JP2006003184A - Surface normal measurement method and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for measuring the surface normal of a small-region object surface being at a separated position. <P>SOLUTION: A beam shift optical system 1 for shifting incident light 91 of a light beam in parallel is formed, by using two wedge prisms 11a, 11b and combining them with their mutual both end faces in parallel so as to have a predetermined gap in the middle. This is integrally rotated with an angle variable actuator 41 to change an irradiation position. The method and apparatus measure the surface normal of the object surface being at the separated position, by computing a normal by a normal computing circuit 51 on the basis of distance data obtained by irradiating at least three points 94a, 94b, 94c in the small region with light beams. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method and an apparatus for measuring a surface normal direction of a small area target surface at a distant position as external environment recognition means such as a mobile robot.

There is means for measuring the position and orientation of a measurement target object by combining a laser distance meter and a polygon mirror or the like and scanning a measurement point in a straight line or a plane (see, for example, Non-Patent Document 1).
Ito: Laser measurement system: LMS series, Journal of the Robotics Society of Japan, Vol. 21, no. 1, pp. 45-47, 2003

In addition, a distance measuring device has been proposed in which light is linearly deflected by two optical wedges having the same wedge angle and rotating in opposite directions (see Patent Document 1).
JP-A-7-218633

However, the means of Non-Patent Document 1 is complicated in structure and control, and the rotation angle control resolution and distance measurement resolution of the polygon mirror are not sufficient, so that it is not suitable for measuring a small area surface such as a rising surface of a staircase, for example. It has the disadvantage of being. Further, the means of Patent Document 1 is a method aimed at linearly deflecting over a wide range, and has the disadvantage that the normal direction of the target surface cannot be uniquely determined. Furthermore, when the means of Non-Patent Document 1 and Patent Document 1 are to be applied to measurement of a small area surface, there is a disadvantage that it is necessary to control the deflection angle as the distance to the measurement target surface changes. .

An object of the present invention is to solve such problems, and the invention of the method according to claim 1 irradiates an object with a light beam, receives light reflected by the object surface, and receives the object surface. The normal of the object surface is measured based on a plurality of distance data obtained by irradiating at least three points in a small area of the object surface in parallel with the light beam. It is in the surface normal measurement method characterized by this. According to a second aspect of the present invention, in the above method, there are two wedge prisms in which both end faces are combined in parallel, and the two wedge prisms for changing the irradiation position of the light beam. An angle variable means for changing the angle and an arithmetic means for calculating a normal of the object surface from the plurality of distance data are used, and the invention according to claim 3 is characterized in that: An adjustable gap is provided between the two wedge prisms, and the invention according to claim 4 is characterized in that the two wedge prisms are arranged as light beams of the light beam. The angle is variable by rotating integrally around the axis.

  According to a fifth aspect of the present invention, there is provided an apparatus according to claim 5, wherein a light beam is irradiated onto an object, light reflected by the object surface is received, and a distance to the object surface is measured. In the surface normal measurement apparatus, the normal of the object surface is measured based on a plurality of distance data obtained by irradiating at least three points with the light beam in parallel. According to a sixth aspect of the present invention, the angles of the two wedge prisms, which are combined in parallel with each other, and the two wedge prisms for changing the irradiation position of the light beam are made variable. An angle variable actuator, and an arithmetic circuit for calculating a normal line of the object surface from the plurality of distance data, and the invention according to claim 7, An adjustable gap is provided between the wedge prisms, and the invention according to claim 8 is characterized in that the two wedge prisms are integrated around the optical axis of the light beam. The rotation angle is variable.

  According to a ninth aspect of the present invention, there is provided a distance measuring apparatus including a function for realizing the surface normal measuring method according to the first to fourth aspects.

According to the present invention, in the invention of claim 1 or 5, the object is based on a plurality of distance data obtained by irradiating at least three points in a small area of the object surface in parallel with the light beam. Since the surface normal is measured, the surface normal of a small area of the object surface can be measured by the same means regardless of the distance.

