JPH01227003A - Measuring apparatus of dimensions - Google Patents

Abstract

PURPOSE:To enable the accurate measurement of an end part of an object of inspection, by a method wherein a regular time of the rise of an image- sensing element signal is determined and a prescribed proportionally-distributed value of an upper wave value after a fixed time from said time is compared with a signal value delayed sufficiently therefrom to generate an edge signal. CONSTITUTION:A light from an object of inspection is sensed by an image- sensing element, and a signal thereof is passed through a low-pass filter 19 to be a signal rising smoothly, so as to improve a resolution. Subsequently, this signal is compared with a reference value 21 by a primary comparator 20 to determine a regular time for the rise. An upper wave value of the signal after a fixed time from said regular time is measured, and a value obtained by turning said value to be a threshold value of 50% and a value of a signal delay 25 obtained by delaying the regular time sufficiently for a prescribed time are compared with each other by a secondary comparator 26 to generate a prescribed edge value. By this method, a time corresponding to a distance of a prescribed rise is measured, and thereby the end part of the object of inspection and, accordingly, the dimensions thereof can be measured accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dimension measuring device that optically measures the dimensions of an object to be inspected and converts the measurements into electrical signals.

[Conventional technology]

In recent years, with the development of optical imaging devices, it has become common to optically measure the dimensions of objects to be inspected, such as plates.

In conventional measurement devices using optical imaging, an imaging element is placed on the imaging plane of a lens based on the principle of a camera, and the dimensions of the object to be inspected are measured based on the size of the image.

However, such a measuring device has a problem in that when the distance from the lens to the object to be inspected changes, the size of the captured image changes, resulting in errors in measurement.

Therefore, the present inventor previously proposed an imaging device for an object to be inspected that solves these problems in Japanese Patent Application No. 61-210481, and applied this device to capture the edge of a steel plate as shown in FIG. We have developed a dimension measuring device 10 that measures .

In this figure, 11 is a lower light source (fluorescent lamp), 12 is a concave mirror that is an example of a light converging means, 13 is a plane mirror, 14 is a filter, 15 is an imaging lens, 16 is a linear array that is an example of an imaging device, Reference numeral 17 indicates a steel plate which is an example of the object to be inspected. Therefore, the light rays from the end of the steel plate 17 that are parallel to the optical axis are transmitted to the concave mirror 12, the plane mirror 13, and the imaging lens 1.
5, is imaged onto a linear array 16, and converted into an electrical signal. Therefore, even if the distance from the concave mirror 12 to the steel plate 17 changes depending on the device 10, the light rays required for imaging are parallel rays, so an image of the same size can be formed on the linear array 16.

[Problem that the invention seeks to solve]

However, since the linear array 16 has a plurality of light-receiving elements arranged in a straight line, its output becomes step-like as shown in FIG. The problem was that it was difficult to decide whether to do so.

In particular, the above-mentioned device 10 has a characteristic that the image becomes blurred when the distance between the steel plate 17 and the concave mirror 12 changes, and as a result, the output value shown in FIG. 5 becomes smooth, making it more difficult to detect the end face of the object to be measured. There was a problem that.

Since the output is stepped, there is a problem in that it is difficult to obtain a detection accuracy smaller than the length of a single light receiving element.

Furthermore, in the above device 10, as shown in the principle diagram in FIG. 6, since a concave mirror (parabolic mirror) 12, which is an example of a light converging means, is used, the solid line m in the graph of FIG. As shown in FIG. 2, the relationship between the height h' of the received light image and the actual value does not match the straight line n, which causes a problem in measurement errors.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a dimension measuring device that solves the above-mentioned problems.

[Means for solving problems]

A dimension measuring device according to a first aspect of the invention that meets the above object uses a first light converging means larger than the measurement length to input only parallel light from the object to be inspected into a second light converging means having a small diameter. and placing an imaging device on an imaging plane of the object to be examined by combining the first light converging means and the second light converging means,
In a dimension measuring device that measures the size of the object to be inspected using a signal from the image sensor, the signal from the image sensor is passed through a low-pass filter, and then compared with a constant value to determine a prescribed rising time. The upper wave value is measured after a certain period of time from the specified rise time, and the edge value is generated by comparing a value obtained by dividing this upper wave value in a predetermined proportion with the above-mentioned signal value delayed by a sufficient predetermined time. There is.

