JPS59127884A - Picture conversion element - Google Patents

Abstract

PURPOSE:To write informations by incoherent visible rays and read them by coherent infrared rays, to increase the kinds of light sources and to improve sensitivity and resolution by holding a photoconductive body with a semiconductor made of a zinc blende type crystal by a pair of electrodes through an insulator. CONSTITUTION:An insulating film 32 in 7mum is formed on Cd0.3Zn0.7Te 31 as a photoconductive body in 500mum thickness prepared through a high-pressure melting method, and transparent electrodes (In2O3.Sn) 33 are formed on both surfaces through a reactive sputtering method. Voltage of 2kV is applied between the transparent electrodes 33, 33, and informations are written by incoherent beams (c) from a tungsten lamp. Coherent beams (d) from a laser in a 1.06mum wavelength are used, and projected to a picture conversion element through a polarizer 36. Only components modulated by the conversion element are changed into coherent beams (e) converted through the polarizer 36 and an analyzer 37 positioned at the position of a cross Nicol. Cd0.3Zn0.7Te has sensitivity extending over the whole visible regions, and visible rays can be used for writing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image conversion system for storing and converting ordinary incoherent optical images into coherent optical images.

Conventional configurations and their problems Parallel processing of two-dimensional information using coherent light overcomes the limitations of time-series processing by computers and enables real-time pattern recognition. However, most ordinary images are made of white incoherent light (and an element is required to convert this incoherent light image into a coherent light image).

This image conversion system requires two 8i functions. One is image writing using incoherent light.
In response to this, it is a function to create and accumulate a pattern such as a charge distribution according to the charge distribution. A photoconductor often performs this function. The other is a function that corresponds to the pattern of this incoherent light and gives 124+ modulation to the coherent light. This function utilizes the Pockels effect, the domain of ferroelectric material, the alignment of liquid crystal, etc.

A conventional image conversion element will be explained using FIG. 1.

Figure 1 (4) is a cross-sectional view of an image conversion element that combines a liquid crystal and a photoconductive film. The light is guided through f4i (2) and converted into a heavy pattern by the membrane (3). The incoherent light (a) stops at the first stopper layer (4) and does not enter the left side after that, transparent turtle 14
1 (2) (8) When a constant voltage is applied to rl, the electric ratio of C distributed to the liquid crystal (7) changes according to the load pattern of the photoconductive film (3), and the liquid crystal (7) It has a strange scissors in the inner Umimukai pattern. Coherent light (b) from the left side of the figure
When incident on the glass (9), the coherent light (b)
and a transparent electrode (8), passes through a liquid crystal (7) that changes the polarization angle of the coherent light (b), and passes through a dielectric mirror (
5) and returns from the glass (9) again. In this way, the strength of the incoherent light (a) incident from the right side is converted into a spatial distribution of polarization angles of the coherent light (b). (6) is a finished oriented film.

Although the device shown in FIG. 1 operates at low voltage, it has a drawback of slow response time.

1) is a sectional view of an image conversion element using Bi125i02o (hereinafter referred to as BSO). This BS
O01 is a material that has both a photoconductive effect and a Pockels effect. When a constant voltage is applied between the transparent vM and poles (1-905) attached to this BSO (12) through an insulating layer (to), and a pattern of incoherent light from ultraviolet to blue (A) is irradiated, the entrance side The voltage distribution between the insulating layer (to) and the BSOlla changes spatially depending on the amount of light. (to)
is an interference filter that passes ultraviolet and blue light and reflects red light. The Pockels effect is a first-order electro-optic effect in which anisotropy of the refractive index appears depending on the applied voltage.
When linearly polarized coherent light (b) passes through, the optical component changes depending on the applied voltage (b).Only the changed component passes through the analyzer aη, and the coherent light (b)
is converted into a pattern of Since B50(2) allows red light to pass through, it is best to use red coherent light as the read light. The image conversion element using this B50(6) has problems in sensitivity and resolution.

This Pockels effect is also observed in zincite-type crystals. As a semiconductor having photoconductivity and having a zincite type crystal, there is a group I-4 compound semiconductor. Furthermore, since the image conversion element 'C requires high resolution, it is preferable that it has a large specific resistance.

