9~ . Logic
-21-
~g~39
circuits within direction control device I2I~~determ~ne
the proper polarity of the Y scan dri~e ~ pplied
to mctor 52 for the correct direction of scan. In the
, '
;: '
-21a-
lllgZ39
normal (non-inverted mode) it is assumed that the Y
direction of scan is in the +Y direction from an initial
position 61 (Figure 1) whereas in the inverted mode of
operation the Y direction of scan is in the -Y direction
from initial position 63.
The start of Y scan time is derived by the
system controller 90 from information it has about the
starting sector number for the next page of information
to be entered into the disc 96 during input scanning.
~he system controller 90 receives information about where
the disc 96 is as it rotates from the header and check
logic block 131 on output lead 132. The controller 90
checks the Y scan status from the diraction control block
on lead 126 prior toinitiating a start scan command to be
sure the scanner is in the correct home, or initial
position. The correct home position obviously is depen-
dent upon whether scanning is to proceed in the normal
or reversed modes of operation.
It should be obser~ed that since the input ~ 20 scan line density must be changed Ireduced) to vary the
magnificat or. ratio it is preferable to change the size
of the scan spot for lnput scanning, ~n order that the
scanning spot cover the entire area of the document
thereby maintaining the optimum ratio of scanning aperture
size to scan line density. To incrase the Y dimension
of the scan spot optically (anamorphically), optical
aperture control 133 is utilized during input scanning,
the aperture control incrasing the size of the scanning
spot in the direction associated therewith via a signal
from system controller 90 on lead 135. On input scan-
ning, the effecti~e X dimension of the spot (in the
direction of high speed scan) may be controlled by
-22-
lllSZ39
changing the electronic bandwidth of the aperture control
134 following the photodetector 64 via a signal from system
controller 90 on lead 135. During output scanning, the
effective size of the spot in the X direction (which is
maintained essentially constant since the output scan line
density is maintained constant) is controlled by the timing
of signals supplied to the acousto-optic modulator 32 via
lead 125 under control of the scan clock generator 94.
As set forth hereinabove with reference to
Figure 1, a blue and red laser 10 and 12 are assumed for
input scanning to avoid color blindness which would occur
if monochromatic illumination were used. In the system
shown, both lasers are used for input scanning, and the
blue laser is used for output scanning.
Although it would be cost effective to use a
single polygon X scanner 20 for both input and output
scanning, it may be preferable to use a second polygon
which uitilize a separate 2-phase synchronous drive motor.
In the single scanner design, one pair of scan
synchronizing detectors will normally suffice i. e. end-
of-scan detector 84 and start-of-scan detector 82.
Signals from these two devices allow the generation of
precisely controlled streams of "bit clocks" for sampling
the signal from photodetector 66 on input scanning or
controlling the timing of image data fed to the laser
modulator 32 on output scanning. It should be noted that
the system mode of operation (whether input scanning or
output printing) is determined by the operator via panel
92. The scan clock frequency is controlled by phase
detector 136, start-stop control device 137, voltage con-
trolled oscillator 138, linearizer 140, and bits~inch
counter 142.
-~rl -23-
239
The voltage controlled oscillator 138, oscillating
at a present frequency, does not operate continuously, but
is released to start oscillating on each scan by the start
of scan pulse and is stopped at the end of scan via start/
stop control 137. The phase comparison in phase detector
136 is also initiated when the start of scan pulse is
received via lead 141. The count down ratio of the bits~
inch counter 142 is set by the system controller 90 accord-
ing to the operator selected magnification ratio and output
paper size utilized. The preferred range is from approxi-
mately 423 bits/inch to approximately 226 bit/inch (input
scan onto 14.33 paper at magnification of 0.61). When the -
preset number of bits (voltage cycles) (bitslinch times
the input scan length including overscan) from oscillator
138 have been counted in the bits/inch counter 142, a
pulse is coupled to the phase detector 134 via lead 144.
If the avexage signal frequency from oscillator 138 is
correct, a pulse will be received from the end of scan
detector 84 at the same time. If, for example, the poly-
;~ 20 gon 28 had speeded up slightly, the end of scan pulse
will arrive at the phase detector before the bitslinch
counter pulse on lead 144. This will cause the phase
detector 136 to generate a voltage error signal to
increase the frequency of oscillator 138. Note that
there are 26 such samples of scanner rotation rate for
each rotation of the scanner 28 since it has been
assumed that scanner comprises 26 facets.
The bits/line counter 146, synchronized by os-
cillator 138 via lead 145, counts down from a preset count
which corresponds to the various sizes of output paper
to which the developed image formed in the xerographic
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, .
