JPH05240640A - Optical distance measuring device - Google Patents

Abstract

PURPOSE:To perform measurement accurately without being affected by surface state of a target object and miniaturize the shape of a device and improve measurement accuracy as compared with a trigonometrical distance measuring system by detecting distance to the target object according to change in light spot size while the target object and a light-reception element are not in image- forming relationship in an optical distance measuring device. CONSTITUTION:A light which irradiated from a light emitting element 1 and is reflected by a target object M is received by a light reception element 3. At this time, the size of light spot on the light reception element changes according to the distance to the target object M and the quantity of received light at each region differs since the light reception element 3 is divided into at least three regions. The distance to the target object M can be detected based on it.

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 optically detecting the presence or absence of an object or the distance to an object by using a light receiving element and a light receiving element.

[0002]

2. Description of the Related Art As a conventional optical distance measuring device of this type, there is a photoelectric sensor device using a triangular distance measuring method as shown in FIG. This sensor device includes a light emitting element 101 and a light projecting lens 102, which are semiconductor lasers for projecting light.
Position detector for light reception (POSITION / SENSI)
NG / DEVICE (hereinafter referred to as PSD) 103, a light receiving lens 104, a laser drive circuit 105 that drives the light emitting element 101, an amplifier 106 that amplifies a signal from the PSD 103, and the like. Then, the light emitting element 101 projects the light onto a target object (A, B, etc.), and the reflected light of the light spot is imaged on the PSD 103 by the light receiving lens 104, and the position of the light spot on the PSD 103 due to the position change of the target object. A change, that is, a change in the position of the center of gravity is detected.

[0003]

However, in this conventional apparatus, since the target object and the PSD 103 are in an image-forming relationship, the center of gravity of the light spot depends on the surface state of the target object (for example, color change or surface step). The position changes and errors easily occur. Further, since the triangulation method is used, the accuracy is deteriorated unless the distance between the light projecting lens and the light receiving lens is increased as the measuring distance becomes longer, which causes a problem that the entire shape of the apparatus becomes large.

The present invention has been made by paying attention to such a conventional problem. The object and the light receiving element are not in an image forming relationship, and the distance to the object is detected from the change of the light spot size. By doing so, it is possible to perform accurate measurement without being affected by the surface condition of the target object, and to reduce the size of the device compared to the triangulation method, and to improve the measurement accuracy. The purpose is to provide.

[0005]

In order to achieve the above object, an optical distance measuring apparatus of the present invention comprises a light emitting element and at least three light-receiving elements that receive reflected light emitted from the light emitting element and reflected by a target object. The light receiving element is divided into areas, and the distance to the target object is detected based on the amount of light received in each of at least three areas of the light receiving element.

Further, the present apparatus has two condensing means for condensing the reflected light emitted from the light emitting element and reflected by the target object, and the light receiving element divided into at least three regions condenses one of them. Each of the light receiving elements is composed of an element for receiving the reflected light condensed by the means before the condensing point and an element for receiving the reflected light condensed by the other condensing means behind the condensing point. The distance to the target object may be detected based on the amount of received light. Further, it may have a plurality of light receiving systems having different detection ranges of the target object.

Further, the light receiving element is divided into five regions, which are a central portion, both side portions thereof, and both outer side portions thereof, and has a plurality of arithmetic circuits for outputting distance information of the target object from each received light amount. Alternatively, the distance of the target object may be detected based on the output of any one of the arithmetic circuits. Further, the light receiving element is divided into at least three regions of the central portion and the other portion by at least two dividing lines, and the light emitting element, the target object, and the light receiving element are arranged in the longitudinal direction of the belt-shaped region of the central portion. The width may be set to be substantially parallel to the included plane, or the width of the belt-shaped region in the central portion may be gradually increased from one end portion to the other end portion. Alternatively, an element having a minute light emitting region may be used as the light emitting element.

[0008]

According to the above structure, the light receiving element receives the reflected light emitted from the light emitting element and reflected by the target object. At this time, the size of the light spot on the light receiving element changes according to the distance to the target object, and since the light receiving element is divided into at least three regions, there is a difference in the amount of light received in each region. The distance to the target object can be detected based on this.

