Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 FIELD OF TIIE INVENTION
_____ ________________
This invention relates to apparatus for tranferring
the setting of process control elements from a process
simulating apparatus to a process machine. In particular,
the invention is useful in connection with a system for
previewing the operation of a color scanner and for
transferring the control element settings from the previewer
system to the scanner.
BRIEF DESCRIPTION OF THE DRAWINGS
_________________________________
Figure 1 is a diagram illustrating a color printing
process using a color scanner;
Figure 2 is a block diagram of a graphic arts
previewing system;
Figure 3 is a schematic and block diagram illustrating
an apparatus for reading and recording the control positions
of a simulating system;
Figure 4 is a schametic and block diagram illustrating
an apparatus for adjusting the position of control elements
in accordance with the recorded signals.
Figure 5 illustrates a control element operating
mechanism in accordance with the present invention;
Figure 5A is a detailed view of the control element
connection in the apparatus of Figure 5.
Figure 6 is a view of the control panel of a color
scanner usable in the Figure 1 process.
BACKGROUND OF THE INVENTION
___________________________
Figure 1 illustrates the process typically used for
the manufacture of color prints. This process employs a
color scanner 12 comprising units 11, 13, 14 and 16. The
color original 10, which may be a photographic print or
g~:
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1 color transparency ls mounted to a rotating drum 11. A
light detector l3 detects the component color content of the
image 10 as various segments of the image are sequentially
scanned, by rotating drum 11 and by moving detector 13
across image 10 in a direction corresponding to the axis of
drum 11. The output of detector 13 is in the form of video
signals representative of the amplitude of the various color
components in sequentially scanned portions of image 10
which are provided to color correction computer 14. These
signals are usually representative of the yellow, magenta,
and cyan color content of image 10 and are represented in
Figure 1 by the letters Y, M, and C. Color correction
computer 14 is equipped with circuits for enhancing,
correcting and cross-correlating the component color signals
and is connected to exposure apparatus 16 which provides a
set of color separations. ~sually four separations are
made, each separation is a black and white transparent image
representative of a single color component in the original
image. Where four separations are provided they are usually
representative of the yellow, magenta, cyan, and black
components of the image. The color separations are used in
the etching of printing plates or cylinders 20. One
cylinder or plate is made corresponding to each of the four
separations and separations and the plates are used with
corresponding colored inks to sequentially print the
component color images on paper, to result in a composite
color image having all of the component colors.
Color correction computer 14 is provided with many
control elements for changing the characteristics of the
color separations manufactured by the scanner 12. Figure 6
1 illustrates the control panel of a typical prior art color
correction computer. It should be noted that the control
panel contains 8~ different control elements including
switches and potentiometers. The control elements are
arranged in an order corresponding to the four color
separations which the scanner manufactures and the various
controls, where applicable, are indicated Y, M, C and B as a
prefix to the control number. Control numbers unrelated to
a particular separation are labeled S for switches, and R
for potentiometers. The single meter has the prefix D.
With the larger number of controls available on a
typical color scanner, the quality of the separations
produced is largely dependent upon the skill of the scanner
operator. Based on the operator's evaluation of the color
original, it is necessary for him to make adjustments to the
control panel in a manner which he feels will produce
separations which will make an acceptable color print in the
actual printing process. After a first set of separations
has been made, it is necessary to manufacture printing
cylinders or plates and actually apply ink to paper to
determine whether the operator's judgment is correct. If
the resulting print does not satisfy the operator or editor,
it is necessary for the operator to adjust the control panel
of the color scanner and repeat the process making new
separations and printing plates. Alternatively, the color
separations or printing plates might be modified by etching
or other processes.
In order to facilitate the production of color prints,
there have been developed color printing previewing
apparatus which simulate the operation of the color scanner,
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1 including the color correcting computer. One such
previewing apparatus 23 is illustrated in Figure 2 wherein
the color original 10 is scanned by a video signal
generating apparatus 24 which may be a color TV camera or
similar device. Video signal generator 24 produces video
signals representative of the elementary colors in image 10
and provides them to a color correction computer 26 which is
similar or identical to the color correction computer 14
used in the scanner of Figure 1. The output of the color
10- correction computer 26 consists of video signals
representative of the color separations 18 used in the
actual printing process. These are supplied to a printing
simulator computer 28 which modifies the video signals in
accordance with the characteristics of the particular
printing process being used. The output signals from
printing simulator 28 are provided to a color display unit
30 which provides a color display image representative of the
resulting color print which would be produced using a
printing process with the color correcton computer control
elements set in accordance with the setting of the control
elements of computer 26.
