CN115113224A

CN115113224A - Telescope range finder and range finding method based on same

Info

Publication number: CN115113224A
Application number: CN202210789253.6A
Authority: CN
Inventors: 罗印龙; 张佳一; 马凌超
Original assignee: Hangzhou Ruimeng Technology Co ltd
Current assignee: Hangzhou Ruimeng Technology Co ltd
Priority date: 2022-07-06
Filing date: 2022-07-06
Publication date: 2022-09-27

Abstract

The application discloses telescope distancer and range finding method based on telescope distancer is applied to range finding technical field, includes: after receiving the ranging instruction, controlling a signal transmitting circuit to transmit N optical pulses to a target position; judging whether the frequency of echo pulses received by a TDC in a signal receiving circuit is greater than K; if the reference voltage value is larger than K, setting the reference voltage value of a comparator in the signal receiving circuit to be a first value, and controlling the signal transmitting circuit to transmit A optical pulses to the target position; otherwise, setting the reference voltage value of the comparator as a second value, and controlling the signal transmitting circuit to transmit B optical pulses to the target position; after the TDC converts each received echo pulse into a corresponding distance value, the distance value with the highest frequency of occurrence is output as the distance of the determined target position. By the scheme, distance measurement can be performed based on the telescope range finder, and the distance measurement precision, the distance measurement distance and the convenience of distance measurement are improved.

Description

Telescope range finder and range finding method based on same

Technical Field

The invention relates to the technical field of distance measurement, in particular to a telescope range finder and a distance measurement method based on the telescope range finder.

Background

With the development of electronic technology, the laser ranging technology is combined with the traditional optical telescope, so that the visible target distance can be obtained. At present, there are three methods for implementing an infrared telescope range finder, 1 is a scheme of a comparator + CPLD (Complex Programmable Logic Device)/FPGA (Field Programmable Gate Array), 2 is a scheme of an ADC (Analog to Digital Converter) + FPGA, and 3 is a scheme of a comparator + TDC (Time-to-Digital Converter).

Although the former 2 methods have multi-pulse capture capability, the maximum operation clock of the CPLD/FPGA is only about 300MHz, the corresponding ranging accuracy is about 0.5m, and the ADC sampling speed is also limited (80-150 MSPS), so that the ranging accuracy of the former 2 methods is low.

A third solution is to make a time measurement of the echo pulses directly with the TDC, with a very high accuracy (in the order of centimetres). The existing TDC also has the capturing capability of 3-4 pulses, but the pulse number of the set echo must be consistent with the set target number when the existing TDC is used, and the captured pulse is effective. For example, if the number of echo pulses is set to 4 and only 3 pulses are captured during this measurement, the 3-pulse measurement results captured at this time are considered invalid, which limits the range-finding capability of the telescope range finder. In outdoor ranging, background light and a measured target are uncertain, and the condition and the number of echo pulses in each measurement process cannot be estimated, so that the multi-target capturing capability of the TDC cannot be exerted.

Therefore, in the case of the comparator + TDC method, although the accuracy of the distance measurement is high, the number of echo pulses is required to be equal to the number of set targets, and the number and the condition of the echo pulses are not constant in the distance measurement in the outdoor environment, so that the number of echoes can be set to 1 time in the application of the TDC. Thus, it is necessary that the signal-to-noise ratio of the echo is high, i.e. the threshold of the comparator is set high enough that only when the true target echo signal is large enough, the true target echo signal can pass the threshold of the comparator and be captured by the subsequent TDC, which limits the ranging distance to a large extent. Because the farther the distance measurement is needed, the lower the echo pulse energy cannot effectively cross the high threshold of the comparator, and if the transmission energy is increased when a single pulse is transmitted, the telescope distance measurement transmission power is beyond safety standards, namely, the telescope distance measurement transmission power is not in accordance with safety regulations.

The current infrared telescope range finder usually obtains the target distance by averaging through multiple distance measurement because the number of loops is set to 1 time, and when measuring long distance and small targets, the telescope range finder is generally in handheld measurement, and the stability of the telescope range finder cannot be ensured, so that in the key measurement process, the shaking and shaking of hands can cause pulse deviation from the targets, and at the moment, an average algorithm of multiple measurement is adopted, and the obtained distance can be an intermediate distance value of a front target and a rear target, and is not a real target distance.

In addition, when the scheme of the current TDC chip is used, a single measurement mode can only measure a distance of 0 to 200 meters, which is greater than 200 meters, and the mode needs to be switched, i.e., the target cannot be switched conveniently and quickly for measurement.

In summary, how to effectively measure distance based on a telescope range finder, improve the accuracy of distance measurement, the distance measurement distance, and the convenience of distance measurement is a technical problem which needs to be solved urgently by technical personnel in the field at present.

Disclosure of Invention

The invention aims to provide a telescope range finder and a range finding method based on the telescope range finder, so as to effectively carry out range finding based on the telescope range finder and improve the range finding precision, the range finding distance and the convenience of range finding.

In order to solve the technical problems, the invention provides the following technical scheme:

a distance measuring method based on a telescopic range finder comprises the following steps:

after receiving the ranging instruction, controlling a signal transmitting circuit to transmit N optical pulses to a target position;

judging whether the frequency of echo pulses received by a TDC in a signal receiving circuit is greater than K;

if the reference voltage value is larger than K, setting the reference voltage value of a comparator in the signal receiving circuit to be a first value, and controlling the signal transmitting circuit to transmit A optical pulses to the target position;

if the reference voltage value is not greater than K, setting the reference voltage value of the comparator to be a second value, and controlling the signal transmitting circuit to transmit B optical pulses to the target position;

after the TDC converts each received echo pulse into a corresponding distance value, taking the distance value with the highest occurrence frequency as the determined distance of the target position;

outputting the determined distance of the target position;

the first numerical value is larger than the second numerical value, N, A and B are preset positive integers not smaller than 2, K is a preset positive integer, and K is smaller than N.