[0009]

1 shows the optical system of an optical distance measuring device according to a first embodiment of the present invention. The present embodiment corresponds to the inventions of claims 1 and 2, and includes a light emitting element 1 and the light emitting element 1.
And a target object M1, M2, M3 located on its optical path, etc. (collectively M)
A light receiving lens 4 and a light receiving element (PSD) 3 for receiving the reflected light reflected by The light-receiving element 3 is arranged in front of the focal point position of the reflected light. Further, the light receiving element 3 is divided into at least three strip-shaped regions 3a, 3b, 3c as shown in FIG. The divided structure is such that the boundary direction of each strip-shaped region is the light emitting element 1,
It is substantially parallel to the plane including the target object M and the light receiving element 3 (corresponding to the invention of claim 7). Further, the light receiving element 3
Is connected to an arithmetic circuit 6 which outputs a detection signal P0 corresponding to the amount of light received in each area. The central area 3a is the negative terminal of the arithmetic circuit 6 and the outer areas 3b, 3
c is connected to the plus terminal of the arithmetic circuit 6.

As shown in FIGS. 2 and 3, the size of the light spot on the light receiving element 3 changes depending on the distance to the target object M. That is, the target objects M1, M2, M from the near side
The size of the light spot changes to S1, S2, and S3 corresponding to 3, and therefore the amount of received light changes. FIG. 3 shows the relationship between the distance to the target object M and the output voltage from the light receiving element 3. The large light spot S1 has a larger ratio of the amount of light received by the regions 3b and 3c of the outer side portions to the region 3a of the central portion than that of the small light spot S3, for example. As a result, output voltages P1, P2, P3 are obtained corresponding to the light spots S1, S2, S3, respectively. The distance of the target object M can be detected from this output voltage. If a light source (light emitting element 1) having a small light receiving diameter is used, the change in spot shape becomes large and the sensitivity becomes high.

FIG. 4 shows a second embodiment. This example
Similarly, it corresponds to the invention of claims 1 and 2, and the lens 7
Is used both for projecting and receiving light, and a half mirror 8 is disposed in the optical path between the light emitting element 1 and the lens 7 so that the reflected light split by the half mirror 8 is received by the light receiving element 3. .. According to this embodiment, the device can be downsized.

FIG. 5 shows a third embodiment. This example
Similarly, it corresponds to the invention of claims 1 and 2, and
In this embodiment, the light projecting lens 2, the light receiving lens 4, and the light receiving element 3
In the third embodiment, the light receiving lens 4 and the light receiving element 3 are tilted and arranged at right angles to the optical axis of the reflected light. Thereby, the distortion of the light spot on the light receiving element 3 can be reduced, and the sensitivity and the measurement range can be expanded.

FIG. 6 shows a fourth embodiment. This example
According to the invention of claim 4, a half mirror 8 is arranged behind the light receiving lens 4 to divide the light flux, and one of the light receiving elements 31 and 32 is provided in front of the focal point and the other is provided for the respective optical paths. Is located behind the focal point. Each light receiving element 31, 32
Is divided into three in the same manner as described above. In this configuration, a differential optical system can be formed and the detection sensitivity can be increased by taking the difference between the detection outputs of the light receiving elements 31 and 32.

FIG. 7 shows a fifth embodiment. This example
According to the invention of claim 4, the half mirror 8 arranged to divide the light beam behind the light receiving lens 4 is tilted by 45 degrees or more from the vertical direction with respect to the optical axis.
The two light receiving elements 31 and 32 are arranged on the same plane so that they can be provided in the same package. This configuration facilitates adjustment.

FIG. 8 shows a sixth embodiment. This example
According to the invention of claim 3, two sets of light receiving lenses 41, 42 and light receiving elements 31, 32 for receiving the reflected light from the target object M are provided, and one light receiving element 31 is in front of the focus and the other. The light receiving element 32 of is provided behind the focal point. As a result, the same effect as that of the embodiment of FIG. 6 is obtained, and the attenuation of the light quantity is reduced, so that the measurement distance can be expanded.