An operator using the previewing apparatus 23 can
adjust the color correction control elements while viewing
display 30 and arrive at a set of control settings which
when applied to the actual color correction computer 14 of
the color scanner 12 will result in an acceptable set of
color separations which will produce the desired qualities
in the color print 22. As noted above, both the color
correction computer 14 and its simulator 26 may have on the
order of ninety control elements. It is both tedious and
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1 time consuming for an operator to manually adjust each of
the control elements of the color correction computer 14 in
the color scanner 12 in accordance with the readings of the
corresponding control elements on the previewer 23.
According to the present invention, a process
simulating apparatus may be used separately from a process
machine and the control settings transferred at the
convenience of the opera~or of the process machine.
SUM~ARY OF THE INVENTION
In accordance with the invention, there is provided a
control operating apparatus for use in connection with a
process machine having a plurality of adjustable process
control elements, which act on process signals to vary at
least one characteristic of the signals and thereby vary the
process. The apparatus comprises detecting means responsive
to an encoded storage media, for providing a sequence of
reference signals representative of desired control element
~ output signals when a predetermined set of process signals
-~ are applied to the process machine. The apparatus also
includes a signal generator for providing the predetermined
set of process signals to the process machine, sampling
means for providing a sequence of control element signals,
each representative of the output of one of the control
elements, operating means responsive to the reference
signals and the contro~ element signals for sequentially
varying each of the control elements until the control
element signals are equal to the reference signals and
control means for controlling the operation of the detecting
means, the signal generator, the sampling means and the
operating means.
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1 According to a preferred aspect of the invention, the
sampling means comprises means for sequentially connecting
each of the process control elements to the operating
means.
According to a further aspect of the invention, the
apparatus is used for controlling elements of a color
scanner in accordance with control position signals encoded
on a storage medium. The apparatus comprises detecting
means responsive to the encoded position signals for
providing a sequence of reference signals representative of
desired scanner control element output signals when a
predeteremined set of simulated video signals are applied to
the scanner; a voltage source for providing said
predetermined set of simulated video signals to the scanner;
a differential amplifier responsive to the reference signals
and control element output signals for providing an output
motor operated signal; first switch means for selectively
connecting the output of each of the control elements to an
input of the differential amplifier; a plurality of motors
each mechanically connected to one of the control elements;
second switching means for selectively connecting the output
of the differential amplifier to each of the motors; and
control means for operating the detectin~ means, the voltage
source and the first and second switching means, according
to a predetermined sequence.
DESCRIPTION OF THE INVENTION
____________________________
Figure 3 is a schematic and block diagram illustrating
the principle components of the invention as used in
connection with the graphic arts previewing apparatus 23 of
Figure 2. The input lines to the color correction computer
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1 26 contain video signals representative of the yellow,
magenta, and cyan components of the original image 10 as it
is scanned by the video signal generating appartus 24.
These video signals are coupled to a matrix of
potentiometers 38a, 38b, 38c, etc., which comprise the
control elements of the color correction computer.
Potentiometers 38 are connected together in a matrix which
provides for adjustment of the amplitude of each of the
video signals and provides for the intermixing of the video
signal in order to generate signals suitable for the
manufacture of color separations. Potentiometers 38 are
designed to be substantially identical to the corresponding
control element in the color correction computer 14 of the
color scanner with which the graphic arts previewing
apparatus is to be used. Each of the outputs of the wipers
of potentiometers 38, in addition to its interconnection in
computer 26, is also connected to multi-throw switch 40 by
one of the buffer amplifiers 39. Switch 40 is operated by
stepper 42 in accordance with control signals from control
unit 46. The output of switch 40 is connected to A to D
converter 44 which generates a digital signal representative
of the amplitude of the voltage at the wiper of the
potentiometer which is connected to A to D converter 44
through switch 40. In order to have a meaningful reading of
the position of potentiometers 38, there is provided a
signal generating apparatus which consists of multi-pole,
multi-throw, switch 50 and voltage generating circuit 48.
