Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~OLOGRAM SCANNER
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hologram
scanner which scans an objective by using a laser beam
diffracted by a hologram.
2. Description of the Related Art
A bar-code reader is used in a market control
system in a supermarket or the like. Such a bar-code
reader reads a bar-code printed on a commodity and
inputs the information data to a computer to control the
operation of the supermarket. A hologram scanner is
used as a bar-code scanner o the bar-code reader. The
prior art is discussed hereinafter in greater detail.
SUMMARY OF THE INVENTION
A primary object of the present invention is to
provide a hologram scanner which makes it possible to
scan perpendicularly to the rotational axis of the
hologram and effectively receive the scattered light,
and which allows the scanner to be made compact.
An~ther object of the present invention is to
provide a hologram scanner which makes it possible to
enhance the safety strength level of each scanning beam
as much as possible, without enlarging the width of the
scanning window through which the scanning beam passes.
In accordance with one particular aspect of the
present invention, there is provide~ a hologram scann~r
comprising: a laser source; a rotary body having a
ro~atlonal axis; at least one hologram facet arranged on
the rotary body for diffracting a laser beam from the
laser source to scan an objective and receive the
scattered light from the objective for detection
thereo~; a motor means for driving the rotary body; and,
; an optical detector for detecting the scattered light
r~ceived and diffracted by the hologram facet, wherein
;~ the hologram facet is inclined with respect to the
rotational axis oE the rotary body.
~nother object is achieved by various embodimQIlts *
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of the present invention as well as further objects, as
can be understood from the description with reference to
the accompanying drawings illustrating preferred
embodiments of the present invention.
BRIEF DESCRIPTIO~ OF THE DRAWINGS
Fig. 1 is a constructional view of a hologram
scanner in accordance with the prior art,
Fig. 2 is a side view of a hologram disc in
accordance with the prior art;
FigO 3 is an explanatory view of the scanning beam
in accordance with the prior art;
FigO 4 is a constructional view of a hologram
scanner in accordance with the present invention;
Figs. 5 to 8, on the same sheet as Fig. 3, are
perspective views of different examples of the rotary
body of the hologram scanner in accordance with the
present invention;
Fig. 9 is another perspective view of another
example of the rotary body of the hologram scanner;
Figs. 10 and 11 are upper views of different
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examples of the rotary body of the hologram scanner in
accordance with the present invention;
Fig. 12 is an explanatory view of ~he hologram
construction method in accordance with the present
invention;
Fig. 13 is a constructional view of a bar-code
reader using the hologram scanner in accordance with the
present invention, ana
Figs. 14 to 35 are constructional views of
dlfferent embodiments of the present invention,
respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 is a constructional view of a hologram
scanner used as a bar-code reader according to the prior
art. The scanner comprises a laser source 2, a beam
expander 3, a hologram disc 4 comprising a plurality of
hologram ~acet elements, a motor 5 for driving the
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hologram disc 4, a mirror 9 having a throughhole 9a at
the center thereof for passing a laser beam, a condenser
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lens 10, and an optical detector 11, within an outer box
1. A laser heam from the laser source 2 passes throu~h
the throughhole 9a of the mirror 9 and is diffracted by
a rotating hologram disc 4 so that the laser beam scans
a bar-code 12 printed on a commodity 13, as a scanning
beam 7 through a window 6. The laser beam 7 irradiated
onto the bar-code 12 is scattered and a part of the
scattered light returns toward the hologram disc 4l as
shown by the number 8 in the drawing. The scattered
light 8 i5 diffracted by the hologram 4, reElected by
the mirror 9, and detected by the detector 11 through
the lens 10.
Each constitutional component, such as the laser
source 2, the hologram disc 4, the motor 5, the mirror
9, and the detector 11, of the hologram scanner is
individually attached to the outer box 1 of the bar-code
reader, together with the other components such as a
control circuit, an interface unit and a power souece.
Such a structure is not compact and is inconvenient to
handle, which causes difficulties when assembling the
bar-code reader since the positioning of the parts of
the hologram scanner is not easy.
The hologram disc 4 of the prior art scanner
comprises a disc plate perpendicular to the rotational
axis thereof. Therefore, the diffraction angle
(Fig. 2) of the scanning beam 7 must be large for
elongatin~ the scanning line traced by the scan~ing
point A with respect to every r~tational angle of the
hologram disc 4. However~ if the diffraction angle ~ is
enlarged, the amount of the scattered light 8 received
by the hologram disc 4 decreases, which results in the
degradation o~ the reliability of the detection.
