JPH02244117A - Optical image converting element - Google Patents

Abstract

PURPOSE:To improve optical and electrical characteristics by optically polishing the adhesive surfaces of a single crystal plate having a photoconductive effect and electrooptical effect and insulating plates and adhering the plates by an optical adhesion (optical contact) method. CONSTITUTION:Side face parts 50a, 50b of the single crystal plate 50 having the photoconductive effect and electrooptical effect, side face parts 52a, 52b, 54a, 54b of the insulating plates 52, 54, and side face parts 56b, 58a of electrode plates 56, 58 which face the insulating plates 52, 54 are respectively optically polished. The dust, dirt, etc., of the side face parts 50a, 50b, 52a, 52b, 54a, 54b and 56b, 58a (side face parts A) as the adhesive surfaces are removed and the side face parts A to be adhered are brought into contact with each other and are so held and tightly adhered that these parts are pressed to stick to each other. The optically polished side face parts A are, therefore, put into the optically adhered (optical contact) state. Since adhesive agent of epoxy resins, etc., are not used at the time of such adhesion, various troubles, such as unequal images, due to the adhesive agents are eliminated.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an optical image conversion element using a single crystal having a photoconductive effect and an electro-optic effect, and in particular, a layer of a flat plate made of the single crystal. When attaching electrodes to both sides or one side through insulating plates, it is possible to improve optical and electrical characteristics by bonding at least the single crystal plate and the insulating plate by an optical contact method. The present invention relates to an optical image conversion device.

[Prior art] The optical image conversion element is F ROM (Pockeles®
eadout 0ptical Modulator)
It is also called an element and belongs to a spatial light modulator. That is, it is an element that applies a predetermined intensity modulation to input information having a spatial distribution, for example, input optical information such as an image, and operates to obtain output optical information.

To explain more specifically, image information is written and stored by irradiating the optical image conversion element with X-rays or blue light, and red light is converted into red light according to the recorded information by irradiating it with red light during readout. Output image information is obtained by applying modulation, and this recording and output process has the characteristic that it can be repeated any number of times by erasing the recorded information.

Therefore, applications of the optical image conversion element operating in this manner include image color conversion, X-ray image detection, gradation adjustment, edge enhancement, ITC conversion, and parallel logical operations. In other words, in color conversion, blue light is used as the write light and red light is used as the read light, taking advantage of the property that an image identical to the recorded image is output by using light with a uniform intensity distribution as the read light. This allows the color of the image to be converted from blue to red. Furthermore, as described above, since X-rays can be used as the writing light for detecting an X-ray image, the X-ray image can be detected by reading out this recorded image. Furthermore, when adjusting gradation and emphasizing edges, if appropriate operations are performed when recording images are successively produced, processing such as adjusting the shading, reversing negative/positive, emphasizing edges, etc. of successive images can be performed. Further, ITC conversion is a process that uses a laser as a readout light and can convert an image made of incoherent light into an image made of coherent light. In this case, since images produced by coherent light can be subjected to various optical processing such as Fourier transformation and holography processing, the processing by ITC transformation has a wide range of useful applications. Parallel logical operations also involve making the intensity of an image correspond to a binary level of high level or low level, and using an image that has read out certain logical information as the readout light, and applying appropriate operations when successive readings are performed to read out recorded information. It is a process in which logical operations such as AND and OR are performed between the images, and the results of these operations can be extracted as an output image.

At this time, multiple pieces of data can be processed in parallel in time by utilizing the parallel characteristics of light, making it possible to perform high-speed logical operations.

As described above, optical image conversion elements that have various application fields are elements that utilize the photoconductive effect and electro-optic effect of single crystals such as bismuth silicon oxide BI123I020 (hereinafter referred to as BSO). Here, the photoconductive effect is
When light enters a dielectric or semiconductor, carrier charges proportional to the incident light are generated, the resistivity decreases, and photocurrent can be caused to flow by applying a voltage. For example, when the single crystal is BSO, this effect is large with X-rays and blue light, and conversely, it hardly occurs with red light.

