JPH0626827A - Three-dimensional measuring instrument - Google Patents

Abstract

PURPOSE:To obtain a noncontact type measuring instrument having high sensitivity and high resolution. CONSTITUTION:An optical system is constituted of a light source 1, a Y-axis displacing means 6, a substance P and a line sensor 3. The light emitted from the light source 1 is applied to the substance P through the Y-axis displacing means 6. The reflected light is received with the line sensor 3. The Y-axis displacing means 6 displaces the light from the light source into the direction of the Y axis of the substance. The substance is displaced in the X-axis direction with an X-axis displacing means 4. The X-Y coordinates of the substance are obtained in this way. The Z-axis coordinate is obtained with the position of the pixel of the line sensor. The line sensor 3 is constituted of the line sensor, Wherein the aspect ratio of unit pixel is large. The line sensor 3 is divided into a plurality of parts in the Y-axis direction. The image is processed with an image processing means 8 for every divided pixel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional measuring apparatus which is preferable for measuring the shape of an object to be inspected in a non-contact state, and is useful for quality control of an object to be measured and FA (Factory Automation). It can be used in the field.

[0002]

2. Description of the Related Art By irradiating an object to be inspected with laser light and capturing the reflected light in a CCD camera or the like, it is attempted to inspect the shape and defects of an object such as a product and thereby control the quality of the product. Has been. Conventionally, a method of using an area sensor for a CCD camera or scanning using a line sensor is known.

[0003]

By the way, the resolution of a general line sensor is about 1/2000, whereas the resolution of an area sensor is about 1/500. As described above, since the area sensor has a lower resolution than the line sensor, there is a problem that the measuring device employing the area sensor cannot perform even the detailed inspection of the inspection object. For example, in the inspection of a lip of an oil seal, which is an oil sealing device, it is necessary to detect even a very small scratch, so that such a low-resolution measuring device cannot be used.

On the other hand, although the line sensor has a high resolution as described above, it has a very low sensitivity, so that there is a problem that sufficient sensitivity cannot be obtained unless the scanning speed is set to a low speed. That is, since the sensitivity is proportional to the light-receiving area, a sensor having a relatively large light-receiving area such as an area sensor has high sensitivity, but the line sensor has a small light-receiving area and thus necessarily has low sensitivity. Therefore, in order to increase the sensitivity, it is necessary to increase the light accumulation time, and as a result, there is a problem that it takes a long time for measurement. If it was attempted to shorten the measurement time, it was necessary to provide a laser device with a high light intensity in order to compensate for the low sensitivity of the line sensor.

In addition to the non-contact type measuring method using the area sensor and the line sensor described above, a contact type measuring method using a contact needle is also known.
Since the load per unit area is large, there is a risk that the inspection object may be damaged, such as scratched. Particularly in oil seals and the like, if the lip is scratched, it will have a very serious effect on the sealability, and therefore the contact type measuring device cannot be used for such an object to be inspected.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a non-contact type measuring apparatus having high sensitivity and high resolution.

[0007]

In order to achieve the above object, a three-dimensional measuring apparatus of the present invention irradiates an object with slit light from a light source and receives the reflected light with a line sensor,
A three-dimensional measuring apparatus for determining a three-dimensional shape of the object, comprising: X-axis displacement means for displacing the object in the X-axis direction.
An X-axis displacement sensor that detects the amount of displacement of the X-axis displacement unit in the X-axis direction, a Y-axis displacement unit that displaces the slit light in the Y-axis direction of the object, and a Y-axis displacement unit in the Y-axis direction. A signal from the Y-axis displacement sensor that detects the amount of displacement, image processing means that performs image processing based on the signal from the line sensor, the X-axis displacement sensor, the Y-axis displacement sensor, and the image processing means. In a three-dimensional measuring device having coordinate reproduction calculation means for reproducing three-dimensional coordinates based on the above, the line sensor is formed of a line sensor having a large aspect ratio of a unit pixel, and the line sensor is arranged in the Y-axis direction. It is characterized in that it is divided into a plurality of parts, and the image processing is executed by the image processing means for each of the divided pixels.

[0008]

The light source, the Y-axis displacement means, the object and the line sensor are constructed as an optical system, and the light emitted from the light source is applied to the object through the Y-axis displacement means, and the reflected light is taken into the line sensor. The Y-axis displacement means displaces the light from the light source in the Y-axis direction of the object, while the X-axis displacement means on which the object is placed displaces the object in the X-axis direction. Thus, the X and Y coordinates of the object can be obtained, and the Z axis coordinates can be obtained from the pixel position of the line sensor.

