JPH0419482B2 - - Google Patents

Description

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

The present invention relates to an edge detection device for a projected image for measuring the dimensions, displacement, etc. of an object, and in particular,
The object to be measured is illuminated with a measuring light beam, and the projected image of the object by transmitted light or reflected light is scanned by a sensor consisting of a light-receiving element to extract an electrical signal. The present invention relates to an edge detection device for a projected image in an optical measuring instrument for measuring dimensions, determining position, determining shape, etc. of a measured object.

[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, conventionally, by moving the edge of the image formation relative to the photoelectric element, the photoelectric element can be detected from the change in the area ratio between the bright and dark areas of the image projected on the light receiving surface of the photoelectric element. There is a device that detects the edge of a projected image by comparing a change in the magnitude of an electric signal output from an element with a reference voltage. However, this method has problems in that it is greatly affected by noise such as ambient light, and the measurement accuracy is greatly reduced due to fluctuations in the signal or reference voltage obtained from the photoelectric element. Furthermore, the photoelectric element is moved relative to the boundary (edge) of the projected image on the screen, the output signal at that time is second-order differentiated to obtain a waveform signal, and edges are detected by comparing this with a reference voltage. However, depending on the speed of relative movement between the photoelectric element and the projected image, the position of the detected edge may differ, and as mentioned above, measurement accuracy may decrease due to fluctuations in the reference voltage. The problem is that it is large. Furthermore, two photoelectric elements are arranged and moved relative to the edges of the projected image, a waveform signal is obtained from the multiple output signals obtained by this, and by comparing this with a reference voltage, There are devices that detect edges, but as mentioned above, the measurement becomes extremely unstable due to relative changes between the output signal obtained from the photoelectric element and the reference voltage, level fluctuations, etc. There are problems in that the area is narrow, measurement modes are limited, and the sensor section or circuit section is complicated. In particular, in projectors, the brightness of the projected image on the screen changes due to fatigue of the irradiation light source lamp, lens characteristics of the projection system, and ambient light, and the brightness of the projected image changes due to switching of the projection magnification. Furthermore, as a condition on the measurer's side, for example, the optimum brightness for the work differs depending on the color of the measurer's eyes (which differs depending on the race), so this must be selected appropriately. If the range of application to the illuminance of the irradiated light is narrow, the performance of the projector will be reduced as a result. Furthermore, in the conventional edge detection method, if the projected image is out of focus, the output waveform of the photoelectric element becomes gentle, so that accurate edge detection cannot be performed. This problem is common not only to projectors but also to edge detection in optical measuring instruments that detect transmitted light or reflected light to directly or indirectly measure the dimensions of objects to be measured. This is a problem. On the other hand, as disclosed in JP-A No. 58-173408, for example, there is an optical measuring instrument for directly or indirectly measuring the dimensions of an object by detecting transmitted light or reflected light. In the edge detection device, the four edge detectors are arranged in a plane substantially parallel to the plane of movement so as to generate at least two sets of phase shift signals based on the brightness and darkness that occurs when moving relative to the object to be measured.
a sensor consisting of two light receiving elements, first and second calculation means for calculating the difference between the phase shift signals of each set, and a third calculation means for calculating the difference between the output signals of the first and second calculation means. and a fourth calculating means for calculating the sum, and outputting a cross signal between the output signal of the third calculating means and a reference level, which occurs while the output signal of the fourth calculating means is at a predetermined level. A device equipped with a detection means has been proposed. This edge detection device has a simple configuration and is capable of measuring without being affected by the light intensity irradiating the measurement target, noise such as disturbance light during measurement, and fluctuations in the output signal of the photoelectric element or the reference voltage. The edges of the object can be detected, and even if the projected image is out of focus in the projector, the edges can be detected accurately.Furthermore, by directly processing the analog signal from the photoelectric element, , it has the advantage of being able to detect edges of the object to be measured. However, the edge detection device disclosed in the above-mentioned Japanese Patent Application Laid-open No. 58-173408 is designed to determine the point where the output signal from the sensor crosses the reference signal, that is, a specific area including the edge position of the object to be measured. As means for this, the area signal is output while the output signal of the fourth calculation means is at a predetermined level, but when the level of the output signal of the fourth calculation means is low, the actual edge signal is output. There is a problem in that it may not be possible to generate an area signal depending on the location. That is, if the object to be measured is made of a material that cannot completely block light, such as a translucent glass product, the brightness of the projected image obtained by illuminating the object to be measured is When the ratio of dark to bright areas becomes small, and the bright area is set to ``1'' and the completely dark area to ``0'', the dark area in the projected image of the semi-transparent glass product will be smaller than 1 and larger than 0. , because the difference between the bright and dark areas is small, it may not be possible to obtain a signal of a predetermined level or higher, and therefore it may not be possible to generate a region signal. Furthermore, since the sensor of the edge detection device is formed of four light-receiving elements arranged in a square shape, for example, when moving relative to the projected image on the screen of a projector, the border line of the light-receiving elements and When the directions of movement match, the edges of the projected image may not be detected, which poses a problem in that the direction of movement of the sensor with respect to the projected image is restricted. On the other hand, the present applicant has proposed, in Japanese Patent Application No. 59-249278, that the object to be measured is, for example, a translucent glass product, etc.
We have proposed an edge detection device for an optical measuring instrument that can reliably detect edges even in the case of materials that cannot completely block light. The area signal generator in the edge detection device described above uses an analog sample-and-hold circuit to generate the area signal, so there is a risk that the area signal will not be excited, resulting in erroneous measurements. Ta. In other words, the analog sample-and-hold circuit is
Generally, it includes a transmission gate, a capacitor, an amplifier, etc., and because current leaks through these, the hold signal changes at a constant attenuation rate. In particular, when the feed speed of the stage on which the object to be measured is placed is very slow, or when the stage is stopped without measuring for a while after holding the hold signal (an analog signal) and then starts measurement again. In some cases, the high hold signal is attenuated and becomes smaller than the sensor output signal, and in such cases, the area signal becomes low level and the edge signal that should be output is not output. , erroneous measurements occur. Furthermore, with the method of setting the reference value using a sample-and-hold circuit, there is no reference value when the edge detection device is powered on, and area signals are excited even in bright or dark areas of the projected image on the screen. Another problem is that a separate initial set circuit must be provided.