,,, . I
lil9239
processor 76 is transferred by standard techniqu~s in
the preset ~ode. ~he range (count) is 4656 to 5312
bits/line which is less than the range for counter 142
since the latter count is preset on the basis of the
input platen scan line length and including overscan.
These numbers are slightly larger than those listed
-24a-
1119Z39
in Tables I and II in order to be compatible with the
operation of the synchronizing buffer 98, the number of bits/
line being rounded upward to the nearest multiple of 16.
The linearizer 140 generates a second input to
oscillator 138 via lead 147 to correct for non-uniform
velocity of the scan spot, the bits/line counter 146 providing
a signal to linearizer 140 via lead 149 to provide an indi-
cation where in the scan line the spot is located at any
instant. It has been observed that the instantaneous scan
velocity normally is higher at the edges of a scan that at
the center of the scan. ~ven though the input and output
scan nonlinearities might compensate each other, electronic
linearity correction of the image data stored in the disc
by scan clock variation may be preferable to allow later
coupling between machines with different scan geometries.
The scan clock gate 148 releases precisely timed
bursts of clock pulses on lead 200 at the start of its
countdown cycle ranging in frequency from 38.30 to 17.93
megabits/second as determined by the system controller 90
;~ 20 (output paper size and magnification ratio). The number of
pulses in the clock burst is determined by the countdown
ratio set in counter 146. The scan clock gate 148 is used
to control the timing of loading the synchronlzing buffer
assembly 98 with signals from the photodetector 66 in the
input scanning mode, the unloading-of the synchronizing
buffer 98 to the disc system 96 for input scanning being
under the control of the disc clock, to be described here-
inafter.
The threshold detector 150, with its input
control parameter on lead 151 is used in simple signal
processing operations to produce, in effect, extremely high
gamma. A threshold slicing level may be modified under
-25/25a-
~T
lll~Z3g
user control to help remove bac~ground and otherwise clean
up inferior originals. Existance of the image information
in electronic form makes possible a wide range of image
enhancement techniques.
The timing of the entire scanning system is slaved
to the disc clock. On input scanning, signals from the
photodetector 66 will come in bursts since (for 11" paper)
the active scan time is only llJ17.855 of the total scan
line period for the case of no reduction. This produces a
peak input scan bit rate (SPBRi) of 38.30 megabits/second.Similarly, the disc input and output data flows in bursts
to compensate for the overhead necessary for sector gaps,
headers and labels. The peak disc data rate is 28.62 mega-
bits/second. Therefore, total peak instantaneous bit rate
for the synchronizing buffer is 38.30 plus 28.62 megabits
second. The average input rate is equal to the average
output rate for most modes of operation and is equal to
23.59 megabits~second. An exception occurs when the
reduced image of the 14" x 17" input platen is smaller
than the output paper size, as determined by the operator
selected magnification ratio and paper size. In that
case, "white border bits" are generated to ~ill the out-
put page as is described hereinafter.
Figure 5 shows some of the functional blocks
enclosed in the dotted outline corresponding to the
synchronizing buffer 98 of the block diagram of Figure 4.
The buffer storage 170 required to accommodate the
bursts of data is assumed to be made up of 16, lK random
' access memory (RA~) chips. Each input and each output
0 operation of the RAM handles 16 bits inparallel. It is
-~6-
l~lg239
assumed that chips operating at 200 nanoseconds fullcycle time will be utilized. This will provide a peak
rate of 80 megabits. Serial to parallel shift register
172 and parallel to serial shift register 174 make the
necessary conversions at input and output, respectively
for the random access memory 170.
For the non-inverted first-in, first-out oper-
ation mode of operation, a load address counter 180 sel-
ected by address selection gates 181, sequences through
the 1024 addresses in RAM 170, sequentially and circular-
ly to load data therein from the threshold detector 150
in the input scanning mode of operation. Similarly, an
unload address counter 182 provides sequential unload
addresses for the RAM 170 under control of address
selection gates 181 when data is to be unloaded to the
disc 97.
The data selection gates 186 contain parallell
digital gates that switch the input and output bit streams
to and from the synchronizing buffer 98. For input scan-
ning, the peak input scan bit rate clock on lead 20
controls the input shift register 172 via the shift
register clocks on lead 206 and load address counter 180
timing via the load/unload clocks on lead 204. The
peak bit rate disc clock on lead 201 controls output
shift register 176 via lead 206 and unload address
counter 182 timing via lead 204. The threshold detec-
tor 150 IFigure 3) is the input data source to the data
selection gates 186 via input shift register 172 and
holding register 173, the output image data ~rom RAM 170
going to disc 97. Similarly, for output scanning (print-
ing) the disc clock on lead 201 controls the input to RAM 170
via shi~t register 172 and load timing via load address
-27-
~1~9239
counter 180 while the scan clock on lead 200 controls the
output of RAM 170 via output shift register 174 and the
unloading address counter timing via counter 182.