For example, since ZnS is a ■-■ group compound with high resistance and photoconductivity, it is
As shown in 769 and C, it is used as a double conversion element. Its structure is shown in FIG. 1(C). This Zn5
(E) is grown on a GaAs single crystal. Then, an insulating layer (2) and a transparent electrode ring were formed on the CZnS layer and heated at °C. The GaAs single crystal t41J has a low resistance, and one of the electrodes also serves as a b'r11.The incoherent light (4) passes through the interference filter decoy and forms a pattern that is absorbed by the ZnSσ. Coherent light (0 is Zn
The light is reflected at the interface between the GaAs single crystal (S) and the GaAs single crystal (C), and is separated from the incident light by a Glan-Thompson prism. This Zn5(A) has a sufficient degree of resolution, but like B50Qa and 11-11, writing is performed using incoherent ultraviolet light, and C has the drawback of poor sensitivity.

Purpose of the Invention The present invention solves the above-mentioned drawbacks of the conventional technology, and is capable of capturing images using incoherent visible light and reading them using coherent infrared light, increasing the number of types of light sources, and achieving image conversion with high sensitivity and resolution. The purpose is to provide devices.

Structure of the Invention In order to achieve the above object, the image conversion element of the present invention comprises (C
dxZn1-xTe )1-y(In2Te3)y (
0SXSI, Q <, y≦0.1) 4, a pair of electrodes sandwiching the photoconductor, and a photoconductor interposed between at least one of the pair of electrodes and the photoconductor. The structure is equipped with an insulator and an insulator.

That is, the image conversion element of the present invention is a semiconductor having a zincite type crystal and excellent photoconductivity in the visible light region (
Cdx Zn1-x Te )ty'(In2 T
e5) The main component is Y [0≦X≦1, Opy≦0.1]. Figure 2 shows the photoconductive sensitivity of various materials.

(a) is ZnS, (b) is BSo, (C) is Z
nTe s (d) is mu of CdTe. (e) is Zn5e-Cdo, 2Zn6. ．． 1 'l''e. As shown in Figure 2, when a heterojunction is formed between polished Cd Zn Te and a window material such as Zn Se with a wide forbidden band width, the forbidden band width of the window material and Cdx Zn1-x
It has sensitivity in the wavelength region between the forbidden band width of Te. By forming this heterojunction Q, not only high sensitivity but also low dark current can be achieved.

Furthermore, by forming a solid solution with In2Te3, the dark current can be reduced and the response to light becomes faster.

Cdx Zn1-x Te and (dx Zn1-x T
e ) + - y (In2 Te5) y and 0≦y≦0
Since the prohibited band width does not change significantly in the range of 1, CCd
x Zn4-x Te )1-y (In2 Tes
) The photosensitivity of y is in the visible light region like Cdx Zn1-x Tc.

Note that when y>0.1, dark current increases, making it difficult to form an incoherent pattern at low illuminance, which is not preferable. In the present invention, paying attention to this point, the BS shown in FIG. 1(B)
O02, instead of ZnS OQ in mt diagram (C), (Cd
The problems of the above materials are solved by using a material with a single layer or heterojunction structure, which has xZnl-xTe)+-y(Ing Te5)y as its main component.

The image altering element of the present invention can be read out using normal incoherent visible light and coherent infrared light. This is advantageous in the following respects.

■ Usually, the objects that we process information are in the form that we can see with our eyes. In other words, there are many objects that are convenient to read with visible light.

■ The light source for writing only needs to be visible light, and no special light source is required.

■ Using coherent infrared light for readout is advantageous because many lasers including semiconductor lasers can be used. Moreover, the light for image processing does not necessarily have to be visible light, and only the final processing result may be converted into visible light using a second harmonic converter, an infrared film, an infrared television camera, or the like.

Zn5e-(C
dx Zn1-x Te )1-y (ln2 Tes
) y is used as an image pickup tube target for the product name 1 Newbicon, and it has been demonstrated that it is possible to achieve high resolution. When used as an image pickup tube or solid-state image pickup plate, one electrode should be a full-surface electrode, and the other electrode should be used for electron beams,
Switching is performed in time series in the scanning circuit. When this photoconductor is used in the present invention, one main surface side of the photoconductor is made an insulator so that no current flows, and a charge pattern is formed on the photoconductor.

