JP2751697B2 - Overhead projector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overhead projector (hereinafter abbreviated as "OHP"), and more particularly to an improvement in an OHP using a spatial light modulator or a light-light converter.

[0002]

2. Description of the Related Art As an OHP using a spatial light modulator, there is, for example, "OHP for plain paper" disclosed in JP-A-3-17615. This OHP is a conventional OH
Paying attention to the fact that P can use only film-transmitted original paper, the contents of the original are written into the liquid crystal light valve by appropriate irradiation and reflection of writing light. The liquid crystal light valve is of an optical writing type and has a configuration in which a reflective layer and a light shielding layer are provided in addition to a photoconductive layer and a liquid crystal layer. When the reading light is applied to the liquid crystal light valve, the liquid crystal light valve undergoes light modulation according to the written contents. The modulated readout light is reflected by the reflection layer and projected on a screen via mirror means. According to this conventional example, it is possible to enlarge and project a plain paper document image onto a screen.

[0003]

On the photoconductive layer side of a spatial light modulator to which writing light from a document is applied,
If the read light for reading the written information leaks, the photoconductive layer reacts due to the leaked read light, causing a decrease in the contrast ratio of the written image. This leakage readout light cannot be made constant even if a reflective layer is provided as in the conventional example. Furthermore, when a readout light with a strong visible range is given to the spatial light modulator in order to obtain a bright and good display image on the screen, the readout light leaking to the photoconductive layer side is further increased, and the display image is increased. Will be further reduced.

In the prior art, a light-shielding layer is separately provided. However, the resolution deteriorates due to the light-shielding film thickness, and the impedance decreases when the light-shielding performance is increased in order to avoid the influence of leakage reading light. This leads to degradation of resolution.

Further, when a liquid crystal of the light valve is of a homogeneous alignment which can be driven at a low voltage and is easy to handle, the wavelength dependence on the readout light increases, and unless the frequency band is extremely limited, The contrast ratio decreases. Then, when the band of the reading light is limited, the luminance of the image on the screen is reduced. In particular, it is very difficult to realize a high-luminance image while maintaining color reproducibility during full-color display.

In addition, the above-mentioned conventional example has a disadvantage that the optical writing type liquid crystal light valve is simply applied to the OHP, and no consideration is given to the convenience and the convenience is not always good.

The present invention focuses on these points.
The first object is to perform image projection with good contrast ratio and resolution. The second purpose is plain paper manuscript,
It is an object of the invention to satisfactorily project various objects such as a transparent manuscript, a book, and a three-dimensional object. A third object is to perform full-color projection with high luminance and good color reproducibility. A fourth object is to improve the convenience of OHP.

[0008]

According to the present invention, there is provided a color separating means for separating writing light containing information to be projected into primary color light, a spatial light modulator to which information for each color obtained by this is written. A color synthesizing means for reading out the information for each color written in this with each corresponding primary color light and synthesizing them to obtain color information, wherein the dielectric mirror of each of the spatial light modulators has a corresponding primary color. It has wavelength selectivity to light, and the light modulating layer uses homeotropically aligned liquid crystal.

According to another aspect of the present invention, there is provided a projection device for irradiating, as the writing light, the light output from the polarizing beam splitter, which is not irradiated to the spatial light modulator, to the projection target. Further, the writing means includes:
A first light source that reflects writing light to a projection target;
A second light source that transmits writing light.

According to another aspect of the invention, the writing means includes first wavelength selection means for outputting the primary color light as writing light in a plane sequence, and the reading means corresponds to the primary color light in synchronization with the wavelength selection means. Is output as readout light in a frame sequential manner.
And wavelength selecting means.

