JPH0275906A - Image formation type displacement gauge - Google Patents

Abstract

PURPOSE:To improve the displacement detecting accuracy of the title displacement gage by irradiating a guide beam of a visible wavelength in addition to a detecting beams of an invisible wavelength and, at the same time, separating a guide beam from reflected rays of light made incident on a photodetector for detecting displace ment. CONSTITUTION:In the first place, a changeover switch 19 is switched to a light source 10 side and the light source 10 is driven 11. Then a guide beam of a visible wavelength emitted from the light source 10 irradiates an object 20 to be measured through a collimator lens 2B, half mirror 17, and object lens 5. While the object 20 is irradiated by the guide beam, the position of the guide beam is adjusted so that the position of the image of the guide beam can become the position to be measured for displace ment. Then the switch 19 is switched to another light source 1 side and a detection beam of an invisible wavelength emitted from the light source 1 forms an image on the object 20 through a collimator lens 2A, polarization beam splitter 3, 1/4 wave plate 4, the mirror 17, and the lens 5. The detection beam reflected by the object 20 advances the same path in the opposite direction and is made incident on a photode tector 8 through the beam splitter 3, a condenser lens 3, and cylindrical lens 7. The photodetector 8 measures a displaced quantity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a displacement meter that measures the displacement of a surface to be measured based on minute changes in light reflected from the surface to be measured. Regarding the displacement meter used.

[Conventional technology]

With the recent ultra-high precision positioning and speeding up of mechatronic products, displacement measurement in the micro-vibration region has become important. Research and development of such precision measurement methods is progressing at various companies,
Various types of optical lasers (especially semiconductor lasers)
Displacement meters are being commercialized.

For example, the laser displacement meter manufactured by Keyence Corporation (
LC series) uses a semiconductor laser (wavelength 7) as the light source.
80nm infrared light), and when actually performing measurements using this displacement meter, the beam itself cannot be directly seen where the measurement spot is formed, so a tool to visualize the light (engineering sheet) is used. , IR fosbar, etc.)
Measurement is performed by aligning the spot onto the surface to be measured.

In addition, since the light reflected from the object to be measured is captured by a photodetector in the displacement meter to detect displacement information, there is a problem that the tilt of the surface to be measured itself has a large effect, so alignment adjustment based on the tilt is extremely important. It is. Regarding this, the amount of light received on the photodetector is electrically detected within the signal processing circuit and displayed on a monitor, and the alignment is adjusted based on the light amount level.

[Problem to be solved by the invention]

Optical displacement meters that use lasers have extremely high precision, so research and development is progressing at various companies and they have been commercialized, but in order to make the displacement meters themselves smaller, semiconductor lasers are used as the light source. (wavelength: 780 nm), which is infrared light, so it is not possible to visually confirm directly where the measurement point is formed, and submicron measurements can be performed using such a high-precision displacement meter. When doing so, there is a problem in that it is extremely difficult to adjust the alignment to the object to be measured, and to determine the reference position with respect to the inclination of the surface and the direction of the optical axis.

On the other hand, in processing equipment using semiconductor lasers, as described in JP-A-62-161490, visible wavelength light is A laser beam is used as a guide beam to irradiate the processing position through the same optical system as the laser beam for processing, and after visually confirming that the beam is irradiated at the correct position, the beam for processing is changed to the laser beam of the visible wavelength. It is known to perform processing by superimposing the irradiation on the

However, in a displacement meter that measures the displacement of a surface to be measured from minute changes in light reflected from the surface, when the invisible beam for measurement and the visible beam for guide are superimposed and incident on the displacement meter, the measured value There was a risk that it would affect. Also,
Because of the visible wavelength laser generator, the displacement meter itself becomes large and there is a risk that it will be inconvenient to handle. Semiconductor lasers with visible wavelengths are being developed to solve these difficulties, but they have not yet been put into practical use.

