U5005264951A
`.
`5,264,951
`[11] Patent Number:
`[19]
`UnltEd States Patent
`
`Takanashi et a1.
`[45] Date of Patent:
`Nov. 23, 1993
`
`[54] SPATIAL LIGHT MODULATOR SYSTEM
`[75]
`‘lnventors:
`ltauo Takanaalti,Kamakura;Sbintaro
`Nakagaki, Miura; lcltlro Negtshi,
`Yokosuka; Ryuaaku Takaltashi,
`Yokosuka; Tetattli Suzuki, Yokosuka;
`Ftdiko Tatautni, Yokohama; Keiichi
`Maeno, Yokosuka, all of Japan
`Victor Company of Japan, Ltd.,
`Yokohama, Japan
`
`[73] Assignee:
`
`[21] Appl. No.: 980.121
`
`[22] Filed:
`
`Nov. 23, 1992
`
`[63]
`
`Related US. Application Data
`Continuation of Ser. No. 681,938, Apr. 8, 1991, aban-
`doned.
`.
`
`Foreign Application Priority om
`[30]
`Apr. 9. 1990 [JP]
`Japan .................................... 2-93524
`Jun. 19, 1990 [JP]
`Japan .................................. 2-160797
`
`[51]
`
`int. 01.5 ...................... GOZF 1/03; GOZF 1/1347;
`(3021= 1/135; 60313 21/14
`[52] US. c1. ........................................ 359/53; 359/72;
`359/250, 359/256; 359/259
`[58] Field of Search .................. 350/173, 342; 353/20,
`353/31, 33, 34; 359/71, 72, 247, 634. 637. 638,
`64, 53, 294,250, 256, 259
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`...... 350/173
`
`1,319,292 10/1919 Kunz ............
`...... 350/173
`1.897.874
`2/1933 Tuttle et al.
`.
`
`4
`.. 350/173
`2.096.425 10/1937 Dixon et a1.
`.
`...... 350/173
`2.737.076 3/1956 Rock. Jr. ......
`
`2.971.051
`2/1961 Back .....
`.. 350/173
`
`7/1967 Back ............... 350/173
`3.333.053
`
`......................... 350/242 ,
`4.191.456
`3/1980 Hong et al.
`
`2.33.53 11/1983 l’lummer~ ............................... 359/64
`4:461:42 51:34 2133“,...“
`”33333;
`
`9/1985 Bonk ........
`4,541,691
`359/64
`
`4,650,286 3/1987 Koda et al
`.......
`. (350/342
`359/64
`4,770,500 9/1988 Kalmanash et a1.
`4,867,536 9/1989 Pidsosny et a1.
`..
`359/64
`
`4,933,751
`6/1990 Shinonaga et a
`. 350/173
`4,968,120 11/1990 Depp et a1. .............. 359/64
`. 350/173
`4,981,352
`1/1991 Tejima et al.
`5.039.209
`8/1991 Takanashi et a1.
`359/72
`
`5.054.892 10/1991 Takanashi et a1.
`359/72
`5,130,826 7/1992 Takanashi et al. .................... 359/72
`
`FOREIGN PATENT DOCUMENTS
`
`1/1990 Japan .
`63113304
`Primary Examiner—Martin Lerner
`Attorney, Agent. or Firm—Michael N. Meller
`
`ABSTRACT
`[57]
`There is provided an optical system for a spatial light
`modulator. The system comprises a light source for
`emitting an unpolarized light, a separator for separating
`a first linearly polarized light having a specified plane of
`polarization from the unpolarized light and polarizer for
`rotating the plane of polarization of the first linearly
`polarized light at a specified angle different from the
`specified angle to obtain a second linearly polarized
`light, wherein the second linearly polarized light
`is
`adopted as a reading light. Also provided is a method of
`photomodulation. comprising the steps of separating a
`light in the region of a specified wavelength from an
`unpolarized light, separating a first linearly polarized
`light having a specified plane of polarization from the
`light and obtaining a second linearly polarized light by
`rotating the plane of polarization of the first linearly
`' polarized light at a specified angle.
`
`'
`
`5 Claims, 12 Dratrlng Sheets
`
`SLMr
`
`
`WL
`
`Ee
`
`6
`
`PLZ.
`
`ll
`
`ECBi
`
`”RU
`--—--RLo
`
`XLNX-1003
`
`

