JP3651412B2 - Distance measuring device and distance measuring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a distance measuring apparatus and a distance measuring method for measuring a distance to a target, and more particularly to a distance measuring apparatus and a distance measuring method for measuring a distance to a target using a laser pulse and a two-dimensional array light receiving element.
[0002]
[Prior art]
FIG. 3 is an explanatory diagram illustrating an example of an operation image of distance measurement, and FIG. 4 is a block diagram illustrating a configuration of a conventional distance measurement apparatus.
[0003]
FIG. 3 (a) shows a scene in which a car is traveling between trees (obstacles), and when trying to drive the car automatically in such a place, as shown in FIG. 3 (b). It is necessary to three-dimensionally understand the state of trees (obstacles) ahead of the car based on the field of view from the vehicle. FIG.3 (c) shows the condition which looked at the tree (obstacle) from the top.
[0004]
At present, as a method of three-dimensionally grasping the state of an obstacle in front of an automobile, a method using a pencil beam and a two-dimensional scanning optical system, and a linear measurement range using a fan beam and a one-dimensional array light receiving element are one-dimensional. A method of scanning using a scanning optical system and a method of using a laser pulse and a two-dimensional array light receiving element are conceivable. In the future, in order to shorten one frame measurement time, a laser pulse and a two-dimensional array light reception are performed. It is expected that a method using an element is generally used.
[0005]
A method using a laser pulse and a two-dimensional array light-receiving element such as a detector array with a distance measuring function (light-receiving elements arranged in a two-dimensional array) emits a single laser pulse forward and receives the two-dimensional array. By receiving the reflected light from the obstacle (target) by the element, the front three-dimensional obstacle situation can be measured instantaneously.
[0006]
As shown in FIG. 4, a distance measuring apparatus using a conventional method using a laser pulse and a two-dimensional array light-receiving element transmits a laser pulse transmitted from a laser oscillation unit 1 through a light-emitting optical system 3 by a half mirror 2. The laser beam is separated into the emitted laser beam to be emitted and the start timing detection laser pulse, and the timing at which the separated start timing detection laser pulse is received by the photodetector 4 is input to the detector array 5 with distance measuring function as the start timing T0. One element of the detector array 5 with a distance measuring function includes a photo detector 7, a preamplifier 8, a determination circuit 9, and a time measurement circuit 10, and a start timing T 0 is input to the time measurement circuit 10.
[0007]
The emitted laser beam is reflected by the target obstacle, is incident on the detector array 5 with a distance measuring function via the light receiving optical system 6 as reflected light from the target, and is reflected from the target by the determination circuit 9 for each element. The light reception timing is determined as the stop timing and input to the time measurement circuit 10.
[0008]
The time measuring circuit 10 measures the time from the start timing T0 (the timing at which the laser pulse for detecting the start timing is received by the light detector 4) to the stop timing (the timing at which the reflected light from the target is received), and from the start timing T0 to the stop timing. The distance to the target can be measured based on the time measurement up to.
[0009]
For example, when the distance measurement resolution is 0.05 and the time measurement is performed digitally using a 3 GHz clock pulse, an 18-bit counter is required for 10 km measurement.
[0010]
[Problems to be solved by the invention]
However, in the prior art, when the detector array with distance measuring function is integrated into LSI for the purpose of downsizing the distance measuring device, the time measuring circuit is large, so there is a limit to downsizing one element. There was a problem that it was impossible to increase the resolution of the detector array with functions.
[0011]
The present invention has been made in view of such problems, and an object of the present invention is to reduce the time measurement circuit scale of the detector array with a distance measuring function, and to make one element of the detector array with a distance measuring function smaller. The object is to provide a distance measuring apparatus and a distance measuring method that can be configured with an area and can increase the resolution of a detector array with a distance measuring function even when the detector array with a distance measuring function is implemented as an LSI.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration.
The gist of the invention described in claim 1 is that the laser pulse is emitted from the laser generating means, the laser pulse reflected by the obstacle is received by each light receiving element of the two-dimensional array light receiving element, and the distance to the obstacle A three-dimensional measurement apparatus for measuring the first pulse detection time for measuring the time from when the laser pulse is emitted until the first arrival at the two-dimensional array light-receiving element as the first pulse time. Measuring means and time measuring means for measuring a time difference in the light receiving timing of the laser pulse between the light receiving elements of the two-dimensional array light receiving element, and summing signals from the light receiving elements of the two-dimensional array light receiving element provided the sum computing means for computing said first pulse detection time measuring means, distance, characterized in that to measure the first pulse time on the basis of a signal from the OR operation means It resides in the constant apparatus.
According to a second aspect of the invention, there is provided delay means for delaying the light receiving timing for each light receiving element of the two-dimensional array light receiving element, and the time measuring means is the light receiving timing delayed by the delay means. The distance measurement apparatus according to claim 1, wherein the time difference is measured.
