JPH05113576A - Overhead projector - Google Patents

Abstract

PURPOSE:To improve the contrast ratio, the resolution, the brightness and the facilitation of a projection image with respect to the various kinds of objects such as a plain-paper original, a transmitted original, a book or a stereoscopic substance in an overhead projector using a space light modulation element. CONSTITUTION:Light reflected on the original 16 is made incident on the space light modulation element 26 provided with a dielectric mirror whose band is restricted and liquid crystal which is homeotropic-oriented by the actions of a mirror 22 and an optical system 24. Then, the image information thereof is written. Besides, read-out light whose band is restricted is made incident on the element 26 by the actions of a light source for read-out 30, a band restricting filter 32, an optical system 34 and a polarizing beam splitter 28 and excellently reflected on the dielectric mirror. Then, the image information is read out.

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 improvement of 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 Japanese Patent Laid-Open No. 3-17615. This OHP is a conventional OH
Paying attention to the fact that P can only use film transparent original paper, the content of the original is written in the liquid crystal light valve by irradiation and reflection of appropriate writing light. The liquid crystal light valve is of an optical writing type and has a structure having a reflective layer and a light shielding layer in addition to the photoconductive layer and the liquid crystal layer. When the liquid crystal light valve is irradiated with the reading light, the liquid crystal light valve undergoes optical modulation according to the contents of writing. The modulated read light is reflected by the reflective layer and projected on the screen via the mirror means. According to this conventional example, it is possible to enlarge and project a plain paper original image on the screen.

[0003]

By the way, on the photoconductive layer side of the spatial light modulator to which the writing light from the original is given,
When the reading light for reading the written information leaks, the leaked reading light causes the photoconductive layer to react, thereby lowering the contrast ratio of the written image. The leaked read light cannot be inevitable even if a reflective layer is provided as in the conventional example. Furthermore, if the read light in the visible range is given to the spatial light modulator in order to obtain a bright and good display image on the screen, the read light leaking to the photoconductive layer side will increase more and more, and the display image Will be further reduced.

In the conventional example, a light-shielding layer is additionally provided, but the light-shielding film thickness deteriorates the resolution, and if the light-shielding performance is increased to avoid the influence of leaked read light, the impedance becomes smaller. However, the resolution will be deteriorated.

Further, when the liquid crystal of the light valve is a homogeneous alignment liquid crystal that can be driven at a low voltage and is easy to handle, the wavelength dependence on the read light becomes large, and the frequency band must be extremely limited. The contrast ratio is reduced. Then, if the band of the reading light is limited, then the brightness of the image on the screen is lowered. In particular, it is very difficult to realize a high-luminance image while maintaining color reproducibility during full-color display.

In addition, in the above-mentioned conventional example, the optical writing type liquid crystal light valve is simply applied to the OHP, no consideration is given to the convenience, and it is not necessarily convenient.

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

[0008]

One of the main inventions is an overhead projector for writing information to be projected onto a spatial light modulator and reading the written information for projection, wherein the dielectric mirror is band-limited. Has a wavelength selectivity for reflecting the read-out light, the light modulation layer uses a liquid crystal of homeotropic alignment, and the read-out light for reading the information of the projection target has a wavelength selectivity of the dielectric mirror. It is characterized by having a corresponding band.

Another main invention is, in the overhead projector, color separation means for respectively separating writing light including information on the projection target into primary color light, and spatial light in which information for each color obtained thereby is written. The spatial light modulator includes a modulator and a color synthesizing unit for reading the information for each color written in the corresponding primary color light and synthesizing them to obtain color information. It has a wavelength selectivity with respect to the primary color light, and the light modulation layer is characterized by using liquid crystal of homeotropic alignment.

Another main invention is to irradiate a projection object with writing light to write information in a spatial light modulator, and to irradiate a reading light output from a reading light source with a polarizing beam splitter to a spatial light modulator. In an overhead projector for reading and projecting written information, a projection means is provided for irradiating, as the writing light, a projection target of light output from the polarization beam splitter that is not irradiated on the spatial light modulator. Is characterized by.