`

`U.S. Patent
`
`Nov. 23, 1993
`
`Sheet 1 of 12
`
`5,264,951
`
`I
`FIG.
`PRIOR ART
`
` FIG. 3
`
`PRIOR ART
`
`PCL(|) mgr"?
`ETI
`/SLMr
`
`
`
`( RL)
`
`2
`
`XLNX-1003
`
`-
`
`

`

`US. Patent
`
`Nov. 23, 1993
`
`Sheet 2 of 12
`
`5,264,951
`
`FIG. 4A
`
` An=ne,-nc
`
`
` TRANSMISSION
`INTENSITY
`
`3
`
`-
`
`XLNX-1003
`
`

`

`US. Patent
`
`Nov. 23, 1993 ‘
`
`Sheet 3 of i2
`
`5,264,951
`
`FIG. 6
`Es
`
`/’ 9
`
`liil ECBr
`
`6
`
`7
`
`LCb
`
`IO
`
`FIG. 8
`
`_Q Ee
`Es Q
`I; as
`
`PLI
`
`'
`
`
`\NL
`
`SLMr
`
`ECBt
`
`PL?
`
`“—————‘RLI
`——————a-RLo
`
`4
`
`XLNX-1003
`
`

`

`US. Patent
`
`Nov. 23, 1993
`
`Sheet 4 of 12
`
`5,264,951
`
`RLO
`
`RU
`
`PLI
`
`ECB?
`
`PLZ
`
`SLM?
`
`
`
`PLO
`
`ECB'!
`
`PLb
`
`
`
`5
`
`XLNX-1003
`
`

`

`US. Patent
`
`Nov. 23,1993
`
`Sheet 5 of 12 I
`
`5,264,951
`
`FIG.
`
`IIA‘
`
`
`_‘I% RLO
`
`FIG. IIB
`
`ECBr
`
`6
`
`XLNX-1003
`
`

`

`US. Patent
`
`Nov. 23, 1993
`
`Sheet 6 of 12
`
`5,264,951
`
`FIG.
`
`I?
`
`WLZ PBS!
`
`PBSZ
`
`RLI
`\OJ
`LS
`
`RLo
`
`RLo
`
`7
`
`XLNX-1003
`
`

`

`US. Patent
`
`‘Nov.23, 1993
`
`Sheet7 of 12
`
`'
`
`5,264,951
`
` 8
`
`XLNX-1003
`
`

`

`US. Patent
`
`Nov. 23, 1993
`
`Sheet 8 of 12
`
`5,264,951
`
`FIG.
`
`I6
`
`Es
`
`Ee
`
`‘
`scan
`
`P'
`
`CA
`
`-
`
`.
`
`SLMrr
`
`WLr—u-
`PLr
`
`_
`
`SLMrg
`
`WLg—c—
`Es
`
`PLb
`WLb—-
`
`SLMrb
`
`Es
`
`Ee
`
`.
`
`PLq
`
`scam
`
`
`
`
`scam
`
`Pb
`
`@JVLS
`
`28
`
`.J ,
`
`§
`mg
`° 5
`g;
`.2
`u.)
`mg
`
`.
`
`PLI
`
`L3
`3
`é RL: gg
`a 2
`o 9
`L522
`LIJ
`N § :71
`Ea;
`
`PJL
`
`“"
`RLo
`
`PL3
`
`RLo
`
`PJL
`
`
`
`9
`
`XLNX-1003
`
`

`

`US. Patent
`
`Nov. 23, 1993
`
`Sheet 9 of 12
`
`5,264,951
`
`FIG. I8
`
`SLMrr
`
`SLMrg
`
`SLMrb
`
`
`
`
`1O
`
`XLNX-1003
`
`

`

`US. Patent
`
`Nov. 23, 1993
`
`Sheet 10 of 12
`
`. 5,264,951
`
`
`
`FIG. 2l'
`
`
`
`6LIGHTTRANSMITTANCE
`
`O
`
`1 1
`
`XLNX-1003
`
`

`

`US. Patent
`
`Nov. 23, 1993
`
`Sheet 11 of 12
`
`5,264,951
`
`FIG. 22
`
`
`
`LIGHTTRANSMITTANCE
`
`
`
`12
`
`XLNX-1003
`
`

