JP3224711B2 - Distance measuring device - Google Patents

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 between objects, and is used as a visual sensor or the like for a computer to recognize the condition of an external space.

In a personal computer, as the user group expands and penetrates into daily life, it has become an important factor to be easy to use and familiar with. A visual sensor is a human interface that is indispensable for communication between a computer and a human. Therefore, it is desired to provide an inexpensive visual sensor suitable for personal use.

[0003]

2. Description of the Related Art As a distance measuring means for automatic focus adjustment of a camera, a triangulation type distance measuring device for measuring a deviation between a light projecting direction and a light receiving direction of detection light is widely used. Generally, this type of distance measuring device includes an infrared light emitting element and a PSD (position detection type detector).
And transmitting and receiving the modulated infrared light to prevent erroneous detection. A technique is known in which a light emitting element for a long distance and a light emitting element for a short distance are provided in order to increase the distance measurement accuracy, and these are switched and used so that the amount of received light falls within an appropriate range. 63-28
2611).

On the other hand, in an industrial robot, a triangulation type distance measuring device is used as a visual sensor similarly to a camera. However, the range of measurement (field of view) that can be measured by one rangefinder is narrow. Therefore, especially in a mobile robot or the like, a plurality of distance measuring devices are arranged so that the light projecting directions (distance measuring directions) are different from each other in order to expand the distance measuring range, and the distance measuring devices are simultaneously driven or sequentially driven. Objects and moving targets are being detected.

[0005]

As described above, a method of expanding the distance measurement range by appropriately arranging a plurality of distance measuring devices includes a method of expanding the distance measurement range by scanning the distance measuring device itself or a distance measuring beam. In comparison, there is no mechanical moving part, which is advantageous in terms of reliability and maintenance.

However, conventionally, if the range of measurement is further expanded or the range of measurement is subdivided to increase the resolution, the number of light-emitting elements and light-receiving elements constituting the rangefinder increases by the same number, and the number of parts increases. However, there is a problem that the number increases significantly. In particular, when the detection light is modulated, the number of modulation circuits and the number of light receiving circuits for extracting the modulated light similarly increase, so that the configuration becomes complicated and the cost increases accordingly.

The present invention has been made in view of such a problem, and an object of the present invention is to realize measurement of an inter-object distance in a two-dimensional space with as few parts as possible.

The distance measuring apparatus according to the first aspect of the present invention is provided for each of two or more M distance measuring directions radially extending along a virtual plane, and is provided in front of each of the distance measuring directions. M light-emitters that emit detection light toward the illuminator, and at respective positions away from the virtual plane , each light-receiving area is provided as common photoelectric conversion means for the M light-emitters.
And two or more N photodetectors arranged so as to include all of the M distance measurement directions, and reflected at different positions on the optical axis of the projector in each of the distance measurement directions. The detection light is selectively applied to the N according to their reflection position.
Light receiving range limiting means for making the light incident on the photodetectors,
Distance measuring direction switching means for selectively emitting the M light projectors one by one in order .

A distance measuring apparatus according to a second aspect of the present invention,
The photodetectors are arranged along a plane orthogonal to the virtual plane. In a distance measuring apparatus according to a third aspect of the present invention, an N-stage slit is provided as the light receiving range limiting means.

In a distance measuring apparatus according to a fourth aspect of the present invention, as the light receiving range limiting means, M lenses are arranged on a plane parallel to the virtual plane. The distance measuring apparatus according to the invention of claim 5 is provided one for each of two or more M distance measuring directions radially extending along the virtual plane,
M light emitters for emitting detection light forward in each of the distance measurement directions, and the M distance light meters located at a distance from the virtual plane as common photoelectric conversion means for the M light emitters
A position detection type photodetector that is arranged so that all of the directions are included in the light receiving range, and outputs a signal corresponding to the incident light amount distribution in the detection axis direction along a plane orthogonal to the virtual plane; In the distance measurement direction, the detection light reflected at different positions on the optical axis of the light projector, the light receiving range limiting means for causing the light receiving surface of the light detector to enter different positions in the detection axis direction on the light receiving surface, The M projectors are 1
Distance measurement direction switching means for selectively emitting light in order one by one ;
Having.

In a distance measuring apparatus according to a sixth aspect of the present invention, a microphone is arranged between the light projector and the light detector.