Here, if the feed pitch of the X-axis displacement means is reduced, the resolution in the X-axis direction is improved, and since the line sensor is used for the resolution in the Z-axis direction, the resolution is higher than that of the area sensor. Become. By using the line sensor, the resolution in the Z-axis direction is improved, and since the sensitivity is high, the scanning time can be shortened.
The resolution in the Y-axis direction decreases. However, in the present invention, the line sensor is divided into a plurality of parts in the Y-axis direction, and the image processing is executed by the image processing means for each of the divided pixels, so that the apparent resolution is improved. be able to.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a three-dimensional measuring apparatus according to an embodiment of the present invention, FIG. 2 (A) is a conceptual diagram showing an image on a YZ plane taken in by an image processing means, and FIG. 2 (B) is a book. FIG. 3 is a front view showing the high-sensitivity line sensor according to the embodiment.
Is an explanatory view for explaining a method of obtaining an output value for each divided pixel in the embodiment, FIG. 4 is a circuit diagram showing a concrete circuit for similarly executing image processing for each divided pixel, and FIG. 5 is a coordinate according to the embodiment. It is explanatory drawing explaining the principle of the coordinate reproduction in a reproduction calculation means.

First, as shown in FIG. 1, the three-dimensional measuring apparatus of the present embodiment comprises a laser generator 1 for irradiating laser light.
a (light source 1), a cylindrical lens 1b (light source 1) that turns the laser light into slit light, a scanning mirror (Y-axis displacement means) 6 that displaces the laser light that has become slit light in the Y-axis direction while reflecting the laser light, It has an object P that is irradiated with laser light and is subjected to measurement such as shape inspection, and a high-sensitivity line sensor 3 that is irradiated with light reflected by the object P, and these constitute a series of optical systems.

Then, the laser light emitted from the laser generator 1a becomes slit light by the cylindrical lens 1b, and the sectional shape of the object P is obtained by the principle of triangulation. The laser light that has become the slit light by the cylindrical lens 1b is scanned by the mirror 6 for scanning.
After being reflected by and reflected by the object P, the reflected light reaches the high-sensitivity line sensor 3, where image processing is executed.

The scanning mirror 6 is rotatably provided, and the slit light scans the object P in the Y-axis direction by this rotation. The rotation amount of the scanning mirror 6 is detected by a Y-axis displacement sensor 7 configured by a rotary encoder or the like, and is output to a coordinate reproduction calculating unit 9 described later as a displacement amount of the object P in the Y-axis direction. The Y-axis displacement means 6 in the present invention
Is not limited to the scanning mirror, and other displacement means may be used. In short, any means can be used as long as it can scan the slit light from the light source 1 onto the object P in the Y-axis direction. Further, the Y-axis displacement sensor 7 is not limited to the rotary encoder, and other means can be used.

On the other hand, the object P is fixed on the X-axis table which is the X-axis displacement means 4, and the X-axis table 4 moves only in the X-axis direction at a predetermined feed pitch. Further, the amount of displacement of the X-axis table 4 in the X-axis direction is detected by an X-axis displacement sensor 5 composed of a linear encoder or the like, and this information is also output to a coordinate reproduction calculation means 9 described later. . In this X-axis table 4, the resolution of the measurement result obtained by the three-dimensional measuring apparatus of the present embodiment is improved as the feed pitch is made smaller. Therefore, the feed pitch is set according to the measurement accuracy of the object P to be measured. It is preferable to set it. The X-axis displacement means 4 of the present invention is
Other means can be used without being limited to the X-axis table described above, and the X-axis displacement sensor 5 is not limited to the linear encoder at all.

The line sensor 3 according to this embodiment has a structure shown in FIG.
As shown in (B), a line sensor in which an aspect ratio of a unit pixel (hereinafter, referred to as an aspect ratio) is relatively large is adopted. A unit pixel of a general line sensor has a length (line direction) of about 13 μm and a width (width direction) of about 13 μm, and an aspect ratio of about 1: 1. On the other hand, in the line sensor 3 according to the present embodiment, the vertical (line direction) is 25 μ, and the horizontal (width direction) is 25 mm (250
A line sensor having a size of about 0 μm is used, and the aspect ratio is approximately 1: 100.

