CN108008373A - A kind of echo cancellation system based on pulse type laser ranging - Google Patents

Abstract

The invention discloses an echo compensation system based on pulsed laser ranging, which solves the problem of the inability to perform gain compensation according to the temperature of the APD working environment and the inability to evaluate the measurement results according to the strength of the return signal when performing laser ranging in the prior art. Correction and compensation are performed, resulting in inaccurate measurement results. Including high-voltage generation circuit, high-voltage detection circuit, temperature detection circuit, APD, IV conversion circuit, gain amplifier circuit, constant ratio timing circuit, digital filter circuit, time difference measurement circuit and the main controller controlled by high-speed FPGA as the core. The present invention adopts the operation of formula 1 and formula 2 to perform temperature compensation, and uses formula 3 to formula 7 to correct and compensate the measurement results, so that the temperature compensation is more accurate, and the measurement results after correction and compensation are more accurate.

Description

An Echo Compensation System Based on Pulsed Laser Ranging

technical field

The invention relates to the field of laser ranging, in particular to an echo compensation system based on pulsed laser ranging.

Background technique

With the development of the laser ranging industry, pulse-based laser ranging has become an indispensable part of civil and industrial applications. The main fields involve laser radar and autonomous positioning robot industry (artificial intelligence industry). Pulsed laser ranging has the characteristics of fast measurement speed and long measurement distance. The main principle is based on the design of laser flight time difference. Because it measures the time difference between emission and reception, the light reflection of objects of different materials and colors The rate is also different, so the error will be larger under different materials and colors of objects. At the same time, the change of the flight time difference will also be affected under different ambient temperatures, resulting in a large error in the measurement results.

Contents of the invention

The technical problem to be solved by the present invention is to provide an echo compensation system based on pulsed laser ranging, which solves the problem that the gain compensation cannot be performed according to the temperature of the APD working environment and the return signal cannot be compensated when performing laser ranging in the prior art. The strength corrects and compensates the measurement results, which makes the measurement results inaccurate.

To achieve the above object, the technical scheme adopted in the present invention is as follows:

An echo compensation system based on pulsed laser ranging, including a high voltage generation circuit, a high voltage detection circuit, a temperature detection circuit, an APD, an IV conversion circuit, a gain amplifier circuit, a constant ratio timing circuit, a digital filter circuit, a time difference measurement circuit and The main controller controlled by high-speed FPGA as the core;

The high-voltage generating circuit is connected to the main controller to generate an adjustable high-voltage DC voltage under the control of the main controller, and its voltage output terminal is connected to the reverse terminal of the APD to ensure that the APD is reverse-biased voltage stability;

The APD is a high-speed avalanche photodiode, which is used to detect the reflected light of an object and convert the light signal into a current signal. The output end of the current signal is connected to the I/V conversion circuit, and the temperature detection circuit is connected to the main The controller is connected to detect the temperature change of the high-speed avalanche photodiode, and transmit the detected temperature information to the main controller in real time. The high voltage detection circuit is connected with the high voltage generation circuit and the main controller respectively. The controller is connected to collect high-voltage information on the upper end of the high-speed avalanche photodiode, and feed back the collected high-voltage information to the main controller, and the main controller uses the temperature information transmitted by the temperature detection circuit to Perform high-voltage compensation on the high-speed avalanche photodiode, and control the high-voltage output of the high-voltage generating circuit according to the high-voltage information fed back by the high-voltage detection circuit, so that the high-speed avalanche photodiode can operate under various ambient temperatures Keep the best working condition, so that the high-speed avalanche photodiode can have the best gain under different ambient temperatures, so as to better receive the stability of the echo;