According to a third aspect of the present invention, there is provided a half mirror disposed on an optical path leading to the two-dimensional array light receiving element, and a photodetector for receiving the laser pulse separated by the half mirror, 3. The distance measuring device according to claim 1, wherein the one-pulse detection time measuring unit measures the first pulse time based on a signal from the photodetector.
According to a fourth aspect of the present invention, a laser pulse is emitted from a laser generating means, and the laser pulse reflected by the obstacle is received by each light receiving element of the two-dimensional array light receiving element to reach the obstacle. A distance measuring method for measuring a distance three-dimensionally, measuring a time from when the laser pulse is emitted to first reaching the two-dimensional array light receiving element as a first pulse time, and the two-dimensional array A time difference between the light receiving timings of the laser pulses between the light receiving elements of the light receiving elements is measured, a signal from each light receiving element of the two-dimensional array light receiving element is summed, and the first pulse is calculated based on the sum-calculated signal. It exists in the distance measuring method characterized by measuring time .
The gist of the invention described in claim 5 is that the light receiving timing of each light receiving element of the two-dimensional array light receiving element is delayed and the time difference between the delayed light receiving timings is measured. It exists in the distance measurement method.
The gist of the invention described in claim 6 is that the laser pulse is separated by a half mirror disposed on an optical path leading to the two-dimensional array light receiving element, the separated laser pulse is received by a photodetector, and from the photodetector. 6. The distance measuring method according to claim 4, wherein the first pulse time is measured based on a signal.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0014]
(First embodiment)
FIG. 1 is a block diagram showing a configuration of a first embodiment of a distance measuring apparatus according to the present invention.
[0015]
In the present embodiment, a laser oscillation unit 1 that transmits a laser pulse, a half mirror 2 that separates a part of the laser pulse transmitted from the laser oscillation unit 1 as a laser pulse for detecting start timing, and a transmission from the laser oscillation unit 1 A light emitting optical system 3 for emitting the emitted laser pulse as an outgoing laser beam, a light detector 4 for detecting the light receiving timing of the start timing detecting laser pulse separated by the half mirror 2, and a two-dimensional array light receiving element. A detector array 5 with a distance measuring function, a light receiving optical system 6 for guiding reflected light from the target to the detector array 5 with distance measuring function, and a first pulse detection for separating the reflected light from the target as a first pulse detecting laser pulse. Laser mirror for separation of the first pulse and the laser pulse for first pulse separation separated by the first pulse detection half mirror. Consisting of a first pulse detector 20 for detecting the pulses received by the very beginning of the scan.
[0016]
One element of the detector array 5 with a ranging function receives a reflected light from a target and converts it into an electrical signal, a preamplifier 8 for amplifying the electrical signal from the photodetector 7, and a preamplifier 8. A delay line 11 for delaying the received electric signal, a determination circuit 9 for determining the light reception timing based on the electric signal delayed by the delay line 11, and a time measurement circuit 10 for measuring a time difference between the elements of the light reception timing. Become.
[0017]
The first pulse detection unit 20 receives the reflected light from the target separated by the first pulse detection half mirror 12 and converts it into an electric signal, and the first pulse detection photo detector 21. The first pulse detection preamplifier 22 that amplifies the electric signal converted by the above and the light reception timing of the first pulse received from the reflected light from the target based on the electric signal amplified by the first pulse detection preamplifier 22 First pulse detection determination circuit 23 for determining the first pulse detection time, and the first pulse detection time measurement for measuring the time until the light reception timing of the first light reception pulse based on the determination result of the first pulse detection determination circuit 23 Circuit 24. The optical path from the first pulse detecting half mirror 12 to the first pulse detecting photo detector 21 and the optical path from the first pulse detecting half mirror 12 to the detector array 5 with distance measuring function have the same length. Is set.
[0018]
A specific circuit of the time measuring circuit 10 and the first pulse detecting time measuring circuit 24 may be a digital counter, and an analog time for converting the charging time to the capacitor voltage level by using the charge accumulation in the capacitor. It may be a measurement type circuit.
[0019]
Next, the operation of the first embodiment will be described in detail.
[0020]
The laser pulse transmitted from the laser oscillation unit 1 is separated into an outgoing laser beam emitted from the half mirror 2 via the light-emitting optical system 3 and a start timing detection laser pulse, and the photodetector 4 is used to detect the separated start timing. The light reception timing is detected by receiving the laser pulse, and the detected light reception timing is input to the first pulse detection time measuring circuit 24 of the first pulse detection unit 20 as the start timing T0.