When the position of control elements 38 is to be read,
input switches 34 of the video signal inputs are connected
to switch 50. Voltage generating circuit 48 and switch 50
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1 are used to supply a predetermined set of voltages to the
video signal input switches 34 of color correction computer
36. The voltages supplied are selected in accordance with
the control element 38 being read. Switch 50 is operated by
stepper motor 52 under the influence of control unit 46.
The units 40 through 54 comprise potentiometer setting
recorder 32 in Figure 3.
In accordance with the invention, the input terminals
of color computer 26 are provided with signals which will
place a suitable voltage across the potentiometer to be
read, which is independent of the settings of the remaining
potentiometers which have not been read. For example, if
all of the video signal inputs are grounded to provide zero
input video signal voltage, certain of the potentiometers 38
will have a suitable applied voltage and this voltage will
not be dependent on the settings of the other
potentiometers. These particular potentiometers may then be
read by switch 40 and A to D converter 44. The wiper voltage
of the potentiometer is converted into a digital signal
which is provided to tape punch 54 and recorded on an output
paper tape 56. Each of the potentiometers is read in a
predetermined sequence. When all of the potentiometers
which are to be read with all zero input voltages have been
read, stepper 52 operates switch 50 to change the input
voltages provided to input switch 34.
The operation of switch 50 provides a second voltage
set to input switches 34, which provides a suitable voltage
at other potentiometers 38, which have not yet been read.
The voltage across each of the second set of potentiometers
should be dependent only upon the supplied voltage and the
1~ ~7~3~
1 settings of potentiometers which have previously been read.
This condition is necessary because the stored control
position signals on the punch tape will be used in the same
sequence for setting the controls of a color scanner.
Control unit 46 provides control signals to voltage
generator 48, stepper motors 42 and 52, and tape punch 54.
This provides a sequence of operations in which a given set
of signals is supplied at the input switch 34 of the color
computer, selected ones of the potentiometers are read for
the voltage at their wiper contacts, and the readings are
converted to digital form and stored on output tape 56 by
tape punch 54. This sequence is followed using different
input voltage combinations for selected one of the
potentiometers 38 until all of the potentiometers have been
read. The tape 56 then contains a complete set of the
potentiometer settings in color computer 26 and may be
removed from the potentiometer setting recorder 32 for use
in a color scanner at a later time.
Figure 4 is a schematic and block diagram illustrating
apparatus for using tape 56 to set the controls of a color
scanner. As previously mentioned, the color computer 14 of
a color scanner includes a plurality of potentiometers 60a,
60b, 60c, etc., each corresponding to one of the
potentiometers 38 in the graphic arts previewing
apparatus. The color computer 14 also has a set of input
video signal terminals having switches 58, each
corresponding to one of the component colors of yellow,
magenta and cyan. A voltage source 62, which is programmed
by control unit 76, provides a set of input signals to input
switches 58, which correspond to the signals supplied to
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1 switches 34 of color computer 36. A multi-throw switch 64
is connected to the wiper output of each of potentiometer
control elements 60 of color computer 14 by an isolation
amplifier. Switch 64 sequentially connects each of the
potentiometer outputs to differential amplifer 74.
Punch tape reader 70 is provided with the tape 56 made
by the tape punch 54 of the Figure 3 apparatus and provides
an output digital signal corresponding to the control
position signals stored on tape 56, one for each of the
potentiometers in the color computer. The control position
signals are converted from digital-to-analog form in D to A
converter 72 and supplied to differential amplifier 74. The
output of differential amplifier 74 is connected to one of
the motors 78 associated with potentiometers 60 by
multi-throw switch 68. Motors 78 are mechanically coupled
to the control rod of potentiometers 60 and are used to
sequentially drive the potentiometers to a position in which
their output signal is equal to the output of D to A
converter 72.
