JPH0665965B2 - Distance detection device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a distance detector that optically detects a distance to an object with high accuracy.

(Prior Art) A machine that can flexibly work in a three-dimensional space, that is, a robot requires measurement of the position, posture, shape, deformation, and the like of an object, but in this measurement, acquisition of distance information is essential. In some cases, it is essential that the distance information can be acquired with the influence of restraining the movement of the object or causing deformation of the object to a minimum. Therefore, an optical distance detection method that can measure from a remote place without contact has been considered. This optical distance detection method is a mark formed by drawing a mark on the object surface, by projecting a light beam on the object surface, or by pushing a light emitting element on the object surface. And the line image) are projected onto the observation surface by an observation lens, and the position of this projected image is detected by a position-sensing photosensitive element such as a CCD arranged on the observation surface to obtain distance information to the object. get.

Further, in Japanese Patent Laid-Open No. 60-52710, in order to miniaturize such a distance detector, between the object and the observation lens,
A distance detecting device has been proposed in which a reflecting mirror is arranged and an image of a sign is once folded back to the optical axis side of the observation lens and then inserted into the observation lens to reduce the size of the device.

(Problems to be Solved by the Invention) By the way, 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. Specifically, the position is determined by the following lens imaging formula. That is, assuming that the distance between the lens and the object lens is b, the focal length of the lens is f, and the distance between the lens and the observation surface is a, the condition for obtaining a clear image is as follows.

For example, in a camera, the distance a between the lens and the observation surface is
Is variable so that the object can be imaged most clearly. However, trying to adjust the focus by mechanical movement to obtain a clear image in the distance detector to improve the detection accuracy is disadvantageous in improving the measurement speed, and the fixed focus method is usually adopted. There is. However, if the fixed focus method is used, the image obtained on the observation surface is blurred and high-precision measurement cannot be performed.

Such a problem naturally occurs in the miniaturized distance detecting device proposed in the above-mentioned Japanese Patent Laid-Open Publication No. Sho.

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

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

(Operation) The operation principle of the present invention will be described with reference to FIG.

FIG. 1 illustrates the case where the reflecting mirror is removed.

The position of the object on the observation line 2 deviated from the optical axis 1 of the observation lens L (mark points T ₀ , T ₁ so that the distance to the object is detected as the distance from the optical axis 1 of the observation lens L). , T ₂ ,) is measured. When the observation surface on which the position-sensing light-sensitive element is arranged is arranged perpendicularly to the optical axis 1 of the observation lens L (3 in the figure) as in the conventional case, the reference point T ₀ satisfying the condition of the expression (1) is gauge T _1, the image I ₁ on the observation plane 3 corresponding to the T ₂ of the non, I ₂ is the detection accuracy will be blurred lowered. On the other hand, in the present invention, the observation surface is provided closer to the theoretical imaging surface 4 satisfying the expression (1) as a whole, as compared with the conventional case,
A clear image is always obtained on the observation surface regardless of the distance to the gauge point.

Hereinafter, a case different from FIG. 1 will be described. Second
The figure is a schematic side view when the light beam is incident at an angle with the optical axis of the observation lens. The linear light beam 5 is projected at a position of the observation lens L, passing through a portion distant from the optical axis 1 by R ₀ , and in the direction of the angle α (counterclockwise is positive). A bright point T is generated on the object surface O, this bright point T is projected onto the observation surface 3 by the observation lens L, and the position of the image I projected onto this observation surface 3 is arranged on the observation surface 3. The distance to the object is measured by the position detecting photosensitive element P. When the distance from the optical axis 1 of the image I on the observation plane 3 is x, the theoretical image plane is expressed by the following equation.

Therefore, it is natural from the equation (1) that if the part of the observation surface corresponding to the gage point (marker) closer to the observation lens is moved away from the observation lens, the sign on the object will be blurred on the observation surface. Imaged a little.

