CN1183389C - Signal processing method and device for laser ranging - Google Patents

Abstract

A signal processing method and device for laser ranging includes the following steps: A. setting the number of measuring blocks and the laser emission times: B. starting from the first measurement block, sampling and counting the laser reflection signal in each block in sequence to find out the block where the target object is located; C. in the block where the target is located, laser light with a preset delay time is emitted, and the reflected laser signal is subjected to sampling operation processing, so that the distance between the laser range finder and the target is calculated more precisely.

Description

Signal processing method and device for laser ranging

technical field

The present invention is related to a laser range finder, and in particular provides a signal processing method and device for a laser range finder, which effectively improves the accuracy of the laser range finder without increasing the sampling period and sampling times. And save the memory required by the laser range finder.

Background technique

Laser range finder (Laser Range Finde) is one of the important devices for measuring distance. The conventional laser range finder uses a pulse (pulse) type laser transmitter to emit a laser pulse (laser pulse) of about 10ns-20ns onto a target. The laser signal reflected by the target is received by a laser receiver, and the distance is calculated by the following formula (1):

T _d ＝2L/C……………………………………(1)

Formula (1) where L represents the distance between the laser rangefinder and the target, C represents the speed of light, and T _d represents the delay time between the emitted laser pulse and the received laser pulse. The exact distance can be calculated by measuring T _d according to formula (1). In order to accurately measure T _d , it is necessary to increase the laser emission power as much as possible, or to eliminate the noise generated by sunlight and sunlight received by the laser receiver. US Patent No. 3,644,740 discloses a receiving circuit that obtains false alarms by controlling the circuit bias of the receiving circuit, thereby improving the signal-to-noise ratio of the receiving circuit. US Patent No. 4,569,599 discloses a counting control technology for detecting distance signals. US Patent No. 4,770,526 discloses a technology to increase the value of the distance detection result by amplifying the time-delayed signal. In addition, a digital distance measurement technology is also disclosed in US Patent No. 3,959,641, which is used to reduce the threshold voltage of the laser receiver to increase the measurement distance.

In order to cope with different situations, US Patent No. 5,612,779 discloses a design that can automatically adjust the threshold voltage (Threshold Voltage). In the previous proposal, the threshold voltage can be changed according to the intensity of the reflected signal of the target, so that a threshold voltage between the noise and the signal intensity of the target can still be set in different environments. The main effect of the above patent case is to increase the measurement distance and accuracy.

To improve the receiving ability and measurement accuracy of the laser range finder, the common method is to adopt high-speed sampling statistics and increase the sampling cycle and sampling frequency, so that the sampling time point is closer to the actual time of receiving the reflected laser signal point, more accurate distance data can be obtained by using the time data for calculation; however, this method has the following disadvantages:

1. During the sampling process, each reference point of the sampling must be recorded. Therefore, for the same distance measurement interval, the higher the sampling period, the larger the memory capacity must be set, and increasing the number of sampling times will also occupy a larger storage space, so A memory with a larger capacity is required, which also increases the manufacturing cost;

2. To increase the sampling cycle and sampling times, higher-speed components must be used, which cost more and consume more power.

Contents of the invention

The main purpose of the present invention is to provide a signal processing method and device for laser distance measurement, which can greatly improve the distance measurement accuracy in the same distance measurement interval without increasing the sampling period.

Another object of the present invention is to provide a signal processing method and device for laser distance measurement, which can divide a plurality of measurement intervals in the same distance measurement interval, so that the required memory capacity is greatly reduced, thereby saving costs.

The reason is, according to the signal processing method of a kind of laser ranging provided by the present invention, it is characterized in that, comprises the following steps:

A. Set the number of measurement blocks and the number of laser shots: divide the total sampling time T _T of laser ranging into several blocks, and set the total number of laser shots in each block;

B. Starting from the first measurement block, the laser reflection signal is sampled and counted in each block in order to find out which block the target is located in;

C. Emit laser light with a predetermined delay time T _k in the block where the target is located, and perform sampling and calculation processing on the reflected laser signal, so as to calculate the distance between the laser range finder and the target.

