JPS60170706A - Optical surface displacement detecting circuit - Google Patents

Abstract

PURPOSE:To improve detection precision by detecting two intersections each of a reference signal and the 1st threshold value, and its reflected signal and the 2nd threshold value, and calculating the time interval of generation between the reference signal and reflected signal from the numbers of clock pulses between the two couples of intersections. CONSTITUTION:A laser beam is made incident on a reference light detecting element 28. The reference signal S1 outputted by the reference light detecting element 24 and the reflected signal S2 outputted by a reflected light detecting element 28 are amplified by amplifiers 46 and 48. Two intersections P11 and P12 of the reference signal S1 and the 1st threshold value Vref1 are detected by the 1st detector 54 and two intersections P21 and P22 of the reflected signal S2 and the 2nd threshold value Vref2 are detected by the 2nd detector 56. Then, the number A of clock pulses generated between the intersections P11 and P21 and the number B of clock pulses generated between the intersections P12 and P22 are counted by the 1st and the 2nd counters 62 and 64 respectively and the time interval of generation between the reference signal and reflected signal is calculated by arithmetic. Then, a displacement converter 70 converts the generation time interval into displacement, which is displayed on a display device 72.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical surface displacement detection circuit, and is particularly suitable for use in an optical surface displacement detection device that can measure the thickness, displacement, etc. of a remote object without contact. , out of the reference signal output from the reference light detection element arranged corresponding to the reference position of the beam scanning range and the beam reflected by the measurement target surface, only the reflected light in a set direction different from the beam irradiation direction is detected. The present invention relates to an improvement in an optical surface displacement detection circuit for determining displacement in a set direction of a surface to be measured from the generation time interval of a reflected signal output from a reflected light detection element configured to receive light.

With the automation of production and the introduction of robots in industry, in-process measurement, higher speed, and higher accuracy are rapidly gaining ground. In addition, there is a growing need for a surface displacement detection device that can measure the thickness, displacement, etc. of a remote object in a non-contact manner.

Such non-contact surface displacement detection devices include those that use an optical displacement method that uses reflected light and scattered light of the light projected onto the object to be measured as signals related to displacement, magnetic flux changes, eddy currents, capacitance changes, etc. etc., which utilize the effect of electromagnetic fishing spots,
Methods that utilize radiation absorption and methods that utilize ultrasonic waves have been proposed. A surface displacement detection device (referred to as a surface displacement detection device) is advantageous.

Various methods have been proposed as this optical surface displacement detection device, and one of them, for example, as shown in FIG.
A rotating mirror 22 for rotating and scanning a spot-shaped laser beam 21 generated from zero at a constant angular velocity, and a rotating scanning beam 23 formed by the rotating mirror 22,
Of the light reflected by the reference light detection element 24 for detecting that the reference position has been scanned and the measurement target surface 10 of the rotating scanning beam 23, only the reflected light in the direction perpendicular to the measurement target surface 10 (displacement measurement direction) is detected. The reference light detecting element 24 includes a slit 26 through which the light passes through, and a reflected light detecting element 28 for detecting the presence or absence of reflected light that has passed through the slit 26, and is measured by a displacement detecting circuit 29. The vertical displacement x of the surface to be measured 10 is calculated from the generation time interval between the reference signal and the reflected signal output from the reflected light detection element 28, that is, the scanning angle θ of the rotating scanning beam 23. Some use a projection beam rotation scanning method.

Furthermore, in the projection beam rotational scanning method shown in FIG. b) Distance m between the rotation mirror 22 and the measurement target surface 10
β1, Bu2, (3rd etc.) need to be tightened 4 times.
9708, as shown in FIG. 2, between the rotating mirror 22 and the surface to be measured 10, there is provided a filter for converting the rotating scanning beam 23 rotated and scanned in a fan shape by the rotating mirror 22 into parallel scanning beams 31 parallel to each other. By inserting a collimator lens 30, an optical linear relationship is established between the scanning angle θ of a rotating scanning beam 23 and the displacement amount x of a surface to be measured 10, thereby easily performing highly accurate measurement. We are proposing a projection parallel scanning system that allows for

However, in either of the optical surface displacement detection devices shown in FIG. 1 or FIG. It is necessary to accurately measure
For this purpose, it is necessary to precisely adjust the edge positions or center positions of the reference signal and the reflected signal.

