JPS61260106A - Method and device for three-dimensional measurement - Google Patents

Abstract

PURPOSE:To attain the automatic measurement by scanning an object to be measured with the aid of an intensity modulated light beam while its modulation frequency is changed by matching to the shape of the object to be measured and creating a striped pattern on the object in a short time. CONSTITUTION:In terms of a holographic laser beam scanner, some holograms are disposed and fixed on the circular periphery of a disk, and rotated at a high speed, thereby scanning a laser beam 1. When the pre-optical system of the holographic laser scanner 4 is adjusted so that the scanning beam 1 can converge in the scanning direction and can diverge in the sub-scanning direction on the surface of the object 6, a scope having the length decided as a scan length is uniformly scanned according to the beam width in the sub-scanning direction. At this time the output of the laser 1 is intensity-modulated to create the striped pattern on the surface of the object 6. Moreover by controlling an injection current to the laser 1, fringe having arbitrary phases and amplitudes can be projected, and the fringe with the pitch suitable to the shape of the object 6 can be freely created.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to three-dimensional measurement using striped patterns, sometimes typified by moiré topography.

(Prior art and its problems) Moire topography projects a striped pattern onto a physical surface, superimposes the striped pattern deformed by the shape of the object and the standard striped pattern, and creates a moire pattern that shows the contour lines generated as the difference frequency. This is a method of measuring the shape of an object by observing it. For details, see, for example, the magazine [Applied Optics], Volume 9,
1970, the paper “Moir6Topo-gr.” on pages 1467-1472
mentioned in aphy month. In this method, as shown in FIG.
There are two types: a grating irradiation type that irradiates with a grating 24, and a grating projection type that forms an image of the grating 24 on the object plane as shown in FIG.

When comparing both methods, the latter is more flexible and has a wider range of applications in terms of operability. Regarding grating projection type moiré topography, for example, see the magazine [Applied Optics, Volume 22, 1]
983, the paper “Automatic 3” written in 850-855 Hessy.
Projection Moire using moving grid method in dimensional topography (Projection Mo1r4 with
moving grants for antom
3-D topography) J. In the projection moiré method, the grating exists near the light source and the camera 25, and compared to the irradiation moiré method,
Operability is good. However, since both methods use a fixed grid, it is difficult to vary the stripe spacing.

Moiré fringes are proportional to the fringe spacing. Therefore, as the number of moire fringes increases, the amount of information increases, making it possible to analyze complex objects, but on the other hand, it takes a lot of time to process images of moire fringes. Therefore, it is effective to change the pitch of the stripes depending on the shape of the object. However, to achieve this using conventional methods, it is necessary to prepare a large number of gratings with different pitches, replace them depending on the shape of the object, and secure them within the device with high precision. Therefore, it takes a lot of time to measure and cannot be used for automatic measurement.

(Objective of the Invention) The object of the present invention is to generate a striped pattern of arbitrary pitch on the object surface in a short time without using a grid, with the optimum pitch according to the shape of the object, and to perform automatic measurement. The purpose of this invention is to provide a three-dimensional measurement method and device that make it possible.

(Structure of the Invention) The measurement method of the present invention scans an object to be measured with the intensity-modulated light while changing the modulation frequency of the intensity-modulated light according to the shape of the object to be measured, and creates stripes with an optimal pitch in each part of the object. The method is characterized in that a pattern is formed on the object to be measured. The three-dimensional measurement device also 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, and a beam of monochromatic light emitted from the light source that is shaped to form the hologram. an optical system for guiding the light to the lens; a signal generator for changing the current injected into the light source; a control device for controlling the signal generator; and a camera for observing the scanning beam scanned by the holographic laser scanner. , and an image processing device that extracts moiré fringes from the scanning fringe pattern and the deformed fringe pattern on the object plane obtained by the camera 12.

(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 intensity modulating the output of the laser, a striped pattern similar to that of the prior art can be generated on the object plane.

Furthermore, by controlling the current injected into the laser, it is possible to project fringes with arbitrary phase and amplitude.
You can freely generate fringes with a pitch that is optimal for the shape of the object. Usually, the intensity is modulated with a rectangular wave, but when modulated with a sine wave, it is possible to prevent the occurrence of high-order moiré fringes.

(Example) FIG. 1 shows an example of the present invention. Semiconductor laser 1
The oscillated light is collimated by a collimating lens 2, converted into an elliptical beam by a cylindrical lens 3, and then scanned onto an object 6 by a hologram lens 5 of a holographic laser scanner 4. For example, GP-
The output voltage of the power supply 10 having an interface such as GP-IB is controlled by a signal generation 511 such as a function generator having a GP-IB interface, which is controlled by an arithmetic control unit 12 such as a microcomputer having an IB interface. is changed, and the semiconductor laser 1 is modulated. At this time, a part of the scanning beam by the hologram lens 5 is taken out by a beam splitter, and two position detectors 8 are placed at the scanning end on a plane at the same distance as the scanning plane.