[Purpose of the invention]

This invention has been made in view of the above-mentioned problems, and is applicable when the relative moving speed of the sensor with respect to the projected image is slow, or when there is an edge of the projected image near the light-receiving part of the sensor, and when the measurement is stopped. An object of the present invention is to provide an edge detection device for a projected image that prevents erroneous measurements by reliably exciting a region signal even when restarting measurement. Another object of the present invention is to provide a projection image edge detection device that does not require an initial set circuit.

[Means to solve the problem]

The present invention provides an edge detection device for a projected image in an optical measuring instrument for measuring dimensions using a projected image of a measurement target using transmitted light or reflected light, which includes an inner light-receiving element having a circular outer periphery; an outer light-receiving element arranged in an annular shape surrounding the light-receiving element, concentrically with the light-receiving element, and having a substantially equal area; It is composed of divided light-receiving elements divided into even numbers, and based on the brightness and darkness that occurs when moving relative to the object to be measured,
a sensor that generates a phase shift signal; and an area signal generation circuit that outputs an area signal when a difference between the outputs of one of the divided light receiving elements diametrically opposed to each other exceeds a predetermined value; a detection circuit that outputs an edge signal when the sum of the outputs of the plurality of divided light receiving elements matches the value of the output of the other light receiving element while the area signal is being output from the signal generating circuit; The above objective is achieved by providing the following. Further, the above object is achieved by dividing the one light receiving element into four sections and comprising first to fourth divided light receiving elements in the circumferential direction. Further, the area signal generation circuit includes a first difference calculator that calculates the difference between the outputs of the first and third divided light receiving elements, and a first difference calculator that calculates the difference between the outputs of the second and fourth divided light receiving elements. A second difference calculator compares the output signal of the first difference calculator with a plus side reference signal and a minus side reference signal, and when the output signal is not between the values of these reference signals, the signal is The first output
a window comparator, and a second difference calculator that compares the output signal of the second difference calculator with the plus side reference signal and the minus side reference signal, and outputs a signal when the output signal is not between the values of these comparison signals. The above object is achieved by comprising a window comparator, and an OR gate that outputs a region signal when at least one of the first and second window comparators outputs a signal.