The reading ability of the scanner is upgraded as
the laser beam is strengthened. However, the eyes of
the operator or customer may be damaged if the laser
beam is excessively strengthened. The laser beam
strength must not exceed the safety standards for the
human eye. The prior art method for enhancing the
allowable laSer beam strength in accordance with the
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safety standards is illustrated in Fig. 3. Ihe laser
beam for scanning in one direction is divided into two
beams which are separated from each other by more than 7
mm at the outside of the scanning window 50' (d > 7 mm),
by using hologram facets having slightly different
diffraction angles. The ~wo separated beams (dash line
and solid line) scan in the same direction, e.g.V in the
direction perpendicular to the drawing sheet. By using
t~o separated beams in one scanning direction, the
strength of each of the beams can be enhanced, even if
they continuously scan one after the other in -the same
direction, since they are deemed to be independen~ of
each other. However, in such an arrangement, the width
of the window 50' formed in the cover plate 49' disposed
over the glass plate 48' must be enlarged to allow the
passage of the two separated beams, which can lead to
accidental damage of the glass plate by the article to
be scanned above the window 50l.
~n embodiment of the present invention is illus-
trated in Fig. 4. A motor 25 is secured on a frame 20~
A rotary body 28 is attached to a rotary shaft 21 of the
motor 25. The rotary body 28 comprises at leas~ one
hologram Eacet 24 on which a hologram (not shown) is
constructed. The hologram facet 24 is inclined with
respect to the rotary shaft 21. A Fresnel mirror 26 is
di~posed on the upper inner surface of the rotary body
28 to reflect and converge a parallel beam Elux. A
metallic reflection film (not shown) is coated on the
front surface or the rear surface (facing the upper
inner surface of the rotary body 28) of the Fresnel
mirror 26.
The rotating body 28 has the shape illustrated in
Fig. 5. ~wo hologram facets 24 form a wedge at an end
of a cylindrical body. Variations of the rotary body 28
are illustrated in Figs. 6 to 9. The rotary body 28 of
Fig. 6 comprises our hologram facets 24 forming a
quadrangular pyramid at an end of a cylindrical body.
The rotary body 28 o Fig. 7 comprises four hologram
facets 24 ~orming a quadrangular pyramid at an end of a
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square pillar. ~he rotary body 28 of Fig. 8 comprises a
conical facet 24 at an end of a cylindrical body. Two
hologram facet elements 24a and 24b having different
diffraction angles may be formed on the same plane, as
illustrated in Fig. 9. Th~ number o~ hologram facets
may be three, four, or five or more to form a pyramid.
Each hologram facet 24 diffracts a scanning beam to
irradiate an objective and simultaneously receives a
scattered light from the objective for the detection
thereof. Therefore, each hologram facet 24 must be large
enough to receive a critical amount of the scattered
light to recognize the objective. Taking this point into
consideration, the rotary body 28 comprising two hologram
facets 24 illustrated in Fig. 5 is the most preferable
from the standpoint of compactness and productivity.
A laser diode module 22 which emits a plane wave
laser beam having an predetermined diameter and a
mirror 23 for reflecting the laser beam are secured to
the frame 20 (Fig. 4). An optical detector 29 is also
secured to the frame 20 at the position facing the
lower end of the rotary body 28. A concave lens 27 is
installed at the lower end of the rotary body 28 for
the following reason. The scattered light (dash lines~
from the objective is converged toward the center of
the lower end of the rotary body 28 by the function of
the Fresnel mirror 26. It is desirable to make the
converging area at the Iower end of the rotary ~ody 28
as small as possible to enlarge the hologram facet area.
The optical detector 29 ~or detecting the converged beam
is disposed at a distance~below the lower end of the
rotary body in such a manner that the detec~or does not
come in contact with the rotary body~ Therefore, the
concave lens 27 is needed to elongate the focus position
from the proximity of the rotary body end to the optical
detector 29.
~ The upper plate 28a (Fig, 10) of the rotary bo~y 28
- has a plurality of slits 28a in a circle to pass~the
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laser beam therethrough.
Another arrangement for passing the laser beam
through the upper plate 28a of the rotary body 28 is
illustrated in Fig. 11. In this arrangement, the upper
plate 28a is made of a transparenk material and the
metallic reflection film is noncoated along a circular
track 39 on the front surface or the rear surface of the
Fresnel lens 26 (Fig. 43 to pass the laser beam through
the circular track 39. The track 39 is not embossed to
form the Fresnel lens so that the beam passes straight
therethrough. By this arrangement, the rotary body 28
can be securely sealed, which stabilizes the function of
the hologram. In an alternative arrangement the laser
beam can be introduced into the rotary body through a
hologram facet, being reflected within the rotary body
and emitted therefrom through the hologram facet, being
diffracted thereby.
