JPH0729452Y2 - Displacement measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention captures the reflected / scattered light of a laser beam with which a measurement target is irradiated by a photodetector, and the displacement of the measurement target is detected by the output signal of the photodetector. The present invention relates to a displacement measuring device for measuring.

[Prior Art] FIG. 6 is a schematic structural diagram for explaining the operation principle of the displacement measuring apparatus 10. As shown in the figure, in this displacement measuring device, the laser light emitted from the semiconductor laser 1 is narrowed down through the illumination lens 2 and is irradiated onto the surface of the measuring object 3. Part of the light reflected / scattered on the surface of the measurement target 3 passes through the imaging lens 4 and is projected on the light receiving surface of the photodetector 5 to form an image of a reflection point. When the measurement target 3 moves back and forth, the image of the reflection point formed by the imaging lens 4 also moves on the light detection element 5 accordingly. This photo detector 5
Is for transmitting to the arithmetic circuit as an electric output the position on the light receiving surface where the light is incident. Therefore, the amount of movement of the surface of the measurement target 3 can be extracted as an electric signal.

[Problems to be Solved by the Invention] As shown in FIG. 7, half of the surface remains the glass surface 11, and the other half of the surface is the Au vapor deposition surface 12 (hereinafter referred to as Au surface 12).
The surface of the glass plate which is said to be the object of measurement. Here, using the displacement measuring device 10 as described above, the Au surface 12 and the glass surface
Displacement measurement was performed by a route that is perpendicular to the boundary line 13 with 11 and is shown by an arrow A in the figure. FIG. 8 (a)-
(C) shows the result, and FIG. (B) shows the measured value at the center of the measurement range.
In (c), the distance between the device 10 and the measurement target 3 is 700 than in (b).
In the case of μm larger, (a) is 700 μm shorter.
As can be seen from these measurement results, the measured values on the glass surface 11 near the Au surface 12 are greatly disturbed, and peaks of signals that should not be detected appear. As described above, according to the conventional displacement measuring device, a correct result may not be obtained even when trying to measure the vicinity of the boundary region where the surface states greatly differ, for example, when measuring a glass surface close to the metal deposition surface. There was a problem.

The present invention has been made in view of such circumstances, and in a displacement measuring device using a laser beam and a photodetector, it is possible to perform displacement measurement without being affected by the surface condition around the measurement point. It is an object.

[Means for Solving the Problem] The displacement measuring device of the present invention is applied to a measuring object having a measuring surface in which a region having a high reflectance and a region having a low reflectance are adjacent to each other with a boundary, and a laser light source and a laser light source are provided. An illumination lens for converging light from the source to create a light beam that irradiates the surface of the object to be measured, an imaging lens for converging light reflected and scattered by the object to be measured, and an imaging lens And outputs the displacement of the surface of the measurement object corresponding to the movement of the imaging point on the surface of the photodetection element In the displacement measuring device including the arithmetic circuit, the longitudinal direction coinciding with the moving direction of the image forming point on the photodetecting element is parallel to the boundary, and the width thereof is on the front surface of the photodetecting element. A slit with the same diameter as the image point is set. Characterized in that was.

[Operation] The laser light emitted to the surface of the measurement target is reflected and scattered,
An image is formed on the light receiving surface of the photodetector through the slit. When the object to be measured is displaced, the image formation point moves along the slit on the light receiving surface, but peripheral unnecessary light in the direction intersecting with the slit is blocked by this slit, so it is affected by the surface condition around the measurement point. However, the photodetector element can output an electric signal according to the displacement of the measurement point.

[Embodiment] First, regarding the reason why an unmeasurable region is generated when measuring the vicinity of the boundary region where the surface condition of the measurement object is greatly different, The background to the invention and the invention was devised. Now, consider a case where the glass surface 11 close to the Au surface 12 as the metal vapor deposition surface is measured by the measuring method as shown in FIG. FIG. 5 is a diagram showing a state in which a measurement target is viewed in plan in such a measuring method. Arrow 20 in the figure
Indicates the incident light path of the laser light, and the arrow 21 indicates the reflected light path of the laser light. In addition, reference numeral 30 in the figure indicates a measurement point on the glass surface 11, and also indicates a spot of a beam imaged on the photodetector 5. Reference numeral 40 in the figure is an image of the photo-detecting element 5 projected on the measurement surface. Now, when the image magnification of the light receiving system in the displacement measuring device is low, the image 40 of the photodetector 5 on the measurement surface becomes considerably large with respect to the spot 30, as shown in FIG. In the range of this image 40, not only the glass surface 11 to be measured but also the Au surface 12 is included.
The reflectance of the surface 12 is higher than that of the glass surface 11, and it is considered that part of the light reflected by the Au surface 12 reaches the photodetector 5. At the time of measurement, a spot corresponding to the displacement of the glass surface 11 is spotted on the light receiving surface of the photodetector 5 corresponding to the image 40.
Although 30 moves in a direction substantially parallel to the boundary line 13, unnecessary peripheral light of the spot 30 reflected by the Au surface 12 shown in FIG. 4 (c) is also emphasized and enters the photodetector 5. Therefore, the pattern of the intensity distribution of the spot 30 imaged on the photo-detecting element 5 of the displacement measuring device is deviated from that at the time of calibration. For this reason, it is considered that the region of low reflectance close to the region of high reflectance becomes unmeasurable. That is, when measuring the boundary portion with different reflectance,
When unnecessary ambient light reaches a portion having a high reflectance, the unnecessary ambient light is emphasized and deviates from the intensity distribution pattern at the time of calibration.