According to still another aspect of the present invention, there are provided focus setting means for irradiation of writing light, first and second light sources for illuminating a projection target with reflection and transmission, writing light reflecting means near a document table, and spatial light modulator. Sensitivity adjusting means, optical means for reflecting the writing light reflected by the reflecting original to enter the spatial light modulator, condensing optical means near the original table, and light adjusting means for the writing means are provided as necessary. The means for reading out the image information from the spatial light modulator is arranged below the document table. According to another main invention, the writing means and the reading means are respectively provided with wavelength selecting means which operate in synchronization with each other.

[0012]

According to the present invention, the dielectric mirror of the spatial light modulator has wavelength selectivity, and band-limited read light is used. Therefore, the leakage of the read light to the photoconductive layer side is very small, and since the light shielding layer is not required,
The contrast ratio and resolution are improved. Further, since the liquid crystal of homeotropic alignment is used, the wavelength dependence 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.
Further, the light not incident on the spatial light modulator is used as the writing light by the action of the deflecting beam splitter of the reading means.

When the projection target is a three-dimensional object, the focus setting means sets the focus position to the desired position, and the information of the document is reflected by the two light sources.
It is read by either transmission. Further, by the sensitivity adjusting means provided in the spatial light modulator, 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. According to still another aspect of the invention, the reading means is arranged below the document table, and the projection head is made compact. Further, by the wavelength selecting means, for example, the image of the projection target is written in the spatial light modulator in the frame order of R (red), G (green), and B (blue), and the corresponding read light of R, G, B is obtained. Therefore, the reading of them is performed at high speed. When this is observed with the naked eye, a color image is displayed as a result.

[0014]

Embodiments of the OHP according to the present invention will be described below with reference to the accompanying drawings. <First Embodiment> First, referring to FIGS. 1 to 3,
A first embodiment of the present invention will be described. FIG. 1 shows a main configuration of the first embodiment as a perspective view, and FIG. 2 shows it as a side view.

In these figures, a document table 12 is provided on the upper surface of a body 10 which is entirely box-shaped. The document table 12 is provided with a cover 14,
As a result, the document 16 on the document table 12 is pressed.

Next, in the document table 12, the writing light output from the writing light source 18 provided on the bottom side of the body 10 is illuminated from inside the body 10 by the optical system 20. The writing light source 18 is provided with a dimmer 18A. In addition, the reflected light from the document table 12 includes a mirror 22 and an optical system 24 provided at a lower portion of the body 10.
By the action of, the light is incident on the image writing side of the spatial light modulator 26. The spatial light modulator 26 is provided with a sensitivity adjusting device 26R.

Next, a polarization beam splitter 28 is provided on the image reading side of the spatial light modulator 26. The reading light source 30 is arranged above the polarization beam splitter 28, and the reading light output from the reading light source 30 enters the polarization beam splitter 28 via the band limiting filter 32 and the optical system 34. A projection optical system 36 is provided on the side of the body 10 on the output side of the reading beam of the polarization beam splitter 28, and a screen 38 is arranged in the projection direction by the projection optical system 36.

Of the above-mentioned parts, the back side of the cover 14, that is, the side 14A facing the document table 12 is configured to have light reflectivity. As the writing light source 18, for example, various ones such as a halogen lamp and an LED may be used, but a necessary one is selected according to the sensitivity of the photoconductive layer of the spatial light modulation element 26 described later. Also, the dimmer 18A
Is for adjusting the brightness and color of the writing light source 18 as desired.

Next, the spatial light modulator 26 is shown in FIG.
The transparent substrates 26A, 26 have a structure as shown in FIG.
A photoconductive layer 26E, a dielectric mirror 26F, and a light modulation layer 26G are laminated in this order between the transparent electrodes 26C and 26D of B. No light-shielding layer is provided. The writing light is the spatial light modulator 26 as indicated by the arrow FA.
The read light is incident on the spatial light modulator 26 as indicated by the arrow FB and is output as indicated by the arrow FC. A driving power source 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
Etc. 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 the read light in a certain limited frequency band (for example, 400 to 630 nm). Then, as shown in FIG. 3B, 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 dependence is used. This homeotropically aligned liquid crystal is characterized in that the change in transmitted light intensity due to a change in the wavelength of incident light is slight 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 drive voltage and frequency of the spatial light modulation element 26 are used for writing conditions,
It is adapted to be 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.
Further, in this embodiment, as shown in FIG. 2, the spatial light modulator 26 and the screen 38 are arranged substantially in parallel,
The arrangement is such that the readout light is obliquely incident on the spatial light modulator 26 at an angle. Each optical system is composed of a plurality of optical elements as needed, and a focus mechanism is provided as needed (not shown).