On the other hand, the applicant has already developed an edge detection device for optical measuring instruments in Japanese Patent Application Laid-open No. 58-173408 and Japanese Patent Application No. 58-173.
-102477, Utility Application No. 58-87424, etc.
Although various methods have been proposed,
As proposed in 08, four light-receiving elements arranged in a plane substantially parallel to the movement plane so as to generate at least two sets of phase-shifted signals based on the brightness and darkness that occur when moving relative to the object to be measured. a sensor comprising a sensor, first and second calculation means for calculating the difference between the phase shift signals of the respective phases, a third calculation means for calculating the difference between the output signals of the first and second calculation means; A fourth calculation means for calculating the sum, and a cross signal between the output a of the third calculation means and the reference bell, which is generated while the output signal of the fourth calculation means is at a predetermined level. Although the edge detection device including the detection means for outputting the edge detection device is suitable for a projector, it has a very complicated configuration to be used as it is in an optical surface displacement detection device. In addition, as proposed in Tokuchi Sho 58-102477, the light receiver is formed from two light-receiving elements divided into two in the direction in which the image of the object to be measured travels, and the output signals of these light-receiving elements are differentiated. A differential circuit that calculates the difference between the output signals of these differentiating circuits, and an output signal from this differential circuit:
The edge detection device, which includes a judgment circuit that compares the signal with a reference signal and determines one point that is an edge of the object to be measured, is suitable for a high-speed scanning laser length measuring machine in which the waveforms of the two output signals are almost the same. However, in general, the waveforms of the reference signal and the reflected signal are significantly different because the apparent diameter of the reflected light differs due to the scattered light, and in particular, the reflected signal tends to have an asymmetrical waveform.Optical surface displacement detection Not suitable for use in equipment as is. Furthermore, as proposed in Utility Model Application No. 58-87424, a part of the light beam can be detected immediately before the object to be measured.
A light amount detection means that converts the light amount fluctuation into an electrical signal and outputs it is provided, and the light amount detection means is connected to the light amount detection means so that the output device serves as a reference signal in the determination device or a correction signal for the light receiver output signal. The connected edge detection device also had the problem that it was not suitable for use as it was in an optical surface displacement detection device.

Also, in order to overcome the difference in waveform between the reference signal and the reflected signal,
It is conceivable to directly capture the midpoint of each output signal and determine the time interval from those intervals, but the method of using, for example, the second-order tR2 when detecting the midpoint of each output signal requires a small and complicated circuit. Not only that, but also it is difficult to determine the exact midpoint.

The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to accurately determine the time interval corresponding to the intermediate point using a simple circuit, without directly determining the intermediate point between the reference signal and the foul signal. The second object of the present invention is to provide an optical surface displacement detection circuit.

The present invention uses the reference No. 15 output from the miscellaneous light detection element arranged corresponding to the reference position of the beam scanning range and the beam reflected by the measurement target surface in a setting direction different from the beam irradiation direction. In an optical surface displacement detection circuit for determining displacement in a set direction of a surface to be measured from the generation time interval of a foul signal output from a reflected light detection element configured to receive only reflected light, the reference signal and a first setter that generates a first threshold that intersects at two positions; a second setter that generates a second threshold that intersects the reflected signal at two positions; and two intersections of the reference signal and the first interval. A first detector that detects the position, a second detector that detects the two intersection positions of the reflected signal and the second threshold value, and a second detector that detects the intersection position between the corresponding pair of intersection positions detected by each detector. a first counter that counts clock pulses detected by each detector;
A second counter that counts clock pulses generated between another pair of correlated intersection positions, and the number of pulses counted by both counters is calculated to calculate the generation time interval of the reflected signal such as the reference signal. By having a computing unit that
The above objective has been achieved.

Further, in an embodiment of the present invention, the first setting device and the second setting device hold the maximum value of the reference light detection element output or the reflected light detection element output, and divide the holding signal to set the first setting device. As a device that generates the threshold value or the second threshold value, it is not affected by fluctuations in the peak value of the reference signal or reflected signal due to scattered light or power fluctuations, etc., and can perform highly accurate measurements even with asymmetric waveforms. It is something.

Furthermore, another embodiment of the present invention provides a comparator for comparing the first detector and the second detector with the reference signal or the reflected signal and a first threshold value or a 21st JI chain, and a rectangular shape of the output of the comparator. It is composed of a digital differentiation circuit that digitally processes the wave Iris signal and generates a pulse signal corresponding to the two crossing positions, and easily determines the two crossing positions of the reference signal or reflected signal and the first threshold value or the second threshold value. It is designed so that it can be detected.

In this light, two crossing positions of the reference signal and the first threshold value and two crossing positions of the reflected signal and the second dark value are respectively detected, and a clock generated between the two pairs of corresponding crossing positions is detected. By counting each pulse and calculating the number of both pulses, the time interval between the occurrence of the reference fg signal and the reflected signal is determined. It is possible to precisely adjust the generation time interval between the pulse signal, that is, the reference signal and the reflected signal, which corresponds to the interval between the intermediate points.

