RU2344499C2 - Device of night viewer protection against optical interference - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention is intended for protection of night viewers against optical interference of ultraviolet, visible and infrared range and may be used in flights or movements of night viewer carriers for provision of carriers orientation in space, masking and exclusion of flare lights by visible and infrared radiation during nighttime. Invention comprises night viewer and channel for optical interference measurement and generation of control signal. Night viewer contains optically connected lens, electrochromic filter, electron-optic converter, eyepiece. Measuring channel includes serially optically connected microscope objective and beam-splitting mirror, reference source of radiation in the form of impulse light diode, matrix photodetector, at that reference source of radiation is electrically connected to pulse generator, creating introduced channel of reference signal formation. Matrix photodetector is electrically connected via introduced multi-channel comparison circuit with introduced multi-channel shaper of control voltage, which comprises multi-channel commutator. Pulse generator is connected with its first output to pulse light diode, and with its second output - to multi-channel comparison circuit, and multi-channel shaper of control voltage is connected via multi-channel commutator with electrochromic filter, at that electrochromic filter is installed in focal plane of night viewer objective, directly joining instrument phototube cathode. Matrix photodetector and electrochromic filter are made in the form of matrices with size of nxn elements, at that every element of electrochromic filter has autonomous electric control of optical interference radiation transmission coefficient.

EFFECT: provision of night viewer against optical interference that create illuminance at the inlet to device objective, which exceeds specified threshold value, without interruption of observation process.

3 cl, 6 dwg

Description

The proposed device relates to devices for protecting night vision devices from optical interference of ultraviolet, visible and infrared ranges.

The aforementioned device is used during flights or movements of night-vision device carriers to ensure carrier orientation in space, mask and eliminate spurious illumination by visible and infrared radiation in the dark.

The following methods and devices for protecting night vision devices from optical interference of visible and infrared radiation are known:

a) protective devices with additional illumination of photochromic material [1, 2];

b) dynamic attenuators on liquid crystals based on the use of the twist effect and with local modulation [3-5];

c) devices based on the use of ferroceramic materials [6, 7];

d) optical devices based on translucent or reflecting spatio-temporal light modulators [8, 9] - and others.

The disadvantages of the known methods and devices for protecting night vision devices are the large mass and dimensions, low speed and low transmittance in the absence of interference, insufficient dynamic range of brightness variation of optical noise sources, failure to provide reliable protection in a wide spectral range, high cost.

As a prototype, the authors chose a device for protecting the organs of vision [1] as the closest in technical essence. The disadvantages of the prototype indicated above.

The purpose of the invention is the elimination of the above disadvantages and the protection of the night vision device from optical interference, creating in the plane of the inlet of the lens illumination of more than 1 lux (lux), without interrupting the observation process.

To achieve this goal, a night vision device equipped with an optical filter made of electrochromic material (hereinafter referred to as the electrochromic filter), which changes its transmittance of optical radiation under the influence of a control voltage, is additionally equipped with a measuring channel that generates a control signal for the electrochromic filter.

Figure 1 shows the functional diagram of the proposed device. The device consists of a night vision device I and a channel for measuring optical interference and generating a control signal II. The night vision device I contains a series-optically connected lens 1, an electrochromic filter 2, an electron-optical transducer 3 and an eyepiece 4 (5 - the organ of vision). The measuring channel II includes a sequentially optically coupled micro-lens 6 and a beam splitting mirror 7, a reference radiation source 8 in the form of a pulsed LED, a matrix (position-sensitive) photodetector 9, while the reference radiation source 8 is electrically connected to the pulse generator 10, forming a formation channel reference signal; the matrix photodetector 9 is electrically connected through a multi-channel comparison circuit 11 with a multi-channel control voltage driver 12, including a multi-channel switch 13, the pulse generator 10 being connected to a pulse LED 8 by its first output and to a multi-channel comparison circuit 11; a multi-channel driver of control voltage 12 is connected through a multi-channel switch 13 with an electrochromic filter 2.

Figure 2 shows the electric circuit of an electrochromic filter 2, electrically connected to a multi-channel switch 13.

