JPS61260107A - Method and device for three-dimensional measurement - Google Patents

Abstract

PURPOSE:To judge the dimension number of approved contour moire fringes even of a staged object by changing a striped pattern in the direction of the pattern and projecting the striped pattern to an object to be measured at least twice. CONSTITUTION:When the pre-optical system of a holographic laser scanner 4 is adjusted in such a way that a scan beam can converge in a scan direction and diverge in a sub-scan direction on the surface of the object 7, a scope having the length decided as a scan length is uniformly scanned according to the beam width in the sub-scan direction. At this time an optical space modulator 4 is placed in the pre-optical system, and a light transmissivity is set to zero or '1', thereby creating the striped pattern. The scanner 5 scans said pattern, whereby the striped pattern can be created on the surface of the object 7. When the striped pattern 30 in parallel with the stage is projected on the staged object with the aid of a lattice 22 in terms of moire topography, an approved contour becomes discontinuous at the position where the stage is present, and accordingly the dimension number cannot be decided. However, fringes having different directions are projected on the subject at least twice, whereby the dimension number can be always decided, and the shape of the object can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention particularly relates to a three-dimensional measurement method and apparatus using stripes such as moire topography.

(Prior art and its problems) Moiré topography projects a striped pattern onto the object surface, superimposes the striped pattern deformed due to the shape of the object and the standard striped pattern, and shows the isotopic line generated as the difference frequency. This is a method of measuring the shape of an object by analyzing moire fringes. For details, see, for example, the magazine "Applied Optics", 9
vol., 1970, pages 1467-1472.
-graphy) J. This method includes a grid 22 placed just in front of the object 23 as shown in FIG.
There are two types: a grating irradiation type in which a point light source 21 irradiates the light with a point light source 21, and a grating projection type in which an image of a grating 24 is formed on the object plane as shown in FIG. When comparing both methods, in terms of operability,
The latter is more flexible and has a wider range of applications. Regarding grid-projection moiré topography, see, for example, the magazine “Applied Optics”.
22, 1983, pages 850-855 [Projection Moiré using moving grid method in automatic three-dimensional topography]
a with moving grants for
r antomated 3-D topography
It is detailed in month y. In these methods, the direction of the generated grid is always constant. However, when measuring an object 23 as shown in FIG. 2, it becomes impossible to determine the order of the contour moiré fringes in places where the object has a step-like shape.

(Objective of the Invention) An object of the present invention is to provide a three-dimensional measuring method and a three-dimensional measuring device that can determine the order of contour moiré fringes even in a step-like object.

(Structure of the Invention) The three-dimensional measurement method of the present invention is characterized in that a striped pattern is projected onto an object to be measured at least twice while changing the direction of the stripes. In addition, this three-dimensional measurement device includes a light source consisting of a semiconductor laser, a holographic laser scanner in which a plurality of hologram lenses are arranged on a disk,
an optical system that shapes a monochromatic light beam emitted from the light source and guides it to the hologram lens; an optical spatial modulator that spatially modulates the beam; a control device that controls the optical spatial modulator; It is equipped with a camera for observing a scanning beam scanned by a holographic scanner, and an image processing device for extracting moiré fringes from a scanning grating pattern and a grating pattern deformed on the object plane obtained by the camera. The structure is as follows.

(Operation/Principle of the Invention) In a holographic laser beam scanning device such as a holographic laser scanner, several holograms are arranged and fixed on the circumference of a disk, and the laser beam is scanned by rotating the holograms at high speed. do. If the front optical system of a holographic laser scanner is adjusted so that the scanning beam converges in the scanning direction on the object plane and diverges in the sub-scanning direction, the beam width in the sub-scanning direction
The length determined as the scan length is scanned over the entire surface. At this time,
By placing a one-dimensional optical spatial modulator inside the front optical system and setting the light transmittance to 0 or 1, a striped pattern is created. By scanning this with a scanner, a striped pattern can be generated on the object surface. Furthermore, if the light transmittance pattern of the optical spatial modulator is moved in time series with the rotation of the scanner, the striped pattern will have an inclination on the object plane. By changing the moving speed of the pattern, a striped pattern with an arbitrary inclination can be generated.