Next, the operation of the present embodiment constructed as above will be described. The original 16 to be projected is placed on the original table 12. At this time, the document 16 is pressed by the cover 14. The original 16 has a writing light source 18,
The writing light is emitted by the action of the optical system 20. The reflected light from the original 16 is reflected by the mirror 22 and the optical system 24.
Is incident on the spatial light modulator 26 by the action of
Image information is written.

At this time, the dimming device 18A irradiates the writing light corresponding to the density and the contrast ratio of the original 16. In addition, when a three-dimensional object is projected instead of the original 16, it is possible to change how the shadow is cast by the light control device 18A. Further, unnecessary light that becomes noise from the outside when the original 16 is small is satisfactorily cut by the cover 14. Further, when the original 16 is a transmissive type, the writing light that has passed through the original 16 is reflected favorably by the cover 14, and the image writing process is favorably performed. Furthermore, the spatial light modulator 2
The sensitivity adjustment by the sensitivity adjusting device 26R of No. 6 is also performed as necessary.

By the actions of the cover 14, the light control device 18A, and the sensitivity control device 26R, the spatial light modulator 26 is operated.
The writing of the image information of the original 16 to the document is performed well. Next, the spatial light modulator 26 in which the image information is written as described above is incident with the read light whose band is limited by the actions of the read light source 30, the band limiting filter 32, the optical system 34, and the polarization beam splitter 28. To do. The read light is used as the light modulation layer 2 of the spatial light modulation element 26.
It is incident on 6G, undergoes intensity modulation corresponding to the written image information, and is reflected by the dielectric mirror 26F.

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

Further, the band-pass filter 3 is used for the read light.
2 limits the band in accordance with the characteristics of the dielectric mirror 26F. Therefore, the read light is satisfactorily reflected by the dielectric mirror 26F and output, and leakage of the read light to the photoconductive layer 26E side is satisfactorily reduced. Further, by configuring the dielectric mirror 26F with wavelength selectivity, the dielectric mirror 26F itself can be made very thin, and the resolution and the contrast ratio are prevented from being lowered.

Next, the readout light output from the spatial light modulator 26 passes through the polarization beam splitter 28 and is projected onto the screen 38 via the projection optical system 36, and the image information read out by this is displayed. Will be displayed. At this time, as described above, the spatial light modulator 2
6 and the screen 38 are arranged in parallel, and the read light obliquely enters the spatial light modulation element 26. Therefore, even if the screen 38 is arranged above the front surface of the projection optical system 36, distortion of Fewer images can be obtained. Further, since there is no projection head, there is an advantage that the image on the screen 38 is easy to see.

According to the apparatus prototyped for this embodiment,
As described above, by setting the density of the dielectric mirror 26F to 4 or more, the contrast ratio on the screen 38 can be set to 100: 1 or more as compared with the conventional case.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. It should be noted that the same reference numerals are used for the components that are the same as or correspond to those in the above-described first embodiment (the same applies to the following embodiments). The second embodiment is an example of a type having a projection head.

In FIG. 4, the main body of the apparatus is the projection head 4
It is largely divided into 0 and the base 42. Inside the projection head 40, the respective parts inside the body 10 of FIG. 2 are housed. Of these, the optical system 4 on the writing side of the spatial light modulator 26
4, a manual focus mechanism 46 is provided. The manual focus mechanism 46 is used for the document table 12
This is for allowing the focus to be arbitrarily adjusted to a desired position when the three-dimensional object 48 or a book is placed on the projection and the projection is performed.

Further, in the present embodiment, a dedicated writing light source 50, mirror 52, 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 read image projection mirror 58 is provided.

The operation of the second embodiment is basically the same as that of the first embodiment, but when the three-dimensional object 48 is projected, the focus position is appropriately set by the manual focus mechanism 46. .. As a result, the three-dimensional object 48
The image at the desired position of 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 transmitted by the action of the mirror 52, the optical system 54, and the Fresnel lens 56. Incident on. Then, 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.

The read-out light from the spatial light modulator 26 is transmitted through the projection optical system 36, reflected by the mirror 58 and projected onto the screen 38, whereby the read-out image information is projected. Further, when the writing light source 18 illuminates the original, it is possible to project the original instruction by the conductor rod.