A desirable method for constructing a hologram used
in the hologram scanner of the present invention is
illustrated in Fig. 12. A plane wave beam 43 and a
spherical wave beam 42 are irradiated at a same
incidence angle C~upon photosensitive emulsion 41 coated
on a transparent substrate such as a glass plate 40.
The beams 4~ and ~3 interfere with each other and form
interference fringes 110 in the photosensitive emulsion
41. The Bragg plane of the interference fringes 110
formed by such a method is perpendicular to the
substrate surface. Therefore, the Bragg angle does not
change, irrespective of any change in the thickness of
the emulsion during the chemical treatment such as
developing and fixing the emulsion, which results ln a
high diffraction efficiency at the time of the
reconstruction of the beam through the hologram.
It is desirable that the incidence angleC~ be 45
degrees, since a laser beam irradiated vertically along
the rotational axis can be diffracted in the horiæontal
direction, by inclining the hologram at an angle of 45
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degrees with respect to the vertical rotational axis,
which makes it possible to achieve an effective scanning
without decreasing the amount of the scattered light
received by the hologram.
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The hologram scanner of Fig. 4 constitutes a
scanniny unit 30 formed in one moduIe combining the
laser source 22, the rotary hody 28, the optical
detector 29, the mirror 23, and the motor 25, on the
5 frame 20. Such a scanning unit module 30 is installed
in a bar-code reader, for examp~e, as illustrated in
Fig. 13. The scanning unit 30 i5 installed within an
outer frame 30 together with a drive control means 32,
an interface means 33 for communicating with a central
processing unit, and a power source 34. The laser
beam emitted from the scanning unit 30 is reflected by
mirrors 36 and 37 and passes and scans a bar-code 12
of a commodity 13 through a window 35.
As mentioned above, each hologram facet of the
hologram scanner of the present invention is inclined
with respect to the rotational axis of the rotary body.
Therefore, it is possible to scan in the dir2ction
perpendicular to the rotational axis of the rotary body,
which increases the efficiency of scanning, since the
scanning range with respect to the rotational angle
of~the rotary body is widened, and which~also makes
it possible ~o use a small hologram facet sinc the
scattered light can be effectively received, thus
obtaining a compact scanner.
Also, the constitu~t1onal components of the hologram
scanner are united in a body as one module. The module
; per~orms a complete scanning function by itself as one
system, from~emission of the laser beam to detection of
the scattered light, an~th~`me;chanical accuracy~is
30~ guaranteed by the module. ~Therefore, var~ious~reading
devices are~easily~assembled by using such a scanning
module, which reduces the total cost of producing the
device. Assemb~ling ~he~hologram scanner as one compact
module with a high~mechanical~accuracy is more easily
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achieved than~assé~bling the components o~ the scanner
individually at the time of fabricating the reading
device in which the scanner is installed.
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Also, by using such a compact scanning module, the
reading device becomes small.
Other examples of the rotary body 28 of the hologram
scanner in accordance with the present invention are
illustrated in Figs. 14 to 20. These examples are
featured in that they comprise a means for changing the
incidence point of the laser beam on the hologram facet
in such a manner that the passage of the beam diffracted
by the hologram facet is changed.
In the example of Fig. 14, the incidence point of
the laser beam 52 on each of the hologram facets 44
and 45 is changed by disposing each of the hologram
facets 44 and 45 on a different level. The laser beam
which passes through the holsgram face~ 44 is re~lected
by mirrors 46 and 47, passes through the glass plate 48
and the wlndow 50 of the cover 49, and scans the objec-
tive (not shown) above the cover as illustrated by a
solid line in the ~igure. On the other hand, the laser
beam which passes through tha hologram facet 45 passes
in a direction as illustrated ~y a dashed line, and is
emitted through the same window 50. The level of each
of the hologram facets 44 and 45 and the position o~the
mirrors 46 and 47 are determined so that~th~ tWQ beam
passages ~solid line~and`dashed line) intersact each
other around the window 50. The in~ersection~angle ~
is;~arranged to be more than 1.45 degrees (5 x 10 4 Sr~,
which is prescribed as a necessary minimum angle (solid
angle~ or deeming that two~i~tersecting lines of a beam
~are individual, in the laser safety~standard~ of the
3~ IEC ~International Electrotechnical Commission). These
two beams scan~i~n th~samé;direction~contlnuously one
after the other on the~ same obj~ective as two individual
scanning beams. Therefore,~the allowable strength of
each beam in accordance with the safety standards can
~e strengthened, which upgrad~s the~ reliability of the
scanning and reading. A~lso, the two beams intersect
around the window~of the~cover plate s~o that the width
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of the window 50 can be narrowed, when compared with the
prior ar~ of Fig~ 3, and thereby the glass plate 48 is
effectively protected by the co~er plate 49.