`

`US. Patent
`
`Nov. 23, 1993
`
`Sheet 12 of 12
`
`5,264,951
`
`
`
`
`
`13
`
`' XLNX-1003
`
`

`

`1
`
`SPATIAL LIGHT MODULATOR SYSTEM
`
`5,264,951
`
`This application is a continuation. of application Ser.
`No. 681938. filed Apr.'8. 1991, now abandoned.
`BACKGROUND OF THE INVENTION
`
`5
`
`This invention relates to a spatial light modulator and
`a display unit in which the spatial light modulator is
`applied.
`The spatial light modulator in which the spatial light
`modulator element operating in the birefringent mode is
`used, is used as the component of the display unit for
`example.
`PROBLEM TO BE SOLVED BY THE
`INVENTION
`
`lO
`
`[5
`
`20
`
`25
`
`The spatial light modulator element which is used as
`the component of the spatial light modulator and oper-
`ates in the birefringent mode, includes, for example, the
`reflex spatial light modulator element SLMr having the
`configuration as illustrated in FIG. 1 or FIG. 2 or trans-
`mission spatial light modulator element SLMt having
`the configuration as illustrated in FIG. 3.
`The modulator element SLMr illustrated in FIG. 1
`and FIG. 2 has the electrodes Etl and Et2, the photo-
`conductive layer component PCL (herein after called
`“component PCL“), the dielectric mirror DML reflect-
`ing the read light, the photo-modulation layer compo-
`nent PML (hereinafter called “component PML") (for
`example, the photo-modulation layer such as the single
`crystal of lithium niobate or the liquid crystal layer, a
`high polymer-liquid crystal composite film, the lead '
`lanthanum zirconate titanate (PLZT) and others). Fur-
`ther. WI. is the write light to write the optical image as
`the charge in the modulator element SLMr, and RI. is
`the read light used for reading out the charge image
`formed in the modulator element.
`The modulator element SLMr in FIG. 1 has further
`the shield film SM. The shield film SM acts so that the
`write light WI. does not reach the read side and the
`read light RI. does not reach the write side.
`The electrode Etl described above is transparent for
`the write light WI. and the electrode Et2 is transparent
`for the read light RL.
`In the modulator element SLMr illustrated in FIG. 1
`and FIG. 2, when the field is applied between both ends
`of the component PCL by connecting the electrodes
`Etl and Et2 with the power source E and the write
`light WL is sent from the electrode Etl side, the write
`light WI. sent to the modulator element passes through
`the electrode Etl and reaches the component PCL.
`Since the electric resistance value of the component
`PCI. changes according to the intensity distribution of
`write light WL reaching it, in the modulator element 55
`SLMr in FIG. 1, the charge image of the intensity distri-
`bution corresponding to the intensity distribution of
`write light WI. reaching the component PCI. is pro-
`duced on the boundary surface between the component
`PC]. and the shield film SM.
`Further, in the modulator element SLMr in FIG. 2,
`the charge image of the intensity distribution corre-
`sponding to the intensity distribution of write light WL
`reaching the component PCL is produced on the
`boundary surface between the component PCL and the
`dielectric mirror DML.
`When the read light RI. of a certain intensity is inci-
`dent from the electrode Et2 side in the modulator ele-
`
`2
`ment SLMr in which the charge image corresponding
`to the intensity distribution of the write light WL is
`produced as described above. the read light RL passes
