JPH04249711A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a small-size distance measuring apparatus capable of measuring the distance to a measuring plane in a short time. CONSTITUTION:A parallel luminous flux with a ring cross section is cast to planes A, B to be measured. An image of the ring on each plane A, B is photographed by a camera 11. The distances l1, l2 to the respective planes A, B from the camera 11 are measured from the size of the radii r1, r2 of the ring images A', B' photographed by the camera 11. Moreover, angles of the measuring planes to a view line 7 of the camera are obtained from the degree of flatness of the elliptical rings A', B' (the angles are deviated from 90 deg. if the degree of flatness is increased). The maximum inclining direction (which is the direction of a longer diameter of the ellipse) is thus obtained from the inclination of the ellipse.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device, and more particularly to a simple point measuring device.

0002

2. Description of the Related Art Conventionally, this type of distance measuring device has been a device that applied triangulation using a laser spot light, or a device that applied autofocus on the lens side using a beam image.

FIG. 2 is a diagram showing a distance measuring device to which triangulation is applied. A laser tube 21 irradiates a laser beam 22 onto a measuring object 24, a two-dimensional CCD camera 23 takes an image of the measuring object 24, and the laser beam 22 The distance of the object to be measured is measured from the intersection of two straight lines between the laser beam 22 and the optical path of the light that hits the object 24, is diffusely reflected, and enters the two-dimensional CCD camera 23.

FIG. 3 is a diagram showing a distance measuring device to which autofocus is applied, in which a laser beam from a laser tube 31 is placed by a half mirror 32 on the optical axis of a two-dimensional CCD camera 34 equipped with a focus adjustment mechanism 33. The projection of the laser beam onto the object 35 is imaged by a two-dimensional camera 34, the focus point that is just in focus is found, and the distance between the CCD camera 34 and the measurement object 35 is determined from the state of the optical system at that time. Figure 4(a) shows the two-dimensional C when the focus is in front.
An image captured by the CD camera 34 is shown in FIG. 4(b).
4(c) shows an image taken by the two-dimensional CCD camera 34 when the focus is just right, and FIG. 4(c) shows the two-dimensional CC image when the focus is far away.
An image taken by the D camera 34 is shown.

[0005]

[Problem to be Solved by the Invention] The conventional distance measuring device using triangulation described above cannot be applied to surveying inside a hole because a certain distance is required between the place where the laser is emitted and the place where the camera is used. , there is also the disadvantage that the device becomes larger. Furthermore, the autofocus system has the disadvantage that it takes time to collect point data because the focus adjustment is performed mechanically.

[0006]

[Means for Solving the Problems] The distance measuring device of the present invention projects a parallel light beam having a ring-shaped cross section onto a measurement plane, and images a ring image on the measurement plane object by the light beam with a camera, The method is characterized in that the distance from the camera to the measurement plane is measured from the size of the radius of the ring image taken by the camera.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1(a) is a diagram showing an embodiment of the present invention, in which a laser beam from a laser tube 1 is guided through a lens 2, a collimator lens 4, and a light shielding plate 3 disposed between them into a laser beam having a ring-shaped cross section. A parallel beam is created and converted into a ring-shaped laser parallel beam 6 centered on the line of sight of a two-dimensional CCD camera 11 using a half mirror 5. A measurement plane illuminated by a ring-shaped laser parallel beam 6 (measurement planes A and B are shown in FIG. 1) is captured by a two-dimensional CCD camera 11.
, and an image of the measurement plane by lens 8 is focused on CCD 10 .

In this way, the image A of the measurement planes A and B
', B' are obtained as shown in FIGS. 1(b) and (c).

[0010] r1 of the ring radius of these images A' and B'
r2 (the longest radius when the ring forms an ellipse) is the radius r1 of the image A' of the measurement plane A close to the lens 8, and the radius r1 of the image B' of the measurement plane B far from the lens 8.
2 becomes smaller. The distance of the object to be measured from the camera is calculated from the radius of the image ring obtained from this relationship.

Note that the radius of the ring-shaped laser parallel beam 6 is R, the field of view of the two-dimensional CCD camera 11 is θ, and the lens 8 is
Let the distance from the measurement planes A and B be l1 l2

0012

(k is a constant).

In addition, when obtaining the radius r of the ring of images A' and B', the radius r of the ring in FIGS. Since a ring is used as shown in the figure, even if the two-dimensional CCD camera 11 is out of focus, the correct radius r can be obtained. Figure 4(a)~
(c) is a diagram showing an image of the two-dimensional CCD camera 11 when the measurement plane is irradiated with a beam having a circular cross section, and FIG.
) to (f) are diagrams showing images when the measurement plane is irradiated with a beam with a ring-shaped cross section. 4(e) is a diagram when the camera is in just focus, and FIGS. 4(c) and 4(f) are diagrams when the camera is in focus. In the case of a ring shape, even if the camera goes out of focus, the ring only becomes thicker and the center of the ring does not change, so the correct radius r can be obtained.

Furthermore, the angle between the measurement plane and the camera's line of sight is obtained by the oblateness of the ellipse of the ring of the obtained image (as the oblateness increases, the angle deviates from 90°),
By tilting the ellipse, its maximum inclination direction is obtained (the major axis direction of the ellipse is the maximum inclination direction).

As described above, the distance and inclination of the measurement plane from the camera can be measured.

[0017]

As explained above, the present invention provides a compact distance measuring system that can measure the distance to a measurement plane in a short time by projecting a ring-shaped light beam onto the measurement plane and analyzing the image obtained. There is an effect that the device can obtain.

[Brief explanation of the drawing]

[FIG. 1] FIG. 1(a) is a diagram showing one embodiment of the present invention, FIG.
(b) and (c) are two-dimensional CCD cameras 11, respectively.
FIG. 2 is a diagram illustrating images of measurement planes A and B according to FIG.

FIG. 2 is a diagram showing a conventional distance measuring device using triangulation.

FIG. 3 is a diagram showing a conventional distance measuring device using autofocus.

4(a) to 4(c) are diagrams showing images taken by the two-dimensional CCD camera 23 of the distance measuring device in FIG. 3, and FIGS. 4(d) to (
f) is a diagram showing an image taken by the two-dimensional CCD camera 11 of the embodiment of FIG. 1;

[Explanation of symbols]

1, 21, 31 Laser tube 2 Lens 4 Collimator lens 5 Half mirror 6 Ring-shaped laser parallel beam 7 Camera line of sight 8 Lens 10 CCD 11, 23, 34 Two-dimensional CCD camera 22
Laser beams 24, 35 Measurement object 33 Focus adjustment mechanism

Claims (2)

[Claims] 1. A parallel light beam having a ring-shaped cross section is projected onto a measurement plane, a ring image on the measurement plane by the light beam is imaged by a camera, and the radius of the image of the ring image taken by the camera is determined. A distance measuring device that measures a distance from the camera to the measurement plane. 2. The distance measuring device according to claim 1, wherein the inclination of the measurement plane is determined based on the elliptic oblateness of the ring image.