JPH0510755A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To measure with high accuracy the distance from the surface of an object to be measured. CONSTITUTION:A distance measuring apparatus is provided with a light detection means 12 having at least two light detecting portions 12A,12B, and an image-forming optical element 10 which provides substantially the same light to the two light detecting portions 12A,12B when receiving light from a predeteremined direction from the surface 6 of an object to be measured. The distance to the surface of the object to be measured is measured according to the amount that the image-forming optical element moves when the outputs of the two light detecting portions become substantially the same.

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 for measuring a distance to an object surface according to the principle of triangulation.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional distance measuring device of this type. The light beam emitted from the light emitting element 2 is condensed by the light projecting lens 4 into a minute spot on the object surface 6 to be measured. Diffuse reflected light from the object plane 6 is condensed by a light-receiving lens 8 on a position sensor 9 made of PSD, and the distance to the object plane is determined according to the principle of triangulation according to the position of a condensed spot on the sensor 9. Is measured.
The distance L from the light projecting lens 4 to the object plane 6 is x, the distance from the light emitting element 2 to the position sensor 9 is y, the distance from the light emitting element 2 to the light projecting lens 4 is y, and the light receiving from the light projecting lens 4 is If the distance to the lens 8 is D, then L = yD / (x-
It can be represented by D).

[0003]

However, in the above-mentioned conventional distance measuring device, when the LED is used as the light source, the distance resolution can be secured only about 10% of the measuring distance, and the measuring accuracy is poor. There was a point.

The present invention has been made in view of such a situation, and an object thereof is to provide a distance measuring device having high measurement accuracy.

[0005]

According to a first aspect of the present invention, there is provided a distance measuring device having a light detecting means having at least two light detecting portions, and a light detecting means which receives light from a surface of an object to be measured in a predetermined direction. The imaging optical element that gives substantially the same light to the two photodetection units, and the imaging optical element is moved so that the imaging optical element can receive light from the object surface to be measured from a predetermined direction. And a moving unit for moving the moving amount of the imaging optical element when the outputs of the two photodetectors are substantially equal to each other, and the distance to the object surface to be measured is measured. .

According to a second aspect of the present invention, there is provided a distance measuring device, a light emitting element, a light projecting lens for condensing a light beam emitted from the light emitting element into a minute spot on the object surface to be measured, and a light projecting lens from the object surface. And a light-receiving lens for condensing the diffusely-reflected light on the imaging optical element.

According to a third aspect of the distance measuring device, the image forming optical element has a symmetrical structure, and the predetermined direction is a direction along the axis of symmetry.

[0008]

In the distance measuring device having the structure according to the first aspect of the present invention, the imaging optical element is moved so that the outputs of the two photo-detecting sections become equal, that is, the differential outputs thereof become zero. Since the distance to the object surface is measured based on this movement amount, the distance can be measured with high accuracy.

In the distance measuring device having the structure of the second aspect, the light beam emitted from the light emitting element is condensed into a minute spot on the object surface to be measured by the light projecting lens.
Since the diffusely reflected light from the object surface is focused on the imaging optical element by the light receiving lens, it is possible to measure the distance with high accuracy even if the object surface itself to be measured does not emit light.

In the distance measuring device having the structure of the third aspect, the predetermined direction is the direction along the axis of symmetry, which facilitates the design.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of one embodiment of a distance measuring device, that is, a lateral distance type photoelectric sensor of the present invention. Light emitting element 2,
The light projecting lens 4, the object surface 6 to be measured, and the light receiving lens 8 are the same as those in the conventional apparatus shown in FIG. However, the light-receiving lens 8 does not collect the diffused / reflected light from the object plane 6 on the position sensor 9 made of the PSD of the conventional device, but on the wedge prism 10.

The wedge prism 10 is moved left and right with respect to the optical axis by moving means (not shown) so that the diffuse reflection light from the object surface 6 to be measured is condensed by the light receiving lens 8 at the apex of the wedge prism 10. It is possible. When the condensing point is at the apex of the wedge prism 10, the condensing beam is divided into two, and each is divided into two.
(Photodetector) Two photodetectors 12A and 12 of 12
B (see FIG. 1 (a)). That is, when the wedge prism 10 receives light from the object surface 6 to be measured from a predetermined direction, the wedge prism 10 gives substantially the same light to the two light detection units 12A and 12B.