Preferably, when it is determined that the number of times of the echo pulse received by the TDC in the signal receiving circuit is greater than K, the determining, by the TDC, a distance value with the highest frequency of occurrence as the distance of the determined target position after converting each received echo pulse into a corresponding distance value includes:

for any 1 echo pulse output by the comparator, detecting the rising edge of the echo pulse through a first channel of the TDC and converting the rising edge into a corresponding distance value, and detecting the falling edge of the echo pulse through a second channel of the TDC and converting the falling edge into a corresponding distance value;

taking the smaller value of the 2 distance values with the highest occurrence frequency as the distance to be compensated, and taking the difference value of the 2 distance values with the highest occurrence frequency as the pulse width;

and determining a corresponding error correction value according to the pulse width, correcting the distance to be compensated based on the error correction value, and taking an obtained correction result as the determined distance of the target position.

Preferably, the controlling the signal transmitting circuit to transmit B light pulses to the target location includes:

the signal transmitting circuit is controlled to transmit B optical pulses to the target position, and each signal receiving channel of the TDC is controlled to be enabled after being delayed for a first time period relative to a start signal of the optical pulse when each 1 of the B optical pulses is transmitted.

Preferably, after receiving the ranging command, the method further includes:

and performing the self-calibration of the gate delay of the TDC through an external crystal oscillator of the TDC.

Preferably, the method further comprises the following steps:

and after receiving a first channel selection instruction, controlling the TDC to be in a multi-channel parallel working state, and after receiving a second channel selection instruction, controlling the TDC to be in a multi-channel serial working state.

Preferably, after the TDC converts each received echo pulse into a corresponding distance value, the method further includes:

and outputting each distance value with the occurrence frequency higher than the first frequency threshold value.

A telescopic rangefinder comprising:

the device comprises a prism, an emitting lens, a receiving and condensing lens, a signal emitting circuit, a signal receiving circuit and an output circuit;

an input circuit: the controller is used for sending a ranging instruction to the controller;

the controller is configured to:

outputting the determined distance of the target position to the output circuit;

the first numerical value is larger than the second numerical value, N, A and B are preset positive integers not smaller than 2, K is a preset positive integer and K is smaller than N.

Preferably, the signal transmission circuit includes:

a pulsed laser diode for emitting a pulse of light to the prism upon excitation;

a transmitting high-voltage circuit connected with the pulse laser diode and used for providing electric energy for the pulse laser diode;

and the switching circuit is connected with the pulse laser diode and is used for controlling the excitation state of the pulse laser diode under the control of the controller.

Preferably, the switching circuit includes: the first switch tube, the first capacitor and the drive circuit;

the control end of the first switch tube is connected with the controller through the driving circuit, the first end of the first switch tube is respectively connected with the first end of the first capacitor and the output end of the transmitting high-voltage circuit, and the second end of the first switch tube is grounded;

the second end of the first capacitor is connected with the cathode of the pulse laser diode, and the anode of the pulse laser diode is grounded.

Preferably, the method further comprises the following steps: a second capacitor and a first resistor;

the first end of the second capacitor is connected with the cathode of the pulse laser diode, the second end of the second capacitor is connected with the first end of the first resistor, and the controller takes the second end of the first resistor as a starting signal end of the optical pulse to be connected with the TDC, so that the TDC receives a starting signal of the optical pulse through the starting signal end.

Preferably, the signal receiving circuit includes:

an avalanche photodiode having an anode grounded for generating a current upon receiving an optical signal;

a reverse bias circuit connected to a cathode of the avalanche photodiode;

a third capacitor having a first end connected to the cathode of the avalanche photodiode and a first end connected to the transimpedance amplifier;

the transimpedance amplifier;

the voltage amplifier is connected with the transimpedance amplifier;

the first input end is used for receiving a reference voltage value, and the second input end is used for a comparator connected with the voltage amplifier;

and the TDC is connected with the output end of the comparator.

By applying the technical scheme provided by the embodiment of the invention, the distance can be automatically distinguished without mode switching, and then the controller can set the reference voltage value of the comparator and control the signal transmitting circuit to transmit a corresponding number of optical pulses to the target position, so that the scheme of the application realizes the convenience of distance measurement and can conveniently and quickly switch the target to measure. In addition, the signal receiving circuit adopts a mode of a comparator and a TDC and has high ranging precision.

After the controller receives the ranging instruction, the signal transmitting circuit can be controlled to transmit N optical pulses to the target position. Specifically, if the number of times of echo pulse is greater than K, it explains that the range finding is close range, this application can set up the reference voltage value of the comparator in the signal receiving circuit to higher numerical value, first numerical value promptly, and then control signal transmitting circuit to launch A light pulse to the target location, otherwise, the number of times of echo pulse is not more than K, it explains that the range finding is long range, this application can set up the reference voltage value of the comparator in the signal receiving circuit to less second numerical value, and then control signal transmitting circuit to launch B light pulse to the target location. Since the reference voltage value of the comparator is high during the short-distance ranging, the influence of interference is favorably reduced because noise is not easy to pass through the comparator with a high threshold. And when long-distance measuring, the reference voltage value of the comparator is lower, so that the distance measuring distance of the application is favorably improved, namely, when long-distance measuring is carried out, even if the energy of the echo pulse is lower, a lower threshold of the comparator can be crossed.

After each received echo pulse is converted into a corresponding distance value by the TDC, the distance value with the highest occurrence frequency is used as the distance of the determined target position, namely, the distance value with the highest occurrence frequency is obtained in a statistical mode instead of the distance of the target position obtained in an average value calculating mode, so that the method is beneficial to avoiding errors caused by hand shaking, interference and other factors, and can obtain the accurate distance of the target position.

