RU2766416C1 - Method for forming image signal using charge-coupled matrix devices - Google Patents

Abstract

FIELD: measuring technology.

SUBSTANCE: invention relates to measuring technology, namely to the field of spectroscopy, and can be used to analyze the data of the received spectrum of optical signals from a charge-coupled device. The method for generating an image signal using charge-coupled matrix devices consists in projecting an image onto a photosensitive surface of a charge-coupled device, accumulating charge packets, and calculating a discretely specified signal accumulation time t_j in the range from t₀ to the maximum allowable signal accumulation time t_N and measuring the amplitude of the spectrum components of the received wideband image signal for all values ​​of t_j, on the basis of which the coefficient of the linear dependence of the increase in the amplitude of the output current of the spectrum point in the i-th optical element of the matrix device with a charge-coupling from the signal accumulation time K_i is calculated and the coefficients of the linear dependence of the angular coefficient of increase in the output current amplitude of a point of the spectrum with increasing signal accumulation time α and β to recalculate and correct the amplitude of the output current at each point of the spectrum of the projected image.

EFFECT: improving the accuracy of correction of non-linear distortions of the spectrum obtained on the spectrum analyzer.

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Description

The method relates to measuring technique in the field of spectroscopy and can be used to analyze the data of the received spectrum of optical signals from a charge-coupled device.

A known spatiotemporal image processing method based on arrays of photosensitive charge-coupled devices (see patent RU2569811, published on November 27, 2015), which consists in spatiotemporal image processing in the form of an image convolution projected onto a matrix of photosensitive charge-coupled devices with a pulse the characteristic of the realizable space-time filter based on two arrays of photosensitive devices with charge coupling with positive and negative readings of the impulse response and the formation of the difference of signals from the outputs of photosensitive devices with charge communication as a common output.

A known method of space-time image processing based on arrays of photosensitive devices with charge coupling (see patent RU2339180, published 11/20/2008), which consists in convolution of an image projected onto a matrix of photosensitive devices with charge coupling with the required impulse response, which determines the implemented spatio-temporal filtering , by discrete accumulation of charges photogenerated under the influence of the projected image in the potential wells of the array of photosensitive devices with charge coupling in combination with the mutual spatial displacement of the image and the matrix of photosensitive devices with charge coupling.

A known method for generating an image signal using CCDs (see patent RU2529369, published on September 27, 2014), which is selected as a prototype, consists in increasing the readout frequency of CCD-type matrix photodetectors with the formation of two image signals that differ in field of view and resolution: panoramic with a large field of view and low resolution and windows of interest with a small field of view and high resolution.

The method is carried out as follows. Before reading the charge packets, the position of the window of interest is set, characterized by the number of lines N1, N2, the level of resolution reduction in the panorama is set, characterized by the number of summed panorama lines M, the charge packets are read in three stages and two image signals are formed. The first and third stages of reading consist in performing N1 and N2 line transfer cycles, respectively, while the output register is read only every M line transfer cycles, during the second stage, the output register is read at each line transfer. Two digital image signals are formed: windows of interest and panoramas. The window of interest image signal is obtained by masking the signal samples read during the second stage, and the panorama image signal is obtained by sequential composition of the signal samples read during the first stage, the element-by-element sum of groups of M lines of samples of the signal read during the second stage, the signal samples read during the third stage.

The disadvantage of this method is the occurrence of non-linear distortions of the resulting spectrum of the received signal from the output of the device with a charge-coupling when changing the signal accumulation time.

The technical problem is the occurrence of non-linear distortions of the resulting spectrum of the projected image signal onto the light-sensitive surface of the device with a charge-coupling when the signal accumulation time changes.

The technical result of the method for generating an image signal using charge-coupled matrix devices is to implement an algorithm for correcting nonlinear spectrum distortions obtained on a spectrum analyzer using a charge-coupled device as a receiving device.

The technical result of the method for generating an image signal using charge-coupled matrix devices, which consists in projecting an image onto a light-sensitive surface of a charge-coupled device, accumulating charge packets, directed line-by-line transfer of charge packets to the output register on one line and transferring the last line of charge packets to the output register , reading the output register and converting the image signal into a line of digital samples using an analog-to-digital converter and repeating these actions until the end of reading all lines of charge packets, is achieved by the fact that when reading the output register and repeating the reading until the end of reading all lines of charge packets, an adjustment is made non-linear distortions of the spectrum of the image projected onto the photosensitive surface of the device with a charge-coupling of the image by recalculating the amplitude of the output current at each point of the spectrum of the projected image, obtained with arbitrary accumulation time t and their simultaneous entry into the controller's memory, for a fixed accumulation time t ₀ , and the recalculation of the amplitude of the output current at each point of the spectrum of the projected image is carried out according to the formula:

,

,

– скорректированное значение амплитуды выходного тока точки спектра в i-м оптическом элементе матричного прибора с зарядовой связью, A(t, A _{i ,0} ) – измеренное значение амплитуды выходного тока точки спектра при времени накопления t, α и β – коэффициенты линейной зависимости углового коэффициента нарастания амплитуды выходного тока точки спектра с увеличением времени накопления сигнала, рассчитываемого путем решения системы линейных уравнений, i – порядковый номер оптического элемента в матричном приборе с зарядовой связью, t ₀ – время накопления сигнала при котором проводится калибровка, t – время накопления сигнала, t ₀ – время накопления сигнала при котором проводится калибровка, при этом составляющие α и β определяют составляющие путем решения системы линейных уравнений:where

is the corrected value of the amplitude of the output current of the spectrum point in the i -th optical element of the matrix device with a charge coupling, A ( t, A _{i ,0} ) is the measured value of the amplitude of the output current of the spectrum point at the accumulation time t , α and β are the coefficients of the linear dependence of the angular coefficient of increase in the amplitude of the output current of the spectrum point with an increase in the signal accumulation time calculated by solving a system of linear equations, i is the serial number of the optical element in the CCD, t ₀ is the signal accumulation time at which calibration is performed, t is the signal accumulation time, t ₀ is the signal accumulation time at which calibration is carried out, while the components α and β determine the components by solving a system of linear equations:

,

,

where A _{i ,0} is the amplitude of the output current of the spectrum point, measured in the i -th optical element of the matrix device with a charge coupling, after analog-to-digital conversion, expressed in discrete readings of the analog-to-digital converter for the signal accumulation time t ₀ at which calibration is performed, α and β are the coefficients of the linear dependence of the slope of the increase in the amplitude of the output current of the spectrum point with increasing signal accumulation time, i is the serial number of the optical element in the CCD, N is the number of elements in the CCD, K _i is the coefficient of linear dependence of the increase in the amplitude of the output current of the spectrum point in the i -th optical element of the matrix device with a charge coupling on the signal accumulation time, while the component K _i is determined by the formula:

,

,

whereK _i is the coefficient of the linear dependence of the increase in the amplitude of the output current of the spectrum point ini-th optical element of a matrix device with a charge coupling on the signal accumulation time,A _{i .0} is the amplitude of the output current of the spectrum point, measured ini-th optical element of a matrix device with a charge connection, after analog-to-digital conversion, expressed in discrete readings of an analog-to-digital converter for the signal accumulation timet ₀ at which the calibration is carried out,A _{i , j} are the amplitudes of the output current of the spectrum point, measured ini-th optical element of a matrix device with a charge coupling, after analog-to-digital conversion, expressed in discrete readings of an analog-to-digital converter at different signal accumulation times,i is the serial number of the optical element in the CCD matrix device,j is the ordinal number of discretely specified signal accumulation times,N is the number of elements in the matrix device with charge coupling,M is the number of discrete signal accumulation times,t ₀ – signal accumulation time at which calibration is performed,t _j is a discretely specified signal accumulation time in the range fromt ₀ (signal accumulation time at which calibration is carried out) up tot _N (the maximum allowable signal accumulation time), while the componentt _j determined by the formula:

t _j = t ₀ + j ⋅( t _M – t ₀ )/ M,

wheret _j is a discretely specified signal accumulation time in the range fromt ₀ (signal accumulation time at which calibration is carried out) up tot _N (maximum allowable signal accumulation time),j is the ordinal number of discretely specified signal accumulation times,M is the number of discrete signal accumulation times,t ₀ – signal accumulation time at which calibration is performed,t _M is the maximum allowable signal accumulation time.

In FIG. Figure 1 shows a block diagram of a device that implements the proposed method for generating an image signal using charge-coupled matrix devices.

In FIG. Figure 2 shows the operation algorithm of the controller for automatic correction of spectrum distortions.