On the other hand, the electro-optic effect here refers to the Pockels effect, which is an effect in which when an electric field is applied to a single crystal, the refractive index of the single crystal exhibits birefringence depending on the magnitude of the electric field. When is BSO, n, , n in the direction perpendicular to the electric field
, an axis is created. Therefore, linearly polarized light incident parallel to the electric field is transmitted as elliptically polarized light having an ellipticity corresponding to the magnitude of the electric field.

FIG. 1 shows the basic structure of an optical image conversion element having such attributes. In the figure, the optical image conversion element indicated by reference numeral 2 includes a single crystal plate having a photoconductive effect and an electro-optic effect, for example, a BS○S○ crystal 4, and an insulating plate 6 is provided on both sides of the BSO single crystal 4. The structure is such that the transparent electrode 8 is attached via.

Next, the operation and operation of the optical image conversion element 2 configured as described above will be explained.
The procedure will be explained with reference to FIGS. 2a to 2e.

First, as shown in FIG. 2a, a voltage source 1 is connected between the transparent electrodes 8.
0 and apply a predetermined DC voltage. In this case, the potential gradient Eh (n=1.2) within the image conversion element 2 is
As shown by reference numeral E1 in Figure a, a spatially -like electric field occurs within the BSO single crystal 4. In order to facilitate understanding of the prior art, the potential gradient E is shown separately for the upper and lower partial regions of the BSO single crystal 2, and in this case,
When the numbers in the subscript n have the same value, they represent the same potential gradient.

Therefore, when writing, as shown in Figure 2,
The lower half region 2a of the optical image conversion element 2 is shielded from light, and the light 14 having an image formed by blue light or X-rays is incident only on the upper half region 2b. In this case, positive and negative carriers 16 and 18, represented by the sign or e, are generated in the BS○S○ crystal 4 according to the amount of incident light 14. The carriers 16 and 18 generated in this way are transferred to the BS○ single crystal 4 by Coulomb force due to the external electric field generated by the voltage source 10.
The presence of the mortar plate 6 prevents further movement, and the carriers 16 and 18 accumulate on both end faces of the BSO single crystal 4. The density of the polarized and accumulated carriers 16, 18 corresponds to information on the intensity of the writing light.

In this case, the polarized carriers 16, 18 generate an electric field in the opposite direction to the external electric field. Therefore, the electric field applied to the crystal is the sum of the external electric field and the electric field due to carriers 16 and 18. In other words, the electric field within the crystal becomes smaller in the portion where the carrier density is high (see potential gradient E2). In the end, the information of the written image is replaced by the electric field intensity distribution within the BSO single crystal 4. If the optical image conversion element 2 is kept in a dark place in this state, the BSO single crystal 4 becomes an insulator again, so the polarized carriers 16 and 18 are retained as they are, and image information is recorded for a long time. .

Next, when reading out, first, a case where a negative image is output will be explained. In this case, as shown in FIG. 2C, light 20 that does not have a photoconductive effect, therefore does not destroy written information, for example, red light 20 with low light intensity.
Inject 0.

Therefore, the linearly polarized light transmitted through a polarizer (not shown) is BSO
The light is converted into elliptically polarized light according to the electric field distribution within the single crystal 4 and passes through the BSO single crystal 4.

Next, red light 22 is transmitted through an analyzer (not shown) disposed perpendicular to the polarizer, and is outputted as red light 22 having image information having a light intensity distribution according to the electric field distribution. The red light 22 having this image information has information of a negative image with respect to the original image.

Next, when reading out a positive image, as shown in FIG.
8 (see potential gradient E). In this state, the red light 22 with image information
has information of a positive image with respect to the original image.

Next, when erasing the written image, as shown in FIG.
are recombined and return to their original state. In this case, since no voltage is applied to the single crystal, the potential gradient becomes zero level E4.

[Problem to be solved by the invention] The optical image conversion element that operates as described above is actually a third
It is configured as shown in the figure. In other words, BS○S○ Akira 4
When attaching the insulating plate 6 and the transparent electrode 8 to both sides of the substrate, the insulating plate 6 and the transparent electrode 8 are attached via optical adhesive layers 32 and 34 such as epoxy resin.