In moire topography, when a striped pattern 30 in the direction shown in FIG. 2 is projected onto a step-like object using a grating 22, the contour lines become discontinuous at positions where there are steps, making it impossible to determine the order. At this time, as shown in FIG. 3, if stripes 31 that are not parallel to the step are projected, the contour lines become continuous, making it possible to determine the order. Before measurement, the presence or absence of a step and the direction of the step are unknown. However, by projecting stripes in different directions onto the object at least twice, a step difference in which the contour lines are discontinuous in each measurement will not result in a step difference in measurements in other directions. As a result, the order can always be determined and the shape of the object can be measured. That is, in the first measurement,
For example, stripes in the direction shown in FIG. 2 are projected onto the object. Next, the second
In the second measurement, for example, as shown in Figure 3, by projecting fringes in a direction 90° different from the direction of the fringes in the first measurement onto the object, information missing in one measurement can be compensated for in the other. can.

(Example) FIG. 1 shows an example of the present invention. Light emitted from a light source 1 consisting of a semiconductor laser is collimated by a collimating lens 2, converted into an elliptical beam by a cylindrical lens 3, and passed through an optical spatial modulator 4 such as a liquid crystal shutter array, for example. The crocodile is scanned by the hologram lens 6 of the holographic laser scanner 5.

The light transmittance of each array of optical spatial modulators is set to 0 or 1 in a striped manner by a modulator control device 12 such as a function generator having a GP-IB interface. When this striped modulated light is scanned and projected onto the object plane by a scanner, a pattern of light transmittance 4 of the optical spatial modulation S4 is scanned over a length determined as the scanning length of the scanner. At this time, the encoder 13 inputs the rotation synchronization signal of the scanner to the arithmetic and control unit 10 such as a microcomputer having a GP-IB interface. Arithmetic control device 10
When the pattern of light transmittance of the optical spatial modulator 4 is changed in time series, the striped pattern on the object plane has an inclination. FIG. 6 shows the state of the signal at this time. The arithmetic control device 10 that receives the synchronization signal 60 of the encoder 13 is the modulator control device 1
A modulation start signal 61 is sent to 2. In response to this, the modulator control device 12 generates an optical spatial modulator control time-series signal 62 to move the light transmittance pattern of the optical spatial modulator in time series, thereby forming stripes with an arbitrary inclination on the object plane. Generate a pattern. The striped pattern formed on the object plane is observed by a TV left camera, and its image is transferred to an image processing device 11, such as a GP-IB, which has functions of integrating, adding and subtracting between images having an ink face. A reference striped pattern corresponding to each striped pattern is input in advance to the image processing device 11 from the arithmetic and control device 10, and moire fringes between the striped pattern and the striped pattern deformed on the object plane are observed. After one measurement is completed,
The pattern of the optical spatial modulator 4 is changed to generate and observe a striped pattern in a direction different from the first measurement. Note that the four arithmetic operations between images means that the gradation of the image is expressed in digital 779, and the gradation calculation is performed for each dot.

(Effect of calculation) As detailed above, by projecting striped patterns in different directions onto an object at least twice, it is possible to easily measure the three-dimensional shape of a step-shaped object, which was previously impossible to measure. Become.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing an example of the direction of a grid that cannot be measured in a stepped object, and FIG. FIG. 4 is a diagram showing an example of the direction of the grating, and FIG. 4 is a diagram showing a conventional example of grating irradiation type moire topography. FIG. 5 is a diagram showing a conventional example of grating projection type moire topography. FIG. 6 is a diagram showing a timing chart of signals. In the figure, 1... Semiconductor laser 2... Collimating lens 4... Optical spatial modulator 3... Cylindrical lens 4
... Holographic laser scanner 6 ... Hologram lens 7 ... Object 8 ... TV left camera
10... Arithmetic control device 11... Image processing device 12... Modulator control device 13... Encoder 21... Light source 22... Grid
23...Object 24...Lattice
Figure 601) Coater setting synchronization signal / let #s: IM sand fg number

Claims (2)

[Claims] (1) A three-dimensional measurement method characterized by projecting a striped pattern onto an object to be measured at least twice while changing the direction of the stripes. (2) a light source made of a semiconductor laser; a holographic laser scanner including a plurality of hologram lenses arranged on a disk; an optical system that shapes a monochromatic light beam emitted from the light source and guides it to the hologram lens; an optical spatial modulator for spatially modulating a beam; a control device for controlling the optical spatial modulator; a camera for observing the scanning beam scanned by the holographic scanner; A three-dimensional measurement device comprising: a striped pattern deformed on an object plane;