When measuring the behavior of each part of a mechatronic mechanical system, the object to be measured is often located in a narrow space between parts, making it difficult to use conventional displacement meters in actual equipment due to work space constraints. Therefore, displacement measurement is performed using a model. It is necessary to downsize the displacement meter for measurement with actual equipment, but in the past, for example, in ``Research on optical non-contact probes (second report), Precision Machinery 51/12/1985J,
There is no description of shortening the optical path length in the optical system configuration of the sensor.

The length of the displacement meter is determined by the optical path length between the objective lens of the displacement meter and the photodetector, and is greatly influenced by the focal length of the condenser lens for focusing the detection beam on the incident surface of the photodetector. The distance between the emission principal point of the light ray that is imaged on the photodetector entrance surface by this condensing lens and the image formation surface (photodetector entrance surface),
There is a relationship between the focal lengths of the objective lenses, which is defined from the viewpoint of the sensitivity of the displacement meter, and it has been difficult to shorten the focal length of the condenser lens. The principal point of exit is a single lens position at which when parallel light rays are incident on the lens system and are imaged, the images are formed at the same position.

An object of the present invention is to facilitate the alignment of a displacement meter using a guide beam, and at the same time eliminate the influence of the guide beam on displacement measurement values.

Another object of the present invention is to provide a displacement meter that is easy to handle.

[Means to solve the problem]

The above problem is solved by irradiating the object to be measured with the light beam emitted by the first light source as a detection beam through an objective lens, and detecting the fluctuation of the reflected light with a photodetector to detect the displacement of the object. The image type displacement meter includes a second light source that emits a visible wavelength light beam, and a means for making the light beam emitted from the light source as a guide beam superimposed on the same optical axis as the detection beam and irradiating the object to be measured. This is achieved by including means for separating a guide beam and a detection beam included in the reflected light reflected from the object to be measured.

As a means of separating the guide beam and detection beam,
It may also be a changeover switch that instructs only one of the first light source and the second light source to emit a light beam, and a wavelength filter or It may also be a wavelength filter prism.

Further, in the imaging type displacement meter according to claim 1, wherein the second light source is connected to the displacement meter via a detachable optical fiber, the second light source may be one using a light emitting diode. The above-mentioned problem can also be achieved by the imaging type displacement meter described in Item 1.

Further, the guide beam superimposed on the detection beam forms an image on the side of the objective lens from the focus of the objective lens of the displacement meter, and a screen is provided on the outer periphery of the objective lens to receive the reflected light of the guide beam. It may also be used as an imaging type displacement meter as described in , in which the screen is divided in the circumferential direction and/or the radial direction. The imaging type displacement meter according to claim 6 may include a light receiver equipped with a photoelectric conversion element.

A claim in which the guide beam is composed of at least three mutually independent light beams, and the intersection of the three light beams with a plane perpendicular to the optical axis of the detection beam at a position before entering the objective lens forms a triangle. The imaging type displacement meter described in item 1 may also be used.

Furthermore, the above problem is solved by reflecting the light beam emitted by the first light source by a polarizing beam splitter, irradiating the object to be measured as a detection beam, and making the reflected light enter a photodetector through the polarizing beam splitter. It is also possible to provide a condensing lens and a concave lens on the optical axis between the polarizing beam splitter and the photodetector in an imaging type displacement meter that detects the displacement of the object to be measured based on fluctuations in reflected light with a photodetector. achieved.

Further, it may be an imaging type displacement meter according to claim 9, in which the condenser lens is provided between the objective lens and the polarizing beam splitter, and the condenser lens is provided on the optical axis between the objective lens and the photodetector. The imaging type displacement meter according to claim 1 may be provided with a concave lens and a concave lens.

[Effect]

A visible wavelength light beam is emitted from the second light source, and this light beam is superimposed on the same optical axis as the detection beam as a guide beam, and is irradiated onto the object to be measured. Since the guide beam is irradiated through the same optical path as the detection beam, the detection beam and guide beam are imaged at the same position on the object to be measured, and the image formation position of the detection beam can also be confirmed from the image formation position of the guide beam. Ru.

