JPS60161523A - Three-dimensional measuring machine - Google Patents

Abstract

PURPOSE:To enhance measuring accuracy, by forming a main scale from glass and providing a disturbance preventing layer for absorbing light transmitting the non-reflective part of said scale to prevent the same from reflecting to the side of an index scale. CONSTITUTION:A main scale 11 having reflective parts 15A and non-reflective parts 15B formed thereto in a checkered pattern and an index scale 12 having light pervious parts 16A and light impervious 16B formed thereto in a checkered pattern are arranged in parallel so as to keep a minute interval therebetween in a state relatively movable to each other, and a light emitting element 17 and a light receiving element 18 are provided in the side of the index scale 12 and the relative moving displacement amount of both scales 11, 12 are detected by both elements to perform three-dimensional measurement. In this measuring machine, a disturbance preventing layer 22 is provided to the rear surface side of the main scale 11 and light transmitting the non-reflective part 15B of the main scale 11 is prevented from reflecting to the side of the index scale 12. Therefore, no noise is generated in the light receiving element 18 and the detection of displacement can be performed with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a three-dimensional measuring machine, and more particularly, to an improvement in a displacement detection device for a three-dimensional measuring machine.

[Technical field] A measuring element supported movably in three axes orthogonal to each other is brought into contact with a measuring point, and displacement amounts of the measuring element in each of the three axial directions are set in each of the three axial directions. 2. Description of the Related Art Coordinate measuring machines that measure the dimensions, shape, etc. of a measurement location by detecting with a displacement detector are used in a wide range of industrial fields.

In such a coordinate measuring machine, the performance of the displacement detection device as well as its mechanical structure have a great influence on the measurement accuracy. Displacement detection devices are selectively used depending on the purpose.

By the way, when adopting an optical type as a displacement detection device,
Mainly due to space constraints, a long main scale is attached to the stationary side of the measuring machine, while a short index scale is attached to the moving side, and the two scales are arranged to move relative to each other. Generally, a so-called reflection type optical displacement detection device in which a light receiving element is disposed on the index scale side is employed.

Conventionally, when adopting a reflective displacement detection device, a metal scale was often used as the main scale, but in the case of a metal scale, a coordinate measuring machine is required to perform extremely high-precision measurements. In addition, since there has been a recent demand for larger sizes, the following problems have arisen.

That is, (1) It is difficult to finish a parallel and smooth plane with high precision, which may adversely affect the checkered pattern. In particular, this tends to occur when the main scale is long. This also causes significant distortion when the main scale is long. ■
When the mounting surface of the main scale is a stone surface plate or the like, the expansion coefficients of metal and stone are significantly different, which tends to cause distortion in the main scale over time. ■Since the checkered stripes are provided using an etching method, side etching becomes large and cannot be ignored in terms of accuracy.

Therefore, by making the main scale made of glass,
Although these problems could be overcome, the following new problems occurred in this case.

In other words, in the reflective type, the amount of change in reflected light due to reflection from the checkered stripes on the main scale is detected by a light receiving element, but when the main scale is made of glass, the amount of change in reflected light due to reflection from the checkered stripes on the main scale is detected, but when the main scale is made of glass, the amount of change in reflected light due to reflection from the checkered stripes on the main scale is detected. For example, light is reflected by a material on the back side of the main scale (anti-index scale side), and this reflected light is also received by the light receiving element. The influence on the light receiving element due to the reflection of light that has passed through the non-reflective area (this is referred to as disturbance) is due to the state on the back side of the main scale, that is, when the light that has passed through the non-reflective area is reflected. The state of the reflective surface when (optical properties), and as a result, the S/N ratio may be varied in various ways, which may adversely affect measurement accuracy.

By the way, in a three-dimensional measuring machine, the X-axis direction is detected on a stone surface plate, the Y-axis direction is detected on a stainless acid guide member, and the X-axis direction is detected on a guide member made of other materials. It is common practice to install the main scales of displacement detection devices on the spindle. Therefore, if a glass main scale is used, even if the same displacement detection device is installed on the same coordinate measuring machine, Differences in the optical properties of the scale attachment locations cause variations in the intensity and mode of the reflected light, which requires special adjustment on the light receiving element side.

Further, the optical properties of each attachment point may change over time, and in such a case, even if special adjustments are made, accuracy will deteriorate. Moreover, it is often unclear how to make adjustments depending on the optical properties of the attachment location, and in such cases, it is impossible to make adjustments.

[Object of the Invention] An object of the present invention is to provide a three-dimensional measuring machine that has excellent measurement accuracy, especially when the entire device is enlarged.