To sum up, the scheme of this application can be based on telescope distancer effectively and range finding has improved range finding precision, range finding distance to and the convenience of range finding.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a flow chart of a distance measuring method based on a telescopic distance measuring instrument according to the present invention;

FIG. 2a is a histogram of distance statistics during long-distance ranging according to an embodiment of the present invention;

FIG. 2b is a histogram of distance statistics during short-range distance measurement according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a telescopic rangefinder in accordance with one embodiment of the present invention;

FIG. 4a is a schematic diagram of a transmitting high voltage circuit according to an embodiment of the present invention;

FIG. 4b is a schematic diagram of a switch circuit according to an embodiment of the present invention;

FIG. 4c is a schematic diagram of a switch circuit according to another embodiment of the present invention;

FIG. 5a is a schematic diagram of a partial structure of a signal receiving circuit according to an embodiment of the present invention;

FIG. 5b is a schematic diagram of a comparator according to an embodiment of the present invention;

FIG. 5c is a schematic diagram of a comparator according to another embodiment of the present invention;

fig. 6 is a schematic diagram of a chip structure of an MS1003 according to another embodiment of the present invention;

fig. 7 is a schematic diagram of the absolute error caused by the echo intensity.

Detailed Description

The core of the invention is to provide a ranging method based on a telescope range finder, which can effectively carry out ranging based on the telescope range finder and improve the ranging precision, the ranging distance and the ranging convenience.

In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.

Referring to fig. 1, fig. 1 is a flowchart illustrating an implementation of a distance measuring method based on a telescopic range finder according to the present invention, where the distance measuring method based on the telescopic range finder includes the following steps:

step S101: and after receiving the ranging instruction, controlling the signal transmitting circuit to transmit N optical pulses to the target position.

Specifically, referring to fig. 3, a user may operate the input circuit 50, thereby causing the input circuit 50 to send a ranging command to the controller 70. The specific structure of the input circuit 50 can be set and adjusted according to actual needs, for example, a key or a button type input circuit 50 is adopted, which is convenient for a user to operate, and for example, a touch screen type input circuit 50 can be adopted, which does not affect the implementation of the present invention.

The controller 70 receives the ranging command, which indicates that the user needs to perform ranging, and the controller 70 may control the signal transmitting circuit to transmit N light pulses to the target position to determine whether the target position to be measured is a short distance or a long distance.

N is a preset positive integer not less than 2, and the specific value can be set and adjusted as required, for example, N is set to 10 in one case.

In addition, in practical application, when the telescope range finder is started, initialization after power-on can be performed. For example, in a specific situation, after the telescope range finder is powered on, the power supply portion is started, and the controller 70 is powered on, and then the controller 70 may first configure the system clock inside and the attributes of each input/output port, and set the voltages of the transmission high voltage circuit 11 in the signal transmission circuit and the reverse bias circuit 31 in the signal reception circuit. Next, the controller 70 may reset and register the TDC chip, for example, in a specific case, the TDC chip selects the MS1003, the controller 70 may send a negative pulse greater than 10 microseconds to the RSTN pin of the MS1003 through the port to perform hardware reset, and then write a 0x50 command through a Serial Peripheral Interface (SPI) port to perform software reset. After the reset is completed, the 32-bit configuration register is written to the MS1003 through the SPI, the configuration register operation command is 0x80, and the 32-bit data is written sequentially with the upper bit in front and the lower bit in back. The initialization operation can be performed once after power-on, and no operation is needed later.

The specific configuration of the signal transmitting circuit may be set as needed, and the light pulse may be efficiently transmitted to the target position under the control of the controller 70.

Step S102: judging whether the frequency of echo pulses received by a TDC in a signal receiving circuit is greater than K; if greater than K, step S103 is performed, and if not greater than K, step S104 is performed.

After controlling the signal transmitting circuit to transmit N optical pulses to the target position, in an ideal case, N echo pulses may be received, but due to interference, different target position distances, and the like, the number of times of echo pulses received by the TDC35 in the signal receiving circuit is not necessarily equal to N.

The present application considers that the lower the energy of the echo pulse as the distance of the target position is, the fewer the number of times the echo pulse is received by the TDC35, and therefore, the controller 70 may determine whether or not the number of times the echo pulse is received by the TDC35 in the signal receiving circuit is greater than K. K is a predetermined positive integer and is less than N, for example, N is set to 10 and K is set to 8 in one case.

When the number of times of the echo pulses received by the TDC35 is greater than K, it indicates that the target position is closer, and therefore step S103 may be performed, otherwise, it indicates that the target position is farther, and therefore step S104 may be performed.

It should be noted that, when step S101 and step S102 are executed, the reference voltage value of the comparator 34 in the signal receiving circuit may be set to a higher first value, so that the echo signal with lower strength and the interference cannot cross the threshold of the comparator 34.

Step S103: and setting the reference voltage value of a comparator in the signal receiving circuit to be a first value, and controlling the signal transmitting circuit to transmit A optical pulses to the target position.

Step S104: and setting the reference voltage value of the comparator to be a second value, and controlling the signal transmitting circuit to transmit B optical pulses to the target position.

When the number of times of the echo pulse received by the TDC35 is greater than K, it indicates that the target position is closer, and therefore, the reference voltage value of the comparator 34 in the signal receiving circuit is set to the first value, so that only a stronger echo signal can cross the threshold of the comparator 34, thereby effectively reducing the interference. Further, when the target position is close, the TDC35 has a low probability of receiving an echo pulse due to interference, and therefore the value of a may be set to be small, for example, a is set to 100, that is, the controller 70 controls the signal transmitting circuit to transmit 100 optical pulses to the target position.

When the number of times of the echo pulse received by the TDC35 is not greater than K, it indicates that the target position is farther away, so the reference voltage value of the comparator 34 in the signal receiving circuit is set to a lower second value, so that even if the echo signal is weaker, the threshold of the comparator 34 can be crossed, effectively increasing the measurement distance. Of course, when the reference voltage value of the comparator 34 is set to a second lower value, noise will also easily cross the threshold of the comparator 34, and thus the pulses output by the comparator 34 are scrambled because the noise appears randomly, and the echo signal at the target location appears only near the target distance. According to the method, the occurrence frequency of different distances is counted, noise and signals belong to random variables in the telescope range finder, and according to a statistical theory, the distribution of independent random variables is converged to normal distribution, so that the distance value with the highest occurrence frequency can be used as the distance of the determined target position.