Further, the guide beam and the detection beam are separated from the reflected light reflected from the object to be measured, and the reflected light of the guide beam does not enter the photodetector, thereby eliminating errors in displacement of the object to be measured due to the guide beam.

Furthermore, if a light emitting diode is used as the second light source that emits visible light, the second light source can be miniaturized, thereby avoiding an increase in the size of the displacement meter body. Even if the light source emits light and the light source and the displacement meter body are connected by a detachable optical fiber, it is possible to avoid increasing the size of the displacement meter body.

Furthermore, according to the present invention as set forth in claim 6, the guide beam is imaged closer to the objective lens than the focal point of the objective lens of the displacement meter, so that the guide beam is located at a position farther from the objective lens than the image formation position. The guide beam reflected by the object to be measured spreads at the position of the objective lens to a greater extent than the outer diameter of the objective lens, and enters the screen provided on the outer periphery of the objective lens. Since the size of the spread increases in proportion to the distance between the guide beam imaging position and the object to be measured, the distance between the object to be measured and the objective lens can be determined from the size of the spread, and the alignment of the displacement meter can be adjusted. It becomes possible.

In addition, the amount of the guide beam irradiation surface incident on each part of the screen is determined by the distance from the objective lens of the displacement meter to the measured object, the guide beam optical axis (same as the detection beam optical axis), and the measured object. It varies depending on the angle formed by the guide beam irradiation surface of the object. If the light-receiving surface of the screen is composed of a photoelectric conversion element, and this screen is divided in the radial direction and/or circumferential direction and the electrical output of each divided part is calculated, conversely, the object to be measured and the displacement meter objective lens The distance between
The angle of the guide beam irradiation surface of the object to be measured is detected.

When the guide beam is not one beam but at least three mutually independent parallel beams and is irradiated onto the surface to be measured through the objective lens of the displacement meter, the three beams are formed on the surface to be measured. The shape created changes depending on whether the surface to be measured is on the objective lens side of the objective lens focal point or not.

When a condensing lens combined with a concave lens is provided on the optical axis between the objective lens and the photodetector, the light reflected by the object to be measured 20 is transmitted to the condensing lens 6 as shown in FIG.
after being refracted so as to form an image at the focal position of the concave lens 9
after being further refracted by the concave lens, the photodetector 8
Therefore, even if the focal length of the condenser lens 6 is shortened and the distance between the condenser lens 6 and the photodetector is shortened,
The position of the emission principal point J' of the light beam incident on the photodetector is closer to the objective lens than the position of the condenser lens, and this emission principal point J'
The distance between the photodetector 8 and the photodetector 8 is maintained at a required distance.

Further, a condensing lens is provided in combination with a concave lens in front of the photodetector, which converts the diffused light beam from the light source into the polarizing beam splitter, and converts the light beam similarly reflected as the diffused beam into parallel light beams from the polarizing beam splitter. Then, the light beam reflected by the object to be measured becomes a condensed light beam by the condensing lens and passes through the polarizing beam splitter 3.Next, this light beam enters a concave lens combined with the condensing lens and is refracted. After that, the light beam enters the photodetector 8, so that the distance between the principal point of emission of the light beam that enters the photodetector and the photodetector is maintained at a required distance.

