JPH0378561B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an edge detection device in an optical measuring instrument for measuring the dimensions, displacement, etc. of an object, and in particular, it irradiates a non-transparent measurement object with a direct beam of light, and the transmitted light or reflected light generated thereby. ,
Alternatively, an optical method is used to make a photoelectric element receive the projected image of the object to be measured using transmitted light or reflected light, extract an electrical signal, and measure the dimensions, position, shape, etc. of the object based on this signal. This invention relates to an edge detection device in a measuring instrument.

[Conventional technology]

Conventionally, this type of optical measuring instrument, for example, a projector, irradiates an object to be measured on a stage with parallel light beams and projects a projected image of the object on a screen based on the transmitted or reflected light. This method uses the formed image to measure the dimensions and shape of the object to be measured, but the edges of the image of the object to be measured that are projected onto the screen generally have so-called smudges, and therefore , move the object to be measured on the stage,
It is difficult to accurately read measurement values from the coincidence of the image formed on the screen and the hairline. In order to solve this problem and other problems, the present applicant has proposed, in Japanese Patent Application No. 59-249278, as shown in FIG. In an edge detection device in an optical measuring instrument for visually measuring the dimensions of an object to be measured, the moving surface and It includes two light receiving elements 12A, 12B arranged concentrically in substantially parallel planes, and the level of the sensor output signal at the sensor output terminals 14A, 14B based on the outputs of both the light receiving elements 12A, 12B is A sensor 12 formed to have an equal value in each of brightness and darkness that occurs during movement, and a difference calculator connected to the sensor output terminals 14A and 14B of this sensor 12 to calculate the difference between the phase shift signals. 16, compares the differential output signal of the difference calculator 16 with high and low level reference signals, and forms a hold signal when the differential output signal is between the high and low levels, and One sensor signal among the output signals is held, and if the output signal exists between the held high-level hold signal and the low-level hold signal, the identification including the cross point of the phase shift signal with the reference level signal is determined. A region signal generator 18 outputs a signal in the region, and while the region signal generator 18 is outputting a signal, a cross between the differential output signal of the difference calculator 16 and a preset reference level signal is generated. We have proposed a sensor equipped with a detection means 20 that outputs a signal. Here, the sensor 12 includes the light receiving element 1
In addition to 2A and 12B, it is provided with current-voltage converters 12C and 12D for voltage-exchanging the outputs of the light-receiving element 12A and the light-receiving element 12B, and amplifiers 12E and 12F for amplifying these output voltages. The area signal generator 18 is connected to the difference calculator 16.
A first comparator 24A compares the differential output signal with a high level reference signal and outputs a hold signal when the differential output signal is lower than the high level; a second comparator 24B that outputs a hold signal when the dynamic output signal is higher than a low level; and a second comparator 24B that outputs a hold signal when the dynamic output signal is higher than a low level; first and second sample and hold circuits 2 that hold one sensor output signal a and sample the sensor output signal a when no hold signal is input;
6A, 26B, and a third sample and hold circuit that compares the output signals of these first and second sample hold circuits 26A and 26B with the sensor output signal a, and outputs a signal when the output signal is smaller than the sensor output signal a.
a fourth comparator 28B that compares the output signal with the sensor output signal a and outputs a signal when the output signal is larger than the sensor output signal a; comparator 28A,
an exclusive OR gate 30 that generates a region signal when only one of the gates 28B outputs a signal;
It is formed with The detection means 20 also includes a comparator 32 that compares the output signal of the difference calculator 16 with a reference level signal and outputs a signal when the two match, that is, at a cross point; Edge detection is performed only when a pulse signal generator 34 generates an edge pulse signal based on the signal output from the pulse signal generator 34, and a signal is output from both this pulse signal generator 34 and the area signal generator 18. It includes an AND gate 36 that outputs a signal. The output signal from this AND gate 36 is adapted to output an edge detection signal to a counter 40 of a displacement detection device 38 interlocked with the stage 3 for the object 4 to be measured. This displacement detection device 38 is composed of an encoder 42 that is linked to the document table 3 and generates a pulse signal according to the amount of movement thereof, and the counter 40 that reads the pulse signal output from the encoder 42. There is. This counter 40 is configured to output its read value to a storage device 44 when an edge detection signal is input from the AND gate 36. The sensor output signals when the sensor 12 approaches the projected image 4A of the measurement object formed on the screen 6 and passes through the edge of the projected image 4A are shown in FIG. 5A by symbols a and b. As shown, the result is a phase-shifted signal with equal amplitude. As shown in FIG. 5B, these output signals are calculated by the difference calculator 16 so that c=ba-a and are output. Output signal a from the sensor output signal 14A
are input to the first and second comparators 24A and 24B of the area signal generator 18, respectively. As shown in FIG. 5C, the first comparator 24A compares the reference voltage Vref+ and the input signal c, and when the signal c is greater than Vref+, the first comparator 24A transfers the sampling signal d to the first sample hold circuit. Output to 26A. Further, as shown in FIG. 5D, the second comparator 24B compares the input signal c with the reference voltage Vref-, and determines whether the signal c is
When it is smaller than Vref-, the sampling signal e is output to the second sample and hold circuit 26B. The first and second sample and hold circuits 26
A, 26B samples the sensor output signal a when the first comparator 24A outputs the sampling signal d and when the second comparator 24B outputs the sampling signal e, and also samples these sampling signals. When d and e are not output, the signal values at the final sampling time are held. Therefore, these sample and hold circuits 26A,
26B outputs a high hold signal f and a low hold signal g to the third comparator 28A and the fourth comparator 28B, respectively, as shown by the broken line and the dashed line in FIG. 5E. These third comparator 28A and fourth comparator 2
8B indicates the input high hold signal f and low hold signal g as shown in FIG. 5F and G.
is compared with the sensor output signal a, and when these high hold signal f and low hold signal g are larger than the sensor output signal a, signals h and i are outputted to the exclusive OR gate 30, respectively. This exclusive OR gate 30 is the third
When a signal is output from only one of the comparator 28A and the fourth comparator 28B, a digital signal j of "1" is output as shown in FIG. 5H. On the other hand, the differential output signal c output by the difference calculator 16 is input to the comparator 32 of the detection means 20, and this comparator 32 receives the differential output signal c as shown in FIG. When c crosses the reference level signal of 0, a digital signal k of "1" is output. Based on the output of comparator 32, pulse signal generator 34 generates a pulse signal l as shown in FIG. 5J.
is output to the AND gate 36. Pulse signal l from the pulse signal generator 34
and the digital signal j from the exclusive OR gate 30 are input to an AND gate 36, which when both input signals are "1", as shown in FIG. 5K, for example, 10μsec
A pulse signal m is outputted, and at this point, an edge of the projected image 4A is detected. The edge detection device in the above Japanese Patent Application No. 59-249278 can be used even when the object to be measured is made of a material that cannot completely block light, such as a translucent glass product. Even if the difference between the dark and bright areas is small and it is not possible to obtain a signal above a predetermined level, edges of the object to be measured can be detected.