[0012]

Each of the N photodetectors can detect the reflected light of the detection light emitted from all the light projectors.

[0013] The M light projectors are alternatively selected by the distance measuring direction switching means. The selected light emitter emits the detection light in the corresponding distance measurement direction. If there is an object (including a human body) on the optical axis of the detection light, that is, in the distance measurement direction, the detection light reflected on the surface of the object enters one of the N photodetectors.

When the photodetector detects the detection light, it is known that the object exists in the virtual plane (two-dimensional space of the object to be measured), and the object exists depending on which projector is selected at that time. You can see the direction. The distance between the objects can be determined based on which of the N photodetectors has detected the detection light.

When a position detection type photodetector that outputs a signal corresponding to the distribution of incident light amount in the detection axis direction is used, the distance between objects can be measured with one photodetector.

[0016]

FIG. 1 is a block diagram showing a functional configuration of a distance measuring apparatus 1 according to the present invention. The distance measuring device 1 includes an optical system 10 that emits detection light and outputs a photoelectric conversion signal corresponding to a distance between objects.
And a control system 20 that controls the projection of light by the optical system 10 and processes the photoelectric conversion signal, and is used, for example, as visual information input means of an object recognition system.

The optical system 10 has seven light projectors 11, five light detectors 12, and a slit 13 as an optical means for limiting the light receiving range of each light detector 12. Each projector 11 includes an infrared light emitting diode and a condenser lens. Each photodetector 12 includes an imaging lens and a phototransistor.

The control system 20 has an MPU (microprocessor) functioning as a distance measuring direction switching means.
unit 21, a modulation circuit 22 for blinking the detection light at a frequency of about 40 kHz, a driver circuit 23 for supplying a drive current to each of the projectors 11, an amplification circuit 24 for amplifying the output (light reception signal) of each of the photodetectors 12, A band-pass filter 25 for extracting a modulation component corresponding to the detection light from the received light signal, an A / D converter 26 for quantizing the extracted modulation component, and external visual information such as a personal computer for measuring the distance measurement result. It has a host interface 27 for transmitting to the processing means (host).

Although not shown, the MPU 21 is composed of a CPU for executing a program, a ROM in which a program and operation data are stored in advance, a RAM serving as a work area for executing the program, and an I / O port. ing.

FIG. 2 is an external view of the optical system 10, FIG. 3 is a sectional view taken along the arrow III in FIG. 2, FIG. 4 is a sectional view taken along the arrow IV in FIG.
FIG. 2 is a diagram illustrating the principle of distance measurement by the optical system 10. In addition,
FIG. 2A is a plan view of the optical system 10, and FIG. 2B is a front view of the optical system 10.

In these figures, the optical system 10 has a block 15 made of black resin as a base. The block 15 is a molded body in which a spherical crown-shaped lower block 15a in which five slits 13 are formed and a substantially semi-cylindrical upper block 15b are integrated.

An arc-shaped wall 51 having seven guide grooves 51a is formed on the upper surface of the upper block 15b.
The above-mentioned light projectors 11 are fitted and positioned one by one in these guide grooves 51a. As shown in FIGS. 2A and 5, each of the projectors 11 has a total of seven distance measurement directions M1 to M7 radially extending at, for example, 15 ° intervals along a virtual plane VS around a virtual viewpoint P. And is arranged so as to emit infrared light (detection light) forward in each of the distance measurement directions M1 to M7. That is, the guide grooves 51 are set so that the optical axis of each projector 11 coincides with the distance measuring directions M1 to M7.
a is formed.

On the other hand, in the lower block 15a, as shown in FIG. 3, five steps of slits 13 are formed along a total of five straight lines radiating from the virtual point Q at intervals of, for example, 6 °. I have.

As shown in FIG. 4, each of the slits 13 is a flat space having a fan-like shape in plan view and extending in the horizontal direction from the back side of the block 15 toward the front side. At the end on the back side of such a slit 13 (that is, at the center of the sector),
The photodetectors 12 are arranged one by one. Each slit 1
The central angle of the fan shape in 3 is set to an angle at which the detection light reflected in front of each of the seven distance measurement directions M1 to M7 can be received.