Therefore, the present inventor has devised a displacement measuring device in which a slit is provided on the front surface of the photodetecting element 5 after grasping such a problem that has not been known in the past. FIG. 1 and FIG. 2 show an embodiment of the present invention. The same parts as in the prior art are designated by the same reference numerals as in FIG. 6 and their explanations are omitted. In this displacement measuring device 50, a slit 51 is provided on the front surface side (the side on which light is incident) of the light detection element 5. This slit
The longitudinal direction of 51 is parallel to the moving direction of the spot 30 on the light receiving surface of the photodetector 5, and its width is almost the same as the diameter of the spot 30 (beam diameter at the reflection point). By providing such a slit 51, unnecessary peripheral light of the spot 30 reflected by the Au surface 12 is blocked as shown in FIGS. 4 (a) and 4 (b). Therefore, when the glass surface 11 and the Au surface 12 are measured in the same direction as in FIG. 7, the peak of the signal that should not be detected on the glass surface 11 near the Au surface 12 is as shown in the measurement result of FIG. It is much smaller than before. That is, according to the present embodiment, the measurable region of the glass surface 11 close to the Au surface 12 is wider than before, and it is possible to measure up to a portion considerably close to the metal vapor deposition surface having high reflectance. Instead of using a slit, it is conceivable to use a photodetector element with a narrow width in the direction orthogonal to the moving direction of the image formation point. However, the photodetector element does not detect light even if the light spot deviates from the light receiving surface. Since it has some sensitivity, it is affected by ambient light, and the effect is lower than when a slit is used.

[Advantages of the Invention] According to the present invention, a slit having a width substantially equal to the diameter of the image forming point on the photodetector is aligned with the moving direction of the image forming point on the photodetector, and the high reflectance of the measurement surface is achieved. It was provided on the front surface of the photodetection element so as to be parallel to the boundary between the region and the low reflectance region.
Therefore, the skirt portion of the intensity distribution pattern of the light beam that reaches the photodetector is removed, and the skirt of the light spot formed on the photodetector is clean. Therefore, when a measurement target having a measurement surface adjacent to each other with a boundary between a high reflectance region and a low reflectance region is measured, even if the hem portion is reflected by the high reflectance region of the measurement target, the photodetector element The center of gravity of the intensity pattern of the upper light spot is less likely to be affected by the skirt portion, and highly accurate displacement measurement can be performed even in the measurement near the boundary surface. This effect is obtained by using this device in which the slit whose width and longitudinal direction are set as described above is installed on the front surface of the photodetector, and which has a measurement surface in which a high reflectance region and a low reflectance region are adjacent to each other with a boundary. It is particularly obtained when measuring a low reflectance region near the boundary in the measurement target. In a measurement object having a measurement surface in which a high reflectance area and a low reflectance area are adjacent to each other with a boundary, unless the low reflectance area near the boundary is measured, the hem of the light spot as described above is used. No problem arises, and the bottom of the light spot formed on the photodetector cannot be removed unless the slit width and longitudinal direction are set as described above for the measurement target. Further, even if the slit is installed at another position, for example, in front of the light receiving lens, only the amount of light entering the photodetector is reduced, and the bottom of the light spot formed on the photodetector cannot be removed.

[Brief description of drawings]

FIG. 1 is a structural view showing an embodiment of the present invention, FIG. 2 is a schematic perspective view showing the structure of the same embodiment, and FIG. 3 is a glass surface and an Au surface continuously measured in the same embodiment. FIG. 4 (a) is a plan view showing the measurement surface in the vicinity of the measurement point in the same example, showing the image of the photodetector, and FIG. 4 (b) is the same figure (a). FIG. 5C is an intensity distribution diagram of a cross section of the spot in the YY direction, FIG. 5C is a intensity distribution diagram of the cross section of the spot in the YY direction when there is no slit, and FIG. FIG. 6 is a diagram showing an image of a photodetector, FIG. 6 is a schematic perspective view showing a configuration of a conventional displacement measuring device, and FIG. 7 is a displacement measuring method of Au surface and glass surface in the conventional device. Is a perspective view showing
FIG. 8 is a graph showing the results of displacement measurement obtained by the measurement of FIG. 3 ... Object to be measured, 5 ... Photodetector, 11 ... Glass surface as low reflectance area, 12 ... Au vapor deposition surface (Au surface) as high reflectance area, 30 ... Imaging point As a spot, 50 ... Displacement measuring device, 51 ... Slit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-191915 (JP, A) JP-A-55-40942 (JP, A) JP-A-60-135714 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A high-reflectance region and a low-reflectance region are applied to a measuring object having a measuring surface adjacent to each other with a boundary, and a laser light source and a surface of the measuring object by condensing light from the laser light source. An illumination lens for forming a light beam for irradiating the object, an imaging lens for condensing the light reflected and scattered by the measurement object to form an image, and a light beam from the measurement object condensed by the imaging lens A photodetection element for forming an image on a light receiving surface, and an arithmetic circuit for outputting the displacement of the surface of the measurement object in response to the movement of the image formation point on the surface of the photodetection element,
In the displacement measuring device provided with, on the front surface of the photo-detecting element, the longitudinal direction coinciding with the moving direction of the imaging point on the photo-detecting element is parallel to the boundary, and its width is the diameter of the imaging point. Displacement measuring device having slits which are almost the same.