RU2012156C1 - Videosignal pick-up built around charge-coupled element - Google Patents

Abstract

FIELD: television. SUBSTANCE: pick-up includes N identical frame transport matrices based on charge-coupled elements. Each matrix has single-side accumulation sections, store sections, M-bit register, commutation unit, controlled key, multiplication unit, comparator, amplifiers. All the matrices are combined in a multilayer module so that their adjacent sections form step-like light-sensitive surface, in front of which fibre bundle having the same face is positioned. EFFECT: higher reliability. 4 dwg

Description

 The invention relates to television technology, the predominant area of its use is the development of electronic photodetectors designed for astronomical optoelectronic systems.

 A known sensor in the form of a CCD matrix with frame transfer, consisting of areas identical in the number of elements in the direction of charge transfer: a photosensitive storage section and a lightproof information storage section. The latter is connected to a read register connected to an output device, for example, with a floating diffusion region, the output of which is the information output of a CCD matrix (F. P. Press. Video signal shapers on charge-coupled devices. M.: Radio and communication, 1981, S. 20-21, 39-40).

 The disadvantages of this sensor are the spreading of the charge from bright light sources (when it exceeds the depth of the potential well of the CCD element) into adjacent elements of the storage section, which reduces the noise immunity of the TV system using this sensor.

 To eliminate these drawbacks, anti-blooming drain channels are used that divide the charge packet transfer registers (K. Seken, M. Thompset. Charge transfer devices, M.: Mir, 1978, pp. 194-199), and also increase the charge transfer frequency.

 However, at the same time, information about the signals of bright light sources is lost, which excludes the possibility of measuring them, and transport noise increases, which together with the residual spurious signal form extended traces of charge transfer from bright sources on the potential topography of the storage section of the CCD matrix, which reduce the noise immunity of the TV system .

 Many technical devices use CCD sensors that use the specified CCD matrix with various devices for processing its video signal.

 When constructing optimal object signal detectors, the use of a known CCD charge transfer channel at the output of the readout register of the CCD matrix, divided into component (generally nonequilibrium) channels, allows one to obtain several autonomous paths for primary processing of the video signal, each of which includes an output device (K. Sechen, M. Thompset, Charge Transfer Devices M.: Mir, 1978, p. 72-74).

 The device for further processing the video signal of these autonomous paths, carrying out their switching and AD conversion of the corresponding signal, taking into account the nonequilibrium components of the CCD channels, is also quite simple. Such processing provides a breakdown of the dynamic range of the video signal into component subbands with the required accuracy of the AD conversion in each of them.

 The closest in technical essence to the proposed device is a CCD sensor using the indicated CCD matrix, the output of the read register of which is connected to a CCD channel, divided into two channels connected to identical output devices. A two-channel signal processing device for the CCD matrix contains in each of the two paths an identical amplifier, for example, with a double correlated sample (edited by P. Jespers, F. Van de Wiele, and M. White. Semiconductor imaging devices, M.: Mir , 1979, pp. 406-408), connected by its input to the output of the corresponding output device. The outputs of the amplifiers are connected respectively to the two switched inputs of the on-off controlled key, the output of which is connected to the input of an analog-to-digital converter, the output of which is connected to one switched input of the second on-off controlled key and to the input of the multiplication unit, the output of which is connected to the second switched input of the second on-off controlled key , the output of which is the information output of the sensor, and the control inputs of both keys are connected to the output of the comparator, one input to torogo connected to the output of one amplifier and the other input is a constant threshold voltage.

 To improve the noise immunity of this sensor, it uses anti-blooming drain channels to prevent charges from bright light sources from spreading across neighboring elements of the CCD array storage section, but this reduces the dynamic range of the sensor signal by limiting the maximum accumulated charge to the depth of the potential well of the storage section element ( given its linear size, due to the requirements for resolution and accuracy of the TV system). In addition, this sensor also has another disadvantage associated with the accumulation of parasitic charges during the transfer of information from the accumulation section to the storage section of the CCD matrix.

 The purpose of the invention is to increase the dynamic range of the signal of the video signal sensor on a charge-coupled device.

 This is achieved by the fact that in the video signal sensor on a device with a charge-coupled connection containing a CCD matrix with frame transfer, consisting of single-line sections for the accumulation and storage of information and an M-bit read register, the output of which is connected to a CCD channel for transferring charges, divided into two nonequilibrium channels, respectively connected to the inputs of two output devices, and two amplifiers, the outputs of which are connected respectively to two switched inputs of the first on-off controlled key, the output of which is connected to the input of the analog-to-digital converter, the output of which is connected to one switched input of the second on-off controlled key and to the input of the multiplication unit, the output of which is connected to the second switched input of the second on-off controlled key, the output of which is the sensor information output, and the control inputs of both keys are connected to the output a comparator, the first input of which is connected to the output of the first amplifier, and a constant threshold voltage is applied to the other input, an additional (N-1) identifier is introduced CCD matrices, the outputs of the output devices of all component matrices are connected to the corresponding inputs of the switching unit, two outputs of which are connected to the inputs of the amplifiers. All matrices are structurally combined into a multilayer module so that their closely adjoining accumulation sections form a stepped photosensitive surface with the NxM format of elements to which the end face of the fiber optic bundle having the identical configuration is joined, the other end of which is the focal plane of the sensor.

