JPH10185534A - Instrument and method for measuring shape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the shape of a transparent body with accuracy even when both front reflection and rear reflection occur and, at the same time, to simultaneously measure the front and rear surfaces of the transparent body by picking up the image of reflected light from at least either the front surface or rear surface of the transparent body and processing the image. SOLUTION: Light from a light source 1 is passed through a slit 2, condensed through a lens 3, and projected upon a transparent sample 4. The image of reflected light from the sample 4 is formed in a lens 5 and picked up with a TV camera 6. An A/D converter 8 digitizes the TV signal of the camera 6 and a picture processor 9 measures the shape of the sample 4 from the digital data. Because of refraction in the sample 4, a deviation is produced between reflected light 12 from the front surface of the sample 4 and reflected light 13 from the rear surface of the sample 4. Therefore, the image 121 of the reflected light from the front surface and the image 131 of the reflected light from the rear surface are picked up with the camera 6 with a deviation between the images 121 and 131. Since the reflected light rays from the front and rear surfaces can be detected separately when the deviation amount is increased and the slit 2 is made narrower in width, high-contrast video signals can be obtained. In addition, it becomes possible to stably catch the reflected light from the rear surface only.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape measuring device for determining the shape of a transparent material such as plastic or glass or a product using the same.

[0002]

2. Description of the Related Art In recent years, manufacturing techniques such as molding and laser processing have been improved, and it has become possible to mass-produce resin products of various shapes with a submicron shape accuracy. For this reason, the measurement accuracy required for evaluating the shape of a processed product is increasing. Conventionally, for measurement of such a minute shape, it has been general to use a dimension measuring machine that enlarges and projects with a microscope and measures the shape by image processing.

[0003]

However, in the optical system of the above-mentioned conventional dimension measuring device, coaxial epi-illumination or fiber illumination is generally used as illumination. Illumination light from the coaxial epi-illumination 34 shown in FIG. 7 includes reflected light even on the front surface of the measurement target and reflected light from the back surface. In this case, when measuring the shape of the transparent body, an image in which the reflected light on the surface to be measured and the reflected light on the back surface are overlapped is obtained, so when measuring the shape of the front surface, the unevenness of the reflected light on the back surface is measured. This causes errors, and conversely, when it is desired to measure the shape of the back surface, there is a problem that unevenness of reflected light on the front surface is superimposed as an error.

Accordingly, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to measure the shape of a transparent body with high accuracy even if there is reflection on the front surface and reflection on the back surface. An object of the present invention is to provide a shape measuring device and a method capable of simultaneously measuring the front surface and the back surface of a measurement object.

Another object of the present invention is to facilitate separation of reflected light on the front surface and reflected light on the back surface.
An object of the present invention is to provide a shape measuring device and a method capable of improving the shape measuring accuracy of the back surface.

[0006]

Means for Solving the Problems The above-mentioned problems are solved,
In order to achieve the object, a shape measuring device according to the present invention is a shape measuring device for measuring a shape of a transparent body, and a light source for irradiating the transparent body with light, and a light from the light source. A light-shielding means for shaping the light into a predetermined pattern, an optical system for condensing light passing through the light-shielding means, light transmitted through the optical system and reflected on the surface of the transparent body, and It is characterized by comprising a television camera that captures at least one of the light reflected on the back of the body, and image processing means that performs image processing on an image obtained by the television camera.

Further, in the shape measuring apparatus according to the present invention, the position of the light source and the position of the light shielding means are adjusted so that the light passing through the light shielding means is incident on the surface of the transparent body at a predetermined angle. It is characterized by being set.

Further, in the shape measuring apparatus according to the present invention, the light shielding means is arranged at a position conjugate with a focal point of the optical system.

Further, in the shape measuring apparatus according to the present invention, the transparent body is arranged so that the front surface and the back surface are located near a focal position of the optical system.

Further, in the shape measuring apparatus according to the present invention, the depth of field of the optical system is set to be larger than the distance between the front surface and the back surface of the transparent body.

