JP2975743B2 - Optical touch probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-focus type optical touch probe, and more particularly, to detecting a side surface of a hole or a groove suitable for use as a non-contact probe when attached to a coordinate measuring machine or the like. The present invention relates to an optical touch probe capable of changing the working distance of an objective lens.

[0002]

2. Description of the Related Art For example, a contact type probe and a non-contact type probe are known as a touch probe of a coordinate measuring machine.

[0003] Among them, the contact type probe is mainly used,
It is disadvantageous for a soft object or an object to be measured which is not desired to be scratched with a mirror surface.

On the other hand, as a non-contact type probe, there is an optical type probe using a triangulation method, but an object to be measured having a mirror surface cannot be detected, only one direction can be detected, the probe is large, and a contact which outputs a touch signal is provided. There was a problem that the measurement software for the probe was not usable and the software became dedicated.

On the other hand, as an in-focus type optical touch probe, an astigmatism method, a critical angle method, a Foucault method and the like are conventionally known.

[0006] Further, the applicant has filed a Japanese Patent Application No. Hei.
5711) proposes an optical touch probe of the pinhole method using two pinholes.

As shown in FIG. 4, a semiconductor laser (LD) 10 as a light source, a polarization beam splitter 14 for reflecting light emitted from the semiconductor laser 10 toward a measurement surface 12, A collimator lens 16 for converting the light whose traveling direction has been changed by the polarization beam splitter 14 into a parallel beam, and a light beam 18 parallelized by the collimator lens 16 are condensed on the measurement surface 12 to form a light spot 22. Objective lens 20 for forming
To prevent the scattered and reflected light from the measurement surface 12 from returning to the semiconductor laser 10 and the polarization beam splitter 14
In combination with the above, a quarter-wave plate 24 for increasing the efficiency compared to the case where a half mirror is used, an imaging lens 26 for forming an image of the reflected light passing through the polarizing beam splitter 14, A beam splitter 28 for splitting the light passing through the imaging lens 26, and the beam splitter 2
8, two apertures (pinholes) 30 arranged before and after the in-focus position of each reflected light divided by 8
A, 30B, two light receiving elements (for example, photodiodes) 32A, 32B for detecting the amount of reflected light passing through the apertures 30A, 30B, respectively, and each light receiving element 3
Current for converting the output currents of 2A and 32B into voltages-
Voltage (IV) converters 40A and 40B and an amplifier 4 for amplifying the output voltage of each of the IV converters 40A and 40B
2A and 42B, a difference calculator 44 for calculating the difference between the outputs of the amplifiers 42A and 42B, a sum calculator 46 for calculating the sum of the outputs of the amplifiers 42A and 42B, and the difference calculator 44
Is divided by the output of the sum calculator 46 to generate an S-curve displacement signal.

Assuming that the reflected light amount is Q0, the light amount of (1/2) Q0 is directed to the transmission side (front pin side) and the reflection side (rear pin side) of the beam splitter 28, respectively.

As shown in FIG. 5, the radius of the laser beam at the position of the stop 30A on the front pin side is defined as wa, and the radius of the laser beam at the position of the stop 30B on the rear focus side is defined as wb. Where 1 / e ² of the intensity distribution) and the radius of the stop is r, the light quantity Q passing through the stop
a (front pin side) and Qb (rear pin side) are respectively expressed by the following equations.

Qa = (1/2) Q0 × [1-exp {-2 (r / wa) ² }] (1) Qb = (1/2) Q0 × [1-exp {-2 (r / wa) wb) ² ｝]… (2)

Therefore, the displacement signal S is expressed by the following equation.

S = (Qb−Qa) / (Qb + Qa) = [exp {−2 (r / wa) ² } −exp {−2 (r / wb) ² }] / [2-exp} −2 ( r / wa) ² {-exp {-2 (r / wb) ² )}] (3)

As is apparent from the equation (3), the displacement signal S has no relation to the amount of reflected light Q0.

Now, the output of each light receiving element 32A, 32B is
As shown in FIG. 6, the displacement signal S obtained at that time becomes an S-shaped curve substantially similar to the conventional one, as shown in FIG. 7, and a displacement signal corresponding to the displacement of the measurement surface 12 is obtained. Can be.

Therefore, the zero cross point of the displacement signal is captured,
If a trigger output circuit 50 for generating a trigger output indicating that the measurement surface 12 has come to the focal position of the objective lens 20 is provided, a touch signal can be obtained as in the case of the contact probe. Therefore, for example, in a coordinate measuring machine, if the value of the scale is read by this touch signal,
The displacement of the measurement surface can be detected.

According to such an in-focus type optical touch probe, a touch signal is output at the same timing as that of a conventional contact type touch probe. Software can be used as is.

Further, since the focusing system is used, non-contact measurement can be performed on any of a mirror surface and a scattering surface.

[0018]

However, the optical touch probe proposed by the applicant in Japanese Patent Application No. Hei 2-130961 (Japanese Patent Application Laid-Open No. Hei 4-25711) can only detect a measurement surface in one direction. Also, the distance between the objective lens and the measurement surface when the touch signal is output (referred to as the working distance of the objective lens) cannot be changed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide an optical touch probe capable of detecting a measurement surface in a plurality of directions separately for each direction. I do.