[Problems to be solved by the invention]

However, in the edge detection device of the above-mentioned patent application No. 59-249278, in order to improve the efficiency of measurement work, edges are detected when the sensor 12 is moved at a high speed higher than a certain speed with respect to the projected image. The problem is that there are cases where it is not possible to do so. That is, when the sensor 12 is moved at high speed relative to the projected image 4A, the waveform c in FIG. 4B becomes
It shrinks in the time axis direction, but on the other hand, the first
Due to the time delay of the comparator 24, the rise and fall of the signal d are delayed as shown in FIG. 4C,
Furthermore, a sample hold circuit 2 corresponding to this
This is because, in addition to the time delay of 6A, the high hold start point of the signal f shown in FIG. 4E is delayed from the position of the cross point, that is, the edge.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and is an optical measuring instrument that is capable of reliably detecting an edge even if there is a time delay in the output signal of the first comparator. An object of the present invention is to provide an edge detection device.

[Means to solve the problem]

The present invention relates to an edge detection device in an optical measuring instrument for directly or indirectly measuring the dimensions of a measurement object by detecting transmitted light or reflected light. It includes a plurality of light-receiving elements arranged in a plane substantially parallel to the moving surface to generate a phase shift signal based on brightness and darkness, and the level of the sensor output signal at the sensor output terminal based on the output of these light-receiving elements is a sensor formed to have an equal value in each of brightness and darkness that occurs during the relative movement; a difference calculator connected to the sensor output terminal of this sensor to calculate the difference between the phase shift signals; Compare the differential output signal of the difference calculator with reference signals of high and low levels, form a hold signal when the differential output signal is between the high and low levels, and select one of the sensor output signals. holds the sensor signal, and when the output signal exists between the held high-level hold signal and the low-level hold signal, a signal is output in a specific area including the cross point of the phase shift signal with the reference level signal. a detection means for outputting a cross signal between the differential output signal of the difference calculator and a preset reference level signal while the signal is being output from the area signal generator; The region signal generator has a falling edge of a one-shot pulse that is output when the differential output signal becomes higher than the reference signal at the higher level, and when the differential output signal becomes higher than the reference signal at the lower level. The above object is achieved by outputting the hold signal using the falling edge of the one-shot pulse, which is output when the signal becomes lower than the reference signal, as a starting point. Further, the present invention includes a region signal generator that compares the differential output signal of the difference calculator with a high-level reference signal, and outputs a high-level signal when the differential output signal is higher than the high-level level. a second comparator that compares the differential output signal with a low level reference signal and outputs a low level signal when the differential output signal is lower than the low level; a first pulse that generates a one-shot pulse when the high-level and low-level signals are input;
and a second one-shot pulse generator, which holds the sensor output signal of one of the sensors and generates the sensor output signal when the one-shot pulse from the first and second one-shot pulse generators is input. The output signals of the first and second sample and hold circuits are compared with the sensor output signal, and when the output signal is smaller than the sensor output signal, the signal is detected. a third comparator that outputs an output; a fourth comparator that compares the output signal and the sensor output signal and outputs a signal when the output signal is larger than the sensor output signal; The above object is achieved by comprising an exclusive OR gate that generates a region signal when only one of the comparators outputs a signal.

[Effect]