FIG. 9 shows another embodiment of the light receiving element 3. This example corresponds to the invention of claim 6, and the light receiving element 3
Is divided into five, and is composed of a central region 3a, regions 3b and 3c on both sides thereof, and regions 3d and 3e on both outer sides thereof. Then, with respect to the region 3a of the central portion, the regions 3b, 3 of the one side portion and the outside portion thereof.
d, and an arithmetic circuit 61 that outputs distance information of the target object from the ratio of the amount of light received in the regions 3c and 3e of the other side portion and the outer side portion thereof, and the central portion and the regions 3a and 3b of both side portions thereof. Regions 3d and 3 of each outer part with respect to 3c
An arithmetic circuit 62 for outputting distance information of the target object from the ratio of the amount of received light of e is provided. If the outputs given to the plus terminals of the arithmetic circuits 61 and 62 are P ′ and P ″ and the detection outputs of the arithmetic circuits 61 and 62 are P10 and P20,
When (P ′ / sum signal) or (P ″ / sum signal) is larger than a certain threshold level, the output P20 is used as the distance signal, and when it is small, the output P10 is used as the distance signal without deterioration of sensitivity. The measurement range can be expanded.

FIG. 10 shows a seventh embodiment of this device. This embodiment corresponds to the invention of claim 5, in which a plurality of light receiving systems for receiving the reflected light from the target object M are provided and the measurement areas are shared, that is, different measurement areas are complemented by each other. This is intended to expand the measurement range as a whole. That is, in the illustrated embodiment, in the left and right light receiving systems, the light receiving elements 31 and 32 are located in front of the focal positions of the light receiving lenses 41 and 42, but at positions relatively different from each other. Besides this example, the same effect can be obtained even if the focal length of one lens is different from that of the other lens, or if the division configuration of one light receiving element is different from that of the other. Further, there may be three or more light receiving systems, and in that case, the measurement range can be further expanded.

FIGS. 11A and 11B show still another embodiment of the light receiving element. This example corresponds to the invention of claim 8, and in each of the light receiving elements 3, the width of the band-shaped region in the central portion among the light receiving regions divided into three is as shown by the boundary lines 11 and 12, It gradually increases from one end to the other. When any of the light receiving elements 3 is used in the state shown in FIG. 1, since a light spot is formed on the right side of the light receiving region as the target object is farther away, as shown in FIG. When the width of the band-shaped region is wide, the sensitivity can be improved. On the other hand, as shown in (b), when the width of the belt-shaped region in the central portion becomes narrower toward the right, the measurement range can be expanded.

Further, as the light emitting device, a light emitting device having an ohmic contact structure and having a minute light emitting region as shown in Japanese Patent Application Laid-Open No. 3-237784 filed by the present applicant may be used. (Corresponding to the invention of claim 9). By using such a light emitting element, a high output can be obtained in a minute light emitting region, so that the emitted light diameter can be reduced, and the change of the light spot shape on the divided light receiving element becomes large with respect to the distance change of the target object. The sensitivity of is improved.

[0020]

As described above, according to the first to ninth aspects of the invention, the reflected light from the target object is not focused, that is, the light receiving element receives the spot at the defocus position, and the light receiving element is divided. Since the change in the amount of received spot light in the light receiving region is observed, the distance to the target object can be stably measured without being affected by the surface shape or color of the target object. Further, since the divided light receiving element is used instead of the position detecting element, the circuit configuration for detection becomes simple.
Also, since it is not a triangulation method, the distance between the light emitting lens of the light emitting system and the light receiving lens of the light receiving system can be minimized because it is not related to the measurement accuracy, and the device can be downsized, In some cases, the light projecting lens and the light receiving lens can be coaxial, that is, both lenses can be shared.

According to the third and fourth aspects of the invention, since the differential optical system can be constructed, the measurement accuracy is improved,
The dynamic range can be expanded. According to the invention of claim 5, since a plurality of light receiving systems are provided and different measurement areas are complemented to each other, the measurement range can be expanded. According to the invention of claim 6, by switching and using the arithmetic circuit according to the signal level, it is possible to expand the measurement range while degrading the sensitivity. According to the invention of claim 7, since the dividing direction of the divided light receiving element is parallel to the plane including the light emitting element, the light receiving element, and the target object, even if there is a step due to expansion of the dynamic range and division of the element, The influence of the step can be eliminated. According to the eighth aspect of the invention, since the divisional configuration of the light receiving element is changed, the sensitivity can be improved and the measurement range can be expanded without changing the optical system. According to the invention of claim 9, the diameter of the emitted light can be reduced and the change of the spot shape on the light receiving element becomes large, so that the measurement sensitivity can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical system of an optical distance measuring device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a light receiving element and a detection circuit of this device.