<Third Embodiment> Next, a third embodiment of the present invention will be described with reference to FIG. The third embodiment is similar to the first embodiment, but the reflected writing light from the original on the original table 12 is reflected by the mirror 60 and enters the spatial light modulator 26. .. The use of mirror 60 allows the overall device to be constructed low. Further, even if the projection head is omitted, it is possible to project a document instruction with a contact rod or the like.

<Fourth Embodiment> Next, a fourth embodiment of the present invention will be described with reference to FIG. In the fourth embodiment, as the writing light of the image information to the spatial light modulator 26, the P component light of the reading light output from the reading light source 30 that travels straight through the polarization beam splitter 28 is used. The P component light is reflected by the mirror 62 and projected onto the document table 12 via the filter 64 and the optical system 20. The filter 64 is provided when the amount of P component light is strong as writing light, and a polarizing plate or the like is used. Also, the light amount can be adjusted by rotating the polarizing plate.

According to this embodiment, the P component of the read light, which wasted in the previous embodiment, is effectively utilized.
Further, according to this embodiment, a convex lens or Fresnel lens cover 66 is provided near the original on the original table 12. As a result, the light output from the document side is efficiently collected and taken into the optical system 24 in a state where the image distortion is small. An appropriate cover 68 is provided around the document table 12 as needed (arrow FE). As a result, unnecessary light that is noticeable to the viewer of the screen 38 is cut.

<Fifth Embodiment> Next, a fifth embodiment of the present invention will be described with reference to FIG. In the fifth embodiment, the reading light source 30, the band limiting filter 32, and the optical system 34 are housed in the base 42 from the projection head 40. The read light is reflected by the mirrors 70 and 72 and enters the polarization beam splitter 28. Also,
A drive circuit 74 is also housed in the base 42, and a flat light source 76 such as a fluorescent tube or an EL used in a liquid crystal display device and the like is transmitted through the lower part of the document table 12 together with the light control device 78. It is provided for mold documents.

In the above-described embodiment, the reading light source 30 and the like are provided in the projection head 40, but the light source is generally large and heavy. Therefore, by utilizing the mirrors 70 and 72, the read light source 30 and the like, together with the drive circuit 74 and the like, can be housed in the base 42, and the projection head 40 can be made smaller and lighter.

Further, according to the present embodiment, when a three-dimensional object or a small original is projected, the flat light source 76 illuminates the lower portion of the original table 12 under appropriate light adjustment by the light adjusting device 78. Then, the brightness of the background of a three-dimensional object or the like changes, and it is possible to project an attractive image.

<Sixth Embodiment> Next, a sixth embodiment of the present invention will be described with reference to FIG. In this embodiment, color projection of a document is performed. In the drawing, 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. Spatial light modulators 82R, 82G, and 82B are disposed on the R (red), G (green), and B (blue) output sides of the three-color separation optical system 80, respectively. These spatial light modulators 82R, 82
On the image reading side of G and 82B, a three-color separation / synthesis optical system 8
4 is provided, and a polarization beam splitter 28 is disposed on the input / output side of the combined read light.

Of the above, each light source 1 is such that the writing light and the reading light include white light or light in each of the R, G, and B bands.
8 and 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 them. Also, a three-color separation / combination optical system 84
Is a spatial light modulator 82 that decomposes the S-polarized component incident from the polarization beam splitter 28 into three primary colors of R, G, and B.
It has a function of outputting to R, 82G, and 82B, respectively, and combining the lights of R, G, and B inputted from them to output to the polarization beam splitter 28 side.

Next, the spatial light modulators 82R, 82G, 8
The basic configuration of 2B is as described above, but those photoconductive layers may be formed so as to have sensitivity in the R, G, and B writing light bands, respectively. For example, a-Si, CdS
e, CdS or the like is used. Further, as the light modulation layer, one having homeotropic alignment is similarly used. 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 has a wavelength selectivity of 4 at any of these wavelengths and a concentration of 4 to light.
It is designed to be above.

Next, the operation of the sixth embodiment as described above will be described. A document on the platen 12 is written by a writing light source 18
Is illuminated by the writing light. The writing light reflected by the original 12 enters the three-color separation optical system 80 through the optical system 24, and is decomposed into the R, G, and B primary color lights there, and the spatial light modulators 82R, 82G, and 82B. Incident on each. As a result, each of the R, G, and B images has been written.