`through the component PM]. before being reflected by
`the dielectric mirror, passes through the component
`PML again and is emitted from the electrode Et2.
`Said read light RL is emitted from the electrode Et2
`side as the read light NJ in the condition that the plane
`of polarization of read light (linearly polarized light) is
`changed according to said charge image.
`Therefore, said read light RLr is changed in its condi—
`tion of read according to the charge distribution of
`charge formed on the boundary surface between the
`‘ component PCI. and the shield film SM in FIG. 1 or
`between the component PCI. and the dielectric mirror
`DML in FIG. 2.
`Next, the following (I) and (2) can be used as the
`transmission spatial
`light modulator element SLMt
`which operates in the birefringent mode as illustrated in
`FIG. 3. (l) The transmission spatial light modulator
`element in which the photoconductive layer component
`PCLI {the photoconductive layer component, which is
`insensitive to the read light RL in practical use, for
`example, 850 (BinSiOzo) and organic photosensitive
`materials (PVK, photosensitive azo-material phthalocy-
`anine, etc.)} which is sensitive at least to the light in the
`range of wave length of write light WI. and is not sensi-
`tive to the light in the range of wave length of read light
`RL is used to form it. (2) The transmission spatial light
`modulator element in which the photomodulation layer
`component which has a property of memory (liquid
`crystal, PLZT) is used to form it.
`.
`At first, when the modulator element SLMt illus- .
`trated in FIG. 3 is formed as an element which has the
`configuration of said (I), it is formed on the substrate
`BPl by laminating the electrode fit], the component
`PCLl which is sensitive at least to the light in the wave-
`length range of write light WI. and is not sensitive to
`the light in the wavelength range of read light RL, the
`component PM]. in which the condition of birefrin-
`gence changes according to the intensity distribution of
`electric field and the condition of plane of polarization
`of read light RL can be changed, the electrode Et2 and
`the substrate 8P2.
`Said electrode Etl is formed to be transparent at least
`to the write light WI. and said electrode Et2 is formed
`to be transparent at least to the read light RL.
`Therefore, in said modulator element SLMt having
`the configuration of (1), when its electrodes Etl and Et2
`are connected to the power supply E and the write light
`WL in the wavelength range to which the component
`PCL: is sensitive is incident from the electrode Etl side.
`the write light WI. passes through the electrode Etl
`and reaches the component PCLI.
`The charge image with the intensity distribution cor-
`responding to the intensity distribution of the write light
`WI. which reaches the component PCLi is produced on
`the boundary surface between the component PCL1 and
`the component PMLI because the electric resistance of
`the component PCL] is changed according to the inten-
`sity distribution of write light WI. which reaches the
`component PCLi.
`When the read light RI. of a certain intensity in the
`wavelength range to which the component PCL; is
`insensitive is incident from the electrode Etl side of
`modulator element SLMt in which the charge image is
`formed corresponding to the intensity distribution of
`the write light WI. as described above, the read light
`
`35
`
`45
`
`60
`
`65
`
`14
`
`XLNX-1003
`
`

