JPS61102510A - Noncontact probe - Google Patents

Abstract

PURPOSE:To obtain a probe which is easy to produce and has no oscillation source by providing an objective with a parallel optical system between its light transmitting lens and image-forming lens. CONSTITUTION:A couple of light transmission optical systems 3 and 4 which have optical axes in parallel to the optical axis of the common objective 2 are provided. Namely, the 1st light transmission optical system 3 consists of the 1st light transmitting lens 5 arranged right behind the lens 2, the 2nd light transmitting lens 6 arranged behind it, and a light emitting diode 7 placed at the composite rear focus position of the lenses 5 and 6. The 2nd light transmission optical system 4 also consists of the 1st light transmitting lens 8, the 2nd light transmitting lens 9, and a light emitting diode 10 similarly to the optical system 3. Thus, the parallel optical system is constituted among the lens 2 and lenses 5 and 8, and image-forming lens 11. Therefore, even if there is an error in lens position, the respective optical systems are easily adjusted and semiconductor light emitting elements are used as a light sourc;e and driven electrically by turns to project two light beams on a surface to be measured alternately, so there is no movable part such as a chopper, thereby taking a measurement with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a non-contact probe that can optically measure the position of a measurement surface by contact.

(Details of the Invention) This type of non-contact probe is described in the Proceedings of the 1985 Spring Conference of the Japan Society of Precision Machinery Engineers, pages 839 to 840. That is, two beams are emitted from the He-Ne laser onto the measurement surface placed in front of the objective lens, symmetrically with the optical axis of the objective lens, and intersecting at one point on the optical axis of the objective lens.
The structure is such that an optical image position detector placed behind the objective lens determines the image interval between the two beams reflected on the measurement surface, and this image interval corresponds to the position of the measurement surface. . According to this, when the object plane is located at the intersection of the two light beams, the image interval becomes zero, and as the object plane shifts back and forth, the image interval increases.Here, the two light beams are chopped When intermittent alternately by
Since each image position is reversed at the intersection position of the two light beams, the direction of the shift can be determined from this.

Furthermore, if the measurement plane is perpendicular to the optical axis of the objective lens, the two images will be generated symmetrically to the optical axis, but if the measurement plane is tilted, the image position will shift in the direction perpendicular to the optical axis depending on the tilt. become. Therefore, the inclination of the measurement surface can be determined from this amount of deviation.

However, with the above-mentioned device, it is difficult to adjust the three optical axes of the two transmitting optical systems and the receiving optical system so that they intersect at one point, and because a He-Ne laser is used as the light source, Since a chopper is used to alternately project the light beam onto the measurement surface, there are problems such as an increase in size and vibration of the chopper causing erroneous measurements.

(Objective of the Invention) An object of the present invention is to solve these drawbacks and provide a non-contact probe that is small and lightweight, does not contain a vibration source, and is easy to manufacture.

(Summary of the Invention) The present invention provides a common objective lens for a light transmitting optical system and at least one pair of light receiving optical systems, and a parallel optical system between the objective lens, the light transmitting lens, and the imaging lens. This eliminates the trouble of adjusting the optical system, and by using semiconductor light emitting elements such as light emitting diodes and semiconductor lasers as the light source of each of the light receiving optical systems, and driving these light sources alternately electrically, the chopper This eliminates the need for moving parts.

(Example) Fig. 1 shows a head of a non-contact probe according to a first embodiment of the present invention, and Fig. 2 is an electric circuit diagram used together with the head of Fig. 1, in which the non-contact probe is used together with the head. Configure.

A common objective lens 2 is fixed to one end of a cylindrical frame 1 forming the outer shape of the head, and a pair of light transmission optical systems 3.4 having optical axes parallel to the optical axis of the common objective lens 2 are installed. It is provided behind the common objective lens 2 symmetrically with respect to its optical axis. The first light transmitting optical system 3 includes a first light transmitting lens 5 placed immediately after the common objective lens 2, a second light transmitting lens 6 placed behind the first light transmitting lens 5, and a first light transmitting lens 6 placed behind the first light transmitting lens 5. It is composed of a light lens 5 and a light emitting diode 7 placed at a focus measurement position after combining the light lens 5 and the second light transmitting lens 6. The second light transmitting optical system 4 is also
Just like the light transmitting optical system 3, the first light transmitting lens 8. It is composed of a second light transmission lens 99 and a light emitting diode 10. An imaging lens 11 is located behind the common objective lens 2,
A light-receiving element 12 for detecting the position of the optical image is disposed at the post-measuring focus position of the imaging lens 11. The light receiving element 12 is a frame that is a position detector (PSD) that outputs a voltage signal according to an X coordinate value (the X coordinate is perpendicular to the optical axis and in a direction within the plane of the paper) corresponding to the position of the optical image. Near the other end of the body 1, pins 13 and 14 are provided for adjusting the position of the light receiving element 12.

