CN113093214A - Method and device for measuring distance by pulse laser - Google Patents
Method and device for measuring distance by pulse laser Download PDFInfo
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- CN113093214A CN113093214A CN202110399496.4A CN202110399496A CN113093214A CN 113093214 A CN113093214 A CN 113093214A CN 202110399496 A CN202110399496 A CN 202110399496A CN 113093214 A CN113093214 A CN 113093214A
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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
- G01S17/46—Indirect determination of position data
- G01S17/48—Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
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- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The invention relates to the field of laser ranging, in particular to a pulse laser ranging method. The method comprises the following steps: emitting ranging laser, receiving reflected light of the ranging laser, and performing photoelectric conversion on a reflected light signal to obtain a corresponding echo waveform; acquiring an echo waveform within a preset waveform threshold range, wherein the lower limit of the preset waveform threshold range is a low threshold voltage, and the upper limit of the preset waveform threshold range is a high threshold voltage; if the acquired echo waveform is not in the range of the preset waveform threshold, adjusting the intensity of the ranging laser to emit the ranging laser again, and acquiring the echo waveform; and obtaining the arrival time point of the echo according to the echo waveform, and calculating the distance between the measured object and the echo waveform according to the arrival time point of the echo. The invention can obtain more accurate echo signals, and the measurement precision is higher during laser ranging. The invention also provides a device for measuring the distance by the pulse laser.
Description
[ technical field ] A method for producing a semiconductor device
The invention relates to the field of laser ranging, in particular to a method and a device for pulse laser ranging.
[ background of the invention ]
Laser ranging is used as a means for measuring distance, and the ranging accuracy is an important index. The existing laser ranging methods include a pulse method, a phase method and a triangle method. The invention relates to pulsed laser ranging. The general principle of pulse laser ranging is that a laser range finder or a laser radar emits a beam of ranging laser, after the ranging laser irradiates a target object, a reflected light signal (called echo) is returned and received by the laser range finder or the laser radar, the laser range finder or the laser radar calculates the time difference between the ranging laser emission and the echo reception, and the distance between a laser emission point and the surface of the measured object is calculated according to the time difference and the propagation speed of light in the air.
In practical use, the method for improving accuracy by pulsed laser ranging is usually to average multiple measurements or perform various circuit or algorithm processing on the received echo signal. Although the method of averaging multiple measurements can eliminate the random error of measurement, the measurement accuracy cannot be really improved. When the method for processing the echo signal is used, if the echo signal is too strong, a receiving circuit can generate a saturation phenomenon, and inaccurate measurement can be caused when the received signal is saturated; and the echo signal is too weak, interference in a circuit can influence a real signal, the signal is unstable, and measurement inaccuracy is also caused.
In view of this, how to overcome the defects existing in the prior art and improve the precision of laser ranging is a problem to be solved in the technical field.
[ summary of the invention ]
Aiming at the defects or the improvement requirements of the prior art, the invention solves the problems of the prior laser ranging method that the precision is not enough due to the improper light signal intensity and the circuit interference.
The embodiment of the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for measuring a distance by using a pulsed laser, specifically comprising:
preferably, the method comprises the steps of emitting ranging laser, receiving reflected light of the ranging laser, and performing photoelectric conversion on a reflected light signal to obtain a corresponding echo waveform; acquiring an echo waveform within a preset waveform threshold range, wherein the lower limit of the preset waveform threshold range is a low threshold voltage, and the upper limit of the preset waveform threshold range is a high threshold voltage; if the acquired echo waveform is not in the range of the preset waveform threshold, adjusting the intensity of the ranging laser to emit the ranging laser again, and acquiring the echo waveform; and obtaining the arrival time point of the echo according to the echo waveform, and calculating the distance between the measured object and the echo waveform according to the arrival time point of the echo.
Preferably, the acquiring of the echo waveform within the preset waveform threshold range specifically includes: acquiring the maximum voltage value of an echo waveform; judging whether the maximum voltage value of the echo waveform is higher than a low threshold voltage, if so, acquiring the echo waveform, and if not, discarding the echo waveform; and acquiring a saturation interval of the echo waveform exceeding a high threshold voltage, judging whether the saturation interval exceeds a preset saturation interval threshold value, if so, discarding the echo waveform, and if not, acquiring the echo waveform.
Preferably, the determining whether the saturation interval exceeds a preset saturation interval threshold specifically includes: starting time counting when the voltage value of the echo waveform exceeds a high voltage threshold, stopping time counting until the voltage value of the echo waveform is reduced below the high voltage threshold, and acquiring the number of clock points in a saturation interval; if the number of clock points in the saturation interval is larger than that of the preset saturation interval threshold value, the saturation interval of the current echo waveform exceeds the preset saturation interval threshold value.
Preferably, adjusting the ranging laser intensity to re-emit the ranging laser specifically includes: if the maximum voltage value of the echo waveform is lower than the low threshold voltage, the light intensity of the ranging laser is improved; and if the saturation interval of the echo waveform exceeds a preset saturation interval threshold value, reducing the light intensity of the ranging laser.