The apparatus of Figure 4 operates to adjust the
position of the control elements of color computer 14 in a
color scanner by the following sequence. Control unit 76
provides a signal to voltage source 62 which causes the
source to provide a selected set of predetermined simulation
voltages to input switches 58 of color computer 14. Control
unit 76 activates stepper motor 66 to move multi-throw
switches 64 and 68 to the positions corresponding to the
wiper and motor respectively of the first of the control
element potentiometers 60 in accordance with the same
sequence used in the Figure 3 apparatus. In addition,
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1 control unit 76 causes reader 70 to read the first stored
digital control position signal on punch tape 56
corresponding to the desired position of the first
potentiometer 60. The digital control position signal is
converted to analog form by D to A converter 72 and supplied
to differential amplifier 74 along with the actual wiper
voltage fo the first potentiometer 60. If the voltages at
the input of differential amplifier 76 are different, there
results a control signal which is supplied to the motor
mechanically coupled to the first potentiometer which
rotates the potentiometer shaft until the signals are
equal. When the two signals are equal, the output of
differential amplifier 74 drops to zero. This condition is
sensed by control unit 76 which activates the control unit
to cause voltage source 62, reader 70, and stepper motor 66
to move to the next sequential position.
The detailed structure and operation of the invention
may be understood by reference to its implementation in
connection with a particular piece of equipment, such as the
color scanner whose control panel is illustrated in Figure
6. In order to obtain motor driven operation of the control
elements of the scanner control panel, a device such as
illustrated in Figure 5 may be used. The Figure 5 device
includes a chassis 80 within which there are mounted drive
motors 78 corresponding to the control elements of the
scanner. The scanner control knobs have been removed from
their respective shafts on the scanner leaving protruding
shaft ends 82 projecting from the control panel. Chassis 88
includes a plurality of shafts 84 each corresponding to one
of the control element shafts 82. Gears 86 are mounted
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1 sha~ts 84 and mate with corresponding gears 88 mounted to
drive motors 78 which are connected to the circuit shown in
Figure 4. For convenience of installation, shafts 84 are
mounted to chassis 80 such that they will move between two
axial positions in the direction indicated by the arrow S.
The control knobs 90 which have been removed from their
shafts 82 on the scanner contol panel may be mounted to the
ends of shafts 84 which protrude from chassis 80. Shafts 84
are connected to shafts 82 preferably by the coupling
illustrated in the exploded view of Figure 5A. Coupling
elements 92 and 96, whieh have protruding sections, are
fixedly mounted on shafts 82 and 84 respeetively. A eentral
eoupling element 94 is provided whieh has transverse grooves
eorresponding to the protruding seetions on parts 92 and 96
sueh that when the shafts with their eorresponding eoupling
elements are brought into eontaet with eoupling element 94,
the protruding sections on parts 92 and 96 engage the
respective grooves on coupling element 94. A sleeve 98
surrounds the entire coupling meehanism in order to prevent
eoupling element 94 from slipping off either part 92 or 96
prior to engagement. This type of eoupling is useful for
making the blind eonneetion between shafts 84 and 82 when
ehassis 80 is plaeed in position over the eontrol panel of
the scanner. Eaeh of shafts 84 is initially moved to its
axial position away from shaft 82. Therefore, the
eorresponding eonneeting part 96 attaehed to shaft 84 is
disengaged from eentral eoupling part 94. This permits the
mounting of ehassis 80 to the eontrol panel of the seanner
without interferenee from the shaft eonneetions. Eaeh of
shafts may then be individually rotated while being urged
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1 into its downward position along arrow S, and when the
projecting part of mating piece 96 engages the groove in
cental part 94, the shaft 84 may be moved to its lowermost
position in which case the two shafts are rotationally
coupled together. Control knobs 90 are attached to
projecting shafts 86 and permit manual operation of the
scanner control elements in the same manner as prior to the
control unit installation.
The sequence of operation for the reading of control
position settings on a graphic arts previewer and the
sequence for setting the control elements of a color scanner
are exemplified by the following table which indicates a
sequence having 69 steps, each corresponding to a selected
one of the 89 control elements on the scanner contrtol panel
illustrated in Figure 6. Not all of the control elements
are automatically set, since some of the control elements
consist of multi-position switches which may be easily set
and other control elements can be easily set by manual
positioning. It has been found to be convenient to use
three drive chassis 80 of the type illustrated in Figure 5
for setting the controls of the color scanner illustrated in
Figure 6. A first drive chasis is used to control the 32
potentiometers on the left of the control panel. A second
drive chasis is used to control the potentiometers labeled
Y-50 through R-69 and third drive chasis is used to set
potentiometers Y-70 through B-89. The switches and
potentiometers grouped in the center of the control panel
are set manually by the operator. Many of these are
adjusted only in the event of a change in the type of
original image or a change in the type of printing process.
