A laser ranging sensor based on laser phase method

Abstract

The application discloses a laser ranging sensor based on a laser phase method and relates to the technical field of laser ranging.The sensor comprises a crystal oscillator, a micro control unit, a reference signal generating module, a measuring signal generating module and an analog-to-digital converter.The crystal oscillator is used to generate a first sinusoidal signal, thereby driving the micro control unit to operate.The micro control unit is used to control the reference signal generating module to generate a reference signal based on the first sinusoidal signal, control the measuring signal generating module to generate a laser beam based on the first sinusoidal signal, control the measuring signal generating module to generate a measuring signal according to the laser reflected by a measured target, calculate a reference phase according to the reference signal converted by the analog-to-digital converter, calculate a measuring phase according to the measuring signal converted by the analog-to-digital converter and calculate the distance from the measured target to the laser ranging sensor according to the reference phase and the measuring phase.The application improves the measurement precision of long-distance measurement.

Description

Technical Field

[0001] This invention relates to the field of laser ranging technology, and in particular to a laser ranging sensor based on the laser phase method. Background Technology

[0002] As robotics technology matures, robots are being used more and more widely across various industries. Currently, robots are widely used in manufacturing, agriculture, construction, healthcare, elderly care services, and education. A crucial sensor in robots is the ranging sensor, whose main functions are obstacle avoidance and path planning. Therefore, robots require the following ranging sensors: 1. High measurement speed, typically reaching 1kHz; 2. High accuracy, typically reaching 2cm. Existing ranging sensors used in robots operate on the triangulation method, and their ranging principle is as follows... Figure 2 As shown, during ranging, the angle between the emitted light from the point laser and the perpendicular line from the CCD target surface is β; the distance between the point laser and the object being measured is D; the length of the first line connecting the front face of the laser and the center (small aperture) of the imaging lens is s; the perpendicular distance from the object being measured to the first line is q; f is the focal length of the receiving lens; P is the upper boundary of the CCD (after the laser point is irradiated to infinity, it is imaged at point P through the lens); g is the position of the laser point irradiating the object being measured and imaged on the CCD through the lens. Assume the distance from Pg is x. According to trigonometric relationships, the distance between the point laser and the object being measured is: D = fs / (sinβ*x). According to the working principle of the CCD, the distance x is the distance between pixels, and its physical resolution is 1 pixel. D = fs / (sinβ*x), where the derivative of D with respect to x is dD / dx = D^2 / (fs*(sinβ)^2), where dD represents the change in distance D, and dx represents the change in x. In laser rangefinders of the same model, f, s, and β are fixed, known values, while x is the distance from the center of the image formed by the laser on the CCD to the CCD boundary. Generally, the pixel value from the image center to the CCD boundary is calculated using a specific algorithm, and then multiplied by the physical size of the pixel (the physical size of the pixel is known and fixed for the same model) to calculate x. The working principle of a laser rangefinder is that the software calculates the x value, and then calculates D according to the above formula.

[0003] Based on the above principles, the following conclusions can be drawn: 1. In the same type of laser rangefinder sensor, the larger D is, the larger the resulting dD is when dx is a fixed variable. This means that the accuracy will significantly decrease when measuring long distances, and the accuracy is directly proportional to the square of the measured distance. 2. To achieve higher measurement accuracy, f, s, and β need to be increased, but this will lead to a larger size of the laser rangefinder sensor. Summary of the Invention

[0004] The purpose of this invention is to provide a laser ranging sensor based on the laser phase method, which improves the measurement accuracy of long-distance measurements.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A laser ranging sensor based on laser phase method includes: a crystal oscillator, a microcontroller unit, a reference signal generation module, a measurement signal generation module, and an analog-to-digital converter;

[0007] The crystal oscillator is connected to the input terminal of the microcontroller unit, the output terminal of the microcontroller unit is connected to the input terminal of the reference signal generation module and the input terminal of the measurement signal generation module, respectively, the input terminal of the analog-to-digital converter is connected to the output terminal of the reference signal generation module and the output terminal of the measurement signal generation module, respectively; the output terminal of the analog-to-digital converter is connected to the input terminal of the microcontroller unit.