Wherein the detailed steps of step B are:

b1. Use the laser range finder to emit laser light for a predetermined number of times:

b2. In each emission event, the laser reflection signal is found by means of continuous sampling with a sampling period T _s ;

b3. Accumulate the laser reflection signals of each emission event to determine whether the target is located in the block.

Wherein the detailed steps of step C are:

c1. Emit laser light and sample the laser reflection signal;

c2. At least one laser light is emitted with a predetermined delay time T _k , and the laser reflection signal is obtained by sampling, wherein the time interval of T _k is less than the sampling period T _s ;

c3 obtains the distance between the target object and the laser rangefinder based on the laser reflection signals obtained from the above-mentioned emission events at different times.

Wherein in step C, the laser signal is transmitted with each delay period of Ts/4, and four different laser emission times of T _s , T _s /4, 3T _s /4 and T _s /2 can be obtained, By comparing the laser reflection signals of each emission event, the laser signal reflected by the target can be obtained, where T _s is the sampling period.

A laser ranging device of the present invention is characterized in that it comprises:

A timing interval generation circuit, used to generate a sampling period signal;

A microprocessor unit connected to the timing interval generation circuit;

A programmable delay unit, connected to the microprocessor unit and the timing interval generation circuit, can be controlled by the microprocessor unit to determine whether to send a delay control signal;

A laser emitting circuit, connected to the programmable delay unit, is controlled by the programmable delay unit to emit laser light;

A laser receiving circuit for receiving reflected laser signals;

A comparator circuit, connected to the laser receiving circuit, for comparing, amplifying and shaping the signals received by the laser receiving circuit;

A memory, connected to the microprocessor unit, is used for its calculation and statistics.

It also includes: a high-speed shift register, connected to the comparison circuit and the timing interval generating circuit, and used to quickly store the signal of the comparison circuit.

Description of drawings

Concerning the detailed structure of the present invention, feature and effect, give a preferred embodiment below hereby, and cooperate drawing to be further described, wherein:

Fig. 1 is a step diagram of a preferred embodiment of the present invention;

Fig. 2 is a schematic diagram of sampling of divided blocks in a preferred embodiment of the present invention;

Fig. 3 is a sampling illustration for the third block where the target object is located in a preferred embodiment of the present invention;

Fig. 4 is another sampling explanatory diagram of a preferred embodiment of the present invention, showing the sampling state after delaying T _s /4 time to emit laser light;

Fig. 5 is another sampling explanatory diagram of a preferred embodiment of the present invention, showing the sampling state after delaying T _s /2 time to emit laser light;

Fig. 6 is another sampling explanatory diagram of a preferred embodiment of the present invention, showing the sampling state after delaying 3T _s /4 time to emit laser light;

Fig. 7 is a flow chart of action about step B in a preferred embodiment of the present invention;

Fig. 8 is a flow chart of the action of step C in a preferred embodiment of the present invention;

FIG. 9 is a circuit block diagram of a preferred embodiment of the present invention.

Detailed ways

Referring to Fig. 1 to Fig. 6, a signal processing method of laser ranging provided by a preferred embodiment of the present invention includes the following steps:

A. Set the number of measurement blocks and the number of laser shots:

Divide the total sampling time T _T of laser ranging into four blocks, and set 10 laser light launches in each block;

B. As shown in Figure 2, starting from the first measurement block, the laser reflection signal is sampled and counted in each block in order to find out which block the target is located in. The following is in each block Detailed steps in:

b1. Use the laser transmitter to emit 10 times of laser light:

b2. In each emission event, the laser reflection signal is obtained by continuous sampling at the sampling period T _s , wherein the laser reflection signal may be the laser signal reflected by the target object, or it may be noise;

b3. Accumulate the obtained laser reflection signal into the memory according to its corresponding address;

In the 10 launch events in step B, since the noise hardly always appears in a fixed position, it can be judged whether the target is located in the block by statistics and correlation calculation;