Since the target position is far away, the noise will easily cross the threshold of the comparator 34, and therefore the value of B can be set to be large, for example, a is set to 500. Certainly, a and B are both preset positive integers not less than 2, and the larger the values of a and B are, i.e. the more the number of measurements is, the more the obtained result has statistical significance, but in practical application, a balance needs to be obtained between the number of measurements and the measurement time, so according to experimental data and theoretical analysis, a and B in the above embodiment may be set to 100 and 500, respectively.

Step S105: after the TDC converts each received echo pulse into a corresponding distance value, the distance value with the highest frequency of occurrence is taken as the distance of the determined target position.

Taking the example where the controller 70 controls the signal transmitting circuit to transmit 100 light pulses to the target location, the TDC35 may receive 0 or several echo pulses after transmitting every 1 light pulse, and ideally, the TDC35 should receive 1 echo pulse after transmitting every 1 light pulse.

For theAny 1 echo pulse according to D ═ DeltaT ═ C ₀ And/2, the echo pulse can be converted into a corresponding distance value. Where Δ T represents the elapsed time between the transmission of 1 light pulse and the reception of the echo pulse, which may be calculated by TDC35, C ₀ For the speed of light, D is the distance value corresponding to the echo pulse, and the distance is taken as the abscissa, and the frequency of occurrence of the distance is taken as the ordinate, so that the distance frequency in the whole distance range can be obtained, for example, in fig. 2a, the peak point of the histogram is the position where the distance frequency is the highest, and the abscissa, that is, the distance value with the highest frequency of occurrence, is taken as the distance of the determined target position.

Step S106: outputting the determined distance of the target position;

the output may be performed after the distance to the target location is determined, for example, in one embodiment the output circuit 60 includes an LCD driver coupled to the controller 70 and a transmissive LCD display coupled to the LCD driver through which the user can view the distance to the target location displayed.

The specific structure of the telescope distancer of this application can set for as required, can include for example: a prism 21, a transmitting lens 22, a receiving condenser lens 40, a signal transmitting circuit, a signal receiving circuit, an output circuit 60, an input circuit 50, and a controller 70. The specific structure of each part may also be set as required, for example, in an embodiment of the present invention, referring to fig. 3, the signal transmitting circuit may specifically include:

a pulse laser diode PLD for emitting a pulse of light to the prism 21 upon excitation;

a transmission high-voltage circuit 11 connected to the pulse laser diode PLD for supplying electric power to the pulse laser diode PLD;

a switching circuit 12 connected to the pulsed laser diode PLD for controlling the excitation state of the pulsed laser diode PLD under the control of the controller 70.

Specifically, the transmission high-voltage circuit 11 supplies electric power to the pulse laser diode PLD, that is, generates a high voltage required for the pulse laser diode PLD. For example, in practical applications, the high voltage circuit 11 generates a high voltage of 50 to 100V. Also, the control of the output voltage of the transmitting high-voltage circuit 11 may be performed by the controller 70. For example, fig. 4a is a schematic structural diagram of the transmitting high-voltage circuit 11 in an embodiment, the transmitting high-voltage circuit 11 in fig. 4a can boost the input low voltage of 3.3V/5V to the high voltage of 50 to 100V required for the pulse laser diode PLD to transmit, and TXHV in fig. 4a represents the high voltage output by the transmitting high-voltage circuit 11. Considering that the voltage is high, the voltage divider network is formed by two resistors in fig. 4a, so that the controller 70 can perform voltage acquisition at the sampling end in fig. 4a through the ADC, that is, can calculate the current output voltage of the transmitting high-voltage circuit 11, and further the controller 70 can adjust the duty ratio of the PWM1 in fig. 4a, thereby performing feedback control on the high voltage output by the transmitting high-voltage circuit 11, and stabilizing the high voltage output by the transmitting high-voltage circuit 11 to the preset value of the controller 70. In addition, in fig. 4a, a voltage stabilizing capacitor is arranged at the input end of the transmitting high-voltage circuit 11, an RC filter circuit is arranged at the output end, and the diode in fig. 4a adopts a design of connecting 2 diodes in series, so that the reverse breakdown voltage can be increased, and of course, in fig. 4a, a single diode or 2 diodes can be selected to be used in series as required.

It should be noted that, for the reverse bias voltage required for the avalanche photodiode APD in the following embodiments, the same or different circuit structure may be adopted, that is, the structure of the reverse bias circuit 31 may refer to the design of fig. 4a, and thus, the description thereof is omitted.

The specific type of the Pulsed Laser Diode PLD of the present application may also be selected according to needs, for example, may be specifically selected as an infrared PLD (Pulsed Laser Diode).

When the transmitting high-voltage circuit 11 is connected to the pulsed laser diode PLD, it may be connected to the anode, and then the conducting loop of the switching circuit 12 is connected to the cathode of the pulsed laser diode PLD, such connection is simple, and when the controller 70 controls the switching circuit 12 to conduct, the high voltage output by the transmitting high-voltage circuit 11 flows from the anode of the pulsed laser diode PLD into the pulsed laser diode PLD, then sequentially passes through the cathode of the pulsed laser diode PLD and the switching circuit 12, and finally reaches the ground.

In a specific embodiment of the present invention, the connection between the transmitting high-voltage circuit 11 and the cathode of the pulse laser diode PLD is used to narrow the pulse width, so that a higher pulse amplitude is obtained within an energy allowable range, i.e., the quality of the optical pulse transmitted by the signal transmitting circuit is improved.

Specifically, referring to fig. 4b, the switch circuit 12 may specifically include: a first switch tube Q1, a first capacitor C1, and a driving circuit 121;

the control end of the first switch tube Q1 is connected with the controller 70 through the driving circuit 121, the first end of the first switch tube Q1 is respectively connected with the first end of the first capacitor C1 and the output end of the transmitting high-voltage circuit 11, and the second end of the first switch tube Q1 is grounded;

the second terminal of the first capacitor C1 is connected to the cathode of the pulsed laser diode PLD, and the anode of the pulsed laser diode PLD is grounded.