Preferably, the method further comprises the following steps: obtaining ranging laser light intensity values respectively corresponding to a high voltage threshold and a low voltage threshold; taking the light intensity value corresponding to the high voltage threshold as a light intensity lower limit and the light intensity value corresponding to the low voltage threshold as a light intensity upper limit as a light intensity adjusting interval; setting at least one light intensity adjusting point in the light intensity adjusting interval; and adjusting the maximum value of the light intensity of the ranging laser to a corresponding light intensity adjusting point according to the echo waveform.
Preferably, after acquiring the echo waveform within the preset waveform threshold range, the method further includes: and acquiring the light intensity of the ranging laser corresponding to the echo waveform, and storing the light intensity as the light intensity used when the ranging laser is transmitted next time.
Preferably, before emitting the ranging laser, the method further comprises: and determining the light intensity value of the ranging laser according to one or more of the maximum measuring distance corresponding to the reflectivity of the target object, the radar transmitting power and the laser wavelength.
Preferably, the obtaining of the time point of arrival of the echo according to the echo waveform specifically includes: and obtaining a rough starting point of the echo curve according to the starting point judgment threshold, calibrating the rough starting point to an accurate starting point according to the waveform of the echo curve, and taking the accurate starting point as the arrival time point of the echo.
Preferably, when there are a plurality of available light intensity values of the ranging laser, the calibration value of the preset waveform threshold range is obtained for each light intensity value
On the other hand, the invention provides a device for measuring distance by using pulse laser, which specifically comprises the following steps: the optical attenuator comprises a laser emitting component 1, an optical attenuator 2, a laser receiving component 3, a photoelectric conversion component 4 and a control component 5, and specifically comprises the following components: the control interface of the laser emitting component 1 is connected with the optical attenuator 2, the control interface of the optical attenuator 2 is connected with the control component 5, and the light outlet of the laser emitting component 1 emits ranging laser to the outside; a receiving port of the laser receiving part 3 receives the echo, an optical signal output port of the laser receiving part 3 is connected with an optical signal input port of the photoelectric conversion part 4, and an electrical signal output port of the photoelectric conversion part 4 is connected with the control part 5; the control unit 5 comprises at least one processor 51 and at least one memory 52, the at least one processor 51 and the at least one memory 52 are connected via a data bus, and the memory 52 stores instructions executable by the at least one processor 51, and the instructions are used for performing the method for pulsed laser ranging provided by the first aspect after being executed by the processor 51.
Compared with the prior art, the embodiment of the invention has the beneficial effects that: according to the invention, through the judgment of the light intensity of the echo signal, an inaccurate measurement signal with over-strong or over-weak light intensity is abandoned, the most appropriate test light intensity is found, and a more accurate echo signal is obtained, so that the measurement precision during laser ranging is higher. In a preferred embodiment of this embodiment, the laser radar can acquire an echo waveform more suitable for calculation by adjusting the light intensity, calibrating the start point of the echo waveform, and the like, thereby further improving the measurement accuracy.
[ description of the drawings ]
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is a flowchart of a method for measuring a distance by using a pulsed laser according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an echo waveform used in a pulsed laser ranging method according to an embodiment of the present invention;
FIG. 3 is a flow chart of another method for measuring distance by using a pulsed laser according to an embodiment of the present invention;
FIG. 4 is a flow chart of another method for measuring distance by using a pulsed laser according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a pulsed laser ranging apparatus according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a control component 5 of a pulsed laser ranging apparatus according to an embodiment of the present invention;
wherein the reference numbers are as follows:
1: laser emitting component, 2: optical attenuator, 3: laser receiving part, 4: photoelectric conversion member, 5: control means, 51: a processor; 52: a memory.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The present invention is a system structure of a specific function system, so the functional logic relationship of each structural module is mainly explained in the specific embodiment, and the specific software and hardware implementation is not limited.
In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other. The invention will be described in detail below with reference to the figures and examples.
Example 1:
the pulse laser ranging needs to calculate the distance according to the echo receiving time, and the accuracy of the echo waveform acquisition influences the ranging precision. Due to the limitation of circuit bandwidth and the influence of circuit noise, in the process of converting the optical signal of the echo signal into the electric signal, the most accurate echo signal waveform can be obtained only when the energy of the echo signal is within a certain specific range, and the most accurate echo initial position is calculated. Therefore, it is necessary to find a suitable measured light intensity to obtain an accurate echo. In order to improve the precision of laser ranging, a proper echo signal waveform, namely proper emission light intensity, needs to be found, and the method and the device judge whether the emitted light intensity is proper or not through the waveform of the echo signal so as to guide the adjustment direction and the adjustment intensity of the light intensity, finally obtain the proper echo waveform and obtain more accurate distance measurement.
As shown in fig. 1, the method for measuring distance by using pulsed laser according to the embodiment of the present invention includes the following steps.
Step 101: and transmitting the ranging laser, receiving reflected light of the ranging laser, and performing photoelectric conversion on the reflected light signal to obtain a corresponding echo waveform.
