JP2005207915A - Displacement measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement measuring instrument for rapidly measuring the amount of displacement of an object under measurement with the instrument itself simplified. <P>SOLUTION: This displacement measuring instrument is characterized by being equipped with a light source 3, an objective lens 6 for condensing light from the light source 3 to irradiate it to the object 2 under measurement, a condensing lens 7 for condensing reflected light reflected from the object 2 and passing through the objective lens 6, an optical path changing means 20 having at least one reflective surface 20a for changing the optical path of outgoing light from the condensing lens 7, a light receiving element 8 for receiving outgoing light from the changing means 20, a reflective surface changing means 21 for periodically changing the optical path by changing at least one of the position or installation angle of the reflective surface 20a, and a displacement amount calculation means 9 for calculating the displacement amount of the object 2 by finding an optical path length at least from the condensing lens 7, via the reflective surface 20a, up to the receiving element 8, based on an output of the receiving element 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a displacement measuring apparatus for measuring an object to be measured in a non-contact manner.

  Conventionally, there are various devices for measuring an object to be measured. Among these devices, the following devices for measuring an object to be measured in a non-contact manner are known. That is, as shown in FIG. 8, a light source 103 that irradiates light toward the object to be measured 102, a collimator lens 104 that collimates the light emitted from the light source 103, and the light emitted from the collimator lens 104 is collected. An objective lens 105 that emits light and irradiates the object to be measured 102 is provided. Further, these devices collect a beam splitter 106 that changes the optical path of the reflected light from the object 102 to be measured, and a light that is collected by the light splitter 106 that collects the light changed by the beam splitter 106 and that has a pinhole 107. An optical lens 110 and a light receiving element 109 that receives light transmitted through the pinhole 107 are provided (see, for example, Patent Document 1).

  In such a configuration, when light is emitted from the light source 103, the light is collimated by the collimator lens 104, and the collimated light enters the beam splitter 106. Part of the incident light passes through the beam splitter 106 and enters the objective lens 105. Then, the light is condensed by the objective lens 105 and the measured object 102 is irradiated with the light. The light reaching the object to be measured 102 is reflected there, and this reflected light is transmitted again through the objective lens 105 and the optical path is changed by the beam splitter 106. The light passes through the pinhole 107 and then reaches the light receiving element 109, and the light intensity is detected by the light receiving element 109.

Here, when the objective lens 105 is moved in the optical axis direction, the light intensity detected by the light receiving element 109 changes depending on the position of the objective lens 105. In other words, the detected light intensity varies depending on the relative distance between the objective lens 105 and the object to be measured 102, and when the relative distance between the two becomes equal to the focal length of the objective lens 105, the light is imaged on the light receiving element 109. The light intensity is maximized. By obtaining the position of the objective lens 105 at the maximum, the surface position of the object to be measured 102 can be measured.
JP 2000-74621 A

  However, according to the configuration as described above, the objective lens 105 needs to be moved with high accuracy, so that there is a problem that the measurement speed cannot be increased and the configuration of the apparatus itself is complicated.

  The present invention has been made to solve such a problem, and provides a displacement measuring device that can quickly measure the amount of displacement of an object to be measured and can simplify the configuration of the device itself. It is intended to provide.

In order to solve the above problems, the present invention provides the following means.
The invention according to claim 1 is directed to a light source that irradiates light to the object to be measured, an objective lens that collects light from the light source and irradiates the object to be measured, and reflects the object from the object to be measured and the objective. A condenser lens for condensing the reflected light transmitted through the lens, an optical path changing means having at least one reflecting surface for changing an optical path of the outgoing light from the condenser lens, and receiving the outgoing light from the optical path changing means And at least one of the condensing elements based on the output of the light receiving element, the reflecting surface variable means for periodically changing the optical path by changing at least one of the position or the installation angle of the reflecting surface. Displacement amount calculating means for calculating a displacement amount of the object to be measured by obtaining an optical path length from the lens to the light receiving element via the reflection surface.

  According to the displacement measuring apparatus according to the present invention, when light is irradiated from the light source to the object to be measured, the light is condensed by the objective lens and irradiated to the object to be measured. The irradiated light reaches the object to be measured and is reflected there. The reflected light passes through the objective lens again and is collected by the condenser lens. The light emitted from the condenser lens is changed in its optical path by the reflecting surface of the optical path changing means, and reaches the light receiving element. When the light receiving element detects the light, it converts it into an electrical signal and outputs it as light intensity information.