`

`5,264,951
`
`5
`
`10
`
`4
`formed by the read light, which is outputted from the
`modulator element SLMr and the modulator element
`SLMt, has a lower contrast ratio.
`To solve the above-mentioned problem, light of sin-
`gle wavelength, such as laser beams can be used as the
`read light RL, but laser beams of large output are neces-
`sary for the read light RL to get a bright reproduced
`image, so that this solution is difficult to adopt.
`Therefore, in the image display unit, the read light of
`narrow wavelength range was obtained by sending the
`light radiated from the usual light source of large output
`to the optical filter of absorbing filter etc. such as di-
`_ chroic filter and colored glass. But in said optical filter
`conventionally used. when it is formed having a narrow
`15
`passband, its reflection and transmission factors at the
`central wavelength of its passband are smaller than that
`of wide passband and the light source which can radiate
`light of very large output is required to generate the
`read light possible to display the reproduced image of
`high luminance, resulting in the low efficiency in use of
`light.
`Next, when the electromagnetic radiation beam (its
`.typical example is ‘light‘ hereinafter) is irradiated to
`anisotropic materials (particularly smectic and nematic
`structures), such as liquid crystal, which are provided in
`the photo-modulation layer component. two kinds of
`transmission light are obtained by birefringence. Of
`these two kinds of light, the light having a velocity
`(refractive index) independent of propagating direction
`and which obeys Snell's law for ordinary isotropic me-
`dium, is called “ordinary ray". The light having a ve-
`locity (refractive index) which is different depending
`upon the propagating direction and which does not -
`obey Snell’s law is‘ called “extraordinary ray". The
`ordinary ray and the extraordinary ray are separated for
`uniaxial crystal and the vibration direction of electric
`flux density vector is perpendicular to the principal
`plane (plane including propagating direction and optic
`axis) for the ordinary ray and parallel for the extraordi-
`nary ray.
`Here, the birefringence An is given by
`
`3
`RL passes from the electrode Etl through the compo-
`nent PCL; and the component PML to the electrode
`Et2, and includes the information corresponding to the
`intensity distribution of electric field which is applied to
`the component PML by the photoelectric effect, and is
`emitted from the electrode £12 side, because the refrac-
`tive index of said component PML is changed by the
`photoelectric effect according to the electric field.
`The component PCL] is insensitive to the read light
`RI. and the photoconductive effectis not generated on
`the component PCL] even if the read light RI. passes
`through the component PCL]. Therefore. the read light
`RI. does not distrub the charge image in the boundary
`between the component PCL; and the component
`PML.
`Next, when the modulator element SLMt illustrated
`in FIG. 3 is formed by using the photo-modulation layer
`component PML) having a property of memory as the
`photo-modulation material layer component which is
`used for its configuration as in above mentioned (2), it is
`formed on the substrate BPI by laminating the elec-
`trode Etl, the component PCL. the component PML;
`which can store the intensity distribution of applied
`electric field as the form of the change of birefringence
`(for example, birefringent type liquid crystal, birefrin-
`gent type PLZT), the electrode Etz and the substrate
`BP2.
`In the modulator element SLMr having the configu-
`ration as in (2), the write period by the write light and
`the read period by the read light are deemed to be serial
`on the time axis, then the write and read operations are
`carried out.
`In the modulator element SLMt having the configu-
`ration of (2), when its electrode Etl and Et2 are con-
`nected to the power supply E and the write light WL is
`incident from the electrode Etl side, the write light WI.
`passes through the electrode Etl and reaches the com-
`ponent PCL.
`The charge image with the intensity distribution cor-
`responding to the intensity distribution of the write light
`WL which reaches the component PCL is produced on
`the boundary surface between the component PCL and
`the component PMLI because the electric resistance of
`the component PCL is changed according to the inten-
`sity distribution of write light WI. which reaches the
`component PCL.
`When the electric field by said charge image is ap-
`plied to the component PML; having a property of
`memory. the component PML] stores the intensity dis-
`tribution of electric field applied to it as a form of 50
`change of birefringence. The content of the storage is
`held even if said write light disappears.
`Next. when the read light of a certain intensity is
`incident from the electrode Etl side of modulator ele-
`merit SLMt, the read light RL is transmitted from the
`electrode Etl, through the component PCL and the
`component PML. which stores the charge image corre-
`sponding to the intensity distribution of write light WL
`as the change of condition of birefringence and to the
`electrode Et2. Thus, the read light includes the informa-
`tion stored in the component PML; and is emitted from
`the electrode Et2 side.
`The degree of modulation which is given to the read
`light by the component PML used in the modulator
`elements SLMr and SLMt described in reference to
`FIGS. 1—3 is changed according to the wavelength of
`read light. Therefore. when the read light is not in a
`narrow wavelength range,
`the reproduced image
`
`20
`
`25
`
`30
`
`35
`
`45
`
`55
`
`65
`
`An=ny—nx
`
`(l)
`
`where nx and ny are the refractive indexes in x and y
`directions respectively and the angle 0 formed by axes
`of ordinary and extraordinary rays in the anisotropic
`medium is determined according to the birefringence
`An. Further, the phase difference, which is determined
`by the angle 0, the modulation layer thickness d of
`medium (see FIG. 4(A)) and the wavelength 7t of light,
`is produced. This relation is called ”retardation R"
`(R=An.d/A). The change of 0 (that is, phase shift) is
`determined by this retardation R and the change is sin2
`(7R). Here, n is the director of modulation layer.
`In the liquid crystal having a birefringent property,
`the birefringence depends upon the electric field (drive
`voltage) applied thereto, and the transmission intensity
`of light (transmittance repeatedly increases and de-
`creases with increased drive voltage). Consequently,
`controlling the applied voltage permits changing the
`intensity of light passing through the liquid crystal film
`and now researches are increasing on the display, re-
`cord, rerecord, etc. of image and character information.
`In the electromagnetic radiation beam modulation
`method the electromagnetic radiation beam is modu-
`lated by using the phase difference between the ordi-
`nary ray and the extraordinary ray which are emitted
`
`15
`
`XLNX-1003
`
`