When the range radar uses pulse laser to carry out distance measurement, at first by the transmitting module of radar according to predetermined pulse waveform transmission range laser, the range laser is reflected back to the radar after meetting the barrier, and the receiving module of radar receives the reverberation, according to the time difference of range laser emission time and reverberation arrival time, according to the formula: the distance is the speed of light at time, and the distance between the laser and the obstacle is obtained.
The ranging radar can directly and accurately obtain the emission time of the ranging laser, but the arrival time of the reflected light needs to be passively received. Therefore, the accuracy of the range radar in receiving the reflected light will directly affect the accuracy of the calculated range. In practical use, the time of arrival of the emitted light cannot be accurately obtained when the emitted light is too strong or too weak, and the intensity of the reflected light is directly related to the intensity of the ranging laser. In order to obtain proper reflected light intensity, before the ranging laser is emitted, the light intensity value of the ranging laser is determined according to one or more of the maximum measuring distance corresponding to the reflectivity of the target object, the radar emission power and the laser wavelength.
(1) Maximum measurement distance: the light intensity value needs to satisfy the maximum measurement distance of an object with a certain reflectivity of the radar index, namely the maximum distance reported by a number value under the condition of not recording errors. In the specific implementation, if the radar index requires that the maximum measurement distance is 100 meters when the reflectivity is 10%, and the distance with the error of 5% is 60 meters. The lowest light intensity is required to ensure that the echo is received when the reflectivity of the target object is 10% at a measurement distance of 100 meters and the measurement error is within 5% at a measurement distance of 60 meters. Under the same distance, the smaller the transmitting power of the object with the same reflectivity is, the smaller the received echo signal is; objects of the same reflectivity use the same transmitting power, and the farther the distance is, the smaller the received echo signal is. Therefore, if the intensity of the emitted light is too low, the reflected light is too weak, and an echo signal may not be obtained at a corresponding measurement distance.
(2) Radar transmission power: in the embodiment, the pulsed laser is used for distance measurement, and the peak power and the total power of the laser are represented by the same value, so that the maximum value of the light intensity of the laser radar cannot exceed the peak power of the laser, otherwise, error reporting of the laser or laser power limitation can be caused.
(3) Laser wavelength: the light intensity of the measured laser echo changes regularly along with the emitted light power, the measured distance and the reflectivity, and the change rules are different under the condition of using lasers with different wavelengths, so that for the lasers with different wavelengths, corresponding light intensity values of the measured laser need to be obtained respectively to meet the measurement requirements.
In specific implementation, the appropriate light intensity parameter can be found through a method of experimental tests. If the maximum measurement distance required by the reflectivity of 10% is 100 meters, a reflecting plate with 10% can be placed at the distance of 100 meters, the maximum light intensity which can be reached by the transmitting power of a laser is firstly used for testing to obtain an echo signal, if the maximum voltage value of the echo signal is greater than the low threshold voltage, the light intensity can be reduced until the maximum voltage value of the echo signal is greater than and closest to the low threshold voltage, and the used light intensity is the light intensity value of the ranging laser. For different reflectivity and distance measurement laser wavelengths, experiments are needed to obtain light intensity values.
In signal processing and calculation, since an optical signal cannot be used as it is, it is necessary to photoelectrically convert a reflected light signal of the received ranging laser light into an echo waveform in the form of an electrical signal corresponding to the optical signal waveform. Because the reflected light energy is large, a high voltage appears when the echo waveform is converted into an electric signal, and the time between the laser and the barrier in the air can be obtained by calculating the time difference from the laser emission time to the initial position of receiving the high voltage of the echo, so that the distance between the laser and the barrier can be further obtained. As shown in fig. 2, the curve in the figure is an echo waveform, and the position of 0 point indicates the real starting position of the echo signal. However, in actual use, due to factors such as optical signal intensity, circuit noise, and transmission bandwidth, the echo waveform after photoelectric conversion does not always completely match the optical intensity waveform, and it is difficult to accurately locate the O point of the echo waveform. Therefore, when distance measurement is actually performed, a threshold needs to be determined according to a theoretical starting point of an echo waveform to distinguish an echo signal from a noise signal, in order to improve receiving accuracy, the starting point determination threshold is usually set to be lower and is generally selected to be a place which is a little higher than circuit noise, and when the echo waveform exceeds the starting point determination threshold, a time point coordinate corresponding to a front intersection point of the starting point determination threshold and the echo waveform is an echo high-voltage starting time point, namely an echo arrival time point. As shown in fig. 2, A, B, C are high voltage starting positions of the echo waveform curves 1, 2, and 3, respectively, the corresponding time coordinate of each point can be regarded as a time point of receiving the echo signal, and F, E, D are high voltage ending positions of the echo waveform curves 1, 2, and 3, respectively. By the time value of the initial position, the time from the emission of the laser to the high-voltage initial position of the received echo signal can be obtained, and the distance of the obstacle can be calculated.
Step 102: and acquiring the echo waveform within the range of the preset waveform threshold.