3V
1 As noted above, for convenience in identification, the
control elements in the Figure 6 control panel have been
given letter prefixes Y, M, C and B for the colors yellow,
magenta, cyan, and black, which are indicated by the color
of the control knob on the color scanner. Control elements
which consist of potentiometers which do not have any color
significance are labeled with the prefix R and switches have
the prefix S. The single meter of the control panel has a
prefix D.
TABLE
Sequence Input Voltages Control Element
No. Y M C No.
___________________________________________________________
1 0 0 0 R 69
2 0 0 0 Y 53
3 0 0 0 M 54
4 0 0 0 C 55
0 0 0 R 65
6 0 0 0 R 67
7 0 0 0 R 68
8 0 0 0 B 31
9 0 0 0 R 73
0 0 0 R 87
11 0 0 0 B 63
12 10 0 0 Y 50
13 10 0 0 Y
14 10 0 0 M 9
0 0 C 17
16 10 0 0 B 25
17 10 0 0 Y 56
18 10 0 0 R 62
19 10 0 0 B 32
0 0 R 79
21 0 10 0 M 51
22 0 10 0 Y 2
23 0 10 0 M 10
24 0 10 0 C 18
0 10 0 B 26
26 0 10 0 M 57
27 0 10 0 Y 59
28 0 10 0 C 61
29 0 10 0 Y 3
0 10 0 M 11
31 0 10 0 C 19
32 0 0 10 B 27
33 0 0 10 C 52
1 Sequence Input Voltages Control Element
No. Y M C No.
____________________________________________________________
34 0 0 10 Y 6
0 0 10 M 14
36 0 0 10 C 22
37 0 0 10 B 30
38 0 0 10 C 58
39 0 0 10 M 60
0 6 10 Y 4
41 0 6 10 M 12
42 0 6 10 C 20
43 0 6 10 B 28
44 0 .07 10 Y 5
0 .07 10 M 13
46 0 .07 10 C 21
47 0 .07 10 B 29
48 0 .08 .32 Y 7
49 0 .08 .32 M 15
0 .08 ~32 C 23
51 0 .07 .31 Y 8
52 0 .07 .31 M 16
53 0 .07 .31 C 24
54 10 10 10 Y 81
M 82
56 10 10 10 C 83
57 10 10 10 B 84
58 10 10 10 B 89
59 10 10 10 R 86
R 88
61 10 10 10 R 64
62 0 0 0 Y 75
63 0 0 0 Y 70
64 0 0 0 M 76
0 0 0 M 71
66 0 0 0 C 77
67 0 0 0 C 72
68 0 0 0 B 78
69 10 10 10 R 66
The above table sets forth a sequence for reading the
control elements of a graphic arts previewing apparatus and
setting the control elements of a typical color scanner,
such as Hell Chromograph DC 300 scanner. In accordance with
the sequence, after the graphic arts previewing apparatus
has been adjusted so that the display depicts an acceptable
color print, the system is activated to automatically
readout the settings of the control elements on the graphic
arts previewing apparatus and record those settings on a
paper tape or other storage device. The sequence set out
li.l~43~)
1 above is by no means unique, but has been selected for
convenience and for providing a small number of different
sets of input voltages and so that the control elements of
the color scanner are set in an order in which the voltage
applied to any particular control element is not dependent
on the setting of a control element which has not yet been
set.
Control unit 46 of the Figure 2 apparatus initiates
the sequence by giving a command to the voltage generating
apparatus 4~ and multi-pole switch 50, which causes the
switch to be set to supply zero input voltage at all of the
input switches 34. At the same time, stepper 42 is
activated such that switch 40 connects control elsment R 69
of the grahic arts previewer to A to D converter 44. An
additional control signal causes the punch unit 54 to record
the voltage output of control element R 69 on paper tape
56. When this has been accomplished, control unit 46
activates stepper 42 to move switch 40 and connect control
element Y 53 to A to D converter 44, for the second step of
the control element reading sequence. After step No. 11 of
the sequence, control unit 46 provides a control signal to
stepper 52 and voltage source 48, which causes an input
voltage of 10 volts to be applied to the yellow video signal
input terminal while the remaining video signal input
terminals remain grounded. The control unit then activates
the process of reading the control element outputs in the
sequence indicated by the table. When the output signals
from all the control elements in the sequence have been
read, the paper tape may be detached from the paper tape
punch and transferred to the color scanner along with the
16
ii i7431~
1 original image 10 for use by the scanner operator in making
color separations.
it is an important feature of the invention that the
color scanner can be operated independent of the graphic
arts previewer, and the operation of the two machines for
any particular original need not be coordinated in time.
