JPS59226802A - Edge detector of optical measuring equipment - Google Patents

Abstract

PURPOSE:To detect an edge with high precision without any influence of variation in the quantity of laser light, etc., by composing a photodetector of two photodetecting elements divided in the direction where an image of a body to be measured travels, and calculating the difference between the output signals of both elements. CONSTITUTION:The photodetector 26 consists of the two photodetecting elements 26A and 26B divided in the direction where the image 24A of the body 24 to be measured travels. When a scanning laser beam reaches an edge part, part of a spot 20A is cut off. The output signals of the photodetecting elements 26A and 26B are differentiated by differentiation circuits 46A and 46B, and a differential circuit 48 calculates their difference. The cross point 54 of the signal waveform 48A at this time and a reference voltage from a reference voltage generator 52 is calculated and a pulse signal 56 is outputted at this time to detect the edge of the body 24 to be measured. Consequently, the edge is detected with high precision without any influence of variation in the quantity of laser light.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a one-point detection device in an optical measuring instrument that measures the dimensions of an object to be measured using a parallel scanning light beam.

Conventionally, a rotating scanning light beam (laser beam) is converted into a parallel scanning light beam passing between the collimator lens and a condensing lens by a collimator lens, and an object to be measured is placed between the collimator lens and the condensing lens. There has been an optical measuring instrument that measures the dimensions of an object to be measured based on the length of time of a dark or bright area that occurs when the parallel scanning light beam is interrupted by the object.

For example, as shown in FIG. 1, a laser beam 12f is oscillated from a laser tube 10 toward a fixed mirror 14, and the laser beam 12 reflected by the fixed mirror 14 is converted into a scanning beam 17 by a rotating mirror 16. This scanning beam 17 is converted into a parallel scanning light beam 20 by a collimator lens 18, and this parallel scanning light beam 20 is converted into a parallel scanning light beam 20.
The object to be measured 24 placed between the remetering lens 18 and the condensing lens 22 is scanned at high speed.
1 method (in the scanning direction (Y direction) of the object to be measured 24) is measured from the length of time of the dark or bright portion of the image produced by the method. That is, the brightness or darkness of the parallel scanning light beam 20 is detected as a change in the output voltage of the light receiver 26 located at the focal point 1η of the condensing lens 22, and the signal from the light receiver 26 is input to the preamplifier 28. After being amplified here, it is sent to the ceramic 1 to selection circuit 30. This segment I-selection circuit 30 generates a voltage V for opening the gate circuit 32 only during the time t during which the object under test 24 is scanned from the output voltage of the photoreceiver 26, and outputs it to the gate circuit 32. It is made to be. This gate circuit 32 includes
Since the tarock pulse CP is inputted from the clock pulse oscillator 34, the clock pulse P corresponding to the time t corresponding to the scanning direction dimension (for example, outer diameter) of the object 24 to be measured can be inputted to the counting circuit 36 from the gate circuit. The counting circuit 36 counts the clock pulses P and outputs a counting signal to the digital display 38, and the digital display 38 digitally displays the dimension in the scanning direction, that is, the outer diameter of the object 24 to be measured. On the other hand, the rotating mirror 16 is driven by the clock pulse oscillator 34 by a synchronous motor 44 that is driven synchronously by the output of a power amplifier 42 and a synchronous sine wave oscillator 40 that generates a sine wave in synchronization with the output of the clock pulse oscillator 34. It is rotated in synchronization with the output clock pulse CP to maintain measurement accuracy.

Such high-speed scanning laser length measuring machines are becoming widely used because they can measure the length, thickness, etc. of moving objects and high-temperature objects with high precision in a non-contact manner.

However, the diameter of the laser beam 12 in the above-mentioned high-speed scanning laser length measurement is 0.8 to 11 m.
If left as is, a measurement error of up to 111111 may occur.

Therefore, conventionally, for example, the boundary (edge) of the object to be measured 24
In order to reduce the diameter of the laser beam in the vicinity, measurement methods have been taken using a lens that focuses on the edge portion, but even in this case, the laser beam 1
It is difficult to reduce the diameter of 2 to 0.08++o++ or less, and therefore, the measurement error due to the diameter of the laser beam will occur at a maximum of o, os mm.

On the other hand, if the edge of the object to be measured is detected by the cross point of the output signal from the photoreceiver 26 and the reference voltage, the measurement error can be reduced to about 1 μm at maximum. Due to changes in the light intensity of the laser beam 12 due to changes in the reflectance of the laser beam 24, changes in the distance from the remeter lens 18 to the object to be measured 24, etc.
There is a problem that the measurement error fluctuates.

There is also a method that detects edges by second-order differentiating the output No. 15 of the light-receiving element, obtaining a waveform signal, and comparing this with a reference voltage. The position of the detected edge may differ depending on its size, and furthermore, as mentioned above, due to fluctuations in the light intensity of the laser beam 12, an apparent edge may be detected at a location other than the edge. be.