In fig. 4b, the high voltage output by the transmitting high-voltage circuit 11 is TXHV, the controller 70 may transmit a pulse trigger signal to the driving circuit 121, the first switching tube Q1 may be a MOS tube, for example, a MOS tube, and after the controller 70 transmits a pulse trigger signal, the driving circuit 121 may provide a larger pulse pull/sink current to the MOS tube, so that the gate of the MOS tube may be charged quickly, the gate of the MOS tube has a high ramp rate, and then the MOS tube may be turned on quickly.

On the other hand, when the MOS transistor is turned off, TXHV charges the first capacitor C1 to store charge, and at the moment when the MOS transistor is turned on, the charge stored in the first capacitor C1 is rapidly discharged. The voltage on the left plate of the first capacitor C1 in fig. 4b is pulled down instantaneously, triggering the pulsed laser diode PLD on the right of the first capacitor C1 to flow a large instantaneous current, and further causing the pulsed laser diode PLD to emit laser light, for example, infrared laser light. The laser emitted by the pulse laser diode PLD is coupled to the emission light path through the prism 21, is focused and collimated by the emission lens 22, and is emitted to the aimed target position.

Fig. 4c is a schematic structural diagram of the switching circuit 12 in another embodiment, the first switching tube Q1 can be implemented by a chip, and the pulse trigger signal transmitted by the controller 70 to the driving circuit 121 is labeled as Triger in fig. 4 c. The first capacitor C1 is implemented by two capacitors C11 and C12 connected in parallel. In addition, in fig. 4C, a voltage stabilizing capacitor and a current limiting resistor are further disposed between TXHV and the first capacitor C1 to ensure the reliability of the circuit, and a resistor and a diode are further disposed in parallel with the pulsed laser diode PLD to perform overcurrent protection on the pulsed laser diode PLD.

Further, in an embodiment of the present invention, the method further includes: a second capacitor C2 and a first resistor R1; the first terminal of the second capacitor C2 is connected to the cathode of the pulsed laser diode PLD, the second terminal of the second capacitor C2 is connected to the first terminal of the first resistor R1, and the controller 70 uses the second terminal of the first resistor R1 as the start signal terminal of the optical pulse to connect to the TDC35, so that the TDC35 receives the start signal of the optical pulse through the start signal terminal.

It will be appreciated that the concept of the present application requires a TDC35 in terms of D ═ Δ T × C ₀ The distance value corresponding to each echo pulse is calculated, and therefore, after the controller 70 controls the signal transmission circuit to transmit any 1 optical pulse to the target position, the controller needs to notify the TDC35 of the message so that the TDC35 starts timing, that is, the TDC35 needs to receive the start signal of the optical pulse. For example, for the embodiment of fig. 4c, after the controller 70 transmits a pulse trigger signal Triger to the driving circuit 121, the Triger may be simultaneously transmitted to the TDC35, so that the TDC35 receives the start signal of the optical pulse.

In this embodiment, it is considered that there is a delay in the circuit from the time when the controller 70 emits the pulse trigger signal to the time when the pulse laser diode PLD emits the laser light, thereby reducing the accuracy of the distance value calculated by the TDC 35. Therefore, in this embodiment, the second capacitor C2 and the first resistor R1 are connected to the cathode of the pulsed laser diode PLD, the second terminal of the first resistor R1 serves as the start signal terminal of the optical pulse to connect to the TDC35, and the second terminal of the first resistor R1 is labeled as FB Triger in fig. 4C for connecting to the TDC35, so that the TDC35 uses the signal here as the start signal of the optical pulse, thereby avoiding the influence of delay on the circuit and not reducing the accuracy of the distance value calculated by the TDC 35.

In an embodiment of the present invention, referring to fig. 3, the signal receiving circuit may include:

an Avalanche Photodiode (APD) having an anode grounded and configured to generate a current when receiving an optical signal;

a reverse bias circuit 31 connected to a cathode of the avalanche photodiode APD;

a third capacitor C3 having a first terminal connected to the cathode of the avalanche photodiode APD and a first terminal connected to the transimpedance amplifier 32;

a transimpedance amplifier 32;

a voltage amplifier 33 connected to the transimpedance amplifier 32;

a first input for receiving a reference voltage value and a second input for a comparator 34 connected to a voltage amplifier 33;

TDC35 connected to the output of comparator 34.

Specifically, after a narrow pulse (10-20 nanoseconds) generated by a signal transmitting circuit is projected to a measured object, a part of the pulse can be reflected to the telescope range finder through diffuse reflection of a target object. In this case, the target to be measured can be regarded as a secondary emission source for emitting energy to the three-dimensional space, and the energy received by the telescopic range finder depends on the area occupied by the receiving condenser lens 40 on a spherical cap with the radius of the distance from the target position. So for a telescopic rangefinder, very weak laser light is received. The energy that the telescope range finder can receive is inversely proportional to the square of the distance of the target position and proportional to the area of the receiving condenser lens 40, the receiving condenser lens 40 focuses the energy of the whole surface to one point, the avalanche photodiode APD needs to be focused on the focal plane of the receiving condenser lens 40 in advance, and focusing can be performed through an optical instrument, so that the focused energy of the receiving condenser lens 40 falls in the photosensitive surface area of the avalanche photodiode APD, and the size of the photosensitive surface is 230-500 micrometers generally.

Under the condition that a relatively high directional bias is applied by the reverse bias circuit 31, the avalanche photodiode APD can quickly convert an optical signal input to the photosensitive surface thereof into a current signal for output, and the gain of the avalanche photodiode APD and the reverse bias at the two ends thereof are in a nonlinear forward relationship, and generally can be set to about 100, but certainly can not be adjusted as required in different occasions.