[0021]
The outgoing laser beam emitted through the light emitting optical system 3 is reflected by the target and reaches the light receiving optical system 6 as reflected light from the target. The reflected light from the target that has passed through the light receiving optical system 6 is separated into the reflected light from the target received by the detector array with distance measuring function 5 by the first pulse detecting half mirror 12 and the first pulse detecting laser pulse. To do.
[0022]
The first pulse detection photodetector 21 receives the first pulse detection laser pulse separated by the first pulse detection half mirror 12 and converts it into an electrical signal, and the first pulse detection preamplifier 22 The electrical signal converted by the detection photodetector 21 is amplified, and the first pulse detection determination circuit 23 reflects the reflected light from the target (first pulse detection) based on the electrical signal amplified by the first pulse detection preamplifier 22. Light receiving timing of the first light receiving pulse is determined, and the determined light receiving timing is input to the first pulse detection time measuring circuit 24 and the time measuring circuit 10 as the first pulse light receiving timing T1. To do. Note that the first pulse detection photo-detector 21 uses the entire measurement area as a light receiving field.
[0023]
The first pulse detection time measuring circuit 24 starts from the start timing T0 based on the start timing T0 input from the photodetector 4 and the first pulse light reception timing T1 input from the first pulse detection determination circuit 23. The time until the 1-pulse light receiving timing T1 is measured. By obtaining the distance to the obstacle (target) from the time measurement result by the first pulse detection time measuring circuit 24, the distance to the nearest obstacle (target) can be measured.
[0024]
The detector array with distance measuring function 5 receives the reflected light from the target for each element. The photodetector 7 of each element receives reflected light from the target and converts it into an electrical signal, the preamplifier 8 amplifies the electrical signal from the photodetector 7, and the delay line 11 outputs the electrical signal amplified by the preamplifier 8. The determination circuit 9 delays the light reception timing based on the electrical signal delayed by the delay line 11 and inputs it to the time measurement circuit 10 as the stop timing.
[0025]
The time measurement circuit 10 measures the time difference between the elements based on the first pulse light reception timing T1 input from the first pulse detection determination circuit 23 and the stop timing input from the determination circuit 9. The distance between the obstacles (targets) can be measured by obtaining the distance between the obstacles (targets) in consideration of the delay time of the electric signal by the delay line 11 from the measurement result of the time difference by the time measuring circuit 10. .
[0026]
Note that the delay of the electric signal by the delay line 11 is performed because it is necessary to input the delay time to the time measurement circuit 10 so that the stop timing can be measured with respect to the first pulse light reception timing T1.
[0027]
In the case of obstacle (target) measurement, it is not necessary for all the elements of the detector array with distance measuring function 5 to measure the distance to the obstacle (target), and one reference distance and one point are used as reference points. As long as the relative distance of a certain distance range can be measured, the obstacle (target) can be grasped. When the size of the obstacle (target) is several meters to several tens of meters, it is sufficient to measure in the range of about 100 meters. To measure the relative distance of 100 meters, 11 bits are sufficient for the counter, and When measuring a distance obstacle (target), the scale of the time measuring circuit 10 of the detector array with distance measuring function 5 can be reduced to a fraction of that when the relative distance is not measured.
[0028]
As described above, according to the first embodiment, the time difference between the elements of the detector array with distance measuring function 5 is obtained based on the first pulse light receiving timing T1 received first, and the obstacle ( In order to measure the relative distance of the target), it is not necessary to measure the distance to the target for all the elements of the detector array 5 with the distance measuring function, and the scale of the time measuring circuit 10 of the detector array 5 with the distance measuring function can be reduced. One element of the detector array with distance measuring function 5 can be configured with a smaller area, and even when the detector array with distance measuring function 5 is implemented as an LSI, the resolution of the detector array 5 with distance measuring function can be increased. There is an effect.
[0029]
(Second Embodiment)
FIG. 2 is a block diagram showing the configuration of the second embodiment of the distance measuring apparatus according to the present invention.
[0030]
In the first embodiment, the first pulse detection timing T1 is determined by the first pulse detection determination circuit 23 by separating the reflected light from the target by the first pulse detection half mirror 12. In the second embodiment, as shown in FIG. 2, the sum of the outputs of the preamplifiers 8 ₁ to 8 _n of each element of the detector array 5 with distance measuring function is taken by the sum arithmetic circuit 25. The first pulse detection timing T1 is determined by the first pulse detection determination circuit 23 based on the output.
[0031]
The photodetectors 7 _{1 to} 7 _n of the respective elements of the detector array with distance measuring function 5 receive the reflected light from the target and convert them into electric signals, and the preamplifiers 8 ₁ to 8 _n are connected to the photodetectors 7 _{1 to} 7 _n. Are respectively amplified and output to the delay lines 11 _{1 to} 11 _n and also output to the sum calculation circuit 25.