In the example of Fig. lS, the rotational shaft S1
of the rotary body 28 is eccentrically arranged with
respect to the center axis of the rotary body 2B, so
that the incidence point of the laser beam 52 on the
hologram facet 54 is shifted from that on the hologram
facet 53.
1~ In the example of Fig. 16, a reflection slit 57
ha~ing inclined side mirror walls and a penetration
slit 58 having vertical side walls are formed in the
upper plate 28a of the rotary body 28. In this arrange-
ment, the passage of the laser beam 52 is separated into
two different passages after passing through the upper
plate 28a, one being the passage of the beam passed
through the reflection slit 57 (solid line), and the
other ~eing the passaye of the ~eam passed through the
penetration slit 58 (dashed line), thereby changing the
incidence point of the beam on the hologram facet 55
from that on the hologram facet 56.
In the example of Fig. 17, instead of the pene-
~ration slit 58 of Fig. 16, another reflection slit S9,
which has inclined side mirror walls inclined in reverse
to the mirror of the Slit 57, to reflect the beam in the
direction reverse to the reflection direction of the
slit 57 is formed in the upper plate 28a of the rotary
: body ~8.
: In the example of Fig. 18, the mirro~s 61 and 63
are eccentrically provided~on the upper plate 60 to
separate the passage of the beam 52 into ~wo passages,
: one being the passage of the solid line passing through
thè hologram facet 62 and the other being the passage of
: the dashed line passing through the hologram facet 64.
: 35 In the example of Fig. 19, hologram facets 65a and
: ~ 67a are formed on the lower surface of ~hick transparent
~ ~ , plates 65 and 67, respectively. A hologram piece 68 is
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formed on the upper surface of one of the plates 67 and
a window 68a is formed in the lower hologram fa~et 67a
corresponding to the upper hologram piece 68 so as to
pass the beam di~fracted by the upper hologram piece 68.
The passage of the beam 52 passing through the same
inlet 66 is differentiated after passin~ thxough the
thick plate 65 or 67. The rotary body 28 of Fig. 19 is
substantially sy~netric in weight with respect to the
rotational shaft, which results in a smooth rotational
movement, compared with the examples of FigsO 14, 15,
and 18.
In the exampIe of Fig. 20, the upper ~embexs of the
rotary body 28 are inclined. A refractive member 70 is
disposed above one of the hologram facets. The other'
upper plate member disposed above the other hologram
facet has a through hole 73 for passing through the
laser beam. The laser beam which passes through the
refractive member 70 is refracted as illustrated in a
solid line, while the laser beam which passes through
the~throughhole 73 of the other upper plate passes
straight as illustrated in a dashed line.
- Variations of an emhodiment of the present invention
are illustrated in Figs. 21 to 23. These embodiments
are featured in;that they~compri~se an improved means
25 ~for~driving the rotary body, which makes it possi~le to
obtain a more compa~ hologram scanner~ ~
In the example of Fig, 21, the cylinder portion 76
of the rotary body~28~is rotatably~supported by a
bearing means 75~. A~plurality~of~electromagnet coils 77
are disposed around the cylinder~portion 76, so that the
rotary body 8 itself constitut~es a~motor, in which the
cylindrical portivn 76 con titutes a rotor of the motor
and the coils~77 constitute a stator of the mo~or.
In the~example~of Fig.~ 22, a hollow shaft 79 is
secured to the frame 20. ~The rotary body 28 lS rotatably
attached to the~hollow shaft 79. The hollow shaft 79
has a coil 80 inside of~the rotary body 28, so that a
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motor is formed in which the rotary body 28 constitutes
a rotor and the hollow shaft 79 constitutes a stator of
the motor. A support plate 78 is secured to the hollow
shaft 7~. A Fresnel mirror (not shown) is disposed on
the under side of the suppoxt plate 78. A laser diode
module 22 is mounted on the support plate 78. Electric
lines 83 connected to the laser diode module 22 and
electric lines 84 cvnnected to the coil 80 of the stator
are disposed within the hollow shaft 79.
