JP3326682B2 - Displacement measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement measuring device for measuring a displacement of a surface to be measured by using triangulation with light, and to a technique for improving the displacement detection accuracy and the measuring speed. .

[0002]

2. Description of the Related Art When measuring the height displacement (irregularity) of a surface to be measured by using light, as shown in FIG. 5, a laser beam is irradiated from a light projector 5 onto a surface 1a of an object 1 to be measured. A displacement measuring device using a triangulation method in which the image of the point S is formed on the light receiving surface 7a of the light receiving element 7 by the image forming lens 6 is used.

The light receiving element 7 is configured to output a signal corresponding to the vertical position of the image forming point on the light receiving surface 7a, and to output the signal in the height direction of the irradiation point S (light of the beam of the projector 5). The light receiving surface 7a is arranged at an angle that coincides with the movement trajectory of the imaging point K with respect to a displacement (in-plane direction formed by the axis and the optical axis of the imaging lens 6).

The object 1 to be measured is moved relative to the displacement measuring device in a direction orthogonal to a plane formed by the optical axis of the beam of the projector 5 and the optical axis of the imaging lens 6, and the irradiation point S is set to S. ′
Alternatively, when the light-receiving element 7 moves in the height direction as shown in S ", the position of the image-forming point K on the light-receiving surface 7a of the light-receiving element 7 moves as K 'or K", and the signal from the light-receiving element 7 also becomes the image-forming point. It changes according to the displacement of. The displacement in the height direction of the measurement target surface can be detected from the amount of change in the signal.

However, since the mechanism for moving the measurement object 1 relative to the displacement measuring apparatus is usually a low-speed mechanism driven by a motor or the like, the measurement is performed at a fine pitch over the entire surface of the measurement object 1. Then, the measurement time becomes very long.

For this reason, in recent years, by using a scanning type displacement measuring device as shown in FIG. 6, measurement is performed by moving only one of the X-axis direction and the Y-axis direction among the movements of the object to be measured. I can do it. This scanning type displacement measuring device deflects a beam output from a light source 11 within a certain angle range by a deflecting device 12 such as a vibrating mirror type, and deflects the deflected beam by a lens 13 so that its optical axis is in one plane. The reference plane 2
The light is emitted to the upper surface 1a of the measurement object 1, and its irradiation point S is linearly reciprocally scanned or one-way scanned, and the image of the irradiation point S is converted into a first cylindrical lens (cylindrical lens) 14.
Then, an image is formed on the light receiving surface 16a of the light receiving element 16 by the second cylindrical lens 15.

[0007]

However, in the conventional scanning displacement measuring apparatus using a cylindrical lens in the light receiving section as described above, the surface to be measured has a high reflectivity like a mirror surface and is located from the irradiation point S. This is not a problem when most of the light is light parallel to the reflection axis. However, when the light from the irradiation point S is scattered and spreads because the surface to be measured is rough and the reflectance is low, the light receiving element There is a problem that the image on the surface is blurred and the measurement accuracy is significantly reduced.

That is, the cylindrical lens basically has a convergence property only in the circumferential direction of the cylindrical surface of the lens, and has no convergence property in other directions. Therefore, as shown in FIG. To
Of the light reflected and scattered at the irradiation point S, the light spread in the circumferential direction of the cylindrical surface of the first cylindrical lens 14 is focused by the first cylindrical lens 14 and enters the second cylindrical lens 15. The light receiving surface 1 of the light receiving element 16 is
The light receiving surface 1 is deflected toward the center in the width direction of the light receiving surface 6a.
7A, an image K is formed on the first cylindrical surface lens 14 of the light reflected and scattered at the irradiation point S as shown in FIG.
The light that spreads in the axial direction of the cylinder of the first cylindrical lens 1
In No. 4, since the light is incident on the second cylindrical lens 15 while being spread without being converged at all, the light receiving surface 16a of the light receiving element 16
The upper image K is a straight line extending in the width direction of the light receiving surface 16a.