In this invention, the sample and hold circuit in the area signal generator is activated by the pulse signal output from the one-shot pulse generator at the rising edge of the output signal of the first comparator, so that it can sample and hold the sensor output signal. The start time does not lag behind the cross point. Therefore, even if the sensor is moved at high speed, the edge of the object to be measured can be reliably detected.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, the same parts as those of the edge detection device in Japanese Patent Application No. 59-249278 shown in FIGS. 4 and 5 are given the same reference numerals. In this embodiment, the present invention is applied to a projector, and as shown in FIGS. 1 to 3,
The light from the light source lamp 1 is irradiated onto the measuring object 4 on the stage 3 from below the stage 3 through the condenser lens 2 or from above the stage 3 through another optical path. Based on the transmitted light or reflected light, a projected image of the object to be measured 4 is formed on the screen 6 via the projection lens 5, and this projected image can be used to indirectly measure the dimensions of the object to be measured 4, etc. In the edge detection device in the projector 10 for performing the measurement, the edge detection device is arranged concentrically in a plane substantially parallel to the movement plane so as to generate a phase shift signal based on the brightness and darkness that occurs when moving relative to the measurement object 4. Both light receiving elements 14 include two light receiving elements 12A and 12B.
The sensor 12 is formed so that the level of the sensor output signal at the sensor output terminals 14A and 14B based on the outputs of the sensors A and 12B is equal to each other in brightness and darkness that occur during the relative movement. The sensor output terminal 14 in the sensor 12
A difference calculator 16 is connected to A and 14B and calculates the difference between the phase shift signals, and compares the differential output signal of the difference calculator 16 with high-level and low-level reference signals, and calculates the differential output. forming a hold signal to hold one sensor signal among the sensor output signals when the signal is between a high level and a low level, and the output signal is between the held high level hold signal and the low level hold signal; A region signal generator 18 outputs a signal in a specific region including the cross point of the phase-shifted signal with the reference level signal, and while the region signal generator 18 outputs a signal, A detection means 20 is provided for outputting a cross signal between the differential output signal of the arithmetic unit 16 and a preset reference level signal. As shown in FIG. 1, the sensor 12 is provided integrally with a transparent plate 22 that is slidably placed on the upper surface of the screen 6 of the projector 10 in parallel thereto. It is also movable. Light receiving element 12B that constitutes the sensor 12
is formed to have a circular cross section, and the light receiving element 12A
is formed in a ring shape concentrically with the light receiving element 12A at intervals in the radial direction around the light receiving element 12A. Here, the sensor 12 includes the light receiving element 1
In addition to 2A and 12B, it is provided with current-voltage converters 12C and 12D for voltage-exchanging the outputs of the light-receiving element 12A and the light-receiving element 12B, and amplifiers 12E and 12F for amplifying these output voltages. These amplifiers 12E and 12F are completely dark,
The offset is adjusted to cancel the dark voltage of the light receiving elements 12A, 12B, and the gain is adjusted so that the outputs at the sensor output terminals 14A, 14B are at the same level in full brightness. The area signal generator 18 is connected to the difference calculator 16.
A first comparator 24A compares the differential output signal of the differential output signal with a high level reference signal and outputs a high level signal when the differential output signal is higher than the high level; a second comparator 24B that outputs a low level signal when the differential output signal is lower than the low level; First and second one shot pulse generators 25 that generate shot pulses
A, 25B, and the sensor output signal a of one of the sensors 12 is held, and when the pulse signals from the first and second one-shot pulse generators 25A and 25B are input, the sensor output signal a is The output signals of the first and second sample and hold circuits 26A and 26B are compared with the sensor output signal a, and the output signal is determined as the sensor output. a third comparator 28A that outputs a signal when it is smaller than the sensor output signal a; and a fourth comparator 28A that compares the output signal with the sensor output signal a and outputs a signal when the output signal is larger than the sensor output signal a. an exclusive OR that generates a region signal when only one of the third and fourth comparators 28A and 28B outputs a signal.
