SU1693396A1 - Coordinate-sensitive device - Google Patents

Abstract

The invention relates to devices for precision measurement of the coordinate position of a light beam. The purpose of the invention is to improve the accuracy by eliminating the temperature drift of the electronic units used. The goal is achieved by alternately connecting the cathodes 12 and 13 of the photodiode (F) 1 through switches 5 and 6 to the operational amplifiers (OA) 2 and 3 and vice versa. The output signals from the OU 2 and 3 are connected to the direct and inverse inputs of the adder (C) 4. This provides modulation of the useful signal at the output (C) 4, the amplitude of which is proportional to the beam offset relative to the center F 1. The signal due to temperature drift has the constant component is excluded from the output signal by the separating element 8. 1 sludge. U S

Description

ABOUT

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The invention relates to a measurement technique and can be used in a wide range of equipment for precision measurement of the position or displacement of a light beam.

The aim of the invention is to improve the accuracy of detecting the displacement of a light beam by eliminating temperature drift and error due to a change in the luminous flux.

The drawing shows a block diagram of the position-sensitive device.

The device contains a two-element coordinate photodiode 1 with a common anode connected to the common bus, operational amplifiers 2 and 3, the non-inverting inputs of which are connected to the common bus, and the outputs connected to the direct and inverse inputs of the adder 4, two switches 5 and 6, generator 7 clock pulses, a separating element 8 and a synchronous detector 9. Operational amplifiers 2 and 3 are covered with logarithmic feedback 10 and 11, their inverting inputs are connected to the outputs of switches 5 and 6, and the first input of the switch 5 is connected to the first cathode 12 of photodiode 1 and to the second input of switch 6, the first input of which is connected to the second cathode 13 of photodiode 1 and to the second input of switch 5, the control inputs of switches 5,6 and synchronous detector 9 are connected to the output of the clock pulse generator 7 , the output of the adder 4 is connected via a separating element 8 to the input of the synchronous detector 9. The separating element can be a capacitor, a transformer, an optocoupler pair.

The device works as follows.

The light beam, which falls simultaneously on two sensitive elements of photodiode 1, generates photocurrent in them, the magnitude of each of which is proportional to the amount of light flux incident on the corresponding element of photodiode 1 and depends on the offset of the center of the light beam relative to the line of separation of the photodiode elements. The photocurrents of the cathodes 12 and 13 of the photodiode at small displacements of the light beam are respectively

| 12 dF (1 + kDH), 113 dF (1-KDH), (1) where g is the sensitivity of photodiode elements;

Ф is the luminous flux incident on one element of the photodiode 1 when the center of the light beam coincides with the line of separation of the sensitive elements of the photodiode:

K - coefficient of proportionality,

defining relationship between the offset

the center of the light beam relative to the line

section of the elements of the photodiode 1 and the change in the photocurrent element of the photodiode.

The generator 7 controls the state of the switches 5 and 6. In one state of the switches 5 and 6, the cathode 12 of the photodiode 1 is connected to the inverting input of the amplifiers 0, body 2, and the cathode 13 to the inverting input of the amplifier 3. At the same time, the voltage on these outputs amplifiers are respectively equal

5 S pt ln (li2 / lN), u3 pt In (FROM / IN))

(2) where RT is the temperature potential of the pn-junction of the logarithmic element 10 (11). IN is the reverse current of the p – n junction of the logarithm element 10 (11).

The voltage at the output of the adder 4 is equal (assuming K AX "1): 1) 41 AX. (3)

In the other state of the switches 5.6, the cathode 12 is connected to the amplifier 3. A. The cathode 13 to the amplifier 2. The voltages at the outputs of the amplifiers are equal

five

 In (hs / lN). U3 prfln h2 / lN). (four)

The voltage on adder 4 becomes equal to 1. one

U -2 p To LH. (five)

Thus, with periodic receipt of clock pulses from the generator

7, at the output of the adder, an alternating signal of ± 2 tpj K AX is formed, which, passing through the separation element 8, in the synchronous detrusor 9 is converted into a constant voltage independent of

of the temperature drift of the voltages of the displacements of the amplifiers 2,3 and of the adder 4. If the transfer coefficients of the adder 4 or of the synchronous detector 9 have a different temperature dependence,

 is provided by using a thermistor in their feedback circuit, then the steepness of the change in output signal will also not depend on temperature.

Claims (1)

The invention of the position-sensitive device containing a two-element coordinate photodiode with a common anode connected to the common bus, two operational amplifiers, non-inverting inputs which are connected to a common bus, and the output terminal is connected to the first photodiode cathode dyes are connected respectively to the direct mode and to the second input of the second switch to the inverse inputs of the adder, about the l and h a-l, the first input of which is connected to You need it so that, in order to increase the second cathode of the photodiode and to the second input precision, the device has two re-5 first switches, a control switch, a clock pulse generator, switch dyes combined with a control element and a synchronous clock input of the synchronous detector and tector, and between the inputs and outputs of the opera-connected to the output of the clock generator the amplifiers included pulses, the output of the adder through the partition of the arrays of the elements, the inverting-10 lithium element is connected to the input of the blue input of the first and second operational synchronous detector, the output of which the amplifiers are connected respectively to the output of the devices to the outputs of the first and second switches, with the first input of the first switching