However, by interposing such optical adhesive layers 32 and 34, the above-mentioned BSO
The voltage applied to the single crystal 4 decreases, causing the inconvenience that the voltage of the voltage source necessary for image formation must be increased.Furthermore, the non-uniformity of the thickness of the optical adhesive layers 32 and 34 As a result, uneven brightness occurs in successive images.Furthermore,
Hardening and shrinkage of the optical adhesive layers 32 and 34 occur, and as a result, the BS○ single crystal 4, the insulating plate 6, and the transparent electrode 8 are distorted.
As a result, distortion occurs in the successive images. Moreover, air bubbles may be mixed into the optical adhesive layer 32, 34, and the subsequent images will also be distorted in this case. Furthermore, the crystal is slightly distorted due to the piezoelectric effect of the BSO single crystal 4 caused by applying a voltage to the BSO single crystal 4, and this distortion causes the optical adhesive layer 32 that has already hardened to absorb the strain stress. There is a possibility that the insulating plate 6 may be peeled off from the BSO single crystal 4 due to the insulating plate 6 not being completely removed. Furthermore, adhesive layer 3
2 and 34 and within the BSO single crystal 4, interference fringes due to multiple reflections of light are likely to occur, resulting in various disadvantages such as deterioration of the readout image.

The present invention has been made in order to overcome the above-mentioned disadvantages, and at least connects a single crystal such as BSO and an insulating plate by optical bonding (optical contact). Therefore, it is an object of the present invention to provide an optical image conversion element with excellent characteristics without optical distortion.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a single crystal plate having a photoconductive effect and an electro-optic effect, and an insulating plate attached to at least one side of the single crystal plate. and an electrode layer that applies an electric field to the single crystal plate through the insulating plate, in which at least opposing surfaces of the single crystal plate and the insulating plate are polished, and then they are pressed together. By doing so, the single crystal plate and the insulating plate are brought into an optically bonded state.

The present invention also provides a single-crystal plate having a photoconductive effect and an electro-optic effect, an insulating plate attached to a side surface of the single-crystal plate, and an electric field applied to the single-crystal plate via the insulating plate. In the optical image conversion element, the monocrystalline plate, the insulating plate, and the electrode plate are bonded together after polishing the opposing surfaces of the single crystal plate, the insulating plate, and the electrode plate. It is characterized by being optically bonded to the plate.

[Operation] When producing an optical image conversion element consisting of a single crystal plate, an insulating plate, and an electrode layer or electrode plate having photoconductive effects and electro-optic effects, at least the contact surface between the single crystal plate and the insulating plate is polished. After bringing them into close contact with each other, a predetermined load was applied to form an optically bonded state, and an optical image conversion element with excellent electrical and optical properties was obtained.

[Example] Next, preferred examples of the optical image conversion element according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 4, reference numeral 50 indicates a single crystal plate having a photoconductive effect and an electro-optic effect, and the single crystal plate includes:
B112SiOzo, B112GeO20, etc. are employed. Both side surfaces 50a, 50 of this single crystal plate 50
Insulating plates 52, 54 and transparent electrode plates 56, 58 made of metal oxide or the like are arranged in parallel with each other while being spaced apart from each other by using a processing jig (not shown).

Here, optical glass or single crystal is used as the insulating plates 52 and 54, and borosilicate glass, quartz glass, etc. are used as the optical glass, and on the other hand, as the single crystal, mica, L i N b O3, L i T a Os
etc. will be adopted. Further, as the electrode plate 56.58, optical glass, for example, borosilicate glass is adopted as the base material, and the side surface portion 56a of the electrode plate 56.58,
A metal oxide such as In*03 or SnO2 is vapor-deposited on the entire surface of 58b to form a transparent electrode.

The side portions 50a, 50b, 52a, 52b, 54a, 54b of the single crystal plate 50, the insulating plates 52.54, and the side portions 5 facing the insulating plates 52.54 of the electrode plates 56.5B
6b and 58a are each optically polished. Their surface roughness (center line average roughness: R1) is 0.1 μm or less, and preferably 0.02 μm or less in order to reduce light scattering as much as possible. In addition, their flatness can be less than 2λ (λ = 546 nm), but
Problems such as easy peeling and interference fringes may occur, so it is preferably less than λ, more preferably λ/2.
The following are desirable.