Various vertical and horizontal dimensions are not limited to the above-mentioned values, and various line sensors can be used. However, a line sensor having a large aspect ratio has a large light receiving area and therefore a high sensitivity sensor. Becomes That is, since the sensitivity is improved as compared with a general line sensor, the light accumulation time can be shortened, and as a result, the time required for measurement can be shortened. Moreover,
The Z-axis direction (line direction) has a higher resolution than the area sensor. For example, if the area sensor is 540
The resolution when it is composed of × 400 pixels is 1/5
40, the high-sensitivity line sensor 3 of this embodiment
If it consists of 2000 pixels, its resolution is 1/20
00, it is possible to obtain a resolution several times higher than that of the area sensor. As a result, the measurement accuracy can be improved, and it can be applied to inspection of fine scratches on the oil seal.

However, since the high-sensitivity line sensor 3 of this embodiment is large in the lateral direction (width direction), the resolution in the width direction is lower than that of a general line sensor. Therefore, in the present invention, this drawback, namely,
In order to compensate for the decrease in resolution in the width direction, pixel division, that is, a method of apparently dividing pixels in the width direction is adopted,
The image processing means 8 including the arithmetic circuit shown in FIG.

The method of capturing image information by this pixel division is as follows. That is, the output value from one pixel does not change at all, but before storing this output value in the image memory of the image processing means, it is calculated into a numerical value as if one pixel was divided.

Specifically, first, as shown in FIG. 3A, the number of pixels of the high-sensitivity line sensor 3 is m, the number of divisions per pixel is n, and the j-th pixel of the i-th pixel. The output value from the high-sensitivity line sensor at the measurement position is y _{i, j} , and the output value of the divided pixel of the i-th pixel is a _{i, k} . Here, the j-th measurement means the number of times of capturing an image when the scanning mirror 6 is rotated at a predetermined pitch. Then, since the output value from one pixel is the sum of the output values of the divided pixels,

[0020]

[Equation 1]

Subtracting the above equations (1) and (2),

[0022]

[Equation 2]

If the initial value a _{i, j} of the divided pixels is given _, y _{i, j + 1} −y _{i, j} which means the pixel difference.
Can be obtained by measurement, so that the output values a _{i, j + n} of the divided pixels can be calculated based on the equation (3). Therefore, when setting the initial values of the divided pixels, if a _{i, 1} = a _{i, 2} = ... = a _{i, n} = 0, that is, if the image density is zero,

[0024]

[Equation 3]

Thus, the output values of the divided pixels can be obtained by a simple calculation if only the initial value is set. Therefore, the arithmetic circuit for obtaining the output value of this divided pixel can be configured by hardware. Also, regarding the setting of this initial value, since the output value of the image processing is black and white contrast, it is sufficient to set an appropriate initial value, and if the calculated result is an inappropriate initial value. Even if it becomes clear, the initial position can be easily reset. For example, it is possible to scan a reference plate in which the shade (brightness) of black and white is fixed in advance and set the initial value based on the value at this time.

FIG. 4 is a circuit diagram in which the above-described calculation for obtaining the output value of the divided pixel is configured by hardware, and the output value from the high-sensitivity line sensor 3 is the A / D converter 10.
After being converted to a digital value by, the line buffer 1
Are sequentially transmitted to the line buffer 2. Then, information is output from the respective line buffers of the line buffer 1 and the line buffer 2 to the subtraction circuit 11, and the subtraction circuit 11 outputs y _{i, j + 1} −y _{i, on} the right side of the above equation (3) _. ask for _j . The calculation result from the subtraction circuit 11 is then output to the addition circuit 12, and the appropriate initial value a output from the image memory 13 is output to the addition circuit 12.
_{Take i, j} and add them. That is, the calculation of Expression (3) is executed. Then, the calculation result is output to the image memory 13 and stored in the corresponding address.

By giving an appropriate initial value, the operation result at the beginning of the operation will be an appropriate value, but the relative value of each operation result will be a result indicating the shade of the image. Therefore, even if the final measurement value is relative, it can be obtained in an extremely high resolution state.

In this way, by dividing the high-sensitivity line sensor 3 in the width direction (Y-axis direction) into a plurality of divided pixels, it is equivalent to a state in which a plurality of general line sensors are arranged side by side in the width direction. Become. As a result, it is possible to obtain a sensor having both the advantage of the high sensitivity of the high sensitivity line sensor and the advantage of the high resolution of the general line sensor.