  Further, in the invention of claim 2 or claim 6, the angle between two wedge prisms in which both end faces are combined in parallel and two wedge prisms for changing the irradiation position of the light beam. Since the angle variable means for making the variable and the calculation means for calculating the normal of the object surface from a plurality of distance data are used, the light beam can be shifted in parallel with a simple configuration, The position can be changed smoothly, and the normal can be automatically calculated.

  In the invention of claim 3 or claim 7, since the adjustable gap is provided between the two wedge prisms, the parallel shift amount of the light beam can be changed, and the measurement target The area of the small area to be measured can be adjusted smoothly and easily according to the surface condition and the required measurement accuracy.

  In the invention of claim 4 or claim 8, since the two wedge prisms are integrally rotated around the optical axis of the light beam to make the angle variable, the irradiation position changes on the circumference with the same radius. 3D normal measurement is possible with a simple operation.

  In the invention of claim 9, since the surface normal measurement function can be added to the conventional distance measuring device, the surface normal can be measured while the distance measuring device is fixed. Can be improved.

  As described above, according to the present invention, it is possible to provide means for measuring the normal direction of a small area surface which is simple in structure and control and is located at a distance.

Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 is an explanatory diagram of Embodiment 1 according to the present invention. The configuration and operation will be described with reference to FIG. The light beam projected by the projector 31 is shaped by the projector lens 32 and becomes incident light 91 to the beam shift optical system 1. The beam shift optical system 1 includes a pair of wedge prisms 11 in which inner and outer end faces are arranged in parallel and a cylinder 12 for housing the two, and in this case, the two wedge prisms 11a and 11b are cylindrical and are not shown. The spacers and the presser ring can keep the relative positions with a space in parallel. Incident light 91 enters the beam shift optical system 1 and is irradiated as irradiation light 93. That is, the incident light 91 is refracted by the first prism 11a, becomes the refracted light 92, and becomes incident light on the second prism 11b. The refracted light 92 is further refracted by the second prism 11b and becomes irradiated light 93, which is irradiated toward the measurement target surface 9. As will be described later, the irradiation light 93 is shifted in parallel with the incident light 91. In this case, the irradiation light 93 a is applied to the irradiation point 94 a on the target surface 9. The reflected light 95 reflected at the irradiation point 94 a returns to the reverse direction through the beam shift optical system 1, for example, and returns to the light receiver 33 through the light receiving lens 34. The measurement control circuit 35 constitutes a distance calculation circuit based on, for example, detection of a pulse-modulated light phase difference, and performs light projection / reception control of the light projector 31 and the light receiver 33 to calculate the distance from the reference point to the target surface. .

In addition, the beam shift optical system 1 is provided with a rotation guide (not shown), abuts on the rotational force transmitting means 42 provided on the shaft of the motor 41 that is a variable angle actuator, and can rotate in conjunction with the motor 41. ing. The measurement control circuit 35 can control the rotation angle of the motor 41, so that the rotation angle of the beam shift optical system 1 can be controlled to a predetermined angle.

The measurement control circuit 35 controls the rotation angle of the beam shift optical system 1 to at least three angles via the motor 41, changes the irradiation light to 93a, 93b, and 93c, and changes the irradiation points 94a, 94b, and 94c on the target surface 9. Measure the distance up to. The rotation angle information and the distance measurement result are sent to the normal calculation circuit 51 for calculating the normal. The normal calculation circuit 51 calculates the normal of the target surface from the rotation angle information and the distance measurement result, and displays the normal on the display 52. You may display the distance to the target surface 9 on the display 52 as needed. Further, the measured normal direction may be examined and displayed as a rotation angle around a preset coordinate axis, for example.