The present invention has been made in view of the above-mentioned problems, and is capable of measuring the object to be measured with high precision and high speed scanning without being affected by changes in the light intensity of the laser beam or changes in the distance from the collimator lens to the object to be measured. It is an object of the present invention to provide an edge detection device for an optical measuring instrument capable of detecting the edges of an object.

This invention scans the object to be measured relatively in one direction and in parallel with a light beam, receives the light beam after scanning by a light receiver, and detects the object to be measured based on the output signal of the light receiver. An edge detection device for an optical measuring instrument that detects the length of time of a dark or bright area due to an image caused by a part of a light beam being blocked by an object to be measured in a scanning direction. The light receiver is formed of two light receiving elements divided into two in the direction in which the image of the object to be measured travels, and a differentiating circuit for differentiating the output signals of these light receiving elements, respectively, and a differentiating circuit for differentiating the output signals of these light receiving elements, respectively; By providing a differential circuit that calculates the difference between output signals, and a determination circuit that compares the output 1g from this differential circuit with a reference signal and determines one point that is an edge of the object to be measured, the above-mentioned problem can be achieved. It accomplishes its purpose.

The present invention also provides a method for disposing a portion of the two light receiving elements so as to be perpendicular to the direction in which the image of the object to be measured crosses a reference line that is a boundary between the two light receiving elements. This aims to achieve the above objectives.

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

Here, in this embodiment, the same or corresponding parts as those of the conventional optical measuring device shown in FIG. 1 will be designated by the same reference numerals as in FIG. 1, and the explanation thereof will be omitted.

This embodiment, as shown in FIGS. 2 and 3,
In the optical measuring device similar to that shown in FIG.
Differentiating circuits 46A and 46B are formed from two divided light receiving elements 26A and 26B and differentiating the output signals of these light receiving elements 26A and 26B, respectively, and the difference between the output signals of these differentiating circuits 46A and 46B is calculated. An edge detection device 51 is configured by providing a differential circuit 48 and a determination circuit 50 that compares the output signal from the differential circuit 48 with a reference signal to determine one point that is an edge of the object to be measured 24. This is what I did.

As shown in FIG. 3, the light-receiving plane shape of the light receiver 26 is a quadrangular shape consisting of two rectangles separated by a boundary line 26C perpendicular to the traveling direction of the image of the object to be measured 24, Each rectangle is a light receiving element 26A, 26B.
are composed of each.

Symbols 28A and 28B in FIG. 2 are light receiving elements 26A and 26B.
The differential circuit 4 of the edge detection device 51 amplifies the output signal of
Preamplifier that outputs to 6A and 46B.

52 indicates a reference voltage generator, and this reference voltage generator is:
li1] A reference voltage having a waveform indicated by the symbol 52A is output to the determination circuit 50, and the determination circuit 50 detects a cross point 54 between the signal of this reference voltage and No. 15 of the differential circuit 48. Then, the pulse signal 5 at that point
6 is output.

Next, the operation of the above embodiment will be explained.

First, in a state in which the parallel scanning light beam 2o is scanning a portion where there is no object to be measured 24, the parallel scanning light beam 2o
0 reaches and covers the light receiver 26 over the entire range of the beam diameter φ, as shown in FIG. 4(A).

In this state, the waveforms 27A and 27B of the output signals from the light receiving elements 26A and 26B are la
It becomes a flat waveform of l' 1 J.

When the parallel scanning light beam 20 approaches the edge portion of the object to be measured 24, as shown in FIGS. The resulting image 24A causes the output signal of each light-receiving element 26A to decrease from the value "1" to "0".

At this time, since the image 24A reaches the light-receiving surface of the light-receiving element 26B later than the light-receiving element 26A, the output signals of the light-receiving elements 26A and 26B also fall as shown in FIG. A time lag will occur between the waveforms 27A and 27B.

Output signal waveform 27A of these light receiving elements 26A, 26B,
27B are differentiated by differentiating circuits 46A and 146'B, respectively, to obtain signal waveforms 47A and 47B.

When the difference between the output signals of the differentiating circuits 46A and 46B is determined by the differential circuit 48A, an output signal shown by a signal waveform 48A is obtained.

The determination circuit 5 compares the output signal of the differential circuit 48 with the reference voltage from the reference voltage generator 52 shown by a waveform 52A.
0 to find the cross point 54, and this cross point 5
If the pulse 21g number 56 is output from the determination circuit 50 at a time of 4, this will indicate the position of the edge of the object to be measured 24.

Moreover, the image 24A of the object to be measured 24 moves relatively,
When the image reaching the light receiving elements 26A, 26B changes from dark to bright, the pulse signal 56 is output at the cross point 54 in the same way as described above, and this indicates the position of the other edge of the object to be measured 24. It turns out.