[0011]

According to the present invention, the dielectric mirror of the spatial light modulator has wavelength selectivity, and uses band-limited readout light. Therefore, leakage of read light to the photoconductive layer side is extremely small, and a light-shielding layer is not required.
The contrast ratio and resolution are improved. Further, since the homeotropically aligned liquid crystal is used, the wavelength dependency is small, and particularly in the case of color display, the band of each color can be widened, and the brightness of the projected image is improved. Light that does not enter the spatial light modulator due to the action of the deflection beam splitter of the reading means is used as writing light.

When the projection target is a three-dimensional object, the information of the document is read out by reflection and transmission by two light sources. Further, by means of the wavelength selection means, for example R
An image to be projected is written to the spatial light modulation element in (red), G (green), and B (blue) plane-sequential manner, and the reading is performed at high speed with the corresponding R, G, and B reading light. . If this is observed with the naked eye, a color image will be displayed as a result.

According to the main mode, when the projection target is a three-dimensional object, the focus position is set to a desired position by the focus setting means. Further, by a sensitivity adjusting means provided in the spatial light modulation element, its driving state is set so that the contrast ratio and the like become good,
In the case of a transmissive original, the transmitted light is reflected by the writing light reflecting means to improve the contrast ratio.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First Embodiment First, a first embodiment of the present invention will be described with reference to FIGS. 2, the apparatus main body is largely divided into a projection head 40 and a base 42. The document table 12 is illuminated via the optical system 20 by the writing light output from the writing light source 18. The reflected light from the document table 12 is incident on the image writing side of the spatial light modulator 26 by the action of the optical system 44.

Next, on the image reading side of the spatial light modulator 26, a polarization beam splitter 28 is provided. The readout light output from the readout light source 30 is passed through the band limiting filter 32 and the optical system 34 to the polarization beam splitter 2.
8. Projection optical systems 36 and 58 are provided on the readout light output side of the polarization beam splitter 28, and a screen 38 is disposed in a projection direction by the projection optical systems 36 and 58.

Of these, the optical system 44 on the writing side of the spatial light modulator 26 has a manual focus mechanism 46
Is provided. This manual focus mechanism 46
Is for allowing the user to arbitrarily focus on a desired position, for example, when a three-dimensional object 48 or a book is placed on the document table 12 and projected.

In this embodiment, a dedicated writing light source 50, a mirror 52, an optical system 54,
Fresnel lenses 56 are provided in the base 42, respectively. Further, on the output side of the projection optical system 36, a mirror 58 for projecting a read image is provided.

Next, the spatial light modulator 26 is shown in FIG.
The transparent substrates 26A, 26
A photoconductive layer 26E, a dielectric mirror 26F, and a light modulation layer 26G are laminated in that order between the B transparent electrodes 26C and 26D. Note that no light-shielding layer is provided. The writing light is applied to the spatial light modulator 26 as shown by the arrow FA.
, And the readout light enters the spatial light modulator 26 as shown by the arrow FB and is output as shown by the arrow FC. A driving power supply 26H is connected between the transparent electrodes 26C and 26D.

Of these, as the photoconductive layer 26E,
For example, a-Si (amorphous silicon), a-Si
H (hydrogenated amorphous silicon), CdSe, CdS
Are used. The dielectric mirror 26F is made of Si, Si
It is constituted by alternately stacking, for example, about 17 layers of O ₂ , TiO _2, etc., and acts as a mirror only for readout light in a certain limited frequency band (for example, 400 to 630 nm). Then, as shown in FIG. 1B, the transmission amount (arrow FD) of the band-limited incident readout light (arrow FB) is 10 ⁻⁴ (hereinafter referred to as “density 4”).
The dielectric mirror 26F is designed as follows.

As the light modulating layer 26G, for example, a nematic liquid crystal having homeotropic alignment (vertical alignment) having low wavelength dependency is used. This homeotropically-aligned liquid crystal is characterized in that the intensity of transmitted light is slightly changed due to a change in the wavelength of incident light, and the threshold voltage of the change is relatively high. A sensitivity adjusting device 26R is connected to the spatial light modulation element 26 as described above, and the driving voltage and frequency of the spatial light modulation element 26 determine the writing conditions,
It is appropriately changed according to display conditions.

