RU2326464C1 - Electro-optical converter - Google Patents

Abstract

FIELD: physics, optics.

SUBSTANCE: invention relates to the electronic equipment, in particular, to electro-optical image converters intended for spectral conversion, scaling, amplification, and temporal analysis of optical signals. The technical effect is achieved by the following: the distinguishing feature of the converter containing a flat photocathode, a focusing electrode, an anode, an electronic beam sweeping system, and a luminescent screen placed into a vacuum enclosure and located along the optical axis, is that a correction electrode in the form of a diaphragm with axially symmetric round opening is inserted into the space between the photocathode and the focusing electrode; the geometrical dimensions of the converter components are selected so as to meet the following ratios: 0.1≤l₁/l₂≤0.25; 1.25≤d₁/d_k≤1.83; 8≤(d₁-d_k)/l₁≤13; 5.4≤L/d_k≤6.8; 0.4≤D/L≤0.6 where: d_k is the operating diameter of the cathode, d₁ is the diameter of the correction electrode diaphragm opening, h is the distance between the photocathode and the diaphragm, l₂ is the distance between the diaphragm and the anode, L is the distance from the photocathode to the screen, D is the focusing electrode diameter.

EFFECT: decrease in image distortion and dimensions of electro-optical image converter.

2 cl, 3 dwg, 3 tbl

Description

Application area

The invention relates to electronic equipment, in particular to electron-optical image converters (image intensifiers) used for spectral conversion, scaling, amplification and temporal analysis of optical signals [H01J 31/50].

State of the art

The prior art patent [1] for an X-ray electron-optical converter. REOP consists of a shell with an entrance window and an input X-ray luminescent screen with a photocathode formed on its inner surface, electrostatic focusing electrodes, an anode and an output cathodoluminescent screen located inside it, the anode opening being covered by a conductive grid made in the form of a spherical segment with a radius of curvature R _c mounted coaxially with the photocathode at a distance L from the center of _ka, and the minimum cross section of the electron beam plane between a spherical segment and O dnym screen set the aperture at a distance from the center of the photocathode L _cr. The dependences for determining R _c , L _ka , L _cr . In a REOP with a quasispherical field, a 1.6-fold reduction in the distance between the photocathode and anode and a 2-3-fold increase in contrast were achieved.

The disadvantage of REOP are the large size of the device. Using such an image intensifier tube, it is impossible to register radiation in the ultraviolet region. In addition, a device with a spherical segment in comparison with flat glass is a much more expensive element of the device.

A patent is known for an image intensifier tube [2], which contains an electrostatic focusing system with a spherical photocathode, a focusing electrode, an anode, an electron beam scanning system, and a fluorescent screen. In this device, the photocathode is made on a substrate, which is a fiber optic plate (FOP), the outer side of which is flat and the inner is spherical. A photocathode is applied to the inside of the GP.

The photocathode is part of a focusing system that transfers an image to a fluorescent screen. Photocathode sphericalization is done in order to radically reduce the geometric distortions of the focusing system. Moreover, the device has small dimensions: Ф ~ 44 mm, length ~ 110 mm.

Currently, the materials used for the fabrication of VOPs (special glass fibers) limit the spectral sensitivity range of the image intensifier tube to the visible region of 400–800 nm. Using such an image intensifier tube, it is impossible to register radiation in the ultraviolet region. In addition, VOP in comparison with flat glass is a significantly more expensive element of the device. An analogue is a patent [3] for an image intensifier tube containing a photocathode, accelerating and focusing electrodes in the form of cylinders of the same diameter, an anode with a diaphragm, an image scanning system and a luminescent screen, characterized in that the anode is equipped with a cylindrical part with a certain ratio of diameter, electrode lengths and ratio the distance from the photocad to the screen. The accelerating electrode has a target diaphragm at the end facing the photocathode.

The disadvantage of the image intensifier tubes are the large size of the device. Using such an image intensifier tube, it is impossible to register radiation in the ultraviolet region.

A closer analogue is the patent for an image intensifier tube [4], which contains an electrostatic focusing system with a flat photocathode on a glass substrate, a focusing electrode, an anode, an electron beam scanning system, and a luminescent screen. The large dimensions of the device: 110 mm, length 360 mm allow using only the central part of the photocathode with a diameter of ~ 12 mm for operation. Due to this, it is possible to reduce the geometric distortion of the image.

The described design of an image intensifier tube with a flat photocathode allows the use of substrates that transmit radiation, including in the ultraviolet range, starting from 110 nm.

