JPH07198845A - Distance and image measuring apparatus - Google Patents

Abstract

PURPOSE:To provide a distance and image measuring apparatus which can obtain distance and image information of a long distance target in a short time by using both electronical and mechanical scannings by sequentially making many light sources emit light and scanning at a large angle in one direction at a high speed. CONSTITUTION:A laser diode array 1 has a plurality of laser diodes 11-ln arranged in one dimension. A driver 2 independently sequentially drives the diodes 11-1n so that only any one diode emits light. A mechanically scanning unit 4 scans an optical beam from a lens 3 in a direction perpendicular to an arraying direction of the array 1. A photodetector 7 photoelectrically converts to generate a photodetection signal. A distance and image calculator 8 calculates a distance between an apparatus and a target 10 based on the photodetection signal of a laser pulse, and further calculates a distance and an image from the scanning direction and the calculated distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance / image measuring device, and more particularly to a distance / image measuring device for simultaneously measuring a distance to a target and information as an image of an object.

[0002]

2. Description of the Related Art Conventionally, when measuring a distance to a target using light or the like, a light beam having a sharp directivity is two-dimensionally scanned and applied to a predetermined place for measurement. This 2
Three-dimensional information, that is, distance / image information can be obtained from the dimensional scanning angle and the distance information. The scanning method includes changing the tilt angle of the mirror, rotating the wedge-shaped glass plate, etc. to change the emission direction of the light beam, and passing the light through the material that has been made dense and dense by ultrasonic waves. ,
Conventionally known is an electronic scanning method in which light is diffracted due to this density to be deflected and the deflection angle is electronically controlled.

[0003]

However, the above mechanical scanning method has a problem that the scanning speed is slow although the deflection angle can be made large. On the other hand, the electronic scanning method has an advantage that the scanning speed can be increased, but has a problem that the deflection angle is small. In addition, a semiconductor laser that oscillates at a relatively fast repetition rate and that oscillates in a pulse manner that can obtain a peak power of a strength required for measuring a distance to some extent is conventionally known. The excitation current density and the intensity of the oscillated light at that portion become extremely large, which causes a problem due to local heat generation and the like. Therefore, it has been conventionally difficult to simultaneously achieve high peak power and fast oscillation repetition.

However, in the case of measurement at an extremely short distance, it is possible to obtain a laser oscillation repetition corresponding to a desired scanning speed by lowering the laser output and increasing the oscillation repetition. However, a large peak power is an essential condition for measuring distances above a certain level. Therefore, even if the scanning speed can be resolved, repetition of laser oscillation is limited when three-dimensional information is obtained by measuring a certain distance or more in each scanning direction. Due to the limit of, only a certain amount of data can be obtained per unit time. Therefore, when it is necessary to measure in a short time, the measurement must be performed at coarse intervals. In other words, when it is desired to acquire data with a fine resolution, a large amount of data is required, so the measurement time must be lengthened.

As described above, the conventional measuring apparatus has a limit of scanning speed when the mechanical scanning method is adopted, and has a problem of deflection angle when the electronic scanning method is adopted, and the semiconductor laser is used. When it is used as a light source, the laser output must be decreased when the oscillation repetition is increased, and if the oscillation repetition is limited, the measurement interval becomes coarse or the measurement time becomes long.

The present invention has been made in view of the above points,
By combining electronic scanning and mechanical scanning by sequentially emitting a large number of light sources, high-speed and large-angle scanning in another direction is performed, and the distance / image information of a long-distance target can be obtained in a short time. An object is to provide a distance / image measuring device to be obtained.

[0007]

In order to achieve the above object, the present invention provides a laser diode array in which a plurality of laser diodes are one-dimensionally arranged, and a driver circuit for sequentially driving the plurality of laser diodes one by one. A lens that makes laser light from a laser diode array parallel light, a mechanical scanning device that scans in a direction orthogonal to the arrangement direction of the laser diode array, and a scanning direction recognition circuit that recognizes the scanning direction of the mechanical scanning device. A laser beam emitted from the laser diode and incident on the target through the lens and the mechanical scanning device, and a light receiving unit that receives the reflected light reflected by the target and further incident through the mechanical scanning device to obtain a light reception signal,
A distance / image calculation circuit for calculating the distance to the target based on the light reception signal from the light receiving means, and then calculating image data according to the distance based on the distance and the output signal of the scanning direction recognition circuit, and a distance / image calculation circuit. And a display device for displaying the output image data.

