CN107272011B - Time point identification method, time point identification circuit system and laser ranging system - Google Patents
Time point identification method, time point identification circuit system and laser ranging system Download PDFInfo
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- CN107272011B CN107272011B CN201710403347.4A CN201710403347A CN107272011B CN 107272011 B CN107272011 B CN 107272011B CN 201710403347 A CN201710403347 A CN 201710403347A CN 107272011 B CN107272011 B CN 107272011B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
Abstract
The invention relates to a time point identification method, a time point identification system and a laser ranging system, which are characterized in that echo pulses obtained by detection during measurement are divided into two paths; one path is subjected to peak value holding processing, the peak value holding processing is used for converting the echo pulse into a direct current level, the voltage value of the direct current level is the peak voltage of the echo pulse, and the direct current level is attenuated in a set proportion; the other path is subjected to delay processing, the delay processing is used for carrying out nanosecond-level delay on the echo pulse, and the delay quantity is ensured to be larger than the time delay caused by peak value holding and attenuation; and comparing the voltage values of the attenuated direct current level and the delayed echo pulse, and taking the time when the voltage value comparison result changes as the arrival time of the echo pulse, wherein when the amplitude of the echo pulse changes, the voltage value of the time point identification level also changes, so that the time point identification independent of the echo intensity is realized. The invention is widely applied to pulse laser ranging systems or ranging of two-dimensional or three-dimensional laser radar systems based on different beam scanning modes.
Description
Technical Field
The invention relates to a time point identification method, a time point identification circuit system and a laser ranging system for a pulse type laser ranging system or a two-dimensional or three-dimensional laser radar system based on different light beam scanning modes, and belongs to the technical field of laser distance measurement.
Background
The pulse type three-dimensional laser radar based on the flight time method has the characteristics of long measuring distance, high frequency, low power consumption and the like due to the adoption of the pulse type laser as a light source, and is widely applied to the fields of three-dimensional modeling, environmental perception and the like. The time difference delta T between the laser pulse transmitting time and the diffuse reflection echo pulse receiving time is recorded by the pulse type three-dimensional laser radar of the flight time method, and the round-trip distance between the laser radar and the measured object can be calculated by multiplying the time difference delta T by the light speed C. The three-dimensional shape information of the measured object can be obtained by scanning beams in the pitching direction and the horizontal direction.
An important factor influencing the distance measurement accuracy in the prior art is the measurement accuracy of the time difference Δ T between the laser pulse emission time and the echo reception time. According to a time-of-flight ranging formula:
wherein L is the measured distance and C is the speed of light. As can be calculated from the above equation, a timing error of 1ns will introduce a ranging error of 15 cm. The amplitude of the echo pulse changes greatly after the emitted laser pulse is subjected to diffuse reflection by objects with different reflectivities. For a pulse type laser radar with a laser pulse width of 5-10 nanoseconds, nanosecond time measurement errors, namely distance measurement errors of dozens of centimeters, can be caused when the arrival time of an echo pulse is judged through a constant level, and the application range and the measurement precision of the three-dimensional laser radar are seriously influenced.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a time point identification method, a time point identification circuit system, and a laser ranging system, which can improve the accuracy of laser radar distance measurement.
In order to achieve the purpose, the invention adopts the following technical scheme: a time point identification method is characterized by comprising the following steps: dividing echo pulses obtained by detection in measurement into two paths; one path is subjected to peak value holding processing, the peak value holding processing is used for converting the echo pulse into a direct current level, the voltage value of the direct current level is the peak voltage of the echo pulse, and the direct current level is attenuated in a set proportion; the other path is subjected to delay processing, the delay processing is used for carrying out nanosecond-level delay on the echo pulse, and the delay quantity is ensured to be larger than the time delay caused by peak value holding and attenuation; and comparing the voltage values of the attenuated direct current level and the delayed echo pulse, and taking the time when the voltage value comparison result changes as the arrival time of the echo pulse, wherein when the amplitude of the echo pulse changes, the voltage value of the time point identification level also changes, so that the time point identification independent of the echo intensity is realized.
In order to achieve the purpose, the invention adopts the following technical scheme: timing discrimination circuitry comprising a peak holder, an attenuator, a delay, and a comparator; the peak value keeper is used for keeping the peak value of the echo pulse to be a direct current level and sending the peak value to the attenuator, the attenuator is used for attenuating the direct current level in a set proportion, the delayer is used for delaying the echo pulse in a nanosecond level, and output signals of the attenuator and the delayer are sent to the comparator to be compared and processed to obtain the arrival time of the echo pulse.