Next, the band limiting filter 32 limits the band of the read light output from the read light source 30 to, for example, 400 to 630 nm in accordance with the characteristics of the dielectric mirror 26F of the spatial light modulator 26. It is for.
Each optical system includes a plurality of optical elements as needed, and a focusing mechanism is provided as needed (not shown).

Next, the operation of the embodiment constructed as described above will be described. The original to be projected is a platen 12
Put on top. The original includes a writing light source 18 and an optical system 20.
The writing light is irradiated by the action of. And manuscript 1
The light reflected by 6 enters the spatial light modulator 26 by the action of the optical system 44, and the image information of the document is written.

Next, the spatial light modulator 26 on which the image information has been written as described above is read out in a band-limited manner by the action of the read-out light source 30, the band-limiting filter 32, the optical system 34, and the polarization beam splitter 28. Light enters. This read light is transmitted to the light modulating layer 2 of the spatial light modulating element 26.
The light enters 6G, undergoes intensity modulation corresponding to the written image information, and is reflected by the dielectric mirror 26F.

In this case, as described above, homeotropically aligned liquid crystal is used as the light modulation layer 26G. Therefore, a change in transmitted light intensity due to a change in the wavelength of the read light is small, and a high contrast ratio can be easily obtained. Further, since the threshold voltage of the change is relatively high, the allowable range for the leakage light is relatively large.

Further, the band limiting filter 3
2, the band is limited according to the characteristics of the dielectric mirror 26F. Therefore, the readout light is satisfactorily reflected by the dielectric mirror 26F and output, and leakage of the readout light to the photoconductive layer 26E side is satisfactorily reduced. Further, by forming the dielectric mirror 26F with wavelength selectivity, the dielectric mirror 26F itself can be formed very thin, and a reduction in resolution and contrast ratio can be prevented.

Next, the readout light output from the spatial light modulator 26 passes through the polarization beam splitter 28, passes through the projection optical system 36, is reflected by the mirror 58 and is projected on the screen 38, thereby reading out. Image information is projected. Writing light source 18 as in this case
When the document is illuminated by the, it is possible to project a document instruction by the conduct rod.

When the three-dimensional object 48 is projected in the first embodiment, the focus position is appropriately set by the manual focus mechanism 46. Thereby, an image of a desired position of the three-dimensional object 48 can be projected on the screen 38. In the case of a transmissive original, the illumination device in the base 42 is used, and the writing light output from the writing light source 50 is reflected by the mirror 52, the optical system 54, and the Fresnel lens 56.
Is incident on the transmission type original. The light transmitted through the document enters the spatial light modulator 26 by the action of the optical system 44, and the image information of the document is written.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the polarization beam splitter 28 of the reading light output from the reading light source 30 is used as the writing light of the image information to the spatial light modulator 26.
Is used. The P component light is reflected by the mirror 62 and is filtered by the filter 64 and the optical system 2.
0 is projected onto the document table 12. The filter 6
Reference numeral 4 is provided when the amount of P component light is strong as writing light, and a polarizing plate or the like is used. Further, the amount of light can be adjusted by rotating the polarizing plate.

According to this embodiment, the P component of the readout light that has been wasted in the above embodiment is effectively used.
Further, according to the present embodiment, the convex lens or the Fresnel lens cover 66 is provided near the document on the document table 12. As a result, the light output from the document side is efficiently condensed and captured by the optical system 24 with little image distortion. A suitable cover 68 is provided around the document table 12 as needed (arrow FE). As a result, unnecessary light that is noticeable to a viewer of the screen 38 is cut.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, color projection of a document is performed. In the figure, the writing light output from the writing light source 18 and reflected by the original is incident on the three-color separation optical system 80 via the optical system 24. Then, R (red) and G of the three-color separation optical system 80
(Green) and B (blue) on the output side, respectively.
R, 82G, and 82B are arranged respectively. A three-color separation / synthesis optical system 84 is provided on the image reading side of these spatial light modulators 82R, 82G and 82B, and the polarization beam splitter 28 is provided on the input / output side of the combined reading light.
Is arranged.