In the present invention, the tilt angle of the device is detected,
It has a tilt angle detection circuit for correcting the image data by the distance / image calculation circuit according to the tilt angle.

[0009]

According to the present invention, since the plurality of laser diodes arranged one-dimensionally are slightly displaced from the optical axis of the lens, when the laser diodes are sequentially driven one by one, the mechanical scanning device is operated. The passed laser light is emitted in different directions little by little, and electronic scanning can be realized. Since the mechanical scanning device scans in the direction orthogonal to the one-dimensional arrangement direction of the laser diode array, the laser light passing through the mechanical scanning device is substantially two-dimensionally scanned.

Further, according to the present invention, since the inclination angle of the device is detected and the distance / image calculating circuit is used to correct the image data, the device is mounted on a vehicle or the like, and the device has unevenness on the road surface. It is possible to obtain an image that does not affect the vertical movement even when the vertical movement is caused by the swell.

[0011]

EXAMPLES Next, examples of the present invention will be described. FIG. 1 shows a block diagram of an embodiment of the present invention. As shown in the figure, the distance / image measuring device of the present embodiment includes a one-dimensional laser diode array 1 and this laser diode array 1.
Driver circuit 2 for sequentially driving the respective elements, a lens 3 for collimating the light beam emitted from the laser diode array 1, and a mechanical scanning device for performing scanning in a direction orthogonal to the arrangement direction of the laser diode array 1. 4, a circuit 5 for recognizing the scanning direction of the mechanical scanning device 4, and a target 10
A light receiving device 6 for receiving the reflected light 11 from the
And the distance to calculate and generate image information from the received light signal
It is composed of an image calculation circuit 8 and a display device 9.

The laser diode array 1 comprises a plurality of laser diodes 1 ₁ to 1 _n arranged one-dimensionally. The driver circuit 2 drives the plurality of laser diodes 1 ₁ to 1 _n independently and sequentially so that only one of them emits light. The mechanical scanning device 4 scans the light beam from the lens 3 in a direction orthogonal to the arrangement direction of the laser diode array 1 by a conventionally known mechanical scanning means.

The light receiving device 6 has a condenser lens, and if necessary, the reflected light transmitted through the condenser lens is made incident on the interference filter through the field stop. The photodetector 7 performs photoelectric conversion to generate a light reception signal. The distance / image calculation circuit 8 uses this device and the target 1 based on the received light signals of the laser pulses emitted from the laser diodes 1 ₁ to 1 _n.
It is configured by a circuit unit that calculates a distance to 0 and further calculates a distance / image from the scanning direction and the calculated distance, and has a structure as shown in FIG. 2, for example. There is.

In FIG. 2, a counter circuit 81, a clock pulse generating circuit 82, a discriminator 83 and a distance calculating section 84 constitute a distance calculating circuit section, and a timing circuit 85, a two-dimensional memory 86 and an image processing section 87. An image calculation circuit unit is configured. Further, the tilt angle detection circuit 88 is provided in the image calculation circuit unit as needed. The counter circuit 81 branches a part of the laser pulse emitted from each of the laser diodes 1 ₁ to 1 _n via the terminal 21 and detects it by a photodetector, or a photodetection signal obtained by the driver circuit 2. A signal obtained by branching the drive signal is applied as a start signal to start counting clock pulses from the clock pulse generation circuit 82.

The discriminator 83 receives the light receiving signal from the photodetector 7 as an input signal via the terminal 22, and outputs a detection pulse when the input signal is above a certain threshold value. The counter 81 stops counting by this detection pulse. The distance calculator 84 calculates the distance from the count value of the counter 81. The timing circuit 85 receives a signal from the driver circuit 2 which indicates which laser diode among the laser diodes 1 ₁ to 1 _n is being driven through the terminal 23, and the scanning direction recognition circuit 5 performs mechanical scanning. A signal indicating a position is input and a signal having a timing corresponding to these input signals is output.

The two-dimensional memory 86 stores the distance data from the distance calculator 84 at an address corresponding to the timing signal from the timing circuit 85. The image processing unit 87 generates image data based on the distance data read from the two-dimensional memory 87. The tilt angle detection circuit 88 detects the tilt angle of this device and outputs the detection signals to the timing circuit 85 and the image processing unit 87, respectively. The display device 9 displays the distance / image which is the output image data of the image processing unit 87.