Further, in the shape measuring apparatus according to the present invention, the light shielding means is a light shielding plate having a slit-shaped opening.

Further, in the shape measuring device according to the present invention, the light shielding means is a knife edge.

Further, the shape measuring apparatus according to the present invention is further characterized by further comprising a moving means for moving the transparent body with respect to the optical system.

The shape measuring method according to the present invention is a shape measuring method for measuring the shape of a transparent body, wherein light irradiated from a light source is formed into a predetermined pattern shape by a light shielding means, and the shape is measured. The emitted light is condensed by an optical system and irradiated on the transparent body, and at least one of the light reflected on the surface of the transparent body and the light reflected on the back side of the transparent body is imaged by a television camera. The shape of the transparent body is measured by performing image processing on an image obtained by the television camera.

Further, in the shape measuring method according to the present invention, the position of the light source and the position of the light shielding means are adjusted so that the light passing through the light shielding means is incident on the surface of the transparent body at a predetermined angle. It is characterized by setting.

Further, in the shape measuring method according to the present invention, the light shielding means is arranged at a position conjugate with a focal point of the optical system.

Further, in the shape measuring method according to the present invention, the transparent body is arranged so that the front surface and the back surface are located near a focal position of the optical system.

In the shape measuring method according to the present invention, the depth of field of the optical system is set to be larger than the distance between the front surface and the back surface of the transparent body.

The shape measuring method according to claim 9, wherein in the shape measuring method according to the present invention, a light shielding plate having a slit-shaped opening is used as the light shielding means.

Further, in the shape measuring method according to the present invention, a knife edge is used as the light shielding means.

Further, the shape measuring method according to the present invention is characterized in that the shape of the transparent body is continuously measured by moving the transparent body with respect to the optical system.

[0022]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
It is a block diagram showing the composition of the shape measuring device concerning an embodiment.

In FIG. 1, reference numeral 1 denotes a lamp as a light source, 2 denotes a slit for shaping light from the light source 1 into a vertically long shape, 3 denotes an optical lens for condensing light transmitted through the slit 2, and 4 denotes a measurement. A transparent sample, 5 is an imaging optical lens whose optical axis is set in the direction of regular reflection of projection light, 6 is a television camera for taking an image formed by the lens 5, and 7 is a sample 4.
Is moved in the direction of arrow B, and 8 is the TV camera 6
An AD converter for digitizing a television signal from a computer; 9, an image processing device for obtaining the shape of the sample 4 from digital data output from the AD converter 8; 11 is an image processing device 9
Is an image monitor for viewing the image processed in step (a).

In FIG. 1, the slit 2 is arranged at a position conjugate with the focal point of the condensing lens 3, and the image of the slit 2 is projected on the measuring object 4. The regular reflection image at this time is captured by the television camera 6. Note that a lens having a sufficient depth of field as compared to the distance between the front surface and the back surface of the measurement target 4 is used as the lens 3. Since the measurement object 4 is a transparent body, the reflected light is divided into front surface reflected light 12 and back surface reflected light 13 as shown in FIG. When the illumination light is incident at an angle α, the specularly reflected light (surface reflected light) is also reflected at the angle α, but the light refracted at the surface proceeds inside the transparent body 4 having the refractive index n, and according to Snell's law. Therefore, the light is refracted at an angle β that satisfies the relationship of n · sin β = sin α. This ray has a thickness d
The light is reflected on the back surface of the transparent body 4 and refracted on the front surface again, and becomes reflected light on the back surface. At this time, the light ray reflected on the front surface and the light ray reflected on the back surface are shifted as shown in FIG. The shift amount x is represented by x = 2d · cosα · tanβ. The image of the television camera 6 at this time is shown in FIG.
become that way. The reflected light 121 from the front surface and the reflected light 131 from the back surface generate an image of slit light at a position shifted by the shift amount x. At this time, measurement is performed so that the front surface reflected light and the back surface reflected light can be separated, in other words, the shift amount x is sufficiently large compared to the width of the front surface reflected light image 121 and the width of the back surface reflected light image 131. The incident angle of the illumination light is set for the thickness d of the object 4 according to the above equation.
Increasing the angle increases the shift amount x. Also, the width of the slit 2 is made sufficiently small so that the width of the images 121 and 131 does not become large. By doing so, in the measurement of the back surface of the transparent body, the reflected light from the front surface and the reflected light from the back surface can be detected separately, so that a video signal with high contrast can be obtained. Further, it is possible to stably capture only the reflected light from the back surface irrespective of the unevenness of the surface reflection.