In order to achieve the purpose, the invention adopts the following technical scheme: a laser ranging system is characterized by comprising a main controller, a pulse laser, a first detector, a second detector, a first amplifier, a second amplifier, a first comparator, a timing circuit and a time point identification circuit system, wherein the main controller is connected with the pulse laser; the main controller controls the pulse type laser to emit detection pulses, and the laser pulses emitted by the pulse type laser are divided into two paths of light; one path of light is emitted to the first detector, the first detector carries out photoelectric conversion on an optical signal and then sends the optical signal to the first amplifier, the first amplifier and a constant level signal are respectively connected with two input ends of the first comparator, and the output end of the first comparator is connected with the timing circuit to serve as a timing starting signal; the other path of light is emitted to a measured object as a detection pulse, a signal diffusely reflected by the measured object is emitted to the second detector, the second detector carries out photoelectric conversion on the light signal and then emits the light signal to the second amplifier, the signal output by the second amplifier is respectively sent to the peak value retainer and the delayer, the signal output by the comparator is sent to the timing circuit as a timing end signal as a trigger signal, and the timing circuit records a time difference between a timing start signal and the timing end signal and sends the time difference to the main controller.
Due to the adoption of the technical scheme, the invention has the following advantages: 1. the invention can finish the generation of the timer stop trigger signal in a single echo by using a time point identification method independent of the echo pulse intensity, and the detection efficiency of the laser radar can not be reduced. 2. The invention uses peak value holding instead of a digital-to-analog converter to obtain the peak value of the echo pulse, saves the digital-to-analog conversion time, reduces the cost of the system and has great significance in the application of high-speed laser radars. 3. The invention ensures that the timing point of the arrival time of the echo pulse of the object with different reflectivities detected by the laser radar does not depend on the echo intensity, improves the distance measurement precision of the three-dimensional laser radar and enhances the adaptability of the three-dimensional laser radar to the targets with different surface reflectivities. The invention can be widely applied to pulse laser ranging systems or ranging of two-dimensional or three-dimensional laser radar systems based on different beam scanning modes.
Drawings
FIG. 1 is a schematic diagram of the time point identification method independent of echo intensity according to the present invention;
FIG. 2 is a method of time point identification of the present invention;
fig. 3 is a laser ranging system based on a time point identification method according to the present invention.
Detailed Description
The present invention is described in detail below with reference to the attached drawings. It is to be understood, however, that the drawings are provided solely for the purposes of promoting an understanding of the invention and that they are not to be construed as limiting the invention. In the description of the present invention, it is to be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
According to the principle of the time-of-flight pulsed three-dimensional laser radar, the distance measurement core of the three-dimensional laser radar is a pulsed distance measurement system based on the time-of-flight method, so that the time point identification method provided by the invention is also suitable for the pulsed laser distance measurement system or a two-dimensional or three-dimensional laser radar system based on different light beam scanning modes.
As shown in fig. 1, if the three echoes with different amplitudes come from targets with the same distance and different reflectivities, and if the time point identification is performed by using the uniform constant level V3, the time difference between the echo 1 and the time point T1, between the echo 2 and the time point T2, between the echo 3 and the time point T3, between the T1 and the T3, and between the T2 and the T3, is a time point error, which may cause a distance measurement error. If the echoes 1, 2 and 3 are subjected to time point identification (that is, the arrival time of the echoes is judged) by respectively using the V1, the V2 and the V3, and the peak ratios of the V1, the V2 and the V3 to the echoes 1, 2 and 3 are the same, the timing points of the echoes 1, 2 and 3 are all T3 theoretically, and no timing error exists.
Based on the principle, in order to realize the constant ratio time point identification, the invention provides a time point identification method, which comprises the following steps: at each ranging, the echo pulse is first subjected to peak measurement or peak hold, and the peak voltage of the pulse attenuated by a certain proportion (e.g., 70%) is used as the time point discrimination level of the current echo pulse.
As shown in fig. 2, the time point identification method of the present invention is implemented by the following steps: during ranging, dividing the detected echo pulse into two paths, and performing peak holding processing on one path, wherein the peak holding processing is used for converting the echo pulse into a direct current level, and the voltage value of the direct current level is the peak voltage of the echo pulse; and attenuating the dc level by a set proportion, for example 70%, the attenuated output being shown as V1 in fig. 1; the other path is subjected to delay processing, the delay processing realizes nanosecond-level delay of the echo pulse, the delay amount is ensured to be larger than the time delay caused by peak value holding and attenuation, and the output of the delay processing is shown as the echo 1 in fig. 1. And comparing the voltage values of the attenuated direct current level and the delayed echo pulse, and taking the time when the voltage value comparison result changes as the arrival time of the echo pulse, wherein when the amplitude of the echo pulse changes, the voltage value of the time point identification level also changes, so that the time point identification independent of the echo intensity is realized. As shown at T1 in fig. 1. When the amplitude of the echo pulse changes, the voltage value of the time point discrimination level also changes, and the time point discrimination independent of the echo intensity is realized as shown in fig. 1.
As shown in FIG. 3, based on the time point identification method of the present invention, the present invention further provides a distance measurement system independent of echo intensity, which includes a main controller 1, a pulsed laser 2, a beam splitter 3, first to second detectors 4 to 5, first to second amplifiers 6 to 7, a first comparator 8, a timing circuit 9, and a time point identification circuit system 10, wherein the time point identification circuit system 10 includes a peak value keeper 11, a delay 12, an attenuator 13, and a second comparator 14.