In the example of Fig. 23, the optical detector 29
is disposed within the rotary body 28 so as to make the
scanner even more compact than ~he example of Fig~ 22.
The optical detector 29 is secured to the end of the
hollow 3haft 79 and a mirror 82 for converging the
scattered light is disposed at the end of the rotary
body 28~ Electric lines 85 connected to the optical
detector 29 are further disposed within the hollow
shaft 79. The other constructions are substantially
: the same as those of Fig. 22.
: : 20: Another embodiment of the present invention is
illustrated in Fig. 24. In this example, a motor
: shaft 21 penetrates the inside of the rotary ~vdy 28
:: along the entire length thereof. With this arrangement,
the rotary body 28 i3 firmly secured to the motor
: 25 shaft 21 so that the rotary~body 28 rotates smoo hly
;~ without generating vibration. Numeral 89 designates a
transparent Fresnel len~.
Further variations:of the embodiment of the present
invention are illustrated in Figs.~25 and 26. These
~examples are fea~ured in that they comprise a means for
~ condensing the scattered light behind the hologram facet
.~ : so as to shorten the rotary~body in height.
: : In the example of Fig. 25, a condensing optical
~' element 86, such as a:Fresnel lens or hologramt is
disposed behind each~hologram facet 24.: The scanning
: ~ laser beam (solid line) passes through A window 87 of
~ the optical element 86 and is diffrJcted by tbe hologram
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facet 24. The scattered light (da~hed line) is xeceived
and diffracted by the hologram facet 24 and condensed by
the optical element 86, then reflected by the Fxesnel
mirror (not shown) disposed on the lower side of the
upper plate of the rotary body 28, a:nd converges to the
position of the optical detector 29.
In the example of Fig, 26, the ~window 87 of one of
the optical elements 86' is filled with a devia~ion
means 88 such as a holo~ram. A window 88' for passing
the beam diffracted by the deviation means is formed
in the hologram facet disposed below the optical
element 86'. With such an arrangement, the passage of
the laser beam 52 is separated into two p~ssages (~olid
line and dash-dot line) in a manner similar to that of
lS Fi~. 19, and the scattered light is condenced by each of
the optical elements 86, ~6' in the manner similar to
that of Fig. 25~
Further variations o~ the embodiment of the present
in~ention axe illustxated in Figs~ 27 to 30. T:hese
examples are featured in that the laser beam i~ intro-
duced into the rotary body through a p~rtion other than
:the upper plate thereof. With such an arrangement, the
motor for driving the rotary body can be disposed close
to the upper plate of the rotary body, sinc~ the laser
source and the mirror can be removed from the gap between
the motor and the rotary body, so that the scanner
becomes more compact and the rotary body rotates smoothly
and stably at a high speed.
In the example o~ Fig. 27, the laser beam 52 is
reflected by a mirror 92:disposed at the proximity of
: the lower end of the rotary body 28 and introduced into
the rotary body 28 through an opening 108 at the lower
end thereof. The introduced laser beam is reflected by
a mirror 93 disposed annularly in the Fresnel mirror 26
and diffract~d by the hologram facet 24.
In the example of Fig. 28, an annular paraboloidal
; mirror 91 is disposed in a paraboloidal mirror 90 for
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converging the scattered light, instead of the annular
mirror 93 disposed in the Fresnel mirror 26 of Fig. 27.
The laser beam 52 is introduced into the rotary body 28
and emitted therefrom in a manner similar to that of
Fig. 27. The focus of the paraboloidal mirror 90 is
on the optical detecter 29 disposed o:n the rotational
axi3 of the rotary body 28. The focus of the annular
paraboloidal mirror 91 is at the intersection point of
the rota~ional axi~ of the rotary body 28 with the
passage of the incidence beam to this mirror 91.
In the example of Fig. 29, the laser beam 52 is
i~troduced into the rotary body 28 through the hologram
facet 24. The la~er beam 52 is irradiated on the
hologram facet 24 at an incidence angle far from the
Bra~g angle so that a great part of the beam penetrates
stxaight through the hologram without being diffracted.
Paraboloidal mirror~ 96, 97 are dispo~d on the lower
side of the upper plate o~ the rotary body 28, in the
same manner as that of Fig. 28.
In the e~ample of Fig. 30, the laser beam 52 is
introduced into the rotary ~ody 28 through its cylin-
drical side wall 96, which is made ~f a transparent
material. Numeral 94 designates a cylindrical lens.