Reducing the size of the image intensifier while maintaining the working diameter of the photocathode leads to significant distortion due to image distortion.

The aim of the present invention is to provide a small image intensifier tube, which retains the ability to register radiation in the ultraviolet region of the spectrum without image distortion.

The technical result of the invention is to reduce image distortion and reduce the size of the device.

Brief Description of the Drawings

Figure 1 shows the scheme of the image intensifier tube, where 1 is the photocathode, 2 is the diaphragm, 3 is the focusing electrode, 4 is the anode, 5 is the electron beam scanning system, 6 is the luminescent screen, 7 is the vacuum shell.

Figure 2 shows a nine-frame image scan.

Figure 3 shows a photograph of the layout of the image intensifier tube made according to this invention.

SUMMARY OF THE INVENTION

The claimed technical result is achieved due to the fact that the image intensifier tube enclosed in a vacuum shell and placed along the optical axis: a flat photocathode, a focusing electrode, an anode, an electron beam scanning system, a luminescent screen, differs in that it is inserted into the space between the photocathode and the focusing electrode a correction electrode in the form of a diaphragm with an axially symmetric round hole, and the geometric dimensions of the image intensifier tubes are made in such a way that they satisfy the following relations :

0.1≤l ₁ / l ₂ ≤0.25

1.25≤d ₁ / d _k ≤1.83

8≤ (d _l -d _k ) / l ₁ ≤13

5.4≤L / d _k ≤6.8

0.4≤D / L≤0.6

where d _k is the working diameter of the cathode, d ₁ is the diameter of the hole of the diaphragm of the correction electrode, l ₁ is the distance from the cathode to the diaphragm, l ₂ is the distance from the diaphragm to the anode, L is the distance from the photocathode to the screen, D is the diameter of the focusing electrode. In the immediate vicinity of the fluorescent screen, a microchannel amplification plate can be installed, which allows you to amplify the output signal and get a better image on the fluorescent screen.

A distinctive feature of this invention is that an additional correcting electrode in the form of a diaphragm is inserted into the near-cathode area of the image tube with a flat photocathode, which, when certain ratios of the sizes of the elements of the electrostatic lens focusing the electron beam onto the luminescent screen are performed, reduces image distortion.

The ratios of the given sizes of the electrodes and the image intensifier tubes as a whole were obtained by computer simulation. The initial data for the calculations and the results are shown in table 1.

Table 2 shows the distortion values depending on the aspect ratio of the elements of the image intensifier tube.

From table 2 selected options that satisfy the ratios of the geometric dimensions of the image intensifier tubes shown in formulas 1-5 and are summarized in table 3.

The device operates as follows. All elements of the device are enclosed in a vacuum shell (7) (see Figure 1).

The investigated process, accompanied by optical radiation, is designed on the photocathode (1) of the image intensifier tube. Working electrodes are supplied to the electrodes (3) of the image intensifier tube. Under the influence of light, the photocathode (1) emits an electron stream. Electrons are accelerated towards the anode (4), pass through the hole in the anode and are focused on the luminescent screen (6). Thus, the image of the investigated process is transferred to the screen.

In the space between the anode (4) and the luminescent screen (6), the electron beam scanning system (5) is located, containing one or two pairs of mutually perpendicular deflecting plates.

By applying short electric pulses of a stepped form or a linearly increasing voltage to the scanning system (5), it is possible to obtain frame-by-frame or continuous scanning of an image on a luminescent screen (6). In this case, the spatio-temporal transformation of the investigated optical signal occurs. Knowing the duration of the sweep, you can measure the duration of the investigated optical process.

Thus, it is possible, while minimizing the geometric parameters of the image intensifier tube, to maintain high quality images.

As an example, figure 2 shows a nine-frame scan of the image on the screen of the image intensifier tube (when using a variant of the device with a scan system consisting of two pairs of deflecting plates).

Figure 3 shows an example of a mock working device made according to this invention. The flat substrate of the photocathode of this image intensifier tube is made of quartz glass, which provides transmission of radiation in the ultraviolet region of the spectrum, starting from 180 nm. Moreover, the device has the following dimensions: diameter 44 mm, length 80 mm, which is ~ 3 times in diameter and ~ 5 times smaller in length than the prototype. The diameter of the working field of the photocathode is ~ 12 mm, which corresponds to the prototype. If necessary, register radiation of low intensity in the immediate vicinity of the screen can be installed microchannel plate, which serves to amplify the current up to 10,000 times.