Of the above, each light source 1 is set so that the writing light and the reading light include white light or light of each band of R, G and B.
8, 30 are configured. The three-color separation optical system 80 has a function of separating incident writing light into three primary colors of R, G, and B and outputting the separated light. The three-color separation / synthesis optical system 84
Decomposes the S-polarized light component incident from the polarization beam splitter 28 into three primary colors of R, G, and B, and
R, 82G, and 82B are output to the polarization beam splitter 28 side, respectively, and the R, G, and B lights input thereto are combined and output to the polarization beam splitter 28 side.

Next, the spatial light modulators 82R, 82G, 8
Although the basic configuration of 2B is as described above, the photoconductive layers may be formed so as to have sensitivity in the bands of the R, G, and B writing lights. For example, a-Si, CdS
e, CdS, etc. are used. In addition, a homeotropic alignment layer is similarly used as the light modulation layer. Further, each dielectric mirror has an incident read light wavelength (for example, R = 590 to 640 nm, G = 490 to 600 n).
m, B = 400 to 500 nm), and the light has a density of 4 at these wavelengths.
It is designed to be above.

Next, the operation of the third embodiment will be described. The original on the platen 12 is a writing light source 18.
Illuminated by the writing light. The writing light reflected by the manuscript 12 enters the three-color separation optical system 80 via the optical system 24, where it is separated into R, G, and B primary color lights, and the spatial light modulators 82R, 82G, and 82B. Respectively. This means that the R, G, and B images have been written.

Next, of the readout light output from the readout light source 30, S reflected by the polarization beam splitter 28
The polarized light component enters the three-color separation / synthesis optical system 84 and receives R,
The spatial light modulators 82R, 82G,
82G and 82B. This gives R,
G, B images are read out, and R, G,
Each light of B enters the three-color separation / synthesis optical system 84 again and is synthesized. The read light after the synthesis is projected on the screen 38 by the action of the polarization beam splitter 28, the projection optical system 36, and the mirror 58, whereby the read image is projected.

According to this embodiment, the spatial light modulator 82
Liquid crystals having homeotropic alignment are used as the light modulation layers of R, 82G, and 82B. For this reason, the wavelength dependency is greatly reduced, so that the wavelength band of each of the R, G, and B lights can be widened, and a bright color image can be obtained. Further, since the concentration of each dielectric mirror is 4 or more, a high contrast ratio can be obtained, and
Since a light-shielding layer is not required and the film thickness can be reduced, a high-resolution projected image can be obtained. In the above embodiment, three spatial light modulation elements are provided independently for each of R, G, and B. However, one element is divided into regions, and a photoconductive layer and a dielectric mirror are optimally designed for each color. It may be driven.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, color projection of a document is performed in the same manner as in the above-described embodiment, and is an improvement of the first embodiment in FIG. In the drawing, wavelength selection filters 100 and 102 are provided between the writing light source 18 for reflection and the optical system 20 and between the writing light source 50 for transmission and the mirror 52, respectively. Further, a wavelength selection filter 104 is also provided between the reading light source 30 and the optical system 34.
Is provided.

These wavelength selection filters 100 and 10
2 and 104 are configured as shown in FIG. 3B, for example, and are configured to rotate synchronously in the direction of arrow FF. As a result, the color of the reading light is selected according to the color of the writing light applied to the projection target. For example, the wavelength selection filter 10
When the three-dimensional object 48 is irradiated with the R light as the writing light according to 0 and 102, the R light is similarly selected as the reading light in the wavelength selection filter 104 of the reading light source 30. The same applies to G and B.

