RU2026607C1 - Two-coordinate laser movement-to-code converter - Google Patents

Abstract

FIELD: computer engineering, measurement technology. SUBSTANCE: two-coordinate laser movement-to-code converter has radiator 1, four-square photodetector 2, integrators 3 and 4, selection and storage circuits 5 and 6, voltage-to-time interval converters 7 and 8, keys 9 and 10, code computation unit 11. Converter is supplemented with current-to-voltage converters 12, 13, 14 and 15, detectors 16, 17, 18 and 19, pulse former 20, counter 21 and modulator 22. Insertion of additional elements with proper couplings makes it possible to reduce level of noise across outputs of photodetector 2 and to rectify influence of background noise and temperature drifts of photodetector 2. EFFECT: increased precision of conversion. 1 dwg

Description

 The invention relates to information-measuring and computer engineering and can be used, in particular, in the welding industry with the operational control of welding movements and deformations of a wide class of products during the welding process.

 A device for measuring two coordinates of a controlled point of an object relative to the reference axis, which is specified by a laser beam [1]. This device also contains a four-quadrant photodetector and an analog signal processing unit. The four-quadrant photodetector consists of a dividing prism and four photodiodes mounted behind it. The laser beam defining the reference axis is divided by a prism into four light fluxes incident on the corresponding photodiodes. The orientation of the separation prism is defined by a rectangular coordinate system. In the block of analog signal processing, information signals of coordinates and the total signal from the photodiodes of the four quadrants are extracted.

 A disadvantage of the known device is the design complexity of the analog signal processing unit, the use of an analog signal splitter and, as a result, the low accuracy of displacement measurement.

The closest to the invention in terms of technical nature and the achieved result is a two-coordinate transducer to code, containing an emitter, which uses a laser, a four-quadrant photodetector and an analog iterative converter, consisting of an adder, two integrators, two sampling and storage circuits, two voltage converters the time interval covered by feedback through two keys, as well as a block for calculating codes N _x and N _y proportional to the coordinates X and Y of the controlled point ki of the object relative to the reference beam of the emitter [2]. The conversion cycle in a known converter is set by a generator.

 A laser beam defining a reference (reference) axis hits a four-quadrant photodetector. The orientation of the separation zones between the quadrants coincides with the direction of the X and Y coordinate axes.

In the block for calculating the codes, the time intervals T _x , T _y, and T _c are converted into codes N _x and N _y proportional to the coordinates X and Y of the controlled point of the object relative to the emitter beam.

 The advantages of the known converter include non-contact measurement method, simplicity of the sensing element associated with the absence of mechanical parts, high sensitivity to movements. The disadvantages of the known device are the small value of the signal-to-noise ratio at the outputs of the sensitive elements of the quadrant photodetector due to the lack of a short circuit mode, the large error in the summation of the signals of the photodiodes by an analog adder, the strong influence of background illumination and temperature drifts of the dark currents of the photodetector, and the difficulty in tuning.

 The aim of the present invention is to improve the accuracy of the Converter.

 This goal is achieved by the fact that in the two-coordinate transducer to the code containing the emitter, optically coupled to a four-quadrant photodetector, the first and second integrators, the outputs of which are connected to the information inputs of the first and second sampling and storage devices, the outputs of which are connected to the information inputs of the first and the second voltage-time interval converters, the outputs of which are connected respectively to the first and second inputs of the code calculation unit, the outputs of which are the outputs of the converter, and with the control inputs of the first and second keys, respectively, the information inputs of which are combined with the first inputs of the first and second integrators respectively, the control inputs of the sampling-storage device, the start-up inputs of the voltage-time interval converters and the third input of the code calculation unit are combined according to the invention, four current-voltage converters, four detectors, a pulse shaper, a counter and a modulator located between the radiation an atel and a four-quadrant photodetector, the outputs of the first and second quadrants of which are connected to the inputs of the first and second current-voltage converters, the output of the third quadrant of the four-quadrant photodetector is connected to the common potential bus, and the common point of all quadrants of the four-quadrant photodetector is connected to the input of the third current-voltage converter, the output of the fourth quadrant of the quadrant photodetector is connected to the input of the fourth current-voltage converter, the outputs of current-voltage detectors are connected to the inputs of the detectors of the same name, the outputs of the first detector are connected to the second inputs of the first and second integrators, the outputs of the second and fourth detectors are connected to the third inputs of the first and second integrators respectively, the output of the third detector is connected to the information input of the keys, the output of the third current converter -voltage is connected to the input of the pulse shaper, the output of which is connected to the counting input of the counter, the output of which is connected to the third input of the calculating unit codes, and the installation inputs of the counter are the control inputs of the converter.

 The drawing shows a functional diagram of a two-coordinate transducer of displacement into code, as well as a schematic representation of the orientation of the quadrants relative to the coordinate axes.

