JPH08219766A - Distance measuring sensor - Google Patents

Abstract

PURPOSE: To make sensing of high accuracy possible even in an asymmetrical light receiving intensity distribution by dividing a light receiving flux by a half-mirror, providing a distance measuring sensor with respective light receiving position detection elements, and arranging one detection element at a position near a light receiving lens in the best focus and the other detection element at another position remote therefrom. CONSTITUTION: A half-mirror 7 is provided during light collection of a light receiving lens 3, a light path is divided, and light receiving element J1 , J2 are provided for luminous fluxes, and the element J1 is set near the lens 3 from a position in the best focus and the other element J2 remote therefrom. In the case where luminous flux intensity incident on the lens 3 is uniform, it is a light receiving spot, and since a distance measuring error is large in the case where a strong part in the luminous flux exists, averaging a result wherein a distance or a displacement amount of the elements J1 , J2 to an object is calculated is used. Even if they are left and right asymmetrical light receiving spots due to the constitution, the error of the distance or the displacement amount is reduced and sensing of high accuracy is made possible, since the light receiving intensity distribution inverted before and after light collection is calculated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement sensor capable of measuring the amount of displacement of an object to be detected using the principle of triangulation and a scanning sensor / distance image sensor to which the displacement sensor is applied.

[0002]

2. Description of the Related Art Conventionally, by using triangulation, the light reflected from an object to be detected is condensed by a light receiving lens near the light projecting lens and the light receiving spot position on the light receiving element is detected to detect the light receiving spot. By calculating the distance to the object, the amount of displacement of the object, the distance to the object, and scanning, the line-shaped or planar-shaped displacement information / distance information was obtained.

[0003]

If the object to be detected is a diffuse reflective object such as paper or ceramic and there is no difference in surface texture depending on the location, the reflection pattern due to the difference in the position where the projected beam hits hardly changes. Is few. However, when a metal surface is ground, fine hairlines appear on the surface of the object to be detected, and when viewed in detail, the surface is a highly reflective surface with various angles, so the reflection pattern is uniform. Therefore, a portion of the light beam entering the light receiving lens has a portion having a high intensity, and the light receiving spot on the light receiving element is not symmetrical and the center of gravity moves. (FIG. 3) Since the irradiation position of the projection beam slightly shifts and the reflection pattern changes, there is a problem in that a displacement amount of 10 to 100 times the actual unevenness is detected. Also,
Depending on the orientation of an object with a large specular reflection component such as a glossy rubber or plastic surface, strong light will enter a part of the light beam entering the light-receiving lens. On the other hand, there was a problem that a large amount of displacement was output.

The present invention has been made in view of such a problem, and provides a distance measuring sensor that reduces the influence when a part of the light beam traveling from the object to be detected to the light receiving lens contains a light beam of high intensity. The purpose is to

[0005]

According to a first aspect of the present invention, a light flux is emitted from a light projecting unit to a detected object, and a part of reflected light from the detected object is received by a light receiving unit near the light projecting unit. In the distance measuring sensor that measures the distance to the detected object and the displacement of the detected object by the principle of triangulation, the light receiving part of the distance measuring sensor divides the received light beam by a half mirror, and the divided light beam Is equipped with a light receiving position detecting element that receives light respectively, and one light receiving position detecting element is arranged closer to the light receiving lens with respect to the best focus position, and the other light receiving position detecting element is provided with respect to the best focus position from the light receiving lens. It is characterized in that it is arranged at a distant position.

According to a second aspect of the present invention, in both of the light receiving position detecting elements, a means for adding the respective outputs on the side where the output is increased when the detected object is moved in a direction away from the detected object, and a direction in which the detected object is moved away. Characterized by comprising means for adding the respective outputs on the side where the output is reduced when moved to the position 1, and a distance measurement calculation circuit for performing the distance measurement calculation on the basis of these added signals. Is.

[0007]

According to the first aspect of the present invention, the light receiving element receives the light beam condensed by the light receiving lens on the side closer to the light receiving lens by the predetermined distance from the best focus position, and the light receiving element receives the light beam by the predetermined distance from the best focus position. Since the output of the light receiving element that receives light on the side far from the lens is calculated,
Even if a part of the received light beam has a high intensity part and has a non-symmetrical received light intensity distribution, it is canceled out and high-precision sensing becomes possible.

According to a second aspect of the present invention, the circuit becomes simpler and the cost can be reduced as compared with the configuration in which the outputs of both the light receiving position detecting elements are detected and the respective outputs are amplified. Since the number is small, the influence of circuit variation is small.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. An example is shown in FIG. The light projecting unit 1 includes a light emitting element (LD or LED) and a light projecting lens 2, and emits a light beam.
A light receiving lens 3 is provided in the vicinity of the light projecting lens 2, and a part of the reflected light from the detected object 4 is captured and guided to the light receiving element 5. The light receiving element 5 is a light receiving position detecting element (for example, PSD) capable of detecting the movement of the light receiving spot, and the distance to an object is measured by the calculation of two current values obtained from the light receiving element 5 according to the principle of triangulation. Light receiving position detection element is P
Instead of the SD, the light receiving elements may be arranged side by side.

The displacement amount Δx on the light receiving position detecting element (PSD) and the displacement amount Δr of the detected object are expressed by the following equations. Δxa = I1−I2 / I1 + 12 × L / 2 L: PSD length Δr = f (Δx) The half mirror 7 is arranged during light collection by the light receiving lens 3 to divide the optical path into two parts, and The light receiving elements J ₁ and J ₂ are arranged as a unit. The light receiving element J ₁ is arranged on the side closer to the light receiving lens 3 by a predetermined distance from the best focus position. The other light receiving element J ₂ is located on the side farther from the light receiving lens 3 by a predetermined distance from the best focus position.

