JPS61181909A - Distance detector - Google Patents

Abstract

PURPOSE:To enable a highly accurate detection of distance in a wide measuring range, by locating part of an observing surface corresponding to the mark closer to an observation lens far from the lens to allow the formation of a good image evenly over the entire observing surface. CONSTITUTION:The positions (marked points T0-T2) of an object on an observing line 2 deviated from the optical axis 1 of an observing lens L are measured so that the distance to the object may be detected as distance from the optical axis 1 of the observing lens L. Here, since the observing surface is located at the position closer to a theoretical image formation field 4 as a whole, a distinct image can be always obtained on the observing surface regardless of the distance to the marked points.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a distance detector that optically detects the distance to an object with high precision.

(Prior art) Machines that can flexibly work in three-dimensional space, that is, robots, need to measure the position, posture, shape, deformation, etc. of objects, and in this measurement, it is essential to acquire distance information. be. In this case, it is important to be able to obtain distance information while minimizing the effects of restricting the movement of the object or causing deformation of the object. For this reason, optical distance detection methods that can measure distance from a distance without contact are being considered.

This optical distance detection method uses marks (points) that are formed by drawing marks on the object surface, by projecting a light beam onto the object surface, or by embedding light emitting elements on the object surface. and line images) onto the observation surface using an observation lens, and the position of this projected image is detected by a position detection photosensitive element such as a CCD placed on the observation surface to obtain distance information to the object. get.

(Problem to be Solved by the Invention) In an imaging optical system using a lens, the position of the observation surface where a clear image of the object can be obtained on the observation surface is generally determined by the distance between the lens and the object. is the position determined by the following lens imaging formula. That is, when the distance between the object and the lens is b, the focal length of the lens is f, and the distance between the lens and the observation surface is a, the conditions for obtaining a clear image are as follows.

For example, in a camera, the distance a between the lens and the observation surface is
is made variable so that the object can be imaged most clearly. However, in order to obtain a clear image and improve detection accuracy with a distance detector, attempting to adjust the focus by mechanical movement is disadvantageous in improving measurement speed, and a fixed focus method is usually adopted. There is. However, if the fixed focus method is used, the image obtained on the observation surface will be blurred, making it impossible to perform highly accurate measurements.

An object of the present invention is to provide a distance detector that detects the distance to an object with high accuracy.

(Means for Solving the Problems) The above object is achieved by positioning the part of the observation surface corresponding to the marker closer to the observation lens at a position farther from the observation lens.

(for production) The principle of operation of the present invention will be explained using FIG.

In order that the distance to the object is detected as the distance from the optical axis 1 of the observation lens L, the position of the object on the observation line 2 that is offset from the optical axis 1 of the observation lens L (gauges To, T+, '
r2. ) is measured. If the observation surface on which the photosensitive element for position detection is arranged is arranged perpendicular to the optical axis 1 of the observation lens L as in the conventional case (3 in the figure), the observation surface other than the gauge point T0 that satisfies the condition of equation (1) Marking point T8. Image 1 on observation plane 3 corresponding to T2. ,1. The image becomes blurred and the detection accuracy decreases. On the other hand, in the present invention, the observation plane is provided at a position closer to the theoretical imaging plane 4 that satisfies formula (1) as a whole compared to the conventional one, so the observation plane A clear image is always obtained at the top.

(Example) Hereinafter, the present invention, which is different from that shown in FIG. 1, will be explained in detail. Second
The figure is a schematic side view of a second embodiment of the invention. At the position of observation lens L, it passes through a part R6 away from optical axis 1, and optical axis 1
A linear light beam 5 is projected in the direction of angle α (counterclockwise is positive) to generate a bright spot T on the object plane 0, and this bright spot T is focused on the observation lens L. The distance to the object is measured by projecting the image I onto the observation surface 3 and detecting the position of the image I projected onto the observation surface 3 by the position detection photosensitive element P arranged on the observation surface 3. .

When the distance of the image I on the observation surface 3 from the optical axis 1 is set to X, the theoretical imaging surface is expressed by the following equation.

