JPH06307810A - Optical displacement meter - Google Patents

Abstract

(57) [Summary] [Purpose] To measure the displacement of the measured object with high accuracy even if the light intensity changes. [Structure] A position detection element 3 for receiving and photoelectrically converting reflected light from the surface of the DUT 6 which moves in response to displacement of the surface of the DUT 6, and a signal I ₁ from the position detection element 3, I
Gain controllable amplification circuits 14 and 15 for amplifying ₂ to a level necessary for calculating the displacement, and amplification circuit 1
A / D conversion circuit 18, CPU 13, and signal I as detecting means for intermittently detecting the output signal levels from 4, 15
_As means for updating the gains of the amplifier circuits 14 and 15 based on the detected values of the levels of ₁ and I _{2 so that} the levels of the signals I ₁ and I ₂ are within the measurable range, based on the detected values. CPU 13 of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical displacement meter for measuring the displacement amount of an object to be measured with high accuracy even if the light amount changes.

[0002]

2. Description of the Related Art A laser displacement meter can measure a distance (displacement amount) of an object to be measured with high accuracy in a non-contact manner. The measuring principle is optically based on triangulation. Therefore, it is said that the measurement accuracy is less affected by the color of the measured object. However, when the required measurement accuracy is higher than 50 μm, the amount of reflected light changes significantly depending on the surface condition (presence or absence of gloss, presence or absence of dirt, etc.) of the measured object. Then, it is difficult to maintain the accuracy because the electric signal is saturated or the noise ratio (S / N) is deteriorated. Therefore, conventionally, the optimum gain setting (teaching) is started by the object to be measured externally or manually before starting the measurement. In the conventional device, this operation was performed only once immediately after the start of the normal work, and was not updated until the unmeasurable alarm was output.

[0003]

In the conventional apparatus, for example, when measuring the thickness of a continuous sheet-like object,
It is not possible to follow changes in the surface condition of the object to be measured, so the measurement accuracy has deteriorated without knowing it, and a large number of defective or extremely close to defective products have been made, or frequent unmeasurable alarms. However, there was an inconvenience that it was necessary to manually reconfigure.

Therefore, an object of the present invention is to provide an optical displacement meter which solves the above problems.

[0005]

In order to achieve the above object, the present invention provides a position detecting means for receiving and photoelectrically converting the reflected light from the surface of the object to be measured which moves in response to the displacement of the surface of the object to be measured. A gain controllable amplification means for amplifying a signal from the position detection means to a level necessary for calculating the displacement, a detection means for intermittently detecting an output signal level from the amplification means, and the detection Each time the detection value of the output signal level from the amplification means is obtained by the means, means for updating the gain of the amplification means so that the output signal level falls within the measurable range based on the detection value. It is characterized by having

[0006]

According to the present invention, for example, the output signal level from the amplifying means is periodically detected, and the gain of the amplifying means is adjusted so that the output signal level falls within the measurable range each time the detected value is obtained. Update.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a system configuration diagram of a laser displacement meter according to an embodiment of the present invention. Reference numeral 1 denotes a sensor unit, which has a semiconductor laser (LD) 2 and a position detection element 3, and the semiconductor laser 2 is driven by a drive circuit 4 which responds to a drive signal, which will be described later in detail, and emits light. The light from the semiconductor laser 2 is focused by the lens 5 and applied to the DUT 6, is reflected there, and is received by the position detection element 3 through the lens 7. The two detection signals at the position I ₁ and the position I ₂ from the position detecting element 3 are amplified by the amplifier circuit 8,
Is output. 9 is a temperature sensor.