`

`5,264,951
`
`IO
`
`5
`through the anisotropic medium such as said liquid
`crystal when either or both sides of input (incident) and
`output (emitted) of electromagnetic radiation beam is a
`wide band, the dependence of modulation component
`on wavelength such that the operating point is moved
`by the wavelength A because the modulation (factor) is
`changed according to the wavelength A of incident light
`was a fundamental problem.
`The relation between the applied voltage and the
`transmission intensity of birefringent
`liquid crystal
`(membrane) is described below with reference to FIG.
`5. The curve a (continuous line) and the curve b (dashed
`line) in FIG. 5 are electro-magnetic radiation beams of
`mutually difi‘erent wavelength. The transmission inten-
`sity of curve a is maximum at the drive voltage Va and
`minimum at the drive voltage Vb. Namely, the curve a
`is “bright (maximum transmission intensity)" at
`the
`drive voltage Va and “dark (minimum transmission
`intensity)“ at Vb in the case of application to the display
`unit. When the wavelength of curve b also exists, how-
`ever, the curve a does not become “dark" at Vb and
`becomes “bright" at a different wavelength due to the
`influence of curve b. Therefore, even if black is required
`to be displayed. sufficient black is not obtained on the
`display unit.
`SUMMARY OF THE INVENTION
`
`6
`FIG. 4 is a principle drawing showing the relation
`between the director of modulation layer and the polar-
`izer;
`FIG. 5 is a characteristics diagram showing the rela-
`tion between the drive voltage applied to the birefrin-
`gent material and the transmission intensity;
`FIG. 6 is a side sectional view showing an example of
`configuration of the electrically controlled birefringent
`liquid crystal element of reflector type;
`.
`FIG. 7 is a side sectional view showing an example of
`configuration of the electrically controlled birefringent
`liquid crystal element of transmission type;
`FIG. 8 is a block diagram to explain the forming and
`' operation principles of the spatial light modulator ac-
`15
`cording to this invention, which includes the reflex
`spatial light modulator element operating in the bire-
`fringent mode;
`FIG. 9 is a block diagram to explain the forming and
`operation principles of the spatial light modulator ac
`cording to this invention. which includes the transmis-
`sion spatial light modulator element operating in the
`birefringent mode;
`FIG. 10 is a block diagram to explain the forming and
`operation principles of a known wavelength selection
`filter which is formed by using the electrically con-
`trolled birefringent liquid crystal element and the polar~
`izer;
`
`2O
`
`25
`
`This invention provides an optical system for an opti-
`cal device (a spatial light modulator) in which an optical
`image is written by a writing light as a charge image by
`photoelectric effect and which reproduces the image as
`a linearly polarized light having the image by rotating a
`plane of polarization of a reading light at a first specified
`angle by photomodulation.
`The optical system comprises a light source for emit-
`ting an unpolarized light, separation means for separat-
`ing a first linearly polarized light having a specified
`plane of polarization from the unpolarized light and
`polarization means for rotating the plane of polarization
`of the first linearly polarized light at a second specified
`angle different from the first specified angle to obtain a
`second linearly polarized light, wherein the second
`linearly polarized light is adopted as the reading light.
`Thereby, the reproduced image of high contrast ratio
`can be obtained by using the read light obtained in the
`high efficiency in use of light source.
`Furthermore. this invention provides a method of
`photomodulation. comprising the steps of separating an
`electro-magnetic radiation beam in the region of a speci-
`fied wavelength from an unpolarized electro-rnagnetic
`radiation beam, separating a first linearly polarized elec-
`tro-magnetic radiation beam having a specified plane of
`polarization from the electro-magnetic radiation beam
`and obtaining a second linearly polarized electro-rnag-
`netic radiation beam by rotating the plane of polariza.
`tion of the first linearly polarized electromagnetic radi-
`ation beam at a specified angle.
`As described above. according to the method of
`photomodulation. the phenomenon that the output is
`different according to the wavelength will be reduced.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIGS. 1 and 2 are side sectional views showing exam-
`ples of configuration of conventional reflex spatial light
`modulator element;
`FIG. 3 is a side sectional view showing an example of
`the configuration of transmission spatial light modulator
`element;
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`FIGS. 11A and 1113 are diagrams of an embodiment