The beam shift optical system 1 is not limited to the configuration shown in FIG. 1, and may be configured as the optical system 2 shown in FIG. In this case, the beam shift optical system 2 is composed of a pair of wedge prisms 21 whose inner and outer end surfaces are parallel to each other and a cylinder 22 for housing the wedge prisms 21a and 21b. The two wedge prisms 21a and 21b are spaced apart by a spacer and a holding ring (not shown). The relative position can be maintained. Incident light 91 enters the beam shift optical system 2 and is irradiated as irradiation light 93. That is, the incident light 91 is refracted by the first prism 21a, becomes the refracted light 92, and enters the second prism 21b. The refracted light 92 is further refracted by the second prism 21b and becomes irradiated light 93, which is irradiated toward the measurement target surface 9. Also in this case, the irradiation light 93 is shifted in parallel with the incident light 91.

Next, the principle of surface normal measurement according to the present invention will be described with reference to FIG. A coordinate system is defined in which the reference point for distance measurement is the origin O, the distance measurement direction is z, and the installation reference plane is x. Assume that the parallel shift amount of the irradiation light 83a with respect to the incident optical axis 81 is r, the shift angle is θ, and the normal line of the object surface 85 is N. By the beam shift optical system 1, the irradiation start point can be regarded as having moved to 82a. If θ is changed and the distance to at least three points 84a, 84b, and 84c is measured, the three optical paths are parallel, so the coordinates of the three points in this coordinate system, P1, P2, and P3, respectively, are determined. A unit normal vector N including 84a, 84b, 84c can be calculated.

  Next, details of the light beam parallel shift method according to the present invention will be described with reference to FIG. In order to change the irradiation position, two wedge prisms 11a and 11b are used. Arrange them so that the wedge surfaces facing each other are parallel. The light 91 incident perpendicularly to the left first prism 11a is refracted and emitted as refracted light 92 to the right. Then, the refracted light 92 is further refracted by the second prism 11 b and emitted as irradiation light 93 to the right side thereof. If the two prisms 11a and 11b have the same refractive index and wedge angle or optically the same performance, the incident light 91 and the irradiation light 93 are parallel. The distance between the incident optical axis and the irradiation light 93 at this time is called a beam shift amount r. Here, by changing the wedge angle θw, the refractive index n, and the interval L between the two prisms of the prisms 11a and 11b, the beam shift amount r can be appropriately adjusted. The refraction angle θd of the refracted light 92 from the first prism 11a is obtained from equation (2), and the beam shift amount r is obtained from equation (3).

  If the prisms 11a and 11b are rotated together while maintaining the relative relationship of the prisms 11a and 11b, the irradiation light 93 can be changed in parallel on the circumference of the radius r, so that the measurement target surface is irradiated in parallel with the incident optical axis 91. Light can be irradiated while being translated by r.

  In the light beam parallel shift method, the parallelism error of the both end faces of the second prism 11b with respect to the first prism 11a becomes the parallel shift of the irradiation light. In particular, when applied to long distance measurement, it has been found that the above error is a major factor that causes an increase in distance measurement error and surface normal measurement error. Care must be taken in designing and manufacturing the beam shift optical system 1 in order to maintain measurement accuracy.

As described above, due to the effect of the beam shift optical system 1, it is possible to provide means for easily measuring the normal direction N of the target surface 9 with a simple structure and control.

In order to improve the distance measurement accuracy, the optical path length may be corrected by inserting a beam shift optical system. Further, in order to improve the surface normal measurement accuracy, it is preferable that the number of irradiation points is not three but more. In addition, when the target surface is not a flat surface, a partial normal line may be measured from a large number of irradiation point groups and used as a shape recognition means.