In the embodiment of fig. 5a, RXHV represents the high voltage output by the reverse bias circuit 31. The current signal output by the avalanche photodiode APD needs to be transmitted to the input terminal of the transimpedance amplifier 32 through the third capacitor C3, the transimpedance amplifier 32 converts the current signal into a voltage signal and outputs the voltage signal, and the transimpedance amplifier 32 may be specifically selected from models such as MS8257, OPA857, and the like. In this embodiment, the third capacitor C3 is used for ac coupling, so that the input of the backlight can be limited to the greatest extent, because the backlight is mostly a dc component, the third capacitor C3 is used for ac coupling, so that only the pulse signal for distance measurement can pass through, and the dc component generated by the backlight is blocked, thereby improving the signal-to-noise ratio.

The echo signal output by the transimpedance amplifier 32 is not yet sufficiently large, and therefore, in this embodiment, the voltage amplifier 33 connected to the transimpedance amplifier 32 is provided, for example, the operational amplifier in the voltage amplifier 33 may be a high-speed high-bandwidth operational amplifier, such as MS8052, SGM8052, or the like. In the embodiment of fig. 5a, a 2-stage voltage amplifier 33 is provided, and sig indicates the output of the voltage amplifier 33. The voltage signal amplified by the voltage amplifier 33 is large enough to be supplied to the comparator 34 for processing.

The comparator 34 of the present application is equivalent to a 1-bit ADC, and can output a quantized value of 0 or 1, and a high-speed comparator 34 can be used. The level signal to be compared is added to the positive input terminal and the negative input terminal of the comparator 34. in one embodiment, when the level of the positive input terminal is higher than that of the negative input terminal, the comparator 34 outputs 1, i.e., outputs high level, otherwise, it outputs 0, i.e., outputs low level. In practical applications, to obtain a positive pulse trigger, the amplified signal of the previous stage may be applied to the positive input terminal, i.e. the output of the voltage amplifier 33 is applied to the positive input terminal of the comparator 34. In addition, the positive input terminal and the negative input terminal of the comparator 34 may be set to have a dc level, but the dc level of the negative input terminal needs to be higher than that of the positive input terminal, so that the output of the comparator 34 is consistent when there is no signal and the output signal of the voltage amplifier 33 is low, and the output is 0 in this embodiment. The comparator 34 outputs a 1 only if the echo signal or noise pulse is capacitively coupled to the dc level of the positive terminal, which is greater than the dc level point of the inverting input terminal. In this example, the dc level at the inverting input is the reference voltage value of the comparator 34, and as can be seen from the above description, the present application can adjust the reference voltage value of the comparator 34.

To obtain such a variable threshold, we can use the comparator circuit of fig. 5b or fig. 5 c. In the embodiment of fig. 5b, the controller 70 controls Q51 to be in the off state, the reference voltage of the comparator 34 is set to be higher, i.e. the first value, and when Q51 is in the on state, R51 and R52 are connected in parallel, the equivalent resistance is decreased, and the reference voltage of the comparator 34 is set to be lower, i.e. the second value. In fig. 5c, the controller 70 can output the PWM2 with adjustable frequency and duty ratio, and output a dc level proportional to the duty ratio of the PWM2 as the reference voltage value of the comparator 34 through a two-stage low-pass filter network consisting of 2 resistors and 2 capacitors, and it can be seen that the reference voltage value of the comparator 34 can be adjusted very flexibly through the PWM 2. In fig. 5c, the controller 70 may also output a dc signal through a built-in DAC, and the DAC is loaded to the pull-down resistor R53 to obtain a corresponding dc voltage, that is, a reference voltage value of the comparator 34, and the reference voltage value of the comparator 34 may also be easily controlled, that is, the controller 70 may adjust the reference voltage value of the comparator 34 by adjusting the size of the output DAC.

The particular type of TDC35 of the present application may also be set and adjusted as desired, but it is understood that the solution of the present application does not require that the number of echo pulses must coincide with the set target number, and therefore, a TDC35 with multi-pulse capture capability may be selected and may allow the actual number of captured pulses to not coincide with the set target number. For example, in one case, considering that the MS1003 has 10 pulse capture capabilities in a single channel and 20 pulse capture capabilities in a dual channel, and has the capability that the actual capture pulse number may not coincide with the set target number and the echo measurement is still valid, the MS1003 may be selected as the TDC of the present application. MS1003 adopts advanced technology, compares 60 to 80P picosecond's precision in traditional TDC35 scheme, has used the scheme of this application after, and the double-channel single precision is 46 picoseconds, and the single channel double precision is 23 picoseconds, and what correspond is 3 ~ 4 mm's measurement accuracy.

Of course, in other applications, other satisfactory TDCs 35 may be selected according to actual needs.

Referring to fig. 6, a schematic diagram of a chip structure of the MS1003 is shown, which can communicate with the controller 70. The time interval measurement may be achieved by receiving a START signal for a light pulse through the START port and an echo signal through STOP1 and STOP 2.

In an embodiment of the present invention, when determining that the number of times of the echo pulse received by the TDC35 in the signal receiving circuit is greater than K, the step S105 may specifically include:

for any 1 echo pulse output by the comparator 34, detecting a rising edge of the echo pulse through the first channel of the TDC35 and converting the rising edge into a corresponding distance value, and detecting a falling edge of the echo pulse through the second channel of the TDC35 and converting the falling edge into a corresponding distance value;

and determining a corresponding error correction value through the pulse width, correcting the distance to be compensated based on the error correction value, and taking the obtained correction result as the distance of the determined target position.

In this embodiment, although it is considered that, when the echo pulse is detected, the TDC35 normally detects a rising edge, but referring to fig. 7, the reflectivity of different substances differs at the same distance, the echo intensity differs, and the time interval for detection differs, that is, the absolute error due to the echo intensity.