In step 101, when performing photoelectric conversion, the voltage value of the echo waveform is proportional to the light intensity signal. Due to the circuit and algorithm of photoelectric conversion, when the light intensity is too low, the electric signal converted from the optical signal is greatly influenced by signal interference; when the light intensity is too high, a saturation phenomenon occurs; only when the light intensity is within a proper interval range, the interference noise can be obviously distinguished, and the waveform distortion caused by saturation can be avoided. Therefore, in the present embodiment, instead of simply using all echo waveforms directly for numerical averaging or calculation correction as in the prior art, usability of echo waveforms is evaluated, and only appropriate echo waveform data is selected for calculation. The voltage value range corresponding to the interval range with the appropriate light intensity is a preset waveform threshold range, wherein the lower limit of the preset waveform threshold range is a low threshold voltage, and the upper limit of the preset waveform threshold range is a high threshold voltage. As shown in the graph of fig. 2, the ordinate in the graph is the voltage value after photoelectric conversion. When the optical signal of the ranging laser is too strong, the electric signal converted from the echo appears a full-gear phenomenon, the maximum voltage value of the electric signal exceeds a high voltage threshold, a curve 1 in fig. 2 is formed, the rising curve is too steep, and the position of the starting point may be earlier than the position of the real starting point; when the optical signal of the ranging laser is too weak, the voltage of the electric signal converted by the echo is too small, and the maximum voltage value of the electric signal is smaller than the low voltage threshold, so that a curve 3 in fig. 2 is formed, the echo signal cannot be distinguished from interference noise, and the position of the starting point may be delayed; only if the size of the optical signal is proper, the obtained echo waveform of the electric signal can be clearly distinguished from noise interference, and the distance of the target object is suitable for calculating according to the regular change of a theoretical curve, such as a curve 2 in fig. 2, wherein the maximum voltage value of the electric signal is between a high voltage threshold and a low voltage threshold, namely within a preset waveform threshold range. In the distance measuring method provided in this embodiment, only the echo waveform pair corresponding to the curve 2 is acquired to calculate the distance, and the echo waveforms corresponding to the curves 1 and 3 are discarded.
In a specific implementation, as shown in fig. 3, the following steps may be used to select an appropriate echo waveform.
Step 201: and acquiring the maximum voltage value of the echo waveform.
In practical implementation, whether the echo waveform is suitable or not can be judged through various geometric parameters of the echo waveform curve, such as whether the echo waveform conforms to a formula of a theoretical curve or not, the slope of the rising edge of the echo waveform, various limit values of the echo waveform, and the like. In the present embodiment, for the sake of simple calculation, whether the echo waveform is appropriate or not is determined by the maximum value of the ordinate of the echo waveform, that is, the maximum voltage value of the echo waveform.
Step 202: judging whether the maximum voltage value of the echo waveform is higher than the low threshold voltage, if so, acquiring the echo waveform, and continuing to judge in the step 203; if not, the echo waveform is discarded.
When the judgment is carried out, the low voltage threshold and the high voltage threshold of the echo waveform need to be determined firstly. Specifically, the light intensity range of the ranging laser capable of being measured more accurately can be obtained through theoretical calculation or actual test.
If the maximum voltage value of the echo waveform exceeds the low threshold voltage, the light intensity of the echo is indicated to be normal, and the echo waveform is obtained for further judgment. If the maximum voltage value of the echo waveform does not exceed the low threshold voltage, the voltage value of the echo waveform is low, which indicates that the light intensity of the echo is too small to accurately judge the initial position, and the echo waveform is discarded. The echo waveform with too low an intensity is initially excluded, via step 202.
Step 203: and acquiring a saturation interval of the echo waveform exceeding the high threshold voltage, and judging whether the saturation interval exceeds a preset saturation interval threshold value. If yes, discarding the echo waveform; if not, the echo waveform is obtained.
