JPH0244312A - Phase converting element - Google Patents

Abstract

PURPOSE:To arbitrarily execute a sum or difference operation of a specific area of a wave front of parallel light information and other area by constituting the title element so that linearly polarized light which is brought to polarization in the main axis direction of a refractive index elliptical body of an electro-optical crystal used at the time applying a half-wavelength voltage between opposed transparent electrodes is made incident in parallel to an optical axis of the electro-optical axis. CONSTITUTION:An opposed transparent electrode 2 is formed in a specific area of parallel planes vertical to an optical axis of an electo-optical crystal 1, a transparent thin film 3 whose optical film thickness is equal to optical film thickness of the opposed electrode 2 is formed in other parallel plane areas than the specific area, and also, between the opposed transparent electrodes 2, a means 5 which can apply a voltage being at least equal to a half-wavelength voltage of the electro-optical crystal 1 to be used is provided. In such a state, linearly polarized light which is brought to polarization in the main axis direction of a refractive index elliptical body of the electro-optical crystal 1 to be used at the time applying a half-wavelength voltage between the opposed transparent electrodes 2 is made incident in parallel to the optical axis of the electro-optical crystal 1. In such a way, a phase conversion of a specific area of a wave front of parallel optical information can be realized without using a complicated means of branching and coupling, and by only controlling the magnitude of a voltage applied between the opposed transparent electrode 2, the phase conversion quantity can be controlled arbitrarily up to magnitude of pi.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a phase conversion element used in the optical information processing industry, which targets devices that utilize technology for processing optical information in parallel.

[Summary of the invention]

In the phase conversion element according to the present invention, a counter transparent electrode is formed in a specific region of a parallel plane perpendicular to the optical axis of an electro-optic crystal, and an optical film thickness of the counter electrode is formed in a $■ region of the parallel plane other than the specific region of the parallel plane. a transparent thin film having an optical thickness equal to , further comprising means capable of applying a voltage at least equal to a half-wave voltage of the electro-optic crystal used between the opposed transparent electrodes, and a half-wavelength By providing means for making linearly polarized light that is polarized in the direction of the principal axis of the refractive index ellipsoid of the electro-optic crystal used when a voltage is applied parallel to the optical axis of the electro-optic crystal used, optical image information, etc. The phase of a specific region of the wavefront of parallel optical information and other regions can be made to differ by a small amount (π), and the sign of the amplitude can be changed. This makes it possible to arbitrarily perform sum or difference calculations, and provides an optical active element that is effective in the field of parallel optical information processing.

[Conventional technology]

Conventionally, optically active devices that change the phase of light and are used have been used in many applications such as liquid crystal devices, Pockels cells, Kerr cells, and Faraday cells.

However, most of these optically active devices are used as light intensity modulation devices in combination with polarizing elements, and they are not intended to actively apply the phase change itself. As a phase conversion element that attempts to modulate the
[Applied Physics Letters 2.401963]
) (Appl, Phys, LeLL, 2.41(
(1963)), a glass plate with an appropriate optical path length has been used.

[Problems to be Solved by the Invention] However, conventional phase conversion elements, especially phase conversion elements that actively try to modulate the change in phase themselves, cannot convert the phase of only a specific region of the wavefront of parallel optical information. This requires complex processing in which only a specific region of the wavefront of the parallel optical information is branched out, phase-converted, and then combined with a region of the wavefront that is not phase-converted. This method has the problem of requiring extremely precise mechanical positioning in order to adjust the amount of conversion.

[Means to solve the problem]

In the phase conversion element according to the present invention, a counter transparent electrode is formed in a specific region of a parallel plane perpendicular to the optical axis of an electro-optic crystal, and a counter transparent electrode is formed in a parallel plane region other than the specific region of the parallel plane with an optical thickness equal to the optical film thickness of the counter electrode. A transparent thin film having an optical thickness is formed, further comprising means capable of applying a voltage at least equal to a half-wavelength voltage of the electro-optic crystal used between the opposed transparent electrodes, and a half-wavelength voltage is applied between the opposed transparent electrodes. Means is provided for making linearly polarized light, which is polarized in the direction of the principal axis of the refractive index ellipsoid of the electro-optic crystal used when it is applied, incident parallel to the optical axis of the electro-optic crystal used.