[Effect]

In this invention, the signal input to the window comparator in the area signal generation circuit is the difference between the output signals of the divided light receiving elements, and the signals to be compared with these signals are preset plus side and With the reference signal Vref ⁺ on the negative side
Vref ^- , it is possible to reliably generate an area signal even when the relative speed of the sensor to the projected image is slow, or when the sensor resumes measurement after a temporary pause near the edge of the projected image. I can do it. Further, without providing an initial set circuit or the like, it is possible to prevent the area signal from being erroneously excited when the power is turned on.

【Example】

Embodiments 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,
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. Then, based on the transmitted light or reflected light, a projected image 4A of the measurement object 4 is formed on the screen 6 via the projection lens 5, and the dimensions of the measurement object 4 are indirectly determined by this projection image 4A. In an edge detection device for a projected image in a projector 10 for measuring, etc., a circular inner light receiving element 1 is used.
2, and an outer light-receiving element 14 which is arranged in an annular shape surrounding the inner light-receiving element 12, concentrically with the inner light-receiving element 12, and having an equal area;
4 consists of first to fourth divided light receiving elements 14A to 14D equally divided in the circumferential direction, and based on the brightness and darkness that occurs when moving relative to the measurement object 4,
A sensor 16 that generates a phase shift signal, and first and third divided light receiving elements 14A and 14C that face each other in the diametrical direction among the divided light receiving elements 14A to 14D.
Alternatively, a region signal generation circuit 18 outputs a region signal when the difference between the outputs of the second and fourth divided light receiving elements 14B and 14D exceeds a predetermined value, and a region signal is output from the region signal generation circuit 18. In between, a detection circuit 20 is provided which outputs an edge signal when the sum of the outputs of the plurality of divided light receiving elements 14A to 14D matches the value of the output of the inner light receiving element 12. The area signal generation circuit 18 includes a first difference calculator 22 that calculates the difference between the outputs of the first and third divided light receiving elements 14A and 14C, and a first difference calculator 22 that calculates the difference between the outputs of the first and third divided light receiving elements 14A and 14C;
A second difference calculator 24 calculates the difference between the outputs of the divided light receiving elements 14B and 14D, and the output signal of the first difference calculator 22 and the positive side reference signal Vref ⁺ and the negative side reference signal Vref ^- . a first window comparator 26 that compares and outputs a signal when the output signal is not between the values of these reference signals Vref ⁺ and Vref ^- , and the output signal of the second difference calculator 24 and the positive side reference. Signal Vref ⁺ and minus side reference signal
Vref ^- and the output signal is compared to these reference signals
a second window comparator 28 that outputs a signal when the value is not between Vref ⁺ and Vref ^- ;
and an OR gate 30 that outputs a region signal when at least one of the second window comparators 26 and 28 outputs a signal. As shown in FIG. 1, the sensor 16 is provided integrally with a transparent plate 7 that is slidably placed on the upper surface of the screen 6 of the projector 10 in parallel thereto. It is also movable. The outer light receiving element 14 of the sensor 16 is formed in a concentric ring shape around the inner light receiving element 12 at intervals in the radial direction. Here, the total area of the outer light receiving elements 14 does not necessarily have to match the area of the inner light receiving elements 12. In that case, by adjusting the gain of the preamplifiers 12A and 15A to 15D, for example, when the whole is in a bright area, the summation unit 3
It is only necessary that the output b of the preamplifier 2 and the output a of the preamplifier 12A match. When the outputs match by adjusting the gain of the preamplifier, the areas of both light receiving elements are considered to be substantially equal. Further, the detection circuit 20 includes preamplifiers 15A to 15A.
a summation unit 32 that calculates the sum of the output signals of the four divided light-receiving elements 14A to 14D that are inputted via the light-receiving element 15D;
and a comparator that compares the output signal of the difference calculator 34 with a reference level signal and outputs a signal when they match, that is, at a cross point. 36, a pulse signal generator 38 that generates an edge pulse signal based on the signal output from the comparator 36, and a signal output from both this pulse signal generator 38 and the area signal generation circuit 18. Output edge detection signal only when
It is equipped with an AND gate 40. The output signal from this AND gate 40 is sent to a counter 44 of a displacement detection device 42 linked to the stage 3.
The edge detection signal is output to the This displacement detection device 42 is composed of an encoder 46 that is linked to the document stage 3 and generates a pulse signal according to the amount of movement thereof, and the counter 44 that reads the pulse signal output from the encoder 46. There is. This counter 44 is configured to output its read value to a storage device 48 when an edge detection signal is input from the AND gate 40. Next, the operation of the above embodiment will be explained. By moving the stage 3, the projected image 4A of the measurement object 4 formed on the screen 6 is moved relative to the sensor 16 in the X direction in FIG. The edge should cross the sensor 16. When the projected image 4A approaches the sensor 16 and passes through it, the inner light receiving element 12
A signal obtained by the light receiving element 14 and adjusted by the preamplifier 12A and input to the detection circuit 20, and a signal obtained by the light receiving element 14 and adjusted by the preamplifier 15A to 15D.