C. In the block where the target object is located, emit laser light with a predetermined delay time, and perform calculation processing on the reflected laser signal, so as to judge the distance between the laser range finder and the target object. The detailed steps are:

c1, emit laser light, sample the laser reflection signal, and record it in the memory. Figure 3 is a timing diagram showing the emission of laser light 301, the received reflected laser signal 302, the signal 303 greater than the predetermined intensity, and the third area The sampling signal 304 of the block, and the corresponding position 305 of the distance signal stored in the memory after sampling;

c2. Delay T _s /4 time (that is, T _k ) to emit laser light, and sample the laser reflection signal. The obtained reflection signal is shown in Figure 4. In the figure, 403 represents the signal of the third block, and 404 represents The sampling signal of the third block, 405, represents the corresponding position of the distance signal stored in the memory after sampling; in this way, the laser light is repeatedly delayed by T _s /4 time (ie T _k ), and the signal location is obtained by statistics and correlation. storage location M10;

Then delay T _s /2 time (that is, 2T _k ) to emit laser light, and sample the laser reflection signal. The obtained reflection signal is shown in Figure 5: by statistics and correlation, the storage position M10 where the signal is located is obtained;

Then delay 3T _s /4 time (that is, 3T _k ) to emit laser light, and sample the laser reflection signal. The obtained reflection signal is shown in Figure 6; by statistics and correlation, the storage position M10 where the signal is located is obtained;

c3. Comparing 305, 405, 505, and 605 in Fig. 3 to Fig. 6, it can be concluded that the time difference of the distance signal in Fig. 3 is (B3+8) × T _s , while the time difference of the distance signal in Fig. 4 to Fig. 6 is (B3+9)×T _s , where B3 refers to the third block;

Then calculate the distance of the undelayed, delayed T _s /4 time, delayed T _s /2 time, and 3T _s /4 time signals according to the following formula 2:

L=(4×B3+8+9+9+9)×T _s /4×C/2-ΔL...(2)

Where B3 is the starting position of the third block; T _s is the sampling period; C is the speed of light; ΔL is the distance correction amount;

In this way, the distance L between the target object and the laser range finder can be calculated.

Fig. 7 is the execution workflow of step B of the present invention, wherein, 704 refers to setting the number of launches to 10 times, and 708-712 refers to comparing the accumulated value with the maximum value to determine whether the target is located in the block .

Fig. 8 is the execution workflow of the present invention about step C, wherein. 802 refers to setting the delay time, 803 refers to setting the number of shots, 809 refers to judging where the target is located in the block, and 811 refers to calculating the distance of the target according to formula (2).

Please refer to Fig. 9 again, it is a kind of laser ranging device 900, which is the practical application of the method provided by the present invention. The laser ranging device 900 is mainly composed of a timing interval generation circuit 913, a microprocessor unit 911, a Programmable delay unit 912, a laser emitting circuit 903, a laser receiving circuit 904, a comparison circuit 905, and a memory 915, wherein:

The timing interval generation circuit 913 is used to generate a system timing measurement interval and a signal with a pulse sampling period T _s , and the system pulse in this embodiment is the sampling period T _s ;

The programmable delay unit 912 is connected to the microprocessor unit 911, and is controlled by the microprocessor unit 911 to determine whether to send a delay control signal and a delay time;

The laser emitting circuit 903 is connected to the programmable delay unit 912, and is controlled by the programmable delay unit 912 to emit a preset delayed laser light;

The laser receiving circuit 904 is used to receive reflected laser signals;

The comparison circuit 905 is connected to the laser receiving circuit 904, and is used to compare the signal received by the laser receiving circuit 904, and to amplify and shape it;

A high-speed shift register 914, connected to the comparison circuit 905 and the timing interval generation circuit 913, for quickly storing the signal of the comparison circuit;

The memory 915 is connected to the microprocessor unit 911 and the high-speed shift register 914, and the microprocessor unit 911 can calculate and accumulate the internal data of the high-speed shift register 914 and store them in the memory 915 ;

Thus, during operation, the microprocessor unit 911 controls the laser emitting circuit 903 to emit laser light on the target, and then receives the laser signal and noise signal reflected by the target through the laser receiving circuit 904 , and then through the comparator circuit 905, the signal that is greater than the predetermined strength is reshaped as shown in 303 in Figure 3, TN1-6 is noise in the figure, and TS is the target signal; then sample with the sampling period T _s , and read the high-speed shift In the temporary register 914, and accumulate in this memory 915 sequentially, its content is as shown in 305 of Fig. 3: when need delay, this microprocessor unit is to set the delay time of this delay unit to be T respectively _s /4, T _s /2, and 3T _s /4, so as to control the transmitter to delay the emission of laser light for a predetermined time, so that a time difference is generated in the received distance signal, and a more accurate distance can be calculated by the above method.

