JPH01233309A - Linearity meter - Google Patents

Abstract

PURPOSE:To measure the degree of linearity of a surface to be measured, by detecting a light intensity pattern which is formed on a light-detecting element by a light transmitted through a detecting prism set on a truck moving on the surface to be measured and a light reflected and transmitted again through the prism. CONSTITUTION:A laser light from a laser 1 is condensed to be passed through a pinhole 4 by a condenser lens 8, made further into a parallel light by a collimator lens 9 and emitted from one end of a measuring area. A detecting prism 11 is set on a truck 6 moving on a surface B to be measured in an optical path of the laser light. When the truck 6 is made to move on the surface B, a light intensity pattern is formed in a recessed or projecting shape according to the case when the optical axis of the detecting prism 11 is on the upper side of the optical axis OA or to the case when the former is on the lower side of the latter. The light intensity pattern is varied in accordance with the amount of displacement of the detecting prism 11. Based on the relationship between the amount of displacement and the light intensity pattern, the amount of displacement is determined from the pattern detected by a linear array sensor 13 and the degree of linearity of the surface B to be measured is measured therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a straight line meter that is not limited by the growth of the measurement head and uses a laser beam with a simple optical system for detecting the measurement surface.

<Prior Art> FIG. 5 is a block diagram of a linear meter using a confocal lens system. In FIG. 9, numeral 1 indicates a laser as a light source. The laser light from here passes through a mirror 2 and is focused onto a pinhole 4 by a lens 3. 5 is an optical system mounted on a cart 6 that moves on the measurement surface B in the optical path of the laser beam, and 7 is a screen. The optical system 5 has a configuration as shown in FIG. The characteristic of the zero-lens optical system that uses a three-lens optical system in which a concave lens 5c is inserted in the center between convex lenses 5a and 5b with the same focal length f is that the distance S between the pinhole 4 and the screen 7 is If the optical system 5 is fixed and moved during this period, the magnification of the image on the screen 7 will remain 1. If the optical system 5 moves upward by δχ, the image on the screen 7 will move downward by 2δχ. . The linearity of the measurement surface B is determined based on this amount of movement. However, this device has drawbacks such as the measurement length S being fixed and the structure of the optical system 5 becoming large.

On the other hand, there is a linear meter in which a photodetecting element having a detection surface divided into four parts is moved over the measurement surface and a laser beam is applied to the detection surface to perform measurement. In this device, it is necessary to irradiate a laser beam onto the center of a photodetector element moving on a measurement surface, and alignment work for this purpose is difficult and errors are likely to occur.

<Problem to be Solved by the Invention> The technical problem to be solved by the present invention is to realize a linear meter that has a simple structure of the optical system mounted on the trolley, has no measurement length limit, and is less prone to measurement errors. It's about doing.

Means for Solving the Problems The present invention has a light source that converts laser light into collimated light having a circular cross section and emits it from one end of the measurement area, and a trolley that moves over the measurement surface in the optical path from the light source. It is placed,
a detection prism made of a material that has a light absorption property for the laser beam, has at least two parts with different thicknesses, and is installed such that the optical axis passes through a boundary area between these two parts at the reference position; , a reflecting means disposed at the other end of the measurement area and reflecting the light that has passed through the detection prism so as to return through a symmetrical optical path with respect to the optical axis; and a reflecting means that is reflected by the reflecting means and passes through the detection prism again. and a photodetecting element for detecting the light, and the linearity of the measuring surface is determined from the light intensity pattern formed on the photodetecting element.

Function> The above technical means works as follows. That is, in the case where the detection prism is, for example, a prism with a thin upper half and a thick lower half, and the optical axis passes through a boundary region between these two parts having different thicknesses, the light detected by the photodetecting element The intensity is constant.

When the boundary region is below the optical axis, a convex light intensity pattern τ with high light intensity at the center is formed in the photodetector element. On the other hand, when the boundary region is above the optical axis, a concave light intensity pattern is formed in the photodetecting element, with the light intensity being low at the center. This light intensity pattern changes depending on the amount of deviation of the detection prism. Since the relationship between the light intensity pattern and the amount of deviation is determined in advance, the amount of deviation can be found from the light intensity pattern measured based on this.

<Example> The present invention will be described in detail below with reference to the drawings. Fig. 1 is a configuration diagram of the device according to the embodiment of the present invention, Fig. 2 is a perspective view of the main parts, Fig. 3 is an explanatory diagram of the operation of the device according to the embodiment of the present invention, and Fig. 4 shows the light intensity pattern. , the same elements as those in FIG. 5 are designated by the same reference numerals, and explanations thereof will be omitted. The laser beam from laser 1 passes through condensing lens 8
The light is condensed into the pinhole 4 by the collimator lens 9, and then converted into parallel light by the collimator lens 9 and emitted from one end of the measurement area.