[Structure of the Invention] Therefore, the present invention employs a so-called reflection type optical displacement detection device as a displacement detection device in each axis direction, and makes the main scale of the device made of glass, and the non-reflective portion of the device is made of glass. By providing a disturbance prevention layer that absorbs light and does not reflect it to the index scale side, or changes the reflected light to a certain level and reflects it to the index scale side, the light that has passed through the non-reflective part of the checkered stripes on the main scale can be absorbed. This method eliminates the need for special adjustment on the light-receiving element side by preventing it from affecting the light-receiving element, or the reflected light is always constant even when the light transmitted through the non-reflective part is reflected and received by the light-receiving element. In this way, the special adjustment on the light-receiving element side is always constant, and in any case, fluctuations in reflected light due to differences in optical properties at the attachment point of the main scale are prevented, and thereby, the above-mentioned It is an attempt to achieve a goal.

[Explanation of Examples] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment of a coordinate measuring machine according to the present invention. The three-dimensional measuring machine has a circular frame 2 on the upper surface of a surface plate L serving as a base, and a slider 4 extending in the front-rear direction (Y-axis direction) of the surface plate L, and a slider 4 along a horizontal beam 3 of the circular frame 2. Slider 4 in the left-right direction (X-axis direction) of the surface plate l
A probe shaft 6 having a measuring element 5 is provided so as to be movable in the vertical direction (X-axis direction) of the surface plate I, respectively. In other words, the measuring head 5 is moved in three axial directions (three-dimensional directions) that are orthogonal to each other.
It is set up so that it can be moved freely. Further, between the surface plate 1 and the gate-shaped frame 2, an optical displacement detection device 10 as a Y-axis direction position detection device for detecting the amount of displacement of the circular frame 2 in the Y-axis direction is installed. An optical displacement detection device 10 serving as an X-axis direction position detection device for detecting the amount of displacement of the slider 4 in the X-axis direction is provided between the slider 4 and the slider 4, and a probe is provided between the slider 4 and the probe shaft 6. Optical displacement detection device l as an X-axis direction position detection device that detects the amount of displacement of the shaft 6 in the X-axis direction
These detecting devices 10 automatically detect the amount of displacement of the measuring stylus 5 in the x, y, and z axis directions, and display them on a display (not shown), respectively.

FIG. 2 shows the internal structure of the optical displacement detection device IO, and in the figure, the long main scale 11 and the short index scale 12° are both made of glass, and both scales 11.12° are made of glass. are arranged so as to be relatively movable in the longitudinal direction of the main scale 11 while maintaining a small parallel interval. Furthermore, the main scale 11 is fixed to a stationary body A, while the index scale 12 is fixed to a moving body B. Here, in the relationship between the surface plate l and the circular frame 2, the constant m1 is the stationary body A, and the gate-shaped frame 2 is the moving body B. Further, in the relationship between the horizontal beam 3 of the gate-shaped frame 2 and the slider 4, the horizontal beam 3 is the stationary body A, and the slider 4 is the moving body B. Furthermore, regarding the relationship between the slider 4 and the probe shaft 6, the slider 4 is a stationary body A, and the probe shaft 6 is a moving body B.

On the front surface of the main scale 11 (the side surface on the index scale 12 side), checkered stripes 15 are formed by vapor deposition along the longitudinal direction of the main scale 11.
are reflective portions 15A and non-reflective portions (i.e., areas where reflective portions 15A are not deposited) 15B having the same width and arranged alternately.
It is composed of.

On the other hand, a lattice stripe 16 is also formed on the index scale 12, and this lattice stripe 16 consists of a transparent portion 16A and a non-transparent portion 16B.
, and the pitch width of both plaid stripes is 15.16 (plaid stripes)
are made equal to each other. Note that by providing two lattice stripes 16 of the index scale 2 shifted by a quarter pitch, the directionality of the index scale 12 can be identified.

A light emitting element 17 and a light receiving element 18 are disposed at a predetermined position on the index scale 12 side in the slider 14, and the light irradiated from the light emitting element 17 onto the lattice stripes 16 of the index scale 12 at a predetermined angle is transmitted through the lattice stripes 16. After passing through the section 16A, it is reflected at the main scale 11,
Again, the transparent part 1 of the checkered stripes 16 of the index scale 12
6A and is received by the light receiving element 18. A signal processing device 19 and a display device 20 are connected to the light receiving element 18, and after the displacement amount (light amount displacement) of the reflected light detected by the light receiving element 18 is processed by the signal processing device 19, it is displayed in the display device 2o. It is displayed as a relative displacement amount of both scales 11 and 12.

A glass plate 21 different from the main scale 11 is closely arranged on the back side of the main scale 11 (opposite the index scale 12 side), and the main scale 11 is attached to the main body 13 via this glass plate 11. .

A disturbance prevention layer 22 is provided on the side surface of the glass plate 21 on the main scale ll side. This disturbance prevention layer 22 is formed from a thin film of a light absorbing material deposited on the side surface of the glass plate 21 or a thin film of a light reflecting material. If the layer is made of a light absorbing material, the non-reflective portion 15B of the main scale 11 is If the material absorbs the transmitted light and does not cause reflected light to be reflected on the index scale 12, the non-reflective portion 15B is made of a light reflective material.
The index scale 12 converts the transmitted light into a constant reflected light (not affected by the material etc. on the main body 13 side).
It is designed to be reflected to the side.