That is, each of the five photodetectors 12 is provided as a common photoelectric conversion means of the seven projectors 11, and is provided on a plane orthogonal to the virtual plane VS (for example, a vertical plane when the virtual plane VS is a horizontal plane). (Plane), and are arranged in one row away from the virtual plane VS. By making the inclinations of the slits 13 different from each other with respect to the virtual plane VS, the detection light reflected at different positions on the front side in the distance measurement directions M1 to M7 is selectively detected by the photodetector according to the reflection position. 12, the light receiving range of each photodetector 12 is limited.

Next, the principle of distance measurement by the optical system 10 will be described together with the operation of the control system 20. In FIG. 5A, the light projectors 11 are radially arranged around the virtual viewpoint P as described above. FIG. 5A shows three distance measuring directions M1 to M3, but the number of distance measuring directions M1 to M7 in the optical system 10 is 7, and the angle between each of the distance measuring directions is 15 °. Therefore, the target area (field of view) for distance measurement is a fan-shaped two-dimensional space having a central angle of 90 ° (15 ° × 6).

The MPU 21 of the control system 20 sequentially selects one of the seven light projectors 11 one by one, and time-divisions the distance measuring directions M1 to M1.
7 emits the detection light. If there is an object in the distance measuring directions M1 to M7, that is, on the optical axis of the detection light, the detection light is irregularly reflected on the surface of the object and a part of the detection light returns to the photodetector 12 side.

On the other hand, as shown in FIG. 5B, each photodetector 12 is arranged away from a virtual plane (plane including the optical axis of the projector 11) VS, and the light receiving range thereof is limited by the slit 13. ing. Therefore, for example, the detection light reflected at a position within the predetermined range w1 including the point P1 on the optical axis of the light projector 11 enters one light detector 12. Also, a predetermined range w2 including a point P2 farther than the point P1 when viewed from the light projector 11
The detection light reflected at the position inside the other light detector 12
Incident on.

Therefore, the distance between the objects can be determined based on which of the five photodetectors 12 has detected the detection light.
Then, the direction in which the object exists can be determined based on which projector 12 is in the selective light emission state at that time.

The MPU 21 fetches five pieces of detection data corresponding to each photodetector 12 output from the A / D converter 26, calculates the distance between the objects, and uses the result together with data indicating the direction of distance measurement together with the host interface. 27 to the host. This series of processing is repeated at a cycle of, for example, 100 ms. The host recognizes the moving state of the object based on the data input one after another.

If the optical dimensions of each slit 13 are the same, the incident optical axis of each photodetector 12 and the virtual plane VS
Are smaller as the distance from the light projector 11 is greater, the position ranges w1 and w2 corresponding to the respective photodetectors 12 are smaller.
Is wider as the distance from the projector 11 increases. Further, actually, the detection light emitted from the light projector 11 is not a perfect linear beam but spreads as the distance from the light projector 11 increases, so that the amount of light reflected at the point P2 is smaller than the amount of light reflected at the point P1. A difference occurs in the amount of incident light. However, slit 1
By appropriately setting the optical dimensional conditions, the amplification factor of the photoelectric conversion signal, and the like in No. 3, the detection conditions can be easily made uniform regardless of the position.

FIG. 6 is a block diagram showing a functional configuration of the distance measuring apparatus 2 according to the second embodiment. 6, components having the same functions as those in FIGS. 1 to 5 are denoted by the same reference numerals. The same applies to the following figures.

The distance measuring device 2 includes an optical system 10B, a control system 20
B and a microphone 30 as voice detection means, and are used as input means for visual information and auditory information in an object recognition system, for example. The microphone 30 is provided to enhance the practicality of object recognition by determining whether an object approaching the distance measuring device 2 emits a voice like a human.

The optical system 10 B has seven light projectors 11, three light detectors 12, and a lens 14 as an optical means for limiting the light receiving range of each light detector 12. Each projector 11 includes an infrared light emitting diode and a condenser lens. Each photodetector 12 is formed of a phototransistor.

The control system 20B includes an MPU 21B having a function as a means for switching a distance measuring direction, a modulation circuit 22 for blinking a detection light, a driver circuit 23 for supplying a drive current to each projector 11, and a light receiving signal of each photodetector 12. Amplifying circuit 24, a band-pass filter 25 for extracting a modulation component corresponding to the detected light from the amplified received light signal, an A / D converter 26 for quantizing the extracted modulation component, and a microphone 3
An amplifier circuit 31 for amplifying the output of 0 (audio signal), an A / D converter 32 for quantizing the amplified audio signal, and transmitting the measurement result to an external information processing means (host) such as a personal computer. Host interface 27 for the operation.