[0020]

According to the present invention, there is provided an optical touch probe of a focusing system, wherein a touch signal is generated when a measurement surface comes to a focal position of an objective lens of a probe for irradiating a light beam. Light beam splitting means for splitting a beam in a plurality of directions, a plurality of light beams split by the light beam splitting means, a plurality of objective lenses for irradiating a measurement surface in each of the split directions, A polarizing means for changing a light beam into a different polarization state for each branching direction is provided, and the measurement surface in the plurality of directions can be distinguished and detected for each direction to achieve the above object.

Further, the light beam is applied to the measurement surface at a different timing for each branch direction.

[0022]

According to the present invention, a light beam splitting means for splitting a light beam applied to a measurement surface into a plurality of directions,
A plurality of objective lenses for irradiating a plurality of light beams branched by the light beam branching means to a measurement surface in each branch direction, and a plurality of objective lenses for setting the light beam to a different polarization state in each branch direction. Since the polarizing means is provided, the measurement surfaces in the plurality of directions can be detected separately for each direction.

Further, when the light beam is applied to the measurement surface at different timings for each branching direction, the measurement surfaces in the plurality of directions can be detected substantially simultaneously.

[0024]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention applied to an optical touch probe according to the pinhole method proposed in Japanese Patent Application Laid-Open No. 30961/1992 will be described in detail.

The first embodiment of the present invention, as shown in FIG.
Collimator lens 16, imaging lens 26, beam splitter 28, diaphragms 30A and 30B, light receiving element 32
A, 32B, IV converters 40A, 40B, amplifiers 42A, 42B, difference operator 44, sum operator 46,
FIG. 4 includes a divider 48 and a trigger output circuit 50.
In an optical touch probe similar to the above, a light beam 18 converted into a parallel light beam by the collimator lens 16 is used.
Are split in different polarization states (for example, the transmission direction is S-polarization and the reflection direction is P-polarization) for each of the splitting directions, and a plurality of light beams 18Z split by the polarizing beam splitter 60. A plurality of objective lenses 12Z and 12Y for irradiating the measurement surfaces 12Z and 12Y with the light beam
Z-direction semiconductor laser 1 for generating S-polarized light for causing Z and 18Y to have different polarization states for each branch direction.
Semiconductor laser 10 for Y direction that generates 0Z, P polarized light
Y, a polarizing beam splitter 62 that transmits S-polarized light and reflects P-polarized light for combining the light of the semiconductor lasers 10Z and 10Y, and a quarter-wave plate 24Z, Y for Z direction.
To reflect the reflected beams from the Z-direction measurement surface 12Z and the Y-direction measurement surface 12Y, which are combined by the polarization means including the directional quarter-wave plate 24Y and the polarization beam splitter 60, in the direction of the imaging lens 26. Mirror 64.

The position of the collimator lens 16 is
Unlike the probe of FIG. 4, it is provided between the polarization beam splitters 62 and 60.

The other configuration and the basic operation are the same as those of the probe shown in FIG. 4, so that the detailed description will be omitted.

In this embodiment, when measuring the inside such as the inside diameter and the groove width of the hole of the object to be measured, as shown in FIG. 1, the light beams 12Z and 12Y are irradiated in the Z direction and the Y direction. , Not only the measurement surface 12Z in the Z direction, but also the measurement surface 12Y in the Y direction, so that the measurement can be performed efficiently.
Further, if the two-way probe is mounted on a rotatable probe head, the inner diameter and groove width of the hole can be measured. On the other hand, conventionally, only the measurement in the Z direction is performed.
It was necessary to change 0 °. Further, when the probe does not enter the hole or the like of the object to be measured, it is difficult to measure in the Y direction.

The light beam is split into a plurality of directions,
Even when only a plurality of objective lenses for irradiating the measurement surface with the plurality of branched light beams for each branch direction are provided, the surface to be measured can be detected in two directions. However, if the light beam cannot be identified,
Since it is not known in which direction the measurement surface was detected, when measuring the inner diameter of the hole or groove width, etc., near the bottom surface of the hole or groove, even if you want to measure the side surface, the bottom surface is detected incorrectly and touched. May output a signal. or,
For narrow holes and grooves, the reverse is also possible.

On the other hand, in the present embodiment, two semiconductor lasers 10Z and 10Y are used, and the polarization directions are S, respectively.
Since the polarization beam splitters 62 and 60 and the quarter-wave plates 24Z and 24Y are combined so as to be polarized light and P-polarized light, the light beam 1 having a different polarization state for each branching direction is provided.
8Z and 18Y can be generated.

Therefore, for example, when it is desired to detect only in the Z direction, only the semiconductor laser 10Z for the Z direction is turned on so that the S-polarized light beam 18Z is irradiated on the measurement surface 12Z in the Z direction. By turning off the light, only the Z direction can be accurately detected.