FIG. 3 is a schematic view of a different case. This distance detection device is extremely widely used in recent years, and projects the light beam 5 onto the object plane O to position the image I of the bright spot T generated on the object O on the observation plane 3. Is detected to detect the distance in the light beam projection direction. Also in this distance detecting device, the position detecting light-sensitive element is conventionally arranged perpendicularly to the optical axis 1 of the observation optical system. The angle formed by the optical axis 6 of the light beam projection optical system and the optical axis 1 of the observation optical system is α, the focal length of the observation lens L is f, and the light beam is projected from the optical axis 1 of the observation lens L at the position of the observation lens L. When the distance to the optical axis 6 of the optical system is R ₀ , the theoretical image plane is similarly expressed by the equation (2). Therefore, the measurement accuracy is further improved by moving the observation surface corresponding to the closer gauge point away from the observation lens L.

(Embodiment) FIG. 4 is a schematic side view showing an embodiment of the present invention. The present invention is an improvement of the invention disclosed in JP-A-60-52710. The reflection mirror 7 is arranged in front of the observation lens L, and the bright spot T formed by projecting the light beam 5 onto the object surface O is once reflected by the reflection mirror 7 and then on the observation surface 3. The distance of the observation lens L in the optical axis 1 direction is detected from the position of the image I projected and projected on the observation surface 3. Also in the case of this embodiment, it is assumed that the inclination angle of the reflecting mirror 7 with respect to the optical axis 1 is φ and the focal length of the observation lens L is f.
Assuming a virtual observation lens L ′ at a position symmetrical to the observation lens L with respect to the reflecting mirror 7, a 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. Let R ₀ be the same as in the case of FIG. 3, and the surface satisfying the expression (2) becomes the theoretical image forming surface. Therefore, by arranging the position-sensing light-sensing element P as shown in the drawing so that the portion of the observing surface with respect to the closer gauge point is farther from the observing lens, the brilliant image is brighter regardless of the distance to the symmetrical object. The point T can be imaged.

The above is described two-dimensionally by using a sectional view with respect to the optical axis, but it goes without saying that the three-dimensional arrangement is exactly the same including the case where the device is rotationally symmetric with respect to the optical axis 1. Yes.

In the present invention, the observation surface, that is, the position detection light-sensitive element may have a curvature instead of a flat surface. Further, it is needless to say that the observation lens shown in each drawing according to each of the above-described examples is merely a conceptual representation of a condensing lens, and includes a single-lens compound lens.

(Effect) The present invention provides a miniaturized distance detection device provided with a reflecting mirror between an object and an observation lens that reflects the image of the sign so as to fold it back in the optical axis direction of the observation lens. Since the portion of the position detection light-sensitive element corresponding to the closer sign is located farther from the lens, good image formation can be performed on average over the entire area of the position detection light-sensitive element. Therefore, distance detection can be performed with high accuracy over a wide measurement range.

[Brief description of drawings]

1 to 3 are explanatory views for explaining the present invention, and FIG. 4 is a schematic view of an embodiment of the present invention. L ...... observation lens, L _P ...... projection _{lens, T, T 0, T 1} , T 2 ...... gauge _{(labeled) I, I 0, I 1} , I 2 ...... image, P ...... position detection light Sensitive element, O ... Object surface, 1 ... Optical axis of observation lens, 3 ... Observation surface, 4 ... Theoretical image plane, 5 ... Light beam, 7 ... Reflector

Claims (1)

[Claims] 1. An observation lens for forming an image of a mark on an object on an observation plane and projecting the light beam, and projecting a light beam along an optical axis of the observation lens to generate a light beam for forming the mark. Means, between the observation lens and the object, installed without traversing the optical axis of the observation lens, reflecting mirror for reflecting the image of the sign once and then folded back into the observation lens, And a position detection photosensitive element for detecting the position of the image of the sign image-projected on the observation surface, based on the position of the image of the sign on the position detection photosensitive element, up to the object A distance detecting device of a type that acquires distance information, characterized in that a portion of a position detection light-sensitive element corresponding to a sign closer to the observation lens is located farther from the observation lens.