When a bound volume is placed on the input platen
62, successive pages of the volume may be placed upside down
on the platen to make use of the book edge feature incor-
porated in copiers commercially available. In order to
reverse the image so that all pages will be right side up
when the output is generated, the X and Y scan directions
both must be reversed Iscan inversion is accomplished by
operator selection of a "Scan Invert" button (not shown)
on panel 92. Note that if only the Y scan direction were
reversed a mirror image of the document scanned would be
reproduced). Although the Y scan direction can be changed
by appropriate control of the Y scan direction control
device 121 thereby resetting the initial start position
and direction of scan mechanically changing the X scan-
ning direction is not feasible due to the inertia and
high operating speeds of the scanner 28. The X-scan
direction is therefor reversed electronically as ~ollows:
For an 8-1/2 x 11" input document, it is assumed that
approximately 291 sixteen bit words comprise one scan
line in the 11 inch X-scan direction. During the input
scan (the system is assumed to be in the inverted input
scanning made) load address counter 180 via address
selection gates 181 causes the input scan info~mation
from photodetector 66 (291) sixteen bit words) to be
stored in sequence, for example in storage locations
O to 290 in RAM 170, at least one complete scan line
being stored therein. Lead 230 is appropriately
energized to allow storage to be accomplished when the
store mode of operation is selected. Preset address
-28-
~:1
~ .,
111~239
counter 179 is caused to be set to a first preset address
290 in the inverted mode of operation, a signal on lead
177 causing the unload address counter 182 via address
selection gates 181 to count down sequentially from
storage location 290 (i.e. 289, 288, ... ) such that the
scan line information is read out word by word in the
reverse order in which it was stored, an appropriate
control signal being applied to lead 230 to enable RAM
170 to be read out. The information read out is coupled
to output shift register 174 via lead 175, data selection
gates 186, and output holding register 183 and thereafter
to disc 97. As shown in Figure 6, output shift register
174 is coupled to the 16-bit output holding register 183
and comprises four shift registers 240, 242, and 246.
When information is to be recorded on discs 97 and appro-
priate control signal from system controller 90 is
applied to register 174 on lead 250 to enable the infor-
mation to be read out in four-bit blocks to be applied to
the disc write block 222 and thereafter to be applied to
the 4 recording surfaces of the discs 97 via write ampli-
fiers 223 ~Fig. 4). When the information read out from
RAM 170 is to be applied to modulator 32 and thereafter
reproduced by xerographic processor 76, the signal on
lead 250 enables the inormation to be read out serially
on lead 125. In a similar manner although not shown in
the figure input shift register 172 is adapted (via a
signal from system controller 90 on lead 251) in the
input scan mode, to convert the input serial data stream
into 16-bit parallel format and to convert the four bit
word from the discs 97 via amplifiers 225 and data
recovery circuits 220 into 16-bit parallel words in the
print (write) mode.
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~, .,
1119239
The next scan line is recorded in locations 291
through 580 in RAM 170 and the preset address counter 179
is set to address 580, the data in these addresses being
read out in a manner as described hereinabove with refer-
ence to locations 0 through 290.
In the inverted mode of operation, the bits inoutput shift register 174 are shifted from left to right
and read out on lines 239, 241, 243 and 245 whereby each
bit in the scan line is transposed for reverse scanning.
In the normal (non-inverted) mode of operation, the bits
in each scan line are shifted right to left and read out
on lines 237, 247, 249 and 253 with no transposition of
the bits comprising the scan line occurring. In other
words, shift register 174 is bidirectional, data bits
being shifted out right-to-left in the inverted mode of
operation whereas the data bits are shifted left to right
in the normal FIFO (first in, first out) mode of buffer
operation. It should be noted that input shift register
172 need not be bidirectional since, in the print mode
of operation, the transposed bits stored on the discs 97
will be in the correct sequence when read out.
When the system ls in the print mode, as deter-
mined by operator energLzation of a "PRINT" button on
panel 92 (not shown), the output from discs 97 is read
out via read pre-amplifiers 225 and initially stored in
memory 170 in the address specified by load address counter
180, counter 180 being selected by address selection
gates 181 to store information in RAM 170. To unload
data to the modulator 32, unload address counter 182 is
selected by gates 181 and caused to transfer the informa-
tion in RAM 170 via data selection gates 186 and output
holding register 183 to output shift register 174. It
-30-
X
: .
1~19239
should be noted, as set forth hereinabove, that since the
scan lines have already been reversed prior to being stored
on disc 97, unload address counter 182 is not caused to
count down by a signal from buffer control 202 on lead 177.