In addition, the image of the irradiation point is converted to a first image having a short focal length.
Of the light-receiving element 16 due to the aberration of the cylindrical lens 14.
The image formation pattern on the light receiving surface 16a is blurred in a horizontally long oval shape as shown in FIG. 8, the S / N of the signal output from the light receiving element 18 is reduced, and the displacement of the measurement surface is highly accurate. Can not be measured with

It is an object of the present invention to solve this problem and to provide a displacement measuring device capable of performing high-accuracy measurement at high speed even when the surface to be measured is rough and light from an irradiation point is spread. .

[0011]

In order to achieve the above object, a displacement measuring apparatus according to the present invention emits a beam whose optical axis moves parallel to a predetermined range on the same plane to a surface to be measured.
A light projection unit that scans an irradiation point of the beam on the surface to be measured,
Receiving light from an irradiation point on the surface to be measured, forming an image of the irradiation point on the light receiving surface of the light receiving element, and outputting a signal corresponding to the light imaging position on the light receiving surface of the light receiving element. A displacement measuring device having a light receiving unit and measuring a displacement of the measurement target surface along a scanning direction of the irradiation point based on a signal output from the light receiving element, wherein the light receiving unit has an outer dimension of A plurality of spherical focusing lens units each having a focal length smaller than the scanning width of the beam are formed in a line in a state where respective optical axes are parallel and continuous on a line orthogonal to the optical axis, In the direction where the optical axis of each of the condenser lenses intersects with the irradiation point scanned on the surface to be measured, the light axis is disposed at a position where the distance to the irradiation point is substantially equal to the focal length. Which are focused by the respective condenser lens units. An array, and a spherical focusing device that focuses a beam focused by each focusing lens unit of the lens array on a light receiving surface of the light receiving element and forms an image of an irradiation point on a measurement target surface on the light receiving surface. A type imaging lens.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 are views showing the configuration of a displacement measuring device according to one embodiment of the present invention.

In FIG. 1, a light projecting unit deflects a laser beam output from a light source 21 by a deflecting device 22 such as a rotating mirror type or a vibrating mirror type. A predetermined range (for example, 3
0 mm), the beam whose optical axis moves in parallel
The light is emitted to the upper surface 1a of the measurement object 1, and the measurement object 1
The beam irradiation point S on the surface 1a is scanned linearly (actually, meandering due to irregularities on the surface of the object to be measured) in a one-way or reciprocating manner.

The light receiving section for receiving the light from the irradiation point includes a lens array 25, an imaging lens 26, and a light receiving element 27.

The lens array 25 has the same focal length f1
(For example, 20 mm) (5 in FIGS. 1 and 2)
Are integrally formed of synthetic resin or glass so that the condensing lens portions 25a to 25e are arranged in a line.

Each condensing lens section has a width at least along the direction in which it is arranged shorter than the scanning width (for example, 6 mm) so that a plurality of condensing lens sections are arranged within the scanning width dimension (30 mm) of the beam emitted from the light projecting section. It has a substantially rectangular outer shape, and is a spherical focusing type in which one surface orthogonal to the optical axis is formed in a spherical shape, and each optical axis is parallel and continuous on a line orthogonal to the optical axis. It is integrated in a state where the side surfaces are in close contact with each other so as to be arranged in a line.

The lens array 25 has a direction in which the optical axis of each condensing lens section intersects with an irradiation point scanned on the surface 1a of the measuring object 1, and the distance to the irradiation point is substantially equal to the focal length f1. Is located in the position. Here, the spherical focusing lens is a lens that can uniformly squeeze light around its optical axis.

For this reason, when the amount of displacement of the irradiation point in the height direction is much smaller than the focal length f1, the condenser lenses 25a to 25e converge and converge the light from the irradiation point almost in parallel. The light exits to the image lens 26.