The IV conversion circuit converts the current signal from the APD into a voltage signal, the voltage signal output terminal is connected to the input terminal of the gain amplification circuit, and the output terminal of the gain amplification circuit is connected to the input terminal of the constant ratio timing circuit connected, the amplified voltage signal is input to the constant-ratio timing circuit, and the constant-ratio timing circuit performs constant-ratio shaping on the voltage signal input by the gain amplifier circuit, and separates the pulsed laser time-of-flight signal and the feedback wave pulse signal width signal, the output end of the constant ratio timing circuit is connected to the input end of the digital filter circuit, and is used to transmit the pulse laser time-of-flight signal and the echo pulse signal width signal to the digital A filter circuit, the digital filter circuit has two output terminals, and is respectively connected to the main controller and the time difference measurement circuit, and the digital filter circuit is used to combine the received pulse laser time-of-flight signal and the The echo pulse signal width signal is filtered and then sent to the main controller, and the time difference measurement circuit is used to filter the pulse laser flight time difference signal from the digital filter circuit and the echo The pulse signal width signal is measured, and the measured data is sent to the main controller, and the main controller controls and reads the data of the time difference measurement circuit, and performs correction and compensation according to the data.

Further, the high voltage generating circuit generates an adjustable high voltage with a voltage range of 100V-200V under the control of the main controller, and the adjustable voltage resolution is 0.5V.

Further, the measurement accuracy of the time difference measurement circuit is 10 ps, and can simultaneously measure the pulsed laser time-of-flight signal and the echo pulse signal width signal.

Further, when the main controller performs high-voltage compensation on the high-speed avalanche photodiode according to the temperature information transmitted by the temperature detection circuit, the following formula is used for high-voltage compensation:

Fn[Uapd]＝Uc+Uk*{Tx}℃ Formula 1

M＝Fn[Uapd]*K Formula 2

Among them, Fn is a unified expression of mathematical function sequence, M is the gain affected by temperature and high pressure, Fn[Uapd] is the APD bias voltage corresponding to the current temperature, Tx is the current temperature value, Uapd is the high pressure value corresponding to the current temperature, Uc is the default APD high pressure, Uk is the APD high pressure coefficient corresponding to each degree of ambient temperature, and K is a constant.

Further, after the main controller controls and reads the data of the time difference measurement circuit, and performs correction and compensation according to the data, specifically, the echo pulse signal width is converted into a signal width distance value Stw according to the following formula:

Stw＝(Td-Tu)*C Formula 3

Among them, Td is the time from the laser emission trigger signal to the falling edge of the return signal, Tu is the time from the laser emission trigger signal to the rising edge of the return signal, and C is the resolution of the speed of light. When the width of the echo pulse signal is narrowed, the calculated Stw value is also will become smaller accordingly, but the distance error will become larger, therefore, the distance errors corresponding to different Stw values are also different, these errors are pre-measured and stored in the Fn{Stw} array, and the main controller according to the real-time signal The width distance value is compared with the value stored in the Fn(Stw) array, and then the signal width distance value Stw is corrected according to the corresponding echo pulse signal width to obtain the width correction value W. The correction formula is:

W＝Fn{Stw} Equation 4

Then, W=b-k*Stw Equation 5

And, K=Fn{Stw[n+1]}-Fn{Stw[n]}, and (W≥0); Formula 6

Among them, b is the maximum compensation width corresponding to the current echo pulse signal width, K is the compensation coefficient corresponding to the current echo pulse signal width, Stw[n] is the width error look-up table, and n is the value of the current echo pulse signal width Integer, Stw is the current echo pulse signal width value;

Since the electrical signal will be delayed during the transmission of the hardware circuit, there will be a delay error, and this error is fixed, so the final measurement distance conversion formula is:

