SU805239A1 - Controlled transparency - Google Patents

Description

(54) MANAGED TRANSPARANT

I

The invention relates to a technique for controlling optical radiation, in particular, the spatial and temporal modulation of light. Spatio-temporal light modulators or controllable transparencies (UT) are used in optical information processing systems as page generators, tunable filters, for encoding, decoding, and displaying information.

Controllable transparencies based on electro-optical ceramics are known (1.

Their disadvantages are low contrast and switching heterogeneity.

The closest in technical essence and the achieved result to the proposed is controlled. A translucent containing a plate of electro-optical ceramics with transparent electrodes in the form of vertical and horizontal stripes placed on opposite plates 2.

The disadvantage of it is a small amount of contrast, due to the fact that the matrix control organization is inherent in the presence of crosstalk. They are expressed in the fact that the voltage on the unselected

cells can reach half the voltage applied to the selected element (i.e., the half-voltage). Since ceramics has an accumulation effect, repeated exposure to the half-voltage will cause the element in the off state to tend to the on state.

The purpose of the invention is to increase the contrast.

This is due to the fact that a controlled ceramic plate containing a plate on electro-optical ceramics with transparent electrodes in the form of vertical and horizontal strips placed on opposite planes is introduced into the second ceramic plate with transparent electrodes in the form of vertical strips, whose thickness is 1.26 -1.34 times the thickness of the first plate, while the second plate is located in series with the first so that the vertical electrodes are arranged symmetrically on the outer planes of the plate and in pairs electrically interconnected, and between the plates on their inner planes are placed

transparent horizontal electrodes in the form of strips.

FIG. I shows an example of the proposed transparency device; in fig. 2 - the same, front view; in fig. 3 is a diagram of ceramics switching | in fig. 4 shows the modulation characteristic of a controllable transparency.

The controllable transparency consists of a ceramic plate 1, on the plane of which vertical transparent electrodes are arranged in the form of strips 2. In series with the first plate is placed a second ceramic plate 3 with vertical transparent electrodes in the form of strips 4. The thickness of the second plate is 1.26 - 1, 34 times more than the first. The vertical electrodes are arranged symmetrically and are electrically interconnected in pairs. Horizontal transparent electrodes in the form of strips 5 are placed between the plates on their inner planes. The intersection of the vertical and horizontal electrodes forms a matrix of switchable elements 6.

The device works in the following way. To reset the selected element to the on state, a voltage Ui 2Ec-de is applied to the electrodes, where d is the voltage. tire second plate. When polarization P ceramics reaches saturation, and then when removing, the voltage of the residual polarization value increases PI. The condition corresponds to point 7 in FIG. 3. In this case, omission of the maximum. The element is switched to the off state by applying voltage U4 -Ec-d to the electrodes. Ceramics in the first plate, whose thickness is Y |, changes to the state with PO, which is characterized by minimal light transmission. If then the element of the half-sampling is applied to this element, then the polarization will move to some intermediate state between P O and P Pc and not P (point 8 in Fig. 3). In the case of a single plate, this will cause the light transmittance of the switched off element to increase somewhat, which will lead to a decrease in contrast. When pulses of half-sampling are repeatedly applied, the polarization will take on successively decreasing values, which will lead to an even greater decrease in contrast. The presence of a second plate results in a reduction in contrast. Since the thickness of the second plastiy is larger, with the same voltage value on the plates, the field value in the second plate will be less than in the first one. Therefore, .1 (the first plate goes into the “off” state (P 0), Tr in the second polarization PI will take some intermediate between Р РЦ and Р О Зиacheие + PI (point 9). When exposed to half-sampling pulses, the value of Р will decrease , approaching the P O value, which will lead to a decrease in light transmission. Thus, an increase in light transmission in the first plate {in the "Off" state

will be compensated by a decrease in the second, i.e. the contrast value will remain unchanged.

The ratio of the thicknesses of the first and second plates is chosen in such a way that when the intensity under the action of the first

On the plate, increasing, will reach a maximum, under the action of the second, it will reach a minimum; This is illustrated in FIG. 4, which shows the dependence of intensity 1 on voltage. Here the curve is 10 -11 - 12 -

, 13 corresponds to the first plate, and the curve 10-14-15-16 is the second. The total effect of the plates will correspond to the curve 10-11 - 12-15-16. Since the intensity is minimal at E 4,6 KB / CM, and the maximum is reached at

value, 8 - 6.2 kV / cm, i.e. Eg / E, 1.26--1.34 yi. Since the voltage on both plates is the same, the thickness ratio dj / dr must also lie within 1.26-1.34.

Thus, the use of the second plate1 | 1 significantly increases the contrast in the UT. So, if we consider a transparency with a capacity of 10 X 10 elements, then the number of half-sampling pulses can reach a value of 10. In the case of a single plate, this results in a contrast ratio of less than 0.1 of the maximum possible value. The presence of the second plate will make the contrast almost independent of the effect of the half-sampling voltage, which will lead to a more than tenfold increase in contrast compared with the known devices. This is of great importance for optical information processing systems.

The independence of contrast from the number of half-pulse pulses does not limit the capacity of the UT. The absence of crosstalk significantly increases the reliability of the systems in which UT is used. If the UT is used in a holographic storage device, the probability of false information appearing in reading is reduced. When UT is used to display, the clarity and distinction of the displayed data is enhanced. The absence of crosstalk also simplifies the control circuitry because

does not require the creation of additional measures that reduce interference. All this greatly increases the efficiency of the UT and the system as a whole, simplifies its operation.

Claims (2)

1. US patent number 3945715. class. 350-150. 1976. 2.Drake M. D. PLZT Matrix-Type Blok Data Compozers. Appl. Optics.v. 13. 1974. No. 7. p. 347-352 (prototype). Fi.2