RU32347U1 - Camera based on a photodetector CCD - Google Patents

Description

A CAMERA BASED ON A PHOTONRIUM NZS MATRIX

The utility model relates to the field of image signal conditioners that are sensitive to visible and near-field RH radiation, and can be used in video monitoring and surveillance systems, as well as in applied television systems designed to operate in a wide range of illumination conditions of the observation object.

Currently, to adapt cameras to changing light conditions, either an electronic system for automatically adjusting the exposure of a photo-receiving CCD matrix is used, or a system

automatic lens iris adjustment. While

Using these systems, self-oscillations resulting in

to flickering images. To eliminate this phenomenon, the camera design provides for the separate use of either an automatic exposure control system or an automatic iris adjustment system. The choice of adaptation method is carried out by the operator using a special switch when installing the 1.2 camera.

The closest analogue is a camera 3 based on a photodetector of a CCD matrix, used in a vehicle and which protects the driver’s eyes from blinding due to anti-blooming, which limits the signal from oncoming headlights and eliminates the spread of charge in the CCD matrix. Such a camera contains a lens located in its focal plane, a CCD photodetector array with an anti-blooming device, a diaphragm with a control unit located between the lens and a CCD photodetector, connected in series with the video signal amplification and processing unit, and a video control unit

2003111308

ISh1111v1111shsh1111111111111111

,; r o o 3 1 1 1 3 o

IPC N 04 N 5/235, 5/335

the device (VKU), as well as the matrix control unit connected to the control buses of the photodetector CCD matrix. To ensure operability at any time of the day with arbitrary average illumination, this camera also contains a block for generating the average value level for analyzing the current image, the input of which is connected to the output of the amplification and video signal processing unit, and the output to the input of the matrix control unit and the input of the aperture control unit. This camera for adapting to changing light conditions has two automatic control loops: exposure and aperture. The automatic exposure control circuit consists of a photodetector CCD with an anti-blooming device, a video signal amplification and processing unit, an average value generating unit for analyzing the current image relative to the white level and the matrix control unit. The radiation flux analyzer is a photodetector CCD. The response time of the circuit is not more than 20 ms. The automatic iris control loop consists of the same units, but instead of the matrix control unit, does it include the diaphragm control unit, which is a high-precision electromechanical device designed to linearly change the diaphragm size. The radiation flux analyzer is a photodetector CCD. Contour reaction time is tenths of a second. The automatic exposure control circuit and the automatic iris control circuit are interconnected by a control signal — the output signal of a video signal amplification and processing unit, and by a radiation flux analyzer — a photodetector CCD, which under certain conditions can lead to self-oscillations in the system that cause the image to flicker . The automatic diaphragm control system is a linear system of automatic control and requires the use of a high-precision electromechanical drive for its implementation, which makes such systems quite expensive and demanding in operating conditions, especially

W € /// SH

specific to operating conditions, especially when operating in the temperature range below minus 10 ° С.

The objective of the utility model is to create a camera based on a photodetector CCD with improved performance, without the use of electromechanical elements for adjusting the radiation flux.

EFFECT: simplified design, increased reliability in a wide range of operating conditions and reduced cost of the camera is achieved by replacing a high-precision linear electromechanical diaphragm drive with a simpler, cheaper and less critical to the operating conditions optical variable-density filter, reversibly changing transmission depending on illumination and duration of exposure.

This is achieved by the fact that the composition of the well-known camera based on a photodetector CCD matrix including a sequentially located lens, an aperture diaphragm, a photodetector CCD matrix with an anti-blooming device located in the focal plane of the lens, as well as a video signal amplification and processing unit and the photodetector CCD control unit, the output of which is connected to the CCD control buses of the CCD, an optical filter of variable density is additionally installed in front of the lens.

In addition, this optical filter is also a protective glass.

The invention is illustrated in the drawing, which shows a block diagram of the proposed camera with an optical filter.

The camera contains a lens 1, in the focal plane of which is a photodetector CCD-matrix 2 with an anti-blooming device. A video signal amplification and processing unit 3 is connected to the output of the photodetector of the CCD matrix 2, and an input of the matrix control unit 4 is connected to the output of the block 3, the output of which is connected to the control buses of the photodetector of the CCD matrix 2. An optical filter of variable density 5 is located in front of the lens 1, which changes transmittance depending on the intensity of the radiation flux incident on it due to the physical processes occurring in it.