The device operates as follows. The visible Ф _ν and infrared Ф _е optical interference radiation Ф _п = Ф _ν + Ф _е falls simultaneously in the field of view of the night-vision device I and at the input of the measuring channel II. The night-vision device generates at the output of the eyepiece 4 an image of the interference source, which leads to “spreading” of the image on the screen of the electron-optical converter 3 and subsequent full illumination of the screen due to saturation of the photocathode of the electron-optical converter 3. Thus, the image of the surrounding space at the output of the night-time device Vision I completely disappears. Measuring channel II is designed to eliminate the consequences of this phenomenon. The luminous flux of the interference source Φ _n = Φ _ν + Φ _e through the micro-lens 6 and the beam splitting mirror 7 falls into a certain place in the matrix of sensitive elements of the matrix photodetector 10, for which, for example, a charge-coupled device is used. The matrix photodetector 9 consists of nxn sensitive elements and is configured for a threshold illumination E _pore = 1 lx, above which the protection of the night-vision device should be activated I. To this end, the threshold illumination is set by a reference radiation source in the form of a pulsed LED 8, controlled by a pulse generator 10, which is connected by its second output to a multi-channel comparison circuit 11, to which a reference signal with a negative sign is supplied - -u _e corresponding to the threshold illumination E _por = 1 lux matrix phot receiver 9. The pulse repetition rate of the reference radiation source 8 should not interfere with the operation of the night vision device and therefore is selected from the condition: f = (3 ... 5) τ _NVD ,

where τ _NVD is the time constant of the night vision device. The main input of the multi-channel comparison circuit 11 receives the total signal u _Σ equal to the sum of the voltage u _T corresponding to the current illumination from optical interference and the voltage u _e corresponding to the threshold illumination E _POR = 1 lux:

Thus, at the output of the multi-channel comparison circuit 11, a signal is generated proportional to the current illumination of the night-vision device I:

The signal (1) enters the multi-channel driver of the control voltage 12, in which the control signal u _y is generated, which then passes through the multi-channel switch 13 to the electrochromic filter 2 with an electrically controlled spectral transmittance function and changes its transmittance in such a way that completely eliminates the effect of optical interference and allows you to observe the image of the surrounding space without luminance distortion caused by interference.

The electrochromic filter 2 is an electrochromic material of a rectangular rectangular shape in the solid or liquid phase, having a matrix structure of size nxn elements, in accordance with the dimensions of the matrix photodetector 9, also having nxn sensitive elements, each of which has autonomous electrical control of the transmittance of the optical noise. It is installed in the focal plane of the lens 1 and allows local dimming of that portion of the field of view of the night vision device I onto which the optical interference image is projected. The corresponding element of the electrochromic filter is turned on by a multi-channel switch 13 according to the signals of the multi-channel driver of the control voltage 12.

Figure 3 shows a diagram illustrating the correspondence of the number of the element of the image (i, j) of optical interference in the plane of the sensitive elements of the matrix photodetector 10 to the number of the element (i, j) of the electrochromic filter, which changes its transmittance (n _g , n _in is the number of elements of the matrix photodetector and electrochromic filter horizontally and vertically, respectively).

It was experimentally established that the optimal illumination of the inlet of the lens 1 of the night vision device II should not exceed 1 lux. To do this, the measuring channel is illuminated by a reference radiation source in the form of a pulsed LED 8, which creates a threshold illumination E _pore = 1 lux in the plane of the photodetector 9. If the threshold level of illumination is exceeded - E _t > E _then the transmittance of the electrochromic filter decreases to a level that provides optimal observation conditions:

where E _opt is the optimal illumination of the entrance pupil of the lens 1 of the night vision device I; τ _y - controlled transmittance of the electrochromic filter; E _t - the current value of the illumination of the entrance pupil of the lens 1 of the night vision device I.

From the formula (2)

when E _opt = 1 lux; k = 1 lux ^-1 - coefficient of coordination of dimension.

Figure 4 presents the calculated dependence of the transmittance of the electrochromic filter on the amount of illumination in the plane of the matrix photodetector 10.

Figures 5, 6 show typical calculated dependences of the transmittance of the electrochromic filter 2 on the magnitude of the control voltage and the law of change in the control voltage with increasing illumination of the night-vision device I by optical interference radiation.

