JPH05323123A - Optical device - Google Patents

Abstract

PURPOSE:To obtain the optical device with high performance by an easy method by providing an optical system which forms an image of an electric write type optical modulator on the write surface of an optical write type spatial optical modulator. CONSTITUTION:Images of TFT drive type liquid crystal panels 102 are reduced and projected on the optical write type liquid crystal spatial optical modulator 104 through an optical system 103. Divided holograms are recorded on the liquid crystal panels 102 respectively. The laser light emitted by a read laser light source 105, on the other hand, is passed through a collimator lens 109 and a polarization beam splitter 107 and made incident on the read side of the optical write type liquid crystal spatial optical modulator. Its reflected light passes through the polarization beam splitter 107 and reaches an observer 106. Consequently, an amorphous silicon layer is irradiated with write data at all times, so nematic liquid crystal having no memory performance is usable. Further, the number of pixels can be increased, the pixel pitch can be made fine, and a large holography reproduced image with high resolution can be obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to optical devices.

[0002]

2. Description of the Related Art A conventional optical device, as shown in FIG.
The hologram recorded on the electric address type liquid crystal panel 802 is directly reproduced by a laser (first optical device). Alternatively, as shown in FIG. 9, a hologram was recorded on the optically writable liquid crystal spatial light modulator 904 by laser scanning (second optical device).

[0003]

However, in the conventional first optical device, the pixel pitch of the liquid crystal panel is made small enough to obtain a sufficient viewing angle of the reproduced image, and the large panel having a sufficient viewing area is provided. There was a problem that it was also difficult to manufacture. Further, in the second conventional optical device, since the laser light is applied to the writing portion for a moment, the liquid crystal needs a memory property, and the ferroelectric liquid crystal is used. However, since the ferroelectric liquid crystal can control the light in only two gradations,
There has been a problem that the efficiency of light use is extremely reduced when holographic reproduction is performed. The present invention solves such a problem, and an object thereof is to provide a high-performance optical device by a simple means.

[0004]

A first optical device of the present invention comprises at least an optical writing type spatial light modulator and an electric writing type space for generating information to be written in the optical writing type spatial light modulator. It is characterized by comprising an optical modulator and an optical system for forming an image of the electrically writable spatial light modulator on a writing surface of the optically writable spatial light modulator.

A second optical device of the present invention is characterized in that, in the first optical device, the optical writing type spatial light modulator is a phase modulation type.

A third optical device of the present invention is characterized in that, in the first optical device, the optical writing type spatial light modulator is an amplitude phase modulation type.

A fourth optical device of the present invention is characterized in that, in the first to third optical devices, the optical system is a hologram.

A fifth optical device of the present invention is characterized in that, in the first to fourth optical devices, the electric writing type spatial light modulator is an amplitude modulation type.

A sixth optical device according to the present invention is characterized in that, in the first to fourth optical devices, the electrically writing spatial light modulator is a phase modulation type.

A seventh optical device of the present invention is characterized in that, in the first to sixth optical devices, the electrically writing spatial light modulator is a liquid crystal spatial light modulator.

An eighth optical device of the present invention is characterized in that, in the first to sixth optical devices, the optical writing type spatial light modulator is a liquid crystal spatial light modulator.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples.

(Embodiment 1) FIG. 1 shows the configuration of an optical device of the present invention.

The optical writing type liquid crystal spatial light modulator 104 has a T
An image of the FT drive type liquid crystal panel 102 is reduced and projected through the optical system 103. Divided holograms are recorded on the liquid crystal panel 102. On the other hand, the laser light emitted from the reading laser light source 105 passes through the collimator lens 109 and the polarization beam splitter 107 and enters the reading side of the optical writing type liquid crystal spatial light modulator. The reflected light (holographic reproduction image) reaches the observer 106 through the polarization beam splitter 107.

In this embodiment, the writing light source 101 is a laser which is collimated by a collimating lens 108. This is to obtain a uniform light intensity in the plane. An incoherent light source may be used as long as the in-plane variation can be suppressed.

The TFT driving type liquid crystal panel 102 is a TN.
In (Twisted Nematic) mode, the light transmittance can be modulated. On the other hand, the optically writable liquid crystal spatial light modulator is capable of phase modulation of light in the homogeneous orientation ECB (electric field control birefringence) mode. TF used in this example
The T liquid crystal panel has 1440 × 1024 pixels and a pixel pitch of 40 μm.

The optical system 103 corrects the distortion of the image due to the oblique incidence and forms an image on the photo-writing type liquid crystal spatial light modulator. At this time, no gap should be formed between the image from the adjacent liquid crystal panel. In addition, dark lines caused by black stripes on the liquid crystal panel were eliminated by slightly defocusing.