D＝C*Tu/2-Dt-W Formula 7

D is the corrected measurement distance in m, Dt is the fixed delay error in m, C is the light speed resolution, W is the width correction value in m, Tu is the laser emission trigger signal to the rising edge of the return signal time.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The high-voltage generating circuit of the present invention provides a reverse working voltage for the APD, and the high-voltage detection circuit detects the working voltage in real time, and feeds back the detected working voltage to the main controller for identification to ensure the stability of the working voltage; The temperature detection circuit detects the temperature of the APD working environment in real time, and transmits the detected APD working environment temperature to the main controller in real time, and the main controller adjusts the output voltage of the high-voltage generating circuit according to the ambient temperature; The reflected laser signal and convert the optical signal into a current signal and output it to the I/V conversion circuit; the I/V conversion circuit converts the current signal output by the APD into a voltage signal, and the signal is amplified by the gain amplifier circuit, and the constant ratio timing circuit Compare the amplified signal with constant ratio and shaping; the digital filter circuit filters out part of the clutter after shaping, and the filtered signal enters the time difference measurement circuit to accurately measure the laser flight time difference and echo width and feed back the information to controller side.

(2) The integrated temperature compensation circuit of the present invention can perform temperature compensation on the output of the APD in real time, thereby ensuring the stability of the echo signal in various environments. The present invention has the characteristics of high-precision measurement, and the system integrates a constant-ratio timing circuit , compared with the traditional time identification and other circuits more accurate, the present invention has super anti-interference ability, the signal from the constant ratio timer is screened by the digital filter, thereby filtering out the interference signal, the present invention has a degree of confidentiality High characteristics, the echo signal from the laser ranging is mainly analyzed by the main controller algorithm to obtain the compensation data.

Description of drawings

Fig. 1 is a structural block diagram of the present invention.

Figure 2 is a gain diagram under different temperature environments in laser ranging.

Figure 3 is a comparison of the echo widths of different objects in laser ranging.

Figure 4 is a comparison diagram of the time and echo width at the frontier moment of different objects in laser ranging.

Fig. 5 is a comparison diagram of the time and echo width of different objects at the front edge of the simulated ideal signal pulse width according to the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and embodiments, and the mode of the present invention includes but not limited to the following embodiments.

As shown in Figure 1, an echo compensation system based on pulsed laser ranging provided by the present invention includes a high-voltage generation circuit, a high-voltage detection circuit, a temperature detection circuit, an APD, an IV conversion circuit, a gain amplifier circuit, and a constant ratio timing circuit, digital filter circuit, time difference measurement circuit and the main controller controlled by high-speed FPGA as the core;

The high-voltage generating circuit is connected to the main controller to generate an adjustable high-voltage DC voltage under the control of the main controller, and its voltage output terminal is connected to the reverse terminal of the APD to ensure that the APD is reverse-biased voltage stability;

The APD is a high-speed avalanche photodiode, which is used to detect the reflected light of an object and convert the light signal into a current signal. The output end of the current signal is connected to the I/V conversion circuit, and the temperature detection circuit is connected to the main The controller is connected to detect the temperature change of the high-speed avalanche photodiode, and transmit the detected temperature information to the main controller in real time. The high voltage detection circuit is connected with the high voltage generation circuit and the main controller respectively. The controller is connected to collect high-voltage information on the upper end of the high-speed avalanche photodiode, and feed back the collected high-voltage information to the main controller, and the main controller uses the temperature information transmitted by the temperature detection circuit to Perform high-voltage compensation on the high-speed avalanche photodiode, and control the high-voltage output of the high-voltage generating circuit according to the high-voltage information fed back by the high-voltage detection circuit, so that the high-speed avalanche photodiode can operate under various ambient temperatures Keep the best working condition, so that the high-speed avalanche photodiode can have the best gain under different ambient temperatures, so as to better receive the stability of the echo;