FIG. 7 is an external view of the optical system 10B of FIG.
8 is a sectional view taken along the arrow VIII of FIG. 7, and FIG. 9 is a sectional view taken along the arrow IX of FIG. FIG. 7A is a plan view of the optical system 10B, and FIG. 7B is a front view of the optical system 10B.

The optical system 10B comprises a substantially semi-cylindrical block 15B whose lower part on the front side is overhanging as a base. An arc-shaped wall portion 51 having seven guide grooves 51a is formed on the upper surface of the block 15B, and the above-mentioned light emitter 11 is fitted into each of the guide grooves 51a and positioned. As shown in FIG.
Is, for example, 15 along the same plane around the virtual viewpoint P.
One is provided for each of a total of seven ranging directions M1 to M7 radially spreading at intervals of °, and is arranged so as to emit infrared light (detection light) toward the front of each of the ranging directions M1 to M7. ing.

As shown in FIG. 9, a space 55 is formed in the lower portion of the block 15B. The space 55 extends in the horizontal direction from the back side to the front side of the block 15B and has a fan shape in plan view. At the rear end (i.e., the center of the fan) of the gap 55, the three photodetectors 12 are arranged in a line in the vertical direction. The central angle of the sector in the gap 55 is set to an angle at which the detection light reflected in front of each of the seven distance measurement directions M1 to M7 can be received. That is, the three photodetectors 12 are orthogonal to the virtual plane VS and in the distance measurement direction M4.
Are arranged apart from the virtual plane VS along the plane including the line segment, and each serves as a common photoelectric conversion unit of the seven light projectors 11.

In the upper part on the front side of the gap 55, the seven lenses 14 are radially arranged on a plane parallel to the virtual plane VS. With these lenses 14,
The detection light reflected at different positions on the front side in the respective distance measurement directions M1 to M7 selectively enters the photodetectors 12 according to the reflection positions, and the light receiving range of each photodetector 12 is limited.

In the distance measuring device 2, similarly to the above-described distance measuring device 1, the MPU 21B of the control system 20B sequentially selects seven projectors 11 one by one and time-divisions the respective distance measuring directions M1 to M1.
7 emits the detection light. If there is an object in the distance measuring directions M1 to M7, that is, on the optical axis of the detection light, the detection light is irregularly reflected on the surface of the object and a part of the detection light returns to the photodetector 12 side.

On the other hand, each photodetector 12 is arranged apart from the virtual plane VS, and the light receiving range thereof is limited by the lens 14. Therefore, for example, the detection light reflected at a point P <b> 4 relatively close to the light projector 11 on the optical axis of the light projector 11 enters the lowermost light detector 12. The detection light reflected at a position farther than the point P4 enters the light detector 12 in the middle stage,
The detection light reflected at a farther position is the uppermost photodetector 1
2 is incident.

Therefore, the distance between the objects can be determined based on which of the three photodetectors 12 has detected the detection light.
Then, the direction in which the object exists can be determined based on which projector 12 is in the selective light emission state at that time.

FIG. 10 is a block diagram showing the functional configuration of the distance measuring apparatus 3 of the third embodiment, and FIG. 11 is a sectional view showing the configuration of the optical system 10C of FIG. The distance measuring device 3 includes an optical system 10C.
And a control system 20C.

The optical system 10C is provided for each of the seven distance measuring directions M1 to M7 extending radially along the virtual plane VS. A position detection type one photodetector (hereinafter referred to as PSD) 12 provided as photoelectric conversion means
0 and a total of seven lenses 14 provided in each of the distance measuring directions M1 to M7 as light receiving range limiting means. The arrangement position of the lens 14 is the same as that of the distance measuring device 2 described above.

The PSD 120 is a relatively large detector having a length of about 6 mm in the detection axis direction of the light receiving surface 120a, and is arranged at the rear end of the gap 55 as shown in FIG. The detection axis direction of PSD 120 is block 15B
In the vertical direction. That is, the PSD 120 outputs a signal corresponding to the incident light amount distribution in a direction along a plane orthogonal to the virtual plane VS.