Next, of the read light output from the read light source 30, the S reflected by the polarization beam splitter 28 is reflected.
The polarization component is incident on the three-color separation / combination optical system 84 and enters R,
The spatial light modulator 82R, which is decomposed into G and B primary color lights,
It is incident on 82G and 82B, respectively. This allows R,
The G and B images are read out, and the R, G and
The respective lights of B enter the three-color separation / combination optical system 84 again and are combined. The combined read light is projected onto 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 with homeotropic alignment are used as the R, 82G, and 82B light modulation layers. For this reason, the wavelength dependence is greatly reduced, and the wavelength band of each of the R, G, and B lights can be widened, and a bright color image can be obtained. Moreover, since the density of each dielectric mirror is 4 or more, a high contrast ratio can be obtained, and
Since a light-shielding layer is unnecessary and the film thickness can be made thin, a high-resolution projected image can be obtained. In the above embodiment, three spatial light modulators are provided independently for each of R, G and B, but one device is divided into regions to optimally design the photoconductive layer and the dielectric mirror for each color. It may be driven.

<Seventh Embodiment> Next, a seventh embodiment of the present invention will be described with reference to FIG. In this embodiment, color projection of a document is performed similarly to the above embodiment, and is an improvement of the second embodiment of FIG. In the figure, the writing light source 18 for reflection and the optical system 2 are shown.
Wavelength selection filters 100 and 102 are provided between 0 and 0, and between the writing light source 50 for transmission and the mirror 52, respectively. The wavelength selection filter 104 is also provided between the read light source 30 and the optical system 34.

These wavelength selection filters 100, 10
The reference numerals 2 and 104 have, for example, the configuration shown in FIG. 7B, and both 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 with which the projection target is irradiated. For example, the wavelength selection filter 10
When the three-dimensional object 48 is irradiated with the R light as the writing light by 0 and 102, the R light is also 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 seventh embodiment will be described. On the three-dimensional object 48 which is the projection target, R, G, B is applied to the three-dimensional object 48 by the action of the wavelength selection filter 100 or 102.
The respective lights are radiated in a frame sequential manner. Therefore, the R, G, and B images are sequentially written in the spatial light modulator 26. On the other hand, these images are read by the reading light output from the reading light source 30, and at this time, the light of 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
The same color is synchronized with the selection of the filter in the wavelength selection filter 104 on the reading light side. Therefore, for example, an image of R is displayed on the spatial light modulator 26.
When written in, the light is read out with R light. The same applies to G and B. When such an operation is performed at high speed in the order of R, G, B, the image on the screen 38 is visually observed as a color image. As described above, according to the present exemplary embodiment, a color image can be easily displayed by writing and reading images in a frame-sequential manner for each color.

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

(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 electro-optic crystal, PLZT, and ferroelectric liquid crystal. In this way, the image information once written is saved until it is rewritten, and the projection can be continued. If 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 applied to the original surface from above, the light is conspicuous to the screen viewer. However, if the illumination of the writing light is turned off after writing the image information, the image on the screen becomes easier to see.

(3) It is also optional to combine the above embodiments. For example, in the sixth embodiment of FIG.
The invention using the P-polarized light component of the polarization beam splitter shown in FIG. 7 as the writing light or the invention using the writing illumination means for the transmissive original shown in FIG. 7 to perform background illumination may be applied. (4) Next, in the seventh embodiment, each light source 18, 3
0, 50 has a configuration in which R, G, B monochromatic light sources are combined into one (for example, an RGB white laser), and it is possible to emit light for each monochromatic light source by switching. Is the wavelength selection filter 100, 10 described above.
2, 104 are unnecessary. At this time, if the switching of the monochromatic light source in each light source is performed in synchronization, R,
It can be G, B frame sequential.

[0054]

As described above, the overhead projector according to the present invention has the following effects. (1) Designing a dielectric mirror of a spatial light modulation element by performing band limitation, using homeotropically aligned liquid crystal as the light modulation layer, and setting the wavelength band of read light to the band characteristic of the dielectric mirror. Since they are made compatible, it is possible to improve the contrast ratio, the brightness, and the resolution of the projected images of various objects such as ordinary documents, transparent documents, books, and three-dimensional objects.