The device operates as follows. The radiation transmitted through the optical filter 5 is focused by the lens 1, which forms an image on the photodetector CCD matrix 2. In each of the cells of the photodetector CCD matrix 2, charges are proportional to the radiation intensity and accumulation time determined by the matrix control unit 4. Charges from a powerful blinding the source overflows the capacity of the cell drive, the excess charge merges into anti-blooming, which leads to the limitation of the signal charge remaining in the cell drive. The output signal of the photodetector of the CCD matrix 2 (video signal) after being limited to anti-blooming is linearly amplified by the amplification and processing unit of the video signal 3, is formed into a standard video signal in accordance with GOST 7845-92 or in the CCIR, PAL, EIA, NTSC standards and through the standard output connector of the camera It is broadcast on standard devices for displaying and documenting video information (video monitoring device, VCR, etc.). At the same time, the video signal from the output of the amplification and processing unit of the video signal 3 is fed to the input of the matrix control unit 4, which controls the exposure by changing the charge accumulation time in the cells of the photodetector of the CCD matrix 2. When the illumination increases in the plane of the photodetector of the CCD matrix 2, the exposure time decreases, when decrease - increases. The maximum exposure time That is determined by the standard for the formation of the video signal in which the camera operates. For cameras operating in accordance with GOST 7845-92, CCIR, PAL c; for cameras operating in the EIA standard, NTSC c. Closed loop,

consisting of blocks 2,3 and 4 is a system of automatic exposure control due to the accumulation of time in the cells of the photodetector CCD-matrix 2 and is a contour of accurate adaptation. The time constant of the automatic exposure control system does not exceed the time of one field of a television signal (20 ms).

However, the dynamic range of the automatic exposure control system is not enough to ensure the operation of the camera in the range of illumination from the minimum value determined by the characteristics of the photodetector CCD-matrix 2, the video signal processing system and aperture lens 1 to the maximum possible value of natural illumination in the area of 100,000 lux, therefore, in front of the lens 1 is an optical filter of variable density 5, reversibly changing the transmission depending on the illumination and the duration of the region a scholar.

Under the action of active radiation, competing processes occur in the photosensitive phase of the variable-density optical filter 5: on the one hand, the formation of color centers, and on the other, the thermal and optical destruction of color centers, the result of which determines the speed and degree of darkening of the variable-density optical filter 5. After termination radiation, only the process of thermal destruction of color centers is retained, causing discoloration of the optical filter of variable density (rel ksatsiyu).

As an optical filter of variable density 5, reversibly changing the transmission depending on the illumination and duration of irradiation, a filter made of commercially available photochromic glass grade FHS4 or FHS7 can be used. The response time of an optical filter of variable density is determined by the relaxation time of the material from which it is made. For photochromic glass

FHS4 or FHS7 relaxation time from a transparent to a darkened state and vice versa is from 150 to 180 s.

For modern photodetector CCDs with an automatic exposure control system, the maximum value of the working illumination in the area with a relative aperture of the lens: 2.0 is from 20,000 ... .70000 lux. depending on the type and sensitivity of the photodetector CCD. The estimates show that the attenuation coefficient of the light flux in a completely darkened state for a variable density optical filter made of one standard photochromic glass grade ФХС4 5 mm thick is 3.2 times, and 10.5 times for a filter made of two standard photochromic glasses ФХС4 5 mm thick. For a filter made of glass grade ФХС7, the attenuation coefficient of the luminous flux is correspondingly 1.3 ... 2.6 times for one glass 2.5 mm thick and 1.7 ...6.7 times for two glasses. In addition, a variable density filter made of glass of the FHS4 brand helps protect the camera from accidental or deliberate exposure to the energy of a pulsed radiation source.

Thus, the proposed technical solution for a camera based on a CCD photodetector matrix provided a technical result, that is, the introduction of an optical filter of variable density in front of the lens ensured stable operation of the camera in the illumination range from the minimum possible values determined by the sensitivity of the photodetector CCD matrix and aperture ratio to the maximum possible values of natural light on the ground (100,000 lux). This eliminates the possibility of self-oscillations in the system leading to flickering of the image, and the camera with the appropriate choice of electro-radio elements is operable at temperatures up to minus 60 ° С. 6

Sources of information.

1.Universal internal cameras with lens mount C, CSMount series VBC, VNC, VCC. Manual. CJSC EMU, St. Petersburg., 2002, from 7-12.

2.Black and white CCD camera BW-410 EA / 410CA // Instraction manual. Samsung Electronics, p. 7-9, 15, 16

3. Patent of Russia JVb 2129337C1, IPC H04N 5/335, publ. 1999 1

Head of the patenting sector Mr. Leushina T.M.

Claims (1)

A camera based on a photodetector CCD array, including a sequentially located lens and interconnected photodetector CCD array with an anti-blooming device located in the focal plane of the lens, as well as a video signal amplification and processing unit and a photodetector CCD control unit, the output of which is connected with control buses of the photodetector CCD, characterized in that an optical filter of variable density is added in front of the lens, changing the pass coefficient Niya, depending on the intensity of the incident radiation flux.