JP2009250676A - Distance measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distance measuring apparatus in which a probe part resists damage and is easy to be replaced. <P>SOLUTION: Light from a light source 2 is made to be a parallel light beam by a collimator lens 3 and is irradiated nearly perpendicularly on the inner wall of a hole 1 from an exit face 14. The scattered light is received by a micro aperture 15, is reflected by mirrors 17, 18 repeatedly, and is guided to a light receiving lens 4 to be received. The light received by the light receiving lens is imaged on a linear sensor 5. If a light receiving position on the linear sensor 5 is determined, the incident angle of the scattered light incident on the micro aperture 15 is determined, thereby allowing the distance from the exit face 14 to the inner wall of the hole 1 to be calculated on the basis of the principle of triangular surveying. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a distance measuring device.

  Conventionally, the shape of a hole by metal processing or the like has been measured using a check tool such as a caliper. However, a caliper or other inspection tool can measure only the narrowest of the contacted parts of the teeth, and is not sufficient for measuring the shape inside the hole.

  Therefore, inspection by a shape measuring machine using a contact type sensor such as a touch probe has been carried out. However, since it is a contact type, there is a problem that an error occurs due to wear or contact pressure of the contact. It was.

On the other hand, Japanese Patent Application Laid-Open No. 2007-285891 (Patent Document 1) irradiates a laser beam spreading in a disk shape inside a hole, images the position hitting the inside of the hole with a camera, and distance from the center thereof. There has been proposed a method of calculating.
JP 2007-285891 A

  However, when the probe is inserted into the hole and shape measurement is performed, especially when the probe is attached to a robot arm or the like, the inserted component easily collides with the inner wall of the hole. There is a problem that a probe having a complicated structure is damaged and cannot be measured.

  The present invention has been made in view of the above circumstances, and provides a distance measuring device that makes it difficult to damage the probe portion and allows easy replacement of the probe portion by simplifying the portion of the probe to be inserted. This is the issue.

A first means for solving the above-described problem is an illumination optical system for illuminating the object to be examined with illumination light that can be regarded as substantially point-like light on the surface of the object to be examined, through the emission aperture (A),
A light receiving opening (C) that is provided at a position away from the exit opening by a certain distance and allows the scattered light scattered at the point (B) where the illumination light hits the surface of the test object to pass;
A light guide unit that repeatedly guides the light that has passed through the light receiving opening by reflection so that an angle θ between the light passing through and the straight line AB at the emission position or a value obtained by adding a constant to the θ, and the light guide A light receiving optical system that receives light guided by the unit and forms an image on a light receiving position detecting element that detects the received position;
A distance measuring apparatus comprising: an arithmetic unit that calculates a distance to the object to be detected based on a position of light detected by the light receiving position detecting element.

  The second means for solving the above-mentioned problem is the first means, wherein the light guide section is composed of two mirrors arranged in parallel to each other and with the reflecting surfaces facing each other. It is characterized by being.

  The third means for solving the problem is the first means or the second means, wherein the light receiving position detecting element is arranged at a focal position of the light receiving optical system. To do.

  The fourth means for solving the problem is any one of the first to third means, wherein the illumination optical system is arranged in parallel with each other, the light source and the collimator lens system, And two mirrors arranged with the reflecting surfaces facing each other, and the light from the light source is converted into parallel light by the collimator lens system and reflected by the two mirrors, respectively, and then the exit aperture It is the one that leads to.

  According to the present invention, it is possible to provide a distance measuring device that is less likely to damage a probe portion and that can be easily replaced.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. In the following drawings, it is assumed that the x axis is in the left-right direction of the paper, the y axis is in the direction perpendicular to the paper, and the z axis is in the vertical direction of the paper. FIG. 1 is a diagram showing a probe unit of a distance measuring apparatus which is a first example of an embodiment of the present invention. This probe is used to measure the inner diameter of the hole 1, but what is actually measured directly is the distance from the probe to the inner wall of the hole 1. By rotating the probe, the distance to the inner wall of the hole 1 can be determined over the 360 ° direction, whereby the inner diameter of the hole 1 can be calculated. Also, by moving the probe up and down, the inner diameter for each hole depth can be measured. Instead of rotating the probe, the hole 1 may be rotated, and instead of moving the probe up and down, the hole 1 may be moved up and down.

  A rhombus prismatic optical element 10 made of a light transmitting member such as glass or plastic is inserted into a hole 1 which is a test object having a depth substantially in the z direction. The upper and lower portions of the optical element 10 are planes perpendicular to the paper surface and are cut at an angle of 45 °. The cutting angle is not necessarily 45 °. It is only necessary that the total reflection condition is satisfied and parallel. Further, if the mirror is used as a normal mirror by depositing a reflective film on this portion, the total reflection condition may not be satisfied.

