JPH0226162B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is applicable to measuring the shape of easily deformed objects such as industrial products, living organisms, and cultural assets, and measuring the thickness of objects on production lines and the damage caused to objects. This invention relates to a non-contact displacement detector that uses laser light in the visible range and is used to measure size and position.

[Conventional technology and its problems]

Conventionally, this type of non-contact displacement detector has been shown, for example, in FIG. In other words, in order to confirm the irradiation position of the laser beam on the object to be detected,
The structure included a He--Ne gas laser 1 that emits visible laser light of 632.8 nm, an acousto-optic modulator 2, a reflecting mirror 3, a condenser lens 4, an optical semiconductor position detector 5, etc. in one case.

This non-contact displacement detector detects an object in the following manner. First, He-Ne gas laser 1
The laser beam 6 emitted from the acousto-optic modulator 2
transmitted light 7, which is modulated by, separated into transmitted light 7 and diffracted light 8, and whose optical axis is adjusted by a reflecting mirror 3;
The transmitted light 7 of the diffracted light 8 is blocked by the wall of the slit 9, and only the diffracted light 8 is emitted to the outside of the non-contact displacement detector. The emitted diffracted light 8 is irradiated onto a light irradiation point 11 of the object to be detected 10, and is reflected and scattered at this light irradiation point 11. A part of the reflected and scattered light 12 and the background light around the object to be detected 10 are focused by the condensing lens 4 in this non-contact displacement detector to a condensing point on the light receiving surface of the optical semiconductor position detector 5. The light is focused on 13. Next, the optical semiconductor position detector 5 outputs the position of this focal point 13 as an electrical signal. Next, in order to improve the S/N ratio between the electrical signal to be detected due to the reflected/scattered light 12 by the detected object 10 and the electrical signal that is noise due to surrounding background light, The arithmetic circuit 14 detects the electrical signal from the reflected/scattered light 12 in synchronization with the modulation of the acousto-optic modulator 2, and calculates the position of the detected object 10. This calculation result is sent to the outside of the non-contact displacement detector. For example, display unit 1 of a printer or CRT
5 is displayed. Furthermore, in the case of the object 10' that has moved on the optical axis of the diffracted light 8, the light 12' reflected and scattered at the light irradiation point 11' is focused on the condensing point 13'.
The position of the object to be detected 10' is calculated using a method similar to that described above.

However, conventional non-contact displacement detectors require a laser light source, an optical modulator such as an acousto-optic modulator, a position detector, and a circuit for driving and controlling these (for example,
Since the drive circuit 16) for the acousto-optic modulator 2, power supply, etc. are housed in one case, the weight is 2 to 3 kg.
The disadvantage was that it was large and difficult to move. In addition, this non-contact displacement detector has many built-in precise fine adjustment mechanisms, such as adjusting the optical axis of the reflecting mirror, blocking transmitted light with a slit, and adjusting the black angle in the case of an acousto-optic modulator. However, when this non-contact displacement detector is moved, the alignment changes due to vibrations, shocks, etc., resulting in deviations in the amount of laser light and the optical axis. If each part, such as the fine adjustment mechanism, is made more robust in order to eliminate this drawback, it will become even more complex and the weight will increase.

Furthermore, in conventional configurations, a heat source such as a laser light source, a position detector, and a condensing lens are housed in one case, so the position detector and condensing lens are affected by heat, resulting in detection errors. Furthermore, in order to prevent this detection error, for example, a cooling fan 17 is built in, but there is a drawback that the influence of heat cannot be completely prevented by the cooling fan 17. When using a cooling device that allows complete prevention, the non-contact displacement detector has the drawback of becoming more complex and larger.

[Object and structure of the present invention]

The present invention has been made in order to eliminate the above-mentioned drawbacks, and includes a detection light source section having a visible range laser light source and an optical modulator that modulates the laser light emitted from the laser light source; An optical transmission line that transmits light from the detection light source section to the detection sensor section, a condensing lens that collects the light transmitted through the optical transmission line that is reflected and scattered by the object to be detected, and a position detector. By providing a non-contact displacement detector comprising a detection sensor section having a detection sensor section, the detection light source section and the detection sensor section are separated via the optical transmission path. The purpose is to facilitate the movement of the parts and improve detection accuracy. Hereinafter, a second embodiment of the present invention will be described.
This will be explained in detail based on the figures.

〔Example〕

FIG. 2 is a configuration diagram showing an embodiment of the present invention. First, this example uses a He-Ne gas laser (wavelength 632.8 nm, output 5 mW) 1 as a laser light source that emits visible light, and a center frequency 80 M as an optical modulator.
Hz acousto-optic modulator 2, reflector 3, slit 9,
an acousto-optic modulator drive circuit 16 for driving the acousto-optic modulator 2; a cooling fan 1;
7 and a detection light source section 19 having a condensing lens 18
And, a quartz-based optical fiber (GI-50) with a length of about 3 m serves as an optical transmission path for transmitting the laser light emitted from the detection light source section 19 to the detection sensor section 22, which will be described later.
20, one end of this optical fiber 20, collimating lens 21, condensing lens 4, and one-dimensional position detection PSD.S1352 (manufactured by Hamamatsu Photonics Co., Ltd., effective light receiving area 34 x 2.5 mm).

