JPS60162901A - Noncontacting displacement measuring instrument - Google Patents

Abstract

PURPOSE:To remove a temperature drift by sampling outputs of an adding and a subtracting circuit with synchronizing sampling pulses when the extent of displacement is calculated by dividing the difference between outputs of a photodetecting element which outputs the position of a light image of an object as two electrical signals by the sum. CONSTITUTION:A light emitting element 22 is turned on through a driving circuit 21 with the output of a pulse generating circuit 20 to form a light spot 25 on the object 24 of measurement through a light transmitting lens 23 and also convert the position of the light image into an electrical signal by the photodetecting element 27 through a photodetecting lens 26. Two electrical signals from the element 27 are passed through preamplifiers 28 and 29, the subtracting circuit 30, and the adding circuit 31 and a divider 33 divides the difference signal by the sum signal held in a sample holding circuit 32 with sampling pulses A to output the extent of displacement of the light image. Further, a sample holding circuit 35 holds the displacement signal which has its starting point delayed behind the pulse A and the same or earlier ending point with or than the pulse B through a high-pass filter 34.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a non-contact displacement measuring device that measures the distance to a measuring object or its displacement while reducing the influence of external light.
In particular, the present invention relates to a non-contact displacement measuring device that can obtain high measurement accuracy without being affected by temperature drift in a divider.

(B) Prior Art Conventionally, this type of non-contact displacement measuring device, as shown in the block diagram in Fig. 1, first generates a pulse with a pulse generator 1 and drives a semiconductor laser 2 with a predetermined pulse width to emit light. let The emitted light is transmitted to the measurement target 4 by the light transmitting lens 3.
A light spot 5 is formed on the surface of the light receiving element 7 , and the spot 5 is then imaged onto a light receiving element 7 through a light receiving lens 6 .

Next, the output current from the light receiving element 7 is sent to a preamplifier 8.9.
After amplification, a predetermined voltage is obtained by the subtraction circuit 1o and the addition circuit 11, and this voltage is input to the sample and hold circuits 12 and 13. Here, the peak value of the voltage is sampled and held according to the sampler pulse 14 synchronized with the pulse generated by the pulse generator 1.

Then, the divider 15 obtains a signal proportional to the displacement meter of the spot light of the light receiving element 7''. In this way,
The amount of displacement of the object to be measured 4 is measured in a non-contact manner using the light from the semiconductor laser 2 as a medium.

However, since the DC level is input to the divider 15, the temperature drift of the divider 15 becomes large and does not affect the measurement accuracy. In particular, there is a problem that this temperature drift becomes extremely large when the input to the adder circuit is small.For this reason, it is possible to use a high-performance divider, but the measurement equipment would be expensive. There was a problem.

(c) Purpose The present invention aims to solve these problems and provide an inexpensive non-contact displacement measuring device that is not affected by the temperature drift of the divider, has a high measurement degree, and is inexpensive. r Make it white.

(D) Structure: The features of the present invention include a drive pulse for driving the light emitting element, a sampling pulse 8 having the same pulse as this drive pulse, and a pulse starting from this sampling pulse 8. a pulse generator that synchronously outputs a sampling pulse B whose pulse end time is delayed and ends at the same time or earlier; and a light emitting element that receives the driving pulse and generates light in a pulsed form. , a light transmitting lens that forms an image of the pulsed light on the surface of the object to be measured, a light receiving lens that forms a light image on the surface of the object to be measured on a light receiving element Q, and a light receiving lens that forms an image of the light on the surface of the object to be measured, and a light receiving element that outputs the position of the optical image as an electrical signal, an amplifier that amplifies the electrical signal output from the light receiving element, a subtraction circuit that subtracts the amplified electrical signal output from the light receiving element, and an addition circuit. a sample hold circuit that samples the electrical signal added by the adding circuit using the sampling pulse A; and a sample hold circuit that samples the electrical signal added by the adding circuit using the sampling pulse A, and divides the electrical signal subtracted by the subtracting circuit by the added electrical signal, a divider that converts and outputs the amount of displacement of the optical image of the element, and the output signal from the divider is passed through a bypass filter.
The point is that it consists of a sample and hold circuit that samples at .

(B) Embodiment FIG. 2 is a block diagram illustrating an embodiment of the non-contact displacement measuring device according to the present invention. In the figure, reference numeral 20 denotes a pulse generator, and this pulse generator 20 determines the timing of driving a light emitting element 22 such as a semiconductor laser or a light emitting diode, and also determines the timing of driving a light emitting element 22 such as a semiconductor laser or a light emitting diode.
35 sampling times are determined.

21 is a drive circuit that drives the light emitting element 22 based on the pulse pulse of the pulse generator 20;
] is input to the light emitting element 221J, for example, pulse width 1 μs to 100 μs, period Q, +ns to
] Generates pulsed light that repeats at approximately ma.

Reference numeral 23 denotes a light transmitting lens that condenses the light from the light emitting element 22 and forms a light beam 125 on the surface of the object 24 to be measured.

26 is a light receiving lens that images the light spot 25 on the surface of the measurement object 24 on the light receiving element 27, and the position of the light image of the light spot 25 formed by the light receiving lens 26 is determined by the light receiving element 27. converted into an electrical signal. Note that the light-receiving element 27 here outputs an electric signal from both ends, and by dividing the difference between the two electric signals by the sum of the two electric signals, the electric signal at the position of the optical image of the optical subograph h25 can be obtained. Refers to a position detection element. Hereinafter, the term "light receiving element 27" refers to this.