  Light emitted from a light source 2 having a sufficiently small light emitting portion such as a laser or LED is converted from the illumination light incident surface 11 on the side of the optical element 10 as a light beam having a constant light beam diameter parallel to the x axis through the collimator lens 3. Make it incident. The light beam is reflected at a right angle by the first reflection surface 12 (total reflection surface) and travels through the optical element 10 in the direction toward the back of the hole 1 (z-axis direction). It is preferable that the traveling direction of the light beam be as parallel as possible to the z-axis direction because the thickness of the optical element 10 can be reduced.

  Further, the second reflecting surface 13 is bent again in a direction that forms an angle of approximately 90 degrees to become a light beam parallel to the x-axis, and the object to be examined is emitted from the illumination light exit 14 (exit aperture, indicated by symbol A). The inner wall of the hole 1 is irradiated. Since the diameter of the light beam is thin, the irradiated portion (indicated by symbol B) is regarded as a point. The inner wall of the hole 1 emits scattered light only in the portion irradiated with light. The scattered light spreads in all directions around the point B, but a minute aperture 15 (light receiving aperture, indicated by symbol C) is provided so that only the light beam passing through the minute aperture 15 is received. In other words, a light shielding material is provided in the vicinity of the minute aperture 15, and the scattered light is prevented from passing through the side surface of the optical element 10 in the portion other than the minute aperture 15. In this embodiment, the line connecting the minute opening 15 and the emission port 14 is parallel to the z-axis. However, this is not always necessary.

  The light that has passed through the minute opening 15 enters the reflecting portions 16 and 17 on the side surface of the optical element 10 that are provided so as to be parallel to each other.

  Scattered light incident on the optical element 10 at an incident angle θ is refracted at an emission angle θ ′ according to Snell's law (sin θ = n sin θ ′, where n is the refractive index of the optical element 10). In the reflection of the light incident on the reflecting portions 16 and 17 at the incident angle θ ′, the reflection angle is equal to the incident angle, so that the state where the light beam is always inclined by θ ′ with respect to the parallel reflecting surface is maintained. In this embodiment, the reflection parts 16 and 17 are planes perpendicular to the plane including ABC and are parallel to the BC axis. However, as long as the reflecting portions 16 and 17 are parallel to each other and are a plane perpendicular to the plane including ABC, it is not always necessary to be parallel to the BC axis.

  The reflective portions 16 and 17 are coated with a reflective film to form a mirror. The scattered light that has passed through the minute aperture 15 is repeatedly reflected between the two reflecting portions 16 and 17 while maintaining the angle θ ′, is emitted from the light receiving window 18, and enters the light receiving lens 4 that is a light receiving optical system. . The two reflection parts 16 and 17 become a light guide part. The light that is repeatedly reflected at the light guide at the angle θ ′ is refracted by the Snell's law (nsin θ ′ = sin θ) at the emission window 18 and is emitted from the optical element 10 at the emission angle θ.

  A linear sensor 5, which is a light receiving position detecting element, is provided at the rear focal length position of the light receiving lens 4, and the scattered light that has passed through the minute aperture 15 is spotted at a position corresponding to the angle θ incident on the minute aperture 15. Tie. By detecting the position of this spot, the distance to the inner wall of the hole 1 can be obtained. The light receiving position detecting element is an element that can detect the position where light is incident, and for example, a PSD or a CCD can be used. It is sufficient if a one-dimensional position can be detected, but a two-dimensional element may be used. In this embodiment, the optical axis of the light receiving lens 4 is parallel to the x axis. However, as described later, it is not always necessary to do so.

A parallel light beam as irradiation light is bent at a substantially right angle by the second reflecting surface 13 as a folding mirror to become a light beam parallel to the x-axis, and is incident on the inner wall of the hole 1 substantially perpendicularly. Therefore, on the principle of triangulation, the distance h from the illumination light exit 14 to the inner wall of the hole 1 is the distance L between the illumination light exit 14 and the minute aperture 15 in FIG. 1 and the detected scattered light angle θ. (An angle formed by the scattered light passing through the minute aperture 15 and the straight line AB (or the x axis)) can be expressed by the following equation.

If the reflecting surfaces of the mirrors 16 and 17 are parallel and perpendicular to the straight line AB (that is, parallel to the yz plane), the angle of the light beam in the light guide section composed of the mirrors 16 and 17 Is stored and emitted from the optical element 10 at an angle θ. Therefore, if it is parallel to the optical axis x-axis of the light-receiving lens 4, the focal length of the light-receiving lens 4 is f, and if the image height that can be spotted is x, there is the following relationship.