〔Example〕

A first embodiment of the present invention will be described with reference to the drawings. 1st
The figure shows an optical system of an optical imaging type displacement meter which is an embodiment of the present invention, and includes a light source 1 that generates an invisible laser beam, and a light source 1 that generates an invisible laser.
A collimator lens 2A that converts the detection beam generated by the parallel beam into a parallel beam, and refracts the direction of the parallel detection beam by 90 degrees toward the surface to be measured and does not refract the reflected light from the surface to be measured. a polarizing beam splitter (hereinafter referred to as PBS) 3, a half mirror 17 that allows the beam refracted by the PB 83 to go straight, and a polarizing beam splitter 3 disposed on the same optical axis between the half mirror 17 and the PH 10. The four-wavelength plate 4, the objective lens 5 disposed on the same optical axis adjacent to the object to be measured side of the half mirror 17, and the half mirror 17 from a direction making 90 degrees with the detection beam. A collimator lens 2B that sends a visible light guide beam as a parallel light beam, a light source 10 that sends a visible light laser guide beam to the collimator lens 2B, and a light source 10 that is adjacent to the PBS 3 on the opposite side to the quarter wavelength plate. A condenser lens 6 is provided on the same optical axis and has the PBS 3 side as the incident side, and a cylindrical lens 6 is provided on the same optical axis adjacent to the exit side of the condenser lens and has the condenser lens side as the incident side. It is provided with a lens 7 and a photodetector 8 which is provided on the same optical axis adjacent to the exit side of the cylindrical lens 7 and whose incidence side is the cylindrical lens 7 side. This displacement meter also includes a changeover switch 19, which is a means for separating the guide beam and detection beam, whose secondary side is connected to the light sources 1 and 10, and a changeover switch 19, which is connected to the primary side of the changeover switch 19. A laser drive circuit 11 is attached.

The light source 1 is a semiconductor laser that emits infrared light with wavelengths of 780 nm and 830 nm.

The operation of the displacement meter shown in the figure will be explained. First, in order to perform alignment, the changeover switch 19 is switched to the light: g10 side, and the light [10 is driven by the laser drive circuit 11 to generate a visible wavelength laser beam (hereinafter referred to as a guide beam). The generated guide beam is made into a parallel beam by the collimator lens 2B, and then converted into a parallel beam by the half mirror 17.
Can be bent in the 0 degree direction. The guide beam exiting the half mirror 17 is refracted by the objective lens 5 and irradiated onto the object 20 to be measured. The position of the object to be measured 20 or the displacement meter is adjusted so that the position of the image of the guide beam on the object to be measured 20 is the displacement measurement position of the object to be measured.

When adjustment (alignment) is completed, selector switch 19
is switched to the light source 1 side, and the light source 1 is driven by the laser drive circuit 11 to generate a laser beam of an invisible wavelength (hereinafter referred to as a detection beam), and the generation of the guide beam from the light source 10 is stopped. The detection beam generated by the light source 1 passes through the collimator lens 2A and becomes a parallel beam, and then enters the PH 10 and is directed toward the object to be measured.
It is refracted 0 degrees. The detection beam refracted by 90 degrees then passes through a quarter-wave plate, passes straight through a half mirror 17, enters the objective lens 5, is refracted, and forms an image on the object to be measured 20. That is, the detection beam passes through the half mirror 17 and the objective lens 5 along the same optical axis as the guide beam, and is irradiated and imaged at the position on the object to be measured 20 that is irradiated with the guide beam. The detection beam irradiated onto the object to be measured 20 is reflected and travels back along the same path as when it was incident.

However, the reflected detection beam is not refracted by the PBS 3 and travels straight, passes through a condenser lens 6 and a cylindrical lens 7, and then enters a photodetector 8. A change in the detection beam reflected light due to the displacement of the object to be measured 20 is detected by the photodetector 8, and the amount of displacement of the object to be measured is detected.

According to this embodiment, the guide beam is not emitted when displacement is detected by the detection beam, and the guide beam does not cause an error in displacement detection. Furthermore, since the two light sources are driven by a common laser drive circuit, the circuit is simple.

FIG. 2 shows a second embodiment of the present invention, in which a light source 10 that does not generate a laser is used, for example, a light emitting diode (LED), and the other configuration is a changeover switch. 19 are identical to the first embodiment shown in FIG.

According to this embodiment, the displacement meter main body can be made smaller than when using a light source that generates a visible wavelength laser.

FIG. 3 shows a third embodiment, in which the light source 10 that generates a visible wavelength laser attached to the displacement meter in the first embodiment is connected and detached via an optical fiber 13 with connectors 21 at both ends. It is freely connected to the displacement meter body. He-
Ne lasers, argon lasers, etc. are large light sources, and if they are directly attached to a displacement meter, the displacement meter will become large and inconvenient to operate. This can prevent a decrease in the operability of the meter body.