The imaging lens 26 has a diameter larger than the scanning width (30 mm) of the beam emitted from the light projecting unit.
One surface orthogonal to the optical axis is formed in a spherical shape, and is formed of a spherical focusing lens having a focal length f2 of, for example, 80 mm, and focuses a beam from the lens array 25 to form a light receiving surface of a light receiving element 27. An image of the irradiation point is formed on the image 27a.
The imaging lens 26 is arranged so that its optical axis coincides with the optical axis of the condensing lens portion 25c at the center of the lens array 25. Although the outer shape of the imaging lens 26 is shown as a circle in FIGS. 1 and 2, it may be a shape obtained by cutting out only a portion corresponding to a range where light from the lens array 25 is incident.

The light receiving element 27 has a rectangular light receiving surface 27a, and outputs a signal corresponding to a position along the vertical direction of the light receiving surface 27a among the positions of the light irradiated on the light receiving surface 27a. Have been. The lateral width of the light receiving surface 27a is equal to the width of each of the condenser lenses 25a to 25e of the lens array 25 and the ratio f2 / f1 of the focal length of each of the condenser lenses and the imaging lens 26.
The magnification is multiplied by (magnification) (for example, as described above, the width of the condensing lens portion is 6 mm and the magnification is 4 when the width is 24 mm). The center of the light receiving surface 27a of the light receiving element 27 is An imaging point which intersects the optical axis of the imaging lens 26 at a position away from the imaging lens 26 by a focal distance f2 and moves with the displacement of the surface 1a of the measurement object 1 in the height direction is a light receiving surface 27a. It is arranged so that it moves vertically in the upper direction.

Note that the optical axis of the beam from the light projecting section and the optical axis of the lens array 25 of the light receiving section have the same angle, ie, positive angle, across the normal of the reference plane 2 in order to secure the amount of received light. The direction is set in advance so as to be the direction of reflection.

Next, the operation of this displacement measuring device will be described with reference to FIGS.
It will be described based on. FIG. 3 is a diagram of the light receiving unit viewed from above in a direction orthogonal to the optical axis of the imaging lens 26, and FIG. 4 is a diagram of the light receiving unit viewed from the side in a direction in which the optical axis of the imaging lens 26 is horizontal. .

The irradiation point S of the beam emitted toward the measuring object 1 on the reference surface 2 is scanned in a fixed direction on the reference surface 2 and the surface 1a of the measuring object 1.

Here, the irradiation point S of the beam is, for example, as shown in FIG.
As shown in (a), when the light is reflected outside and scattered from the irradiation point S when the light beam is outside the optical axis in a range facing the light collecting lens portion 25a of the lens array 25, the light is mainly emitted from the light collecting lens portion 25a. Are focused into substantially parallel beams, and enter the imaging lens 26 at an angle to the optical axis thereof.

The imaging lens 26 converges the beam from the condenser lens portion 25a, changes the direction of its optical axis, and converges the beam at a position on one end side of the light receiving surface 27a of the light receiving element 27.

Each of the condensing lens portions and the imaging lens 26 of the lens array 25 is a spherical converging type lens that converges light around its optical axis evenly, so that as shown in FIG. The light scattered from the irradiation point S when viewed from the side is also focused substantially parallel by the condenser lens portion 25a, and
6 converges on the light receiving surface 27a of the light receiving element 27.

For this reason, on the light-receiving surface 27a of the light-receiving element 27, a point-like image K is placed at a position exactly corresponding to the height of the irradiation point S.
is generated, and an electric signal corresponding to the position is output.

This signal is input to a signal processing unit (not shown), and the height from the reference plane 2 to the irradiation point S is detected.

It should be noted that the other condensing lens unit 25 is located
Weak light incident on b to 25e is also focused and formed into an imaging lens 2
6 are incident on the light receiving surface 2 of the light receiving element 27.
No image is formed on 7a.

The irradiation point S is set by
As shown in FIG. 3B, when the light reaches the position intersecting with the optical axis of the condenser lens section 25a of the lens array 25, the light reflected and scattered from the irradiation point S is mainly emitted from the condenser lens section 25a.
Is focused into a beam parallel to the optical axis, and enters the imaging lens 26 in a state parallel to the optical axis.

For this reason, the image Ka of the irradiation point S is formed substantially at the center of the light receiving surface 27a of the light receiving element 27 in the width direction.