`of a spatial light modulator constructed in accordance
`with the principles of the present invention using a
`single polarization beam splitter;
`FIG. 12 is a diagram of an embodiment of a spatial
`light modulator constructed in accordance with the _
`principles of the present invention and using two polar-
`ization splitters;
`FIG. 13 is a diagram of a further embodiment of a
`spatial light modulator constructed in accordance with
`the principles of the present invention;
`FIG. 1‘ is a diagram of an embodiment of a spatial
`light modulator constructed in accordance with the
`principle of the present
`invention and using a three
`color separation prism;
`FIG. 15 is a diagram of a further embodiment of a
`spatial light modulator constructed in accordance with
`the principles of the present invention and using a three
`color separation prism in the form of a dichroic prism;
`FIG. 16 is a diagram of a further embodiment of a
`spatial light modulator constructed in accordance with
`the principles of the present invention and using a three
`color separation optical system having a dichroic prism
`and additional prisms for the correction of optical path
`length.
`FIG. 17 is a diagram of a further embodiment of a
`spatial light modulator constructed in accordance with
`the principles of the present invention and using trans-
`mission spatial light modulator elements.
`_
`FIG. 18 is a diagram of a further embodiment of the
`present invention using three spatial light modulators
`having the configuration of the embodiment illustrated
`in FIGS. 11A and 113.
`FIG. 19 is a diagram of a further embodiment of the
`present invention using three spatial light modulators
`having the configuration of the embodiment illustrated
`in FIG. 13;
`FIG. 20 is a diagram of a further embodiment of the
`present invention using three sets of spatial light modu-
`lators having the configuration of the embodiment illus-
`trated in FIG. 12;
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`FIG. 21 is a characteristics diagram showing the
`relation of drive voltage versus transmission intensity
`wherein the dependence of modulation component it-
`self on wavelength is reduced;
`FIG. 22 is a characteristics diagram wherein the
`phase difference between the wavelengths. which are
`obtained by controlling the wavelength band,
`is con-
`trolled to one half wavelength or less;
`FIG. 23 is an are oblique side view showing funda-
`mentally a different embodiment of the electromagnetic
`radiation beam modulator according to this invention;
`FIG. 24 is an oblique side view similar to the embodi-
`ment of FIG. 23 except that the wavelength selection
`filter is located at the outlet side of the modulator.
`FIG. 25 is an oblique side view similar to that of FIG.
`23 except that two wavelength selection filters are used,
`one at the inlet side and one at the outlet side of the
`modulator; and
`FIG. 26 is a principle drawing of the display unit
`which is formed by using the reflex optical modulator
`component (electromagnetic radiation beam modula-
`tor).
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`This invention will now be described in detail on
`reference to the accompanying drawings.
`Throughout the drawings, like reference numerals
`are used to designate like or equivalent elements for the
`sake of simplicity of explanation.
`In each drawing, SLMr is a reflex spatial light modu-
`lator element operating in the birefringent mode (reflex
`light-light conversion element) SLMr and for example,
`is the configuration is described with reference to
`FIGS. 1 and 2 can be used as this reflex spatial light
`modulator element SLMr.
`The drawing symbol of reflex spatial light modulator
`element used in the figure has added thereto further
`suffixes r, g and b in order to show the following dis-
`tinction of modulator element SLMr; that is, when the
`optical image which is written in the modulator element
`SLMr by the write light WL is a red image obtained by
`the three color separation of the optical image of dis-
`play object, the suffix r is added to the modulator ele-
`ment as SLMrr. Further when the optical image which
`is written in the modulator element SLMr by the write
`light WI. is a green image obtained by the three color
`separation of the optical image of display object, the
`suffix g is added to the modulator element as SLMr.
`When the optical image which is written in the modula-
`tor element SLMr by the write light W]. is a blue image
`obtained by the three color separation of the optical
`image of display object, the suffix b is added to the
`modulator element SLMrb. Hereinafter, when the mod-
`ulation element is described without distinction of the
`modulator element SLMrr. SLMrg and SLMrb, the
`modulator element SLMr is used.
`Further,
`in each drawing. SLMt is a transmission