In step 202, the echo waveform with too small light intensity is eliminated, and the echo waveform with too large light intensity is also eliminated. In this embodiment, the echo with normal light intensity and the echo with too high light intensity are distinguished by using a high threshold voltage, when the light intensity is too high, the maximum voltage value of the echo waveform may exceed the high threshold voltage to generate a full-shift phenomenon, and the rising curve of the echo waveform with the full-shift phenomenon is too steep, so that the curve starting point cannot be accurately obtained, and therefore the echo needs to be discarded. For convenience of description, an interval of the waveform exceeding the high threshold voltage on the time axis in the present embodiment is referred to as a saturation interval. Further, in the actual measurement, due to the reflectivity, the circuit interference, the deviation between the theoretical value and the actual value, and the like, the echo waveform of the normal light intensity may also exceed the high threshold voltage. In general, since the saturation range of the echo waveform in which the reflected light is excessively large is large and the saturation range of the echo waveform of the normal reflected light is small or none, two kinds of echo waveforms can be distinguished by the range of the saturation range. The echo waveform with overlarge light intensity is obtained when the range of the saturation interval exceeds a preset saturation interval threshold value, and needs to be discarded; the echo waveform with the saturation interval range smaller than the preset saturation interval threshold value and the normal light intensity can be used for distance measurement calculation. In specific implementation, a specific value of the preset saturation interval threshold is set according to the ranging precision, a theoretical waveform curve, specific experimental data and the like, and is generally a maximum value of a saturation interval of an echo waveform capable of accurately ranging. Specifically, in practical implementation, since the range of the saturation interval and the preset saturation interval threshold are time values, for simplicity and convenience of calculation, a software or hardware clock may be used to count the time, and the time value of the saturation interval may be calculated according to the number of clock points in the saturation interval. And starting time counting when the voltage value of the echo waveform exceeds the high voltage threshold, stopping time counting until the voltage value of the echo waveform is reduced below the high voltage threshold, and acquiring the number of clock points in a saturation interval through a counting value. If the number of clock points in the saturation interval is larger than that of the preset saturation interval threshold, the current saturation interval of the echo waveform exceeds the preset saturation interval threshold, which indicates that the light intensity is too large, and the echo waveform needs to be discarded; if the number of clock points in the saturation interval is less than that of the preset saturation interval threshold, the current saturation interval of the echo waveform does not exceed the preset saturation interval threshold, the light intensity is appropriate, and the echo waveform can be used for ranging calculation.
Through steps 201 to 203, echo waveforms within a preset waveform threshold range can be acquired, and the ranging laser intensities corresponding to these waveforms are appropriate, the waveform regularity is good, the time points at which the echoes arrive can be acquired more accurately, and the method can be directly used for calculating the distance in step 104. For the echo with too small light intensity or too large light intensity, the echo waveform is not in the range of the preset waveform threshold, and the arrival time point of the echo cannot be accurately obtained, so that the echo waveform is discarded, and after the light intensity of the ranging laser is adjusted by using the method in step 103, the ranging laser is transmitted again by using the adjusted light intensity and the echo is received, so as to obtain the echo waveform which can be used for calculation.
Furthermore, if the currently received echo waveform is within the preset waveform threshold range, the currently used ranging laser light intensity can accurately perform ranging when the external environment is not changed, so that the same light intensity can be used for ranging when the external environment is not changed during the next ranging. For convenience in use, when the echo waveform within the preset waveform threshold range is acquired, the light intensity of the ranging laser corresponding to the echo waveform can be acquired at the same time, and the light intensity is stored and used as the light intensity used when the ranging laser is transmitted next time.
Step 103: and if the acquired echo waveform is not in the range of the preset waveform threshold, adjusting the intensity of the ranging laser to emit the ranging laser again, and acquiring the echo waveform.
If the saturation interval of the echo waveform discarded in step 102 exceeds the preset saturation interval threshold, as shown in waveform 1 in fig. 2, the echo is too strong, which indicates that the light intensity of the ranging laser is too high and weaker light intensity needs to be used. If the maximum voltage value of the echo waveform is lower than the low voltage threshold, such as waveform 3 in fig. 2, the echo is too weak, which indicates that the light intensity of the ranging laser is too small, and a stronger light intensity needs to be used. In both cases, an accurate echo waveform starting point cannot be acquired according to the current echo waveform, that is, the accurate arrival time of the echo cannot be acquired, so that the method cannot be used for ranging calculation. At this time, the light intensity of the ranging laser to be transmitted next time needs to be adjusted according to the current echo waveform, so that the echo waveform to be received next time is within the preset waveform threshold range.
Specifically, as shown in fig. 4, the light intensity may be adjusted by the following steps.
Step 301: a high voltage threshold and a low voltage threshold are obtained.
In specific implementation, the laser light intensity values corresponding to the high threshold voltage and the low threshold voltage can be obtained through experimental values, and the high threshold voltage and the low threshold voltage are respectively obtained through experiments.
(1) Low voltage threshold: when the laser receiving component does not receive the echo waveform, a very small voltage is generated, the voltage value is called a baseline and is generally not 0, in actual use, a wide-spectrum light (such as sunlight) is generally used for irradiating the received photoelectric module, the laser receiving component is tested to obtain the maximum value of the baseline, and a low-voltage gate is limited to a position which is a little larger than the maximum value of the baseline so as to distinguish the waveforms of the baseline and the echo.
(2) High voltage threshold: the laser receiving component can generate a saturation phenomenon when the light intensity is too high, the maximum light intensity of the laser is used as the measured light intensity, a very close target with very high reflectivity is measured, the echo waveform is saturated, and the position where the maximum voltage of the saturation waveform is a little smaller is taken as a high voltage threshold, so that the saturation waveform is avoided.
Step 302: and moving the target object meeting the radar reflectivity requirement from the radar maximum measurement distance position to the radar direction until the voltage value of the echo waveform is lower than the high voltage threshold, increasing the attenuation value of the ranging laser until the echo signal is higher than the low voltage threshold, and taking the attenuation value of the ranging laser as a light intensity adjusting point.