The control system 20C includes an MPU 21C having a function as a distance measuring direction switching means, a modulation circuit 22 for blinking detection light, a driver circuit 23 for supplying a drive current to each projector 11, and two light receiving signals from the PSD 120. It has an amplification circuit 24C for amplification, an arithmetic circuit 25C for outputting the relative ratio of the two amplified light reception signals as light reception position information, an A / D converter 26C for quantizing the light reception position information, and a host interface 27. I have.

The MPU 21C sequentially selects the seven light projectors 11 one by one, and emits detection light in the respective distance measuring directions M1 to M7 in a time-division manner. If there is an object in the distance measuring directions M1 to M7, the detection light is irregularly reflected on the surface of the object and a part of the light returns to the PSD 120 side.

On the other hand, since the PSDs 120 are arranged at a distance from the virtual plane VS and their light receiving ranges are limited by the lens 14, the light reflected at a point P 4 on the optical axis of the light projector 11 relatively close to the light projector 11 is detected. Light is PSD12
The light is incident on the vicinity of the lower end of the light receiving surface 120a. The detection light reflected at a position farther from the point P4 is incident on a vertically central portion of the light receiving surface 120a, and the detection light reflected at a position farther is incident near the upper end of the light receiving surface 120a.

Therefore, the distance between the objectives can be determined from the position in the light receiving surface where the detection light is incident. Then, the direction in which the object exists can be determined based on which projector 12 is in the selective light emission state at that time. According to the PSD 120, it is possible to perform stepless and highly accurate ranging within a predetermined range.

According to the above-described embodiment, distance measurement in seven directions is
It can be realized by one light transmitter 11 and five light detectors 12, and as in the conventional example, seven distance measuring devices (light transmitter +
The number of the photodetectors 11 can be reduced as compared with the case where the photodetectors are arranged in different directions.
Since the photodetectors 12 are arranged along a plane orthogonal to the virtual plane VS, the size of the optical systems 10 and 10B can be reduced.

Also, when seven light detectors 12 are provided in place of the light projector 11 and five light projectors 11 are provided in place of the light detector 12, distance measurement with the same resolution as in the above-described embodiment is possible. However, according to the above-described embodiment, since the number of components on the light receiving side where signal processing is complicated is smaller than that on the light emitting side, the control system 20
Can be further simplified.

According to the embodiment of FIG.
Since the light receiving range is limited by the slit 13 provided in the optical system 10, the number of components of the optical system 10 is small and the structure is simple compared with the case where special optical components are used, and the cost of the distance measuring device 1 can be reduced. Can be planned.

According to the embodiment of FIGS. 7 and 11,
Since the light receiving range is limited by the lens 14 provided in the block 15B, the optical path can be set relatively freely by the design of the lens 14, so that the size of the block 15B can be reduced compared to the case of the slit 13. It is easy to plan.

According to the embodiment of FIG. 7, the photodetectors 12, 1
Since the microphone 30 is disposed in the gap between the light projector 11 and the photodetectors 12, 120 which is inevitably generated to separate the block 20 from the virtual plane VS, the size of the block 15B due to the attachment of the microphone 30 can be avoided, and the size can be reduced. It is possible to obtain a multifunctional distance measuring device 2 having excellent performance and having a voice detection function.

In the embodiments of FIGS. 1 to 9 described above,
Although it has been described that a discrete component represented by a phototransistor is used as the photodetector 12, an imaging device such as a CCD array in which a large number of light receiving units are integrated is provided as a common photoelectric conversion unit for all the projectors 11, Thereby, the resolution of the distance measurement may be increased. In that case, each light receiving section corresponds to the photodetector of the present invention.

In the above embodiment, the seven light projectors 11
Are converted into photoelectric conversion outputs in the ranging directions M1 to M7.
By making appropriate settings in accordance with the incident angle sensitivity characteristics (directivity) of the photodetector 12 so as not to cause a difference due to the above, distance measurement with higher accuracy can be easily realized.

In the above embodiment, the distance measuring directions M1 to M7
May be in the horizontal direction, the elevation angle direction, or the depression angle direction, and may be optimized according to the positional relationship between the optical systems 10, 10B, and 10C and the object.