The data which is being read out therefor is electronically
reversed in the x-scan direction.
The scan clock on lead 200 is utilized to control
the timing of loading the RAM 170 with signals from the
photodetector 66 on input scanning, the unloading of the
RAM 170 being controlled by the clock signal derived from
the disc system 96 on lead 201. For output scanning, the
loading of the RAM 170 is controlled by the clock signal
from disc system 96 whereas the unloading of the RAM 170
is controlled by the scan clock signal on lead 200. The
load and unload address clocks are applied to lead 204
and shift register clocks are applied to lead 206 via
synchronizing buffer control 202.
The header and check logic 131 (Figure 4) is
connected to the shift registers 172, 174 via leads 227
and 228 to enable the acquisition and loading of header
and control information from the data stored ln the shi~t
registers. The system controller 90 will supply header
and check logic 131 with the following parameters: Lines~
page, bitslline, and page start sector number which in
turn modifies the data stored in the RAM 170 with this
information priox to loading the discs 97. Since four
surfaces of the disc are used in parallel, the basic
disc data block is 4 x 4096 = 16,384 data bits which cor-
responds to the timing of one disc sector. Since the
largest number of bits in a scan line may be greater than
4096 data bits, the start of successive scan lines may not
occur at sector boundaries. It is assumed that the first
-31-
lil9239
scan line of each page may start at a sector boundary
identified by the page start sector number.
The label information associated with each sector
may identify the number of lines remaining in the current
page and the location of the boundaries between successive
scan lines for each sector. This information can be
thought of as completely defining the format and other rele-
vant information about the data to follow.
The header and check logic block 131 will check
sector identification and will preferably also verify data
integrity by generating and comparing error detection and
correction redundancy patterns by standard computer tech-
niques although this does not form part of the present
invention. Sector number checking is aided by the avail-
ability of the current sector position of the disc derived
from the system timing counter 129 of Figure 4 which supplies
sector pulses ~approximately 48,000 pulses per disc revolution)
to sector counter 240 via lead 241 (approximately 50,000
total for 1024 turns). As shown, pulses from timing
counter 129 are also applied to buffer control 202 (approxi-
mately 28.2 megabits/sec) and header ~nd disc loglc 131 (one
index pulse per disc revolution) via leads 201 and 242,
respectively. The clock for disc data recovery circuit 220
is derived from the recorded data during a read operation,
the clock for the disc write logic circuits 222 being
derived from the system timing counter 129 during record-
ing. Each of the four independent data recovery circuits
220 will generate its independent read timing clock although
the disc system timing clock controls the combined output
data stream as it is passed to the main synchronizing
buffer 98.
-32-
~1
~ . ...
111~239
number commands to the seek control block 206 via lead 224
that controls the positioner Inot shown) for disc arms 115.
Seek complete status is indicated to the system controller
90 via lead 207 when the commanded sector has been acquixed
by the seek control 206. The system controller 90 can then
issue the start scan signal to the seek controller 206 to
allow the disc heads to follow the spiral track either for
recording or playback of the disc data.
The position detector 210 generates radial head
position error signals (i.e. radial deviation from the
helical track) from the playback voltage on lead 211 which
may be generated by the position control pattern permanent-
ly recorded in the fixed header segment of each sector.
Timing for this operation is derived from the system timing
15 counter 129 via lead 228.
The gear clock PLL 212 is a phase locked loop
frequency multiplier used to generate the 28.62 megabit/
second basic system timing signal. The input for this
block is derived from a multi-toothed gear mounted to
the disc drive hub, (a plurality of teeth corresponding
to each of the 48 sectors per t~lrn~ a magnetic detector
pickup mounted on the disc suppc t structure generating
a pulse as each tooth rotates therepast, a pulse stream
thereby being generated having a frequency proportionai
to the rotational speed of disc 96. A typical input to
gear clock phase locked loop 212 is 192 pulses~sacond.
In order to provide the required maximum system pulse
rate of 28.62 mbs, gear clock 212 multiplies the input
pulse rate by a factor of approximately 5500. The
-33-
. ,
l~lg239
detector is separated from the recording discs 97 and
is always available whether the disc system 96 is
reading or writing. It is to be noted that system
timing counter 124 supplies a plurality of pulse signals,
includLng pulse rates reduced in frequency from the
28.62 mbs input on its output counter leads to provide
appropriate timlng signals to ~he ~arious system elemen~s.
For exzmple, a frequency of 100 cycles is generally
re~uired to drive motors 40 and 152. The count ratio o~
counter 129 is varied by the magnification ratio on
lead 128.
Three basic modes of opera~ion are involved
in the operation o~ the present system. The ~ixst is a
preparatory one noted as job set up, the second is input
scanning where originals are scanned and written on the
disc, the third is output scanning where copies are
produced xerographically.