Therefore, from the time t between the two pulse signals @56 from one edge of the object to be measured 24 to the other edge, the first
The dimension of the object to be measured 24 in the scanning direction is detected by the same procedure as in the optical measuring device shown in the figure.

In this embodiment, for example, parallel scanning light beam 2
Even if there is a change in the light intensity of the parallel scanning light beam 20 in a state where the edge of the object to be measured 24 is not detected, this change in light intensity is captured by the light receiving elements 26A and 26B, and these changes are differentiated. When the light reaches the differential circuit 48 via the circuits 46A and 46B, the fluctuation in the amount of light is canceled out, so that pseudo edge detection does not occur.

Therefore, the edge detection function is performed only when the parallel scanning light beam 20 reaches the edge portion of the object 24 to be measured.

In the above embodiment, the light receiving elements 26A and 26B of the light receiver 26
is divided by a boundary line 26C in a direction perpendicular to the moving direction of the image 24A of the object to be measured; however, the present invention is not limited thereto; for example, as shown in FIG.
As shown in , the boundary line 26G may be inclined with respect to the advancing direction of the image 24A.

In this case, as shown in FIGS. 5(,B) to (D), the slope of the fall or rise of the output signal from bright to dark or from dark to bright in each of the light receiving elements 26A and 26B becomes large. Therefore, the detection range of the cross point 54 can be made narrower with respect to the time axis, that is, the edge position can be detected more precisely.

Further, in the embodiment shown in FIG. 5, the light receiving element 2-6
The boundary line 26C between the two light receiving elements 26A and 26B is arranged diagonally.
It is sufficient that the shadow @24A of the object to be measured 24 is disposed perpendicularly to the direction in which the shadow @24A moves and beyond the reference line that serves as the boundary between the two light receiving elements 26A and 26B.
Boundary #I26C does not have to be an inclined straight line.

Further, in the above embodiment, the object to be measured 24 is kept stationary and the parallel scanning light beam 20 is moved in the scanning direction, but the present invention is not limited to this. , it is sufficient that the light beam moves relative to the object to be measured in the scanning direction; therefore, the light beam side is fixed and the object to be measured is moved relative to it;
Alternatively, it is applicable to each object in which the object to be measured and the light beam move together.

Since the present invention is configured as described above, it is possible to accurately detect the edges of the object to be measured with a simple configuration. This has the excellent effect of being able to detect the edges of the object to be measured without being affected by this.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional optical measuring device, Figure 2 is a block diagram showing a conventional optical measuring device.
The figure is a block diagram showing an embodiment of an edge detection device in an optical measuring instrument according to the present invention, FIG. 3 is a block diagram showing an enlarged main part of the same embodiment, and FIGS. 4(A) and (B) ,(
C) is an explanatory diagram showing the relationship between the planar shape of the light receiver and the image in the same embodiment, and FIG. 5(A) is a plan view showing the planar shape of the light receiver in the second embodiment of the present invention. Figure (B) ~
(D) is a g-line diagram showing an output signal, a differentiated signal, and a differential signal in the light receiver of the second embodiment. 12. Laser beam, 18. Collimator lens, 20. ... Parallel scanning light beam, 22 ... Condenser lens, 24 ... Measured object, 24A ... Image, 26 ... Light receiver, 26A, 26B ... Light receiving element, 26C ... Boundary Lines, 46A, 46B... Differential circuit, 48... Differential circuit, 50... Judgment circuit, 51... Edge detection device, 52... Reference voltage generator, 54... Cross point. Agent: Keisuke Matsuyama (and 1 other person, Figure 4, Figure 5)

Claims (2)

[Claims] (1) The object to be measured is relatively scanned in one direction and in parallel with a light beam, the light beam after scanning is received by a light receiver, and the object to be measured is scanned based on the output No. 1z of the light receiver. The dimension of the object to be measured in the scanning direction is determined by detecting the length of time of a dark part or a bright part caused by a part of the light beam being blocked by the image. ii1'J The photoreceptor is formed from two light-receiving elements divided into two in the direction in which the image of the object to be measured advances, and a differentiation circuit for differentiating the output No. 15 of these light-receiving elements, respectively, and a differential circuit for differentiating the output No. 15 of these light-receiving elements, A differential circuit that calculates the difference between the output signals of the circuit and a determination circuit that compares the output signal from the differential circuit with a reference signal and determines one point that is an edge of the object to be measured is provided. An edge detection device in an optical measuring instrument characterized by: (2) Parts of the two light-receiving elements are arranged perpendicularly to the direction in which the image of the object to be measured moves and beyond a reference line that serves as a boundary between the two light-receiving elements. An edge detection device in an optical measuring instrument according to claim 1.