JP3281986B2 - Image measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image measuring device,
The present invention relates to an image measuring device that measures a measurement target by irradiating the measurement target with parallel light.

[0002]

2. Description of the Related Art In a case where a product is automatically inspected in an automation line, it is indispensable to automatically extract information of the product. Therefore, a CCD line sensor or the like in which elements are arranged one-dimensionally is used. The used image measuring device is widely used. This type of measuring device includes a halogen lamp,
A light emitting unit having a light source such as an LED or a laser diode and a light emitting lens for converting light from the light source into parallel light,
A CCD line sensor that receives light from the light emitting unit, and a CCD
A signal processing circuit for processing the analog output of the line sensor to obtain digital data corresponding to the amount of received light for each pixel; and an arithmetic processing circuit for sequentially comparing the digital data with threshold data to measure a product. It is mainly composed of The arithmetic processing circuit must sequentially compare the digital data with the threshold data, determine the edge of the change from light to dark and from dark to light, and measure the number of edges and the dimension between the edges. Then, the shape, position, dimensions, and number of products are measured.

When measuring the outer diameter of a product, for example, with this type of measuring device, the product is arranged at a position that blocks a part of the parallel rays from the light projecting section. At this time, as for the output of the CCD line sensor, the output of the part shaded by the product is lower than that of the other parts. Since the width of the shaded portion corresponds to the outer diameter of the product, the outer diameter of the product can be known by measuring the width.

When a CCD line sensor is used, shading correction for correcting unevenness in sensitivity of each element, unevenness in illuminance of a light source, or the like may be performed. In shading correction, the reciprocal of the received light amount of each element when no product is placed between them is stored as a correction value, and the correction is performed by multiplying the received light amount at that time by the correction value when measuring the product. Do.

[0005]

In the above-mentioned conventional configuration using a halogen lamp or an LED as a light source, the measurement accuracy can be improved by shading correction.
It is difficult to obtain perfect parallel light. For this reason, in order to perform highly accurate measurement, it is necessary to shorten the distance between the light emitting unit and the light receiving unit.

The above-described conventional configuration using a laser light source as a light source has an advantage that parallel light can be easily obtained. However, the laser beam forms a ripple-rich waveform due to the influence of a far field pattern, interference fringes, and the like. Therefore, when the output of each cell of this CCD is taken out in time series using CDD on the light receiving element side, a signal in which a signal waveform having a high frequency and a small amplitude is superimposed on a signal waveform having a low frequency and a large amplitude is obtained. can get. If shading correction is performed on such a light receiving result, the light receiving position may be shifted from the light projecting position during measurement due to the influence of vibration or the like, and the high frequency ripple having a small amplitude may be corrected in a direction to increase. Yes, the light receiving result becomes unstable and the error is amplified. That is, when a laser light source is used, the accuracy cannot always be improved by shading correction.

An object of the present invention is to enable stable and accurate measurement.

[0008]

An image measuring apparatus according to the present invention is an apparatus for measuring an object by irradiating the object with parallel light. This device includes an irradiating unit, a light receiving unit, an extracting unit, and a measuring unit. The irradiating means irradiates the object to be measured with parallel light. The light receiving means has a plurality of light receiving elements arranged corresponding to the parallel light. The extracting means extracts a light receiving result in a predetermined frequency band from signals extracted in time series from a plurality of light receiving elements in a state where no measurement target is arranged between the irradiation means and the light receiving means. The measurement means measures the measurement target based on the extraction result of the extraction means and the light reception result of the light receiving means in a state where the measurement target is arranged therebetween.

[0009]

In the image measuring apparatus according to the present invention, first, the extraction means determines a predetermined frequency from signals extracted in time series from a plurality of light receiving elements in a state where the object to be measured is not arranged between the irradiation means and the light receiving means. The reception result of the band is extracted. Then, the measuring unit measures the measurement target based on the extraction result and the light reception result in a state where the measurement target is arranged therebetween.

In this case, highly accurate detection can be performed even if the light transmission and reception are separated. Moreover, the light receiving result of the unnecessary frequency band is extracted by the extracting means, and the measurement target can be measured while performing the correction based on the extracted result, so that the measuring accuracy is further improved.

[0011]

FIG. 1 shows an image measuring apparatus according to an embodiment of the present invention. In the figure, the image measuring device mainly includes a light projecting unit 1 and a light receiving unit 2 which are arranged at an interval at which a measurement object M can be arranged. The light projecting unit 1 includes a laser diode 3 and a light projecting lens 4 that converts the laser light emitted from the laser diode 3 into parallel light. The light receiving unit 2 receives a parallel light from the light projecting unit 1, a CCD line sensor 5, an amplifier 6 that processes and amplifies an analog output of the sensor 5, and outputs an amplified output to one of two terminals A and B. An analog switch 7; a low-pass filter 8 connected to the terminal B; an A / D converter 9 for A / D-converting either the output of the low-pass filter 8 or the output of the terminal A; It has a memory A10 for storing, a memory B12 for storing a correction value, and a CPU 11 for performing a measurement process.