In the above embodiment, the distance measuring directions M1 to M7
(Resolution), the number of photodetectors 12, the configurations of the light projector 11 and the photodetector 12, the materials and shapes of the blocks 15, 15B, the configurations of the optical systems 10, 10B, 10C, and the control systems 20, 20B, The circuit configuration of the 20C can be variously changed. For example, the light receiving range may be limited by using a lens having a predetermined shape such as an arc shape. Further, the M light projectors 11 can be arranged in a straight line with different directions, and the N light detectors 12 can be arranged almost parallel to the virtual plane VS.

[0059]

According to the first to third aspects of the present invention,
The measurement of the inter-object distance in the two-dimensional space can be realized with as few parts as possible.

According to the second aspect of the invention, the size of the apparatus can be reduced. According to the third aspect of the invention, the structure can be further simplified. According to the invention of claim 4, the device can be made more compact.

According to the fifth aspect of the invention, it is possible to increase the resolution of the distance measurement without increasing the number of components. According to the invention of claim 6, it is possible to realize the addition of the voice detection function while avoiding an increase in size.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a functional configuration of a distance measuring apparatus according to the present invention.

FIG. 2 is an external view of an optical system of the distance measuring device.

FIG. 3 is a sectional view taken along the arrow III in FIG. 2;

FIG. 4 is a sectional view taken along the arrow IV in FIG. 3;

FIG. 5 is a diagram illustrating the principle of distance measurement by an optical system.

FIG. 6 is a block diagram illustrating a functional configuration of a distance measuring apparatus according to a second embodiment.

FIG. 7 is an external view of the optical system of FIG. 6;

FIG. 8 is a sectional view taken along arrow VIII of FIG. 7;

FIG. 9 is a sectional view taken along the arrow IX in FIG. 8;

FIG. 10 is a block diagram illustrating a functional configuration of a distance measuring apparatus according to a third embodiment.

11 is a cross-sectional view illustrating a configuration of the optical system of FIG.

[Explanation of symbols]

 1, 2, 3 Distance measuring device 11 Projector 12 Photodetector 13 Slit (light receiving range limiting means) 14 Lens (light receiving range limiting means) 21, 21B, 21C MPU (Distance measuring direction switching means) 30 Microphone M1-7 Distance measuring Direction VS Virtual plane 120 PSD (Position detection type photodetector)

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Fumitaka Abe 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-61-272725 (JP, A) JP-A-60-233610 (JP, A) JP-A-6-297365 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01C 3/00 G02B 7/00

Claims (6)

(57) [Claims] 1. One is provided for each of two or more M distance measurement directions radially extending along a virtual plane,
M light emitters that emit detection light forward in each of the distance measurement directions, and at a position distant from the virtual plane , each as common photoelectric conversion means for the M light emitters ,
So that the light receiving range includes all of the M distance measurement directions
Two or more N light detectors arranged , and, in each of the distance measurement directions, the detection lights reflected at different positions on the optical axis of the projector in accordance with their reflection positions. A light receiving range limiting means for making the light incident on the N photodetectors; and a distance measuring direction switching means for selectively emitting the M light emitters one by one sequentially. Distance device. 2. The distance measuring apparatus according to claim 1, wherein said N photodetectors are arranged along a plane orthogonal to said virtual plane. 3. The distance measuring apparatus according to claim 1, wherein an N-stage slit is provided as said light receiving range limiting means. 4. The distance measuring apparatus according to claim 1, wherein said light receiving range limiting means includes M lenses arranged on a plane parallel to said virtual plane. 5. One is provided for each of two or more M ranging directions radially extending along a virtual plane,
M light projectors that emit detection light forward in each of the distance measurement directions; and all of the M distance measurement directions at positions away from the virtual plane as common photoelectric conversion means for the M light projectors.
Are arranged so as to be included in the light receiving range, and a position detection type photodetector that outputs a signal according to an incident light amount distribution in a detection axis direction along a plane orthogonal to the virtual plane, and each of the distance measurement directions A light receiving range limiting means for causing the detection lights reflected at different positions on the optical axis of the light projector to enter different positions in the detection axis direction on a light receiving surface of the light detector; A distance measuring direction switching means for selectively emitting light one by one in order from the distance measuring device. 6. The distance measuring apparatus according to claim 1, wherein a microphone is arranged between said light projector and said photodetector.