In addition, the dimension measuring device according to the second invention in accordance with the above-mentioned object converts light from the object to be inspected into parallel light to a second light converging means having a small diameter using a first light converging means larger than the measurement length. An imaging device is placed on the imaging plane of the object to be examined by combining the first light converging means and the second light converging means, and the signal of the cough imaging device is used to capture the image of the object to be examined. In a dimension measuring device for measuring a size, a signal from the image sensor is passed through a linearizer corresponding to an actual measured value, and the output value is linearly proportional to the measured value.

Here, the first light converging means refers to a concave mirror or a convex lens, and the second light converging means also includes these holes.

[Effect]

In the dimension measuring device according to the first invention, the signal from the image sensor is first passed through a low-pass filter to make a signal that rises smoothly to improve resolution, and then the signal is set to a constant value (for example, about 50% of the signal). The specified start-up time is determined by comparing the

Therefore, the rise of the signal can be detected by this, and the upper wave value of the signal after a certain period of time from this reference time is measured. This makes it possible to measure the magnitude of a signal that has risen sufficiently.

Next, this upper wave value is divided into a predetermined proportion (for example, 50%), and when this is compared with the above signal value delayed for a predetermined time to generate a matching signal that becomes an edge signal, this signal is It is possible to measure the time corresponding to the distance of a constant rise in response to the magnitude of the signal value (i.e. upper wave value) that varies depending on the voltage or other conditions, and thereby accurately detect the object being tested. The edges can be measured.

Next, in the dimension measuring device according to the second aspect of the invention, since the signal from the image sensor is passed through a linearizer, the measured dimension and the output value are proportional.

〔Example〕

Next, embodiments embodying the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.

Here, FIG. 1 is a block diagram of an electric circuit of a dimension measuring device according to an embodiment of the present invention, FIG. 2 is an overall block diagram of the dimension measuring device, and FIG. 3 is a waveform diagram of the dimension measuring device. .

Since the signal from the linear array 16, which is an example of the image sensor shown in FIG. 4, has a step-like shape as shown in FIG. 3(a), it is first smoothed by passing through the low-pass filter 19.

The reference value 21 (
Compare with V,). Here, the reference value is determined to be approximately 50% of the maximum output value, but the present invention is applicable to other values as well.

Next, as shown in FIG. 3(b), the output signal of this primary comparator 20 is transferred to a delay circuit (or timer circuit).
2 for a predetermined period of time (tl). This time (tl
) is set to be a sufficient time for the above signal to rise.

Then, the signal after passing through the low-pass filter 19 with the signal delayed by a certain period of time (tl) is collected by the sample hold circuit 23, and the sample value (v2) is divided in a predetermined proportion by the dark value determining circuit 24 to obtain (v3). obtain.

Here, the darkness value is set to about 50%.

Next, the rise portion of the low-pass filter 19 is delayed from the time when the dark value is determined by the delay circuit 25,
As shown in FIG. 3(C), this signal and the dark value are compared by the secondary comparator 26 to obtain a signal having an edge value as shown in FIG. 3(d).

When the delay time of the delay circuit 25 is subtracted from the time of occurrence of this signal value, the linear array 16 scans the steel plate 1.
Since the time at which the steel plate 17 reaches the end of the plate can be calculated, it is possible to determine the position of the steel plate 17 on the linear array 16. Two of these devices are installed, and an optical device (as shown in the fourth figure) is installed at both ends of the plate. ), the dimensions of the steel plate can be measured.

Note that the above circuit (hereinafter referred to as edge detection circuit), which is a combination of the -order comparator 20, delay circuits 22, 24, sample hold circuit 23, threshold value determination circuit 25, and secondary comparator 26, detects the maximum value of the rising pulse. It can be used for a device that generates an output when the value reaches a certain ratio (<1) to the wave value, and in this case, it will operate effectively even for the maximum value that fluctuates due to voltage fluctuations or ambient conditions.