Next, the operation of this embodiment will be described.
In FIG. 1, a plurality of laser diodes 1 ₁ to 1 _n arranged one-dimensionally are sequentially driven by a driver circuit 2 to sequentially emit pulsed laser light. This laser light is collimated by the lens 3 and is incident on the mechanical scanning device 4. These laser diodes 1 ₁ ~
Since 1 _n is slightly displaced from the optical axis of the lens 3, the laser light after passing through the lens 3 becomes parallel light heading in slightly different directions. For example, the laser light emitted from the laser diode 1 ₁ becomes parallel light indicated by 12 ₁ , and the laser light emitted from the _kth laser diode 1 _k becomes parallel light indicated by 12 _k .

By sequentially driving the plurality of laser diodes 1 ₁ to 1 _n at "time intervals longer than the time required for distance measurement", each laser diode can be utilized without confusion of emitted laser beams. Distance measurements can be made. Considering the entire apparatus, sequentially emitting one laser beam in slightly different directions is the same as causing the emitted laser beam 12 to scan. Therefore, it can be said that this is also a kind of electronic scanning.

Distance information is obtained for each one-dimensional scanning direction. It should be noted that although no scanning for light reception is performed in this scanning direction, one direction of the light receiving surface of the photodetector 7 placed on the focal plane of the light receiving device 6 for receiving the reflected light 11 from the target 10 is lengthened. By doing so, the reflected light from all the electronically scanned directions can be received. Since the photodetector 7 having a wide field of view in the one-dimensional direction has been put to practical use in a one-dimensional scanning distance measuring device using a fan-shaped beam, there is no particular problem. Further, as a matter of course, it is possible to use a photodetector in which a large number of laser diodes are arranged in a one-dimensional direction.

When measuring a distance of 150 m, that is, up to about 1 μs when converted to the round trip time of light, even if the laser emission interval is increased to the same repetition rate of 1 MHz,
There is no danger of confusing the distance measurement between pulses with the return light of another pulse. However, in reality, there is a limit to realizing this with one laser element while maintaining the output above a certain level.

In this embodiment, a large number of laser diodes 1
_{Since 1} to 1 _n share the oscillation respectively, the laser emission interval of each laser diode is 10 kHz.
Repeating about z is sufficient. As a result, in this embodiment, high-repetition high-power oscillation can be performed without causing a thermal problem, and the laser beam can be scanned at high speed.

In this way, the laser diodes 1 ₁ ...
The pulsed laser light sequentially emitted from 1 _n and collimated by the lens 3 is two-dimensionally scanned by the mechanical scanning device 4 at a relatively low speed in the direction orthogonal to the electronic scanning. Is scanned. The light receiving side is also scanned in the same direction as the mechanical scanning direction. That is, the laser beam scanned by the mechanical scanning device 4 is reflected by the target 10 to be reflected light 11, which is incident on the light receiving device 6 through the mechanical scanning device 4 to be received. The reflected light that has passed through the light receiving device 6 is photoelectrically converted into a light reception signal by the photodetector 7, and then input to the discriminator 83 via the terminal 22 of the distance / image calculation circuit 8 shown in FIG.

The discriminator 83 outputs a detection pulse to stop the counting operation of the counter circuit 81 when the received light signal is above a predetermined threshold value. Counter circuit 8
1, a start signal synchronized with each light emission timing of the laser diodes 1 ₁ to 1 _n is input via the terminal 21, and at the time of inputting this start signal, counting of clock pulses of a constant cycle from the clock pulse generation circuit 82 is started.

Therefore, the counter circuit 82 outputs a pulse laser beam emitted from a certain laser diode as shown by a1 in FIG.
Until the time when the reflected light shown by 2 is detected by the photodetector 7, the clock pulses shown in FIG. 7B are counted, and the counted value shows a value corresponding to the round-trip time t of the laser light. . The distance calculation unit 84 obtains the round-trip time t of the laser light based on this count value, and then adds {((speed of light)) to the round-trip time t.
The distance from the device to the target 10 is calculated by multiplying by 1/2.

In this way, the distance data calculated based on the round-trip time of each laser beam of each laser diode 1 ₁ to 1 _n is supplied to the two-dimensional memory 86,
Mechanical scanning device 4 detected by scanning direction recognition circuit 5
It is written by the timing pulse from the timing circuit 85 based on the scanning position of. This two-dimensional memory 86
Is basically a laser diode 1 ₁ to 1 _{n in the} vertical direction, for example.
1 to 1, each of which has a two-dimensional memory area corresponding to the scanning angle of the mechanical scanning device 4 in the lateral direction, and each distance data is stored in each memory area.