R6 x = a(--tanα)' -Ro (2) Therefore, it is obvious from equation (1) that the part of the observation surface corresponding to the landmark (marker) closer to the observation lens is moved away from the observation lens. As a result, the mark on the object is imaged on the observation surface with less blur.

FIG. 3 is a schematic diagram of a third embodiment of the present invention.

This distance detection device has been extremely widely used in recent years, and it projects a light beam 5 onto the object plane 0 and detects the object 0.
The position of the bright spot T generated above on the observation surface 3 is detected, and the distance in the light beam projection direction is detected. In this distance detection device as well, the position detection photosensitive element is conventionally arranged perpendicular to the optical axis 1 of the observation optical system. The angle between the optical axis 6 of the light beam projection optical system and the optical axis 1 of the observation optical system is α, and the focal length of the observation lens L is f1.The light beam projection optical system starts from the optical axis 1 of the observation lens L when the focal length of the observation lens L is f1. If the distance to the optical axis 6 of the system is R8, the theoretical imaging plane is similarly expressed by equation (2). Therefore, by moving the observation plane corresponding to a closer gauge point away from the observation lens L, measurement accuracy can be further improved.

FIG. 4 is a schematic side view showing a fourth embodiment of the present invention.

This embodiment is based on the invention disclosed in Japanese Patent Application No. 58-161088. A reflecting mirror 7 is arranged in front of the observation lens L, and a bright spot T formed by projecting the light beam 5 onto the object surface 0 is reflected by the reflecting mirror 7 and then onto the observation surface 3. The distance of the observation lens L in one direction of the optical axis is detected from the position of the image I projected onto the observation surface 3. In the case of this embodiment as well, it is assumed that the inclination angle of the reflecting mirror 7 with respect to the optical axis 1 is φ, the focal length of the observation lens L is f, and the observation lens L with respect to the reflecting mirror 7 is
Assuming that the virtual observation lens is placed at a position symmetrical to L', and the distance d (1+sec α) from the optical axis 1 of the observation lens to the optical axis 1' of the virtual observation lens at the position of the observation lens L is Ro, then basically Generally speaking, it is the same as in the case of FIG. 3, and the surface that satisfies equation (2) becomes the theoretical imaging surface. Therefore, by arranging the position detection photosensitive element P as shown in the figure so that the part of the observation surface corresponding to the nearer gauge point is further away from the observation lens, a bright spot can be seen more clearly regardless of the distance to the object. T can be imaged.

The above has been explained two-dimensionally using a cross-sectional view with respect to the optical axis, but it goes without saying that the same applies to three-dimensional arrangements, including cases where the device is rotationally symmetrical with respect to the optical axis 1. stomach.

In the present invention, the observation surface, ie, the position detection photosensitive element, is not a flat surface but may have a curvature. Further, the observation lenses shown in the drawings according to the above embodiments are merely conceptual representations of condensing lenses, and needless to say, they include single-lens and double-lens lenses.

(Effects) In the present invention, since the portion of the observation surface corresponding to the marker closer to the observation lens is located farther from the lens, it is possible to form a good image on average over the entire observation surface. Therefore, distance detection can be performed with high accuracy over a wide measurement range.

[Brief explanation of drawings]

1 to 4 are schematic diagrams of first to fourth embodiments of the present invention, respectively. L... Observation lens, Lp... Projection lens, T, To, I3. I2......marker sign)
[,1,,I,,I2...image,P...
...Position detection photosensitive element, ○...Object plane, 1...Optical axis of observation lens, 3...Observation surface, 4...Theory imaging plane,
5...Light beam, 7...Reflector 1st
Figure 4 (:1,

Claims (1)

[Claims] Project the mark on the object onto the observation surface using the observation lens,
In this type of distance detection device that detects the position of the sign image projected on the observation surface using a position detection photosensitive element on the observation surface to obtain distance information to the object, the observation lens corresponds to a sign that is closer to the object. A distance detection device characterized in that a portion of the observation surface where the observation surface is located is located farther from the observation lens.