JPS593304A - Measuring method of size - Google Patents

Abstract

PURPOSE:To measure exactly the size of an object to be measured in accordance with the distribution of the distortion factor of a lens system which is beforehand calculated by drawing out the output pulses corresponding to a bright part from a solid-state image sensing element and counting the same. CONSTITUTION:The image of an object 1 to be measured is formed on a solid- state image sensing element 3, which outputs pulses in accordance with the bright part where there is no image of the object to be measured. On the other hand, the sample of a known size is formed, and the image forming position thereof is changed continuously, then the effective diameter X0 in the photodetection part of the solid-state image sensing element and the distribution of the distortion factor of the lens system are calculated. Thereafter, the sizes X1, X2 corresponding to the bright part are calculated from the output pulses of the time when the object 1 is formed an image on the element 3. The sizes X1, X2 corresponding to the bright parts 1, 2 are subtracted from the above-described effective diameter X0, whereby the size X3 of the object 1 is known.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dimension measuring method for measuring the dimensions of an object to be measured by forming an image of the object on the surface of a solid-state image sensor through a lens system.

In recent years, a non-contact dimension measurement method using a solid-state image sensor as described above has been used to continuously measure the diameter of a steel rod or the like at high speed.

Conventionally, in this type of measurement method, in order to minimize the influence of lens system distortion, a sample of known dimensions is measured in advance, and the relationship between the number of output pulses of the solid-state image sensor and the sample dimensions is calculated. By calculating a constant distortion rate from the equation and using it as a correction coefficient, the dimensions of the object to be measured are obtained from the number of output pulses of the solid-state image sensor.

However, since the distortion rate of a lens system is often not uniform even within the effective diameter range, it is inappropriate to obtain the dimensions of the object to be measured from the number of output pulses of a solid-state image sensor based on the above-mentioned constant distortion rate. There is. For example, there is a problem in that when the object to be measured is imaged at the center of the light-receiving section of a solid-state image sensor, the dimensional measurement error is small, but conversely, when the object is imaged around the light-receiving section, the error becomes large. In addition, with conventional methods, it was not possible to determine the position where the object to be measured was imaged on the solid-state image sensor surface, so even if the distortion rate distribution of the lens system was calculated, It was not possible to calculate the exact dimensions.

Therefore, in order to further reduce measurement errors in the conventional method, it is necessary to strictly design the lens system, adjust each lens as a lens, and align each lens after the device is installed. However, these tasks are extremely complicated and difficult.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a dimension measuring method that can relatively accurately measure dimensions without making strict adjustments to the lens system or the like.

To this end, the dimension measurement method according to the present invention focuses a sample of known dimensions on the solid-state image sensor surface through a lens system, and continuously changes the imaging position of the sample. The effective diameter of the light-receiving part and the distortion rate distribution of the lens system are calculated, and then, when the object to be measured is imaged on the solid-state image sensor surface, an output pulse corresponding to the bright area is extracted from the solid-state image sensor. The present invention is characterized in that the dimensions of the object to be measured are calculated by counting, calculating the dimensions of the bright portion based on the counted value and the distribution of the strain rate, and subtracting the dimension of the bright portion from the effective diameter.

FIG. 1 is an explanatory diagram for explaining the principle of the method according to the present invention. In the figure, ] is the object to be measured, 2 is the lens system,
3 is a solid-state image sensor. The solid-state image sensor 3 has a light receiving section in which, for example, 50 pixels are arranged in a row, and outputs pulses corresponding to bright areas that are the areas receiving light. No pulses are output for the dark areas where the image is displayed. Further, XO in the figure is the effective diameter of the light receiving section, which is the dimension of the object to be measured when an image is formed on the entire surface of the light receiving section.

On the other hand, a sample of known dimensions is imaged, and the imaging position is continuously changed to calculate the effective diameter XO of the light-receiving section of the solid-state image sensor and the distortion rate distribution of the lens system.

The distortion rate distribution of this lens system is stored in relation to, for example, the output pulses and dimensions of the solid-state image sensor 3 shown in the figure.

Thereafter, in the output signal when the object to be measured 1 is imaged on the solid-state image pickup device 3, the number of output pulses corresponding to the bright portion] and the bright portion 2 are counted.

Assuming that the count values are 81 and S2, dimensions XI and X2 corresponding to bright portions 1 and 2 are calculated from the relationship between the output pulse and the dimensions shown in the figure. Then, by subtracting the dimensions x1 and x2 corresponding to the bright area [2] from the effective diameter XO, the dimension X3 of the object to be measured can be determined.

An embodiment of the dimension measuring method according to the present invention will be described below.

FIG. 2 shows an example of a measuring device using the method according to the present invention.
FIG. 3 is a diagram of its operating waveforms.

In FIG. 2, 1/ is a light source, 2 is a lens system, and 3 is a solid-state image sensor including, for example, a charge-coupled device (CCD).
This solid-state image sensor 3 has 204 pixels of 10 μm each.
It has eight light receiving sections arranged in rows. 4 is an object to be measured, for example, a steel material.