As shown in FIG. 1, if the measurement surface 15 is located at the front focal plane of the common objective lens 2, then the light emitting diode 7,
The light emitted from the IO enters the second light transmitting lens 6.9, exits the first light transmitting lens 5.8, becomes a parallel light beam, and enters the common objective lens 2. Since the optical axes of the first light transmitting optical system 3 and the second light transmitting optical system 4 are parallel to the optical axis of the common objective lens 2, the light emitted from the common objective lens 2 is transmitted onto the measurement surface 15 and also through the common objective lens. The light is focused on the optical axis of 2. That is, the front focal position of the common objective lens 2 becomes conjugate to the light source 7.10, the images of the light source 7.10 overlap at the front focal position, and the reflected light from the measurement surface 15 enters the common objective lens 2 and becomes parallel light. After that, it enters the imaging lens 11 and the light receiving element 12
If the shape of the light-emitting surface of the light-emitting diode 7.10 is made circular with the same diameter, the center position of the reflected image on the light-receiving element 12 when the light-emitting diode 7 is turned on and the light-emitting diode 10 is turned on. The center position of the reflected image on the light-receiving element 12 is the same as the center position of the reflected image on the light-receiving element 12 when If the light emitting diode 7 is turned on, if it moves in the direction of moving away,
The position of the reflected image on the light-receiving element 12 shifts in the cloth direction in the plane of the paper (in the positive direction of the X coordinate if the above-mentioned position is the origin), and when the light-emitting diode 10 is turned on, the position of the reflected image on the light-receiving element 12 shifts. The position shifts to the left in the paper (in the negative direction of the X coordinate if the above-mentioned position is the origin), and the amount of shift corresponds to the amount of movement of the measurement surface 15. On the other hand, measurement surface 1
5 moves in the optical axis direction of the common objective lens 2, in the direction approaching the common objective lens 2, the direction of displacement of the position of the reflected image on the light receiving element 12 is opposite to that described above.

Alternate lighting of the light emitting diodes 7 and IO is performed by a well-known two-phase oscillator 16, as shown in FIG. The position signal from the light receiving element 12 is a voltage signal corresponding to the X coordinate value. For the sake of simplicity, it is assumed that a circuit (not shown) is adjusted so that when the measurement surface 15 is at the front focal position of the common objective lens 2, a zero voltage indicating the origin is output from the light receiving element 12. do. The output signal of the light receiving element 12 is input to a first sample and hold circuit 17 and a second sample and hold circuit 18. The first sample and hold circuit 17 is.

A signal that drives the light emitting diode 10 of the two-phase oscillator 16 is input as a sampling signal, and the light emitting diode
The output signal of the light receiving element 12 when O is lit is sampled and held. On the other hand, the second sample hold circuit 1
Reference numeral 8 inputs a signal for driving the light emitting diode 7 of the two-phase oscillator 16 as a sampling signal, and samples and holds the output signal of the light receiving element 12 when the light emitting diode 10 is lit.

Note that if the output signal of the light receiving element 12 is sampled and held at the rising edge of the signal that drives the light emitting diode 7, the desired signal may not necessarily be sampled and held, so the output signal of the two-phase oscillator 16 is delayed by about two periods. A more stable sampling signal can be obtained by providing a delay circuit between the two-phase oscillator 16 and the sample and hold circuits 17 and 18, and determining the rising edge of the output signal as the sampling signal. Coordinate signal corresponding to the position from sample hold circuit 17°18
X! .

X, is input to the arithmetic circuit 19 and a predetermined arithmetic operation is performed. Now, as shown in FIG. 1, if the angle at which the optical axis of the first light transmitting optical system 3 and the optical axis of the second light transmitting optical system 4 intersect is α, then the front focal point of the common objective lens 2 is The position Z in the optical axis direction based on the position is +'Xz Z = -tan (90-α/2) -filX
, -X.

It can be found as In response to a command to find a position Z (not shown), the arithmetic circuit 19 performs the fi1 calculation, and as shown in FIG. 15 is tilted, the tilt angle θ is X, -X.

...(2) It can be obtained as follows. In FIG. 4, the optical axis of the first light transmitting optical system 3 is 3', the optical axis of the second light transmitting optical system 4 is 4', and the image of the light emitting diode 7 generated on the measurement surface 15 is 7'0. An image of the light emitting diode 10 is shown at 10'. (The calculation circuit 19
performs the calculation of equation (2). The calculation results by the calculation circuit 19 are displayed on the display device 20.

To explain the operation shown in FIG. 2 with reference to the time chart shown in FIG. 3, the two-phase oscillator 16 outputs the signals shown in FIG. The light receiving element 12 emits light at a high level.
As shown in figure (c), the coordinate signal of the reflected image when the light emitting diode 7 is lit! , and the coordinate signal x8 of the reflected image when the light emitting diode 10 is turned on are output alternately. 1st
The sample and hold circuit 17 holds the coordinate signal x2 as shown in FIG. 3(N), and the second sample and hold circuit 18 holds the coordinate signal x1 as shown in FIG. 3(D). Constant α introduced in advance
and the coordinate signal XI+Xt using equation (1) or equation (
2), the calculation by the calculation circuit 19 is an analog calculation, but the coordinate signal XI+X! It is also possible to perform digital calculations after performing A and -D conversion.