That is, the distance h from the minute opening 15 to the inner wall of the hole 1 can be expressed by the following equation. These calculations are performed by a calculation unit (not shown) in response to the output of the linear sensor 15.

When the position detection resolution on the linear sensor is Δx, the difference Δh in distance to the inner wall of the hole that can be detected can be calculated as follows.

  For example, when the pitch of the pixels of the linear sensor 5 is 5 μm, the distance h to the inner wall of the hole 1 is 1 mm when the distance L between the exit 14 of the illumination light and the minute opening 15 is 1 mm and the focal length f of the light receiving lens 4 is 10 mm. Can be detected with an accuracy of about 2 μm. In addition, the accuracy is improved as the size of the minute aperture 15 is smaller. However, since the amount of light is reduced and diffraction occurs, the actual limit is about several μm, and practically about several tens μm is preferable.

  In the present embodiment, as described above, since the distance to the hole is measured by the incident angle θ of the light beam incident on the light receiving lens 4, even when light approaches the boundary between the mirror 16 and the light receiving window 18, FIG. As shown in FIG. 4, the light reflected by the mirrors 16 and 17 always enters the light receiving lens 4 in parallel, and forms an image at one point on the linear sensor 5 placed at the rear focal position of the light receiving lens 4. That is, an image is formed at a distance X = fθ from the point where the linear sensor 5 intersects the optical axis of the light receiving lens 4. f is the focal length of the light receiving lens 4. For this reason, if the center of the spot imaged on the linear sensor 5 is detected, the inclination of the light beam can be detected. And the distance h to the hole 1 is computable by the above-mentioned formula.

  Here, prisms and notches are arranged in the microscopic aperture 15 and the light receiving window 18 of the optical element 10, the incident surface is inclined, and the angle of incidence on the reflectors 16 and 17 is made to be totally reflected by making it larger than the critical angle. And light can be propagated efficiently. The reflecting portions 16 and 17 are planes perpendicular to the plane including ABC and are parallel to the AC axis. However, if the reflecting portions 16 and 17 are parallel to each other and are perpendicular to the plane including ABC, it is not always necessary to be parallel to the AC axis.

  Further, as shown in FIG. 1, since the first reflecting surface 12 and the second reflecting surface 13 are arranged in parallel, the optical axis of the optical system on the irradiation side (the optical axis of the light source 2 and the collimator lens 3). Is parallel to the optical axis of the light receiving system (the optical axis of the parallel light emitted from the illumination light exit port 14), and illumination is performed even when the optical element 10 is mounted with an inclination as shown by the solid line in FIG. The light emitted from the light emission port 14 is kept parallel to the original light beam (a straight line parallel to the optical axis of the light source 2 and the collimator lens 3) indicated by a one-dot chain line in FIG.

Further, the incident angle of the light beam incident on the light receiving lens 4 does not change no matter how many times it is reflected by the mirrors 16 and 17. When the optical element 10 is mounted with an inclination of δ, the line connecting the light beam that irradiates the object and the minute aperture 15 is inclined, so the inclination θ ′ of the light beam that passes through the minute aperture 15 is expressed by the following equation: To change.

If δ is small, the following equation is approximately obtained. In an actual measuring apparatus, if the maximum value of this value θ ′ is about 5 arc minutes, there is almost no problem in measurement.

  That is, the smaller the inclination (L / h) of the received light passing through the optical element 10, the less the influence of the error. Therefore, it is desirable to maintain the sensitivity by decreasing the distance L between the illumination light exit 14 and the minute opening 15 and increasing the focal length f of the light receiving lens 4. In this case, the image height becomes high, and the linear sensor 5 may be offset from the optical axis of the light receiving lens 4.

  Further, since the detection position of the hole 1 is shifted due to the inclination of the optical element 10, it is desirable to correct the shift by confirming the position where the light hits the hole 1 when the optical element 10 is attached.

  In the case where the reflecting surfaces 16 and 17 are inclined by δ with respect to the z axis and are not parallel, the incident angle of the scattered light reaching the minute aperture 15 is the angle θ formed by the straight line AB and the scattered light. A value obtained by adding a slope δ with respect to the z-axis.

In this case, the scattered light is refracted at the minute aperture 15 by Snell's law, and the refraction angle is sin = ⁻¹ (sin (θ + δ) / n). In this way, the angle of incidence on the reflecting surfaces 16 and 17 is different from the case where the reflecting surfaces 16 and 17 are not inclined with respect to the z-axis, that is, δ = 0, but the reflecting surfaces 16 and 17 are parallel to each other so that they are reflected. The corner is preserved.