Here, since at least one of the position and the installation angle of the reflection surface is periodically changed by the reflection surface variable means, the arrival point at which the light reflected from the reflection surface reaches the light receiving element. Changes. That is, the optical path length from the condensing lens to the light receiving element via the reflecting surface periodically changes. Therefore, the light is imaged at one point on the arrival point where the optical path length is equal to the focal length of the objective lens and the condenser lens. At this time, the detected light intensity becomes maximum. Therefore, in the displacement measuring apparatus according to the present invention, the displacement amount calculation means causes the light intensity to reach the light receiving element from at least the condenser lens through the reflecting surface when the light intensity becomes maximum based on the output of the light receiving element. The optical path length is calculated, and the displacement amount of the object to be measured is calculated from the optical path length.
Thereby, since the reflecting surface is changed by the reflecting surface variable means without moving the objective lens, the displacement amount of the object to be measured can be calculated quickly and easily, and the apparatus itself can be configured more simply. It becomes possible.

According to a second aspect of the present invention, in the displacement measuring apparatus according to the first aspect, the optical path changing means is a polygon mirror, and the reflecting surface varying means includes a rotation mechanism for rotating the polygon mirror. And
According to the displacement measuring apparatus according to the present invention, the light emitted from the light source enters the condenser lens in the same manner as described above. And the light radiate | emitted from the condensing lens reaches | attains the reflective surface of a polygon mirror, The optical path is changed toward a light receiving element by this reflective surface. At this time, since the polygon mirror is rotated by the rotating mechanism, the optical path length from the condenser lens to the light receiving element periodically changes. Therefore, in the same manner as described above, the displacement amount of the object to be measured is calculated by the displacement amount calculation means.
Thereby, the displacement amount can be measured more quickly and easily, and the configuration of the apparatus itself can be further simplified.

  According to a third aspect of the present invention, in the displacement measuring apparatus according to the second aspect, an angle formed between the radial direction of the polygon mirror and the at least one reflective surface is an angle formed between the radial direction and another reflective surface. It is characterized by being set differently.

According to the displacement measuring apparatus according to the present invention, the angle formed between the radial direction of the polygon mirror and the reflecting surface is reflected by the reflecting surface whose angle is set differently from the other, and the other reflecting surface. The arrival point on the light receiving element is different from the reflected light.
As a result, output information can be captured for each arrival point, and errors due to variations in the light receiving elements can be mitigated, enabling measurement with higher accuracy.

According to a fourth aspect of the present invention, in the displacement measuring apparatus according to any one of the first to third aspects, an fθ lens is installed on an optical path between the light receiving element and the reflecting surface. It is characterized by being.
According to the displacement measuring apparatus of the present invention, since at least one of the position of the reflecting surface or the installation angle is changed by the reflecting surface varying means, the light emitted from the condenser lens is reflected by the reflecting surface, and the reflection thereof. The light continuously enters the light receiving element while gradually changing the incident angle.

Here, as the incident angle to the light receiving element is further away from zero degree, the shape of the incident light at the arrival point becomes elliptical, and the detection error of the light receiving element increases accordingly. On the other hand, the closer the incident angle to the light receiving element approaches zero degrees, the closer to the perfect circle at the arrival point, the higher the accuracy of detection. In the displacement measuring apparatus according to the present invention, since the fθ lens is installed on the optical path between the light receiving element and the reflecting surface, the light incident on the fθ lens is incident on the light receiving element regardless of the incident angle. Therefore, the optical path is maintained so as to be vertical, and the incident angle to the light receiving element is always zero degrees.
Thereby, the shape formed by the light incident on the light receiving element is always a perfect circle, and high-precision light detection is possible.

  According to the present invention, it is possible to speed up the measurement of the displacement amount of the object to be measured and simplify the configuration of the apparatus itself.

(Example 1)
Hereinafter, a displacement measuring apparatus according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a state in which a workpiece, which is an object to be measured, is installed in a displacement measuring apparatus as a first embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a displacement measuring device, and reference numeral 2 denotes a workpiece.
This displacement measurement value 1 is approximately a laser diode (light source) 3 that emits laser light, a collimator lens 4 that makes the laser light emitted from the laser diode 3 parallel light, and an optical path of light emitted from the collimator lens 4. The half prism 5 that changes by 90 degrees is provided, and the work 2 is placed on the optical path changed by the half prism 5.