As shown in FIG. 3C, the beam is further scanned so that the irradiation point S is within a range opposing the converging lens portion 25a of the lens array 25, and the converging lens portion adjacent to the optical axis thereof. When it is near 25b, the light reflected and scattered from the irradiation point S is mainly focused by the condenser lens portion 25a,
The light enters the image forming lens 26 at an angle opposite to that in the case of FIG.

For this reason, the imaging lens 26 includes the light receiving element 2
7 at a position on the other end side of the light receiving surface 27a in the width direction of the light receiving surface 27a.
Make a.

As described above, when the position of the irradiation point S moves from one end to the other end within the range facing the condenser lens portion 25a, the position of the image Ka on the light receiving surface 27a of the light receiving element 27 becomes
The light receiving surface 27a moves from one end in the width direction to the other end.

When the irradiation point moves by δ in the height direction (normal direction of the reference plane 2) as shown in FIG. 4B, for example, as shown in FIG. The position of the image on the light receiving surface 27a of the element 27 is shifted like K ', a signal corresponding to the position is output, and the height of the irradiation point S' from the reference plane 2 is detected from this signal, S
The difference δ from the height is also known.

Then, as shown in FIG. 3D, when the irradiation point S comes to a position facing the boundary between the condensing lens portion 25a and the converging lens portion 25b, the light from the irradiation point S becomes ,
Since the two condensing lens portions 25a and 25b converge into substantially parallel beams and enter the imaging lens 26, images Ka and Kb are formed at both ends of the light receiving surface 27a of the light receiving element 27 in the width direction. These two imaging points Ka, K
Since the positions along the vertical direction of the light receiving surface 27a are the same, a signal corresponding to the position in the vertical direction is output from the light receiving element 27 as in the case of one image.

The beam is further scanned, and FIG.
As shown in (2), when the irradiation point S moves within a range opposed to the condenser lens portion 25b, the light reflected and scattered from the irradiation point S is mainly focused by the condenser lens portion 25b, and is focused on the imaging lens 26. On the other hand, the light is incident on the optical axis at an angle, and the imaging lens 26 forms a point image Kb at one end of the light receiving surface 27a of the light receiving element 27 in the width direction.

Similarly, while the irradiation point S is scanned within a predetermined range (here, 30 mm), the image K on the light receiving surface 27a of the light receiving element 27 is equal to the number of the condensing lens portions of the lens array 25. While moving from one end to the other end in the width direction by the number of times, it moves in the vertical direction in accordance with the displacement of the height of the surface 1a of the measurement target 1, and the height of the surface 1a of the measurement target 1 A signal corresponding to the displacement is output, and the displacement of the surface to be measured can be measured based on the signal.

As described above, in the displacement measuring apparatus according to the embodiment, the irradiation point is formed by the lens array in which the plurality of spherical focusing type condensing lens units are arranged in a row in parallel with the beam scanning direction of the light projecting unit. Is focused into a substantially parallel beam, and this beam is focused on a light receiving surface of a light receiving element in a point-like manner by a spherical focusing type imaging lens.

Therefore, even when the surface of the object to be measured is rough, the image on the light receiving surface of the light receiving element is not spread and blurred, and a highly accurate displacement measurement can be performed.

The diameter 1 is larger than the beam scanning range.
A light receiving element having a smaller light receiving surface width can be used as compared with a method in which light from an irradiation point is converged almost in parallel by only two spherical focusing type condensing lenses and emitted to the imaging lens 26. In other words, it is known that the response speed of this type of light receiving element becomes slower as the width thereof is larger, so that light from the irradiation point is focused by a plurality of small condenser lenses as described above. With this configuration, a light-receiving element with a small width of the light-receiving surface and a high response speed can be used, and the scanning speed can be increased to increase the processing speed for signals from the light-receiving element, thereby shortening the measurement time. Becomes

In the above embodiment, five condensing lens portions 25a to 25e are provided for a beam scanning range of 30 mm.
Is used, but this does not limit the present invention. For example, a condensing lens portion having a smaller outer shape (for example, 2 mm in width) is more (for example, 15 mm in width).
The width of the light-receiving surface of the light-receiving element can be further reduced by reducing the width of the condensing lens portion in this way, and the processing speed for a signal output from the light-receiving element can be further increased. Can be raised.