The CPU 11 determines the connection state of the analog switch 7. When the analog switch 7 is switched to the terminal B side, the CPU 11
Is read out and the reciprocal thereof is stored in the memory B1.
2 is stored as a correction value. Laser diode 3 and C
The PU 11 is connected to a main body control unit (not shown). The main body control unit displays the measurement result and gives a selection signal of the analog switch 7, a drive signal of the laser diode 3, and the like to the measurement device.

Next, the operation of the above embodiment will be described. First, initialization is performed in step S1 of FIG. At the time of initial setting, the contents of the memories A10 and B12 are all cleared. In step S2, the analog switch 7
Is switched to the terminal A or the terminal B. Here, when the correction value is input, the analog switch 7 is switched to the terminal B. Then, the laser diode 3 and the CCD line sensor 5 are driven without disposing the measurement object M between the light projecting unit 1 and the light receiving unit 2.
At this time, the received light data that has passed through the low-pass filter 8 is AD-converted by the A / D converter 9 and stored in the memory A10. For example, when light reception data as shown in FIG. 3 is obtained, only low frequency light reception data having a large amplitude shown by a thick solid line in FIG. 3 passes through the low-pass filter 8 and is A / D converted and stored in the memory A10. That is, the low-pass filter 8
Extracts only low frequency components of the received light data.

In step S3, the extracted light reception data stored in the memory A10 is read. In step S4, the reciprocal of the extracted light reception data is calculated. In step S5, the reciprocal of the calculated extracted data is stored in the memory B12 as a correction value. Upon completion of the process in the step S5, the process returns to the step S2. On the other hand, if it is determined in step S2 that the analog switch has been switched to the terminal A, the process proceeds to step S6. When the measurement object M is arranged between the light projecting unit 1 and the light receiving unit 2 and measurement is performed, the analog switch 7 is switched to the terminal A. In step S6, the received light data in the memory A10 is read. Here, the memory A1
In 0, a value obtained by A / D converting the light receiving result as it is is stored. That is, the measurement result is stored as it is.
In step S7, the correction value stored in the memory B12 is read. In step S8, the correction is performed by multiplying the correction value by the received light data read from the memory A. Note that, at the time of this correction, as described above, correction is not performed using ripples with small high-frequency amplitudes. In step S9, the outer diameter of the measured object M is calculated based on the result of the multiplication, and is output to the main body control unit. When these processes are completed, the process returns to the step S2.

Here, only the data of the reciprocal of the low frequency component is stored as a correction value in the memory B12, and the high frequency component is not stored. Therefore, the measured object M
When the received light data is corrected in the case where is not arranged, the high-frequency component ripple remains as shown in FIG. However, since the correction by the high frequency component is not performed, even if the position shift between the light projecting unit 1 and the light receiving unit 2 occurs,
The amplification of the error due to the correction does not occur. Therefore, stable and accurate measurement can be performed even when coherent light such as laser light is used.

[Other Embodiments] (a) In the above-described embodiment, a laser diode is used as a light source.
A laser or other laser irradiation means may be used. (B) Instead of a CCD line sensor, a MOS image sensor or various image pickup tubes may be used. (C) In the above embodiment, the low-pass filter is used as the extracting means, but a low-frequency component may be calculated and extracted by a microcomputer.

[0017]

According to the optical dimension measuring apparatus of the present invention,
The measurement is performed using the parallel light, and only the light receiving result in a predetermined frequency band is extracted by the extracting means, and the measured light receiving result can be corrected based on the extracted result, so that stable and accurate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of an image measuring device according to an embodiment of the present invention.

FIG. 2 is a control flowchart thereof.

FIG. 3 is a waveform chart showing an example of a light reception result.

FIG. 4 is a waveform chart showing an example of a correction result.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light emitting part 2 light receiving part 3 laser diode 5 CCD line sensor 8 low-pass filter 10 memory A 11 CPU 12 memory B

Claims (1)

(57) [Claims] 1. An irradiating means for irradiating a parallel light to an object to be measured, a light receiving means having a plurality of light receiving elements arranged corresponding to the parallel light, and the measuring means between the irradiating means and the light receiving means. Extracting means for extracting a light receiving result of a predetermined frequency band from signals extracted in time series from the plurality of light receiving elements in a state where no object is arranged; and an extraction result of the extracting means and the measuring object arranged between the extracting means. An image measurement device comprising: a measurement unit configured to measure the measurement target based on a light reception result of the light reception unit in a state.