JPS6338107A - Scan type laser range finder - Google Patents

Abstract

PURPOSE:To take a measurement speedily with accuracy by simple facilities by turning a reflecting mirror around its center axis of turning by a specific angle and reflecting projection light by the center axis of turning. CONSTITUTION:Laser light emitted by a laser oscillator 1a is reflected by the center axis 5 of turning of the turning mirror 4 and projected as spot light on an object 8. Laser reflected light 7 which returns in the same course with the laser protected light 6 when viewed from the center axis 5 among various scattered light beams of the spot light is received by a photodetector 2a. Then the mirror 4 is rotated around the center axis 5 by an angle theta and then the spot light moves on the object 8 from a point P to a point Q. The position of the light spot on the detector 2a is detected in synchronism with laser light scanning by the turning of the mirror 4 to measure the isolation distance of the scanning range (P-Q) continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] Kikomei relates to a scanning laser distance meter that continuously measures the distance from the object to measure the surface shape of the object.

[Conventional technology]

Laser rangefinders are used in a wide variety of fields to capture the shape and distance of objects by utilizing the property of lasers, which travel straight through as arrows of light and bounce back as strong light.

As shown in Figure 5, the principle of the laser distance meter is that a laser beam is projected onto the target object from a laser oscillator 1 (point M), and a photodetector 2 placed near the laser oscillator 1 detects N1 on the target object. Map the light spot that occurs at the point or N2 points,
The distance $M-N or M-N2 is measured from the position eQ''Qs of the light spot on the photodetector 2.

In addition, when measuring the profile of an object, the sixth
As shown in the figure, the object 8 is fixed, and the distance from Po to Pn is measured by moving the laser distance meter 10, which integrates the laser oscillator 1 and the photodetector 2, parallel to the object 8. #Standing 0-Standing. Or, conversely, fix the laser distance meter 10 and move the object in parallel to obtain a distance of 31
A 1f stage has been proposed in which the profile is obtained by measuring the moving distance and determining the vertical 0""un for the moving distance.

[Problem that the invention seeks to solve]

The above-mentioned technical means require large-scale equipment to move the laser rangefinder or the object, and there are problems in that rattling and vibration of the laser rangefinder itself while it is moving can easily cause measurement errors, and it takes a long time to complete the measurement. was there.

The object of the present invention is to solve these problems all at once and to propose a scanning laser distance meter that can measure accurately and quickly with simple equipment.

[Means for solving problems]

The present invention is intended to solve the above-mentioned problems, and employs the following technical means. In other words, ■a laser oscillator that projects laser light onto a target object, ■a photodetector that detects reflected light from the target object, and ■a scanning laser distance meter that uses a reflective mirror interposed in the optical path of the projected light and reflected light. The reflecting mirror is rotated at a predetermined angle around the central axis of rotation,
The projection light is reflected from the rotational center axis to continuously scan the surface of the object, and the reflected light from the object surface is reflected to the photodetector at the rotational center axis.

[Effect]

The operation of the present invention will be explained with reference to FIGS. 3 and 4. Third
The figure shows a perspective view, and FIG. 4 shows a plan view. The laser beam projected from the laser oscillator 1a is reflected on the rotation center axis 5 of the rotation mirror 4.

Spot light is projected onto the object 8.

Among the various scattered lights from the spot light, the photodetector 2a receives the laser reflected light 7 that returns along the same path as the laser projection light 6 when viewed from the direction of the mirror rotation center axis 5. Therefore, the photodetector 2a is installed through the lens 3 above the projected light 6 when viewed from the direction of the mirror rotation center axis 5 (FIG. 4).

In the above configuration, when the rotating mirror 4 is rotated by an angle θ about the central axis 5, the spot light moves on the object 8 from point P to point Q.

Let the distances from point 0 of the mirror rotation center axis 5 to points P and Q be OF and OQ.

If 0F=OQ, the angle φ formed by the projected light 6 and the reflected light 7 is the same, and φP=φQ. The positions of the light spots P' and Q' on the photodetector 2a corresponding to this angle φ are the same.

Further, if OP≠OQ, the angle φ is different and becomes φpf - φQ. The positions of the light spots P' and Q' on the photodetector 2a corresponding to the angles φP and φQ are different positions.

In other words, the distance from the rotation center 0 point to the target object is determined by the distance from the photodetector 2aJ corresponding to the angle φ formed by the projected light 6 and the reflected light 7.
It can be measured as the position of the light spot of z and does not depend on the rotation angle 0 of the single rotation mirror 4.

Therefore, if the position of the light spot on the photodetector 2a is detected in synchronization with the laser scanning by the rotation of the rotating mirror 4,
It is possible to continuously measure the distance between the scanning ranges (points P to Q).