When the position of the object surface 6 to be measured changes in the vertical direction in the drawing, the light collecting position of the light from the object surface 6 to be measured is displaced in the left-right direction in the drawing with respect to the position of the prism 10. When the object surface 6 to be measured moves away from the position shown in FIG. 1A in the upward direction of the drawing, the light collection position from the object surface 6 to be measured is shifted to the left as shown in FIG. Detector 1
The focused beam is guided only to 2B. Here, if the prism 10 is moved to the left according to the movement of the condensed beam,
(As shown in FIG. 1A, the two photodetectors 12A and 12A are
B is provided with a substantially identical focused beam. Therefore, it is possible to measure the distance from the movement amount of the wedge prism 10 to the object surface 6 to be measured when the outputs of the two photodetectors 12A and 12B become substantially the same.

FIG. 2 shows an embodiment of the present invention in which a micro prism 20 having a bilaterally symmetrical structure is provided instead of the wedge prism 10 of FIG. The micro prism 20 is a micro prism 20 such as a wedge prism arranged at the center, and micro triangular prisms are arranged on the left side and the right side. Note that FIG. 2A shows a case where the condensing point is at the apex of the bilaterally symmetric minute prism of the microprism 20, and the condensing beam is divided into two, as in FIG. (Light detecting means) 12 is guided to two light detecting portions 12A and 12B. 2 (b) is shown in FIG.
Similar to (b), the measurement target object surface 6 moves away from the measurement target object surface 6 in the upward direction of the drawing, and the light collection position of the light from the measurement target object surface 6 shifts to the left. It shows where they were led.

Instead of the micro prism 20, a blaze type grating can be used. The blazed grating is an element that bends the optical path by diffraction and is a blazed type (sawtooth shape) so that the first-order diffracted light can be obtained with high efficiency, and has a bilaterally symmetrical structure like a micro prism. The blazed grating has the same function as the micro prism.

In the above-mentioned embodiment, the object surface 6 to be measured does not emit light, but the present invention can be applied to the case where the object surface 6 to be measured emits light. In this case, the light emitting element 2
Further, the light projecting lens 4 is unnecessary.

Further, instead of the wedge prism, the micro prism, etc., a hologram element having the same function can be used.

Furthermore, instead of the two-part PD, two independent PDs are used.
One photo detector may be used. In short, any photo-detecting means having at least two photo-detecting sections may be used.

[0019]

According to the distance measuring device of the first aspect, the light detecting means having at least two light detecting portions,
When receiving light from the object surface to be measured from a predetermined direction,
An imaging optical element that gives substantially the same light is provided to the two photodetector units, and the amount of movement of the imaging optical device when the outputs of the two photodetector units are substantially the same is used. Since the distance to the object surface to be measured is measured, the distance can be measured with high accuracy.

According to the distance measuring device of the second aspect,
The light beam emitted from the light emitting element is focused by the light projecting lens to a minute spot on the object surface to be measured, and the diffuse reflection light from the object surface is focused on the imaging optical element by the light receiving lens. Therefore, the distance can be measured with high accuracy even if the object surface itself to be measured does not emit light.

According to the distance measuring device of the third aspect,
Since the imaging optical element has a symmetrical structure and the predetermined direction is along the axis of symmetry, the design becomes easy.

[Brief description of drawings]

FIG. 1 is an optical configuration diagram showing a configuration of an embodiment of a distance measuring device of the present invention.

FIG. 2 is an optical configuration diagram showing the configuration of another embodiment of the distance measuring device of the present invention.

FIG. 3 is an optical configuration diagram showing a configuration of an example of a conventional distance measuring device.

[Explanation of symbols]

10 wedge prism 12 2 division PD (light detection means) 12A 12B Photodetector 20 micro prism

Claims (3)

[Claims] 1. A light detecting means having at least two light detecting portions, and when receiving light from an object surface to be measured from a predetermined direction,
An image forming optical element that gives substantially the same light to the two light detecting portions; and the image forming optical element so that the image forming optical element can receive light from the object surface to be measured from the predetermined direction. Distance to the object surface to be measured based on the amount of movement of the imaging optical element when the outputs of the two photodetectors are substantially the same. A distance measuring device characterized by measuring. 2. A light emitting element, a light projecting lens for condensing a light beam emitted from the light emitting element into a minute spot on the object surface to be measured, and diffused reflected light from the object surface for forming the image. The distance measuring device according to claim 1, further comprising a light-receiving lens that collects light on the optical element. 3. The imaging optical element has a symmetrical structure,
The distance measuring device according to claim 1 or 2, wherein the predetermined direction is a direction along an axis of symmetry.