The IV conversion circuit converts the current signal from the APD into a voltage signal, the voltage signal output terminal is connected to the input terminal of the gain amplification circuit, and the output terminal of the gain amplification circuit is connected to the input terminal of the constant ratio timing circuit connected, the amplified voltage signal is input to the constant-ratio timing circuit, and the constant-ratio timing circuit performs constant-ratio shaping on the voltage signal input by the gain amplifier circuit, and separates the pulsed laser time-of-flight signal and the feedback wave pulse signal width signal, the output end of the constant ratio timing circuit is connected to the input end of the digital filter circuit, and is used to transmit the pulse laser time-of-flight signal and the echo pulse signal width signal to the digital A filter circuit, the digital filter circuit has two output terminals, and is respectively connected to the main controller and the time difference measurement circuit, and the digital filter circuit is used to combine the received pulse laser time-of-flight signal and the The echo pulse signal width signal is filtered and then sent to the main controller, and the time difference measurement circuit is used to filter the pulse laser flight time difference signal from the digital filter circuit and the echo The pulse signal width signal is measured, and the measured data is sent to the main controller, and the main controller controls and reads the data of the time difference measurement circuit, and performs correction and compensation according to the data.

The high voltage generating circuit of the present invention generates adjustable high voltage with a voltage range of 100V-200V under the control of the main controller, and the adjustable voltage resolution is 0.5V.

The measurement accuracy of the time difference measuring circuit of the present invention is 10 ps, and can simultaneously measure the pulse laser flight time difference signal and the echo pulse signal width signal.

The high-voltage generating circuit of the present invention provides a reverse working voltage for the APD, and the high-voltage detection circuit detects the working voltage in real time, and feeds back the detected working voltage to the main controller for identification to ensure the stability of the working voltage; the temperature detecting circuit Detect the temperature of the APD working environment in real time, and transmit the detected APD working environment temperature to the main controller in real time, and the main controller adjusts the output voltage of the high-voltage generating circuit according to the ambient temperature; APD is used to detect the reflected laser on the projected object Signal and convert the optical signal into a current signal and output it to the I/V conversion circuit; the I/V conversion circuit converts the current signal output by the APD into a voltage signal, and the signal is amplified by the gain amplifier circuit, and the constant ratio timing circuit will amplify the The signal is compared and the ratio is constant and shaped; the digital filter circuit filters out part of the clutter after shaping, and the filtered signal enters the time difference measurement circuit to accurately measure the laser flight time difference and echo width and feed back the information to the controller. .

In order to solve a series of problems such as the influence of the ambient temperature of the APD and the influence of different material objects on the measurement results, the present invention compensates the temperature, and at the same time corrects and compensates the measurement results. The specific compensation principles are as follows.

At present, most pulse-based laser ranging is based on the distance collected and converted based on the leading time of the transmitting and receiving pulses, and it is also the most accurate measurement method at present. When the target object is placed at the same distance, but has different light reflectivity due to the difference in material and surface color, different return signals will be generated. At the same time, the accuracy of the pulse-based laser ranging will also change with the change of the ambient temperature. The distance of the same distance in different environments will be very different, which means that different materials, colors and different environments The noise will affect the accuracy of the measurement results.

The influence from temperature will change the APD gain and make the measured echo width and time-of-flight inaccurate:

The gain of APD depends on the incident light power, dark current, and ambient temperature. It is its unique internal structure. When the operating temperature and reverse bias voltage change, its response gain will change.

As shown in Figure 2, different temperatures and voltages have different gains. This will directly affect the stability of the laser echo signal; where M indicates that the corresponding gain is different at different temperatures. U/V means that if you want to obtain equivalent M at different temperatures, you need different high voltage compensation; T1...T7 means M and compensated V at different temperatures;

According to the description of the graph, in order to obtain a stable M, it is necessary to perform high voltage compensation on the APD according to the ambient temperature.

The energy intensity of light reflected by different materials and colors is different, which will also lead to different echo widths, thus directly affecting the accuracy of the distance measurement:

For example, in Figure 3, the measured object at the same distance produces two different return signals A and B due to different colors. Signal A is the return signal of a black surface measured object with low reflectivity, and signal B is a reflectance High return signal of white surface measured object.