Table 1 d _k d _l l ₁ l ₂ D L Magnification ratio Distortion,% one. 12 eighteen 4,5 thirty 36 75 0.6 3 2. 12 17 4,5 thirty 44 75 0.6 2.7 3. 12 fifteen 4,5 thirty 40 75 0.6 3.6 four. 12 17 4,5 32 32 81.7 0.7 four 5. 12 16 4,5 31 36 92 0.8 5.5 6. 12 22 4,5 thirty 40 75 0.6 5.2 7. 12 17 4,5 thirty 40 83.7 0.88 6.4 8. 12 19 four 30.5 42 75 0.7 3.2 9. 12 17 2 32,5 36 75 0.6 5,6 10. 12 eighteen 7 27.5 36 75 0.6 3 eleven. 12 22 7 27.5 40 75 0.6 3.2 12. 12 17 1.4 30.6 42 72.5 0.68 9.3 13. 12 17 5 27 36 72.5 0.68 3,7 fourteen. 12 fifteen 3 29th 38 72.5 0.68 four fifteen. 12 17 2 27.5 36 70 0.7 5.9 16. 12 fifteen 3 26 36 65 0.64 3.8 17. 12 16 3 26.5 40 70 0.7 4.6

table 2 d _l / d _k l ₁ / l ₂ L / d _k D / L Distortion,% one 1,5 0.15 6.25 0.48 3 2 1.42 0.15 6.25 0.59 2.7 3 1.25 0.15 6.25 0.53 3.6 four 1.42 0.14 6.8 0.4 four 5 1.33 0.145 7.6 0.39 5.5 6 1.8 0.15 6.25 0.53 5.2 7 1.42 0.15 7 0.48 6.4 8 1,58 0.13 6.25 0.6 3.2 9 1.42 0.06 6.1 0.5 5,6 10 1,5 0.25 6.25 0.48 3 eleven 1.83 0.25 6.8 0.53 3.2 12 1.42 0.05 6.04 0.56 9.3 13 1.42 0.19 6 0.5 3,7 fourteen 1.25 0.1 6 0.55 four fifteen 1.42 7.3 5.8 0.63 5.9 16 1.25 0.115 5,4 0.55 3.8 17 1.33 0.11 5.8 0.57 4.6

The criterion for the suitability of the obtained ratios was the distortion value not exceeding 4%.

Table 3 d _l / d _k l ₁ / l ₂ L / d _k D / L Distortion,% one. 1,5 0.15 6.25 0.48 3 2. 1.42 0.15 6.25 0.59 2.7 3. 1.25 0.15 6.25 0.53 3.6 four. 1.42 0.14 6.8 0.41 four 5. 1.42 0.13 6.25 0.59 3.2 6. 1,5 0.25 6.25 0.48 3 7. 1.83 0.25 6.8 0.53 3.2 8. 1.42 0.19 6.04 0.5 3,7 9. 1.25 0.1 6 0.55 four 10. 1.25 0.115 5,4 0.55 3.8 eleven. 1.33 0.11 5.83 0.57 four

INFORMATION SOURCES

1. RF patent No. 2019882.

2. Patent for utility model of the Russian Federation No. 444874.

3. A.S. USSR No. 1100655.

4. A.S. USSR No. 868884.

Claims (2)

1. An electron-optical image converter containing enclosed in a vacuum shell and placed along the optical axis: a flat photocathode, a focusing electrode, an anode, an electron beam scanning system, a luminescent screen, characterized in that a correction electrode is inserted into the space between the photocathode and the focusing electrode a diaphragm with an axially symmetric round hole, and the geometric dimensions of the elements of the electron-optical transducer are made in such a way that satisfying the following relationships: 0.1≤l ₁ / l ₂ ≤0.25; 1.25 d d ₁ / d _k 1 1.83; 8≤ (d _l -d _k ) / l ₁ ≤13; 5.4≤L / d _k ≤6.8; 0.4≤D / L≤0.6, where d _k is the working diameter of the cathode, d ₁ is the diameter of the aperture of the correction electrode, l ₁ is the distance from the photocathode to the diaphragm, l ₂ is the distance from the diaphragm to the anode, L is the distance from the photocathode to the screen, D is the diameter of the focusing electrode. 2. The electron-optical image converter according to claim 1, characterized in that in the immediate vicinity of the luminescent screen, an amplification microchannel plate is installed.

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