-33a-
lllg239
During the job set up, the system controller
90 fu~ni~hes a starting sector number for the first page.
The disc seek control 206 will find that sector issued
by header and chec~ logic 131, and then set up ~he idle
mode holding pattern and ~ndicate a seeX complete
condition to the system controller 90 on lead 207.
S~milarly, the proper timing ratio~ will have been
issued to cause the sca~ner 28 rpm to be selected and
stabilized. The scan clocX phase loc~ed loop will be
generating the correct number o~ bits/inch and bits/scan
line for the selected magni~ication ratio and output
page size, the proper scan clock there~y being applied to
lead 200. The header control logic 131 wi}l have been
set up with the bits/scan line and scan lines/page para-
meters. The controller 90 will generate the sector
number to start each page, and these will be pro~ided
se~uentially to the seek control 206 as the job progres-
ses in order to allow for electronic precollation.
The controller 90 has been gi~en the number of pages/
~ook and the number of booXs ~copies)/job by the user
through the control panel 92.
The controller 90 ma~ derive or be told by the
opexator of the sLmplex/duplex status of each output
page and computes appropriate page start sector numbers
to provide the optimum sequence for duplex output
production (if the ~erographic ~rocessor 77 is capa~le
of duplex operation)~
After the job is sat up, the input scanning
operation can p~oceed. The operato- places his ~irst
original on the platen and pushes either the `'~or~al"
or "Invert" scan button on panel 92. ~his causes the
syste~ controller 90 to initiate a scan on either the
Y or-Y direction (Figure 1) at an initial start~ng
-34-
lii9239
pcsition. The Y scan motor 52 will starL wi~h a lead
time (with respect to the arrîval of the page st?rt
sector number of the disc) to allow the Y scan mirror
to accelerate and stabilize at the selected velocity
~as determined by the selected reduction rati~) and
depending on normal or reverse scan direction, both
parameters be~ng operator initiated. As was mentioned
hereinabove for reverse scanning, one or more complete
scan lines must be loaded into the synchronizing bu~fer
98 prior to the arrival of the page start sector at
read heads of the disc. At this time, the disc ~ystem 96
will demand output from the buf~er 98 in inverted (or ~IFO)
mode. The data ~low into the buffer 98 from the photo-
~etector 6~' is timed according to the scan clock synchron-
ization circuits and is not determined by the position of
the Y scan drive motor 52. Variations Ln the position
of the Y scan mirror at the start of electrical scan
are e~uivalent to a shift ~ t~e position of the original
on the platen t~n the Y direction) and do not affect
the synchroniz~ng buffer. A position detector can be
provided to chec~ the timing o this operation to allow
the system controller 90 to adju~t the lead time
paræmeter.
The system runs to the end of the page and the
disc system 96 see~s the next page start sector number.
If the input scanning is being done for simplex output
printing, the next page will start at the next sector
following ~he last sector used in the previous page.
For duplex output, appropriate page start position
interlace will have ~een generated by the system
-35-
I
~1~9~39
controller 90. That is, the sequence of pases alo~g the
~piral track on disc 96 will be arranged during input
~canning ~or the benefit of high thruput output.
Operation during the third mode, output
scanning, is similar. In the idle condition, the disc
system 96 ac~uires the page start sector. The paper
feed from either the duplex recirculation paper path
or the normal paper supply path from xerographic processor
77 can be triggered on demand from the system controller
90. Collation is then done electronically as each page
is read from the disc in se~uence to fon~ a bo~k, the
number of bco~s ~hat will be generated being dependent
on operator selection of the appropriate buttons on
panel 92.
Interlea~ed input and output may be requ~red
for example, when a job requiring 2S copies o~ a 13-page
original has been loaded and the system is Ln the output
(print) de. The operator then wishes to load a new
~0~. Thi8 fact, plus th~ other normal jo~ set up
~uantit~es are entered via the control Xeyboard 92 and
the first original of the new job is placod on the platen
62. When the start button is pushed, the system controller
90 f~nishes printing the output page in proces~ and then
mcment rily interrupts the output printing operation.
The system controller 90 res~ts the scan clock rate
and an input scan takes place. The system then immedi-
ately resumes output printing while the operator changes
to the next original on the input plat~n, the process
being repeated until the first job is com?leted and 211
the originals of the new job have been scanned.
The following sets forth an analysis of some of
the factors that may be utilized to determine the size
of synchronizing buffer 170 and the system timinq
-36-
~ . . .
111~239
relationships and considers the case of-~np~ scan~ing,
using 8-1/2 x 11" output paper size and the normal
(no reduction) mode. This appears to place the most
stringent demands on the size of buffer 170. Table rv
hereinbelow lists some data, (times being in micro
seconds and bit rates in megabits/second)for the system
described hereinabove.