Next, the operation of the fourth embodiment will be described. The three-dimensional object 48 to be projected is R, G, B by the action of the wavelength selection filter 100 or 102.
Are irradiated in a plane-sequential manner. For this reason, the R, G, and B images are sequentially written to the spatial light modulator 26. On the other hand, these images are read out by readout light output from the readout light source 30, and at this time, light having the wavelength selected by the wavelength selection filter 104 enters the spatial light modulator 26.

In this case, the selection of the filter in the wavelength selection filter 100 or 102 on the writing light side is as follows.
The operation is performed such that the same color is obtained in synchronization with the selection of the filter in the wavelength selection filter 104 on the readout light side. Therefore, for example, the image of R is
When the data is written in the, the reading is performed by the light of R. The same applies to G and B. When such an operation is performed at high speed in the order of R, G, and B, the image on the screen 38 is observed by the naked eye as a color image. As described above, according to the present embodiment, a color image can be easily displayed by writing and reading an image in a plane sequence for each color.

<Other Embodiments> The present invention is not limited to the above-described embodiments, but includes, for example, the following. (1) In any of the embodiments, each optical system may be configured using various optical elements, and a focus, particularly an autofocus mechanism, may be appropriately provided as necessary.

(2) A modulation material having a memory property may be used as the light modulation layer of the spatial light modulation element. Examples of the light modulation material having a memory property include an electro-optic crystal, PLZT, and a ferroelectric liquid crystal. In this way, the image information once written is stored until it is rewritten, and the projection can be continued. If the illumination of the writing light is turned off when the writing of the image information to the spatial light modulator is completed, the power consumption can be reduced. Further, when the writing light is irradiated onto the document surface from above, the light becomes noticeable to a screen viewer. However, if the illumination of the writing light is turned off after the writing of the image information, the image on the screen becomes more visible.

(3) The above embodiments can be combined with each other. For example, the third embodiment of FIG.
The invention using the P-polarized light component of the polarization beam splitter as described above as writing light may be applied. (4) Next, in the fourth embodiment, each of the light sources 18, 3
In the case where each of the monochromatic light sources R, G, and B is integrated into one (for example, an RGB white laser, etc.), light emission of each monochromatic light source can be performed by switching. Are the wavelength selection filters 100 and 10 described above.
2 and 104 become unnecessary. At this time, if the switching of the monochromatic light source in each light source is performed in synchronization, R, R
G and B planes can be used.

[0043]

As described above, the overhead projector according to the present invention has the following effects. (1) The dielectric mirror of the spatial light modulator is designed by limiting the band, and a homeotropically aligned liquid crystal is used as the light modulating layer, and the wavelength band of the reading light is adjusted to the band characteristic of the dielectric mirror. Since this is made compatible, it is possible to improve the contrast ratio, the brightness, and the resolution of projected images of various objects such as a normal original, a transparent original, a book, and a three-dimensional object.

(2) In particular, when a homeotropically aligned liquid crystal is used as the light modulating layer when performing color display by color separation and color synthesis, the wavelength band of each primary color light is widened due to its wavelength dependence. Thus, the brightness of the projected image can be increased. (3) In addition, since the split light by the polarization beam splitter for guiding the read light to the spatial light modulator is used as the write light, the configuration of the device is simplified, the light is effectively used, and the power consumption is reduced. There is an effect that can be achieved.

(4) Further, by providing the focus means, it becomes possible to cope with the projection of a book or a three-dimensional object.
By providing the reading means below the document table, the projection head can be made compact. By providing two reading light sources, it is possible to deal with both reflective and transmissive documents.
Convenience can be improved, for example, the sensitivity of the spatial light modulator can be adjusted to an optimum state by the sensitivity adjusting means. (5) The wavelength selecting means operating in synchronization with the writing means and the reading means are respectively provided, and the light projection target is irradiated with the primary color light to write the image of each primary color on the spatial light modulation element in a plane-sequential manner. Since the image is read out and displayed by the color reading light, a color image can be displayed well.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a spatial light modulation element in the present embodiment.