Here, in the case where the continuous portion of the back surface of the measurement object 4 is only on the near side as shown in FIG. 1, consider the case of measuring the shape of the root portion 50 along the direction of arrow B. At this time, when the reflected light from the back surface is imaged, an image 131 of the reflected light from the back surface is formed in the middle (the root portion 50) as shown in FIG.
Position). At this time, the luminance is graphically displayed along the bright line A of the reflected light on the back surface, as shown in FIG. By binarizing the waveform with a predetermined threshold to determine the edge position, the edge position on the back surface (the position of the root portion 50) can be measured with high accuracy. By continuously performing this edge position measurement while moving the stage 7 in the direction of arrow B,
The shape of the edge (root portion 50) on the back surface of the transparent body can be accurately measured.

Similarly, when it is desired to measure the shape of the front surface, not the reflected light from the back surface but the reflected light from the front surface
Similarly, a process of obtaining the edge position of the image 121 of the surface reflected light may be performed. In this case, for example, the measurement target 4 shown in FIG.
The shape of the edge indicated by 52 can be measured.

Next, the method of detecting the shape of the object 4 and its edge position will be described in more detail.

FIG. 5A is a side view of the object 4 to be measured.
FIG. 5B is a front view of FIG. 5A viewed from the right side.
FIG. 5C is a bottom view of FIG. 5A viewed from below.
In FIG. 5, the edge position 50 is originally linear, but has a warp as shown in FIG. 5C due to a manufacturing error due to molding. Although this warp is extremely small in practice, it is emphasized in FIG. In the present embodiment, the shape of the warpage at the edge position 50 is measured.

As shown in FIG. 6, projection light is made incident so that the slit light impinges on the portion to be measured. At this time, as described above, light is reflected on the front surface and the back surface of the measurement target 4.
Since the light is obliquely incident, the reflection position on the front surface and the reflection position on the back surface deviate from each other. When the measurement target 4 is viewed by the TV camera 6 on the light receiving side, the portion where the slit light is reflected is located on the front surface. It is seen as two bright lines, the reflected light from the back and the reflected light from the back. Since the back surface of the measuring object 4 has only the edge position 50, the reflected light from the back surface becomes a line interrupted on the way. This is shown as 11 in FIG. 1 and FIG.

In the slit image shown in FIG. 3, the slit image 131 is an image of the reflected light from the back surface, and the position of the end portion of the slit image 131 represents the edge position 50 of the measuring object 4. First, looking at the intensity distribution of light in the horizontal direction of all images, as shown in FIG.
Data at which the light intensity increases at two positions where there are 21, 131 are obtained. Binarization is determined based on whether this light intensity is larger or smaller than a predetermined threshold. The processing is repeated one pixel at a time from the first pixel in the horizontal direction to the 512th pixel. Starting from the first pixel, when the light intensity of the pixel on the left of the pixel of interest is smaller than the threshold value and the light intensity of the pixel of interest is larger than the threshold value, the left detection point of the slit image on the memory Register in the table. Next, when the light intensity of the pixel of interest is larger than the threshold value and the light intensity of the pixel on the right of the pixel of interest is smaller than the threshold value, it is registered in the memory table as the right detection point of the slit image. When there are two slit light images on the screen as shown in FIG. 3, two sets of left detection points and right detection points of this slit image can be formed on the memory. Since it is known in advance from the configuration of the apparatus of the present embodiment that the reflected light from the back surface exists on the right side, the second set of the two sets of the left detection point and the right detection point is used, and the left detection point is used. And the center position of the right detection point is determined to be the center position A of the reflected image on the back surface of the slit light.