FIGS. 4A and 4B illustrate the fourth embodiment of the present invention. Showing a fifth embodiment, a changeover switch 19 provided in the first embodiment
This prevents the guide beam from entering the photodetector 8 without providing a guide beam.

In the embodiment shown in FIG. 4A, a wavelength filter 12, which is a means for separating a guide beam and a detection beam, is provided in front of the photodetector 8, and a changeover switch is not provided. This is the same as the embodiment shown in FIG. In this embodiment, taking advantage of the difference in wavelength between the detection beam and the guide beam, a wavelength filter 12 is provided that allows only the detection beam to pass, and the light at the wavelength that causes the guide beam and other disturbances is filtered to the photodetector 8. It is cut off in front of the sensor to eliminate any effect on displacement detection.

In the embodiment shown in FIG. 4B, instead of the wavelength filter 12 in front of the photodetector 8, a wavelength filter prism 14 is used.
The embodiment is the same as the embodiment shown in FIG. 4A, except that it is provided between the PH 10 and the condenser lens 6. The wavelength filter prism 14 is a means for separating a guide beam and a detection beam. Also in this embodiment, the guide beam is refracted by the wavelength filter prism and does not enter the photodetector 8, so the guide beam does not affect displacement measurement.

4 above. According to the fifth embodiment, the light source 1 that generates the detection beam constantly generates the beam, and does not generate or stop the beam every time a measurement is performed.
There is no need to wait until the beam stabilizes.

FIG. 4C shows a sixth embodiment of the invention. This embodiment differs from the fourth embodiment in that, instead of providing a wavelength filter 12, a half mirror 17 is used as a second polarizing beam splitter PB33', and the guide beam is directed to the second polarizing beam splitter PB33'.
The other components are the same as those of the fourth embodiment. PB83' serves as a means for separating the guide beam and detection beam. In this embodiment as well, the light source 1 is a semiconductor laser (wavelength: 780 nm).
.

830nm), PBS3 uses a wavelength of 800nm.
This is for near nm. Against this.

PB33' is for visible light with a wavelength of 600 nm. In this configuration, since the detection beam is different from the applicable wavelength range, the total amount of light incident on PBS 3' is refracted by 90 degrees and emitted, whereas the guide beam, which is visible light, is reflected and refracted by PBS 3'. The light travels straight through the objective lens and is irradiated onto the object to be measured. Furthermore, the entire amount of the reflected detection beam is reflected by PBS 3' and enters the photodetector 8, but the reflected light of the guide beam is reflected by PB 83'.
Because it travels straight without being refracted or reflected.

The light does not enter the photodetector 8.

According to this embodiment, in addition to being able to eliminate the influence of the guide beam on the photodetector without providing a changeover switch, wavelength filter, wavelength filter prism, etc., the PB
Since the entire amount of light of the incident detection beam is reflected at 83', the amount of detection beam light decreases little and the accuracy of displacement detection is improved.

The alignment adjustment for measuring the displacement of the object to be measured 20 includes aligning the axis of the point to be measured with respect to the displacement meter, as well as adjusting the inclination of the surface to be measured with respect to the optical axis of the detection beam.

FIG. 5 shows a part of the optical system of the seventh embodiment.
In the embodiment shown in Fig. B, instead of the collimator lens 2B that makes the guide beam a parallel beam, a convex lens 18 that makes the guide beam a constricted beam is provided, and the display line 16 when focused.
The difference is that a screen 15 having a screen 15 is provided concentrically on the outer periphery of the exit surface of the objective lens 5. The rest of the configuration is the same as that in FIG.
The guide beam is incident on the object to be measured 20 and is imaged on the object to be measured 20 . The guide beam enters the objective lens 5 through the half mirror 17 as a contracted light, so it forms an image on a surface closer to the objective lens than the imaging surface of the detection beam.The guide beam is reflected by the object to be measured 20 and enters the screen 15. But,
The position of the surface to be measured matches the imaging position If of the detection beam (reference position of the object to be measured) C, and the surface to be measured coincides with the detection beam (
When the guide beam is perpendicular to the optical axis, a reflected image as shown in FIG. 6(b) is projected onto the screen 15. A focus display line 16 is provided so as to coincide with the outer peripheral position of the reflected image at this time. If the object to be measured is located at a distance a from the focal plane 11c of the objective lens 5,
As shown in FIG. 6(a), the reflected image of the guide beam on the screen 15 becomes larger than the display line 16 when in focus, and conversely, if it is closer, the reflected image becomes smaller as shown in FIG. 6(c). If the surface to be measured is not perpendicular to the optical axis of the guide beam but is inclined, a reflected image as shown in FIG. 6(8)(d) will result. When the screen 15 is made of a semi-transparent material, it is possible to observe the displacement meter from behind (to the right in the figure).