In practical implementation, in order to avoid frequent adjustment of laser power, the light intensity of the ranging laser may be adjusted by using an attenuator, an attenuation value corresponding to each light intensity is used as a light intensity adjustment point, and the attenuation value of the light intensity adjustment point may be searched through practical tests. Specifically, the target object may use a reflecting plate with a reflectivity requirement of the radar index number, the reflecting plate is placed at the position of the maximum test distance, the light intensity of the test laser is set to be the maximum light intensity, the attenuator is set to be 0, and the maximum value of the echo signal should be slightly higher than the low voltage threshold at this time. And then the distance of the reflecting plate is shortened, the echo signal is slightly lower than the high voltage threshold, the attenuation value of the attenuator is increased at the position until the echo signal is slightly higher than the low voltage threshold, and the attenuation value at the moment is recorded and used as a first-gear light intensity adjusting point.
Step 303: the reflectivity of the target object is adjusted, and at least one light intensity adjusting point is arranged in the light intensity adjusting interval.
In order to adjust the light intensity of the ranging laser, a plurality of light intensity adjusting points can be arranged in the light intensity adjusting interval, and the light intensity of the ranging laser emitted next time is directly adjusted to the light intensity adjusting points. In specific implementation, after the light intensity adjustment points are obtained for the first time, the reflecting plate with high emissivity is replaced when the reflecting plate is close to the radar, the position of the reflecting plate is adjusted to make the echo waveform consistent with the height of the previous reflecting plate when the previous reflecting plate is close to the radar, and then the operation in step 302 is repeated to obtain the light intensity adjustment points corresponding to different reflectances until the reflecting plate with the maximum reflectivity is used. Since the reflectivity of an object in nature is generally below 200%, when a qualified waveform can be achieved when the reflector plate is close to the radar, the acquisition of the light intensity adjustment point is stopped. The light intensity adjusting point obtained through actual test can theoretically ensure that the echo waveform is within the range of the preset waveform threshold. In different implementation scenes, the adjustment step length of the reflectivity can be selected according to needs, so that the adjustment amplitude is small during each light intensity adjustment, and the convenience and the accuracy of the adjustment are improved. In specific implementation, the plurality of light intensity adjustment points may be stored as a list for obtaining, or may be adjusted by setting a corresponding adjustment step length.
Step 304: and adjusting the attenuation value of the ranging laser to a corresponding light intensity adjusting point according to the echo waveform.
As shown in fig. 2, the light intensity corresponding to curve 1 is too high, and the light intensity needs to be reduced, and the light intensity adjustment point with a higher attenuation value is selected to reduce the light intensity of the test laser. The light intensity corresponding to curve 3 is too small, the light intensity needs to be increased, and the light intensity of the test laser is improved by using a light intensity adjusting point with lower attenuation degree.
Through steps 301 to 304, the light intensity corresponding to the echo waveform discarded after exceeding the preset waveform threshold range is adjusted, so that the echo waveform obtained next time can be theoretically within the preset waveform threshold range, and the time point of arrival of the echo can be accurately obtained.
Further, in the actual ranging, due to the fact that the measured object is too far away, the reflectivity of the surface of the measured object is not appropriate, equipment is failed, and the like, even if the light intensity of the ranging laser is adjusted, an appropriate echo waveform cannot be acquired. In order to avoid influencing the working efficiency of distance measurement, a threshold value of the light intensity adjustment times can be set, when the adjustment times exceed the threshold value, the light intensity is not adjusted for measuring distance again, but an alarm prompt is given to a user to remind the user to carry out proper adjustment.
Step 104: and obtaining the arrival time point of the echo according to the echo waveform, and calculating the distance between the measured object and the echo waveform according to the arrival time point of the echo.
An echo waveform within a preset waveform threshold may be acquired, either by step 103 or by performing step 104 one or more times. At the moment, the curve of the echo waveform is regular, the time spent from the emission of the laser to the reception of the high-voltage initial position of the echo signal can be obtained accurately according to the echo waveform and the acquired time point of the arrival of the echo, and the distance of the obstacle is calculated.
Further, as can be seen from fig. 2, A, B, C points corresponding to the high voltage start positions of the echo waveform curves 1, 2, and 3 calculated according to the echo curve and the start point judgment threshold have a certain distance from the actual position 0 point at which the actual echo signal arrives, and the distance calculated by directly using the time point corresponding to A, B, C is not accurate. However, due to circuit noise and bandwidth of photoelectric conversion, the true 0 point is difficult to obtain, and only compensation calibration can be performed by using a theoretical value of an echo waveform, or a calibration value can be obtained by using specific measurement experimental data. The calibration compensation has certain requirements on the waveform, and if the waveform has long-time full gear or the maximum value of the waveform is too small, the difference between the curve of the echo waveform and the theoretical curve is large, the accurate compensation cannot be carried out. For the curve 1 in fig. 2, since the light energy is too large, the circuit is saturated immediately when the light energy is converted into an electrical signal, the rising edge is very steep, and the waveforms of the rising edges are almost the same when the saturation depths are different, so that the time exceeding the high threshold in the curve 1 is different, but the position of the point a is always the same, and thus the point a cannot be corrected to the point O by the shape of the curve 1. For curve 3 in fig. 2, since the light energy is too small, the signal and noise approach each other when converted into an electrical signal, and thus the position of point C is not stable due to the influence of circuit noise, and point C cannot be stably corrected to point O. And both the curve 1 and the curve 3 exceed the preset waveform threshold range, and the light intensity needs to be adjusted to emit ranging laser again for ranging. Only under the condition of curve 2 in fig. 2, the echo waveform is within the range of the preset waveform threshold, the light energy is large, the signal cannot be submerged in noise, the signal is stable, meanwhile, the waveform of the saturated rising edge does not exist, the waveform of the whole echo curve is regularly changed, the point of intersection of the threshold and the waveform curve can be judged according to the starting point to obtain the rough starting point B of the echo curve, and then the rough starting point B is calibrated to the accurate starting point 0 according to the waveform rule of the echo curve to obtain the accurate distance.