Therefore, the function of the insulator is unreliable in order to retain the charge pattern. Since the charge pattern written with light is read out in parallel by re-lighting, the operation is different from that of an image pickup tube or a solid-state image pickup plate.

DESCRIPTION OF EMBODIMENTS Hereinafter, a syncretic embodiment of the present invention will be described based on one example.

[Example ■]

Cd6 prepared by high pressure bath melting method. s Znq, 7
Cleave the Te on the (110) plane and take out the flat plate. It was polished and etched to a size of 500 μm thick with 1.5 an x 8 cn+ sandalwood, and both sides were slightly tapered. As shown in FIG. 8(a), CdO which is a photoconductor
, 3Zn6.7 Te C3T) on top of the product name Pary
After forming a 7 μm insulating film (A) of Iene, it was made transparent by reactive sputtering! ) C441 (In20s, 8 mouths) (goods) is formed on both sides. Transparent WL pole (to) (to) h
A voltage of 2 KV was applied to the disk, and writing was performed using incoherent light (c) from a tungsten lamp. i.e. Cdo, 3
Zno, 7 Te lυ incoherent light (c)
An electrical distribution pattern corresponding to this was formed.

Next, as shown in FIG. 8(b), coherent light from a laser with a wavelength of 1.06 μm is used and made incident on the image conversion element through a polarizer. Only the modulated component here becomes coherent light (E) converted through a polarizer (E) and an analyzer located at a crossed Nicols position. In Figure 4 (a
) as shown in Cd6. sZno and yTe have sensitivity in the entire visible range, which is significantly different from BSO shown in FIG. 2(b), which has a sensitivity of only 500 μm or less. 1st below
As shown in the table, Bso and CdTe*ZnTe
There is not much difference in Pockels coefficient of 1.

Although there is not much difference in the efficiency of conversion from incoherent light to coherent light in Table 1, it is clear that visible light can be used for writing in this example. To erase the written image, it is sufficient to short-circuit the transparent electrodes (to each other).

[Example]

As shown in Figure 5, the C
ZnSem is formed on the surface of the incoherent light incident side of do,,Zno,7TeC1σ by 2oooi vapor deposition.

Other steps are the same as in [Example I]. In this way, as shown in Fig. 4 (C), high fi
It becomes li. Figure 4 (b) (c) (d) is Zn5
e -Cd(,,3Zn(1,7Te sensitivity, each with different ZnSe thickness. Zn:Se(to)
plays the role of window effect, Cd6.3 Zno, 7 T
Light with a wavelength larger than the 0 energy bandgap of e 01,
This is to prevent recombination of carriers generated by light on the short wavelength side. In this example, a tungsten lamp was used.
When C writing is performed, the amount of light is reduced by one to two orders of magnitude compared to [Embodiment I].

[Example 1] As shown in FIG. 6, Cdo, 3Zno of [Example ■]
, 7 Te instead of @, (Cd6.3 Zno, y
Te ) o, vr (In2Ts4). , O5(
A) was used as a photoconductor. The other configurations are the same as [Embodiment 1]. By doing this, the resolution is improved and the erasing time becomes faster even when the inversion is performed.Table 2 below shows a comparison with the conventional example.

Table 2 As shown in Table 2, by forming a solid solution with In2Te3, the specific resistance increases and it is thought that there are only a few traps that capture holes.

[Example ■]

In the case of [Example I] to [Practical example], the element can be made very thin in terms of mechanical strength. In order to solve this problem, an example will be shown in which the part that performs image conversion is formed of a thin film.

After a Zn5e single crystal grown by the vapor phase method is heat-treated in a Zn solution to lower its resistance, a [111] plane with an area of about 1aII×ion is used and a thickness of 0.5j! 11.

This is etched with dichromate sulfuric acid and used as a substrate.
As shown in FIG. 7, a transparent electrode (I
n20s) 1511 by the sputtering method, 10 cdTelI21 was deposited on the other surface of the substrate by the proximity method.
pms (ZnTe)o,n (In2Tes)
o,ot@20μm, substrate temperature 100~+300°C
(Fig. 7(a)). This was heated to 550℃ in a vacuum.
, after heat treatment for 2 hours, CdTen2 and (ZnTe)0. H(In2
Te3) o, o+ f531 is (CdxZn1-x
Te)+-y (In2Tes)y layer-. Glass is formed on this by a sputtering method, and then a transparent electrode (In203) is formed by a reactive sputtering method (FIG. 7(b)). In this image conversion element, when a positive voltage is applied to the transparent electrode, the electric field changes to (CdxZn1-xTe)1-y(In3
It takes one layer of Tes)y and one glass. As a result, the image conversion layer became thinner, and the resolution was better than in the case of [practical inversion].