A gate 30 is formed. The detection means 20 also includes a comparator 32 that compares the output signal of the difference calculator 16 with a reference level signal and outputs a signal when the two match, that is, at a cross point; Edge detection is performed only when a pulse signal generator 34 generates an edge pulse signal based on the signal output from the pulse signal generator 34, and a signal is output from both this pulse signal generator 34 and the area signal generator 18. It includes an AND gate 36 that outputs a signal. The output signal from this AND gate 36 is adapted to output an edge detection signal to a counter 40 of a displacement detection device 38 interlocked with the stage 3. This displacement detection device 38 is composed of an encoder 42 that is linked to the document table 3 and generates a pulse signal according to the amount of movement thereof, and the counter 40 that reads the pulse signal output from the encoder 42. There is. This counter 40 is configured to output its read value to a storage device 44 when an edge detection signal is input from the AND gate 36. Next, the operation of the above embodiment will be explained. The projected image 4A of the measurement object 4 formed on the screen 6 is moved in one direction relative to the sensor 12 so that the edge of the projected image 4A crosses the sensor 12. When the projected image 4A approaches and passes through the sensor 12, it is obtained by the light receiving elements 12A and 12B, and is adjusted by the amplifiers 12E and 12F via the current-voltage converters 12C and 12D. , the output signals generated from the sensor output terminals 14A and 14B are indicated by symbols a and b in FIG. 3A.
As shown by , the result is a phase-shifted signal with equal amplitude. As shown in FIG. 3B, these output signals are calculated by the difference calculator 16 so that c=ba-a and are output. Output signal a from the sensor output terminal 14A
are input to the first and second comparators 24A and 24B of the area signal generator 18, respectively. As shown in FIG. 3C, the first comparator 24A compares the reference voltage Vref+ and the input signal c, and when the signal c is greater than Vref+, the first comparator 24A outputs a high level signal d to the first one shot. Output to pulse generator 25A. Further, as shown in FIG. 3D, the second comparator 24B compares the input signal c and the reference voltage Vref-, and determines whether the signal c is
When it is smaller than Vref-, the low level signal e is
output to the one-shot pulse generator 25B.
Note that the first and second comparators 24A and 24B
is provided with hysteresis characteristics as shown in FIGS. 3C and 3D to prevent chattering. When the first one-shot pulse generator 25A receives the high-level signal d, the first one-shot pulse generator 25A outputs 1 at that point.
The first sample and hold circuit 26
Output to A. Also, a second one-shot pulse generator 25B
outputs one pulse e' to the second sample and hold circuit 26B when the low level signal e is input. The first and second sample and hold circuits 26
A and 26B sample the sensor output signal a while the pulse signal d' and the pulse signal e' are input, and when the pulse signals d' and e' are not output, they respectively sample the final sampling signal. The signal value at that point in time is held.
That is, the signal values at the falling edges of the pulse signals d' and e' are held. Therefore, these sample and hold circuits 26A,
26B is configured to output a high hold signal f and a low hold signal g to the third comparator 28A and the fourth comparator 28B, respectively, as shown by the broken line and the dashed line in FIGS. 3G and 3H. There is. These third comparator 28A and fourth comparator 2
8B indicates the input high hold signal f and low hold signal g as shown in FIG. 3G and H.
is compared with the sensor output signal a, and when these high hold signal f and low hold signal g are larger than the sensor output signal a, the signal h is
and i to the exclusive OR gate 30. This exclusive sieve OR gate 30 is the third
When a signal is output from only one of the comparator 28A and the fourth comparator 28B, a digital signal j of "1" is output as shown in FIGS. 3K and 4. On the other hand, the differential output signal c output by the difference calculator 16 is input to the comparator 32 of the detection means 20, and this comparator 32 receives the differential output signal c as shown in FIG. 3L. When c crosses the reference level signal of 0, a digital signal k of "1" is output. Based on the output of comparator 32, pulse signal generator 34 generates a pulse signal l as shown in FIG.
is output to the AND gate 36. Pulse signal 1 from the pulse signal generator 34
and the digital signal j from the exclusive OR gate 30 are input to the AND gate 36, which when both input signals are "1", as shown in FIG. 3N, e.g. ,
A pulse signal m of 10 μsec is output, and at this point, the edges of the projected image 4A are detected. The edge signal m, which is a pulse, is transmitted to the displacement detection device 3.
8 and is input to the counter 40 at counter 4.
0 outputs the read value at the time when this edge signal m is input to the storage device 44, and detects the position of the edge of the measuring object 4 on the stage 3. The signals stored in the storage device 44 will be output to another computing device, printed out, or displayed on a display. In the above embodiment, the projected image 4 of the sensor 12