 Unlike the prototype in the proposed device, the charges generated in the photosensitive surface during the accumulation time are repeatedly (and not in one go) transferred to the light-protected sections of information storage, where they are summed and then transferred to the corresponding read registers. If the area of the element of the information storage sections and the read register exceeds the area of the element of the accumulation sections due to a corresponding increase in the depth of the potential well, a gain is obtained in the dynamic range of the signal, and line-by-line dumping of information from each accumulation section to the corresponding storage section (without transferring charges on the photosensitive surface, as this is implemented in the prototype) avoids the spurious signal of charge transfer, which leads to an increase in noise immunity proposed on the sensor. Moreover, having these advantages, it will (with the same resolution) have a sensitivity almost the same as that of the prototype.

 The proposed device differs from the prototype in the absence of electrical connection between the output devices and amplifiers, the presence of (N-1) additional matrices, the combination of all CCD matrices in the original modular design, the presence of new units (fiber optic bundle and switching unit) and their structural and electrical links to other elements of the circuit.

 In FIG. 1 is a structural diagram of the proposed sensor video signal on the device with a charge-coupled connection; in FIG. 2 is a block diagram of a switching unit; in FIG. 3 - design of a video signal sensor on a charge-coupled device; in FIG. 4 is a timing diagram illustrating the operation of the constituent blocks of the proposed sensor.

The video signal sensor on a charge-coupled device consists of N identical CCD matrices 1 with frame transfer, consisting of single-line storage sections 2 and 3 information storage and an M-bit read register 4, the output of which is connected to the charge transfer CCD channel 5, divided into two nonequilibrium channels connected to identical output devices 6, 7, for example, with a floating diffusion region. All output devices are connected to the corresponding inputs of the switching unit 8, consisting, for example, of a clock generator 16, the output of which is connected to the input of the counter 17, the corresponding outputs of the triggers of which are connected to the inputs of the combinational circuit 18, N outputs of which are connected respectively to the control inputs of the dual on-off controlled keys 19. Two outputs of the switching unit 8 are connected to the inputs of identical amplifiers 9, 10, for example, with double correlated sampling, the outputs of which are connected respectively but to the two switched inputs of the on-off controlled key 11, the output of which is connected to the input of the analog-to-digital converter 12, the output of which is connected to one switched input of the second on-off controlled key 14 and to the input of the digital multiplication unit 13, connected by its output to the other switched input of the second controlled key 14, the output of which is the information output of the sensor. The control inputs of the keys 11, 14 are connected to the output of the comparator 15, one input of which is connected to the output of the amplifier 9, and a constant threshold voltage U _{n is} applied to the other.

 Structurally, the matrices 1 are assembled into a multilayer module 20 so that their closely adjoining accumulation sections form a stepped photosensitive surface in the format of N x M elements, to which an end face of the fiber optic bundle 21, the other end of which is the focal plane of the sensor, is docked. In each layer of module 20, elements 1-7 are located; the sensor video processing board 22 comprises elements 9-19. The electrical connection of the module 20 and the board 22, as well as the supply of the necessary control pulses to them, is provided using a multi-core cable 23.

 As a comparator 15, IC 521 CA5 can be used, as controlled keys 11, 14 - IC 590 KN4, ADC 12 can be implemented on IC K572 PV1A-B, digital multiplication unit 13 - on IC KR 1802 BP2, and amplifiers 9, 10 are performed on the IC 544 UD2. Switching device 8 can be performed on the following integrated circuits: 531 LAZ - clock generator 16; 531 IE17P - counter 17, 555 ID8, 531TM2P - combinational circuit 18; 590KN4 - managed keys 19.

 The design features of the proposed sensor include the presence of runoff channels separating charge packet transfer registers in the sections for accumulating and storing information of constituent matrices, as well as the following dependences of some parameters characterizing its operation.