(Function) With the above configuration, phase conversion of a specific region of the wavefront of parallel optical information can be realized without using complicated means such as branching and coupling, and the voltage applied between the facing transparent electrodes in the present invention can be realized. By simply controlling the magnitude of , the amount of phase shift can be arbitrarily controlled up to at least the magnitude of π, thus solving the above problem.

〔Example〕

Embodiments of the phase conversion element according to the present invention will be described below with reference to the drawings. FIG. 1 is a principle diagram of the phase conversion element according to the present invention, in which 1 is an electro-optic crystal, 2 is a facing transparent electrode,
3 is a transparent Fj film, 4 is a polarizer, 5 is a high voltage source, 6 is a switch, 7 is the principal axis of the refractive index ellipsoid when a half-wave voltage is applied, 8 is the crystal axis of the electro-optic crystal 1, and 9 is the incident light. be. Electro-optic crystals include KHz PO4, KDt POa, NH
a Hz PO-ZnS, Zn5e, CdS, GaAs
, BaTi0a, LiNboi, LiTaos, KTi
OPO4, quartz, etc. can be used, but in this example, a case will be described in which KHl PO is used as the electro-optic crystal. As shown in Figure 1, K Hz P O
Since the optical axis of a coincides with the crystal C axis, KHl PO was cut and polished in a parallel plane perpendicular to the crystal C axis, that is, parallel to the plane defined by the crystal a axis and the crystal a axis.

The size of the crystal C plane is 15fl x 30n and the thickness is 5
+u, and the transmitted wavefront precision of the parallel plane was set to λ/20 (however, λ-633 nm).Also, in order to adjust the optical system capacitively, the remaining parallel planes were set to the principal axis of the refractive index ellipsoid when a half-wave voltage was applied. It was cut parallel to the X and Y axes of 7. Note that the angle between the X axis of the principal axis 7 of the refractive index ellipsoid and the a axis of the crystal axis 8 when a half-wave voltage is applied is 45 degrees. Next, approximately 1,600 ITO (a compound of indium oxide and tin oxide) was formed as a counter transparent electrode 2 on half of the parallel plane perpendicular to the C axis of the crystal axis 8 using reactive vapor deposition. As the counter transparent electrode 2, indium oxide, M-tin oxide, zinc oxide, etc. may be used in addition to ITO. A transparent thin film 3 was formed on the soil surface by vacuum evaporation. The transparent thin film 3 may be formed only on one side of a parallel plane perpendicular to the C axis of the crystal axis 8, or may be formed on both opposing sides. When forming, it is formed so that the optical film thickness is equal to the sum of the optical film thickness of each of the two opposing transparent electrodes 8.Normally, the two opposing transparent electrodes 8 are formed with the same film thickness. , the film thickness of the opposite transparent rod 8 is d, the refractive index is n, and i! When the film thickness of the I film 3 is d and the refractive index is n, then d-2d @ n i
C of crystal axis 8 should be formed so that i / n
When the transparent thin film 3 is formed on opposite surfaces perpendicular to the axis and parallel to each other, the thickness of the transparent thin film 3 formed on each surface is d
．． When d-den2, d-'In@, (d-den, +d-den2)
The transparent thin film 3 may be formed to a thickness such that n=n electrodes so that the light transmittance of the surface on which the transparent electrode 8 is formed is equal.