(2) In particular, when a liquid crystal having homeotropic alignment is used as a light modulation layer when color display is performed by color separation and color combination, the wavelength band of each primary color light should be wide due to its wavelength dependence. Therefore, the brightness of the projected image can be increased. (3) Further, since the separated light by the polarization beam splitter that guides the read light to the spatial light modulator is used as the write light, the device configuration is simplified, and the light is effectively used and the power consumption is reduced. There is an effect that can be achieved.

(4) Further, by providing a focus means, it is possible to correspond to the projection of books, three-dimensional objects, etc.
The projection head can be made compact by providing the reading means under the original table, and both reflective and transmissive originals can be supported by providing two reading light sources.
It is possible to improve the convenience such that the sensitivity of the spatial light modulator can be adjusted to an optimum state by the sensitivity adjusting unit. (5) The writing means and the reading means are respectively provided with the wavelength selecting means that operate in synchronization with each other, and the light projection target is irradiated with the primary color light to write the images of the respective primary colors in the spatial light modulator in the frame sequential manner. Since color light is read out and displayed, a color image can be displayed well.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part showing a first embodiment of an OHP according to the present invention.

FIG. 2 is a configuration diagram of a main part showing a first embodiment of the OHP according to the present invention.

FIG. 3 is an explanatory diagram showing a spatial light modulator according to the example.

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

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

FIG. 6 is a configuration diagram showing a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram showing a fifth embodiment of the present invention.

FIG. 8 is a configuration diagram showing a sixth embodiment of the present invention.

FIG. 9 is a configuration diagram showing a seventh embodiment of the present invention.

[Explanation of symbols]

10 ... Body, 12 ... Manuscript stand, 14 ... Cover, 14A ...
Face-to-face (writing light reflecting means), 16 ... Original, 18 ... Writing light source (writing means, first light source), 50 ... Writing light source (writing means, second light source), 18A ... Light control device, 2
0, 24, 34, 44, 54 ... Optical system, 22, 52, 5
8, 60, 70, 72 ... Mirror, 26, 82R, 82
G, 82B ... Spatial light modulator, 26E ... Photoconductive layer, 26
F ... Dielectric mirror, 26G ... Optical modulation layer, 26H ... Driving power supply, 26R ... Sensitivity adjusting device (sensitivity adjusting means), 28 ...
Polarizing beam splitter, 30 ... Readout light source (readout means), 32, 64 ... Band limiting filter, 36 ... Projection optical system, 38 ... Screen, 40 ... Projection head, 42 ... Base, 46 ... Manual focus mechanism (focus setting means) ), 48 ... Three-dimensional object, 56 ... Fresnel lens, 62 ...
Mirror (projection means), 66 ... Fresnel lens cover, 6
8 ... Cover, 74 ... Drive circuit, 76 ... Flat light source (second
Light source, 78 ... Dimmer, 80 ... Three-color separation optical system (color separation means), 84 ... Three-color separation / combination optical system (color combination means), 100, 102 ... Wavelength selection filter (first wavelength selection) Means), 104 ... Wavelength selection filter (second wavelength selection means), FA, FB, FC, FD, FE, FF ... Arrows.

[Procedure amendment]

[Submission date] March 3, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Another main invention is, in the overhead projector, color separation means for respectively separating writing light including information on the projection target into primary color light, and spatial light in which information for each color obtained thereby is written. The dielectric mirror of each of the spatial light modulators is provided with a modulator and a color synthesizer for reading the information for each color written in the corresponding primary color light and synthesizing them to obtain color information. It has a wavelength selectivity with respect to the corresponding primary color light, and is characterized in that the light modulation layer uses a liquid crystal of homeotropic alignment.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

According to the present invention, the dielectric mirror of the spatial light modulator has wavelength selectivity, and band-limited read light is used. Therefore, the leakage of the read light to the photoconductive layer side is very small, and since the light shielding layer is not required,
The contrast ratio and resolution are improved. Further, since the liquid crystal of homeotropic alignment is used, the wavelength dependence 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. Further, the light not incident on the spatial light modulator is used as the writing light by the action of the deflecting beam splitter of the reading means.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ichiro Negishi Ichiro Negishi 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Japan Victor Company of Japan, Ltd. (72) Tetsuji Suzuki 3--12 Moriya-cho, Kanagawa-ku, Yokohama Address: Victor Company of Japan, Ltd. (72) Inventor: Reiji Tatsumi, 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Pref. Address 12 Victor Company of Japan, Ltd.