=

=

=

= K_БУ,
U_п= U_1Кмах,
d_B<< l_эсн, где S_эсн, S_эсх, S_эрс, S_э1К, S_э2К - соответственно площади элементов секций накопления 2 и хранения 3 информации, регистра 4 считывания, первого и второго составляющих каналов ПЗС-канала 5;
Q_cн, Q_cх, Q_pc, Q_1K, Q_2K - соответственно глубина потенциальной ямы ПЗС-элемента секций 2 и 3, регистра 4, первого и второго каналов ПЗС-канала 5;
К - коэффициент пропорциональности (К > 1);
К_БУ - множитель в цифровом блоке 13 умножения;
U_1Кмах - максимальный сигнал на выходе усилителя 9;
Т_накΣ - суммарное время накопления заряда в секциях хранения информации 3;
Т_нак - время накопления заряда в секциях накопления информации 2;
d_В - диаметр волокна волоконно-оптического жгута 22;
l_эсн - линейный размер элемента секций накопления 2
Датчик видеосигнала на приборе с зарядовой связью работает следующим образом.S _esh = S _ems = S _e1k + S _e2k ,
Q _cx = Q _pc = Q _1K + Q _2K ,
K =

=

=

=

= K _BU ,
U _p = U _{1 Kmah} ,
d _B << l _esn , where S _esn , S _eskh , S _ers , S _e1K , S _e2K are, respectively, the area of the elements of the sections of accumulation 2 and storage of 3 information, read register 4, the first and second component channels of the CCD channel 5;
Q _cn , Q _cx , Q _pc , Q _1K , Q _2K - respectively, the depth of the potential well of the CCD element of sections 2 and 3, register 4, the first and second channels of the CCD channel 5;
K is the coefficient of proportionality (K>1);
To _BU - the multiplier in the digital block 13 multiplication;
U _1Kmakh - the maximum signal at the output of the amplifier 9;
T _nkΣ is the total charge accumulation time in the information storage sections 3;
T _NK - the time of accumulation of charge in the sections of the accumulation of information 2;
d _{In the} diameter of the fiber optic bundle 22;
l _esn - linear element size of accumulation sections 2
The video sensor on the device with a charge-coupled device operates as follows.

The optical image focused by the optical system in the focal plane, coinciding with the flat end of the fiber optic bundle 22, is transferred by it to the photosensitive surface. Under the action of light, in M elements of each accumulation section 2, charges proportional to the distribution of illumination accumulate during the time T _nk . When the charge accumulated in section 2 exceeds the depth of the potential well of the element, excess carriers are diverted to the stock areas, preventing the image from blurring. The accumulated charge relief during the transfer time T _per1 simultaneously for all matrices is transferred to the elements of the storage sections 3, which, having K times larger than that of the elements of the accumulation sections, have an area corresponding to K times greater depth of the potential well. Stock areas in sections 3 of information storage prevent the spread of the charge accumulated in them during the time T _nakΣ = KT _nak . After K charge transfer cycles in section 3, the charge relief is transferred from them synchronously for all matrices 1 during the time T _per2 to registers 4, from which it is subsequently read out alternately. In this case, the charge packets are separated in the CCD channels 5 into pairs of nonequilibrium charges in a 1: K ratio and are converted into the corresponding video pulses by identical output devices 6, 7.

 The necessity of dividing the video path into two nonequilibrium channels is due to the fact that the maximum charge read from register 4 exceeds the allowable charge at the input of output devices 6, 7, which ensures linearity and the required high accuracy of the AD conversion of the video signal. Therefore, the charges of register 4, corresponding to large signals, are removed from the second transfer channel with K times a smaller area of the element, i.e., with a decrease in K times, and small signals, the range of which is 1 / K of the total range, are removed from the first channel 1 K .

When reading charges from the registers 4, the switching unit 8 carries out alternate connection of the output devices of the 6.7 component matrices 1 (sequentially from the first to the Nth). Such a connection of the output devices of each matrix is made during the reading of the charge relief from the M elements of the corresponding reading register (T _cci ). Each time devices 6, 7 are switched, the following operations are performed in the switching device 8: under the action of a clock pulse, a counter 17 is activated from the clock generator 16. At the same time, a potential change occurs at the corresponding outputs of the combinational circuit 18, which, acting on the control inputs of the corresponding keys 19, cause their operation, as a result of which the output devices 6, 7 of the i-th matrix 1 are disconnected from the inputs of the amplifiers 9, 10, to which the output devices of the 6, 7 (i + 1) -th matrix are connected.

The comparator 15 captures the excess of the signal U _1K over the threshold U _p corresponding to the level of the maximum signal in the path 6-8-9. The managed key 11 in accordance with the output signal of the comparator U _K connects to the ADC 12 either 9 if U _1K <U _p , or 10 if U _1K ≥U _p . The ADC converts the video signal into a digital code. Accordingly, according to the signal U _K, for weak signals, the output signal of the sensor is directly a digital video signal from the output of the ADC 12, and for large signals after multiplying by K _BU from the output of block 13. Switching of outputs 12 and 13 to the sensor information output is performed by key 14 under the action control signal U _K.

