RU1314800C - Method and apparatus to calibrate matrix photodetector - Google Patents

Abstract

FIELD: optical electronic television equipment. SUBSTANCE: matrix photodetector nonuniformity calibration method provides for treatment of photodetector with reference radiation, amplification of video signal of each ij member up to value of reference level, determination and storing of corresponding factor of compensation and following amplification of video signal from each ij member. During calibration point source reference radiation weight center coordinate is measured and photodetector is moved till coordinate of calibrated member coincides with coordinate of reference radiation weight center. Apparatus to compensate matrix photodetector video signal nonuniformity also has television camera 1, movement device 2, matching block 3, storing block 10, sequential approximation register 11, digital switch 12, comparator 13 and reference level code sensor. Analog-digital converter 4, coordinated discrete measuring unit 8, second digital switch 5, second and third comparators 7 and 9, multiplying unit 14 and counter 6 are added to the apparatus. This allows to exercise with high accuracy calibration of matrix photodetector during operation with point-type or local source of radiation. In the case, calibration as a version is exercised using both reference source of radiation and information light stream from source under study, that increases accuracy of compensation. EFFECT: increased accuracy of compensation. 3 cl, 2 dwg

Description

 The invention relates to optical-electronic television technology and can be used in devices for measuring the coordinates and photometry of point objects, in systems of astro-orientation and astronavigation, in which matrix photodetectors are used.

 The aim of the invention is to improve the accuracy of compensating for uneven video signal of a matrix photodetector.

 Figure 1 shows the structural diagram of a device for calibrating a matrix photodetector; figure 2 is a structural diagram of a discrete coordinate meter.

 The calibration method of the matrix photodetector is as follows.

где j номер элемента разложения по строке, т.е. номер столбца фотоприемника;
i номер cтроки;
А_j1 амплитуда видеосигнала от ij-го элемента.During calibration, the photodetector is irradiated using a point radiation source and the coordinates of the center of gravity of a point object in the decomposition elements are measured using the algorithm with weighting

where j is the number of the line expansion element, i.e. column number of the photodetector;
i line number;
And _{j1 is the} amplitude of the video signal from the ij-th element.

,

сравнивают с координатами I, у калибруемого элемента: в случае несовпадения координат перемещают фотоприемник (или световой поток относительно фотоприемника) до их совпадения. Затем определяют коэффициент коррекции чувствительности указанного элемента и запоминают его, после чего переходят к калибровке следующего элемента. В режиме компенсации видеосигнал ij-го элемента усиливают с соответствующим коэффициентом компенсации N_ij.Coordinates

,

they are compared with the coordinates I, for the element being calibrated: in case of a mismatch of coordinates, the photodetector (or light flux relative to the photodetector) is moved until they coincide. Then, the sensitivity correction coefficient of the specified element is determined and stored, after which they proceed to the calibration of the next element. In the compensation mode, the video signal of the ij-th element is amplified with the corresponding compensation coefficient N _ij .

 The device for calibrating the matrix photodetector contains a television camera 1, including a matrix photodetector and a synchronization unit, a moving device 2, a matching unit 3, an analog-to-digital converter (ADC) 4, a second digital switch 5, a counter 6, a third comparator 7, a discrete coordinate measuring device 8 , a second comparator 9, a memory unit 10, a successive approximation register 11, a first digital switch 12, a first comparator 13, a multiplication unit 14, a reference level code sensor 15, a calibration signal input 16 and an output 17.

 The discrete coordinate meter 8 comprises a threshold block 18, multiplication blocks 19 and 20, a single vibrator 21, accumulating adders 22-24, division blocks 25 and 26, and an output register 27.

 The device operates as follows.

 The signal “Calibration”, which is input 16, allows the third comparator 7 to work and switches the switch 12 to the mode when the first input connected to the output of the register 11 of successive approximations is connected to its output, puts the memory unit 10 at the fifth input into the addressing mode from the counter 6, and also sets the counter 6 to its original state.