It is preferable to use d-power or wd-power. In this example, n
= S10 was used as the material of the transparent thin film 3 to make it n-electric, but Yt Os, A 1 z Os, P b
Materials such as Fz, CeF, Tiot, and Zr0z can be used. Further, the thickness of the transparent thin film 3 in this example was approximately 1600. As the polarizer 4, a Glan-Thompson prism or a Glantiller prism using calcite, or a polarizing beam splinter using an optical multilayer film can be used. In this embodiment, a Glan-Thompson prism using calcite is used, and the polarizer 4 y5
It was installed so that the polarization plane of the light after the irradiation was parallel to the X-axis of the principal axis 7 of the refractive index ellipsoid when a half-wave voltage was applied. High voltage electric 1ll
For X5, use a DC power supply that can apply up to 10kV,
K.H., P.O.

The voltage applied to the opposing transparent electrode 2 was set to 0N10FF using the switch 6 so that a half-wavelength voltage of 7.6 kV could be output. In order to accurately apply a half-wave voltage, the phase conversion element according to the present invention is inserted into a laser interferometer, and the surface on which the opposing transparent electrode 2 is formed and the transparent thin film 3 are separated.
The transmitted wavefront phase with respect to the surface on which was formed was measured, and the applied voltage necessary to make the difference by π was set as the output of the high-voltage power supply. At this time, in the laser interferometer, the surface on which the opposing transparent electrode 2 is formed and the transparent FIII! The laser return light intensity differs depending on the surface where 3 is formed. The laser return light intensity ratio (hereinafter referred to as brightness ratio) on each surface changes depending on the voltage φ applied between the opposing transparent electrodes 2.

Figure 2 shows this change. As can be seen from FIG. 2, when the phase conversion element in this embodiment is inserted into an interferometer, the applied voltage at which the brightness ratio of the surface where the opposing transparent electric bridge 2 is formed and the surface where the transparent thin film 2 is formed is equal exists at zero volts; It can be seen that the phase is shifted by π at 7.6 kV.

In addition, when the phase conversion element of the present invention is used in a laser optical system, the polarizer 4 is unnecessary by making the polarization plane of the laser beam coincide with the X axis or Y axis of the principal axis of the refractive index ellipsoid when a half-wave voltage is applied. Become.

Next, an example of the principle of performing parallel optical information processing using the phase conversion element of the present invention will be described. FIG. 3 is a diagram showing the principle of parallel optical information processing using the phase conversion element of the present invention.
11 is a phase conversion element of the present invention, 11 is a Fourier transform lens,
12 is first input information, 13 is second input information, and 14 is output information. In FIG. 3, a high voltage fil! is applied to the opposing transparent electrode 2 of the phase conversion element 10 of the present invention. 5, when no applied voltage is applied, when the parallel optical information a is manually inputted as the first input information to the formation surface of the transparent thin film 3, and the second input information s is inputted to the formation surface of the counter transparent electrode 2, a, Even after b passes through the phase conversion element 10 of the present invention, no phase difference occurs, and the intensity distribution of F as the output information 14 after being Fourier transformed by the Fourier transformation lens 11 is Fl''=(lA
l”+lBl”+lnl”+2Re (A” B)+
2Re (B”p)+2Re (A”n))(e
xρ(iψ). Here, n is information noise, ψ is the phase caused by the input positions of input information a and b, Al), Be
, n= are the complex conjugates of A, B, and n, respectively, Re (A
"B), Re(B"n), and Re(A"n> are the real parts of A"B, B"n, and A"n, respectively.Next, the opposing transparent electrode 2 of the phase conversion element 10 of the present invention When a half-wave voltage of the electro-optic crystal used is applied by the high-voltage power source 5 by turning on the switch 6 to the formation surface of the transparent thin film 3, parallel optical information a is inputted as the first input information to the formation surface of the transparent thin film 3, When b is input as the second input information to the forming surface of the opposing transparent electrode 2, a and b are the phase conversion element 1 of the present invention.
0, a phase difference of π occurs, and the output information after being Fourier transformed by the Fourier transform lens 11 is F.
', the intensity distribution is IF'= (IAI" +l
Bl" + ln'l"-2Re(A" B) -2R
e (B"n')-2Re (A"n'))
exp(iψ), where n' is information noise. If you electrically or optically subtract lF+" and +F"l, you get nun', so 4Re (A" B
)+4Re(A” n)+4Re(B” n) information. Here, since A''n and B''n are often sufficiently small compared to A''B, this information is essentially 4Re(A
'''B) In other words, it becomes cross-correlation information between the first input information I'lla and the second input information.In this way, by using the phase conversion element of the present invention, it is possible to calculate the sum of the correlation strengths of the two parallel optical information.・It has an excellent function of easily performing subtraction while minimizing information noise.An optical correlation process similar to this can be found in Japanese Unexamined Patent Publication No. 138616/1982, but it is possible to use the phase conversion element according to the present invention. This makes it possible to reduce the influence of autocorrelation and information noise in optical correlation processing.Also, as an input method for the first input information I [112 and the second input information 13, a liquid crystal display element, a magneto-optical display element, or Using an electrochromic display element and COD as a detection element for output information a14,
By using IF+" and IF'l' detected by the COD as direct input information 12 and second input information 13 for the tube 1, it is also possible to add and subtract parallel optical information quasi-optically.