TABLE rv
Total sector time 106/30 x 48 694.44
Active sector time 16,384/28.61 572.55
Inter sector time (assumed gap time) 121.89
Total sc~n line tim~ 60 x 106/~)(Vp 197.11
Active scan line time 4656/38.3O 121.5a
Inactive scan line time 75.53
Total bits/scan line 46~6
Total bits/sector 16,3~4S
~umber of scan lin~s/sector '3.51
PeaX bit rate to disc 28.62
Peak bit rate from scanner 38.30
The most stringent demands made on sy~chronizing buffer
. .
is in the inverted page mode wh~re at least one complete
scan l~ne muct be loaded into the buffer memory 170
prior to removal o~ inform~tion for the disc 96. The
minimu~ lead time for informatian supplied to the ~uf~er
memory ~rom the input s~anner that is re~uired to prevent
the disc unload requirements from overtaking the data
available ~n the buffer should be dete~mined.
Time will be measured, ~n the follow~ng calcu-
lation, with respect to the instant,time to,tnat data
~its must be su~plied to the 96 disc from the bu~rer
170. The time to load the 4656 ~its of the first scan
line Lnto the aisc 96 is
4656/~8.62 - 162~71 microseconds.
The disc therefor accepts a line of data Ln less than
the 197.11 microseconds total scan line time. Therefore,
-37- ~
when disc 76 is ready to receive the beg~nn~hg of the
fourth scan line near the and of the first disc sector
which will occur at
t4 = 3 x 162.71 = 488.12 microseconds
after to~ the lnput scanner at t4 ~ust have loaded
four complete scan lLnes into the buffer 170. The
time re~uired to load n scan lines Lnto the buffer is
given by ..
n (197.11) -75.53
If T~ denotes the lead time in microseconds with respect
to the start of the data blocX ~to)~
4 (197.11) - 75.53 -T = 488.12,
Tl, = 224~79.
~ . . . , ... .~ ?
.
t '694 ~ --- 694
, 573 .
.. Disc ti~ng -- 1 Z , 3 4 ¦ x ! 4 ~5 , 6 ~ 7 ~, x
~ 225 .J 488 . .: .
~ 2 X 1 3 , X L 4 _ X, 5 ~ X, 6 , X ~ 7 ~ X, 8 ~ X
1, ~, 3 ... represent scan line numbers (both disc and
scan~ ,
x represents inactive time
Thus, TL re~rssents the latest start time at which
input scan ~ig~als may start to enter the sync~ronizing
buffer 170 measured with respect to time to, the initi-
ation of the unload to fhe disc, the unload initiation
process being controlled by bu~fér control 202.
The earliest start time is determined by the
-38- ,
239
upper limit on the size of buffer 170. Aft~r feedLng
three scan lines into the buffer without removing any
informatlon for the disc 96 there will be
(16,384 - 3 x ~656) = 2416
bit positions left in the buffer ~70. The start of
transfer to the disc 96 from the buffer (to) will
oc~ur at some time during the loading of the fourth scan
lLne into th~ buffer 170. Prior to to~ the net Lnput
rate to ~he buffer 170 will be 38.30 megabits/second
input. The diferential input rate after to will be
38.306 -28.62 = 9.68 megabits/second~
. . ., ~ ... _ . ...
.
. ~ . , - ,
Disc ~ 163 ,
ti~ir.g 1 2 3 ~ 4
. . . ~ ~ .' . ' '.
--I 43 ~ 78 1 ~ 121,6 ~ .
3 ~ X ~ 1 4 I x ~ 6 J x -I
tl to, t2- ' ' ' '',, " '. '-' . ....... . '
~, input scan ~:isnir.g
,: .' , :.
The active time for scanning the fourth scan line (121.58
microseconds) can be devided into two intervals, tl ~ t2
tl + t2 = 121.58.
The total net inorease in bits contained in the buffer
170 during the input of the fourt~ scan line cannot
exceed the rema~nins capacity of tke buffer 170 (2~15
bits). Thererore,
tl x 38.30 ~ t2 x 9.68 = 2416.
tl = 43.30 microseconds.
-39-
lllg;~39
The earliest lead time that the~scannlng input
can start is, there~ore,
TE = 3 x 197.11 ~ 43.30 = 634.63 microseconds.
The optimum lead time with respect to to
normally would be considered to be the average of the
e2rliest and latest lead times, i.e. 430 microseconds.