FIG. 5 is an explanatory diagram of a second embodiment according to the present invention in the case of using a distance meter that is manufactured by integrating a projector, a light receiver, and a part of a measurement control circuit. In order to perform distance measurement, for example, a distance meter 6 having a communication function and based on the principle of pulse-modulated optical phase difference detection is used. The emitted light 91 of the distance meter is shifted in parallel by the beam shift optical system 1 in the same manner as in the first embodiment, and is irradiated as the irradiation light 93. Reflected light from the surface to be measured is received by the distance meter 6, and the distance measurement result calculated by the distance meter 6 is received by the communication control circuit 7. The communication control circuit 7 controls the distance meter 6 and controls the rotation angle of the motor 41 in order to control the rotation angle of the beam shift optical system 1 to at least three angles as in the first embodiment. The rotation angle information and the distance measurement result are sent to the normal calculation circuit 51, and the normal calculation circuit 51 calculates the normal N of the target surface from the result and displays it on the display 52. Since other configurations and operations of the second embodiment are the same as those of the first embodiment, detailed description thereof is omitted.

As described above, due to the effect of the beam shift optical system 1, it is possible to provide means for easily measuring the normal direction of the target surface while the structure and control are simple and the distance meter main body is fixed.

The present invention can be used as external environment recognition means such as a mobile robot. For example, it can be used as means for easily measuring the inclination of a structure such as a wall surface or a staircase.

Explanatory drawing of Example 1 of this invention Illustration of other light beam parallel shift optical system Illustration of surface normal measurement principle Illustration of light beam parallel shift Explanatory drawing of Example 2 of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Beam shift optical system 11 A pair of wedge prism 11a, 11b Wedge prism 12 Cylinder 2 Another beam shift optical system 21 A pair of wedge prism 21a, 21b Wedge prism 22 Cylinder 31 Light projector 32 Light projection lens 33 Light receiver 34 Light reception lens 35 Measurement Control circuit 41 Motor 42 Rotational force transmission means 51 Normal calculation circuit 52 Display 6 Distance meter 7 Communication control circuit 81 Incident optical axis 82a Irradiation start point 83a Irradiation light 84a, 84b, 84c Irradiation point 85 Normal measurement target center point 9 Normal measurement target surface 91 Incident light 92 Refracted light 93, 93a, 93b, 93c Irradiated light 94a, 94b, 94c Irradiated position 95 Reflected light

Claims (9)

Using the principle of irradiating an object with a light beam, receiving light reflected from the object surface, and measuring the distance to the object surface, the light beam is parallel to at least three points in a small area of the object surface. A surface normal measurement method, comprising: measuring a normal of the object surface based on a plurality of distance data obtained by irradiation. 2. The method according to claim 1, wherein the angle of the two wedge prisms in which both end faces are combined in parallel and the angle of the two wedge prisms for making the irradiation position of the light beam variable is variable. And a surface normal measurement method characterized by using means for calculating the normal of the object surface from the plurality of distance data. 3. The surface normal measurement method according to claim 2, wherein an adjustable gap is provided between the two wedge prisms. 4. The surface normal measurement method according to claim 2, wherein the two wedge prisms are integrally rotated around the optical axis of the light beam to change the angle. Using the principle of irradiating an object with a light beam, receiving light reflected from the object surface, and measuring the distance to the object surface, the light beam is parallel to at least three points in a small area of the object surface. A surface normal measurement device that measures a normal of the object surface based on a plurality of distance data obtained by irradiation. 6. The apparatus according to claim 5, wherein the angle of the two wedge prisms in which both end faces are combined in parallel and the angle of the two wedge prisms for making the irradiation position of the light beam variable is variable. A surface normal measuring apparatus comprising: an actuator; and an arithmetic circuit for calculating a normal of the object surface from the plurality of distance data. 7. The surface normal measuring apparatus according to claim 6, wherein an adjustable gap is provided between the two wedge prisms. 8. The surface normal measuring device according to claim 6, wherein the two wedge prisms are integrally rotated around the optical axis of the light beam to change the angle. 5. A distance measuring apparatus incorporating a function for realizing the surface normal measuring method according to claim 1.

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