JPS61122505A - Edge detecting device of optical measuring instrument - Google Patents

Abstract

PURPOSE:To take and accurate measurement by irradiating an object of measurement with a scanning light directly, and photodetecting the resulting transmitted or reflected light or the projection image of the object by a photoelectric sensor. CONSTITUTION:When the projection image 4A of the object of measurement is passed through the photoelectric sensor 12, output signals (a) and (b) from sensor output terminals 13A and 13B are processed by difference arithmetic 38 to obtain a signal a-b, which are inputted to the 1st and the 2nd comparing circuits 20 and 22. Then, the circuits 20 and 2 generates output signals (c) and (d) when an input analog signal and the signal a-b vary from a high level to a low level and reset the signals (c) and (d) when they vary from the low level to the high level. An exclusive OR which inputs the signals (c) and (d) outputs a signal (e) to a pulse signal generator 34, which outputs a pulse signal (f) to an AND gate 32. The signal (a) from the sensor 12, on the other hand, is passed through an area signal generator 31 and a digital signal generator 30 a digital signal '1' to the gate 32. Then, the gate 32 detects the edge of the image 4A when the input signals are both '1'.

Description

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

The present invention relates to an edge detection device for an optical measuring instrument for measuring the dimensions, displacement, etc. of an object, and particularly relates to an edge detection device for an optical measuring instrument for measuring the dimensions, displacement, etc. of an object. Alternatively, a photoelectric sensor receives the projected image of the object to be measured using the transmitted light or reflected light, extracts an electrical signal, and uses this signal to measure the dimensions of the RSS fixed object.An edge detection device in an optical measuring instrument. Regarding the improvement of

[Conventional technology]

Conventionally, this type of optical measuring instrument, for example, a projector, irradiates a measurement target on a stage with parallel light beams, and projects the measurement target onto a screen based on the transmitted light or reflected light. This method forms an image and measures the dimensions, shape, etc. of the object to be measured from this image, but the edges of the image of the object to be measured that are projected onto the screen generally have so-called blur, and therefore, It is difficult to move the object to be measured on the stage and accurately read the measurement value based on the coincidence of the image formed on the screen with the hairline. In order to solve this problem, in the past, by moving the edge of the image and the photoelectric sensor relative to each other, charging was performed based on the change in the area ratio between the bright and dark areas of the image projected on the light receiving surface of the photoelectric sensor. Some devices detect the edge of a projected image by comparing changes in the magnitude of an S-curve analog signal output from a sensor with a reference voltage. That is, a photoelectric sensor that is movable relative to the image of the object to be measured and that optically captures the image of the object to be measured and generates an S-curve-shaped analog signal at the edge thereof; and an output of the photoelectric sensor. There is an edge detection circuit that detects the intersection of an analog signal of 1 and a preset reference signal and outputs an edge signal of the image of the object to be measured, and a circuit that detects the edges of the object to be measured. Here, in the edge detection circuit, in order to avoid the influence of noise generated from peripheral devices, etc., a cross-point detection circuit is used to detect the intersection between the analog signal of the photoelectric sensor output and a preset reference signal. A filter is inserted in the reference signal to prevent it from becoming impossible to identify the intersection due to noise generated near the reference signal. However, when a filter is provided in this way, the detection signal rPrI! ! For example, if the measurement target is 2On/s (20μIll
/μs), a time delay of several μs occurs,
Lateral base 1μ...Measurement of accuracy becomes impossible. Furthermore, in recent years, high-precision measurement and high-speed feeding have been required for this type of optical dimension measuring machine, and in this case, a filter that aims to improve measurement accuracy by eliminating noise is required to There is a problem in that the time lag has become a factor in reducing measurement accuracy. Moreover, the measurement accuracy decreases even during normal times when no noise occurs. Conventionally, this problem has been solved by increasing the projection magnification in projectors, but this also has its limitations.