According to this embodiment, first, a 632.8 nm laser beam 6 emitted from a He-Ne gas laser 1 is modulated by an acousto-optic modulator 2 at a modulation frequency of 2 kHz, and separated into transmitted light 7 and diffracted light 8. be done. Transmitted light 7
is blocked by the wall of the slit 9, and the diffracted light 8
The light passes through the slit 9 and is coupled by the condensing lens 18 to the optical fiber 20 connecting the detection light source section 19 and the detection sensor section 22 and propagates. and,
The diffracted light 8 emitted from one end of the optical fiber 20 in the detection sensor section 22 is irradiated as collimated light 23 by the collimating lens 21 to the light irradiation point 11 of the detected object 10, and is partially reflected and scattered. Ru. Note that if the object to be detected 10 is not an object that easily reflects and scatters light, the light irradiation point 11 of the object to be detected 10 may be provided with means for reflecting and scattering light. Next, a part 12 of the reflected/scattered light and the object 10 to be detected are
The surrounding background light is focused by the condensing lens 4 onto a condensing point 13 on the light receiving surface of the optical semiconductor position detector 5, and is detected by the arithmetic circuit 14 of the detected object 10 in the same way as in the conventional case. The position is calculated.

As described above, according to this embodiment, the detection light source section and the detection sensor section are separated, compared to the conventional non-contact displacement detector in which the detection light source section and the detection sensor section are housed in one case. During measurement, the movable object (conventionally, the non-contact displacement detector itself, in this embodiment, the detection sensor section) is lightweight;
It becomes very easy to move. In addition, in the detection light source section, which has a precise fine-tuning mechanism for the optical system necessary for an acousto-optic modulator, etc., only the detection sensor section moves through an optical transmission path such as an optical fiber during measurement. It is not affected by vibration or shock caused by this movement. As a result, changes in the amount of light and the optical axis due to misalignment within the detection light source section can be reduced, and the detection accuracy can be improved because it can be stably maintained. Furthermore, since the detection sensor section does not include a heat source such as a laser light source or an acousto-optic modulator drive circuit, the influence of heat on a position detector such as an optical semiconductor position detector can be reduced.

The present invention is not limited to the above-described embodiments, but may include the following embodiments. First, as a visible range laser light source,
Although a He-Ne gas laser is used, the present invention is not limited to this, and a laser light source that emits laser light such as a He-Cd gas laser may also be used.
A laser light source with a wavelength of 400 nm to 700 nm with high visibility is preferable. Next, the optical modulator may be an optical modulator using an electro-optic effect, an optical modulator using a magneto-optic effect, etc., and an acousto-optic modulator is preferable because it has a high extinction ratio and is simple in configuration. Next, the position detector is not limited to an optical semiconductor position detector, but may be a position detector such as a CCD that can extract a signal depending on the position where light is irradiated. Next, the light to be detected may be transmitted light instead of diffracted light, but since diffracted light has a higher extinction ratio and has an easier S/N ratio with the surrounding background light, diffracted light is more desirable. Next, the optical transmission line is not limited to the quartz-based GI-50 optical fiber, but may be other optical fibers such as plastic fiber. Next, although there is no need for a reflecting mirror, if it is desired to downsize the detection light source section, it is better to provide a reflecting mirror. Next, the condensing lens and slit in the detection light source section and the collimating lens in the detection sensor section may be provided as appropriate depending on the object to be measured and the measurement accuracy.

〔Effect of the invention〕

As described above, according to the present invention, by separating the detection light source section and the detection sensor section and providing an optical transmission path such as an optical fiber between them, it is possible to perform tasks such as guiding a robot arm or performing three-dimensional measurements on a stage. This makes it extremely easy to move the detection sensor section of the non-contact displacement detector in accordance with the object to be detected, and has the effect that the position of the object to be detected can be detected with high precision.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional non-contact displacement detector, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1... He-Ne gas laser, 2... Acousto-optic modulator, 3... Reflector, 4... Condensing lens, 5...
Optical semiconductor position detector, 6... Laser light, 7... Transmitted light, 8... Diffracted light, 9... Slit, 10...
Object to be detected, 11... Light irradiation point, 12... Reflected/scattered light, 13... Focusing point, 18... Focusing lens,
19...detection light source section, 20...optical fiber, 21
... Collimating lens, 22 ... Detection sensor section.

Claims (1)

[Scope of Claims] 1. A detection light source section having a visible range laser light source and an optical modulator that modulates the laser light emitted from the laser light source, and transmitting the laser light from the detection light source section to a detection sensor section. and a detection sensor section having a position detector and a condensing lens that collects light transmitted through the optical transmission path that is reflected and scattered by an object to be detected; A non-contact displacement detector characterized in that the detection light source section and the detection sensor section are separated via a path. 2. The non-contact displacement detector according to claim 1, wherein the optical transmission path is an optical fiber. 3. The non-contact displacement detector according to claims 1 to 2, wherein the optical modulator is an acousto-optic modulator.