As shown in Figure 4, since the reflectance of black is very low, the signal B detected by the APD on white is wider than the signal A detected on black, and the leading edge moment of signal A will be wider than the leading edge moment of signal B (Tu ) takes longer, and the distance calculated by signal A is greater than that calculated by signal B.

As shown in Figure 5, the present invention combines software and hardware to establish a stable and reliable "ideal signal pulse width", which is generated by a very strong target signal, and the pulse width of any normal return signal is always narrower than this ideal signal pulse width. When the real return signal becomes weaker, the pulse width of the detected return signal will become narrower, which indirectly causes the time to measure the rising edge to become longer, and the calculated distance will become larger, and this extra distance will become Therefore, there is a mathematical function relationship between the pulse width of the returned signal and the pulse width of the ideal signal, as shown in Figure 5.

When the main controller of the present invention performs high-voltage compensation on the high-speed avalanche photodiode according to the temperature information transmitted by the temperature detection circuit, the following formula is used for high-voltage compensation:

Fn[Uapd]＝Uc+Uk*{Tx}℃ Formula 1

M＝Fn[Uapd]*K Formula 2

Among them, Fn is a unified expression of mathematical function sequence, M is the gain affected by temperature and high pressure, Fn[Uapd] is the APD bias voltage corresponding to the current temperature, Tx is the current temperature value, Uapd is the high pressure value corresponding to the current temperature, Uc is the default APD high pressure, Uk is the APD high pressure coefficient corresponding to each degree of ambient temperature, and K is a constant.

After the main controller of the present invention controls and reads the data of the time difference measurement circuit, it performs correction and compensation according to the data, specifically, the echo pulse signal width is converted into a signal width distance value Stw according to the following formula:

Stw＝(Td-Tu)*C Formula 3

Among them, Td is the time from the laser emission trigger signal to the falling edge of the return signal, Tu is the time from the laser emission trigger signal to the rising edge of the return signal, and C is the resolution of the speed of light. When the width of the echo pulse signal is narrowed, the calculated Stw value is also will become smaller accordingly, but the distance error will become larger, therefore, the distance errors corresponding to different Stw values are also different, these errors are pre-measured and stored in the Fn{Stw} array, and the main controller according to the real-time signal The width distance value is compared with the value stored in the Fn(Stw) array, and then the signal width distance value Stw is corrected according to the corresponding echo pulse signal width to obtain the width correction value W. The correction formula is:

W＝Fn{Stw} Equation 4

Then, W=b-k*Stw Equation 5

And, K=Fn{Stw[n+1]}-Fn{Stw[n]}, and (W≥0); Formula 6

Among them, b is the maximum value of the compensation width corresponding to the current echo pulse signal width. According to the actual measurement, the maximum calculation value of b is 3.0m at a measurement distance of 50m, and the minimum value is 0.1cm; K is the current echo pulse signal width corresponding to The compensation coefficient of K is different according to the measurement distance and the echo pulse signal width; when K=0, W=3.0m, the minimum W=0; Stw[n] is the width error query table, n is the current Integer of echo pulse signal width value, Stw is the current echo pulse signal width value.

Since the electrical signal will be delayed during the transmission of the hardware circuit, there will be a delay error, and this error is fixed, so the final measurement distance conversion formula is:

D＝C*Tu/2-Dt-W Formula 7

D is the corrected measurement distance in m, Dt is the fixed delay error in m, C is the light speed resolution, W is the width correction value in m, Tu is the laser emission trigger signal to the rising edge of the return signal time.

The invention integrates a temperature compensation circuit, which can perform temperature compensation on the output of the APD in real time, thereby ensuring the stability of the echo signal in various environments. The invention has the characteristics of high-precision measurement, and the system integrates a constant ratio timing circuit. Compared with The traditional time identification and other circuits are more accurate. The present invention has super strong anti-interference ability. The signal from the constant ratio timer is screened by the digital filter to filter out the interference signal. The present invention has the characteristics of high confidentiality , the echo signal from the laser ranging is mainly analyzed by the main controller algorithm to obtain the compensation data.