[Problems to be solved by the invention]

The present invention has been made in view of the above problems, and provides an edge detection device for an optical measuring instrument that eliminates the time lag caused by the filter by omitting the filter and enables accurate measurement. The purpose is to

[Means to solve the problem]

This invention is an optical measuring instrument that generates an edge signal by detecting the intersection of an S-curve analog signal generated at the edge of a measurement object and a preset reference signal. An edge detection device, an insulator, a reference signal setter for setting a high level and a low level sandwiching the set level of the reference signal, and a reference signal setting device for setting a high level and a low level that sandwich the set level of the reference signal, and when the analog signal changes from a high level to a low level, the analog signal and the reference signal are a first detector that detects the intersection of the analog signal and the high level to establish an output signal, and detects the intersection of the analog signal and the high level and releases the output signal when the analog signal changes from a low level to a high level; When the analog signal changes from high level to low level, the intersection of the analog signal and the low level is detected to establish an output signal, and when the analog signal changes from low level to high level, the analog signal a second detector that detects the intersection between the first detector and the reference signal to cancel the output signal; and an exclusive OR circuit that receives the output signals of the first detector and the second detector as inputs. , among the output signals of this exclusive OR circuit,
The above object is achieved by providing an edge signal generator that discriminates the output signal when the analog signal is in one of the falling and rising states and outputs an edge signal. Further, the first detector, the second detector, and the setting device each receive the reference signal and the analog signal as inputs, and one set has a positive hysteresis characteristic and the other has a negative hysteresis characteristic. The above object is achieved by constructing the comparator. Further, the edge signal generation circuit includes a filter for eliminating noise on the analog signal, a differentiating circuit for differentiating the analog signal after passing through the filter, and determining whether the output of the differentiating circuit is positive or negative. A region signal generator including a comparator that outputs a signal; and an AND gate that outputs an edge signal when signals are simultaneously output from the region signal generator and the exclusive OR circuit. It is something to be achieved. Further, the area signal generator is a first comparator that compares the differential output signal of the difference calculator 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 that compares the differential output signal with a low-level reference signal and outputs a hold signal when the differential output signal is higher than the low level; and a second comparator that outputs a hold signal when the differential output signal is higher than the low level; first and second sample and hold circuits that hold the analog signal based on the hold signal and sample the analog signal when the hold signal is input; and output signals of the first and second sample and hold circuits and the analog signal. A third comparator outputs a signal when the output signal is smaller than the analog signal, and compares the IFI output signal with the analog signal, and outputs a signal when the output signal is larger than the analog signal. and an exclusive OR gate that generates a region signal when only one of the third and fourth comparators outputs a signal. The goal is to achieve the following.