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

As shown in FIG. 3, this embodiment uses a laser beam generator 20, a rotating mirror 22, a photodiode, and a reference light detector, similar to the conventional example shown in FIG. an element 24, a slit 26, a reflected light detection element 28 made of, for example, a photodiode, a displacement detection circuit 29,
In the optical surface displacement detection device having a collimator lens 30, a mirror 40 is provided at a reference position in the parallel scanning beam 31, and the mirror 40 allows the reference light detection element 2 to be detected by the mirror 40.
8 is configured to emit a laser beam through a lens 41 and a slit 42, and the displacement detection circuit 2
9, amplifiers 46 and 48 that amplify the reference signal S1 of the output of the M single light detection element 24 and the reflection signal S2 of the output of the reflected light detection element 28, respectively, and a first amplifier that intersects the reference signal 81 at two positions. a first setter 50 that generates a threshold value vrf3F+; a second setter 52 that generates a second I8I value Vrerz that intersects the reflected signal 82 at two positions; a first detector 54 that detects two cross points 1ifP11, P12;
The second detector 56 detects the two intersection positions P21TP22 of the reflected signal S2 and the second threshold value vref2, and the corresponding intersection positions detected by each detector 54, 56 (1)
For example, P 1+ and P 21, P 12 and P
22, the clock pulse generator 60, and each detector 54. First counter 62 for counting
and a second counter 64 that counts the number of clock pulses B generated between the other pair of correlated intersection positions P+2 to P22 detected by each detector 54.56, and both counters 62.64. a calculator 66 which calculates the generation time interval between the reference signal and the reflected signal by calculating the number of both pulses counted;
and a third setter 68 for inputting a set value that relates the generation time interval and the displacement 11x, and the generation time interval of the output of the calculator 66 using the setting (to 1) of the third setter 68. It is composed of a displacement converter 70 for converting the displacement into a line, and a display 72 for displaying the output of the displacement converter 70. In FIG. 3, 44 is a reflected light detection element. This is a lens for condensing the reflected light reflected by the lens 28.

The first setting device 50 and the second setting device 52 each have
Reference photodetection element 24 inputted via the amplifier 46
a capacitor 50 for holding the output or the maximum value of the reflected light detection element 28 output input via the amplifier 48;
A or 52A and the voltage held by the capacitor 50A or 52A, for example, is divided into 1/2 to obtain the first threshold value Vr.
ef+ or second threshold 1! It is comprised of a variable voltage dividing resistor 50B or 52B that generates V + ·er 2.

Further, the first detector 54 and the second detector 56 each have the output of the reference light detection element 24 inputted via the amplifier 46 or the reflected light detection element 28 manually inputted via the amplifier 4.8. A comparator 54A or 5 that compares the output with the first @1iaVref or the second threshold value /ref2.
6A and the comparator 54A or 56A as shown in FIG.
By differentiating the output rectangular wave signal Sp1.5l12, inverting one and taking the logical sum, or by delaying the rectangular wave signal @8p1, Sp2 by a minute time as shown in Fig. 5, the original By taking the exclusive OR with the reference signal 81 or the reflected signal S2, the pulses (No. 8 Pn and P1
2 or a digital differentiation circuit 5 that generates P21 and -F22.
It is composed of 4B or 56B.

FIG. 6 shows examples of signal waveforms at various parts in this embodiment. As is clear from the figure, for example, the rising edge P 1 of the reference signal S1
1 and the pulse pilA, which is calculated by counting the time interval of the rising edge P21 of the reflected signal 82, and the pulse number B, which is calculated by counting the time interval of the falling edge P12 of the reference signal S2 and the falling edge P22 of the reflected signal S2, and the pulse number B is calculated by 2. By doing so, the reference signal S1
The number of pulses corresponding to the midpoint of S2 and the midpoint of reflection A can be calculated with high precision.

In this embodiment, the first threshold 1! Vl・e[1st and 2nd
Since the threshold value Vref2 is varied depending on the maximum value of the reference signal S1 or the maximum value of the foul signal S2, the accuracy can be maintained regardless of fluctuations in the output signal due to scattered light, power fluctuations, etc. good measurements can be taken. Furthermore, it is also easy to aim for the midpoint in the case of an asymmetric waveform. Note that the voltage dividing ratio by the voltage dividing resistors 50B and 52B is 1/
2, but also the first riIAIlfWVref+
It is also possible to set the second threshold value vref2 to a constant voltage.