The screen 15 is divided into four as shown in FIG.

It consists of a photoreceiver made up of two or eight divided photoelectric conversion elements, and by signal processing the output of each divided part, the deviation of the surface to be measured from the reference position and the inclination of the surface to be measured are detected. As shown in Fig. 7(a), the receiver is divided into four parts,
Each divided part A, B, C.

Assuming that the amount of light received at D is A', B', C', and D', the direction of inclination can be obtained by calculating the following equation.

X= (A'+D')-(B'+C')y=
If (A'+B')-(c'+D')x=y=o, it is determined that there is no slope.

When the light receiver is divided as shown in FIG. 7(b), the signal value at zero focus, in which the positional deviation of the surface to be measured from the reference position is detected by the equation below, is taken as the reference value.

When in focus, reference value = A' + B' When close, reference value <A' + B' When far, reference value >A' + B' When the receiver is divided as shown in Figure 7 (Q), the above calculation is performed. By combining, perspective.

Both tilt detections are possible.

By using the method described above, it is possible to automatically detect the distance, near, and inclination of the surface to be measured using a combination of a photoreceiver and a calculation device, and by appropriately selecting a photoelectric conversion element, invisible wavelength It is also possible to detect distance and inclination using the light beam.

FIG. 8 shows a part of an optical system according to an eighth embodiment of the present invention, which detects the inclination and distance of a surface to be measured. The difference between this embodiment and the embodiment shown in FIG. 4A is that the guide beam incident on the objective lens 5 is composed of at least three light beams parallel to the optical axis and separated from each other, and these three light beams are parallel to the optical axis. The point of intersection of the detection beam with a plane perpendicular to the optical axis at a position before entering the lens 5 is not on a straight line. FIG. 8(b) shows the arrangement of the guide beams when they enter the objective lens 5. In this embodiment configured in this way, when the surface to be measured is at the focal position of the objective lens, the three guide beams are As shown in FIG. 9(b).

If they converge at one point on the surface to be measured and are further away from the focal plane, then as shown in Figure 9 (
An image is formed on the surface to be measured in the shape shown in a), and if it is closer than the focal plane, the image is formed in the shape shown in FIG. 9(c). If the surface to be measured is not perpendicular to the optical axis of the detection beam, the
), the position of the image is disturbed. That is, for alignment, it is sufficient to adjust the object to be measured or the displacement meter so that the three guide beams converge at one point as shown in FIG. 9(b).

According to this embodiment, alignment adjustment can be performed while directly checking visually in this way, so a displacement meter that is easy to use can be obtained.

A ninth embodiment of the present invention will be described with reference to FIG. A relay lens 2C is provided adjacent to the light source 1 on the optical axis of the light beam generated by the light source 1, and a polarizing beam splitter 3 is provided adjacent to the relay lens 2c. of the polarizing beam splitter 3 from the light source 1 to the polarizing beam splitter 3
A condenser lens 6 is provided on the optical axis of the reflected light beam (detection beam) adjacent to the side on which the incident light beam is reflected, and a condenser lens 6 is provided adjacent to the condenser lens 6 on the optical axis of the reflected light beam (detection beam). A 174 wavelength plate 4 is provided, and an objective lens 5 is further provided adjacent to the 1/4 wavelength plate 4. In addition, a cylindrical lens 7 is provided on the opposite side of the polarizing beam splitter 3 from the condenser lens 6.
are provided on the same optical axis with the polarizing beam splitter 3 side as the incident side.