FIG. 3 is a characteristic diagram of an output voltage of a light receiving element.

FIG. 4 is a diagram showing an optical system of the present device according to a second example.

FIG. 5 is a diagram showing an optical system of the present device according to a third example.

FIG. 6 is a diagram showing an optical system of the present device according to a fourth example.

FIG. 7 is a diagram showing an optical system of the present device according to a fifth example.

FIG. 8 is a diagram showing an optical system of the present device according to a sixth embodiment.

FIG. 9 is a configuration diagram showing another example of a light receiving element and a detection circuit.

FIG. 10 is a diagram showing an optical system of the present device according to a seventh example.

FIG. 11 is a configuration diagram showing still another example of the light receiving element.

FIG. 12 is a configuration diagram of a conventional optical distance measuring device.

[Explanation of symbols]

 1 Light-Emitting Element 3 Light-Receiving Element 4 Light-Receiving Lens (Condensing Means) 6 Arithmetic Circuit M Target Object

Claims (9)

[Claims] 1. A light emitting device, and a light receiving device divided into at least three regions for receiving reflected light emitted from the light emitting device and reflected by a target object, and each of the at least three regions of the light receiving device. An optical distance measuring device characterized by detecting the distance to a target object based on the amount of received light. 2. A light emitting element, a condensing means for condensing the reflected light emitted from the light emitting element and reflected by a target object, and at least three light receiving means for receiving the reflected light condensed by the condensing means. An optical distance measuring device, comprising: a light receiving element divided into areas, and detecting a distance to a target object based on each amount of received light in at least three areas of the light receiving element. 3. A light emitting element, two light collecting means for collecting reflected light emitted from the light emitting element and reflected by a target object, and light collecting means for collecting light by one of the two light collecting means. A light receiving element divided into at least three regions for receiving reflected light in front of the converging point, and at least three light receiving elements for receiving reflected light condensed by the other condensing means behind the converging point. An optical distance measuring device, comprising: a light receiving element divided into areas, and detecting a distance to a target object based on each amount of received light in at least three areas of the light receiving element. 4. A light emitting element, a condensing means for separating and condensing the reflected light emitted from the light emitting element and reflected by a target object into two light fluxes, and a converging means for separating the light.
The first divided into at least three regions for receiving one of the two condensed light beams in front of the converging point
And a second light receiving element divided into at least three regions for receiving the other light beam of the two light beams separated and condensed by the light condensing means, at least three regions. An optical distance measuring device characterized by detecting the distance to a target object based on the amount of light received in each of the divided regions of the first light receiving element and the second light receiving element. 5. A light emitting element, a condensing means for condensing the reflected light emitted from the light emitting element and reflected by a target object, and at least three regions for receiving the reflected light condensed by the condensing means. Consisting of divided light receiving elements,
An optical distance measuring device, comprising: a plurality of light receiving systems having different detection ranges of the target object, and detecting the distance of the target object based on each light receiving amount of at least three regions of the light receiving element of the light receiving system. apparatus. 6. A light emitting device, and a light receiving device for receiving reflected light emitted from the light emitting device and reflected by a target object, wherein the light receiving device comprises a central portion, both side portions thereof,
It is divided into five areas consisting of the outer side portion and both outer side portions, and the distance information of the target object is obtained from the respective light receiving amounts of the central portion, the one side portion and the outer side portion, and the other side portion and the outer side portion. An arithmetic circuit for outputting, and an arithmetic circuit for outputting distance information of a target object from respective light receiving amounts of three regions of a central portion and both side portions thereof, one outer portion, and the other outer portion are provided. An optical distance measuring device characterized by detecting the distance of a target object based on the output of a circuit. 7. The light-receiving element is divided by at least two dividing lines into at least three regions of a central portion and the other portion, and the longitudinal direction of the belt-shaped region of the central portion is such that the light-emitting element, the target object, and The optical distance measuring device according to claim 1, wherein the optical distance measuring device is substantially parallel to a plane including the light receiving element. 8. The light receiving element is divided into at least three strip-shaped regions other than the central portion by at least two dividing lines, and the width of the strip-shaped region of the central portion is from one end to the other end. The optical distance measuring device according to any one of claims 1 to 6, wherein the optical distance measuring device is gradually increased. 9. The optical distance measuring device according to claim 1, wherein an element having a minute light emitting region is used as the light emitting element.