 The two-coordinate displacement transducer to code contains an emitter 1, a four-quadrant photodetector 2, the first and second integrators 3 and 4, respectively, the first and second sampling-storage devices 5 and 6, respectively, the first and second voltage-time converters 7 and 8, respectively, the first and second keys 9 and 10, respectively, block for calculating codes 11, first, second, third and fourth converters 12, 13, 14, 15, respectively, first, second, third and fourth detectors 16, 17, 18 and 19, respectively, pulse shaper 20 counter 21 and modulator 22.

The emitter 1 is mounted on a fixed base snap and is used to set the reference axis. The four-quadrant photodetector 2 is optically coupled to the emitter 1 and is mounted at a controlled point on the object. The outputs of the integrators 3 and 4 are connected to the information inputs of the sample-storage devices 5 and 6, respectively. The outputs of the sample-storage devices 5 and 6 are connected to the information inputs of the first and second voltage-time converters 7 and 8, respectively, the outputs of the latter are connected to the control inputs of the keys 9 and 10 and the first and second inputs of the block for computing codes 11, respectively. In this case, the output of the keys 9 and 10 is connected to the first input of the integrators 3 and 4. The control inputs of the sample-storage devices 5 and 6, the start inputs of the voltage-time interval converters 7 and 8, and the third input of the code calculation unit 11 are combined. The outputs N _x and N _{y of the} block computing codes 11 are the outputs of the device. The inputs of the current-voltage converters 12-15 are connected to the three outputs of the four-quadrant photodetector 2 and its common point, and the outputs are connected to the inputs of the detectors 16 - 19, respectively. The inputs of the first and second quadrants of the quadrant photodetector 2 are connected to the inputs of the first and second current-voltage converters 12 and 13, respectively. The output of the third quadrant of photodetector 2 is connected to the common potential bus, and the common point of all quadrants is connected to the input of the third current-voltage converter 14. The output of the fourth quadrant of photodetector 2 is connected to the input of the fourth current-voltage converter 15.

 The outputs of the converters 12, 13, 14 and 15 are connected to the inputs of the detectors of the same name 16, 17, 18 and 19. The output of the first detector 16 is connected to the second inputs of the integrators 3 and 4. The outputs of the second and fourth detectors 17 and 19 are respectively connected to the third inputs integrators 3 and 4, and the output of the third detector 18 to the common input of keys 9 and 10.

 The output of the pulse shaper 20 is connected to the counting input of the counter 21, the output of which, in turn, is connected to the third input of the block 11. The installation inputs of the counter 21 are the control inputs of the converter. The modulator 22 is located on the path of the light flux from the emitter 1 to the photodetector 2.

The proposed device operates as follows. Using a modulator 22, the light flux of the emitter 1, incident on a four-quadrant photodetector 2, is modulated with a frequency of f _m The converters 12-15 are connected to the corresponding outputs of the photodetector 2 according to a certain rule. This rule is determined by the relative position of the quadrants (in the drawing, the quadrants are marked with Roman numerals I, II, III and IV) and their orientation relative to the coordinate axes X and Y. When the coordinate axes X and Y pass through the center of the photodetector 2, the first quadrant (1) corresponds to a positive direction X and Y axes, and the rest are numbered sequentially counterclockwise, starting with quadrant I.

 The voltage at the outputs of the current-voltage converters 12-15 repeat the law of change in luminous flux. In this case, the voltage phase at the output of the current-voltage converter 14 is shifted by half the period compared with the voltage phase at the outputs of the current-voltage converters 12, 13, and 15. The voltage amplitudes at the outputs of these converters are directly proportional to the light flux incident on the corresponding element of the quadrant photodetector 2 , and the voltage amplitude at the output of block 14 is directly proportional to the total luminous flux incident on all four quadrants of photodetector 2 (this is due to the connection I input the converter 14 to the common point of the quadrant photodetector 2). The sign of the voltage at the output of the detector 18 is opposite to the sign of the voltage at the outputs of the detectors 16, 17 and 19.

= k

(1)
y = kU_y= k

= k

(2) где К - коэффициент передачи преобразователя, U_Σ = U₁ + U₂ + U₃ + U₄;
U₁, U₂, U₃, U₄ - напряжения на выходах соответствующих детекторов.The coordinates of the center of the light flux relative to the center of the four-quadrant photodetector 2 are determined by the following expressions:
x = kU _x = k

= k

(1)
y = kU _y = k

= k

(2) where K is the transfer coefficient of the converter, U _Σ = U ₁ + U ₂ + U ₃ + U ₄ ;
U ₁ , U ₂ , U ₃ , U ₄ - voltage at the outputs of the respective detectors.