In the inventive device, therefore, it is proposed to use an optical filter of electrochromic material:

1) the electrochromic filter is made in the form of a mosaic structure, each element of which has autonomous electrical transmission coefficient control depending on the position of the optical noise source in the field of view of the night-vision device;

2) the electrochromic filter is not installed in front of the lens, as in the known devices [1, 2], but behind it, in the focal plane of the lens, which ensures focusing of the optical noise source at a certain point in the field of the image being generated; this does not lead to undesirable illumination of the entire field of view and ensures continuous operation of the electron-optical converter, regardless of the presence of interference;

3) a measuring channel is introduced into the device, consisting of a coordinate-sensitive matrix photodetector and a control voltage generating circuit supplied to the corresponding element of the electrochromic filter; as a result, there is a sharp decrease in the transmittance of this element by a time equal to the duration of the interference; at the same time, the remaining field of view of the device remains transparent, which allows you to observe the image of the surrounding space with a given quality.

Thus, the above-described device for protecting the night vision device from optical interference allows to achieve the purpose of the invention, namely: to protect the night vision device from optical interference that creates illumination at the entrance to the device’s lens that exceeds a predetermined threshold value without interrupting the observation process. In this case, the interference acts locally and only briefly incapacitates only a small part of the field of view of the device, and in the rest of the field of view, the protection provides the specified range and the image quality.

Literature

1. Barachevsky V.A., Vasilevsky O.N., Suschev G.A. et al. Extension of the light range of television cameras using electrochromic filters // Technique of Communications. Ser. Technique of television. - 1981. - Issue 2. - S.13-18.

2. Barachevsky V.A., Lashkov G.I., Tsekhomsky V.A. Photochromism and its application. - M .: Chemistry, 1977 .-- 280 p.

3. Sci. New. Lett., 1965, v. 88, No. 4, p. 55; Missiles Rockets, 1966, v. 18, No. 17, p. 23.

4. Itseleva L.N., Polushkin D.Yu., Sikharulidze D.G. et al. Light-protective glasses based on liquid crystals // OMP. - 1990. - No. 1. - S.38-40.

5. Blinov L.M. Electro and magneto-optics of liquid crystals. - M .: Nauka, 1978.- 384 p.

6. Brezhnev V.A., Garfinkel B.I., Dolgopoliy Yu.E. and other Perspectives of passive-matrix liquid crystal screens and high-speed shutters // Electron. industry. - 2002. - No. 1. - S.14-24.

7. Pat. UK No. 2128362A, 1984 // Bull. VNIIIPI. - 1984. - 107-12-84.

8. Europatent No. 0436845, 1989 // Bull. VNIIIPI. - 1989 - No. 29. - 91-07-17.

9. Tomilin MG, Danilov VV, Optical devices on liquid crystals to protect the observer from glare radiation sources // OMP. - 2004. - No. 2. - S.14-24.

Claims (3)

1. A device for protecting night-vision devices from optical interference, comprising a measuring channel including a micro lens and a photodetector, and an electrochromic filter, characterized in that a channel for generating a reference signal is included in it, including optically coupled beam splitting mirror and a reference radiation source electrically connected to the pulse generator, and the photodetector of the measuring channel is made in the form of a matrix (position-sensitive) photodetector of radiation cal interference, forming a control signal depending on the power and coordinate the interference optical image in the plane of the sensitive elements of the photodetector matrix are electrically connected via a measuring channel introduced into the path comparison circuit multichannel, multi-control voltage generator and with a multichannel switch electrochromic filter; in this case, the pulse generator is connected by its first output to a reference radiation source, and by a second output to a multi-channel comparison circuit. 2. The device according to claim 1, characterized in that the electrochromic filter is installed in the focal plane of the lens of the night-vision device and is directly adjacent to the photocathode of the device. 3. The device according to claim 1, characterized in that the matrix photodetector of optical interference radiation and an electrochromic filter are made in the form of matrices of size nxn elements; wherein each element of the electrochromic filter has an autonomous electrical control of the transmittance of the radiation of optical interference.

Images