In this regard, in this embodiment, the pulse width is calculated, taking TDC35 as MS1003 as an example, STOP1 of MS1003 as its first channel, and STOP2 as its second channel, and these two channels are used in parallel in this embodiment, that is, for any 1 echo pulse output by comparator 34, STOP1 and STOP2 can both receive the pulse, and STOP1 detects the rising edge of the pulse and converts it into a corresponding distance value, and STOP2 detects the rising edge of the pulse and converts it into a corresponding distance value.

Referring to fig. 2b, the first peak of the histogram is the distance to be compensated, which represents the leading edge (rising edge) of the echo pulse, and the second peak represents the trailing edge (falling edge) of the echo pulse, and the pulse width is the trailing edge-leading edge, i.e. the difference between the 2 distance values with the highest frequency of occurrence in fig. 2b is the pulse width.

After the pulse width is obtained, the corresponding error correction value can be determined by the pulse width, and the corresponding relationship can be determined in advance through experimental verification and theoretical analysis, for example, a corresponding list of the pulse width and the error correction value can be set, or a function can be fitted, so that the corresponding error correction value can be obtained after the pulse width is input. Finally, the distance to be compensated is corrected based on the error correction value, and the obtained correction result is the distance of the determined target position, for example, a simple way is to directly superimpose the error correction value and the distance to be compensated.

In addition, it should be noted that, when the distance is long, because the signals are all relatively small, that is, the amplitude of the echo signal from the target position is equivalent to the noise level, and therefore the ranging error caused by the amplitude can be ignored, so that under the long-distance test, only the leading edge of the pulse needs to be grabbed, for example, in the embodiment of fig. 2a, after the leading edge of each echo pulse is grabbed and converted into a distance, the distance value with the highest outgoing line frequency can be directly used as the determined distance of the target position.

In an embodiment of the present invention, the step S104 of transmitting B optical pulses to the target location by the control signal transmitting circuit may specifically include:

the control signal transmitting circuit transmits B light pulses to the target location and, upon transmitting each 1 of the B light pulses, controls each signal receiving channel of the TDC35 to be enabled after a first time delay relative to the start signal for the light pulse.

In the embodiment, the telescope range finder measures a sufficiently long distance, the safety level of single reflection energy is about 200nJ, and the energy release causes certain fluctuation to the power supply and the ground, and although the mode of isolation is realized by an LC filter, a magnetic bead and the like, the influence of the fluctuation cannot be completely eliminated. Therefore, when the light pulse is emitted, the same frequency interference also appears at the receiving end, and the interference appears only in a period of inherent time after the emission, has no relation with the object to be detected and the ambient light, and belongs to the interference of pure electrons. As can be seen from the foregoing description, the received energy is inversely proportional to the square of the distance. Since the reference voltage value of the comparator 34 is set at the high range, i.e., the first value, at the time of performing the short-range distance measurement, the noise including the electronic interference does not easily cross the threshold of the comparator 34.

However, in long range, the reference voltage level of comparator 34 is set at a low level, and noise including the electrical interference may cross the threshold of comparator 34, for which, in this embodiment, a short distance is masked after each of the B light pulses is transmitted. Still taking MS1003 as an example, controller 70 controls STOP1 and STOP2 of MS1003 to be enabled after delaying for a first time period with respect to the start signal of the optical pulse, and in the case of fig. 6, controller 70 may implement delay enabling of STOP1 and STOP2 through En _ STOP1 and En _ STOP 2. That is, after any one of the B optical pulses is transmitted, STOP1 and STOP2 do not receive any pulses because STOP1 and STOP2 are not yet enabled, and as previously described, the disturbance occurs only a certain amount of time after transmission, after a delay, and the electronic disturbance has disappeared when STOP1 and STOP2 are enabled.

In an embodiment of the present invention, after receiving the ranging instruction, the method may further include:

the gate delay self-calibration of TDC35 is performed by an external crystal oscillator of TDC 35.

This embodiment considers that the TDC35 needs to calculate the time interval, and the fluctuation of the ambient temperature and the supply voltage causes the gate delay time inside the TDC35 to change, so in this embodiment, the self-calibration of the gate delay of the TDC35 is performed by the external crystal oscillator of the TDC 35. Of course, when such an embodiment is implemented, the TDC35 carrying the external crystal oscillator to realize the self-calibration of the gate delay needs to be selected, for example, the MS1003 in fig. 6, and the chip is externally connected with a 4MHz high-precision crystal oscillator.

When the gate delay self-calibration of the TDC35 is performed, the trigger timing may be selected according to the requirement, for example, once after each power-on, or periodically, or once before each ranging, the gate delay self-calibration of the TDC35 is performed, which does not affect the implementation of the present invention.

In an embodiment of the present invention, after the TDC in step S105 converts each received echo pulse into a corresponding distance value, the method may further include:

According to the scheme, the distance of the target position is obtained in a statistical mode, so that the function of measuring the distances of a plurality of targets at one time can be achieved. Specifically, after outputting each distance value with the occurrence frequency higher than the first frequency threshold, the user can easily determine which targets respectively correspond to the distances. For example, when the distance of a far handrail is measured, the distance output by the telescopic range finder is 600 meters and 601 meters, so that the user can know that 600 meters is the distance of the handrail and 601 meters is the distance of the wall surface behind the handrail. The specific value of the first frequency threshold can be set and adjusted as required.

It should be noted that, taking MS1003 as an example, a single channel has 10 pulse capture capabilities, and a dual channel has 20 pulse capture capabilities, in the foregoing, the dual channels of MS1003 are used in parallel, that is, STOP1 and STOP2 are connected in parallel, after any 1 optical pulse is transmitted, STOP1 can receive 10 echo pulses at most, and likewise, STOP2 can receive 10 echo pulses at most. In practical applications, if a strong background light is encountered outdoors, the probability of noise increases, and each 10 pulses of the two channels may fill up quickly, so that echo pulses at target locations further away from the rear cannot be captured. Because of the parallel operation of two channels, a noise pulse may be captured by both channels at the same time, which may result in a reduction in the number of echo pulses actually captured at the target location during the entire ranging process.