`spatial light modulator element operating in the bire-
`fringent mode (transmission light-light conversion ele-
`ment) SLMt and for example the configuration de-
`scribed with reference to FIG. 3 can be used as this
`modulator element SLMt.
`light
`The drawing symbol of transmission spatial
`modulator element used in the figure has added thereto
`further suffixes r. g and b in order to show the following
`distinction of modulator element SLMt. That is, when
`the optical image which is written in the modulator
`
`8
`element SLMt by the write light WL is a red image
`obtained by the three-color separation of the optical
`image of display object, the suffix r is added to the
`modulator element as SLMtr. When the optical image
`which is written in the modulator element SLMt by the
`write light WL is a green image obtained by the three-
`color separation of the optical image of display object,
`the suffix g is added to the modulator element as
`SLMtg. When the optical image which is written in the
`modulator element SLMt by the write light WL is a
`blue image obtained by the three color separation of the
`optical image of display object, the suffix b is added to
`the modulator element as SLMtb. Hereinafter, when
`the modulator element is described without distinction
`of the modulator element SLMtr. SLMtg and SLMtb,
`the modulator element SLMt is used.
`Next, the reflex electrically controlled birefringent
`liquid crystal element ECBr is described. The configu~
`ration illustrated in FIG. 6 for example, which is formed
`by laminating the transparent electrode 7, the liquid
`crystal layer LCb operating in the birefringent mode.
`the reflection film 10 and a substrate 9 on a substrate 6
`can be used as this liquid crystal element ECBr. In FIG.
`6, the power supply Es is connected to the transparent
`electrode 7 and the reflection film 10. Said reflection
`film 10 may be formed of aluminum evaporation film for
`example and the reflection film 10 is also used for the
`electrode.
`The drawing symbol of reflex electrically controlled
`birefringent liquid crystal element used in the figure has
`added there to additional suffixes r, g and b in order to
`show the following distinction of liquid crystal ECBr.
`For the liquid crystal element to which the read light of '
`a red optical image of display object is supplied, the
`suffix r is added as ECBrr. For the liquid crystal ele-
`ment to which the read light of a green optical image of
`display object
`is supplied,
`the suffix g is added as
`ECBrg. For the liquid crystal element to which the read
`light of a blue optical image of display object is sup-
`plied, the suffix b is added as ECBrb. Hereinafter, when
`the liquid crystal element is described without distinc-
`tion of the liquid crystal element ECBrr, ECBrg and
`ECBrb. the liquid crystal element ECBr is used.
`Further, the transmission double refraction field con-
`trol liquid crystal element ECBt is described. The con-
`figuration illustrated in FIG. 7 for example, which is
`formed by laminating the transparent electrode 7, the
`liquid crystal layer LCb operating in the birefringent
`mode, the transparent electrode 8 and the substrate 9 on
`the substrate 6 can be used as this liquid crystal element
`ECBt. In FIG. 7 the power supply Be is connected to
`the transparent electrodes 7 and 8.
`The drawing symbol of liquid crystal element ECBt
`used in the figure has added thereto additional suffixes r,
`g and b in order to show the following distinction of
`liquid crystal ECBt. For the liquid crystal element to
`which the read light of a red optical image of display
`object is supplied, the suffix r is added as ECBtr, fur-
`ther, for the liquid crystal element to which the read
`light of a green optical image of display object is sup-
`plied, the suffix g is added as ECBtg. For the liquid
`crystal element to which the read light of a blue optical
`image of display object is supplied, the suffix b is added
`as ECBtb. Hereinafter. when the spatial light modulator
`element is described without distinction of liquid crystal
`element ECBtr, ECBtg and ECBtb, the liquid crystal
`element ECBt is used.
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`In the spatial light modulator according to this inven-
`tion, as described about FIGS. 8 and 9, the wavelength
`selection filter is formed by using the modulator ele-
`ment SLMr or SLMt besides the polarizer PL and the
`liquid crystal element ECBt, or by using the polarizer
`PL and the liquid crystal element ECBr as shown in the
`embodiment described below.
`FIGS. 11A and 118 show an embodiment of the
`spatial light modulator according to this invention. In
`10 FIGS. 11A and “8, PBS is the polarization beam Split-
`ter, and when the read light RLi of unpolarized light
`inputted from a light source LS to the spatial light mod-
`, ulator is incident on the polariz