〔Effect of the invention〕

As described above, in the phase conversion element according to the present invention, the opposing transparent electrode is formed in a specific area of the parallel plane perpendicular to the optical axis of the electro-optic crystal, and the opposing transparent electrode is formed in a parallel plane area other than the specific area of the parallel plane. forming a transparent thin film having an optical thickness equal to the optical thickness of the electro-optic crystal; When a half-wave voltage is applied to the electro-optic crystal, the parallel Since the phase of a specific region of the wavefront of optical information and other regions can be made to differ by at least π, and the sign of the amplitude can be changed, the sum or difference between a specific region of the wavefront of parallel optical information and other regions can be made to differ by at least π. This allows calculations to be performed arbitrarily, and in particular, if the phase conversion element according to the present invention is applied to optical correlation processing as seen in Japanese Patent Laid-Open No. 57-138616, information noise can be minimized and only cross-correlation information can be obtained. This has an extremely large effect on visual comparison of images in production factories.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram of the phase conversion element according to the present invention, and Fig. 2 is a diagram showing the relationship between the brightness ratio 1/I of the transparent thin film forming surface and the counter electrode forming surface within the interferometer and the applied voltage in the present invention. The explanatory diagram and FIG. 3 are diagrams showing the principle of parallel optical information processing using the phase conversion element of the present invention. 1... Electro-optic crystal 2... Opposing transparent electrode 3... Transparent thin film 4... Polarizer 5...High voltage power supply 6...Switch 7...Main axis of refractive index ellipsoid when half-wave voltage is applied 8...
Crystal axis 9...Incoming light 10...Phase conversion element 11 of the present invention...Fourier transformation lens 12...First input information 13...Second input information I4...Output information and above Applicant Seiko Electronic Industries Co., Ltd. Agent Patent Attorney Keiyuki Hayashi Mitsuaki Sukemoto Nibo 6th Place of Retaliation Principles National Affairs 1 Figure 13 2nd Entry 77 Practice

Claims (1)

[Scope of Claims] A counter transparent electrode is formed in a specific region of a parallel plane perpendicular to the optical axis of the electro-optic crystal, and a counter transparent electrode is formed in a parallel plane region other than the specific region of the parallel plane with an optical thickness equal to the optical film thickness of the counter transparent electrode. forming a transparent thin film with an optical thickness; further comprising means capable of applying a voltage at least equal to a half-wavelength voltage of the electro-optic crystal used between the opposed transparent electrodes; and applying a half-wavelength voltage between the opposed transparent electrodes; A phase conversion element characterized by having means for causing linearly polarized light that is polarized in the direction of the principal axis of the refractive index ellipsoid of the electro-optic crystal to be applied to the electro-optic crystal to be incident parallel to the optical axis of the electro-optic crystal to be used.