Rowever, the ~can lLne start times precess with respect
to the disc sector start times. The opti~um ena~le
~ime for a}lowing the input scanner to start loading
will leave the buffer 170 equal margins before the
earliest allowed time and after the late~t pos~ible
occurri~g time (after enable). These possible data
load start times are separated by one total scan time
or 197.11 microseconds. Thus, if m - margin time,
2m 1 197.11 - 643.63 - 224.79. -
m = 110.87
Therefore, ~or the case of 8-1/2 x 11"
output paper size inverted scanning, no reduction,
the optimum time to initiate input scan loadLng o~
the synchroniz~ng buffer 170 is
TE -m - 532.77 micro~econds
bofore to~
:', - ` ` ' ' : '
644, - _
- 533
111 ~ 7 ~ . 225
maYgin scan start ¦ ~argln
t ~t~val ~
~F , sc,~n star. enable T~ ~
-40- j .
- 1119Z39
An example o~ how the normal ~rst-in fi~9~-
out operation might function during non-synchronous
interlaced load and unload cycles is set forth herein-
after. Assume again the 8-1/2 x 11" output paper, no
reduction, input scan case. l~-~it words will be
available Ln the input data holding register }73
(Figure S) a~ intervals of
16/3a.3 = 0.4178 microseconds.
Thi~ information must be loaded into the ~M 170 at
somo time before the next 16-bit data word is assembled
in the input shift register, i.e. before 417.8 nano-
seconds have elapsed.
5imilarly, the output shift register 174
,
-40~- 1
~Z39
will require a new 16-bit word from its output holding
register 183 at intervals of
16/28.62 = 0.55905 microseconds.
If there is a coincidence in the time at which
an input word is ready and an output word can be accepted,
input is given priority, since inputs come faster, when
simultaneous requests for RAM operation occur. Table III
illustrates (in simplified terms neglecting logic delays
of a few nanoseconds~ a possible sequence of events. For
this example, it is assumed that an internal sync buffer
logic clock on lead 201 running at 57.24 mega pulses/sec
instead of the 28.62 megabits per second set forth herein-
after is made available by the gear clock phase locked
loop 212.
Therefore, internal events can be initiated
only at the times of occurrence of these clock pulses or
about every 17.47 nanoseconds. Each RAM memory cycle
(either store (load) or read (unload) is assumed to take
200 ns. Assume that the memory cannot be recycled until
at least the second clock pulse occurs following the
completion of any memory ~ycle or after any new non-
synchronous memory cycle request is generated. The
times listed for completion of memory cycles, and also
for the availability o~ input words, are not synchronous
with the internal buffer clock and are designated as
"NS" in the table. In this arrangement, RAM output
requests will occur synchronously at inter~als of 32
internal clock periods.
For purposes of identification, the input
words being loaded are designated as 101, 102, etc.,
while the words being unloaded are 1, 2, 3 etc.
-41-
239
TABLE III
RAM (FIF0) Ti~ng Example
I~t~al
Cloc~c
Puls~ Time ~oldlng Register S
~u~er_ nsec ~ OPeration ~n~ut Out~u~
O O reqyssc. 101 ready 1 ready
17.5 start load 101
IJS 217.5 end load 101 emDty
13 227.1 re~ync.
14 244.6 ~tart unload 1
~S 417.8 102ready
WS 4~4 . 6 end u~load 1 . empty
454.2 re~y~c.
27 471.7 sta~t load 102
32 559.0 2 Eesdy
~S 671.7 end lc~ad 102 empty
39 681.3 re~ync.
69~3.8 start unloaa 2
~S 835 .6 103ready
E~S 8g8.8 end us~load 2 . ~npty
52 908.4 resync.
53 925.9 ~tart lcad 103
64 111~.1 3 r-ady
~5 1125 . 9 end load 103 empty
1135 . 6 resync.
66 1153 . O start u~load 3
l!~S 1253.4 104ready
~S -L3S3 . O OEld ~load 3 empty
78 1362.7 ~esync~
79 1380.1 start load 104
~S 15aO.l end load loa empty e.~np~y
***~o acti~rity - waitlng ~or r~uest***
~S 1671. 2 105 ready
-42-
~:39
96 1677.1 resync. ~~ ~ ~ 4 ready
97 1694.6 start load 105
NS 1894.6 end load 105 empty
109 1094.2 resync.
110 1921.7 start unload 4
NS - 2089.0 106 re~dy
The poin~ to notice is that the FIF0
se~uence catches up with the combined input and output
tasks at 1580.1 nsec after the start of the example.
It waits for the generation of a n~w request which
comes at 1671.2 n~ec when a nonsynchxonous load
re~uest is generated, and the pattern starts to repeat.
An input scan tIming prob}em occurs when
the reduction ratio causes the reduced Lmage of the
input to be smaller than the output paper size. The
size of the original (s) on the platen 62 is of no
concern if the cover is closed. The viaeo signal
variation due to the difference Ln re~lectivity of
; the platen cover and the unmarked areas of the paper
can be set below the slicing level of the threshold
detector 150 and should not ~e noticable.