  The emission angle of the light emitted from the light receiving window 18 is θ + δ, but since the light receiving window 18 is inclined by δ, the incident angle with respect to the light receiving optical system 4 independent of the optical element 10 is θ, and the inclination of the optical element 10 Is not affected. FIG. 4 is a diagram showing a probe unit of a distance measuring apparatus which is a second example of the embodiment of the present invention. Since this probe is the same as the probe shown in FIG. 1 except for a part, the same components are denoted by the same reference numerals, and the description thereof may be omitted. In this probe, the light source 2 and the collimator lens 3 are incorporated in the optical element 10, and the parallel light is emitted from the illumination light without passing through the first reflection surface 12 and the second reflection surface 13. 14 can be emitted. The effect is not different from that shown in FIG.

  However, in this case, when the optical element 10 is damaged, the light source 2 and the collimator lens 3 must be replaced at the same time, so the embodiment shown in FIG. 1 can be said to be economically superior. Since the arrangement of the light source 2 and the collimator lens 3 is also flexible, the embodiment shown in FIG. 1 is preferable.

  FIG. 5 is a diagram showing a probe unit of a distance measuring apparatus which is a third example of the embodiment of the present invention. Since this probe is also the same as the probe shown in FIG. 1 except for a part, the same components are denoted by the same reference numerals and the description thereof may be omitted.

  In the embodiment shown in FIG. 1, the optical axis of the light receiving lens 4 which is a light receiving optical system is parallel to AB. However, in this embodiment, the optical axis is inclined by AB and φ. Yes. That is, it is inclined by the x axis and φ. It is the same that the linear sensor 5 is disposed at the focal position of the light receiving lens 4.

  That is, in the embodiment shown in FIG. 1, the scattered light that has passed through the minute aperture 15 enters the light receiving lens 4 with an inclination of θ with respect to the optical axis, but in the case of FIG. 5, (θ−φ ) Only incident at an angle. Therefore, the linear sensor 5 forms an image at a position away from the optical axis of the light receiving lens 4 by X ′ = f (θ−φ). Since f and θ are known, if X ′ is known, θ can be obtained, and h can be obtained by the above-described calculation formula. Thus, the optical axis of the light receiving lens 4 that is a light receiving optical system is not necessarily parallel to AB.

  In the embodiment of the invention, glass is described as an example of the optical element, but a hollow element having a reflection surface on the inner surface or the outer surface may be used.

It is a figure which shows the probe part of the distance measuring device which is the 1st example of embodiment of this invention. It is a figure which shows the example of the incident method of the light ray which injects into a light-receiving part. It is a figure which shows the state in which the light receiving element 10 was inclined and attached. It is a figure which shows the probe part of the distance measuring device which is the 2nd example of embodiment of this invention. It is a figure which shows the probe part of the distance measuring device which is the 3rd example of embodiment of this invention.

Explanation of symbols

1: hole, 2: light source, 3: collimator lens, 4: light receiving lens, 5: linear sensor, 10: optical element, 11: illumination light incident surface, 12: first reflecting surface, 13: second reflecting surface , 14: emitting surface (exiting aperture), 15 minute aperture (receiving aperture), 16: reflecting portion (mirror), 17: reflecting portion (mirror), 18: receiving window

Claims (4)

An illumination optical system that illuminates the object to be examined with illumination light that can be regarded as substantially point-like light on the surface of the object to be examined, through the exit aperture (A);
A light receiving opening (C) that is provided at a position away from the exit opening by a certain distance and allows the scattered light scattered at the point (B) where the illumination light hits the surface of the test object to pass;
A light guide unit that repeatedly guides the light that has passed through the light receiving opening by reflection so that an angle θ between the light passing through and the straight line AB at the emission position or a value obtained by adding a constant to the θ, and the light guide A light receiving optical system that receives light guided by the unit and forms an image on a light receiving position detecting element that detects the received position;
A distance measuring apparatus comprising: a calculation unit that calculates a distance to the object to be detected based on a position of light detected by the light receiving position detecting element.   The distance measuring device according to claim 1, wherein the light guide unit is two mirrors that are arranged in parallel to each other and that are arranged with their reflection surfaces facing each other.   The distance measuring device according to claim 1, wherein the light receiving position detecting element is disposed at a focal position of the light receiving optical system.   The illumination optical system includes a light source, a collimator lens system, and two mirrors that are arranged in parallel with each other and have reflecting surfaces facing each other, and transmits light from the light source to the collimator lens system. 4. The distance measuring device according to claim 1, wherein the distance measuring device converts the light into parallel light and reflects the light with the two mirrors, and then guides the light to the exit aperture. 5. .

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