[Example Y]

A CdTe single crystal wafer formed by the Bridgeman method was used with a thickness of 0.5 fl and an area of 81 x 8 (111) planes, and glass was formed on one surface by the sputtering method. , In the other track, In metal is vapor-deposited, vacuum-sealed together with Zn metal, and heat treated. When such heat treatment is performed, Z is added to the CdTe single crystal.
Diffusion of n and In occurs, and (CdxZn1-x Te
) ty (In2 Te3 ) y-. Finally, create a transparent electrode (material) on the glass 1, and
Use the golden bird as it is as an electrode assembly (Figure 8). In this case, both the rock entry light and the readout light enter from the left side of Figure 8, and the coherent light is! Reflected by the $jA gauze, (Cdx
Zn1-xTe)1-y (In2Tea)y
Pass through the layer of El twice. In this case, a similar coherent signal can be obtained with twice the modulation and with a voltage that is approximately half of the applied voltage in [Embodiment 2].

Note that in the above example, Zn Se −(Cdx Znt
-xTe)1-y(In2're, )y heterojunction was mainly explained, but instead of this Zn5e, GaN
5n0, etc., 5n0, etc.
2. Oxides such as CdO may also be used.

Furthermore, although the device of the present invention has been described as an incoherent light-coherent light converter, it is limited to a wavelength conversion device that converts a visible light pattern into an infrared light pattern, regardless of whether it is incoherent or coherent. C can also be used.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, as described in detail, (Cdx Zn1-x Te )ty with high photoconductivity and Bockel effect
(I n2Te3 )y (0:x≦1.0≦y≦0
1), the incoherent light for writing can be visible light, and the coherent light for reading can be infrared light, and there is a wide variety of light sources and freedom of choice.
The photoconductive wavelength range is wide and the resolution is high because of the high m degree and the high dark specific resistance. Furthermore, since the response characteristics are good, it is advantageous for high-speed image processing such as erasing.

[Brief explanation of the drawing]

Figures 1 (A) to (C) are cross-sectional views of conventional 'g' and 1 elevation conversion elements, Figure 2 is an explanatory diagram of photoconductive sensitivity, and Figure 8
The figure is a cross-sectional view of the image conversion element according to the embodiment of FIG. 1, FIG. - It is a sectional view of the image conversion element in a 5th example. 0])...Cd+1.3 Zn (,,7Te s)
...Insulating film, (to)...Transparent electrode, Threat 1-Zn
SesH-(Cdo, 3Zno, yTe)0.
95 (ln2Te3) o, os, 6...substrate, wire)@...transparent electrode, 95ka...CdTes (foundation)
...(Zn Te )o, all (In2 Te3
) o, ot, 1541- (CdxZn1-x T
e) ty(In2Te5)ys M++ glass, -... glass, m ・g pole, Ell -(Cdx
Zn1-x Te)+-y (In2 Te3)y
s N-transparent electrode. Agent Yoshihiro Morimoto Figure 1 1(C) 2 7β , 3202/4 Figure 3 Ctl) Figure 2 438- (G) Figure 4 JP-A-59-127884 (7) Figure 7, 11) , Me Fig. 1 641/, 43 χ stroke''

Claims (1)

[Claims] 1. (CdxZn+-xTe)+-y(In2Te
3) VLO > XSI, Q (, -y <-Q, 1) A photoconductor that covers the layer, a pair of electrical contacts that sandwich this photoconductor, and a pair of electrodes and a musical notation. A small number of letters with light (
On the other hand, it was an image conversion system that was interposed and was able to stir up the t-co-loquan body. 2. Photoconductor 1, (CdX Zn1-x Te )+
-y (ln2 Tea)y(,0;,!≦1.0,4
ySOt)m and a semiconductor layer having a bandgap width wider than the chest, and a heterojunction force of 1 is formed.