The single crystal plate 50, the insulating plates 52 and 54, and the electrode plate 56
．． 58 side parts 50a, 50b, 52a, 52b, 54
The size of a154b, 56a, 56b and 58a, 58b is 1 to 200 mm square, preferably 10 to 10 mm square.
It is 0 mm square. Further, the thickness of the single crystal plate 50 is 0.
．． 05~5mm, preferably 0.3~Q, 3m
It is assumed that m. Furthermore, the thickness of the self-insulating plates 52 and 54 is 0.002 to 1 m when the material is glass or mica.
fIl, preferably 0.01 to 0.03 mm. In addition, its materials include L i N b O3, L
i 0.01-5m when using TaO3 single crystal
m, preferably 0.1 to 1 mm.

In such a configuration, first, the side portions 50a, 50bs 52a, 52b, 54a serve as adhesive surfaces.

Remove dust, clumps, etc. from 54b, 56b, and 58a (hereinafter collectively referred to as side surface portion A).

Next, the side parts to be bonded are brought into contact with each other, and held so as to be pressed against each other so as to be brought into close contact. As a result, the optically polished side surfaces are brought into an optical bonding state (optical contact).

In addition, as a method to reach an optically bonded state,
One possible method is to bring the boards to be bonded into close contact with each other in pure water, then take out the stuck boards and dry them until the water becomes a molecular film.

Note that in the above embodiment, the electrode plates 56 and 58 are omitted, and the thickness of the insulating plates 52 and 54 is increased.
In2O5, S described above on the side parts 52a and 54b of 54
It goes without saying that the electrode layer may be formed by vapor depositing a metal oxide such as n02.

The optical image conversion device thus created is shown in Figures 2a to 2e.
It acts on the explanation shown in and between the roads.

In this case, since the optical image conversion element according to this embodiment does not use an adhesive such as an epoxy resin for bonding, it has the advantage that various inconveniences such as image unevenness caused by the adhesive can be eliminated. It will be done.

Specific examples will be described below.

Example 1 A 30 mm x 830 mm x 800 μm' (100)-plane single crystal plate was cut out from a Bi, SiO2° single crystal produced by a pulling method, and both sides of the plate were optically polished to a flatness of λ/4. 40mm x 40mm x as insulation board
Using 30 μm' borosilicate glass, the electrode plate was 40 mm x 40 mm x 4 mm' with a flatness of λ/
4. Optically polished borosilicate glass with an ITO film, which is a metal oxide film, was used.

After the insulating plates are brought into close contact with both sides of the single crystal board and adhered to each other by optical contact, electrode plates are further brought into close contact with both sides of the single crystal board and pressed together to form an optical contact. An optical image conversion element was produced by adhering using an adhesive method.

On the other hand, for comparison, an optical image conversion element according to the prior art was fabricated by bonding a single crystal plate and an insulating plate with an optical adhesive, and then bonding electrode plates to both sides with an optical adhesive.

When a He-Ne laser was transmitted through the element fabricated by Honzuke and the transmitted wavefront and spatial frequency spectrum were observed, it was found that the element had better characteristics with no wavefront aberration than the element using adhesive. Its characteristics are shown in Table 1.

Table 1 In Table 1, the half-wave voltage is the voltage corresponding to the image writing voltage, and the resolution (lp/w) is the number of black and white line pairs that can be confirmed in the l s width. represents.

Furthermore, the durability such as thermal shock resistance of the optical image conversion element according to this example was significantly improved compared to the conventional method using an adhesive.

Example 2 30 mm x 30 mm x 800 μm from B ll 25 r 02° single crystal produced by pulling method
Cut out a (100) plane plate of t, and have both sides with flatness λ
Optically polished to /4. 40mm x 40 as an insulation board
A mica plate of mm x 10 μm' is used, and the flatness of the electrode plate is 4Q mm
IT on one side of optically polished borosilicate glass
One with an O film was used.