[Operation] In this invention, the filter is omitted, and the true edge is detected by specifying only one point where the noise-containing S-curve analog signal intersects the reference signal, and by not accepting subsequent noise. By detecting extremely close points as edges, generation of measurement WA differences due to time lag is prevented, and measurement accuracy is improved. Embodiments Examples of the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to a projector, and as shown in FIGS. 1 and 2, light from a light source lamp 1 is directed below a stage 3 through a condenser lens 2. The object to be measured 4 on the stage 3 is irradiated from above or from above the a-anastomosis 3 via another optical path, and based on the transmitted light or reflected light, it is projected onto the screen 6 via the projection lens 5. This is a projector 1o for forming a projected image 4A of a counter-dyed object 4 to be measured and indirectly measuring the dimensions of the object 4 to be measured using this projected image 4A. Projection image 4A of the measurement object 4 that is relatively movable
a photoelectric sensor 12 that optically captures the image and generates an S-curve-shaped analog signal at its edge;
an edge detection circuit 14 that detects the intersection between the output analog signal and a preset reference signal and outputs an edge signal of the projected image 4A;
2, and measures the dimensions of the object to be measured 4 from the amount of relative movement between the object to be measured 4 and the photoelectric sensor 12 while the edge signal is generated. In the projection 110 as described above, the edge detection circuit 14 is set with a high level and a low level that sandwich the set level of the reference signal from the reference signal setter 18, and when the analog signal changes from a high level to a low level, , detecting the intersection of the analog signal and the reference signal to establish an output signal, and detecting the intersection of the analog signal and the high level when the analog signal changes from low to high, and canceling the output signal; a first comparator circuit 20 having a positive hysteresis characteristic that, when the analog signal changes from a high level to a low level, detects the intersection of the analog signal and the low level to establish an output signal; When the analog signal changes from a low level to a high level, detecting the intersection of the analog signal and a reference signal,
a second comparator circuit 22 with a positive hysteresis characteristic that cancels the output signal; and these first comparator circuits 20
and an exclusive OR circuit 24 which inputs the output signal of the second comparison circuit 22;
Of the output signals of the circuit 24, an edge signal generation circuit 26 is provided which discriminates the output signal when the analog signal is in one of the falling and rising states and outputs an edge signal. The photoelectric sensor 12 generates an S-curve phase shift signal a based on the brightness that occurs when moving relative to the sexual force projection image 4A.
, b, and includes two light receiving elements 12A and 12B arranged concentrically in a plane substantially parallel to the movement plane, and sensor output signals a, based on the outputs of both light receiving elements 12A and 12B.
The level at the sensor output terminals 13A and 13B of b is
It is formed to have the same value in each of the bright and dark states that occur during the relative movement. The edge signal generation circuit 26 includes a filter 27 for eliminating noise on one output signal a of the photoelectric sensor 12, a differentiation circuit 28 for differentiating the analog signal after passing through the filter 27, and an output of the differentiation circuit 28. A comparator 29 that determines the positive or negative of and outputs a signal when it is negative, this comparator 2
an area signal generator 31 including a digital signal generator 30 that outputs a digital signal when the output signal from 9 rises and falls; signals are simultaneously output from the @ area signal generator 31 and the exclusive OR circuit 24; and an AND circuit 32 that outputs an edge signal when the edge signal is output. Reference numeral 34 in FIG. 2 indicates the exclusive OR circuit 24.
This shows a pulse signal generator for outputting a pulse signal when a signal is output from. Further, reference numeral 38 is connected to the sensor output terminals 13A and 13B of the photoelectric sensor 12, and calculates the difference between the phase shift signals AB and outputs this to the first and second comparison circuits 20 and 22. Show the difference calculator. Further, between the edge detection circuit 14 and the photoelectric sensor 12, there are installed current-to-voltage converters 40A and 40 for exchanging the outputs of the light receiving elements 12A and 12B into voltage signals.
B is placed. As shown in FIG. 1, the photoelectric sensor 12 is provided integrally with a transparent plate 33 placed parallel to and movable on the upper surface of the screen 6 of the projector 10. 33, so that it can be moved. The light receiving element 12A constituting the photoelectric sensor 12 is formed to have a circular cross section, and the light receiving element 12B is similar to the light receiving element 1.
2A, the light receiving elements 12A are spaced apart in the radial direction.
It is formed into a concentric ring shape. The displacement detection device 16 includes an encoder 46 for detecting the amount of movement of the document stage 3, and counts the output of the encoder 46, and detects the object to be measured when the edge signal from the edge detection circuit 14 is input. A counter 48 outputs a signal indicating the position of the object 4. Next, the operation of the above embodiment will be explained. Projection image II of the measurement object 4 formed on the screen 6
) 4A, the photoelectric sensor 12 is moved in one direction so that the edge of the projected image e4A crosses the photoelectric sensor 12. When the projected image tl14A approaches the photoelectric sensor 12 relatively and passes through it, the light receiving elements 12A and 12B
and current-voltage converters 40A, 40B
The output signals generated from the sensor output terminals 13A and 13B through the sensor output terminals become S-curve-shaped phase-shifted signals with equal amplitudes, as shown by symbols a and b in FIG. 3<A). As shown in FIG. 3(B), these output signals are computed into a-b by the difference computing unit 24 and output. If there is noise, the signal outputted by the difference calculator 38 remains contaminated with noise, and is outputted from the first comparator circuit 2.
o and the second comparison circuit 22. The first comparison circuit 20 compares the analog signal and the reference signal ■re when the input analog signal changes from high level to low level.
r to establish an output signal C, as shown in FIG. is detected, and the output signal 0 is released. On the other hand, when the signal a-b changes from a high level to a low level, the second comparator circuit 22 detects the intersection of the signal and the low level, as shown in FIG. 3 (D>). To,
The output signal d is established, and when the signal changes from low to high, the intersection between the signal and the reference signal vrer is detected and the output signal d is released. exclusive O to which the output signals C and d are input;
When only one of these signals C and d is input, the R circuit 24 outputs a signal e to the pulse signal generator 34, as shown in FIG. 3(E). The pulse signal generator 34 outputs a pulse signal to the AND circuit 32 as shown in FIG. 3F based on the output signal from the exclusive OR circuit 24. One output signal a of