A plano-concave lens 9 is provided adjacent to the cylindrical lens 7 on the same optical axis, and a photodetector 8 is provided adjacent to the concave lens 9 on the same optical axis. The condenser lens 6 sends the detection beam reflected by the polarizing beam splitter 3 as a parallel beam to the 174-wave plate 4, and also sends the reflected light, which is a parallel beam sent from the 174-wave plate 4, to the polarizing beam splitter 3 as a contracted beam. It is something that is complicated.

The detection beam generated by the light source 1 passes through the relay lens 2c and enters the polarizing beam splitter 3 as a diffused beam. The detection beam incident on the polarizing beam splitter 3 is reflected, changes its 90' optical axis, and enters the condenser lens 6 as a diffused beam. The detection beam, which is refracted by the condenser lens 6 and turned into a parallel beam, passes through the quarter-wave plate 4 and the objective lens 5, is irradiated onto the object to be measured, is reflected once, and travels back along the same optical path.

The light enters the polarizing beam splitter 3 as a contracted light beam and passes through as it is. The detection beam reflected light that has passed through the polarizing beam splitter 3 is refracted by a cylindrical lens 7, then refracted by a concave lens 9, and then enters a photodetector 8. The quarter-wave plate 4 is combined with the polarizing beam splitter 3 to enable effective use of light.

In FIG. 12 showing an example of the prior art, an object to be measured 20
A cylindrical lens 7 is provided so that the theory of astigmatism can be applied to the imaging system that images the reflected light onto the photodetector 8 in order to capture the displacement in the optical axis direction of the photodetector 8. In this embodiment, since the plano-concave lens 9 is provided between the cylindrical lens 7 and the photodetector 8, the emission principal point of the condenser lens 6 is focused due to the combined lens effect. Becomes the objective lens side of the optical lens 6,
The optical path between the condenser lens 6 and the photodetector 8 is shortened without shortening the distance between the photodetector 8 and the emission principal point, and an astigmatism difference is also generated on the photodetector 8. . The condensing lens 6 is combined with a relay lens 2c, and the detection beam passing through the condensing lens 6 in the direction of the objective lens is made into a parallel beam. In the embodiment shown in FIG. 11, the distance between the objective lens 5 and the photodetector 8 is 67.5 mm, but in the conventional example shown in FIG. 13, it is 228.81 a+m, and the length of the displacement meter is shortened. It is clear that

This is because when a parallel ray enters a single lens, the principal point of exit of the lens is approximately at the center of the lens, but in this example, the lens is a combination of a condenser lens and a concave lens, so the principal point of exit is from the condenser lens. This position has the effect of shortening the optical path while maintaining the same performance.

Even when a half mirror was provided in the optical path in order to superimpose the guide beam on the detection beam, by shortening the optical path with the above-mentioned configuration, the effect of suppressing the increase in the size of the displacement meter was obtained.

〔Effect of the invention〕

According to the present invention, in addition to the detection beam of invisible wavelength, the guide beam of visible wavelength is irradiated, and the means is provided for separating the guide beam from the reflected light incident on the photodetector for displacement detection. It is possible to prevent the guide beam reflected light from entering the photodetector, which has the effect of improving the accuracy of displacement detection.

Since the laser light source that generates the guide beam is separated from the displacement gauge body and coupled to the displacement gauge body via a detachable optical fiber, the displacement gauge can be easily operated.

The guide beam forms an image on the objective lens side from the focal plane of the objective lens, which is the reference position of the surface to be measured, and a screen is provided around the objective lens to receive the reflected light of the guide beam. It becomes possible to detect the distance of the surface to be measured from the reference position and the inclination with respect to the optical axis of the detection beam from the deviation in the position of the reflected light incident on the surface, which has the effect of facilitating the seven alignments for displacement detection.