Next, along the center position A of the slit image,
When the distribution of light intensity of each pixel is examined in the vertical direction of the screen, data as shown in FIG. 4 is obtained. The edge position is obtained by binarizing the light intensity of this pixel with a predetermined threshold. When the light intensity of the pixel exceeds a predetermined threshold value by repeating the processing from the first pixel to the 480th pixel in the vertical direction,
The position of the pixel is defined as an edge position.

In this way, one edge position is obtained for one image.

Next, the edge position measurement is repeated over the entire length of the object 4 while stepping the stage 7 shown in FIG. 1 to sample the warped shape data of the object 4 shown in FIG. I can do it.

In the above description, the image processing is performed only on the reflection image of the slit light on the back surface. However, by performing the same edge measurement on the reflection image of the slit light on the front surface, the edge shape can be simultaneously formed on the front and back surfaces. Can be measured.

For example, when the object to be measured has a shape as shown in FIG. 8, if the slit light is irradiated within the range shown in FIG. 8, a reflection pattern as shown in FIG. 9 is obtained. From this image, the front edge and the rear edge can be measured simultaneously.

(Second Embodiment) FIG. 10 is a block diagram showing a configuration of a shape measuring apparatus according to a second embodiment.
The same reference numerals are given to the same functional portions as those of the embodiment.

In FIG. 10, 1 is a lamp as a light source, 21 is a knife edge for projecting a pattern obtained by cutting light on one side of the light source 1, 3 is an optical lens for condensing the pattern light, and 4 is a transparent to be measured. Sample 5, an imaging lens having an optical axis set in the regular reflection direction of the projection light, 6 a television camera for photographing an image formed by the imaging lens 5, 7 moving the sample 4 in the direction of arrow C An AD converter 8 for digitizing a television signal from the television camera 6;
Denotes an image processing device for obtaining the shape of a sample from digital data output from the AD converter 8; 70, a display device for outputting a measurement result from the image processing device 9;
Is an image monitor for viewing the image processed in step (a).

In FIG. 10, the knife edge 21 is arranged at a position conjugate with the focal point of the focusing lens 3, and a knife edge image is projected on the measurement object 4. At this time, the front surface reflected light and the back surface reflected light are shifted and reflected as described in the first embodiment. The knife edge 21 is provided on the side that cuts light rays reflected on the side closer to the back surface reflected light out of the front surface reflected light.
The television camera 6 that receives the reflected light is set at a position where only the back surface reflected light is incident on the imaging optical lens 5.

In this way, the light reflected on the front surface of the transparent measuring object 4 does not enter the television camera 6, and only the light reflected from the back surface can be received. The resulting image is as shown in FIG. In FIG. 10, the edge portion 41 on the back surface of the transparent body 4 can be regarded as an edge image 411 in FIG. This image can be binarized with a predetermined threshold to determine the shape of the edge image.

Also in this case, since the back surface image is not deteriorated by the reflected light from the front surface, the shape of the back surface can be obtained with high accuracy.

Similarly, when it is desired to measure the shape of the front surface, the position of the knife edge is set on the opposite side to the optical axis to cut the reflected light from the back surface, and the television camera is placed at a position to receive the reflected light from the front surface. You only need to install it. By performing image processing for obtaining the shape on the image obtained at this time,
The shape of the front surface can be accurately measured without being affected by the influence of the back surface.

The present invention can be applied to a modification or modification of the above embodiment without departing from the gist of the invention.

For example, in the above embodiment, the number of pixels of the image sensor used for the television camera 6 is set to 512 pixels in the horizontal direction,
Although 480 pixels are set in the vertical direction, it goes without saying that an image sensor having a different number of pixels may be used.

[0045]

As described above, according to the present invention,
In the shape measuring device, the shape can be measured accurately even if there is reflection on the front surface and reflection on the back surface, and the front and back surfaces of the measurement object can be measured simultaneously.

Further, by facilitating the separation of the reflected light on the front surface and the reflected light on the back surface, the accuracy of measuring the shape of the back surface can be improved.