input to the filter 27 in the area signal generator 31;
After noise is removed here, the signal is input to the differentiating circuit 28. In the differentiation circuit 28, the input signal a is differentiated and outputted to the comparator 29. The comparator 29 compares the signal from the differentiating circuit 28 with a reference signal, and outputs a signal to the digital signal generator 3o when the signal from the differentiating circuit 28 is negative, and outputs a signal to the digital signal generator 304. As shown in Figure 3 (G), “1
" is output as a digital signal 9. The pulse signal r from the pulse signal generator 34 and the digital signal port from the area signal generator 31 are input to an AND gate 32, and when both the input signals are "1" (this As shown in FIG. 3(H), for example, an edge signal (pulse signal) 11 of 10 μs is output, and at this point, the edge of the projected image 4A is detected. 46 detects the amount of movement of the stage 3, and a counter 48 counts the output signal of the encoder 46 as an absolute position signal at each time.The edge signal h from the AND gate 32 is This is input to the counter 48 in the displacement detection device 16, and the counter 48 outputs the counted displacement amount, that is, the position signal of the measuring object 4, to the storage device 50 when the edge signal is input. The output signal from the digital signal generator 36 is displayed on a display or output to a printer. There is a slight time lag in the digital signal g compared to the actual increase or decrease in the analog signal a, but since the area signal generator 30 outputs it in a relatively wide time period before and after the edge, the filter 28 is not considered a problem. In this example, the time lag due to
The point where the analog signal intersects with the reference signal V ref is specified between a high level and a low level that sandwich the set level of the reference signal Vrer, and the points that approximate the actual intersection are condensed and detected as edges. However, there is no problem if the range of the high level and low level is set within the overall measurement accuracy. Furthermore, noise on the S-curve signal does not always occur, and under normal conditions, the actual edge and the detected edge exactly match. Furthermore, if the measurement speed is increased, the slope of the a-b S-curve signal becomes larger, so the faster the measurement is, the closer the actual edge and the simulated edge are. Measurement accuracy will be improved. Further, in this embodiment, the light receiving elements 12A and 12B constituting the photoelectric sensor 12 are formed in a concentric shape, and the sensor output terminals 13A and 13B generated by these elements
Since the output levels of the signals are made equal, the boundary line between the light receiving elements 12A and 12B does not coincide with the direction of movement, and the output level of the photoelectric sensor 12 is uniform regardless of the direction of movement relative to the projected area II) 4A. Therefore, there is no restriction on the direction of movement of the charged sensor relative to the object to be measured, and edge detection can be performed with high precision. Further, as described above, since the light receiving elements 12A and 12B constituting the photoelectric 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 applicable to small measuring instruments, but also simplifies the supporting means, and
In a projector, the effective viewing range of the screen can be increased. Furthermore, since the photoelectric sensor 12 is small, it can also be applied to edge detection of a complex-shaped object to be measured. In the above embodiment, both the first comparison circuit 2o and the second comparison circuit 22 are formed from comparison circuits having positive hysteresis characteristics, but the present invention is not limited to this. Instead, the reference signal setter 18, a first detector corresponding to the first comparison circuit, and a second detector corresponding to the second comparison circuit 22 may be provided separately and independently. Further, 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 a certain interval, so that a pair of S-curve phase shift signals a and b are obtained. However, the present invention is not limited to this, and the light receiving element constituting the sensor may be of any type as long as it can obtain an S-curve analog signal. It may be a single light-receiving element, a combination of an optical fiber and a light-receiving element, or a combination of three or more light-receiving elements. Further, the area signal generator 31 in the embodiment described above is not limited to the configuration of the embodiment as long as it detects the rise or fall of one of the output signals from the photoelectric sensor. Thus, for example, as shown in FIG. 4, the area signal generator 52 compares the differential output signal of the difference calculator 38 with a high level reference signal, and when the differential output signal is lower than the high level, a first comparator 54 that outputs a hold signal; a second comparator 56 that compares the differential output signal with a low level reference signal and outputs a hold signal when the differential output signal is higher than the low level; and the photoelectric sensor 1 based on the hold signals inputted from the second comparators 54 and 56.
First and second sample and hold circuits 58.2 hold one sensor output signal a of No. 2, and sample the sensor output No. 15 a when the hold signal is input.
60 and these first and second sample and hold circuits 5
8. A third comparator 62 that compares the output iM of 60 and the sensor output signal a and outputs a signal when the output signal is smaller than the sensor output signal a, and the output signal and the sensor output signal. a fourth comparator 64 that outputs a signal when the output signal is larger than the sensor output signal a;
and an exclusive OR gate 66 that generates a III-range signal when only one of the third and M4 comparators 62, 64 outputs a signal. In the case of this example, vibration etc. cause the sensor output to
Even when a signal undergoes a temporary fluctuation, it is possible to reliably output a region signal at a time point including a cross point without erroneously outputting the region signal. Furthermore, in the embodiment, the light receiving elements 12A and 12B are
By making the light receiving areas equal, the sensor output terminals i3A and 13B are made equal.
This can be done as long as the output signals at the sensor output terminals 13A and 138 are at the same level. The output levels of both sensor output terminals 13A and 13B may be made equal without providing the sensor output terminals 13A and 13B. Furthermore, in the above embodiment, within the projection fl! Sensor 7 for 4A
However, this may be done by moving the projection f14A relative to the sensor 7 by moving the stage 3, for example. 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 optical measuring instruments for directly or indirectly measuring the dimensions of objects to be measured. Effects of the Invention 1 Since the present invention is configured as described above, it is possible to eliminate the time delay of the detection signal with respect to the actual position of the photoelectric sensor with respect to the object to be measured, and to perform high-speed, high-precision dimension measurement. It has an excellent effect.