When the relative moving speed with respect to A is increased, the waveform of the differential output signal c in FIG. 3B shrinks in the time axis direction. In this case, the first and second comparators 24A, 24
Since there is a time delay in the output signal of
The falling point of the output signal d of the comparator 24A may be behind the cross point of the differential output signal c, that is, the position of the edge of the object to be measured. However, the starting point of signal hold in the sample and hold circuit 26A is based on the rising edge of the output signal d of the first comparator 24A, and one pulse signal d' output from the first one-shot pulse generator 25A. Since the hold start point in the sample-and-hold circuit 26A does not lag behind the cross point, that is, the edge position of the object to be measured. Therefore, even if the relative movement speed between the sensor 12 and the projected image 4A of the measurement object 4 is made high, the edge of the measurement object 4 can be reliably detected. Here, in the above embodiment, the measurement object 4
However, in the case of a material that cannot completely block light, such as a translucent glass product, Figure 3A and Figure 5A
As shown in the following, the sensor output signals a and b in the dark area are 0 when the sensor output signal is set to "1" in bright light and "0" in complete darkness.
The value is larger than 1 and close to 1. In this case, when these sensor output signals a or b compare themselves with the reference voltage Vref-, the reference voltage Vref-
It may not be possible to obtain the intersection point with Vref-, and therefore it may not be possible to obtain the area signal. In this embodiment, the region signal is converted to the difference calculator 1.
6 differential output signals, that is, c=a−b, even if the object 4 to be measured is a translucent material, the area signal can be reliably obtained. Furthermore, in this embodiment, the light receiving elements 12A and 12B constituting the sensor 12 are formed in a concentric circle shape, and the output levels of the signals generated by these elements at the sensor output terminals 14A and 14B are made equal. , light receiving elements 14A and 14B
Since the moving direction does not coincide with the boundary line of There is no restriction on the direction of movement, and edge detection can be performed with high precision. Further, as described above, since the light receiving elements 12A and 12B constituting the sensor 12 are configured in a concentric circle, the area of the light receiving surfaces of the light receiving elements 12A and 12B facing the object to be measured can be reduced.
Therefore, it is not only possible to apply the present invention to small-sized measuring instruments, but also to simplify the supporting means thereof, and to increase the effective viewing range of the screen in a projector. Furthermore, since the sensor 12 is small, it can also be applied to edge detection of a complexly shaped object. In the above embodiment, the light receiving element 12A is formed in a circular shape, and the light receiving element 12B is formed in a concentric ring shape surrounding the circular light receiving element 12A at intervals, but the present invention is not limited to this. Not a thing,
It is sufficient that the sensor includes a plurality of light receiving elements and can obtain a phase shift signal. Therefore, for example, a ring-shaped light-receiving element may be arranged without providing a radial interval from the inner circular light-receiving element, or two light-receiving elements may be arranged in a concentric ring-shaped light-receiving element. It may be configured from the following. Further, for example, four light receiving elements may be arranged in a block shape. Further, in the embodiment, the light receiving elements 12A, 1
2B, the sensor output terminals 14A and 14B are made equal by making the light receiving area equal, but this is different from the sensor output terminal 1.
It is sufficient that the output signals at 4A and 14B are at the same level, and therefore the light receiving elements 12A,
12B and the sensor output terminals 14A, 14B, or the output levels of both the sensor output terminals 14A, 14B may be made equal without providing an amplifier. Further, in the above embodiment, the projection image 4A is moved relative to the sensor 12 by moving the stage 3, but this may be done by moving the sensor 12 relative to the projection image 4A. . Further, although the above embodiment is for measuring the edge of a projected image on a screen of a projector, the present invention is not limited to this, and the present invention is not limited to this, but can be performed by detecting transmitted light or reflected light, It is generally applied to an edge detection device in an optical measuring instrument for directly or indirectly measuring the dimensions of an object to be measured. Therefore, for example, from the relative movement of the main scale and index scale that form an optical grating, the object to be measured can be scanned in parallel using a photoelectric length measuring device for photoelectrically measuring dimensions, etc., or a laser beam, etc. The present invention is also applied to an edge detection device in a measuring instrument, etc., which measures the dimensions of the object to be measured from its bright and dark areas.