The high-voltage generating circuit of the present invention can perform real-time high-voltage adjustment according to changes in ambient temperature, so that the APD can obtain stable gain performance. The high-voltage generating circuit has the characteristics of wide voltage, high current, bottom ripple, and adjustable output voltage.

The invention integrates a temperature compensation circuit, which is close to the APD, and is used to detect the temperature of the APD and the ambient temperature, and perform temperature compensation on the APD according to different ambient temperatures, so that the APD can work stably in various environments.

The present invention adopts a constant ratio timing circuit. Compared with the traditional time discrimination circuit and high-pass discrimination circuit, the biggest advantage is that it can solve the fluctuation of the laser echo signal generated by objects at different distances, thereby further improving the measurement accuracy.

The invention integrates a digital filter circuit, which is easy to receive the interference of external light during the laser measurement process. In order to better distinguish the authenticity of the signal, this system combines hardware digital filtering, and then analyzes the signal by software, so as to make it more accurate. It solves the problem of external light interference in laser ranging.

The present invention adopts the operation of formula 1 and formula 2 to perform temperature compensation, and uses formula 3 to formula 7 to correct and compensate the measurement results, so that the temperature compensation is more accurate, and the measurement results after correction and compensation are more accurate.

The above-mentioned embodiment is only one of the preferred implementation modes of the present invention, and should not be used to limit the scope of protection of the present invention, but any modification or embellishment without substantive significance made on the main design concept and spirit of the present invention shall be solved by it. If the technical problems are still consistent with the present invention, all should be included in the protection scope of the present invention.

Claims (5)

1. A kind of 1. echo cancellation system based on pulse type laser ranging, it is characterised in that：Including high-pressure generating circuit, high pressure inspection Slowdown monitoring circuit, temperature sensing circuit, APD, IV conversion circuit, gain amplifying circuit, constant fraction discriminator circuit, digital filter circuit, when Difference measurements circuit and the master controller by high speed FPGA for core control；

   The high-pressure generating circuit is connected with the master controller, and adjustable high voltage direct current is produced under the control of the master controller Voltage, its voltage output end are connected with the backward end of the APD, to ensure the stability of the APD reversed bias voltages；

   The APD is high speed avalanche photodiode, for detecting object reflected light, and converts optical signals into current signal, The output terminal of its current signal is connected with the I/V conversion circuits, and the temperature sensing circuit is connected with the master controller Connect, institute is sent in real time for detecting the temperature change of the high speed avalanche photodiode, and by the temperature information detected Master controller is stated, the high-voltage detecting circuit is connected with the high-pressure generating circuit and the master controller respectively, for gathering The high pressure information of the high speed avalanche photodiode upper end, and the high pressure information collected is fed back into the main control Device, the master controller according to the temperature information that the temperature sensing circuit is transmitted to the high speed avalanche photodiode into Horizontal high voltage compensates, and the high pressure information fed back according to the high-voltage detecting circuit controls the high pressure of the high-pressure generating circuit Output size, so that the high speed avalanche photodiode can keep optimum Working under various environment temperatures, makes Optimal gain can be had at different ambient temperatures by obtaining high speed avalanche photodiode, so as to preferably receive the steady of echo It is qualitative；