[Brief explanation of drawings]

Fig. 1 is an optical system diagram showing an embodiment in which the optical dimension measuring machine 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 the embodiment. FIG. 4 is a block diagram showing the main parts of the second embodiment of the present invention. 4...Measurement object, 4A...Projected image, 1
0... Projector, 12... Photoelectric sensor, 1
2A, 12B... Light receiving element, 13A, 13B... Sensor output terminal, 14... Edge detection circuit, 16... Displacement detection device, 18... Reference signal setter, 2o... First 22... Second comparison circuit, 24... Exclusive OR circuit, 26... Edge signal generation circuit, 27... Filter, 28... Differential circuit,
29...Comparator, 31.52...Area signal generator, 32...AND gate, 54...First comparator, 56...Second comparator, 58...th 1 sample hold circuit, 60... second sample hold circuit, 62... third comparator, 64... fourth comparator, 66... exclusive OR gate.

Claims (4)

[Claims] (1) In an edge detection device for an optical measuring instrument that generates an edge signal by detecting an intersection between an S-curve analog signal generated at an edge portion of a measurement object and a preset reference signal, the reference signal A reference signal setting device for setting a high level and a low level that sandwich the set level of and a first detector that detects the intersection of the analog signal and the high level and cancels the output signal when the analog signal changes from a low level to a high level; when the analog signal changes from a low level to a high level, detecting an intersection between the analog signal and the reference signal to establish an output signal; a second detector that cancels the output signal; an exclusive OR circuit that receives the output signals of the first detector and the second detector; An edge detection device for an optical measuring instrument, comprising an edge signal generation circuit that discriminates an output signal when an analog signal is in one of falling and rising states and outputs an edge signal. (2) The first detector, second detector, and setting device are
each inputs the reference signal and analog signal,
2. An edge detection device for an optical measuring instrument according to claim 1, wherein the edge detection device is comprised of two sets of comparison circuits, both of which have positive hysteresis characteristics. (3) The edge signal generation circuit includes a filter for eliminating noise on the analog signal, a differentiating circuit for differentiating the analog signal after passing through the filter, and determining whether the output of the differentiating circuit is positive or negative. and an AND gate that outputs an edge signal when signals are simultaneously output from the region signal generator and the exclusive OR circuit. An edge detection device in an optical measuring instrument according to claim 1 or 2. (4) The region signal generator is a first region signal generator that compares the differential output signal of the difference calculator 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 that compares the differential output signal with a low-level reference signal and outputs a hold signal when the differential output signal is higher than the low level; first and second sample-and-hold circuits that hold the analog signal based on the hold signal and sample the analog signal when the hold signal is input; and output signals of the first and second sample-and-hold circuits. and the analog signal, and outputs a signal when the output signal is smaller than the analog signal.
a fourth comparator that compares the output signal and the analog signal and outputs a signal when the output signal is larger than the analog signal, and only one of the third and fourth comparators. 3. An edge detection device for a photoelectric measuring instrument according to claim 1, further comprising an exclusive OR gate that generates a region signal when outputting a signal.