Furthermore, as shown by the dotted line in FIG. 1, if the lower wave value voltage (V,), which is the base of the pulse, is determined by using another sample and hold circuit 27, the dark value circuit 24 determines (v, - It is also possible to measure the time when v.)×α.

Figure 2 shows a circuit for measuring the dimensions of a steel plate using two of the edge detection circuits described above.
As shown in the figure, a concave mirror 12 is used as an example of a light converging means. Therefore, as explained using FIGS. 6 and 7, an error occurs due to the bending of the concave mirror.

Therefore, the output of the edge detection circuit 28 is temporarily applied to the linearizer 29. If this linearizer is set as an inverse function to the curve m shown in Fig. 7, its output value will be as shown in Fig. 7 n.
As shown in the figure, it becomes a linear value and generates an output proportional to the length.

This linearizer may be one that digitizes the signal once and linearizes it using a memory, or may process the signal as an analog signal using an operational amplifier.

Although the above signal processing has been explained for the case where it is processed as an analog signal, it is also possible to pass the signal from the linear array through a low-pass filter if necessary and then perform AD conversion to control the entire signal using a digital signal. .

〔Effect of the invention〕

In the dimension measuring device according to the first aspect of the invention, even if an image sensor that generates signals in a stepped manner is used, it is possible to obtain an output that exhibits a resolution superior to that of the image sensor.

In addition, in the case of an optical type, the output of the image sensor becomes smooth due to defocus, etc., but even in such a case, it is possible to reliably measure all dimensions of the object to be inspected.

In the second invention, it is possible to correct errors that occur when using a light converging means such as a concave mirror or a convex lens, and to obtain an output that is proportional to the measured dimension.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an electric circuit of a dimension measuring device according to an embodiment of the present invention, FIG. 2 is an overall block diagram of the dimension measuring device, FIG. 3 is a waveform diagram of the dimension measuring device, and FIG. 4 is a waveform diagram of the dimension measuring device. Fig. 5 is a waveform diagram showing the output state from the linear array; Fig. 6 is a schematic diagram of the optical part of the dimension measuring apparatus; Fig. 7 shows the incident angle and the object to be inspected. It is a graph showing the relationship with the dimensions of an object. [Explanation of symbols] 10--Dimension measuring device, 11--1...Lower light source, 12--Concave mirror (first light converging means), 13------ --One plane mirror (second light convergence means), 14...-Filter, 15...----
1 imaging lens, 16 ・-curved linear array, F ・
・・・・・・-Road plate (object to be tested), 19------
-1 low-pass filter, 20 Yamakawa-1 primary comparator, 21------1 reference value, 22--Delay circuit, 23 - Sample hold circuit, 24-
・--Threshold value determination circuit, 25-------Delay circuit, 2
6 ------- Secondary comparator, 27 -------
-Sample hold circuit, 2 g -1111・-Edge detection circuit, 29---111 Linearizer agent Patent attorney Fujio Nakamae Figure 5

Claims (2)

[Claims] (1) Only parallel light from the object to be inspected is made to enter a second light converging means having a small diameter using a first light converging means larger than the measurement length, and the first light converging means and the second light converging means In the dimension measuring device, an imaging device is arranged on the imaging plane of the object to be inspected by combining with a light converging means, and the size of the object to be inspected is measured by the signal of the image sensor. After passing the signal through a low-pass filter, determine a prescribed rising time by comparing it with a constant value, measure an upper wave value after a certain period of time from the prescribed rising time, and divide this upper wave value in a predetermined proportion, A dimension measuring device characterized in that an edge value is generated by comparing the signal values sufficiently delayed by a predetermined time. (2) Only parallel light from the object to be inspected is incident on a second light converging means having a small diameter using a first light converging means larger than the measurement length, and the first light converging means and the second light converging means In the dimension measuring device, an imaging device is arranged on the imaging plane of the object to be inspected by combining with a light converging means, and the size of the object to be inspected is measured by the signal of the image sensor. A dimension measuring device characterized in that the signal is passed through a linearizer corresponding to the actual measured value so that the output value is linearly proportional to the measured value.