On the other hand, 5 is a counting circuit that counts the number of output pulses of the solid-state image sensor, 6 is a so-called retrigger type monostable multivibrator, 7 is a delay circuit, 8 is a monostable multivibrator, and 9 is the output signal of the counting circuit 5. A latch circuit for latching .]Oa and 10b are interfaces, 11 is an arithmetic processing section, 12 is a storage circuit, and 13 is a display device.

First, instead of the steel material 4 that is the object to be measured, a sample 4' of known dimensions is placed at a predetermined position, and parallel light is irradiated onto it from the light source 1' via the lens system 2. As a result, the sample 4' is imaged on the light receiving portion of the solid-state image sensor 3. This solid-state image sensor 3 is driven by, for example, a drive circuit including a crystal oscillator (not shown) or the like. Therefore, the solid-state image sensor 3 is
A signal as shown in 11 is output. This output signal is given to a counting circuit 5 and a monostable multivibrator 6, and the counting circuit 5 counts the number of pulses, and the monostable multivibrator 6 determines whether the output pulses are continuous or not. The signals are clearly distinguished and a read signal as shown in FIG. 3(C) is output.

That is, in the read signal shown in Figure 31), rHJ
The area corresponding to is the bright area of the light receiving part of the solid-state image sensor 3, and the area rLJ is the dark area. This read signal is given to the latch circuit 9 as a control signal, and after being delayed by the delay circuit 7, it is sent to the monostable multivibrator 8.
given to. The monostable multivibrator 8 provides a counter clear signal as shown in FIG. 3) to the counting circuit 5 as a control signal.

Therefore, after the counting circuit 5 counts the number of output pulses corresponding to the bright portion of the solid-state image sensor 3, the latch circuit 9 latches the count output at the fall of the read signal. Then, the latch circuit 9 holds it until the next fall of the read signal. On the other hand, the count output of the output pulse corresponding to the bright portion is latched and then erased by a counter clear signal. Then, the counting circuit 5 starts counting output pulses corresponding to the next bright area.

The count value of the output signal of the solid-state image sensor 3 counted in this manner is given to the arithmetic processing unit 11 via the interface 102I together with the gate signal shown in FIG. 3(A).

Then, when the sample 4' is moved and its imaging position is continuously changed, the arithmetic processing unit 11 calculates the count value of the output signal of the solid-state image sensor 3 at each imaging position and the count value of the output signal of the solid-state image sensor 3 at each imaging position. Based on the dimensions of the sample 4', the effective diameter of the light receiving portion of the solid-state image pickup device 3 and the distortion rate distribution of the lens system 2 are calculated and stored in the storage circuit 121. In other words, even if the sample 4' with constant dimensions is moved and its imaging position is changed, if the lens system is undistorted, the sum of the output pulses corresponding to the bright area will remain constant, or if the lens system is distorted. In the case of a system, the number of output pulses varies depending on the imaging position. Therefore, sample 4
By moving the imaging position of ' over the entire surface of the light receiving section of the solid-state image sensor 3 and looking at the change in the count value of the output pulses, it is possible to know the distortion rate distribution of the lens system and the effective diameter of the light receiving section.

Then, the dimensions of the steel material 4 are measured.

At this time, the output pulses of the solid-state image sensor 3 are counted in the same manner as in the case of the sample 4' described above. Therefore, as shown in FIG. 1, for example, as shown in FIG. Dimensions X1 and X2 corresponding to bright portion 1 and bright portion 2 are calculated based on the ratio distribution. Then, by subtracting the dimensions X1 and X2 from the effective diameter XO stored in the memory circuit 12, the dimension X3 of the steel material 4 is calculated. and,
The calculated dimensions of the steel material 4 are displayed, for example, on the display 13 via the interface Job.

As is clear from the above description of an embodiment of the present invention, the dimension measurement method according to the present invention extracts output pulses corresponding to bright areas from the solid-state image sensor and counts them, so that the Since the position where the object is imaged can be known, the correct dimensions of the object to be measured can be determined based on the distribution of the distortion factor of the lens system calculated in advance.

Therefore, if the method according to the present invention is used, relatively accurate dimension measurements can be made without making strict adjustments to the lens system, so the present invention is extremely useful in practical use.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining the principle of the method according to the present invention, FIG. 2 is an example of a dimension measuring device using the method according to the present invention, and FIG. 3 is an operational waveform diagram thereof. 2... Lens system, 3... Solid-state image sensor, 4... Steel material, 5... Counting circuit, 6.8... Monostable multivibrator, 7... Delay circuit, 9... latch circuit, 1
0a, 10b...Interface, 11...Arithmetic processing unit, 12...Storage circuit, 13...Display device. Patent applicant Koji Onishi, patent attorney representing Shimadzu Corporation

Claims (1)

[Claims] By focusing a sample with known dimensions on the solid-state image sensor surface through a lens system and continuously changing the imaging position of the sample, the effective diameter of the light-receiving section of the solid-state image sensor and the distortion rate distribution of the lens system can be determined. Then, when the object to be measured is imaged on the surface of the solid-state image sensor, output pulses corresponding to bright areas are extracted from the solid-state image sensor and counted, and the counted value and the distribution of the distortion rate are calculated. A dimension measuring method, comprising: calculating the dimensions of a bright part based on the effective diameter, and calculating the dimensions of the object to be measured by subtracting the dimension of the bright part from the effective diameter.