FIG. 2 is a configuration diagram showing a first embodiment of the present invention.

FIG. 3 is a configuration diagram showing a second embodiment of the present invention.

FIG. 4 is a configuration diagram showing a third embodiment of the present invention.

FIG. 5 is a configuration diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Body 12 ... Original plate 14 ... Cover 14A ... Facing 16 ... Original 18 ... Writing light source 50 ... Writing light source 18A ... Light control device 20,24,34,44,54 ... Optical system 22,52,58,60,70 , 72 ... Mirror 26, 82R, 82G, 82B ... Spatial light modulator 26E ... Photoconductive layer 26F ... Dielectric mirror 26G ... Light modulation layer 26H ... Driving power supply 26R ... Sensitivity controller 28 ... Polarization beam splitter 30 ... Readout light source 32, 64 ... band-limiting filter 36 ... projection optical system 38 ... screen 40 ... projection head 42 ... base 46 ... manual focus mechanism 48 ... three-dimensional object 56 ... Fresnel lens 62 ... mirror 66 ... Fresnel lens cover 68 ... cover 74 ... drive Circuit 76 Flat light source 78 Dimming device 80 Three-color separation optical system 84 Three-color separation and synthesis optics 100,102 ... wavelength filter 104 ... wavelength filter FA, FB, FC, FD, FE, FF ... arrow

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuji Suzuki 3-12-12 Moriyacho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Within (72) Inventor Fusiko Tatsumi 3-12 Moriyacho, Kanagawa-ku, Yokohama, Kanagawa Address: Victor Company of Japan, Ltd. (72) Inventor Tatsusaku Takahashi 3-12 Moriyacho, Kanagawa-ku, Yokohama, Kanagawa Prefecture, Japan Victor Company of Japan, Ltd. (56) References JP-A-3-17615 (JP, A) JP-A-3 JP-18815 (JP, A) JP-A-3-83021 (JP, A) JP-A-2-47072 (JP, A) JP-A-61-30167 (JP, A) JP-A-61-210338 (JP, A) ) Actually open 1-85723 (JP, U) Actually open sho 59-89337 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/13 505 G02F 1/135 G03B 21 / 132 G02F 1/1337 G02F 1/1335

Claims (4)

(57) [Claims] 1. An overhead projector for writing information to be projected onto a spatial light modulation element in which a photoconductive layer, a dielectric mirror, and a light modulation layer are stacked, reading the written information, and projecting the information. Color separation means for separating writing light containing information into primary color light, a spatial light modulation element to which information for each color obtained by this is written, and information for each color written in the color light corresponding to the primary color light And a color synthesizing means for synthesizing them to obtain color information, wherein the dielectric mirror of each of the spatial light modulators has wavelength selectivity for the corresponding primary color light, and the light modulating layer is An overhead projector using homeotropically aligned liquid crystal. 2. A method of irradiating a projection target with writing light to write information on a spatial light modulator, and irradiating a read beam output from a reading light source with a polarizing beam splitter to write information written on the spatial light modulator. An overhead projector for reading and projecting, comprising: a projection unit for irradiating, as the writing light, a light output from the polarization beam splitter, which is not irradiated to the spatial light modulator, to the projection target. projector. 3. A writing means irradiates a projection object with writing light to write information on the spatial light modulator, and a reading means irradiates read light to read and project information written on the spatial light modulator. In the overhead projector, the writing unit includes a first light source that reflects the writing light to the projection target and a second light source that transmits the writing light. 4. A writing means irradiates writing light to a projection target to write information on the spatial light modulator, and a reading means irradiates read light to read and write information written on the spatial light modulator. In the overhead projector, the writing unit includes a first wavelength selection unit that outputs the primary color light as writing light in a plane sequence, and the reading unit synchronously synchronizes the primary color light with the wavelength selection unit in a plane sequence. An overhead projector comprising: a second wavelength selection unit that outputs the read light.