28 and 29 are preamplifiers that amplify the electrical signal from the light receiving element 27, 30 is a subtraction circuit that calculates the difference between the outputs of the preamplifiers 28 and 29, and 31 is an addition circuit that calculates the sum of the outputs of the preamplifiers 28 and 29. be.

32 is a sample hold circuit that samples the electric signal added by the addition path 31 using the sampling pulse 8 from the pulse Q'-IE device 20, and this sampling pulse A is set to be the same as the drive pulse. .

33 is a divider that divides the electrical signal subtracted by the subtraction circuit 30 by the electrical signal output from the sample bold circuit 32 to convert and output the amount of displacement of the optical image of the light receiving element 27. be.

34 is a bypass filter that purifies only the signal displaced from the pulsed light of the light emitting element 22 and does not take it out; 35 is a sample bold that samples the output signal from the divider 33 through the bypass filter 34 and then samples it with a sampling pulse B. It is a circuit.

This sampling pulse B is set so that its pulse start time is delayed from the sampling pulse 8, and its pulse end time is set to end at the same time or earlier. The driving pulse and the sampling pulse A,
, B are output from the generator 20 in synchronization with each other.

Although not shown, a bypass filter 34 is appropriately inserted between the light receiving element 27 and the subtraction circuit 30 and addition circuit 31.

Next, the temporal relationship of the operation of the system shown in the block diagram of FIG. 2 will be explained based on timing charts 1 to 3 of FIG. 3.

The operations from the pulse generator 20 to the subtraction circuit 30 and the addition circuit 3 are the same as those in the previous embodiment, so a description thereof will be omitted.
1ll! do. When the output signal of the adder circuit 31 is sampled and held using the sampling pulse A, it becomes a waveform with short steps as shown by the broken line. The reason for sampling and holding here is that it is necessary to quickly recover in the next light emitting period of the light emitting element 22.If sample bold is not used, the added output will be Ov during the period in which the light emitting element 22 does not emit light, as shown by the solid line. Since the waveform has a long step, the output of the divider 33 becomes saturated or undefined. This results in a longer recovery time.

The output signal from the divider 33, which divides the subtraction output by the addition output sampled and bolded with this sampling pulse A, generally has a waveform with a blunted rise as shown in the figure.

When this output signal is sampled by the sampling pulse B through the bypass filter 34, the peak value of the output signal of the bypass filter 34 is maintained and converted into a continuous signal, which is proportional to the amount of displacement of the optical image on the light receiving element 22. A signal is output.

(f) Effects The present invention has effectively achieved the intended purpose with the configuration described in detail below. In particular, even if a temperature drift occurs in the divider, the output signal from the divider is passed through the bypass filter, so the temperature drift does not affect measurement accuracy. In addition, since a sample hold circuit is provided that samples with sampling pulse B after passing through a bypass filter, the influence of the blunt rise of the output of the divider is reduced, and the sampled output of the divider becomes the desired displacement output. .

In addition, there is an offset in the output of the divider, and a trimmer is required to adjust this, but as mentioned above, the output of the divider is passed through the bypass filter and then input to the sample and hold circuit, so the offset is There is no influence due to
Since the l-lima can be omitted, the adjustment of the divider becomes easy. In this way, a non-contact displacement measuring device with high measurement accuracy and low cost can be obtained without using a high-performance divider.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating a conventional non-contact displacement measuring device, FIG. 2 is a block diagram illustrating an embodiment of the non-contact displacement measuring device according to the present invention, and FIG. 3 is a timing chart illustrating the temporal relationship of operations of the system shown in the block diagram. 20... Pulse generator, 22... Light emitting element, 23.
...Light sending lens, 24...Measurement object, 26...0 - Light receiving lens, 27...Light receiving element, 28.29...
Amplifier, 30... Subtraction circuit, 31... Addition circuit, 3
2.35... Sample hold circuit, 33... Divider, 34... Bypass filter, A, B... Sampling pulse. Patent applicant Reed Electric Co., Ltd. Agent Patent attorney Takaharu Ohnishi 1

Claims (1)

[Claims] (1) A driving pulse for driving a light-emitting element, a sampling pulse 8 having a pulse set to be the same as this driving pulse, and a pulse start time delayed from this sampling pulse 8, and a pulse end time at the same time or earlier. a pulse generator that outputs the sampling pulse B that finishes early in synchronization with each other; a light emitting element that receives the drive pulse and generates pulsed light; and a light emitting element that generates pulsed light on the surface of the object to be measured. A light transmitting lens that forms an image, a light receiving lens that forms a light image on the surface of the object to be measured on a light receiving element, and a light receiving element that outputs the position of the light image formed on the light receiving element as an electrical signal. , an amplifier that amplifies the electrical signal output from the light receiving element; a subtraction circuit that subtracts the amplified electrical signal output from the light receiving element; and an addition circuit that adds the electrical signal that is added by the addition circuit; A sample hold circuit performs sampling using the sampling pulse 8, and the electric signal subtracted by the subtraction circuit is divided by the added electric signal to convert and output the amount of displacement of the optical image of the light receiving element. A non-contact displacement measuring device comprising: a divider that outputs a signal from the divider; and a Samplepoort circuit that passes an output signal from the divider through a bypass filter and then samples it with the sampling pulse I3.