The signal that has been adjusted by the summing unit 32 in the detection circuit 20 becomes a phase-shifted signal with equal amplitude, as shown by symbols a and b in FIG. 3A. As shown in FIG. 3B, these output signals are calculated by the difference calculator 34 to give c=ba-a and are output. The signals obtained by the first and third divided light receiving elements 14A and 14C in the outer light receiving element 14 pass through preamplifiers 15A and 15C, and are converted into signals A,
It is input as C to the first difference calculator 22. This first difference calculator calculates the difference between the two input signals A and C, and the resulting signal f=A-
C is output to the first window comparator 26. Further, after the signals obtained by the second and fourth divided light receiving elements 14B and 14D in the outer light receiving element 14 are adjusted by preamplifiers 15B and 15D, a second difference calculation is performed as signals B and D. vessel 24
is output to. This second difference calculator 24 calculates the difference between the two input signals B and D and outputs the signal g=B−D to the second window comparator 28 . Here, the sensor 16 detects the first and third images with respect to the projected image 4A, as shown in FIG.
When approaching relatively from the first divided light receiving element 14A side in the direction of the diameter passing through the center of the divided light receiving elements 14A, 14C, the output signal f of the first difference calculator 22 is shown in FIG. 3D. You will be able to do it. On the other hand, the second and fourth divided light receiving elements 1
4B and 14D are moved relative to the edge of the projected image 4A so that they are always at the same distance,
The difference between the two output signals, that is, the output signal g of the second difference calculator 24 becomes g=0. The first window comparator 26
When the value of the input signal f from the difference calculator 22 is compared with the preset positive reference signal Vref ⁺ and negative reference signal Vref ^- , and the output signal g is not between the values of these reference signals. The output signal h becomes high level. That is, the signal h as shown in FIG. 3E is OR
It will be output to the gate 32. On the other hand, the output signal of the second difference calculator 24 is g=0
Then, the positive and negative side reference signals Vref ⁺
Vref ^- , the second window comparator 28 does not output a signal. Therefore, only the output signal h of the first window comparator 26 is input to the OR gate 30, and therefore, the OR gate 30 receives the area signal j as shown in FIG. 3F from the detection circuit 20. AND
It will be output to the gate 40. On the other hand, the differential output signal c output by the difference calculator 34 is input to a comparator 36, and this comparator 36 receives the signal k when the differential output signal c crosses the reference level signal of 0. Output. Comparator 36
Based on the output signal k of the pulse signal generator 38
is a pulse signal l as shown in Fig. 3C.
Output to AND gate 40. Pulse signal l from the pulse signal generator 38
And the digital signal j from the OR gate 30 is
When both input signals are at high level, the AND gate outputs a pulse signal m of, for example, 10 μSec, as shown in FIG. 3G, and at this point, the projected image 4A Detect edges. Here, the comparator 36 outputs a signal k when the input signal c crosses the zero level. Therefore, the comparator 36 outputs an unnecessary signal k even if the sensor 16 is outside or inside the edge of the projected image 4A, that is, in a bright area or a dark area, and each time the pulse signal generator 38 outputs an unnecessary signal k. This results in the output of an unnecessary pulse signal _L1 or _L2 as shown in FIG. Since an edge signal is output only when both are input to the AND gate 40, an edge signal based on unnecessary pulse signals _L1 and _L2 will not be output. In this embodiment, the area signal generation circuit 18
The first and second window comparators 2 in
The signals inputted to 6 and 28 are transmitted to the divided light receiving element 14.
^The sensor ^is 16
Even when the relative speed of the sensor 16 to the projected image 4A is slow, or when the sensor 16 temporarily pauses and then resumes measurement near the edge of the projected image 4A, the area signal can be reliably generated. Further, without providing an initial set circuit or the like, it is possible to prevent the area signal from being erroneously excited when the power is turned on. The operation of the above embodiment is as shown in FIG.
This is a case where the sensor 16 is set to cross the edge of the projected image 4A in the diametric direction passing through the center of C, but when the sensor 16 is moved in a direction perpendicular to the above (Y direction) or Even when moving diagonally, the edge signal m can be obtained in the same way as described above. Further, in the above embodiment, the inner light receiving element 12 constituting the sensor 16 is circular, and the outer light receiving element 14 is composed of divided light receiving elements 14A to 14D divided into four equal parts in the circumferential direction. The present invention is not limited to this, but the inner light receiving element 12 may be divided. Further, both the inner light receiving element 12 and the outer light receiving element 14 may be ring-shaped. Furthermore, the number of divided sections of the inner or outer light receiving elements 12, 14 may be an even number of four or more. Therefore, the inner light receiving element 12 or the outer light receiving element 1
4 may be equally divided into 6 or 8 pieces. Further, in the above embodiment, the projection image 4A is moved relative to the sensor 16 by moving the stage 3, but this may be done by moving the sensor 16 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 can be used to measure the edge of a projected image on an optical measuring device or the like. This is generally applied to detection devices. 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 or the like. The present invention is also applied to an edge detection device in a measuring instrument, etc., which measures the dimensions of an object to be measured from its bright and dark areas.