The main controller 1 controls the pulse laser 2 to send out a detection pulse, and starts a distance measuring process.
Laser pulse emitted by the pulse laser 2 is divided into two paths of light by the spectroscope 3, one path of light reflected by the spectroscope 3 is output to the first detector 4 through a reflecting mirror, the first detector 4 performs photoelectric conversion on an optical signal and then sends the optical signal to the first amplifier 6, the first amplifier 6 and a constant level signal are respectively connected with two input ends of the first comparator 8, and the output end of the first comparator 8 is connected with the timing circuit 9 to serve as a timing starting signal, namely the laser pulse emission time. The timing circuit 9 realizes recording of the time difference Δ T between the timing start signal and the timing end signal (i.e., the arrival time of the laser echo pulse).
The other path of light transmitted by the spectroscope 3 is emitted to the object to be measured as a detection pulse, and a signal diffusely reflected by the object to be measured is emitted to the second detector 5. The second detector 5 performs photoelectric conversion on the optical signal and transmits the optical signal to the second amplifier 7, the signals output by the second amplifier 7 are respectively transmitted to the peak value holder 11 and the delayer 12, and the peak value holder 11 realizes that the peak value of the echo pulse is held at a direct current level; the delay 12 achieves nanosecond delay of the echo pulse, ensuring that the amount of delay is greater than the delay caused by the peak keeper and attenuator. The signal output from the peak holder 11 is sent to the attenuator 13, and the attenuator 13 attenuates the dc level output from the peak holder 11 by a predetermined ratio. The output signals of the attenuator 13 and the delay 13 are sent to the second comparator 14, and time point discrimination independent of the echo intensity is completed. The signal output from the second comparator 14 is sent to the timing circuit 9 as a trigger signal as a timing end signal, that is, the time when the laser echo pulse arrives.
The timer circuit 9 records a time difference Δ T between a timing start signal (i.e., a laser pulse emission timing) and a timing end signal (i.e., a laser echo pulse arrival timing), and transmits Δ T as a result of this measurement to the main controller 1.
The main controller 1 implements the following calculation according to Δ T to obtain the distance value L measured this time:
wherein C is the speed of light.
The above embodiments are only used for illustrating the present invention, and the structure, connection mode, manufacturing process, etc. of the components may be changed, and all equivalent changes and modifications performed on the basis of the technical solution of the present invention should not be excluded from the protection scope of the present invention.
Claims (3)
1. A time point identification method is characterized by comprising the following steps:
dividing echo pulses obtained by detection in measurement into two paths;
one path is subjected to peak value holding processing, the peak value holding processing is used for converting the echo pulse into a direct current level, the voltage value of the direct current level is the peak voltage of the echo pulse, and the direct current level is attenuated in a set proportion;
the other path is subjected to delay processing, the delay processing is used for carrying out nanosecond-level delay on the echo pulse, and the delay quantity is ensured to be larger than the time delay caused by peak value holding and attenuation;
and comparing the voltage values of the attenuated direct current level and the delayed echo pulse, and taking the time when the voltage value comparison result changes as the arrival time of the echo pulse, wherein when the amplitude of the echo pulse changes, the voltage value of the time point identification level also changes, so that the time point identification independent of the echo intensity is realized.
2. Timing discrimination circuitry comprising a peak holder, an attenuator, a delay, and a comparator; the peak value keeper is used for keeping the peak value of the echo pulse to be a direct current level and sending the peak value to the attenuator, the attenuator is used for attenuating the direct current level in a set proportion, the delayer is used for delaying the echo pulse in a nanosecond level, and output signals of the attenuator and the delayer are sent to the comparator to be compared and processed to obtain the arrival time of the echo pulse.
3. A laser ranging system comprising a master controller, a pulsed laser, first to second detectors, first to second amplifiers, a first comparator, a timing circuit, and the timing discrimination circuitry of claim 2;
the main controller controls the pulse type laser to emit detection pulses, and the laser pulses emitted by the pulse type laser are divided into two paths of light;
one path of light is emitted to the first detector, the first detector carries out photoelectric conversion on an optical signal and then sends the optical signal to the first amplifier, the first amplifier and a constant level signal are respectively connected with two input ends of the first comparator, and the output end of the first comparator is connected with the timing circuit to serve as a timing starting signal;
the other path of light is emitted to a measured object as a detection pulse, a signal diffusely reflected by the measured object is emitted to the second detector, the second detector carries out photoelectric conversion on the light signal and then emits the light signal to the second amplifier, the signal output by the second amplifier is respectively sent to the peak value retainer and the delayer, the signal output by the comparator is sent to the timing circuit as a timing end signal, and the timing circuit records the time difference between the timing start signal and the timing end signal and sends the timing end signal to the main controller.
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| CN115184907B (en) * | 2022-09-08 | 2022-12-16 | 北醒（北京）光子科技有限公司 | Balance detection circuit and laser ranging system |
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