Further, in this embodiment, the number of clock pulses and the displacement i are compared by dividing the sum (A+B) of the count values of the first counter 62 and the second counter 64 by 2 as in the conventional case. , it is also possible to omit the operation of dividing by 2 by reducing the number of clock pulses to 1/2 of the conventional number.

In the embodiment IIIj, the time interval between the rising edge 1]1 of the reference signal S1 and the rising edge P2+ of the reflected signal S2, and the time interval between the falling edge P12 of the reference signal S1 and the reflected signal 82
Although the time interval of each falling P22 of
The time interval between the rising edge P ++ of the reference signal S1 and the falling edge P 22 of the anti-aJ signal S2 and the falling edge P 1 of the reference signal S1
Even if the calculation is performed by measuring the time interval between P21 and the rising edge P21 of the reflected signal S2, the result is the same.

Although this light is particularly suitable for use in an optical surface displacement detection device using a projection beam parallel scanning method as shown in the embodiments, the scope of application of the present invention is not limited thereto, and is applicable to the above-mentioned It is clear that the present invention can be similarly applied to optical surface displacement detection devices using a projection beam rotation scanning method as shown in Figure 1, optical surface displacement detection devices using other methods, and even general optical measuring instruments. be.

As explained above, 1. According to the present invention, the excellent effect is that the time interval corresponding to the midpoint between the reference signal and the foul signal can be finely adjusted with a simple circuit without directly finding the midpoint between the reference signal and the foul signal. has.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an example of an optical surface displacement detection device using a conventional projection beam rotation scanning method, and FIG. 2 is an optical surface displacement detection device using a projection beam parallel scanning method already proposed by the applicant. FIG. 3 is a block diagram showing the structure of an optical surface displacement detection device in which an embodiment of the optical representative displacement detection circuit according to the present invention is adopted; FIG. FIG. 4 is a diagram showing an example of the operation of the digital differentiation circuit used in the above embodiment;
The figure is a diagram showing another example of the operation of the digital differential circuit, and FIG. 6 shows the waveforms of each part of the above embodiment.
It is a diagram. DESCRIPTION OF SYMBOLS 10... Measurement target surface, 20... Laser beam light generator, 22... Rotating mirror, 24... Reference light detection element, 26... Slit, 28... Foul light detection element,
50.52... Setting device, 50A, 52A... Capacitor, 50B, 52B... Voltage dividing resistor, 54.56... Detector, 54A, 56A... Comparator, 54[3,56B ...Digital differentiation circuit, 58...
Shift register, 60...Clock pulse generator, 62.64...Counter, 66... Arithmetic unit, Sl.
...Reference signal, Sl...Reflected signal, V rer +
, V rer 2-threshold, P ++, P 12, P2
1. P2.2...Cross position, A, B...Clock pulse number. Agent Takaya Ron (and 1 other person) Figure 1 Figure 2 Figure 4 Figure 5 6 Figure 2'

Claims (1)

[Claims] 1) The reference signal output from the reference light detection element arranged corresponding to the M* position in the beam scanning range and the beam irradiation direction among the beam reflection light due to the measurement target surface. An optical surface displacement detection circuit that calculates the displacement of a surface to be measured in a set direction from the generation time interval of reflection signals output from a reflected light detection element configured to receive only reflected light in a set direction different from the set direction. a first setter that generates a first threshold that intersects the reference signal at two positions; a second setter that generates a second threshold that intersects the reflected signal at two positions; and a second setter that generates a second threshold that intersects the reflected signal at two positions; a first detector that detects two intersection positions between the signal and the first threshold; a second detector that detects two intersection positions between the reflected signal and the second threshold; a first counter that counts clock pulses that occur between a pair of associated intersection positions; and a first counter that counts clock pulses that occur between another pair of associated intersection positions that are detected by each detector. An optical surface displacement detection circuit comprising: 2 counters; and an arithmetic unit that calculates the generation time interval of the reference No. 55 and the reflected signal by calculating both pulse numbers counted by both counters. . (2) the first setter and the second setter hold the maximum value of the reference light detection element output or the reflected light detection element output;
2. The optical surface displacement detection circuit according to claim 1, wherein the first threshold value or the second threshold value is generated by dividing the holding signal. (3) The first detector and the second detector include a comparator that compares the reference signal or reflected signal with a first threshold value or a second intermediate value, and digitally processes a rectangular wave signal output from the comparator. 2. The optical surface displacement detection circuit according to claim 1, further comprising a digital differentiation circuit that generates pulse signals corresponding to two intersection positions.