When the intensity of the light beam incident on the light receiving lens 3 is uniform, the light receiving spots are substantially symmetrical. However, when a part of the received light beam has a strong intensity depending on the type and condition of the object to be detected. Has an effect on the light receiving spot. Since it is difficult to see in the diagram using the half mirror 7 in FIG. 1, an equivalent explanatory diagram is shown in FIG. As shown in FIG. 2, when a strong light flux is generated in a part of the reflected light, one peak is also generated in the light receiving element J ₁ in the vicinity of the skirt of the generally Gaussian distribution. The distance measurement error becomes large when a light flux portion having a high intensity exists in the peripheral portion of the received light flux, and therefore such an example is illustrated.

In the light-receiving element J ₁ , the portion of the received light beam having high intensity is on the opposite side to that of J ₁ . The result of calculating the distance to the object and the displacement amount of the object from the output of the light receiving element J ₁ and the result of calculating the distance to the object and the displacement amount of the object from the output of the light receiving element J ₂ are averaged. In the case where the optical system is not ideal or the variation of the circuit system is absorbed, one of the calculation results may be weighted and averaged.

With this configuration, even if the light receiving spot is not symmetrical, the light receiving intensity distribution that is inverted before and after focusing is calculated, so that the secondary intensity peaks that cause the movement of the center of gravity are offset. Therefore, the error between the actual distance and the amount of displacement can be reduced. FIG. 4 shows another embodiment. In both the light receiving position detecting elements J ₁ and J ₂ , the output i on the side where the output ratio increases when the detected object 4 is moved in the away direction. ₁ and i ₁ ′ are added, and the outputs i ₂ and i ₂ ′ on the side where the output ratio becomes smaller when the detected object 4 is moved away from each other are added,
After that, a distance measurement calculation circuit 8 for performing a distance measurement calculation based on these added signals is provided.

According to this structure, both light receiving positions
Sensing element J₁, J₂Each output i of ₁, I₂I₁′,
i₂′ Is detected and the output i of each of these is detected.₁, I₂;
i₁′, I ₂Compared to the configuration that amplifies ′ by installing an amplifier
Amplification of the circuit, cost reduction, and amplification
Since the number of circuits is small, the influence of circuit variation is small.
Things.

[0015]

According to the first aspect of the present invention, the light receiving element that receives light on the side closer to the light receiving lens by a predetermined distance from the best focus position of the light beam condensed by the light receiving lens, and the predetermined distance from the best focus position. However, because the output of the light receiving element that receives light on the side far from the light receiving lens is calculated, even if there is a part of the received light beam with a strong intensity and the received light intensity distribution is not symmetrical, it is offset This has the effect of enabling high sensing.

According to a second aspect of the present invention, in both of the light receiving position detecting elements, the means for adding the respective outputs on the side where the output ratio increases when the detected object is moved away from the detected object, Since it is provided with a means for adding each output on the side where the output ratio becomes smaller when moved in the direction to move away, and a distance measurement calculation circuit for performing distance measurement calculation based on both added signals thus added, Compared to the configuration that detects each output of both light receiving position detection elements and amplifies each output, the circuit becomes simpler, cost can be reduced, and the number of amplifier circuits can be reduced, so the influence of circuit variation It has the advantage of being less.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention.

2A is an operation explanatory view, FIG. 2B is an output waveform diagram of a light receiving element J ₁ , and FIG. 2C is an output waveform diagram of a light receiving element J ₂ .

FIG. 3A is an explanatory diagram for obtaining a light-receiving spot line image intensity distribution on a white paper (diffusion surface), and FIG. 3B is a distribution diagram thereof.
(C) is an explanatory view for obtaining a light-receiving spot line image intensity distribution on a copper plate (grinding hairline surface), and (d) is a distribution diagram thereof.

FIG. 4 is a block circuit diagram of another embodiment.

[Explanation of symbols]

 1 Emitter 4 Object to be detected 5 Light receiving element 7 Half mirror

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[Procedure amendment]

[Submission date] July 3, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

The displacement amount Δx on the light receiving position detecting element (PSD) and the displacement amount Δr of the detected object are expressed by the following equations. Δxa = [(I ₁ −I ₂ ) / (I ₁ + I ₂ )] × (L / 2) L: PSD length Δr = f (Δx) The half mirror 7 is arranged during light collection by the light receiving lens 3. Then, the optical path is divided into two, and the light receiving elements J ₁ and J ₂ are arranged for each light flux. The light receiving element J ₁ is arranged on the side closer to the light receiving lens 3 by a predetermined distance from the best focus position. The other light receiving element J ₂ is located on the side farther from the light receiving lens 3 by a predetermined distance from the best focus position.

Claims (2)

[Claims] 1. A light flux is emitted from a light projecting unit to an object to be detected,
A distance measuring sensor that receives a part of the reflected light from the detected object by the light receiving part near the light emitting part and measures the distance to the detected object and the displacement of the detected object by the principle of triangulation. As a light-receiving part of the distance measuring sensor, it is equipped with a light-receiving position detecting element that splits the light-receiving luminous flux by a half mirror and receives each of the divided luminous fluxes. One light-receiving position detecting element is closer to the light-receiving lens with respect to the best focus position. A distance measuring sensor, which is arranged at a position, and the other light receiving position detecting element is arranged at a position far from the light receiving lens with respect to the best focus position. 2. In both of the light receiving position detection elements, a means for adding respective outputs on the side where the output ratio increases when the detected object is moved away from the detected object, and the detected object is moved away from the detected object. In this case, it is provided with means for adding respective outputs on the side where the ratio of the outputs is reduced, and a distance measurement calculation circuit for performing distance measurement calculation on the basis of these added signals. The distance measuring sensor according to Item 1.