After insulating plates were brought into close contact with both sides of the single crystal plate and adhered by optical contact method, electrode plates were brought into close contact with both sides and adhered by optical contact method to fabricate an image conversion element. did. Its characteristics were as shown in Table 1, such as between the element and the path.

Example 3 B 112 S i O2° produced by the pulling method,
30mm x 3Qmm x 300p from single crystal
A single crystal plate of the (100) plane of m' was cut out, and both sides thereof were optically polished to a flatness of λ/4. 40mm as an insulating plate
L r N b of X 40 mm X 300 μm'
Using Oz, the electrode plate is 4Qmm X4Q+nm
Borosilicate glass optically polished to a flatness of x 4 +r+m' of λ/4 with an ITO film attached thereto was used.

An insulating plate is closely attached to one side of the single crystal plate and optical bonding (
After bonding using the optical contact method, electrode plates are attached to both sides of the electrode plates to create an optical bond.
An image conversion element was fabricated by adhering the two using a method.

In the above embodiments, Pyrex glass (trade name of Corning Corporation) or BK7 glass can be used as the borosilicate glass.

[Effects of the Invention] As described above, according to the present invention, when producing an optical image conversion element, the bonding surface between the single crystal plate having the photoconductive effect and the electro-optic effect and the insulating plate is optically polished, and the optical Adhesive using optical contact method. Therefore, since no adhesive is used for bonding, the effects of distortion of subsequent images or interference fringes caused by adhesive when using the optical image conversion element are completely eliminated, and furthermore, The voltage of the power supply required for image detection can be lowered without causing a drop in the voltage applied to the single crystal due to the thickness of the adhesive, and an optical image conversion element with extremely improved optical and electrical properties can be obtained. .

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and changes in design can be made without departing from the gist of the present invention. Of course.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram for explaining the principle of the optical image conversion element, Fig. 2 a to e are diagrams for explaining the operation of the optical image conversion element, and Fig. 3 is a diagram of the optical image conversion element according to the prior art. 4 is an explanatory diagram of the exploded configuration of the optical image conversion element according to the present invention; and FIG. 5 is an explanatory diagram of the configuration of the optical image conversion element in an optically bonded state according to the present invention. 50... Single crystal plate 52.54... Insulating plate 56.58... Electrode plate

Claims (8)

[Claims] (1) A single crystal plate having a photoconductive effect and an electro-optic effect,
An optical image conversion element comprising an insulating plate attached to at least one side of the single crystal plate, and an electrode layer for applying an electric field to the single crystal plate via the insulating plate, which includes at least the single crystal plate. An optical image conversion element characterized in that the single crystal plate and the insulating plate are brought into an optically bonded state by polishing the surface facing the insulating plate and then press-bonding the single crystal plate and the insulating plate to each other. (2) In the optical image conversion element according to claim 1, the surface roughness (R_a) of the contact surface between the single crystal plate and the insulating plate is 0.1.
An optical image conversion element characterized by having a flatness of μm or less and a flatness of 2λ or less. (3) The optical image conversion element according to claim 1 or 2, wherein the material of the insulating plate is optical glass. (4) The optical image conversion element according to claim 1 or 2, wherein the material of the insulating plate is a single crystal. (5) A single crystal plate having a photoconductive effect and an electro-optic effect,
An optical image conversion element comprising an insulating plate attached to at least one side of the single crystal plate, and an electrode plate for applying an electric field to the single crystal plate via the insulating plate, which is insulated from the single crystal plate. After polishing the opposing surfaces of the plate and electrode plate,
1. An optical image conversion element characterized in that the single crystal plate, an insulating plate, and an electrode plate are brought into an optically bonded state by being pressure-bonded to each other. (6) In the optical image conversion element according to claim 5, surface roughness (R_a) of the contact surfaces of the single crystal plate, the insulating plate, and the electrode plate.
is 0.1 μm or less, and the flatness is 2λ or less. (7) The optical image conversion element according to claim 5 or 6, wherein the material of the insulating plate is optical glass. (8) The optical image conversion element according to claim 5 or 6, wherein the material of the insulating plate is a single crystal.