Further, in an implementation scenario of the present invention, there may be a plurality of different light intensity values of the ranging laser available for matching different measurement accuracies, different measurement ranges, different laser light sources, and the like. At this time, each different light intensity value corresponds to a different preset waveform threshold range, and the calibration values between the rough starting point and the precise starting point are different in the different preset waveform threshold ranges. Therefore, when calibration compensation is performed, calibration values in a preset waveform threshold range under each light intensity value need to be obtained respectively, so as to perform accurate calibration compensation on echo waveforms under different ranging laser light intensities.
After the steps 101 to 104 provided in this embodiment, a more accurate time point at which the echo arrives can be obtained, and then a distance value of the object to be measured can be calculated more accurately, so that the accuracy of the pulse laser ranging is improved in a simple and efficient manner.
Example 2:
on the basis of the method for measuring the distance by using the pulsed laser provided by the embodiment 1, the invention further provides a device for measuring the distance by using the pulsed laser, which can be used for realizing the method.
Fig. 5 is a schematic diagram of a device architecture according to an embodiment of the present invention. The pulsed laser ranging device provided by the present embodiment includes a laser emitting unit 1, an optical attenuator 2, a laser receiving unit 3, a photoelectric conversion unit 4, and a control unit 5.
The control interface of the laser emitting component 1 is connected with the optical attenuator 2, and the adjustment of the ranging laser light intensity is completed by adjusting the attenuation value of the optical attenuator 2. The control interface of the optical attenuator 2 is connected to the control unit 5, and receives the light intensity control signal sent by the control unit 5, and attenuates the light intensity accordingly. The outgoing light from the laser emitting unit 1 is attenuated by the optical attenuator 2, and then, the ranging laser having a suitable light intensity is generated and emitted to the outside through the light outlet of the laser emitting unit 1.
Further, if the ranging laser needs a plurality of different light intensities, the maximum attenuation value of the optical attenuator 2 may be adjusted according to the radar blind zone setting of the laser receiving part 3 and the maximum reflectivity of the ranging laser, and then the attenuation range of the optical attenuator 2 is divided into a plurality of intervals, and the attenuation value of each interval is used as the light intensity of one ranging laser. During specific distance measurement, the preset waveform threshold range under each light intensity needs to be adjusted according to the performance parameters of the laser receiving part 3, and corresponding calibration values are calibrated.
The receiving port of the laser receiving part 3 receives the echo, the optical signal output port of the laser receiving part 3 is connected with the optical signal input port of the photoelectric conversion part 4, the echo received by the laser receiving part 3 is received, and the echo is subjected to photoelectric conversion to generate an echo waveform represented by a voltage value. An electric signal output port of the photoelectric conversion part 4 is connected to the control part 5, and sends the echo waveform to the control part 5.
The control unit 5 receives a signal comprising one or more processors 51 and one or more memories 52. In fig. 6, a processor 51 and a memory 52 are taken as an example. The processor 51 and the memory 52 may be connected by a bus or other means, such as the bus connection in fig. 6. The memory 52, which is a non-volatile computer-readable storage medium for the pulsed laser ranging method, may be used to store non-volatile software programs, non-volatile computer-executable programs, and modules, such as the pulsed laser ranging method in embodiment 1. The processor 51 executes various functional applications and data processing in steps 102 to 104 of embodiment 1, that is, functions of the method of pulsed laser ranging in embodiment 1 other than laser signal transceiving and photoelectric conversion, by running the nonvolatile software program, instructions, and modules stored in the memory 52. The memory 52 may include high speed random access memory and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some embodiments, the memory 52 may optionally include memory located remotely from the processor 51, and these remote memories may be connected to the processor 51 via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof. Program instructions/modules are stored in the memory 52 that, when executed by the one or more processors 51, perform the method of pulsed laser ranging in embodiment 1 described above, e.g., perform the various steps illustrated in fig. 1, 3, and 4 described above. Meanwhile, the memory 52 is also used to store long-term data or temporary data such as a light intensity value, a preset waveform threshold range, a preset saturation interval threshold, a light intensity adjustment point, and a calibration value of the ranging laser used in embodiment 1.