; y= K

(3)
В составе предлагаемого преобразователя можно выделить два идентичных канала преобразования: канал преобразования координаты X (интегратор 4, устройство 6, преобразователь 8, ключ 10) и канал преобразования координаты Y (интегратор 3, устройство 5, преобразователь 7 и ключ 9), являющихся итерационными преобразователями отношения напряжений в интервал времени. В установившемся режиме интервалы времени T'_x и T'_y определяются выражениями:
T

=

·T_ц; T

=

·T_ц (4) При этом интервал времени T_ц формируется при помощи формирователя 20 и счетчика 21 и определяется выражением
T_ц=

(5) где N - значение кода, задаваемого на входе преобразователя в зависимости от необходимого интервала усреднения. Подставляя (4) в (3) можно получить
x = K

- 1

; y = K

- 1

(6)
Последние выражения можно переписать в виде
T_x=

· X = 2T

- T_ц;
T_y = 2T'_y - T_ц . (7) Таким образом, предлагаемый преобразователь обеспечивает более высокую точность преобразования, обусловленную рядом причин:
- обеспечением режима короткого замыкания для квадрантного фотодетектора 2 за счет подключения всех его выходов к входам преобразователей ток-напряжение, находящихся под потенциалом общей точки преобразователя, что позволяет получить низкий уровень шумов на выходах фотодетектора 2;
- отсутствием в схеме сумматора, точность коэффициента преобразования которого в прототипе задавалась пятью резисторами;
- устранением влияния фоновой засветки, температурных дрейфов фототоков четырехквадрантного фотодетектора и аддитивных погрешностей на входе устройства путем введения модуляции светового потока и обеспечения работы устройства на переменном токе.Denoting U ' _x = U ₁ + U ₄ ; U ' _y = U ₁ + U ₂ , we obtain the following expressions:
x = K ²

; y = K

(3)
As part of the proposed converter, two identical conversion channels can be distinguished: the coordinate transformation channel X (integrator 4, device 6, converter 8, key 10) and the coordinate transformation channel Y (integrator 3, device 5, converter 7 and key 9), which are iterative converters stress relations in a time interval. In the steady state, the time intervals T ' _x and T' _{y are} determined by the expressions:
T

=

· T _c ; T

=

· T _c (4) In this case, the time interval T _c is formed using the shaper 20 and the counter 21 and is determined by the expression
T _c =

(5) where N is the value of the code specified at the input of the converter depending on the required averaging interval. Substituting (4) into (3) we can obtain
x = K

- 1

; y = K

- 1

(6)
Recent expressions can be rewritten as
T _x =

X = 2T

- T _c ;
T _y = 2T ' _y - T _c . (7) Thus, the proposed Converter provides a higher conversion accuracy, due to several reasons:
- providing a short circuit mode for the quadrant photodetector 2 by connecting all its outputs to the inputs of the current-voltage converters under the potential of the common point of the converter, which allows to obtain a low noise level at the outputs of the photodetector 2;
- the absence of an adder in the circuit, the accuracy of the conversion coefficient of which in the prototype was set by five resistors;
- elimination of the influence of background illumination, temperature drifts of the photocurrents of the quadrant photodetector and additive errors at the input of the device by introducing light modulation and ensuring the operation of the device on alternating current.

 In addition, an important advantage of the proposed two-coordinate transducer to displacements into code is the simplicity of its configuration, due to the lack of an adder and the use of fewer tuning resistors.

Claims (1)

 TWO-ORDER LASER TRANSFER OF TRANSFER TO CODE, comprising an emitter optically coupled to a four-square photodetector, first and second integrators, the outputs of which are connected to the information inputs of the first and second sampling-storage devices, the outputs of which are connected to the information inputs of the first and second voltage-to-interval converters time, the outputs of which are connected respectively with the first and second inputs of the block computing codes, the outputs of which are outputs of the converter, and with the control inputs of the first and second keys, respectively, the information inputs of which are combined, and the outputs are connected with the first inputs of the first and second integrators, respectively, the control inputs of the sample-storage device, the start-up inputs of the voltage-time interval converters, and the third input of the code calculation unit combined, characterized in that, in order to increase the accuracy of the converter, four current-voltage converters, four detectors, a pulse shaper, a counter are introduced into it and a modulator located between the emitter and the four-square photodetector, the outputs of the first and second quadrants of which are connected to the inputs of the first and second current-voltage converters, the output of the third quadrant of the four-quadrant photodetector is connected to the common potential bus, and the common point of all quadrants of the four-quadrant photodetector is connected to the input of the third current-voltage converter, the output of the fourth quadrant of the four-quadrant photodetector is connected to the input of the fourth converter a current-voltage converter, the outputs of current-voltage converters are connected to the inputs of the detectors of the same name, the output of the first detector is connected to the second inputs of the first and second integrators, the outputs of the second and fourth detectors are connected to the third inputs of the first and second integrators, the output of the third detector is connected to the information input the first key, the output of the third current-voltage converter is connected to the input of the pulse shaper, the output of which is connected to the counting input of the counter, the output of which is connected Inen with the third input of the code calculation unit, and the installation inputs of the counter are the control inputs of the converter.