In this regard, in an embodiment of the present invention, the method may further include:

after receiving the first channel selection command, the TDC35 is controlled to a multi-channel parallel operating state, and after receiving the second channel selection command, the TDC35 is controlled to a multi-channel serial operating state.

In such an embodiment, the TDC35 may be selected to be in a multi-pass serial operation state or in a multi-pass parallel operation state. When TDC35 is operating in parallel with multiple channels, the channels are used in parallel and enabled simultaneously. When the TDC35 is in the multi-channel serial operating state, each channel may be enabled in time-sharing manner in sequence, taking the dual-channel MS1003 as an example, for example, the STOP1 is enabled first, and after waiting for a certain period of time, the STOP2 is enabled. In addition, the measuring range is increased in such a mode, and the measuring range is larger when the measuring range is used in series when the number of channels is larger.

By applying the technical scheme provided by the embodiment of the invention, the distance can be automatically distinguished without mode switching, and then the controller 70 can set the reference voltage value of the comparator 34 and control the signal transmitting circuit to transmit a corresponding number of optical pulses to the target position, so that the scheme of the application realizes the convenience of distance measurement and can conveniently and quickly switch the target for measurement. In addition, the signal receiving circuit of the present application adopts a mode of the comparator 34+ the TDC35, and has high ranging accuracy.

After the controller 70 receives the ranging command, it may control the signal transmitting circuit to transmit N optical pulses to the target location, and in this application, by determining whether the number of times of the echo pulses received by the TDC35 in the signal receiving circuit is greater than K, it may determine the distance between the target location and the target location. Specifically, if the number of times of the echo pulse is greater than K, it is described that the distance measurement is performed in a short distance, the reference voltage value of the comparator 34 in the signal receiving circuit is set to be a higher value, that is, a first value, and then the signal transmitting circuit is controlled to transmit a number of optical pulses to the target position, otherwise, the number of times of the echo pulse is not greater than K, it is described that the distance measurement is performed in a long distance, and the reference voltage value of the comparator 34 in the signal receiving circuit is set to be a smaller second value, and then the signal transmitting circuit is controlled to transmit B number of optical pulses to the target position. Since the reference voltage value of the comparator 34 is high at the time of the short distance measurement, it is advantageous to reduce the influence of the disturbance because the noise does not easily pass through the comparator 34 having a high threshold. During long-distance ranging, the reference voltage value of the comparator 34 is low, so that the ranging distance of the present application is favorably increased, that is, during long-distance ranging, even if the energy of the echo pulse is low, the lower threshold of the comparator 34 can be crossed.

After TDC35 converts each received echo pulse into corresponding distance value, this application is the distance that the distance value that will appear the frequency the highest is regarded as the target location who determines, that is to say, through the mode of statistics, obtain the distance value that the frequency of appearance is the highest, rather than the mode of calculating the average value obtains the distance of target location, consequently is favorable to avoiding because shake, the shake of hand, the error that factors such as interference lead to, can obtain the distance of comparatively accurate target location.

Corresponding to the embodiment of the ranging method based on the telescopic range finder, the embodiment of the invention also provides the telescopic range finder, which can be correspondingly referred to with the embodiment. The telescopic rangefinder may include:

a prism 21, an emitting lens 22, a receiving condenser lens 40, a signal emitting circuit, a signal receiving circuit, an output circuit 60;

input circuit 50: for sending ranging instructions to the controller 70;

a controller 70 for:

judging whether the number of times of echo pulses received by a TDC35 in a signal receiving circuit is more than K;

if the reference voltage value is larger than K, setting the reference voltage value of the comparator 34 in the signal receiving circuit to be a first value, and controlling the signal transmitting circuit to transmit A optical pulses to the target position;

if not, setting the reference voltage value of the comparator 34 to a second value, and controlling the signal transmitting circuit to transmit B light pulses to the target position;

after the TDC35 converts each received echo pulse into a corresponding distance value, taking the distance value with the highest frequency of occurrence as the distance of the determined target position;

outputs the distance of the determined target position to the output circuit 60;

It is further noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Those of skill would further appreciate that the various illustrative components and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the components and steps of the various examples have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

The principle and the implementation of the present invention are explained in the present application by using specific examples, and the above description of the embodiments is only used to help understanding the technical solution and the core idea of the present invention. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall into the protection scope of the present invention.

Claims

1. A distance measuring method based on a telescope range finder is characterized by comprising the following steps:

outputting the determined distance of the target position;

2. The telescopic range finder-based ranging method according to claim 1, wherein when it is determined that the number of times of the echo pulses received by the TDC in the signal receiving circuit is greater than K, said determining the distance value with the highest frequency of occurrence as the determined distance of the target position after the TDC converts each received echo pulse into the corresponding distance value comprises:

3. The telescopic rangefinder-based ranging method of claim 1 wherein said controlling the signal transmission circuitry to transmit B light pulses to the target location comprises:

4. The telescopic rangefinder-based ranging method of claim 1 further comprising, after receiving the ranging command:

5. The telescopic rangefinder-based ranging method of claim 1 further comprising:

6. The telescopic range finder-based ranging method of any one of claims 1 to 5, further comprising, after the TDC converts each received echo pulse into a corresponding range value:

7. A telescopic rangefinder, comprising:

an input circuit: the controller is used for sending a ranging command to the controller;

the controller is configured to:

8. The telescopic rangefinder of claim 7 wherein the signal transmission circuitry comprises:

9. The telescopic rangefinder of claim 8 wherein the switching circuit comprises: the first switch tube, the first capacitor and the drive circuit;

10. The telescopic rangefinder of claim 9, further comprising: a second capacitor and a first resistor;

11. A telescopic rangefinder according to any of claims 7 to 10 wherein the signal receiving circuit comprises:

a reverse bias circuit connected to a cathode of the avalanche photodiode;

the transimpedance amplifier;

the voltage amplifier is connected with the transimpedance amplifier;

and the TDC is connected with the output end of the comparator.