Those of ordinary skill in the art will appreciate that all or part of the steps of the various methods of the embodiments may be implemented by associated hardware as instructed by a program, which may be stored on a computer-readable storage medium, which may include: a Read Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and the like.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A method for measuring distance by pulse laser is characterized in that:
emitting ranging laser, receiving reflected light of the ranging laser, and performing photoelectric conversion on a reflected light signal to obtain a corresponding echo waveform;
acquiring an echo waveform within a preset waveform threshold range, wherein the lower limit of the preset waveform threshold range is a low threshold voltage, and the upper limit of the preset waveform threshold range is a high threshold voltage;
if the acquired echo waveform is not in the range of the preset waveform threshold, adjusting the intensity of the ranging laser to emit the ranging laser again, and acquiring the echo waveform;
and obtaining the arrival time point of the echo according to the echo waveform, and calculating the distance between the measured object and the echo waveform according to the arrival time point of the echo.
2. The pulsed laser ranging method according to claim 1, wherein the obtaining of the echo waveform within a preset waveform threshold range specifically comprises
Acquiring the maximum voltage value of an echo waveform;
judging whether the maximum voltage value of the echo waveform is higher than a low threshold voltage, if so, acquiring the echo waveform, and if not, discarding the echo waveform;
and acquiring a saturation interval of the echo waveform exceeding a high threshold voltage, judging whether the saturation interval exceeds a preset saturation interval threshold value, if so, discarding the echo waveform, and if not, acquiring the echo waveform.
3. The method of claim 2, wherein the determining whether the saturation interval exceeds a preset saturation interval threshold specifically comprises:
starting time counting when the voltage value of the echo waveform exceeds a high voltage threshold, stopping time counting until the voltage value of the echo waveform is reduced below the high voltage threshold, and acquiring the number of clock points in a saturation interval;
if the number of clock points in the saturation interval is larger than that of the preset saturation interval threshold value, the saturation interval of the current echo waveform exceeds the preset saturation interval threshold value.
4. The method of claim 1, wherein the adjusting the ranging laser intensity re-emits the ranging laser, specifically comprising:
if the maximum voltage value of the echo waveform is lower than the low threshold voltage, the light intensity of the ranging laser is improved;
and if the saturation interval of the echo waveform exceeds a preset saturation interval threshold value, reducing the light intensity of the ranging laser.
5. The pulsed laser ranging method according to claim 4, further comprising:
acquiring a high voltage threshold and a low voltage threshold;
moving a target object which meets the radar reflectivity requirement from the radar maximum measurement distance position to the radar direction until the voltage value of an echo waveform is lower than a high voltage threshold, increasing the attenuation value of the ranging laser until an echo signal is higher than a low voltage threshold, and taking the attenuation value of the ranging laser as a light intensity adjusting point;
adjusting the reflectivity of the target object, and setting at least one light intensity adjusting point in the light intensity adjusting interval;
and adjusting the attenuation value of the ranging laser to a corresponding light intensity adjusting point according to the echo waveform.
6. The method of pulsed laser ranging according to claim 1, wherein after acquiring the echo waveform within the preset waveform threshold, the method further comprises:
and acquiring the light intensity of the ranging laser corresponding to the echo waveform, and storing the light intensity as the light intensity used when the ranging laser is transmitted next time.
7. The pulsed laser ranging method of claim 1, further comprising, before emitting the ranging laser:
and determining the light intensity value of the ranging laser according to one or more of the maximum measuring distance corresponding to the reflectivity of the target object, the radar transmitting power and the laser wavelength.
8. The pulsed laser ranging method according to claim 1, wherein the obtaining of the arrival time of the echo according to the echo waveform specifically comprises:
and obtaining a rough starting point of the echo curve according to the starting point judgment threshold, calibrating the rough starting point to an accurate starting point according to the waveform of the echo curve, and taking the accurate starting point as the arrival time point of the echo.
9. The pulsed laser ranging method of claim 8, further comprising:
when a plurality of available ranging laser light intensity values exist, calibration values of the preset waveform threshold range under each light intensity value are obtained respectively.
10. The device for measuring the distance by the pulse laser is characterized by comprising a laser emitting component (1), an optical attenuator (2), a laser receiving component (3), a photoelectric conversion component (4) and a control component (5), and specifically comprises the following components:
the control interface of the laser emitting component (1) is connected with the optical attenuator (2), the control interface of the optical attenuator (2) is connected with the control component (5), and the light outlet of the laser emitting component (1) emits ranging laser to the outside;
a receiving port of the laser receiving component (3) receives the echo, an optical signal output port of the laser receiving component (3) is connected with an optical signal input port of the photoelectric conversion component (4), and an electrical signal output port of the photoelectric conversion component (4) is connected with the control component (5);
the control unit (5) comprises at least one processor (51) and at least one memory (52), said at least one processor (51) and at least one memory (52) being connected by a data bus, said memory (52) storing instructions executable by said at least one processor (51), said instructions, after being executed by said processor (51), being adapted to perform the method of pulsed laser ranging according to any of claims 1-9.
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