  In addition, the displacement measuring apparatus 1 condenses the laser light whose traveling direction is changed by the half prism 5 and transmits the objective lens 6 that irradiates the workpiece 2 toward the workpiece 2 and the objective lens 6 and the half prism 5. A condensing lens 7 that condenses the reflected light from the work 2, a linear image sensor (light receiving element) 8 that is provided in the vicinity of the condensing lens 7 and receives light emitted from the condensing lens 7, and a linear image sensor 8 is provided with a data processing unit (displacement amount calculation means) 9 for performing a predetermined calculation based on the output from 8. The linear image sensor 8 is provided with a light receiving surface having a plurality of pixels, converts light reaching each pixel into an electrical signal, and sequentially outputs this as light intensity information.

  In the displacement measuring apparatus 1 in the present embodiment, the objective lens 6 and the condenser lens 7 are fixed. Further, in the displacement measuring apparatus 1 in the present embodiment, a prismatic polygon mirror 20 having a regular octagonal cross section is installed on the optical path between the condenser lens 7 and the linear image sensor 8. The polygon mirror 20 includes eight reflecting surfaces 20a that reflect the laser light on its outer peripheral surface, and the light path from the condenser lens 7 is reflected by the reflecting surface 20a, thereby changing its optical path and reflecting the reflected light. The light reaches the linear image sensor 8.

  The polygon mirror 20 is rotatably supported by a rotating shaft (reflecting surface varying means, rotating mechanism) 21, and the arrival points when the light emitted from the polygon mirror 20 reaches the linear image sensor 8 are continuously provided. In order to change, the polygon mirror 20 is rotated at a constant cycle around the rotation axis 21. At this time, each reflecting surface 20a can always be moved along the same locus. Thereby, the optical path length from the condensing lens 7 to the linear image sensor 8 changes periodically.

The condenser lens 7, the polygon mirror 20, and the linear image sensor 8 are positioned and installed at predetermined intervals as will be described later.
Further, the data processing unit 9 obtains the reference optical path length L shown in FIG. 5 that is the focal length between the condenser lens 7 and the objective lens 6 based on the output from the linear image sensor 8 as described later. It has become. Further, a displacement distance T shown in FIG. 5 between the objective lens 6 and the surface of the workpiece 2 is calculated from the reference optical path length L.

Next, the operation of the displacement measuring apparatus 1 in the present embodiment configured as described above will be described.
First, the workpiece 2 as the object to be measured is mounted at a predetermined position, and from this state, the laser diode 3 is driven to irradiate the laser beam, and the rotary shaft 21 is driven to rotate the polygon mirror 20. Then, the laser light emitted from the laser diode 3 is converted into parallel light by passing through the collimator lens 4, and the light enters the half prism 5. The incident direction of the incident light is changed by approximately 90 degrees toward the workpiece 2 by the half prism 5. Then, this light is collected by being incident on the objective lens 6 and is irradiated toward the work 2. The irradiated light reaches the measurement point of the work 2 and is reflected there. The reflected light is transmitted again through the objective lens 6 and further through the half prism 5. Then, the light enters the condenser lens 7, is condensed by the condenser lens 7, and is irradiated toward the polygon mirror 20.

  The irradiated light reaches the reflection surface 20a of the polygon mirror 20 and is reflected there, thereby changing the traveling direction and reaching the linear image sensor 8. Here, since the polygon mirror 20 is rotating, the point at which the outgoing light from the condenser lens 7 first reaches the reflecting surface 20a is not determined, but the new reflecting surface 20a is formed by the rotation of the polygon mirror 20. When the light is first transmitted, as shown in FIG. 2, the emitted light reaches the end of the reflecting surface 20a, and the reflected light is an angle between the reflecting surface 20a and the optical axis N at this time. The predetermined position of the linear image sensor 8 corresponding to is reached.