【Effect of the invention】

Since the present invention is configured as described above, even if the moving speed of the sensor with respect to the projected image is slow, or even if the sensor is temporarily stopped near the edge of the projected image and then moved again, the area signal can be reliably detected. It has the excellent effect of being able to detect the edges of a projected image by excitation.

[Brief explanation of drawings]

Fig. 1 is an optical system diagram showing an embodiment in which the projection image edge detection device 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 same implementation. It is a diagram showing the process of signal processing in an example. 4...Measurement object, 4A...Projected image, 12...
...Inner light receiving element, 14...Outer light receiving element, 14A
~14D...divided light receiving element, 16...sensor,
18... area signal generation circuit, 20... detection means,
22...First difference calculator, 24...Second difference calculator, 26...First window comparator, 28
...Second window comparator, 30...OR
Gate, 32...Summing unit, 38...Pulse signal generator, 40...AND gate.

Claims (1)

[Scope of Claims] 1. An edge detection device for a projected image in an optical measuring instrument for measuring dimensions using a projected image of an object to be measured using transmitted light or reflected light, comprising: an inner light-receiving element having a circular outer periphery; , an outer light-receiving element is arranged surrounding the inner light-receiving element, concentrically with the inner light-receiving element, and having a substantially equal area; a sensor that is composed of four evenly divided light receiving elements and generates a phase shift signal based on the brightness and darkness that occurs when moving relative to the object to be measured; and a sensor that generates a phase shift signal in the diametrical direction of one of the divided light receiving elements. an area signal generation circuit that outputs an area signal when the difference in output between the divided light receiving elements facing each other exceeds a predetermined value; 1. A projection image edge detection device comprising: a detection circuit that outputs an edge signal when the sum of the outputs of one light-receiving element matches the value of the output of the other light-receiving element. 2. The projection image edge detection device according to claim 1, wherein the one light receiving element is divided into four sections and is composed of first to fourth divided light receiving elements in the circumferential direction. 3. The area signal generation circuit includes the first and third area signal generation circuits.
a first difference calculator that calculates the difference between the outputs of the divided light receiving elements; a second difference calculator that calculates the difference between the outputs of the second and fourth divided light receiving elements; and the first difference calculator. a first window comparator that compares the output signal of the device with a positive reference signal and a negative reference signal and outputs a signal when the output signal is not between the values of these reference signals; and the second difference calculation. a second window comparator that compares the output signal of the device with a positive reference signal and a negative reference signal and outputs a signal when the output signal is not between the values of these reference signals; 3. The projection image edge detection device according to claim 2, further comprising an OR gate that outputs an area signal when at least one of the window comparators outputs a signal.