Claims (12)

[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 laminated, and reading the written information to project the information. Has a wavelength selectivity that reflects band-limited read light, the light modulation layer uses a liquid crystal having homeotropic alignment, and the read light for reading the information of the projection target is the wavelength of the dielectric mirror. An overhead projector having a band corresponding to selectivity. 2. An overhead projector for writing information of a projection target into a spatial light modulation element in which a photoconductive layer, a dielectric mirror, and a light modulation layer are laminated, and reading the written information to project the information. Color separation means for separating the writing light containing information into primary color light, a spatial light modulator in which the information for each color obtained by this is written, and the corresponding primary color light for the information for each color written therein And a color synthesizing means for synthesizing them to obtain color information, the dielectric mirror of each spatial modulation element has wavelength selectivity with respect to the corresponding primary color light, and the light modulation layer is homeomorphic. An overhead projector characterized by using liquid crystal of tropic alignment. 3. The projection light is irradiated with writing light to write information in the spatial light modulation element, and the reading light output from the reading light source is irradiated by the polarization beam splitter to read information written in the spatial light modulation element. In an overhead projector for reading and projecting, an overhead comprising projection means for irradiating, as the writing light, the light output from the polarization beam splitter that is not irradiated on the spatial light modulator as the writing light. projector. 4. The writing means irradiates the projection object with the writing light to write the information in the spatial light modulation element, and the reading means irradiates the reading light with the reading light to read and project the information written in the spatial light modulation element. In the overhead projector, the writing unit has a focus setting unit for irradiating writing light onto a projection target. 5. The writing means irradiates the projection object with the writing light to write the information in the spatial light modulation element, and the reading means irradiates the reading light with the reading light to read and project the information written in the spatial light modulation element. In the overhead projector, the reading means is arranged below a document table. 6. The writing means irradiates the projection target with writing light to write information in the spatial light modulation element, and the reading means irradiates the reading light with projection light to read and project the information written in the spatial light modulation element. In the overhead projector, the writing means includes a first light source that reflects writing light with respect to a projection target and a second light source that transmits writing light. 7. The writing means irradiates the projection target with writing light to write information in the spatial light modulation element, and the reading means irradiates reading light to irradiate and projects the information written in the spatial light modulation element. In the overhead projector, the document projector is provided with writing light reflecting means for reflecting the writing light transmitted through the projection target. 8. The writing means irradiates the projection object with the writing light to write information in the spatial light modulator, and the reading means irradiates the reading light with the read light to project the information written in the spatial light modulator. An overhead projector, wherein the spatial light modulator is provided with a sensitivity adjusting means. 9. The writing means irradiates the projection object with the writing light to write information in the spatial light modulator, and the reading means irradiates the reading light to read and project the information written in the spatial light modulator. In an overhead projector, a document table that supports the projection target so that the writing light of the writing unit is projected from above, and an optical unit that reflects the writing light reflected by the projection target and makes it enter the spatial light modulator. An overhead projector characterized by having and. 10. The writing means irradiates the projection object with writing light to write information in the spatial light modulator, and
In an overhead projector for irradiating the reading light by the reading means to read the information written in the spatial light modulator and projecting the information, a condensing optical means for condensing the writing light reflected by the projection target is provided in the vicinity of the projection target. An overhead projector characterized by being placed. 11. The writing means irradiates writing light onto the projection target to write information in the spatial light modulator,
In an overhead projector for irradiating reading light by a reading means to read and project information written in a spatial light modulator, the writing means is provided with a dimming means for changing writing light intensity according to the projection target. An overhead projector characterized by the above. 12. The writing means irradiates writing light onto the projection target to write information in the spatial light modulator, and
In the overhead projector for irradiating the reading light by the reading means to read and project the information written in the spatial light modulator, the writing means includes first wavelength selecting means for outputting the primary color light as writing light in a frame sequential manner. The overhead projector, wherein the reading means includes a second wavelength selecting means that outputs the corresponding primary color lights as reading light in a frame sequential manner in synchronization with the wavelength selecting means.