As can be seen from the above, the advantages of the present invention are:

One, saving memory cost: because the present invention divides the total sampling time into several blocks, the required memory space is less than half of that of the conventional user, that is, the memory required by the present invention is less than that of the conventional user. The cost is also relatively low.

2. Improve the accuracy without increasing the cost: the present invention obtains the time difference of the distance signal by delaying the emission of laser light, and then obtains a more accurate target distance. To achieve the purpose of improving the accuracy, but to use the existing components, cleverly obtain the time difference by delaying the transmission, and then obtain a more accurate distance value through calculation, so the present invention improves the distance measurement without increasing the cost. Accuracy, with a clear gain in efficacy.

To sum up, the signal processing method and device for laser distance measurement of the present invention have the above-mentioned advantages over those who use it, and its practicability and progress are beyond doubt. In addition, it has never been publicly used or disclosed. Based on various documents and materials, the present case should already have all the requirements for a patent for invention.

Claims (6)

1. A signal processing method for laser ranging, characterized in that, comprising the following steps: A. Set the number of measurement blocks and the number of laser shots: divide the total sampling time T _T of laser ranging into several blocks, and set the total number of laser shots in each block; B. Starting from the first measurement block, the laser reflection signal is sampled and counted in each block in order to find out which block the target is located in; C. Emit laser light with a predetermined delay time T _k in the block where the target is located, and perform sampling and calculation processing on the reflected laser signal, so as to calculate the distance between the laser range finder and the target. 2. The signal processing method of laser ranging according to claim 1, wherein the detailed steps of step B are: b1. Use the laser range finder to emit laser light for a predetermined number of times: b2. In each emission event, the laser reflection signal is found by means of continuous sampling with a sampling period T _s ; b3. Accumulate the laser reflection signals of each emission event to determine whether the target is located in the block. 3. the signal processing method of laser ranging according to claim 1, is characterized in that, wherein the detailed steps of step C are: c1. Emit laser light and sample the laser reflection signal; c2. At least one laser light is emitted with a predetermined delay time T _k , and the laser reflection signal is obtained by sampling, wherein the time interval of T _k is less than the sampling period T _s ; c3 obtains the distance between the target object and the laser rangefinder based on the laser reflection signals obtained from the above-mentioned emission events at different times. 4. The signal processing method of laser ranging according to claim 1, wherein in step C, the laser signal is emitted with a period of each delay T _s /4, and T _s can be obtained, T _s /4, 3T _s /4, T _s /2 four different laser emission times, compare the laser reflection signals of each emission event, and the laser signal reflected by the target can be obtained, where T _s is the sampling period. 5. A laser distance measuring device, characterized in that it comprises: A timing interval generation circuit, used to generate a sampling period signal; A microprocessor unit connected to the timing interval generation circuit; A programmable delay unit, connected to the microprocessor unit and the timing interval generation circuit, can be controlled by the microprocessor unit to determine whether to send a delay control signal; A laser emitting circuit, connected to the programmable delay unit, is controlled by the programmable delay unit to emit laser light; A laser receiving circuit for receiving reflected laser signals; A comparator circuit, connected to the laser receiving circuit, for comparing, amplifying and shaping the signals received by the laser receiving circuit; A memory, connected to the microprocessor unit, is used for its calculation and statistics. 6. A kind of laser ranging device according to claim 5, characterized in that it also includes: a high-speed shift register connected to the comparison circuit and the timing interval generation circuit for quickly storing the Comparing the signal of the circuit.

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