[0032]
The sum calculation circuit 25 calculates the sum of the outputs of the preamplifiers 8 ₁ to 8 _n , and the first pulse detection determination circuit 23 determines the first pulse light reception timing T 1 based on the output from the sum calculation circuit 25 and determines the first pulse reception timing T 1. This is input to the time measuring circuit 24 for detecting one pulse and the time measuring circuits 10 ₁ to 10 _n .
[0033]
The delay lines 11 _{1 to} 11 _n delay the electric signals amplified by the preamplifiers 8 ₁ to 8 _n , respectively. The determination circuits 9 _{1 to} 9 _n are based on the electric signals delayed by the delay lines 11 _{1 to} 11 _n. Then, the light receiving timing is determined and inputted to the time measuring circuits 10 ₁ to 10 _n as stop timing.
[0034]
Note that the present invention is not limited to the above-described embodiments, and it is obvious that the embodiments can be appropriately changed within the scope of the technical idea of the present invention. In addition, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiment, and can be set to a number, position, shape, and the like that are suitable for implementing the present invention. In each figure, the same numerals are given to the same component.
[0035]
【The invention's effect】
The distance measuring apparatus and distance measuring method of the present invention obtains the relative distance of an obstacle (target) by obtaining the time difference between each element of the detector array with a distance measuring function based on the first pulse light receiving timing received first. For the measurement, it is not necessary to measure the distance to the target for all the elements of the detector array with a distance measuring function, and the scale of the time measuring circuit of the detector array with the distance measuring function can be reduced. The element can be configured with a smaller area, and even when the detector array with a distance measuring function is implemented as an LSI, it is possible to increase the resolution of the detector array with a distance measuring function.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of a distance measuring device according to the present invention.
FIG. 2 is a block diagram showing a configuration of a second embodiment of a distance measuring device according to the present invention.
FIG. 3 is an explanatory diagram illustrating an example of an operation image of distance measurement.
FIG. 4 is a block diagram showing a configuration of a conventional distance measuring device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser oscillation part 2 Half mirror 3 Light emission optical system 4 Photo detector 5 Detector array with a ranging function 6 Light reception optical system 7 Photo detector (photodetector)
8 Preamplifier 9 Determination Circuit 10 Time Measurement Circuit 11 Delay Line 12 First Pulse Detection Half Mirror 20 First Pulse Detection Unit 21 First Pulse Detection Photodetector 22 First Pulse Detection Preamplifier 23 First Pulse Detection Determination Circuit 24 1 pulse detection time measurement circuit 25 Sum calculation circuit

Claims (6)

A distance measuring device that emits a laser pulse from a laser generating means, receives the laser pulse reflected by an obstacle for each light receiving element of a two-dimensional array light receiving element, and measures the distance to the obstacle three-dimensionally Because
First pulse detection time measuring means for measuring a time from when the laser pulse is emitted until the first arrival at the two-dimensional array light-receiving element as a first pulse time;
A time measuring means for measuring a time difference in light receiving timing of the laser pulse between the light receiving elements of the two-dimensional array light receiving element ,
Comprising sum calculating means for calculating the sum of signals from each light receiving element of the two-dimensional array light receiving element;
The first pulse detection time measuring means causes the first pulse time to be measured based on a signal from the sum calculating means . Delay means for delaying the light receiving timing for each light receiving element of the two-dimensional array light receiving element,
The distance measuring device according to claim 1, wherein the time measuring unit measures a time difference of the light reception timing delayed by the delay unit. A half mirror disposed on an optical path leading to the two-dimensional array light receiving element;
A photodetector for receiving the laser pulse separated by the half mirror,
The distance measuring device according to claim 1, wherein the first pulse detection time measuring unit measures the first pulse time based on a signal from the photodetector. A distance measuring method for emitting a laser pulse from a laser generating means and receiving the laser pulse reflected by an obstacle for each light receiving element of a two-dimensional array light receiving element and measuring a distance to the obstacle three-dimensionally Because
The time from when the laser pulse is emitted until it first reaches the two-dimensional array light receiving element is measured as the first pulse time,
Measuring the time difference of the light receiving timing of the laser pulse between the light receiving elements of the two-dimensional array light receiving element;
The signal from each light receiving element of the two-dimensional array light receiving element is summed,
A distance measuring method comprising measuring the first pulse time based on the sum-calculated signal . Delaying the light receiving timing for each light receiving element of the two-dimensional array light receiving element;
5. The distance measuring method according to claim 4, wherein a time difference of the delayed light reception timing is measured. The laser pulse is separated by a half mirror disposed on the optical path leading to the two-dimensional array light receiving element,
The separated laser pulse is received by a photodetector,
6. The distance measuring method according to claim 4, wherein the first pulse time is measured based on a signal from the photodetector .

Images