в данном кадре. Во время кадрового гасящего импульса (КГИ) эти координаты записываются в выходной регистр измерителя и поступают таким образом на второй вход компаратора 7. Если равенства I=

, y=

не выполняются, то на первом выходе /> </ компаратора 7 будет сигнал, определяющий направление и величину движения устройства 2 перемещения. В течение некоторого числа кадров повторяются операции измерения координат и сравнения их со значениями I_y. Если I=

, y=

, то на первом выходе компаратора 7 сигналы отсутствуют, а на втором выходе /=/ возникает логическая "1", которая поступает на управляющий третий вход цифрового коммутатора 5 и на третий вход выбора регистра 11 последовательных приближений. В следующем кадре, когда код номера текущего элемента ij, поступающего на первый вход компаратора 9 с выхода телевизионной камеры 1, совпадает с кодом Iy на выходе счетчика 6, с выхода компаратора 9 снимается импульс, который поступает на тактовый вход АЦП 4. Таким образом, до окончания текущего кадра на выходе АЦП фиксируется код, характеризующий сигнал с элемента с номером Iy. Этот код поступает на первый вход блока 14 умножения, второй вход которого подключен к выходу регистра 11 последовательных приближений, который запускается по четвертому входу импульсом с выхода цифрового коммутатора 5. В течение (n+1) тактов, где n число разрядов на выходе кода регистра 11, осуществляется при помощи блока 14 умножения, компаратора 13, датчика 15 кода опорного уровня и регистра 11 формирование кода N_Iy коррекции чувствительности Iy-го элемента посредством сравнения произведения кодов сигнала А_Iy, с указанного элемента и подбираемого коэффициента коррекции N_Iy с кодом N_m опорного уровня. По окончании процесса подбора кода сигналом "Конец измерения" с второго выхода регистра 11 последовательных приближений производится запись значения N_Iy в ячейку блока 10 памяти по адресу Iy, который поступает на четвертый вход блока памяти с выхода счетчика 6. Этот же сигнал устанавливает счетчик 6 следующее состояние I, y+1.From the output of counter 6, the code number of the calibrated element of the matrix photodetector Iy is taken, where y is the element number in the row or column number, I is the row number, and is fed to the input of the comparator 7. The ADC 4 converts the voltage of the video signal from the output of the television camera 1 to the digital code A _ij , since through the digital switch 5 to its clock input receives clock pulses (TI), the next with a frequency of elements. This digital code is fed to a discrete 8-coordinate meter, where the coordinates of the center of gravity of a point object projected onto the photosensitive surface of the matrix photodetector are calculated

in this frame. During the frame blanking pulse (CGI), these coordinates are recorded in the output register of the meter and thus arrive at the second input of the comparator 7. If the equalities I =

, y =

are not executed, then at the first output /></ of the comparator 7 there will be a signal that determines the direction and magnitude of the movement of the device 2 movement. For a certain number of frames, the operations of measuring coordinates and comparing them with the values of I _{y are} repeated. If I =

, y =

, then at the first output of comparator 7 there are no signals, and at the second output / = / a logical “1” appears, which goes to the control third input of the digital switch 5 and to the third input of the selection of the register 11 of successive approximations. In the next frame, when the code number of the current element ij arriving at the first input of the comparator 9 from the output of the television camera 1 coincides with the code Iy at the output of the counter 6, the pulse is transmitted from the output of the comparator 9, which is fed to the clock input of the ADC 4. Thus, Before the end of the current frame, the code characterizing the signal from the element with the number Iy is recorded at the ADC output. This code is fed to the first input of the multiplication unit 14, the second input of which is connected to the output of the consecutive approximation register 11, which is triggered by the fourth input by a pulse from the output of the digital switch 5. During (n + 1) clock cycles, where n is the number of bits at the output of the register code 11, it is carried out using the multiplication unit 14, the comparator 13, the reference level code sensor 15 and the register 11 to generate the sensitivity correction code N _{Iy of the} Iy element by comparing the product of the signal codes A _Iy from the specified element and the selected correction coefficient N _Iy with code N _{m of the} reference level. At the end of the code selection process, the signal “End of measurement” from the second output of the register of 11 successive approximations records the value of N _Iy in the cell of the memory block 10 at the address Iy, which is fed to the fourth input of the memory block from the output of counter 6. The same signal sets counter 6 as follows state I, y + 1.