The distance data read from the two-dimensional memory 86 is subjected to image processing by the image processing section 87 and then output to the display device 9 for display. As the image processing by the image processing unit 87, hues assigned to each certain distance range (for example, 90 to 95 m are red, 95 to 100 m are orange,
Method of displaying each pixel, such as 100 to 105 m is yellow,
In addition, there is a method of connecting pixels that show the same distance, such as contour lines, by connecting them with a line, and a method of displaying only the areas where the distance difference is a predetermined distance or more and connecting them with a line and displaying the contour. is there. Which of these image processing methods is adopted can be arbitrarily determined.

The distance data may be output to a computer or the like as needed. Further, when specifically implemented, it is difficult to temporally control the scanning of the mechanical scanning device 4, so the scanning direction of the mechanical scanning device 4 which scans at a constant period is detected, A method such as controlling electronic scanning based on the information is required.

When this embodiment is mounted on a vehicle or the like and is measured while traveling, it is possible that the entire apparatus may be tilted due to vertical movement depending on the shape of the ground. In that case, the tilt angle is detected by the tilt angle detection circuit 88, and the light emitting position of the laser diode array 1 is controlled by this tilt angle detection information or the storage address of the two-dimensional memory 86 for storing the distance information is changed. , 3D information for the target 10 can be obtained without being affected even if the apparatus tilts during scanning.

FIG. 4 is a diagram showing an image of an image connecting points at which the difference between the scanning direction, the type of scanning, and the distance changes abruptly, that is, a point corresponding to the target edge. Goal 1
Assuming that 0 is a square object located at a certain distance, an image of the object is displayed on the display screen 91 of the display device 9 when the device is stable, for example, as shown in FIG. It is displayed as indicated by 31. The distances to the points inside the line 32 indicating the edge of the image 31 are almost equal, but the distances outside the line 32 vary greatly, and in some cases, the distances become too long to be measured.

Here, when the vehicle mounted with the apparatus of this embodiment is tilted by the vertical movement and the emission direction of the scanning laser light is changed, the above-mentioned image 31 is, for example, as shown by 33 in FIG. 4 (B). , The edge 34 looks distorted. Therefore, in this embodiment, based on the tilt angle detection information of the tilt angle detection circuit 88,
Image correction processing is performed by one of the following methods. In the first correction method, the light emission timing of the laser diode array 1 is kept as it is and the time timing of storing in the two-dimensional memory 86 is shifted to
When the device is facing upward by an angle corresponding to the number of units, the distance data measured by the laser diode 1 ₂ is stored in the address where the distance data measured by the laser diode 1 ₁ is originally stored. The stored distance data are stored in the addresses shifted one by one. And the two-dimensional memory 86
Is read as usual.

In the second correction method, the timing of storing the distance data in the two-dimensional memory 86 is fixed, and the light emission timing of each of the laser diodes 1 ₁ to 1 _n of the laser diode array 1 is shifted to, for example, the laser diode 1 _1. The address at which the distance data measured by the laser diode 1 ₁ is originally stored, while the distance data measured by the laser diode 1 ₂ or 1 ₃ is emitted slightly before the time when the distance data originally measured is stored. To store. And 2
The dimensional memory 86 is read out as usual.

In the third correction method, the light emission timing of the laser diode array 1 and the timing of storing the distance data in the two-dimensional memory 86 are respectively set as usual with the inclination angle being zero, and the output inclination angle of the inclination angle detection circuit 88 is determined. The readout control of the image processing unit 87 is performed based on the detection data.

By such an image correction process, the image on the screen 91 of the display device 9 can be made to have a straight line 36 at the edge, as shown at 35 in FIG. 4C. However, this correction processing discards the image portion 37 indicated by diagonal lines,
Since it is not displayed, it is not possible to display all the images in the scanned area, but in actuality, in most areas, the distance / image information is obtained by correcting the tilt of the device due to vertical movement of the vehicle etc. Can be obtained. Further, when the vertical movement is caused to extend beyond the screen, it is possible to ensure the continuity of measurement by not displaying the data for one screen.

As described above, according to the present embodiment, since electronic scanning and mechanical scanning are used in combination, a target at a relatively long distance can be obtained as in the case of high-repetition high-power laser scanning at high speed. On the other hand, it is possible to obtain the distance / image information with a fine resolution and in a short time. Laser diode array 1
Since the electronic scanning is performed by using, the repetition of oscillation of each laser diode is limited, but the entire apparatus can perform the same high-speed scanning as when the laser diode oscillates as fast as the number of laser diodes. In addition, since the mechanical scanning device 4 scans in a direction that may be delayed, the cost can be reduced and the scanning range can be increased.