The signal from the position detector 8 is sent to the arithmetic and control unit 12 through an arithmetic circuit (comprised of an operational amplifier) 13 that takes the differential of its output. The arithmetic and control unit 12 operates as shown in the flowchart shown in FIG. That is, when the beam scans the position detector 8 above the scanning end, a signal is generated to start modulating the semiconductor laser, and when the beam passes the position detector 8 below the scanning end, the modulation of the semiconductor laser is generated. The signal generator 11 is controlled by generating a signal to terminate the process. After the modulation is completed, a constant current is applied from the signal generator 11 to control the laser to continuously oscillate in order to detect the modulation start position needle for the next scan. FIG. 5 shows the signals that control each device at this time. Upon receiving the signal (a) from the position detector above the scanning end, the arithmetic and control unit 12 sends a modulation start control signal (c) to the signal generator 11. In response to this, the signal generator 11 sends a laser modulation signal (e) to the power supply 10, which converts this signal into a current necessary to drive the laser and injects it into the laser. Figure 2 shows how the laser injection current changes over time. The modulation frequency is controlled by the arithmetic and control unit 12 so that a striped pattern with an optimal pitch is formed in each part of the object. The arithmetic and control unit 12, which has received the signal (b) from the position detector at the lower scanning end shown in FIG. 5, sends a modulation end control signal (d) to the signal generator. In response to this, the signal generator finishes transmitting the laser modulation signal to the current, and the power supply injects a constant current above the threshold into the laser. Laser threshold current I
When a pulsed current Ia larger than th is injected into the laser, a striped pattern is generated on the object surface. For example, when the holographic laser scanner 4 consisting of 20 hologram lenses is rotated at 6000 rpm, the
With m5ec, stripes can be generated on the entire scanning surface. Therefore, by using a TV right camera that can accumulate light for 500 m5ec or more, it is possible to image deformed stripes on the object plane. Frame memory and GP
- A striped pattern corresponding to the signal generated by the signal generator 11 is input from the arithmetic and control unit 12 in advance to the image processing device 14, which is equipped with an interface such as IB and has image addition/subtraction and integration functions. By superimposing the image with the image taken by the right camera, moiré fringes are generated and displayed on the data output device 15 such as a CRT.

The four arithmetic operations for an image are to digitally represent the gradation of an image and perform gradation calculations for each dot. Control device 1
Since the semiconductor laser 1 can be modulated by 2, a striped pattern having an arbitrary pitch can be generated. FIG. 3 is a diagram showing the effects of this invention when compared with the conventional example. The conventional method only generates stripes with a constant period, so even for objects with large and small changes in shape, as shown in Figure 3(a),
As in b), it is not possible for both subcommittees to measure with the same degree of accuracy. On the other hand, since the intensity of the laser beam is modulated in this invention, the fringe pitch can be changed arbitrarily (e)
As shown in FIG. 2, a dense striped pattern can be generated in areas where the shape change is large, and a sparse striped pattern can be generated in areas where the shape change is small, so that measurements can be made efficiently in terms of accuracy and measurement time.

(Effects of the Invention) As described above, according to the three-dimensional measurement method and apparatus of the present invention, the pitch of the stripes can be arbitrarily controlled within the lattice plane simply by changing the modulation frequency of the light source, and the pitch of the stripes can be adjusted to the shape of the object. Stripes with optimal pitch can be generated in a short time. As a result, automatic measurement becomes possible because the troublesome work of replacing the grid is eliminated.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing temporal changes in current injected into a semiconductor laser, and FIG. 3 is a diagram showing an example of the present invention.
A diagram comparing the effects of this invention and a conventional example, Figure 4 is a flowchart of the device, Figure 5 is a timing chart, Figure 6 is a diagram showing a conventional example of grating irradiation type moiré topography, and Figure 7 is grating projection. FIG. 2 is a diagram showing a conventional example of type moiré topography. In the figure, 1... Semiconductor laser 2... Collimating lens 3... Cylindrical lens 4... Holographic laser scanner 5... Hologram lens 6... Object 7... Beam splitter 8...・Position detector 9...TV camera
1o...1 power source...2 signal generators
12... Arithmetic control device 13... Arithmetic circuit
14...Image processing device 15...Data output device Komatamon/v1 Director 1, :Nsu 1% (δSakitakufu Miyomi 嘱地Hurst 2 Zusho Mamine 3 Mouth (a) 斡＠ Diagram (b) June atmosphere (c) I

Claims (2)

[Claims] (1) Scanning the object to be measured with the intensity modulated light while changing the modulation frequency of the intensity modulated light according to the shape of the object to be measured, forming a striped pattern with an optimal pitch on each part of the object. A three-dimensional measurement method characterized by: (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; a signal generator for changing the current injected into the light source; a control device for controlling the signal generator; a camera for observing the scanning beam scanned by the holographic laser scanner; a scanning stripe pattern; and the camera 12. 1. A three-dimensional measuring device comprising: an image processing device that extracts moiré fringes from a deformed fringe pattern on an object plane obtained by the method.