Next, a method of reproducing the three-dimensional coordinates of the object P based on the information from the X-axis displacement sensor 5, the Y-axis displacement sensor 7 and the image processing means 8 described above will be described. In the present invention, the reproduction of the three-dimensional coordinates is obtained by the coordinate reproduction calculation means 9 using the principle of triangulation in surveying. That is, as shown in FIG. 5A, in the optical system in which the light from the light source is reflected by the object P and is received by the light receiving element (line sensor), the distance between the light source and the lens in the XY plane (baseline Length) is D, the focal length of the lens is f, the position of the spot light on the light receiving element is Xa, Ya, and the angle formed by the trajectory of the light with the XY plane is φb, φ.
a, θb and θa are the angles of the trajectory of the light on the XY plane.
Then, the three-dimensional coordinates (X, Y, Z) of the object P to be obtained
Is

[0030]

[Equation 4]

[0031]

[Equation 5]

In this way, from the set values f, D, θb and the measured values Xa, Ya, the equations (14), (15), (1)
Based on 6), the three-dimensional coordinates (X, Y, Z) of the object P can be calculated. Since the coordinates (X, Y, Z) obtained from this calculation result represent the three-dimensional coordinates themselves of the object P, if this is applied as an inspection device for pass / fail judgment based on a certain reference value, The three-dimensional measuring device of the invention can be applied as a high-speed and highly accurate inspection device.

The three-dimensional measuring apparatus of the present invention is not limited to the above-mentioned embodiment and can be variously modified. Further, the method using the three-dimensional measuring apparatus of the present invention is not limited to the inspection apparatus and can be applied to various other fields.

[0034]

According to the three-dimensional measuring apparatus of the present invention, the line sensor is composed of a line sensor having a large unit pixel aspect ratio, and the line sensor is divided into a plurality of parts in the Y-axis direction. Since the image processing is executed by the image processing means for each time, the sensitivity is increased and the scanning time can be shortened. Further, the resolution of pixels is increased, and as a result, it can be used as a fine inspection apparatus.

Furthermore, since a simple algorithm is used to execute the pixel division calculation, this calculation process can be implemented by hardware, and the calculation time and cost can be shortened.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a three-dimensional measuring apparatus according to an embodiment of the present invention.

FIG. 2A is a conceptual diagram showing an image on a YZ plane taken in by an image processing means, and FIG. 2B is a front view showing a high-sensitivity line sensor according to the present embodiment.

FIG. 3 is an explanatory diagram illustrating a method of obtaining an output value for each divided pixel in the embodiment.

FIG. 4 is a circuit diagram showing a specific circuit that similarly executes image processing for each divided pixel.

FIG. 5 is an explanatory diagram illustrating the principle of coordinate reproduction in the coordinate reproduction calculation means according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source 1a ... Laser generator 1b ... Cylindrical lens 3 ... High-sensitivity line sensor 4 ... X-axis table (X-axis displacement means) 5 ... X-axis displacement sensor 6 ... Scanning mirror (Y-axis displacement means) 7 ... Y-axis Displacement sensor 8 ... Image processing means 9 ... Coordinate reproduction calculation means 10 ... A / D converter 11 ... Subtraction circuit 12 ... Addition circuit 13 ... Image memory P ... Object

Claims (1)

[Claims] 1. An object (P) is irradiated with slit light from a light source (1), and the reflected light is received by a line sensor (3).
A three-dimensional measuring device for determining a three-dimensional shape of the object (P), comprising: an X-axis displacement means (4) for displacing the object (P) in the X-axis direction; and an X-axis displacement means (4) of the X-axis displacement means (4). An X-axis displacement sensor (5) that detects the amount of axial displacement, a Y-axis displacement unit (6) that displaces the slit light in the Y-axis direction of the object (P), and the Y-axis displacement unit (6). Y-axis displacement sensor (7) for detecting the amount of displacement in the Y-axis direction, image processing means (8) for performing image processing based on the signal from the line sensor (3), and the X-axis displacement sensor ( 5), a Y-axis displacement sensor (7), and coordinate reproduction calculation means (9) for executing reproduction of three-dimensional coordinates based on a signal from the image processing means (8), The line sensor (3) is a line with a large unit pixel aspect ratio. A three-dimensional structure comprising a sensor, the line sensor (3) is divided into a plurality in the Y-axis direction, and image processing is executed by the image processing means (8) for each of the divided pixels. Measuring device.