   Current signal from the APD is converted into voltage signal by the IV conversion circuit, its voltage signal output end and institute The input terminal connection of gain amplifying circuit is stated, the gain amplifying circuit output terminal connects with the constant fraction discriminator circuit input end Connect, amplified voltage signal, which will be inputted to the constant fraction discriminator circuit, the constant fraction discriminator circuit, to be amplified by the gain The voltage signal of circuit input carries out constant proportion shaping, and isolates pulse laser jet lag signal and echo impulse width letter Number, the output terminal of the constant fraction discriminator circuit is connected with the input terminal of the digital filter circuit, for by the pulse laser Jet lag signal and the echo pulse signal width signal are sent to the digital filter circuit, the digital filter circuit There are two output terminals, and be connected respectively with the master controller and the time difference measurement circuit, the digital filter circuit is used After the pulse laser jet lag signal received and the echo pulse signal width signal are filtered processing The master controller is sent to, the time difference measurement circuit is filtered the digital filter circuit pulse after processing Laser flying time difference signal and the echo pulse signal width signal measure, and the data after measurement are sent to described Master controller, the main controller controls and the data for reading the time difference measurement circuit, and be modified according to the data and Compensation.
2. A kind of 2. echo cancellation system based on pulse type laser ranging according to claim 1, it is characterised in that：It is described High-pressure generating circuit produces the adjustable high pressure that voltage range is 100V-200V, its adjustable electric under control of the master controller Pressure resolution ratio is 0.5V.
3. A kind of 3. echo cancellation system based on pulse type laser ranging according to claim 2, it is characterised in that：It is described The measurement accuracy of time difference measurement circuit is 10ps, can measure pulse laser jet lag signal and echo pulse signal width at the same time Signal.
4. 4. a kind of echo cancellation system based on pulse type laser ranging according to claim 1-3 any one, it is special Sign is：The master controller is according to the temperature information that the temperature sensing circuit is transmitted to two pole of high speed avalanche photoelectricity When pipe carries out high pressure compensation, high pressure compensation is carried out using the following formula：

   Fn [Uapd]=Uc+Uk* { Tx } DEG C formula one

   M=Fn [Uapd] * K formulas two

   Wherein, Fn is unified representation mathematical function ordered series of numbers, and M is the gain that progress is influenced by temperature and high pressure, and Fn [Uapd] is The corresponding APD biass of Current Temperatures, Tx are current temperature value, and Uapd is the corresponding high-voltage value of Current Temperatures, and Uc is acquiescence APD high Pressure, Uk are the every once corresponding APD high pressures coefficient of environment temperature, and K is constant.
5. A kind of 5. echo cancellation system based on pulse type laser ranging according to claim 4, it is characterised in that：It is described After main controller controls and the data of the reading time difference measurement circuit, and it is modified and compensates according to the data, specifically, Echo pulse signal width is converted into by signal width distance value Stw according to the following formula：

   Stw=(Td-Tu) * C formulas three

   Wherein, Td is Laser emission trigger signal to return signal trailing edge moment, and Tu is Laser emission trigger signal to return Signal rising edge time, C is light velocity resolution ratio, and when echo pulse signal narrowed width, the Stw values calculated can also become therewith It is small, but range error will become larger, and therefore, the different corresponding range errors of Stw values is also different, these errors are surveyed in advance Go out and be stored in Fn { Stw } array, master controller is according to live signal width distance value and is stored in Fn (Stw) array Value is compared, its signal width distance value Stw is modified further according to corresponding echo pulse signal width, obtains width Correction value W, correction formula are：

   W=Fn { Stw } formula four

   Then, W=b-k*Stw formulas five

   Also, K=Fn { Stw [n+1] }-Fn { Stw [n] }, and (W >=0)；Formula six

   Wherein, b is the corresponding compensation width maximum of current echo pulse signal width, and K is current echo pulse signal width Corresponding penalty coefficient, Stw [n] are width error inquiry table, and n is the integer of current echo pulse signal width value, and Stw is to work as Preceding echo pulse signal width value；

   Since electric signal has delay phenomenon in hardware circuit transmitting procedure, so a delay time error just occurs, and this A error is fixed, so final measurement distance reduction formula is：

   D=C*Tu/2-Dt-W formulas seven

   D is revised measurement distance, and unit m, Dt are constant time lag error, and unit m, C are light velocity resolution ratio, and W is width Correction value is spent, unit m, Tu are Laser emission trigger signal to return signal rising edge time.