The ~laser beam 52 Is re1ect~d by a conical mirror 95
~: 25 dispo~ed at the~center of:~the lower side of the upper
~: plate of the rotary body 28,~ and diffracted by the
:~ hologram facet 24. A Fresnel mirror tnot shown) is
also disposed on the:~lower side of:the upper plate of
the~rotary body 28.
~A further~embodiment;of the present invention is
illustrated in Fig. 31. In this example, the side
: wall 98 of the rotary body:28 is~ormed as a hologram
acet. The scat~ered light: ~rom the ob~jective is
received hy the holog~am of the side wall 98 and
diffracted toward the lo~er end of the rotary body 28
where the optical detector 29 i8 dispo~ed. With ~uch a
; construction, the amount o~ the scattered light received
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by the hologram facet i~ increased, which upgrades the
detection reliability. The side wall 98 is a cylindrical
wall c,r a plate constituting a polygon pillar. The
hologram of the side wall 98 is constructed by using a
spherical wave diverging from the scanning point of
the objective as the object beam and a spherical wave
converging toward the central lower end of the rotary
body as the reference beam.
A further embodiment of the present invention is
illustrated in Fig. 32. In this example/ the opening 99
at the lower end of the rotary body 28 is very small
and the scattered light (dashed line) is converged to
this opening 99. The scattered light diverges from the
converged point at the opening 99 and again converges
through a convex lens 100 disposed outside of the rotary
body 28 so that the converged beam is detected by the
optical detector 29. A hologram or an ellipse mirror
may be used for converging and deviating the scattered
beam to a desired position,~instead of the convex
, 20 lens lO0.
Further embodiments of~the present invention are
illustrated in FigsO 33 and 34. In these examples, one
inclined hologram facet~24 is~disposed on the lower side
; of ~he rotary body 28.
~In the example of~Fig. 3~3, a cylinder 76 of the
rotary body 28 is rotatably supported by the frame 20
through a bearing means 75.~T~he rotary body 28 itself
constitutes~a motor in which the cylinder 76 serves a
rotor and coils 77 disposed around the cylinder 76 serve
a~s a stator,~`simLlar~to the~example of~Fig. 21.~ Instead
of~s~uch an arrangement for constituting a motor, a
motor may~be used for driving~the rotary body through a
reduction gear mèans.~ A hole 101 for passing the laser
beam is formed~at ~he~center of the upper plate of the
rotary body 28. Th~ Iaser beam 52 from the laser diode
module 22 is reflected~by the mirror 23, and introdu~red
,, into the rotary body 28 through the hole lOl, then
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diffracted by ~he hologram facet 24 to scan an objective.
The scattered light from the objective is xeceived by
the hologram facet 24. With this construction, the area
of the hologram f~cet for receiving the scattered light
is enlarged.
In the example of Fig. 34, the difference from the
example of Fig. 33 resides in that the laser beam 52 is
irradiated to the rotary body 28 from the lower side
thereof~ A mirror 103 is coated at the center of the
lower surface of the hologram facet 24. In both examples
of Figs. 33 and 34, the hologram facet 24 is constructed
so that the spherical scattered light is changed to a
plane wave light and the upper plate 102 of the rotary
body 28 comprises a transparent Fresnel lens for
converging the parallel plane wave scattered light
diffracted by the hologram facet 24. Howéver, instead
of such an arrangement, a self-focusing hologram facet
and a mere transparent upper plate may be used, so that
the scattered beam is directly converged to the position
of the optical detector 29 by the self-focusing hologram
facet.
A furthar embodiment~of the~present invention is
illustrated in~Fig. 35.~ n thls~example, the laser
;beam 52 i5 introduced in~o the rotary body 28 through a
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hollow rotational shaft~105.~An L-shaped pipe 104 is
; installed within the hollow~rotational shaft 105. Two
mirrors 106 and~-107~for~re~fLecting~and~devlating the
laser beam 52~are,~disposed i~ the L-shaped pipé 104.
The hollow shaft~105; may~be~e1ther~integra1~with the
30~;shaft of the~motor~25~or~conn~écted;~to;the~motor shaft
through a reduction~gear means. The L-shaped pipe 104
,in the hollow~shaft does~not rotate.
In~the;abové~mentioDed~embodiments of the~,present
~ invention, the~hologram~may be formed either directly on
;~ ~ 35 the r*tary body~member or on a plate which is attaahed
to the rotary body, to constitute a hologram facet of
rot,ary body.
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