 Then the signal from the second output (=) of the comparator 8 is removed, the digital switch 5 is returned to its original state, which ensures the operation of the ADC 4 in a bitwise mode and a discrete coordinate meter 8, and the register of successive approximations is turned off by the selection input.

Further, the processes described above are repeated until the coefficient N _I , y + 1 is found for the sensitivity correction of the element with the number I, y + 1.

 Thus, the calibration of all elements of the matrix photodetector is carried out.

 At the end of the calibration, the “Calibration” signal from the input 16 is removed, which can be done by decrypting the final state of the counter 6, and the device switches to compensation mode: the output of the switch 12 is now connected to its second input connected to the output of the memory unit 10, which is already addressed from the synchronization unit of the television camera 1.

The code from the output of the ADC 4 A _iu goes to the multiplication unit 14, where it is multiplied by the compensation coefficient N _ij and, as a result, the video signal corrected by the unevenness of sensitivity comes in the form of a binary code that varies with the frequency of the elements.

Claims (3)

1. The method of calibrating the matrix photodetector, which consists in irradiating the matrix photodetector with radiation from a reference radiation source, amplifying the video signal from each ij-th element, where i is the row number of the matrix photodetector, j is the column number to the reference level, determining and storing the compensation coefficient N _i for each element and the subsequent amplification of the video signal from each ij-th element with a compensation coefficient N _i , characterized in that, in order to improve the accuracy of compensation for uneven video signal matrix photodetector, determine the coordinate of the center of gravity of the light spot of the reference radiation source, measure the coordinate of the ij-th element of the matrix photodetector, compare them with each other and shift the matrix photodetector until the coordinate of the ij-th element coincides with the coordinate of the center of gravity of the reference radiation source.  2. A device for calibrating a matrix photodetector comprising a television camera including a matrix photodetector and a synchronization unit associated with a moving device connected to the matching unit, as well as a memory unit, a successive approximation register, a digital switch, a comparator and a reference level code sensor, the output of which connected to the second input of the comparator connected by the output to the first input of the sequential approximation register, the second input of which is connected to the output of the television camera and the second the input of the memory unit, and the output with the first input of the memory unit and the first input of the digital switch, the second input of which is connected to the output of the memory unit, characterized in that an analog-to-digital converter, a discrete coordinate meter, a second digital switch, the second and third comparators are introduced into it , a multiplication unit and a counter, the input of which is connected to the third input of the memory unit and the second output of the sequential approximation register connected by the third input to the third input of the second digital switch and the second output a third comparator, the first output of which is connected to the input of the matching unit, the first input with the output of the counter, the fourth input of the memory unit and the second input of the second comparator connected by the first input to the output of the television camera, the first input of the analog-to-digital converter and the first input of the second digital switch, the second the input of which is connected to the output of the second comparator, the first output with the fourth input of the sequential approximation register and the second input of the analog-to-digital converter, and the second output from the second m input of a discrete coordinate meter connected to the second input of the third comparator, and the first input to the output of the analog-to-digital converter and the first input of the multiplication unit, the output of which is connected to the first input of the first comparator and the output of the device, and the second input to the output of the first digital switch, connected by the third input to the third input of the third comparator and the fifth input of the memory block.  3. The device according to claim 2, characterized in that the discrete coordinate meter comprises a threshold block, the output of which is connected to the first inputs of the first and second multiplication blocks, the outputs of each of which are connected to the first inputs of the first and second adders, respectively, the outputs of which are connected to the first the inputs of the first and second blocks of division, the outputs of which are connected to the inputs of the output register connected to the input of the comparator, as well as a series-connected single vibrator and a third adder, the output of which is connected to the second m inputs of the division blocks, while the output of the one-shot is additionally connected to the second inputs of the first and second adders, and the input is connected to the output of the digital switch, the other output of which is connected to the third inputs of the division blocks, the output of the digital switch is additionally connected to the second inputs of the multiplication units and to the fourth the inputs of the division blocks, the output of the threshold block is connected to the second input of the third adder, and the output of the analog-to-digital converter is connected to the input of the threshold block, the third input of the first, second a multiplication unit and the third adder.

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