Reference numeral 10 denotes a half mirror, which transmits the laser beam and emits it to the measurement area, while reflecting the return light from the measurement area to the detector side in the direction perpendicular to the optical axis OA.

Reference numeral 11 denotes a detection prism having light absorption characteristics, and a 1lf detection prism is mounted on the cart 6 that moves on the measurement surface B in the optical path of the laser beam.
It has been f. The detection prism 11 has a shape as shown in FIG.
1b is formed thick (thickness 2d). At the reference position, the boundary area H between these two parts 11a and llb is aligned with the optical axis O.
It is set so that A passes through.

Reference numeral 12 denotes a reflecting means fixed at the other end of the measurement area, which reflects the light transmitted through the detection prism 11 so as to return through a symmetrical optical path with respect to the optical axis OA. A cube reflecting prism is used. 13 is a photodetection element using a linear array sensor, 14
is a condensing lens. The light detection element 13 detects the light that is reflected by the corner cube reflecting prism 12, passes through the detection prism 11 again, and is reflected by the half mirror 10 in a direction perpendicular to the optical axis OA.

Next, the operation of such a device will be explained with reference to FIGS. 3 and 4. FIG. 3(a) shows a case where the detection prism 11 is at the reference position, and in this case, the optical axis OA is installed so as to pass through the boundary area H between the two parts 11a and llb of the detection prism 11 having different thicknesses. ing. In this state, the light incident on the linear array sensor 13 passes through an optical path with a thickness of 3d in the detection prism 11, and all the light is absorbed uniformly, so the light intensity is constant as shown in FIG. A pattern can be obtained.

As a result of moving the trolley 6 on the measurement surface B, if the detection prism 11 is located above the optical axis OA as shown in FIG. 11, which transmits an optical path with a thickness of 3d,
The light intensity pattern includes a portion close to the optical axis OA that transmits an optical path of 4d, and the light intensity pattern becomes a concave shape as shown in FIG. 4(b). Note that the portion where the light intensity is low widens as the detection grism 11 deviates upward from the optical axis OA.

On the other hand, when the detection prism 11 is located below the optical axis OA as shown in FIG. The light intensity pattern includes the transmitted light and the light transmitted through the 2d optical path near the optical axis OA, and the light intensity pattern has a convex shape as shown in FIG. 4(c). The portion with high light intensity spreads as the detection prism 11 deviates downward from the optical axis OA.

The light intensity pattern changes depending on the amount of deviation of the detection prism 11, and the relationship between the amount of deviation and the light intensity pattern (specifically, the part with high light intensity in the center of the pattern, or the part with low light intensity in the center of the pattern) , which are involved in the detection of this area, and the relationship with the number of elements of the near array sensor), then the amount of deviation is determined from the pattern detected by the linear array sensor 13 based on this relationship. In this way, as long as the amount of deviation of the detection prism 11 is within the range of the circular cross section of the collimated laser beam, the straightness of the measurement surface B can be measured.

<Effects of the Invention> According to the present invention, the detection prism is the only optical system mounted on the trolley, so the structure of this part can be simplified. Furthermore, since the light source and the reflecting means are both fixed, measurement errors are less likely to occur, and alignment work is simple. Furthermore, there is an advantage that the length of the measurement area over which the cart moves can be arbitrarily selected.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an apparatus according to an embodiment of the present invention, Fig. 2 is a perspective view of main parts, Fig. 3 is an explanatory diagram of the operation of the apparatus according to an embodiment of the present invention, Fig. 4 is a light intensity pattern diagram, and Fig. 5 is a conventional FIG. 6 is a diagram showing the configuration of the optical system in the device shown in FIG. 5. DESCRIPTION OF SYMBOLS 1... Laser, 6... Cart, 9... Collimator lens, 10... Half mirror 111... Detection prism, 12... Reflection means, 13... Photodetection element, B
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Claims (1)

[Claims] A light source that converts laser light into collimated light with a circular cross section and emits it from one end of the measurement area, and a material that is placed on a trolley that moves over the measurement surface in the optical path from the light source and that has light absorption properties for the laser light. a detection prism formed by, having at least two parts with different thicknesses and installed so that its optical axis passes through the boundary area of these two parts at the reference position; and a detection prism placed at the other end of the measurement area. a reflecting means that reflects the light that has passed through the detection prism so as to return through a symmetrical optical path with respect to the optical axis; and a photodetection element that detects the light that has been reflected by the reflection means and has passed through the detection prism again. 1. A straightness meter, characterized in that the straightness of the measurement surface is determined from the light intensity pattern formed on the photodetection element.