[0047]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a shape measuring apparatus according to a first embodiment. .

FIG. 2 is a diagram illustrating a state in which illumination light is reflected by a front surface and a back surface of a transparent body.

FIG. 3 is a diagram showing a front surface reflection image and a back surface reflection image of slit light.

FIG. 4 is a diagram for explaining a method of obtaining an edge position from a luminance distribution.

FIG. 5 is a diagram showing a shape of a measurement target.

FIG. 6 is a diagram showing a projection state of slit light on a measurement target.

FIG. 7 is a diagram showing a luminance distribution of an image of front surface reflected light and an image of back surface reflected light.

FIG. 8 is a diagram illustrating a shape of a measurement target of another example.

FIG. 9 is a view showing a reflection image when the measurement object shown in FIG. 8 is irradiated with slit light.

FIG. 10 is a diagram illustrating a configuration of a shape measuring apparatus according to a second embodiment.

FIG. 11 is an explanatory diagram of an image obtained by the device of the second embodiment.

FIG. 12 is a diagram showing a configuration of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lamp 2 Slit 3 Optical lens 4 Measurement object 5 Imaging lens 6 TV camera 7 Stage 8 A / D conversion device 9 Image processing device 10 Display device 11 Image monitor

Claims (16)

[Claims] 1. A shape measuring device for measuring a shape of a transparent body, comprising: a light source for irradiating the transparent body with light; and a light shielding for shaping light from the light source into a predetermined pattern shape. Means, an optical system for condensing light passing through the light shielding means, and at least one of light transmitted through the optical system and reflected on the front surface of the transparent body and light reflected on the back surface of the transparent body. A shape measuring device comprising: a television camera for capturing an image; and image processing means for performing image processing on an image obtained by the television camera. 2. The position of the light source and the position of the light-shielding means are set such that light passing through the light-shielding means enters the surface of the transparent body at a predetermined angle. The shape measuring device according to claim 1. 3. The shape measuring apparatus according to claim 1, wherein the light shielding unit is disposed at a position conjugate with a focal point of the optical system. 4. The shape measuring apparatus according to claim 1, wherein the transparent body is arranged so that the front surface and the back surface are located near a focal position of the optical system. 5. The shape measuring apparatus according to claim 4, wherein a depth of field of the optical system is set to be deeper than a distance between a front surface and a back surface of the transparent body. 6. The shape measuring apparatus according to claim 1, wherein the light shielding means is a light shielding plate having a slit-shaped opening. 7. The shape measuring apparatus according to claim 1, wherein the light shielding means is a knife edge. 8. The apparatus according to claim 1, further comprising moving means for moving said transparent body with respect to said optical system.
3. The shape measuring device according to 1. 9. A shape measuring method for measuring a shape of a transparent body, wherein light emitted from a light source is shaped into a predetermined pattern shape by a light shielding means, and the shaped light is condensed by an optical system. Irradiating the transparent body, and capturing at least one of the light reflected on the front surface of the transparent body and the light reflected on the back surface of the transparent body with a television camera, an image obtained by the television camera And measuring the shape of the transparent body by image processing. 10. A method in which light passing through the light blocking means is incident on the surface of the transparent body at a predetermined angle.
10. The shape measuring method according to claim 9, wherein a position of the light source and a position of the light shielding unit are set. 11. The shape measuring method according to claim 9, wherein said light shielding means is arranged at a position conjugate with a focal point of said optical system. 12. The shape measuring method according to claim 9, wherein the transparent body is arranged so that the front surface and the back surface are located near a focal position of the optical system. 13. The shape measuring method according to claim 12, wherein the depth of field of the optical system is set to be larger than the distance between the front surface and the back surface of the transparent body. 14. The shape measuring method according to claim 9, wherein a light shielding plate having a slit-shaped opening is used as the light shielding means. 15. The shape measuring method according to claim 9, wherein a knife edge is used as the light shielding means. 16. The shape measuring method according to claim 9, wherein the shape of the transparent body is continuously measured by moving the transparent body with respect to the optical system.