Note that a semiconductor laser may be used instead of the light emitting diode 7.10 used in the above explanation, and these elements that are small and can be turned on and off at high speed are referred to as semiconductor light emitting elements. In addition, as the light receiving element 12, in addition to a position detector (PSD) that obtains an analog signal corresponding to the coordinate position, a two-split photodiode, a charge-coupled device (COD), etc.
etc. can be used. However, the detection range of the two-split photodiode is narrow.

In the above explanation, the first light transmitting optical system and the second light transmitting optical system are arranged symmetrically with respect to the optical axis of the light receiving optical system, but the optical axis of the first light transmitting optical system and the second light transmitting optical system are arranged symmetrically. As long as the optical axes of the second light transmitting optical system are parallel to the optical axis of the light receiving optical system, they do not need to be symmetrical.

In other words, even in such a case, there is a one-to-one correspondence between the position of the optical image on the light-receiving element and the measurement surface, so it is necessary to know the amount of deviation in advance. can be done without any problems.

Further, a pair of light transmitting optical systems are further disposed in a plane including the optical axis of the light receiving optical system and perpendicular to the plane of the paper of FIG. 1, with the optical axis sandwiched therebetween. If considered in the same way as the second light transmitting optical system 4, the position and angle of the measurement surface 15 in the direction perpendicular to the paper plane of FIG. 1 can be measured.

As described above, two-dimensional measurement can be performed by sequentially driving the light emitting diodes of the four light transmitting optical systems by the four-phase oscillator and sample-holding the signals from the light receiving elements.

Furthermore, the air circuit may be built into the rad, or it may be led to the outside of the head with a cord and made separate.

Next, referring to FIG. 5, the probe of the second embodiment of the present invention will be explained. The structure of the probe head shown in FIG. 5 is almost the same as that of the previous embodiment, but a reflecting mirror 21 tilted at 45 degrees with respect to the optical axis is disposed at the tip of the common objective lens 2. This embodiment is suitable for measuring a surface substantially perpendicular to the optical axis, whereas this embodiment is suitable for measuring a surface substantially parallel to the optical axis.

If a probe head is attached to the tile axis of a measuring device (not shown) so as to be rotatable around its optical axis, it becomes possible to easily measure a cylindrical axis or hole whose axis is parallel to the optical axis.

In addition, if the reflector 21 is configured to be detachable from the probe head body using a clamp or the like,
It can be applied to both parallel measurement surfaces.

(Effects of the Invention) As described above, according to the present invention, since a parallel optical system is used between the common objective lens, the light transmitting lens, and the imaging lens, even if there is an error in the position of each lens, each optical axis is Intersect at the focus of a common objective lens. Therefore, adjustment of the optical system is extremely easy. In addition, since a semiconductor light emitting element is used as the light source and is electrically driven alternately to project two light beams onto the measurement surface, the device can be made smaller and lighter, and since it does not include any moving parts, it can be made more expensive. Accuracy can be measured.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the head of a non-contact probe according to the first embodiment of the present invention, Fig. 2 is an electric circuit diagram used with the head and 2 of Fig. 1, and Fig. 3 is an electric circuit diagram of Fig. 2. A time chart for explaining the operation of the circuit diagram, FIG. 4 is an explanatory diagram when the measurement surface 15 is inclined, and FIG. 5 is a sectional view of the head of a non-contact probe according to the second embodiment of the present invention. , is. (Explanation of symbols of main parts) 1...Frame body, 2...Common objective lens, 3.4...Light transmission optical system, 7, lO...Light emitting diode, 11...Imaging lens , 12... Light receiving element, 16... Two-phase oscillator, 17.18... Sample hold circuit, 19... Arithmetic circuit.

Claims (1)

[Claims] an objective lens; and at least one pair of light transmission optical systems having an optical axis that is parallel to the optical axis of the objective lens and sandwiching the optical axis of the objective lens, and that is disposed in a peripheral area behind the objective lens. and a semiconductor light emitting element disposed at the post-focusing position of the light transmission optical system, and a semiconductor light emitting element arranged behind the objective lens and between the pair of light transmission optical systems, which corresponds to the optical axis of the objective lens. an imaging lens disposed with an optical axis, and a light receiving element for detecting a light image position disposed at a post-focusing position of the imaging lens;
a driving means for selectively driving the pair of semiconductor light emitting elements; and a driving means for driving one of the semiconductor light emitting elements by inputting an output signal of the light receiving element in synchronization with the driving of the semiconductor light emitting elements. calculation means for calculating the position of the measurement surface in front of the objective lens by performing a predetermined calculation using the output signal of the light receiving element and the output signal of the light receiving element when the other of the semiconductor light emitting elements is driven as measured values; A non-contact probe comprising: a frame that includes at least the objective lens, the pair of light transmitting optical systems, the semiconductor light emitting element, the imaging lens, and the light receiving element to constitute a head. .