Further, since the polygon mirror 20 continues to rotate, the reflection surface 20a is moved according to the rotation angle of the polygon mirror 20 as shown in FIGS. The angle with 20a is gradually changed. Therefore, the position where the emitted light from the condenser lens 7 reaches the reflecting surface 20a is continuously changed from the end of the reflecting surface 20a toward the other end. At the same time, since the angle between the optical axis N and the reflection surface 20a is gradually changed, the emission angle from the reflection surface 20a is also continuously changed. Therefore, the arrival point at which the light emitted from the reflecting surface 20a reaches the linear image sensor 8 continuously changes while drawing a constant locus according to the movement of the reflecting surface 20a.
Then, when the position where the light emitted from the condenser lens 7 reaches the reflection surface 20a passes the end of the reflection surface 20a, a new reflection surface 20a appears at the same time, and the above operation is repeated periodically.

Therefore, the optical path length from the condenser lens 7 to the linear image sensor 8 via the reflecting surface 20a changes according to the angle between the optical axis N and the reflecting surface 20a. Therefore, when the optical path length is shorter than the focal lengths of the condenser lens 7 and the objective lens 6, as shown in FIG. 2, the emitted light from the reflecting surface 20a does not form an image on the linear image sensor 8, that is, focus. It will be in a state that does not fit. Then, when the rotation of the polygon mirror 20 proceeds and the same focal length and the same optical path length become equal, the light emitted from the reflecting surface 20a forms an image on the linear image sensor 8 as shown in FIG. It becomes a state. At this time, the light intensity in the linear image sensor 8 becomes maximum. As the rotation further proceeds, as shown in FIG. 4, the arrival point moves in a state where the focus is not adjusted again.
A series of emitted light from end to end of the reflecting surface 20a is received by the linear image sensor 8 and output to the data processing unit 9 as light intensity information one by one.

  Here, as described above, since the arrival point to the linear image sensor 8 changes depending on the angle between the optical axis N and the reflection surface 20a, the optical path length from the condenser lens 7 to the linear image sensor 8 is reached. Is determined by the angle between the optical axis N and the reflecting surface 20a. In other words, each member is positioned and installed at a predetermined interval, and using the position data, the arrival point to the linear image sensor 8, that is, the position of the light receiving pixel on the light receiving surface of the linear image sensor 8. Therefore, the angle of the reflecting surface 20a is obtained. Therefore, the optical path length from the position of these light receiving pixels to the linear image sensor 8 from the condenser lens 7 can be calculated.

Therefore, the data processing unit 9 determines the reference optical path from the position on the light receiving surface of the pixel received at the time when the received light intensity becomes maximum, that is, when the optical path length matches the focal length of the condenser lens 7 and the objective lens 6. The length L is calculated. Furthermore, the displacement distance T of the workpiece 2 and the reference optical path length L are in an inversely proportional relationship as follows.
T = A / (LB) + C
(However, A, B, and C are constants depending on the characteristics of the objective lens 6 and the condenser lens 7)
Therefore, the data processing unit 9 calculates the displacement distance T from the reference optical path length L, and measures the displacement amount of the surface of the workpiece 2.

As described above, according to the displacement measuring apparatus 1 in the present embodiment, the displacement amount of the surface of the workpiece 2 is obtained by rotating the polygon mirror 20 instead of moving the objective lens 6. Can be measured.
Further, the device itself can be simply configured as compared with the case where the objective lens 6 is moved simply by rotating the polygon mirror 20.

(Example 2)
FIG. 6 shows the main part of the second embodiment of the present invention.
In FIG. 6, the same components as those shown in FIG.
This embodiment and the first embodiment have the same basic configuration, and differ in the following points.
That is, in the present embodiment, the reflecting surface 20a is set so that the virtual line M directed in the radial direction of the polygon mirror 20 and the reflecting region for reflecting the laser beam intersect at right angles on the outer peripheral surface of the polygon mirror 20. When, and a set reflecting surface 20b so as to intersect with an angle theta ₁ between the virtual line M and the reflective region are not perpendicular.

In such a configuration, when the workpiece 2 is placed at a predetermined position and the laser diode 3 is driven, the laser beam is irradiated from the condenser lens 7 toward the polygon mirror 20 by the same operation as in the first embodiment. Is done. In the present embodiment, since the setting angles of the reflecting surfaces 20a and 20b are different from each other, the arrival points to the linear image sensor 8 are different. Therefore, the pixels that receive the light in the linear image sensor 8 are different from each other. Then, each piece of information is output from the linear image sensor 8 based on the light emitted from the reflecting surfaces 20a and 20b, and the reference optical path length L is calculated by averaging the calculation results calculated from each piece of information. The amount of displacement is measured in the same manner as in the first embodiment.
As described above, the variation in the light receiving pixels is alleviated and the measurement can be performed with higher accuracy.