【Effect of the invention】

Since the present invention is configured as described above, in an edge detection device in an optical measuring instrument using a light receiving element, even if the relative movement speed of the sensor with respect to the object to be measured is increased, the accuracy is not affected by this. This has an excellent effect of being able to reliably detect high edges.

[Brief explanation of drawings]

Fig. 1 is an optical system diagram showing an embodiment in which the edge detection device in the optical measuring instrument according to the present invention is implemented in a projector, Fig. 2 is a block diagram showing the configuration of the embodiment, and Fig. 3 is FIG. 4 is a diagram showing the process of signal processing in the same embodiment. FIG. 4 is a block diagram showing the edge detection device in the earlier application filed by the present applicant. FIG. 5 is a diagram showing the process of signal processing in the edge detection device. be. 4...Measurement object, 4A...Projected image, 12...
...sensor, 12A, 12B...light receiving element, 16
...Difference calculator, 18... Area signal generator, 20...
...Detection means, 24A...First comparator, 24B...
...Second comparator, 25A...First one shot pulse generator, 25B...Second one shot pulse generator, 26A...First sample hold circuit, 26B...Second sample hold circuit ,
28A...Third comparator, 28B...Fourth comparator, 30...Exclusive OR gate, 32
...Comparator, 34...Pulse signal generator, 36...
...AND gate.

Claims (1)

[Scope of Claims] 1. In an edge detection device in an optical measuring instrument for directly or indirectly measuring the dimensions of an object to be measured by detecting transmitted light or reflected light, It includes a plurality of light-receiving elements arranged in a plane substantially parallel to the moving surface to generate a phase shift signal based on the brightness and darkness that occurs during movement, and a sensor output signal based on the output of these light-receiving elements is transmitted to the sensor output terminal. A sensor formed so that the level is equal to the brightness and darkness that occur during the relative movement, and a difference calculator connected to the sensor output terminal of this sensor and calculating the difference between the phase shift signals. and compares the differential output signal of the difference calculator with reference signals of high and low levels, and forms a hold signal when the differential output signal is between the high and low levels, and controls the sensor output signal. One of the sensor signals is held, and if the output signal exists between the held high-level hold signal and the low-level hold signal, it is possible to detect a specific area including the cross point of the phase shift signal with the reference level signal. A region signal generator that outputs a signal, and a detection device that outputs a cross signal between the differential output signal of the difference calculator and a preset reference level signal while the signal is output from the region signal generator. and a falling edge of a one-shot pulse that is output when the differential output signal becomes higher than the high-level reference signal; An edge detection device for an optical measuring instrument, wherein the hold signal is output with the falling edge of a one-shot pulse outputted when the level becomes lower than the low-level reference signal as a starting point. 2. The area signal generator includes a first comparator that compares the differential output signal of the difference calculator and a high level reference signal, and outputs a high level signal when the differential output signal is higher than the high level. , a second comparator that compares the differential output signal with a low level reference signal and outputs a low level signal when the differential output signal is lower than the low level; When a level signal is input, first and second one-shot pulse generators each generate a one-shot pulse, and one sensor output signal of the sensor is held, and the first and second one-shot pulse generators each generate a one-shot pulse. first and second sample-and-hold circuits that sample the sensor output signal when a one-shot pulse from the pulse generator is input; and output signals of the first and second sample-and-hold circuits and the sensor output signal. a third comparator that compares the output signal with the sensor output signal and outputs a signal when the output signal is larger than the sensor output signal; and a third comparator that compares the output signal with the sensor output signal and outputs a signal when the output signal is larger than the sensor output signal. Claim 1, comprising: a fourth comparator that outputs a signal; and an exclusive OR gate that generates a region signal when only one of the third and fourth comparators outputs a signal. An edge detection device in the optical measuring instrument described in 2.