According to the present invention as set forth in claims 9 and 10.11, since a condensing lens combined with a concave lens is used in the displacement meter, the optical path of the reflected light can be shortened, and the displacement meter can be made smaller or larger. The effect of suppressing the oxidation was obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a first embodiment of the present invention. FIG. 2 is a partially omitted sectional view showing a second embodiment of the present invention;
FIG. 3 is a perspective view showing the third embodiment, 4B, 4b, 4
Figure c is a sectional view showing the 4th, 5th and 6th embodiments, respectively;
FIG. 5 is a partial sectional view showing the seventh embodiment, and FIG. 6 is a partial cross-sectional view showing the seventh embodiment.
7 is a front view showing a modification of the example shown in FIG. 6, FIG. 8 is a partial sectional view showing the eighth embodiment, and FIG. 9 is a front view taken along line VI-VI in the figure. 8 is a front view taken along the line ■-■ in FIG. 8, and FIG. 10 is an optical path diagram showing the principle of optical path shortening. FIG. 11 is an optical path diagram showing a ninth embodiment of the present invention. FIG. 12 is a schematic diagram showing an example of the prior art, and FIG. 13 is an optical path diagram showing an example of the prior art. DESCRIPTION OF SYMBOLS 1... First light source, 5... Objective lens, 6... Condenser lens, 8... Photodetector, 9... Concave lens, 10
...Second light source, 12...Wavelength filter, 13...
・Optical fiber, 14...Wavelength filter prism, 15
... Screen, 19 ... Changeover switch, 20
...Object to be measured.

Claims (1)

[Claims] 1. The light beam emitted by the first light source is used as a detection beam to irradiate the object to be measured through an objective lens, and the variation of the reflected light is detected by a photodetector to determine the displacement of the object to be measured. In the imaging type displacement meter for detection, a second light source that emits light of visible wavelength;
means for superimposing a light beam emitted from the light source as a guide beam on the same optical axis as the detection beam and irradiating the object to be measured, and detecting the guide beam contained in the reflected light reflected from the object to be measured; An imaging type displacement meter characterized by comprising means for separating the beam from the beam. 2. The arrangement according to claim 1, wherein the means for separating the guide beam and the detection beam is a changeover switch that instructs only one of the first light source and the second light source to emit a light beam. Image type displacement meter. 3. Claim characterized in that the means for separating the guide beam and the detection beam is a wavelength filter or a wavelength filter prism disposed between the position where the guide beam and the detection beam are superimposed and the photodetector. 1. The imaging type displacement meter according to 1. 4. The imaging type displacement meter according to claim 1, wherein the second light source is connected to the displacement meter via a detachable optical fiber. 5. The imaging type displacement meter according to claim 1, wherein the second light source uses a light emitting diode. 6. The guide beam superimposed on the detection beam forms an image on the objective lens side from the focus of the objective lens of the displacement meter, and a screen is provided on the outer periphery of the objective lens to receive the reflected light of the guide beam. The imaging type displacement meter according to claim 1. 7. The imaging type displacement meter according to claim 6, characterized in that the screen is composed of a light receiver equipped with a photoelectric conversion element, and the screen is divided in the circumferential direction and/or the radial direction. 8. The guide beam consists of at least three light beams independent of each other, and the intersection of the three light beams with a plane perpendicular to the optical axis of the detection beam at a position before entering the objective lens forms a triangle. The imaging type displacement meter according to claim 1, characterized in that: 9. The light beam emitted by the first light source is reflected by a polarizing beam splitter and irradiated onto the object to be measured as a detection beam, and the reflected light is incident on a photodetector via the polarizing beam splitter and reflected by the photodetector. An imaging type displacement meter that detects displacement of an object to be measured based on fluctuations in light, characterized in that a condensing lens and a concave lens are provided on the optical axis between the polarizing beam splitter and the photodetector. Imaging type displacement meter. 10. The imaging type displacement meter according to claim 9, wherein the condenser lens is provided between the objective lens and the polarizing beam splitter. 11. The imaging type displacement meter according to claim 1, further comprising a condenser lens and a concave lens provided on the optical axis between the objective lens and the photodetector.