The width of the light receiving element can be reduced by reducing the ratio f2 / f1 of the focal length f1 of each condenser lens portion to the focal length f2 of the imaging lens 26. When the distance f2 is reduced, the aberrations worsen,
When the focal length f1 of the condenser lens unit is increased, the amount of received light decreases. Therefore, the outer shape, focal length, and the like of each lens may be determined according to the state of the surface to be measured, the accuracy required for measurement, and the like.

Further, the lens array 25 of the above embodiment is used.
Although a plurality of condenser lenses were integrally formed of synthetic resin or glass, a plurality of individually produced condenser lenses may be bonded together to be integrated. They may be arranged in a line without any gap.

In the above embodiment, the lens array 2
Although each of the condensing lens units 5 and the imaging lens 26 is a spherical focusing lens whose one surface is actually formed in a spherical shape, light is evenly converged around its optical axis. Any lens can be used as long as it is a spherical focusing type lens that can perform such operations, and a lens having both spherical surfaces or aspheric surfaces may be used.

[0046]

As described above, in the displacement measuring apparatus according to the present invention, a plurality of spherical focusing type condensing lens portions capable of uniformly squeezing light around the optical axis thereof are parallel to the beam scanning direction. The light from the irradiation point is converted into a substantially parallel beam by a lens array arranged in a row, and this beam is focused on a light receiving surface of a light receiving element by a spherical focusing type imaging lens.

Therefore, even when the surface of the object to be measured is rough, the image of the irradiation point on the light-receiving surface of the light-receiving element does not spread and is blurred, and the light-receiving surface has a small width and a high response speed. Can be used, and highly accurate displacement measurement can be performed at high speed.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of the present invention.

FIG. 2 is a side view of the embodiment.

FIG. 3 is a view of the light receiving unit according to the embodiment viewed from above in a direction orthogonal to the optical axis thereof.

FIG. 4 is a side view of the light receiving unit according to the embodiment in a direction in which its optical axis is horizontal.

FIG. 5 is a principle diagram of displacement measurement using light.

FIG. 6 is a perspective view showing a configuration of a conventional scanning displacement measuring device.

FIG. 7 is a diagram for explaining the operation of the conventional device.

FIG. 8 is a diagram showing an imaging pattern of a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Light source 22 Deflection device 23 Lens 25 Lens array 25a-25e Condensing lens part 26 Imaging lens 27 Light receiving element 27a Light receiving surface

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 G01C 3/06

Claims (1)

(57) [Claims] 1. A light projecting unit which emits a beam whose optical axis moves in a predetermined range in parallel on the same plane to a surface to be measured, and scans an irradiation point of the beam on the surface to be measured, and a surface to be measured. A light receiving unit that receives light from the upper irradiation point, forms an image of the irradiation point on the light receiving surface of the light receiving element, and outputs a signal corresponding to an image forming position of light on the light receiving surface of the light receiving element; A displacement measuring device that measures displacement of the measurement target surface along a scanning direction of the irradiation point based on a signal output from the light receiving element, wherein the light receiving unit has an outer dimension of scanning the beam. A plurality of converging spherical converging lens units having a smaller focal length and a smaller focal length are formed in a row with their optical axes parallel and continuous on a line perpendicular to the optical axis. The optical axis of the optical lens part is set to the irradiation point where it is scanned on the surface to be measured. A lens array that is disposed at a position where the distance to the irradiation point is substantially equal to the focal length in the intersecting direction, and that focuses light from the irradiation point by each of the condensing lens units; A spherical focusing type imaging lens that focuses the beam focused by the lens unit on a light receiving surface of the light receiving element and forms an image of an irradiation point on a measurement target surface on the light receiving surface. Displacement measuring device characterized by the above-mentioned.