+

+

+

+

+

, где Т_сч.э - длительность считывания одного заряда с регистра 4;
τ_срi- время срабатывания соответствующего блока (см. фиг. 1).Additional conditions for the implementation of the proposed sensor are K (T _nk + T _per1 )> NMT _sc .
K (T _nk + T _per1 )> NMT _cf.
T _sch.e >

+

+

+

+

+

where T _SCE - the duration of reading one charge from register 4;
τ _cfi is the response time of the corresponding block (see Fig. 1).

 Subject to the latter condition, the proposed sensor performs automatic switching of both paths for processing and converting information in real time.

 The technical effectiveness of the proposed CCD sensor relative to the prototype can be assessed by comparing their main parameters.

, где N_min - минимальный сигнал элемента матрицы;
σ_Σ- среднеквадратическое значение суммарного шума элемента матрицы.The sensitivity of the CCD receiver is characterized by the signal-to-noise ratio at the amplifier output
Ψ =

where N _min is the minimum signal of the matrix element;
σ _Σ is the rms value of the total noise of the matrix element.

+T

+K(T_нак+T

)= T

+KT

Откуда при Т_перП= КТ_пер1 следует Т_накΣ= Т_накП.From FIG. 4 shows that the duration of the accumulation and transfer of the proposed sensor and prototype (P) are connected by the following ratio:

+ T

+ K (T _nk + T

) = T

+ KT

Whence at T _perP = CT _per1 it follows that T _{nc Σ} = T _ncP .

, где τ - коэффициент пропускания волоконно-оптического жгута.Then, with the same size of the element of the photosensitive surface, and therefore the same resolution of the proposed sensor (D) and prototype, the dependence of their minimum signals is
N = τN

where τ is the transmittance of the fiber optic bundle.

=

.With the identical elements of the structure of the video path of the sensor and the prototype

=

.

Then ϑ _Д + τϑ _П , i.e., at low energy losses in the fiber, the compared receivers can be considered close in sensitivity.

= τKN

Тогда выигрыш в динамическом диапазоне сигнала, обеспечиваемый ПЗС-датчиком, по сравнению с прототипом составляет
η =

= K Кроме того, в предлагаемом датчике накопленные на светочувствительной поверхности зарядовые пакеты за один такт построчно выносятся в светозащищенные секции хранения, а не переносятся по всей секции накопления, как в прототипе. Это принципиально исключает паразитные заряды, накапливаемые во время переноса в матрице прототипа, а следовательно повышает по сравнению с ним помехозащищенность предлагаемого датчика.Based on the principle of operation of the proposed sensor, the maximum accumulated signal of an element of its information storage section is associated with the maximum signal of the element of the prototype matrix by the ratio
N

= τKN

Then the gain in the dynamic range of the signal provided by the CCD sensor, in comparison with the prototype is
η =

= K In addition, in the proposed sensor, the charge packets accumulated on the photosensitive surface in one cycle are taken out line by line into the light-protected storage sections, and are not transferred throughout the accumulation section, as in the prototype. This fundamentally eliminates spurious charges accumulated during transfer in the prototype matrix, and therefore increases the noise immunity of the proposed sensor compared to it.

 The indicated advantages are especially effective when using a video signal sensor on a charge-coupled device in TV systems of astronomical complexes.

For example, expanding the dynamic range of the signal by a factor of 10 will increase the brightness of the analyzed objects, the radiation of which is converted into a digital signal, by a magnitude Δm _v = 2.5 log 10 = - 2.5, while increasing the probability of detecting faint objects (CR and stars) on a complex background.

Claims (1)

 VIDEO SENSOR ON THE DEVICE WITH CHARGING COMMUNICATION, containing a CCD matrix with frame transfer, consisting of single-line sections for storing and storing information and an M-bit read register, the output of which is connected to a CCD channel for transferring charges, divided into two channels connected respectively to the inputs two switched inputs of the first on-off controlled key, the output of which is connected to the input of an analog-to-digital converter, the output of which is connected to one switched input of the second on-off control key and with the input of the multiplication unit, the output of which is connected to the second switched input of the second on-off controlled key, the output of which is the information output of the sensor, and the control inputs of both keys are connected to the output of the comparator, the first input of which is connected to the output of the first amplifier, and the other input is constant threshold voltage input, characterized in that, in order to increase the dynamic range of the signal, additional (N - 1) identical CCD matrices are introduced into it, outputs of output devices The properties of all CCD matrices are connected to the corresponding inputs of the switching unit, the two outputs of which are connected to the inputs of the amplifiers, and all matrices are structurally combined into a multilayer module so that their closely connected accumulation sections form a step-sensitive photosensitive surface in the format of N x M elements, in front of which is located identical configuration end of the fiber optic bundle, the other end of which is the focal plane of the sensor.

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