The present invention is not limited to the above-described embodiment. For example, as shown in FIG. 4A, the electronic scanning direction is the vertical direction (vertical direction) of the screen and the mechanical scanning direction is the screen. However, the electronic scanning direction may be the horizontal direction of the screen and the mechanical scanning direction may be the vertical direction of the screen. However, since the mechanical scanning direction can have a large scanning angle, it is actually desirable to set the lateral direction of the screen as the mechanical scanning direction.

Further, when the present invention is used for detecting an obstacle to an object traveling on the ground, it is not necessary to scan a large amount in the up and down direction, but if a sudden protrusion is assumed in the left and right direction, the scanning range is changed to cope with the problem. Since there is also a need to do so, there is also an advantage that the degree of freedom is increased when the left and right direction is the mechanical scanning direction.

[0037]

As described above, according to the present invention,
Since the electronic scanning and the mechanical scanning are combined to perform two-dimensional scanning, similar to the high-repetition high-power laser scanning at high speed, with a fine resolution for a target at a relatively long distance, and The distance / image information can be obtained in a short time. Further, according to the present invention, by detecting the tilt angle of the device and electronically correcting the distance and the image, it is possible to always display an image that is easy to see without being affected by the vertical movement of the device. As in the case of detecting the speed and the like, it is possible to easily recognize whether or not they are the same object.

Furthermore, when electronic scanning is performed in both directions, the photodetector must be two-dimensionally large,
In addition to the problem in terms of hardware, it causes an increase in background noise, etc., but since the present invention is electronic scanning in only one direction, a photodetector for a fan beam that has already been put into practical use can be applied, Background noise can be reduced.

[Brief description of drawings]

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

FIG. 2 is a block diagram of an example of a distance / image calculation circuit in FIG.

FIG. 3 is a time chart for explaining an operation of a main part of FIG.

FIG. 4 is a diagram for explaining the directions of electrical scanning and mechanical scanning in FIG. 1 and correction of a display image.

[Explanation of symbols]

1 laser diode array 1 ₁ to 1 _n laser diode 2 driver circuit 3 lens 4 mechanical scanning device 5 scanning direction recognition circuit 6 light receiving device 7 photodetector 8 distance / image calculation circuit 9 display device 10 target 81 counter circuit 84 distance calculation Unit 86 Two-dimensional memory 87 Image processing unit 88 Tilt angle detection circuit

Claims (4)

[Claims] 1. A laser diode array in which a plurality of laser diodes are one-dimensionally arranged, a driver circuit for sequentially driving the plurality of laser diodes forming the laser diode array one by one, and a laser beam from the laser diode array. A lens for making parallel light, a mechanical scanning device for scanning in a direction orthogonal to the array direction of the laser diode array, a scanning direction recognition circuit for recognizing the scanning direction of the mechanical scanning device, and the laser diode Laser light emitted and incident on a target through the lens and the mechanical scanning device receives reflected light reflected by the target and incident on the mechanical scanning device to obtain a light reception signal; After calculating the distance to the target based on the light receiving signal from the light receiving means, the distance and the output signal of the scanning direction recognition circuit are used to calculate the distance. A distance / image measuring device, comprising: a distance / image calculating circuit for calculating image data according to the distance; and a display device for displaying output image data of the distance / image calculating circuit. 2. The distance / image calculation circuit includes means for detecting a propagation time of laser light from the laser diode, a distance calculation section for calculating a distance based on the propagation time, and distance data indicating the distance. 2. A two-dimensional memory for storing the data according to the output of the scanning direction recognition circuit, and an image processing unit for processing the output data of the two-dimensional memory to generate image data. Distance and image measuring device. 3. A correction process of image data by detecting a tilt angle of a device and controlling a write timing of the two-dimensional memory in the distance / image calculation circuit or an output timing of the image processing unit according to the tilt angle. The distance according to claim 2, further comprising a tilt angle detection circuit for performing
Image measuring device. 4. The arrangement direction of the laser diode array is a screen vertical direction of a display device that displays an image based on the image data, and the scanning direction of the mechanical scanning device is a screen horizontal direction of the display device. The distance / image measuring device according to any one of claims 1 to 3.