Note that if the incident laser beam deviates from the rotation center axis 5 of the rotation mirror, an error will occur in the measurement distance depending on the rotation angle of the mirror, so it is necessary to make the laser beam incident on the rotation center axis 5 of the rotation mirror. . For example, the measurement error ΔZX when the laser beam is incident on a point X mm away from the rotation center axis 5 is expressed as follows, where θX is the rotation angle of the mirror...(1) where ΔIX is a function of Ox. Since it is expressed as
By measuring the rotation angle θX, it is possible to correct ΔIX.

The reason for this will be explained with reference to FIGS. 7 and 8. As shown in the figure, rectangular coordinates are taken with the center 0 of the mirror as the origin.

Here, Sl: Coordinates when the scanning laser rangefinder 9 is in the correct position S2: Coordinates when the scanning laser rangefinder 9 is shifted by X mm 0: Mirror rotation angle A: From the photodetector to the mirror center If the distance is the distance from the center of the BEE laser to the surface of the object, then (the distance #Lx from the sensor to the surface of the object at any angle θX when the laser beam is irradiated to the center axis of O is as follows from Figure 7) The distance Lx+ when the sensor is set at a position offset by X mm from the y-axis is LXI = 5 from Figure 8.
2QX + QXPXI where 52QX=A (X-tan(-Ox)) Sin
L (/X Sin l tlx therefore LX 1=A
+Xa tan Ox.

(2) Therefore, since the distance error ΔflX is obtained from the difference between equations (3) and (2), the equation (1) is obtained.

〔Example〕

Figures 1 and 2 show an example in which the scanning laser distance meter of the present invention is applied to detecting the tip shape of a hot coil. Two types of scanning laser range finders are used. A distance meter is preset on the coil center axis according to the coil diameter, and the laser is scanned at an angle of 45 degrees. Let the coil rotate at a constant speed.

The distance to the coil surface, that is, the surface shape, is measured in a 45-degree scanning range to detect the shape of the tip of the coil.

Figure 1 shows an optical path diagram during measurement, and Figure 2 shows an example in which a scanning laser distance meter is preset to accommodate coils of different diameters and is used to detect the tip position of the coil.
Figure 2(a) shows a side view, Figure 2(b), Figure 2(
C) is a plan view showing the case where measurements are made corresponding to small-diameter and large-diameter coils, respectively.

In the embodiment of the present invention, an eccentric cam is used to rotate the mirror, and the mirror rotation angular velocity is 60 deg/sec.
Mirror rotation angle 33.75°≦θ≦56.25° Measurement scanning time 750 m s / 1 scan Return scanning time 250 m5 / '1scan Sampling period 5 ms (200 Hz) to improve measurement efficiency and equally spaced data Sampling was made possible. Additionally, the two rangefinders share a rotating mirror.

Note that the left and right measured pressure # error is when the incidence of the laser beam mentioned above deviates from the rotation center axis 5 of the rotation mirror.

In the mirror rotation angle of this embodiment, for example, X is -1 m.
The case where the deviation is m is calculated from equation (1) as Δ! ;L1 =-
0.41mm to 12=0.41mm.

[Effects of the Invention] The scanning laser distance meter of the present invention can measure the shape of a target object,
The separation distance can be measured quickly and accurately with simple equipment, so for example, it is possible to automatically detect the tip shape of a hot coil and the winding direction of the coil, making it possible to automate the line, as well as It has a wide range of applications and is highly effective in promoting business efficiency.

[Brief explanation of the drawing]

1 and 2 are embodiments of the present invention, and FIG. 31A
4 are explanations of the working theory of the present invention, FIGS. 5 and 6 are explanatory diagrams of the conventional example, and FIGS. 7 and 8 are explanatory diagrams for proving the mathematical formula. 1... Laser oscillator 1a... Laser oscillator 2.
...Photodetector 2a...Photodetector 3...Lens 4...Rotating mirror 5...Rotating center axis 6...Laser projection light 7...Laser reflected light 8... Object 9...Scanning laser distance meter 10...Laser distance meter φP, φQ, 0, θX...Angle M, N1. N2. O, P, Pn, P', Q, Q', Sl
, 32 points

Claims (1)

[Scope of Claims] 1. Consisting of a laser oscillator that projects laser light onto an object, a photodetector that detects reflected light from the object, and a reflecting mirror that is interposed in the optical path of the projected light and reflected light, The reflecting mirror is rotated by a predetermined angle around a rotational center axis, and reflects the projected light at the rotational center axis to continuously scan the surface of the object, and also to reflect light from the surface of the object. A scanning laser distance meter characterized in that light is reflected to the photodetector at the rotation center axis.