The original image and output tape from the graphic arts
previewer can be stored until time is available on the color
scanner for producing separations from the corresponding
original. In order to set up the color scanner control
elements, the scanner operator inserts punched tape 56 into
tape reader 70 and activates control unit 76 to initiate the
tape reading and control setting cycle. This cycle follows
the same sequence, set forth in the table above, according
to which the signal outputs from the control elements of the
graphic arts previewer were read~ In the control setting
cycle control unit 76 causes voltage source 62 to supply the
first set of input voltages, all inputs zero volts, to input
switches 58 of the color computer. Tape reader 70 then
reads the digital signal representative of the output
voltage of control element No. R 69 which is stored on tape
56 and supplies it to D to A converter 72 which generates a
reference voltage. Stepping motor 66 operates switches 64
and 68 to connect the output terminal of Control No. R 69 on
the color scanner to differential amplifier 74, and
simultaneously connect the output of differential amplifier
74 to the motor 78 connected to control element R 69.
Differential amplifier 74 provides an output signal to
switch 68 and motor 78 connected to control element R 69,
which causes motor 78 to turn, varying the position of
1~17~3~
1 control element R 69 until its output signal is equal to the
stored output signal derived from tape 56 which is supplied
to the other terminal of differential amplifier 74. When
the two signals supplied to the differential amplifier 74
are equal, the output of the differential amplifier
approaches zero volts, a condition sensed by control unit 76
which activates reader 70 to read the stored position signal
corresponding to the next control element, control Y 53, and
supply a new reference signal in analog form to differential
amplifier 74, while stepper switch 66 connects the output of
control element Y 53 and the motor corresponding to control
element Y 53 to differential amplifier 74. This process is
repeated until all the control elements of the color scanner
which are motorized have been set. At appropriate points in
the sequence, the control unit 76 supplies a control signal
to voltage source 62 which causes source 62 to change the
input voltages supplied to input switches 58. It has been
noted above that not all of the control elements of the
color scanner need be motorized. Those controls which are
not motorized may be manually sent by recording their
positions when the image is previwed on the graphis arts
- previewer and by having the operator of the color scanner
adjust the position of these controls where necessary or
appropriate. In many cases, the control positions need not
be changed from one image to the next.
It will be evident to those familiar with the art that
the apparatus of the invention may be applied to systems
other than color scanners and graphic arts previewers. In
general, the system is applicable for use with a process
machine having variable control elements and with a process
18
~1117~
1 simulation apparatus having corresponding control elements.
Similar electronic devices may simulate chemical processes,
such as photography, or mechanical or electrical processes,
such as the manufacture of tape recordings or phonograph
records.
It will also be evident to those familiar with the
electronic art that components other than those illustrated
may be advantageously used in a device in accordance with
the invention. The invention as illustrated makes use of
multi-throw and/or multi-pole stepping switches. Those
familiar with digital circuitry will recognize that such
switches may easily be replaced with solid state multiplex
circuits which perform the switching function in accordance
with digital control signals. Similarly, the tape punch
apparatus as described above may be replaced with any
similar storage device, such as a magnetic tape, disk
recorder, or card punch. It is also possible, and practical
in some cases, to implement the invention without the use of
a storage medium by directly connecting the output of switch
40, which is connected to the control element of the process
simulating apparatus to one of the poles of differential
amplifier 74. The use of a storage medium, such as tape 56,
facilitates separate and independent use of the process
simulation apparatus, such as a graphic arts previewer, and
the process machine, such as the color scanner.
The invention may also be applied to systems whihch
use control elements other than potentiometers. The control
elements used in a system may include variable capacitors,
or inductors, or even variable gain amplifiers. In such
applications it may be necessary to use different or more
19
743Q
1 complex test signals in the control element reading and
setting operation. In some cases, for example, it may be
necessary to make use of single freguency tone signals or
the like for setting the contrQl elements. In these cases,
the characteristic output of control elements may be
something other than the voltage at the output of the
elements. Accordingly, different detector and test signal
generator circuits would be appropriate.