The device for implementing the proposed method for generating an image signal using charge-coupled matrix devices, shown in Fig. 1 contains a broadband optical signal source 1, an optical circulator 2, an array of series-connected optical filters 3, a diffraction grating 4, a charge-coupled device 5, and a controller for automatic correction of spectrum distortions 6, moreover, a broadband optical signal source 1, the input of which is the input of the device , connected to the first port of the optical circulator 2 via a fiber light guide, an array of series-connected optical filters 3 is connected to the second port of the optical circulator 2 via a fiber light guide, the third port of the optical circulator 2 is connected to the input of a diffraction grating 4 via a fiber light guide, the output of which is connected to the input of the device with a charge-coupled 5, the output of which is connected to the controller for automatic correction of spectrum distortions 6, the output of which is the output of the device, and the array of series-connected optical filters 3 is made on the basis of fiber th Bragg grating with a Gaussian shape of the reflection spectrum.

The device works as follows. Beforehand, a program is loaded into the controller unit for automatic correction of spectrum distortions 6, which works according to the algorithm shown in Fig. 2.

Connect the power supply system for blocks of broadband optical signal 1, the controller for automatic correction of spectrum distortions 6.

The power supply system required for the blocks of the broadband optical signal source 1, the controller for automatic correction of spectrum distortions 6 in Fig. 1 is not shown.

To generate an image signal using CCDs, a wideband optical signal f(λ) is generated using a broadband optical signal source 1 with a central frequency corresponding to the middle of the frequency band covered by an array of series-connected optical filters 3. The generated broadband signal passes through the first port optical circulator 2 and fed to an array of series-connected optical filters 3, the frequency bands of which are equal to each other and are selected in such a way as to cover the entire frequency range of the broadband signal. In the array of series-connected optical filters 3, in each of the individual filters, the amplitudes of the spectral components of the broadband signal change, falling into the passband and reflection of each of the individual filters of the array of series-connected optical filters 3.

The broadband signal g(λ) obtained in this way in the reflection channel of an array of series-connected optical filters 3 is reflected back to the second port of the optical circulator 2 and through the third port of the optical circulator 2, enters the diffraction grating 4, where the spectrum of the broadband signal g(λ) is decomposed into individual spectral components g(λ _i ), which are then projected onto the light-sensitive surface of the device with charge coupling 5, where the charge packets are accumulated, the charge packets are directed line-by-line transfer to the output register on one line and the last line of the charge packets is transferred to the output register, reading output register and the formation of samples A _i λ _i , with amplitude A, which, in turn, are sent to the controller for automatic correction of spectrum distortions 6, where digitization and correction of distortions of the broadband signal spectrum is carried out after passing through an array of series-connected optical filters filters 3, which arise as a result of choosing different charge accumulation times in a CCD 5.

Consider the implementation of the method of forming an image signal using matrix devices with charge coupling. The output register is read, the readings are formed, and the data received from the CCD 5 is digitized. The algorithm that automatically corrects the distortions of the optical signal spectra operates in two modes: calibration mode and measurement mode.

In the calibration mode, the number of discretely specified signal accumulation times M, the calibration signal accumulation time t ₀ and the maximum allowable signal accumulation time t _M are pre-set, which are determined by the required measurement and correction accuracy, on the basis of which the accumulation time tuning step Δt is calculated and the discretely specified time is calculated signal accumulation t _j in the range from t ₀ to the maximum allowable signal accumulation time t _M . Then the amplitude of the spectrum components of the received broadband signal is measured for all values of t _j on the basis of which the coefficient of the linear dependence of the increase in the amplitude of the output current in the i-th optical element of the matrix device with charge coupling 5 is calculated from the signal accumulation time K _i and the coefficients of the linear dependence of the angular the coefficient of amplitude increase with increasing signal accumulation time α and β, which are recorded in memory to correct distortions of the measured spectra of a broadband image signal projected onto a photosensitive surface of a CCD device when operating in the measurement mode.

In the measurement mode, the range of change in the accumulation time t _int is pre-set to ensure the change in the amplitude of the measured spectral components A _i in the range [A _min … A _max ], determined by the required measurement accuracy. Then, the spectrum of the broadband image signal projected onto the photosensitive surface of the device with a charge-coupling is measured and the amplitude and wavelength values of its spectral components are corrected according to the previously calculated values of α and β.

A device for implementing the proposed method for generating an image signal using charge-coupled matrix devices can be implemented on the following elements, designed to operate at a central wavelength of 785 nm (other wavelengths are possible), for example:

As a source of broadband optical signal 1, a broadband optical source SLD-CS-331-HP3-SM-785-I from Superlum can be selected;

Optical circulator GateRay GR-CIRC-31 can be chosen as optical circulator 2;

As an array of series-connected optical filters 3, fiber Bragg gratings can be selected;

As the diffraction grating 4, the SH.10G08-DO-RDG-RP diffraction grating from Schwabe can be selected;

As the CCD 5, the S9737-01 CCD from Hamamatsu can be selected;

As a controller for automatic correction of spectrum distortions 6, a microprocessor controller based on chips from Atmel, Microchip, etc. can be selected;

Reference cords or cables TELECOM-TEST of the LLC Production and Trade Company SOKOL can be chosen as fiber light guides.