The optical writing type liquid crystal spatial light modulator is described in detail in, for example, SID'90 DIGEST, 327, but its operation will be briefly described here.

FIG. 2 shows the structure of the photo-writing type liquid crystal spatial light modulator used in this embodiment. An image of the TFT liquid crystal panel is projected on the amorphous silicon layer 203. Then, the conductivity of each point changes according to the light intensity, and the voltage applied to the liquid crystal layer 207 changes. This voltage changes the alignment state of the liquid crystal to control light.

In the present embodiment, the photo-writing type liquid crystal spatial light modulator has a homogeneous orientation and nematic liquid crystal is used without twisting. Therefore, the tilt of the liquid crystal molecules is changed by applying a voltage, and the phase of light can be changed due to the birefringence of the liquid crystal. The optically writable liquid crystal spatial light modulator of this example was able to change the phase substantially linearly by 2π or more.

In this embodiment, the phase plate 205 is arranged on the dielectric mirror 204. As a result, the polarization directions of the read light and the reflected light are orthogonal to each other, and the optical path can be easily separated by using the polarization beam splitter.

In this example, kinoform was used as the hologram. Kinoform is the original image with a random phase added to it and Fourier transformed to extract only the phase component. For details, see Appl. Opt. 12 (1
973) 2328.

The kinoform is given as a phase distribution, which is recorded as an amplitude distribution on a TN mode liquid crystal panel. That is, the phase of 0 to 2π is converted into the transmittance of 0 to 1 and recorded. When this amplitude distribution is projected on the optical writing type liquid crystal spatial light modulator, the phase of the reading light can be modulated according to the light intensity. In this way, a phase hologram (Kinoform in this embodiment) is formed on the optically writable liquid crystal spatial light modulator.
Was recorded.

In the present embodiment, the TFT liquid crystal panel is arranged 10 pixels in length and width.
Arrange them one by one (100 in total), each one tenth
It was reduced and projected. Therefore, the hologram written in the optical writing type liquid crystal spatial light modulator has a pixel pitch of 4 μm, the number of pixels of 14400 × 10240, and a size of 58 mm × 41 mm.
Is. The reproduced image from this hologram has a size of about 6 cm square when viewed from a distance of 40 cm. Since it is a rewritable hologram that uses a spatial light modulator, moving images can be easily realized.

If the lasers of the three primary colors of red, blue and green are switched at high speed and the hologram is rewritten in synchronism therewith, color three-dimensional moving image reproduction is possible.

In the writing method of the present invention, unlike the laser scanning method, the writing data is always applied to the amorphous silicon layer, so that a nematic liquid crystal having no memory property can be used. Therefore, the phase can be continuously modulated according to the writing light intensity. Of course, there is no moving part for scanning, and there is an effect that it is easy to handle.

The number of pixels can be increased by increasing the number of liquid crystal panels used. At this time, since the driving circuit of the liquid crystal panel is attached to each liquid crystal panel, there is no problem such as screen flicker. Further, the pixel pitch can be made fine by changing the magnification of the optical system. This makes it possible to obtain a large holographic reproduction image with high resolution.

(Embodiment 2) FIG. 3 shows the configuration of another embodiment of the present invention. In this embodiment, an image of another liquid crystal panel is projected on the shadow portion of a black stripe of a certain TFT liquid crystal panel to increase the aperture ratio and further reduce the pixel pitch.

FIG. 4A shows a state of a pixel of the TFT liquid crystal panel. 401 is an opening and 402 is a black stripe.

FIG. 4B shows a state of a projected image on the writing surface of the optical writing type spatial light modulator. 40 shown by the solid line
3 is a projected image from one liquid crystal panel, which is indicated by a dotted line 4
Reference numeral 04 is a projected image from the other three liquid crystal panels. The aperture ratio was almost 100% and the pixel pitch was halved by inserting projection images from other liquid crystal panels in between.

In this embodiment, since the aperture ratio is 100%, the reproduced image of the hologram does not show a high-order duplicate image.

(Embodiment 3) FIG. 5 shows the configuration of a third embodiment of the present invention. In this embodiment, a hologram element 503 is used instead of the optical system 103. A laser was used as a light source.

This hologram element can reduce an image while correcting distortion of oblique incidence. Further, it is possible to correct the unevenness of the light amount of the light source.

This hologram element was designed in a pattern by a computer and prepared by an electronic beam drawing apparatus.

As a result, the number of parts can be greatly reduced,
It has become possible to reduce the size and cost of the device.

(Embodiment 4) FIG. 6 shows the configuration of a fourth embodiment of the present invention. In this example, holography was also used for data writing.