Figure 7(a) i9 a representation of a
reduced image 270 formed on output paper 272 (this
can also c~rrespond, for example, to the electrostatic
dot pattern formed on drum 76 within the xerographic
processor 7~ A-~ can be seen, in order to center the
image 270 on output paper 272, the left hand and right
hand borders tas viewed from the paper) 274 and 276,
respecti~ely, ~nd ~he upper and lower borders 278 and
280, respectively, must be appropriately generated to
center tne Lmage 270.
Figure 7 (b) s'no~s apparatus ~hich may
.
'~
be utilized to center the image 270 shown in Figure 7 (a).
The system controller 90 via leads 280 and 282, loads regis-
ters 284 and 286, respectively, wit~ appropriate data
(dependent on magnification ratio and output paper size~
relating to the borders 274, 276, 278 and 280. For the X
input scan direction, a problem arises if 17M<Lp. For 11"
paper, this is M~ 0.65 (M~ o.84 for 14.33 paper). In these
cases, there would be fewer input bits available than is
required for one output scan line (SDo) (Lp), the input
scan bit rate being less than the average disc bit rate.
Register 284 is therefor loaded with appropriate
data corresponding to borders 278 and 280, the output of
register 284 being compared in comparator 290 with infor-
mation regarding the X position of scan from bits per line
counter 146. Register 286 is similarly }oaded by
microprosessor 90 via lead 282 and is compared with the Y
position of scan from Y scan position counter 294 (i.e.
compares the scan position with the known border conditions).
~ When 17 (M) C Lp (determined by system controller 90), the
;~ 20 necessary "white margin zeros" are split equally between
the beginning and end of each scan line, the output on
line 126 being correspondingly controlled. Referring to
Figure 4A, the output on lead 126 is coupled to a logic
device 300 which comprises AND gates 301 and 303. The
output on lead 126 is coupled to one input of AND gate
301 and to an inverting input of AND gate 303. The
output from data selection gates 186 is applied to the
other input of AND gate 301 whereas a voltage Vc is
applied to the other input of AND gate 303. When lead
126 is low AND gate is enabled and passes the voltage Vc
-44-
~,'1
~9Z39
to the modulator 32 to cause the laser 10 to generate the
necessary white margins Ithe beam from laser 10 discharges
the appropriate margin areas of drum 96). If lead 126 is
high, gate 303 is disabled, gate 301 is enabled and the
data signals on lead 125 passes to modulator 32 to modulate
the laser light from laser 10 to reproduce colla~ed pages
in xerographic processor 77.
Although not shown in the figures, the Y scan
position counter 294 is adapted to cooperate with the
shaft of motor 52 in a known manner to provide signals
representing the Y position of the scan line.
Similarly, for 14(M)~ Wp, the width of the
platen, as reduced, is less than the output paper width,
when M ~0.61 for 11" paper (or M~ Q.72 for 14.33 paper).
For this situation register 286 is appropriately loaded
with data corresponding to borders 274 and 276, a string
of completely blank scan lines being generated both
before and after the Y scan starts and finishes producing
valid data within the width of the image on drum 76.
These procedures will center the reduced
image of the platen area on the output page. The sur-
rounding white borders will be electronically generated
by causing the laser to perform the function of an
adjustable fade out lamp.
It should be noted that the drive frequency
for the 2 pole polygon motor 40 is Vp¦60 Hz. In
order to generate a 2-phase quadrature motor drive
signal, a quadruple frequency clock rate is required.
The correct value will cause scan bits to be generated
at the average data rate of the disc. Then
-45-
'J'~
_ . .
`
~ 3~ 7 (BPS) (~) (V~/60 = ABR.
Wherein BPS is the bits per soan line rounded upwards.
The peak bit rate of the disc g6 is related to the
average bit rate by the ratio of the number of clock
pulses/sector, CPPS, to the data bit times per sector
or CPPS/4096. The polygon drive frequency divide ratio,
DR, is selected such that
~(CPPS) tABR)/4096)]/DR = 4 (V~/60 - 4 ~ABR)/(BSL)(~
DR = (CPPS) (~SL~ (~)/16,384.
with CPPS = 4968, BS~ = 4656, ~ = 26,
DR - 36,707.
While the i~vention has been ~escribed with
refarence to its preferred embodiments, it will be
understood by those skilled in the;art that various
changes may be made and e~uivalents may be substituted
for elements thereof without departing from the true
spirit and scope of the invention. In addition, many
modifications may be made to adapt a particular situ-
ation or material to the teaching of the invention
without departing from its essential teachings.
-46-