To build a device for implementing the proposed method for generating an image signal using charge-coupled matrix devices, all of the indicated blocks for generating, receiving and processing signals can be made in an integrated design.

All this allows us to speak about the achievement of the technical result - the correction of non-linear distortions of the spectra of optical signals based on charge-coupled devices by implementing an algorithm for correcting non-linear distortions of the spectrum obtained on a spectrum analyzer using a charge-coupled device as a receiving device.

Claims (34)

A method for generating an image signal using charge-coupled matrix devices, which consists in projecting an image onto a light-sensitive surface of a charge-coupled device, accumulating charge packets, directed line-by-line transfer of charge packets to the output register on one line, and transferring the last line of charge packets to the output register, reading the output register, and converting the image signal into a line of digital samples using an analog-to-digital converter, and repeating these actions until the end of reading all lines of charge packets, characterized in that when reading the output register and repeating the reading until the end of reading all lines of charge packets, correction of non-linear distortions of the spectrum of an image projected onto a photosensitive device with a charge-coupled device by recalculating the amplitude of the output current at each point of the spectrum of the projected image obtained at an arbitrary time and accumulation t and their simultaneous entry into the memory of the controller, for a fixed accumulation time t ₀ , and the recalculation of the amplitude of the output current at each point of the spectrum of the projected image is carried out according to the formula:

, where

is the corrected value of the amplitude of the output current of the spectrum point in the i -th optical element of the CCD matrix device, A ( t, A _{i ,0} ) is the measured value of the amplitude of the output current of the spectrum point at the accumulation time t , α and β are the coefficients of the linear dependence of the slope of the increase in the amplitude of the output current of the spectrum point with increasing signal accumulation time, calculated by solving a system of linear equations, i is the serial number of the optical element in the CCD matrix device, t ₀ is the signal accumulation time at which calibration is carried out, t is the signal accumulation time, t ₀ is the signal accumulation time at which calibration is carried out, while the components α and β determine the components by solving a system of linear equations:

, where A _{i ,0} is the amplitude of the output current of the spectrum point, measured in the i -th optical element of the matrix device with a charge-coupling, after analog-to-digital conversion, expressed in discrete readings of the analog-to-digital converter for the signal accumulation time t ₀ at which calibration is carried out , α and β are the coefficients of the linear dependence of the slope of the increase in the amplitude of the output current of the spectrum point with increasing signal accumulation time, i is the serial number of the optical element in the CCD matrix device, N is the number of elements in the matrix device with charge coupling, K _i is the coefficient of linear dependence of the increase in the amplitude of the output current of the spectrum point in the i -th optical element of the matrix device with a charge coupling on the signal accumulation time, the component K _i is determined by the formula:

, where K _i is the coefficient of the linear dependence of the increase in the amplitude of the output current of the spectrum point in the i -th optical element of the matrix device with a charge coupling on the signal accumulation time, A _{i ,0} is the amplitude of the output current of the spectrum point, measured in the i -th optical element of the matrix device with a charge coupling, after analog-to-digital conversion, expressed in discrete readings of the analog-to-digital converter for the signal accumulation time t ₀ at which calibration is carried out, A _{i , j} are the amplitudes of the output current of the spectrum point, measured in the i -th optical element of the matrix device with a charge coupling, after analog-to-digital conversion, expressed in discrete readings of the analog-to-digital converter at different signal accumulation times, i is the serial number of the optical element in the CCD matrix device, j is the serial number of discretely specified signal accumulation times, N is the number of elements in the matrix device with charge coupling, M is the number of discrete signal accumulation times, t ₀ is the signal accumulation time at which calibration is carried out, t _j is a discretely specified signal accumulation time in the range fromt ₀ (signal accumulation time at which calibration is carried out) up tot _N (maximum allowable signal accumulation time), in this case, the component t _j is determined by the formula: t _j = t ₀ + j ⋅( t _M – t ₀ )/ M, where t _j is a discretely specified signal accumulation time in the range from t ₀ (signal accumulation time at which calibration is performed) to t _N (the maximum allowable signal accumulation time), j is the serial number of discretely specified signal accumulation times, M is the number of discrete signal accumulation times, t ₀ is the signal accumulation time at which calibration is carried out, t _M is the maximum allowable signal accumulation time.

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