According to this embodiment, the following effects can be achieved.

High-precision machining is easy, there is little change over time and there is no distortion during installation, so even if the coordinate measuring machine is large, the main scale 11 will not be distorted and high-precision measurement will be possible. It is possible.

Furthermore, since the disturbance prevention layer 22 is disposed on the back side of the main scale 11 (the side opposite to the index scale 12), the light that has passed through the non-reflective portion 15B of the checkered stripes 15 of the main scale 11 is not reflected to the index scale 12 side. Alternatively, it is reflected to the index scale 12 side as constant reflected light (with known properties). Therefore, no noise is generated in the light receiving element 18, or by performing a certain quantitative correction in the signal processing device 19, accurate (high precision) displacement detection can be performed at all times. That is, the stationary body A is the attachment point of the main scale 11.
The measured value is not influenced by the optical properties of the side.

Furthermore, since it is only necessary to attach the main scale 11 to the stationary body A via the glass plate 21 provided with the disturbance prevention layer 22, attachment is easy.

In addition, when carrying out the implementation, the checkered stripes 15 of the main scale 11
may be provided on the side of the stationary body A (the side opposite to the index scale 12) (see FIG. 4). In this case, the stationary body A
This has the effect that when the main scale ti is deformed, the effect of expansion and contraction on the main scale ti is low. Alternatively, the disturbance prevention layer 22 may be directly deposited on the back side of the main scale 11 (see FIG. 5), or the disturbance prevention layer 22 may be formed directly on the stationary body A side, and then the main scale A scale 11 may be attached (FIG. 6). In these cases, the influence of the glass plate 21 on the expansion and contraction of the pitch of the checkered stripes 15 of the main scale 11 is small.

Furthermore, the disturbance prevention layer 22 is made of a light-absorbing material such as a black paint film or a synthetic resin, or a light-reflecting material such as a metal vapor-deposited film with a small reflectance. In order to make the prevention layer 22 uniform in thickness, it is desirable that the main scale 11 be brought into close contact with the attachment location.

Furthermore, the displacement detection devices attached in each axial direction are not necessarily limited to being the same.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a three-dimensional measuring machine that has excellent measurement accuracy, and particularly has excellent measurement accuracy even when the entire device is enlarged.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the overall configuration of an embodiment of the coordinate measuring machine according to the present invention, FIG. 2 is an enlarged perspective view showing the internal structure of the optical displacement measuring device in the embodiment, and FIG. FIGS. 4 to 6 are cross-sectional views showing the main scale and index scale of the optical displacement detection device, and FIGS. 4 to 6 are cross-sectional views showing the main scale and index scale in other embodiments different from each other. A... Stationary body, B... Moving body, l... Surface plate, 2.
...gate frame, 3...horizontal beam, 4...slider, 5...measuring head, 6...probe axis, 10...
・Optical displacement detection device, 11...Main scale, 1
2... Index scale, 15.16... Plaid stripes, 15A... Reflective part, 15B... Non-reflective part, 16
A... Transparent part, 16B... Non-transparent part, 17... Light emitting element, 18... Light receiving element, 19... Signal processing device, 20... Display device, 21... Glass plate, 22...
- Disturbance prevention layer. Agent Patent attorney Minoru Kinoshita (and 1 other person) Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] (1) A main scale having lattice stripes in which reflective parts and non-reflecting parts are arranged alternately, and an index having lattice stripes in which transparent parts and non-transparent parts are arranged in alternating order. The scale and the scale are arranged so as to be movable relative to each other, and a light emitting element and a light receiving element are arranged on the index scale side, and the light emitted from the light emitting element passes through the index scale, is reflected by the main scale, and returns to the index scale. Light is transmitted through the scale and received by the light receiving element, and the measuring head is movable in three mutually orthogonal axes directions by an optical displacement detection device that detects the amount of relative movement of both scales based on the amount of displacement of this light. In a three-dimensional measuring machine that measures the dimensions, shape, etc. of a measuring point by detecting the amount of displacement in each of three axial directions of a measuring point when brought into contact with a measuring point, the main scale is made of glass, and A three-dimensional measuring machine characterized by being equipped with a disturbance prevention layer that absorbs light transmitted through the non-reflective portion and does not reflect it toward the index scale side, or changes it into a constant reflected light and reflects it toward the index scale side. (2. A three-dimensional measuring machine according to claim 1, characterized in that the disturbance prevention layers of the displacement detection devices in the three axial directions are formed from the same material. (3) Patent A three-dimensional measuring machine according to claim 1 or 2, wherein the disturbance prevention layer is formed from a thin film of a light-absorbing material. (4) Claim 1 Alternatively, the three-dimensional measuring machine according to item 2, wherein the disturbance prevention layer is formed from a thin film of a light-reflecting material.