Conversely, when it is desired to detect only in the Y direction, only the Y direction semiconductor laser 10Y is turned on so that the P-polarized light beam 18Y is irradiated on the Y direction measurement surface 12Y.
The direction semiconductor laser 10Z is turned off.

Next, a second embodiment of the present invention will be described in detail.

In the second embodiment, as shown in FIG. 2, the same Z-direction semiconductor laser 10Z and Y
Direction semiconductor laser 10Y and polarization beam splitter 62
, A collimator lens 16 and a polarizing beam splitter 6
0, a quarter-wave plate 24Z for the Z direction, and a quarter for the Y direction
Wave plate 24Y, Z-direction objective lens 20Z, Y-direction objective lens 20Y, mirror 64, imaging lens 26
, A beam splitter 28, apertures 30A and 30B,
Light receiving elements 32A, 32B and IV converters 40A, 40
B, a difference operator 44, a sum operator 46, and a divider 48
And an optical touch probe including a trigger output circuit 50, an oscillator 70, a timing circuit 72 for generating a necessary timing signal in accordance with an output of the oscillator 70, and a timing circuit 72 in accordance with an output of the timing circuit 72. A laser drive circuit 74 for alternately turning on the Z-direction semiconductor laser 10Z and the Y-direction semiconductor laser 10Y at different timings, and the IV converter in synchronization with a timing signal output from the timing circuit 72. 40A, 40
B, respectively, for detecting the outputs of B and outputting them to the difference calculator 44 and the sum calculator 46, respectively.
In accordance with the output of the sum calculator 46 and the output of the timing circuit 72, it is determined which of the light beams is illuminated when there is a light amount signal, and as a result (Z direction,
A light amount discriminating circuit 78 for outputting an identification signal indicating the Y direction)
It is provided with.

The other structure and basic operation are the same as those of the first embodiment, so that detailed description will be omitted.

In the present embodiment, the irradiation timings of the two semiconductor lasers 10Z and 10Y are shifted, and irradiation is performed at different timings as shown in FIG. It can be determined by determining whether or not light is received.

In each of the above embodiments, since the two lasers correspond one-to-one in the two directions, the power loss is small and the measurement on the measurement surface with a low reflectance can be performed.
It is enough.

In each of the above embodiments,
Although the pinhole method using two pinholes was used as the focusing method, the detection method is not limited to this, and other focusing methods such as the astigmatism method, the critical angle method, and the Foucault method are used. You may.

In each of the above embodiments, the beam splitter 28 includes the imaging lens 26 and the diaphragm 30A,
30B, the beam splitter 28
Is not limited to this, and it may be provided between the imaging lens 26 (which requires two lenses) and the polarization beam splitter 14.

[0040]

As described above, according to the present invention, measurement surfaces in a plurality of directions can be separately detected for each direction, and the inside of a hole, such as an inner diameter and a groove width, can be measured.

In the case where the light beam is applied to the measurement surface at different timings for each branching direction, the measurement surfaces in the plurality of directions can be detected substantially simultaneously.

[Brief description of the drawings]

FIG. 1 is an optical path diagram including a partial block diagram showing a configuration of a first embodiment of an optical touch probe according to the present invention.

FIG. 2 is an optical path diagram including a partial block diagram showing the configuration of a second embodiment.

FIG. 3 is a diagram illustrating an example of irradiation timing of a semiconductor laser in a second embodiment.

FIG. 4 is a diagram showing an example in which the applicant filed Japanese Patent Application No. 2-130961.
FIG. 4 is an optical path diagram including a partial block diagram for explaining the operation principle of the optical touch probe according to the pinhole method proposed in Unexamined Japanese Patent Publication No. 4-25711) .

FIG. 5 is a diagram showing a light amount of a light beam passing through a diaphragm in the optical touch probe.

FIG. 6 is a diagram showing an example of an output of the light receiving element in the same manner.

FIG. 7 is a diagram showing an example of the relationship between the displacement of the measurement surface and the displacement signal.

[Explanation of symbols]

 10Z, 10Y: semiconductor laser, 12Z, 12Y: measuring surface, 16: collimator lens, 18Z, 18Y: light beam, 20Z, 20Y: objective lens, 26: imaging lens, 28: beam splitter, 30A, 30B: stop, 32A, 32B: light receiving element, 60, 62: polarizing beam splitter, 64: mirror, 70: oscillator, 72: timing circuit, 74: laser driving circuit, 76A, 76B: synchronous detector, 78: light quantity discriminating circuit.

Claims (2)

(57) [Claims] 1. A touch signal is generated when a measurement surface comes to a focal position of an objective lens of a probe that irradiates a light beam.
In a focusing type optical touch probe, a light beam branching unit for branching the light beam in a plurality of directions, and a plurality of light beams branched by the light beam branching unit are measured for each of the branching directions. A plurality of objective lenses for irradiating the light beam, and a polarizing unit for changing the light beam into a different polarization state for each branch direction, and the measurement surfaces in the plurality of directions can be detected separately for each direction. An optical touch probe, characterized in that: 2. The optical touch probe according to claim 1, wherein the light beam is applied to the measurement surface at different timings in each of the branch directions.