A kinoform is recorded on the phase modulation type TFT liquid crystal panel 602 and light from the laser light source 601 is irradiated. The reproduced image of this kinoform is formed on the writing surface of the optical writing type liquid crystal spatial light modulator 104. This reproduced image is exactly the light intensity distribution to be written in the spatial light modulator.

In this method, since the distortion correction hologram due to the oblique incidence can be superimposed on the data input to the liquid crystal panel, the optical system 103 can be replaced by the Fourier transform lens.

(Embodiment 5) FIG. 7 shows the configuration of a fifth embodiment of the present invention. In this embodiment, the optical writing type spatial light modulator is of the amplitude phase modulation type.

The photo-writing type liquid crystal spatial light modulator 704 of this embodiment uses a photochromic glass for the glass substrate 210 of FIG. Therefore, when the light having a wavelength of 400 nm or less is irradiated, the transmittance can be changed. Since the He-Ne laser of 633 nm was used for reading, the transmittance does not change.

Since the phase can be changed by the liquid crystal layer, the amplitude and phase of the read light can be modulated at each point. As a result, almost complete control of the light wavefront was achieved and a good reproduced image could be obtained. A Fresnel conversion type hologram was used.

Although the embodiments of the present invention have been described above, the present invention can also be widely applied to optical information processing and display devices.

[0043]

According to the present invention, unlike the laser scanning method, the writing data is always applied to the amorphous silicon layer, so that a nematic liquid crystal having no memory property can be used. Therefore, the phase can be continuously modulated according to the writing light intensity. Of course, there is no moving part for scanning, and it is easy to handle.

The number of pixels can be increased by increasing the number of liquid crystal panels used. At this time, since the driving circuit of the liquid crystal panel is attached to each liquid crystal panel, there is no problem such as screen flicker. Further, the pixel pitch can be made fine by changing the magnification of the optical system. This makes it possible to obtain a large holographic reproduction image with high resolution.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of an optical device of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a photo-writing type liquid crystal spatial light modulator used in an example of the present invention.

FIG. 3 is a side view showing another configuration of the optical device of the present invention.

FIG. 4A is a top view showing a pixel of a TFT liquid crystal panel used in an example of the present invention. (B) is a top view showing a projection image on the writing surface of the optical writing type spatial light modulator used in the embodiment of the present invention.

FIG. 5 is a side view showing another configuration of the optical device of the present invention.

FIG. 6 is a side view showing another configuration of the optical device of the present invention.

FIG. 7 is a side view showing another configuration of the optical device of the present invention.

FIG. 8 is a side view showing a configuration of a conventional optical device.

FIG. 9 is a side view showing a configuration of a conventional optical device.

[Explanation of symbols]

 101 light source 102 TFT drive type liquid crystal panel 103 optical system 104 optical writing type liquid crystal spatial light modulator 105 laser light source 106 observer 107 polarizing beam splitter 108 collimator lens 109 collimate lens 201 glass substrate 202 transparent electrode 203 amorphous silicon layer 204 Dielectric mirror 205 Phase plate 206 Alignment film 207 Liquid crystal layer 208 Alignment film 209 Transparent electrode 210 Glass substrate 401 Opening 402 Black stripe 403 Projection image from one liquid crystal panel 404 Projection image from another liquid crystal panel 503 Holographic element 601 Laser light source 602 Phase modulation type TFT liquid crystal panel 603 Fourier transform lens 701 Light source 702 TFT drive type liquid crystal panel 703 Optical system 704 Optical writing type liquid crystal spatial light modulator 08 collimator lens 801 light source 802 electrically addressed type liquid crystal panel 803 Fourier transform lens 808 collimating lens 901 laser light source 902 a polygon mirror - 903 galvanometer mirror - 904 optical writing type liquid crystal spatial light modulator 905 laser light source 907 a polarizing - beam splitter 909 collimating lens

Claims (8)

[Claims] 1. An optical device for performing wavefront reproduction with coherent light, at least an optical writing type spatial light modulator, and an electric writing type spatial light modulator for generating information to be written in the optical writing type spatial light modulator. And an optical system for forming an image of the electrically writable spatial light modulator on a writing surface of the optically writable spatial light modulator. 2. The optical device according to claim 1, wherein the spatial light modulator of the optical writing type is a phase modulation type. 3. The optical device according to claim 1, wherein the optical writing type spatial light modulator is an amplitude phase modulation type. 4. The optical device according to claim 1, wherein the optical system is a hologram. 5. The optical device according to claim 1, wherein the electrically writing spatial light modulator is an amplitude modulation type. 6. The optical device according to claim 1, wherein the electrically writing spatial light modulator is a phase modulation type. 7. The spatial light modulator of the electrically writing type is a liquid crystal spatial light modulator.
The optical device described. 8. The optical device according to claim 1, wherein the optical writing type spatial light modulator is a liquid crystal spatial light modulator.