(Example 3)
FIG. 7 shows the main part of the second embodiment of the present invention.
In this embodiment, an fθ lens 22 is provided on the optical path between the reflecting surface 20 a of the polygon mirror 20 and the linear image sensor 8.
For this reason, even if the incident angle of the light applied to the fθ lens 22 gradually changes, the light is transmitted through the fθ lens 22, so that all the incident light is incident on the linear image sensor 8 perpendicularly.
As a result, the shape of the incident light to the linear image sensor 8 at the arrival point is always a perfect circle, and measurement can be performed with higher accuracy.

In the above embodiment, the polygon mirror 20 is provided, but a plate-like reflecting mirror may be used instead. At this time, the reflecting mirror is reciprocated along the incident direction when the light emitted from the condenser lens 7 enters the reflecting mirror, or the reflecting mirror is rotated in the same manner as in the above embodiment. If it does, the effect similar to the above can be acquired.
Furthermore, instead of the polygon mirror 20, a galvanometer mirror may be used.
In the above embodiment, the linear image sensor 8 is provided. However, the present invention is not limited to this, and other light receiving elements such as an area image sensor may be used. However, since the reading speed is increased, the linear image sensor 8 is better.

In the above embodiment, the reference optical path length L is obtained from the position of the pixel that the linear image sensor 8 receives. However, the present invention is not limited to this. For example, an angle detection sensor is provided in the vicinity of the reflection surface 20a. The reference optical path length L may be calculated from the angle information from and the light intensity information from the linear image sensor 8.
Note that the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

It is a schematic block diagram which shows the 1st Example of the displacement measuring apparatus which concerns on this invention. In the Example, it is a figure which shows the state in which the emitted light from a condensing lens reached | attained the linear image sensor, Comprising: It is explanatory drawing which shows a mode before the emitted light forms an image. In the Example, it is a figure which shows the state which the emitted light from a condensing lens reached | attained the linear image sensor, Comprising: It is explanatory drawing which shows a mode that the emitted light imaged. In the same Example, it is a figure which shows the state which the emitted light from a condensing lens reached | attained the linear image sensor, Comprising: It is explanatory drawing which shows a mode after the emitted light has imaged. It is explanatory drawing which shows each optical path in the Example. It is explanatory drawing which shows the principal part of the 2nd Example of the displacement measuring apparatus which concerns on this invention. It is explanatory drawing which shows the principal part of the 3rd Example of the displacement measuring apparatus which concerns on this invention. It is a schematic block diagram which shows the conventional displacement measuring apparatus.

Explanation of symbols

1 Displacement measuring device 2 Workpiece (object to be measured)
3 Laser diode (light source)
6 Objective lens 7 Condensing lens 8 Linear image sensor (light receiving element)
9 Data processing part (displacement amount calculation means)
20 Polygon mirror (light path changing means)
20a, 20b Reflecting surface 21 Rotating axis (Reflecting surface variable means, rotating mechanism)
22 fθ lens L Reference optical path length (optical path length)

Claims (4)

A light source for irradiating the object to be measured;
An objective lens that collects light from the light source and irradiates the object to be measured;
A condenser lens that condenses the reflected light reflected from the object to be measured and transmitted through the objective lens;
An optical path changing means having at least one reflecting surface for changing the optical path of the outgoing light from the condenser lens;
A light receiving element for receiving light emitted from the optical path changing means;
Reflecting surface variable means for periodically changing the optical path by changing at least one of a position or an installation angle of the reflecting surface;
A displacement amount calculating means for calculating a displacement amount of the object to be measured by obtaining an optical path length from at least the condenser lens to the light receiving element via the reflection surface based on the output of the light receiving element; A displacement measuring apparatus comprising: The optical path changing means is a polygon mirror,
The displacement measuring apparatus according to claim 1, wherein the reflecting surface varying unit includes a rotation mechanism that rotates the polygon mirror.   The angle formed between the radial direction of the polygon mirror and the at least one reflecting surface is set to be different from the angle formed between the radial direction and another reflecting surface. Displacement measuring device.   The displacement measuring apparatus according to claim 1, wherein an fθ lens is installed on an optical path between the light receiving element and the reflecting surface.

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