A controller 10 has the following structure. Reference numeral 11 denotes a gain control determination circuit, which detects a light emission amount detection signal of the semiconductor laser 2 from a photodiode provided close to the semiconductor laser 2 and an amplifier circuit 8.
The detection signal of the position I _{1 and} the detection signal of the position I ₂ are added, and the addition signal from the addition circuit 12 is input, and the ratio between the emission light amount detection signal and the addition signal is calculated there To do. Position I ₁ from amplifier circuit 8
The detection signals of I ₂ and I ₂ are amplified by the gain variable amplification circuits 14 and 15 according to the control signal from the CPU 13, and are input to the addition circuit 16 for adding these and the subtraction circuit 17 for subtracting them. The output signals of the adder circuit 16, the subtractor circuit 17 and the temperature sensor 9 are converted into digital data by the A / D conversion circuit 18 and input to the CPU 13. The CPU 13 calculates the displacement amount (AB) of the surface of the DUT 6 by a well-known method based on the output of the addition circuit 16 and the output of the subtraction circuit 17, and digitally outputs the result to D / A conversion. Analog output via circuit 19,
Furthermore, it displays on the display 20. Further, the CPU 13 monitors the temperature of the semiconductor laser 2 with the temperature sensor 9. Reference numeral 21 denotes a light amount control circuit, which generates a drive signal based on a reference value 22 and inputs it to the drive circuit 4 when the operation of the laser displacement meter is started (the semiconductor laser 2 emits light with a predetermined light emission amount). ), And thereafter the reference value 22 and the addition circuit 1
Based on the difference from the signal value from 6, a drive signal is generated so that the semiconductor laser 2 can obtain a predetermined amount of light emission. A timer 23 counts up every set time and inputs an interrupt signal to the CPU 13. The set time, that is, the interrupt time interval, is obtained from the length of the object to be measured, the transport speed, etc., is set by a setter such as a keyboard or dip switch, and is set in the timer 23 via the CPU 13.

Next, the operation of the CPU at the time of timer interruption will be described with reference to FIG.

When a timer interrupt occurs, first, the level at which the gains of the amplifiers 14 and 15 at that time are set is read (S1). Then, whether or not the sensor unit 1 of the laser displacement meter is in a position within the measurement range with respect to the DUT 6 (that is, outside the measurement range when it is too far or too close) is determined via the A / D conversion circuit 18. Two amplifier circuits 14 and 1 based on the received light signal of the position detection element 3 obtained by
Judgment is made based on the addition level of the signal from 5 (S2),
If it is within the measurement range, it is determined whether or not the received light amount for measuring can be obtained based on the addition level and the subtraction level of the signals from the two amplifier circuits 14 and 15, that is, whether or not the received light amount is insufficient. , Or whether the amount of received light is excessive (S3, S4), and when the amount of received light is insufficient, it is determined whether the gains of the amplifier circuits 14 and 15 at that time are maximum (S3).
5) If not maximum, a signal for increasing the rank gain by 1 is output to the amplifier circuits 14 and 15 (S6), and then it is determined whether or not the insufficient received light amount has been resolved (S7). Repeat. On the other hand, when the amount of received light is excessive in S4, it is determined whether or not the gains of the amplifier circuits 14 and 15 at that time are minimum (S8). Output to (S
9) Then, it is judged whether or not the excessive amount of received light has been resolved (S
10), S8 to S10 are repeated until the problem is resolved. When the gains of the amplifier circuits 14 and 15 are maximum and the amount of received light is insufficient (S5)
Also, when the gains of the amplifier circuits 14 and 15 are minimum and the amount of received light is excessive (S8), it is not measured.

The gain switching of the amplifier circuits 14 and 15 is a very general method, for example, the feedback resistance of an operational amplifier is switched by an analog switch. The switching signal is supplied from the CPU 13. As another method, an operational amplifier having a gain switching function built into an amplifier circuit may be used.

As described above, when measuring the thickness, step, etc. of a continuously flowing sheet material, for example, if the surface condition of the object to be measured changes, a measurement error has conventionally occurred. However, as described above, according to the present invention, for example, the amount of reflected light is checked at regular intervals, and by controlling the gain of the amplifier circuit to be always optimum at that time, a measurement error does not occur and a high accuracy is obtained. Can measure. Therefore, in the conventional method, an alarm or the like is frequently generated, and the gain is manually corrected one by one, but it is unnecessary in the present invention, and the production efficiency is improved. Furthermore, the quality of the product can be maintained with high accuracy.

[0014]

As described above, according to the present invention, the displacement amount of the object to be measured can be measured with high accuracy even if the light amount changes.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a flow chart showing the operation of the embodiment.

[Explanation of symbols]

 2 semiconductor laser 3 position detection element 13 CPU 14, 15 amplification circuit 16 addition circuit 18 A / D conversion circuit

Claims (1)

[Claims] 1. A position detecting means for receiving and photoelectrically converting reflected light from the surface of the object to be measured which moves in response to the displacement of the surface of the object to be measured, and a signal from the position detecting means for calculating the displacement. A gain controllable amplification means for amplifying to a level necessary for the detection, a detection means for intermittently detecting the output signal level from the amplification means, and a detection value of the output signal level from the amplification means by the detection means. The optical displacement meter is characterized in that it comprises means for updating the gain of the amplifying means so that the output signal level falls within a measurable range based on the detected value.