[0008] The crystal oscillator is used to generate a first sine wave signal, thereby driving the microcontroller unit to operate;

[0009] The microcontroller unit is used for:

[0010] The reference signal generation module is controlled to generate a reference signal based on the first sine wave signal;

[0011] The measurement signal generation module is controlled to generate a laser beam based on the first sine wave signal;

[0012] The measurement signal generation module is controlled to generate a measurement signal based on the laser light reflected by the target being measured;

[0013] The reference phase is calculated based on the reference signal after being converted by the analog-to-digital converter.

[0014] The measurement phase is calculated based on the measurement signal after conversion by the analog-to-digital converter.

[0015] The distance from the target to the laser rangefinder is calculated based on the reference phase and the measurement phase.

[0016] Optionally, the reference signal generation module includes: a frequency divider, a digital frequency generator, a first analog switch, a second analog switch, and a mixing and filtering circuit;

[0017] The microcontroller unit is connected to the frequency divider, the digital frequency generator, the first analog switch, and the second analog switch, respectively. The frequency divider and the digital frequency generator are both connected to the first analog switch. The digital frequency generator is connected to the second analog switch. The first analog switch and the second analog switch are both connected to the mixing and filtering circuit. The mixing and filtering circuit is connected to the analog-to-digital converter.

[0018] The frequency divider is used for:

[0019] The first sine wave signal is divided by frequency to obtain the frequency-divided first sine wave signal;

[0020] The microcontroller unit is specifically used for:

[0021] The digital frequency generator is controlled to generate a second sine wave signal, a third sine wave signal, and a fourth sine wave signal based on the first sine wave signal;

[0022] The first analog switch is controlled to output a first output signal based on the first sine wave signal and the second sine wave signal after frequency division; the first output signal is either the first sine wave signal or the second sine wave signal after frequency division.

[0023] The second analog switch is controlled to output a second output signal based on the third sine wave signal and the fourth sine wave signal; the second output signal is either the third sine wave signal or the fourth sine wave signal.

[0024] The mixing and filtering circuit is used to generate the reference signal based on the first output signal and the second output signal.

[0025] Optionally, the measurement signal generation module includes: a frequency divider, a digital frequency generator, a first analog switch, a second analog switch, a laser diode, an avalanche photodiode, an avalanche photodiode, and a bandpass filter circuit;

[0026] The microcontroller unit is connected to the frequency divider, the digital frequency generator, the first analog switch, the second analog switch, and the avalanche photodiode. The frequency divider and the digital frequency generator are both connected to the first analog switch. The digital frequency generator is connected to the second analog switch. The first analog switch is connected to the laser diode. The second analog switch is connected to the avalanche photodiode. The avalanche photodiode is connected to the bandpass filter circuit. The bandpass filter circuit is connected to the analog-to-digital converter.

[0027] The frequency divider is used for:

[0028] The first sine wave signal is divided by frequency to obtain the frequency-divided first sine wave signal;

[0029] The microcontroller unit is specifically used for:

[0030] The digital frequency generator is controlled to generate a second sine wave signal, a third sine wave signal, and a fourth sine wave signal based on the first sine wave signal;

[0031] The first analog switch is controlled to output a first output signal based on the first sine wave signal and the second sine wave signal after frequency division; the first output signal is either the first sine wave signal or the second sine wave signal after frequency division.

[0032] The second analog switch is controlled to output a second output signal based on the third sine wave signal and the fourth sine wave signal; the second output signal is either the third sine wave signal or the fourth sine wave signal.

[0033] The laser diode is used for:

[0034] A laser beam is generated based on the first output signal and irradiated onto the target under test.

[0035] The avalanche photodiode is used to receive the laser beam reflected by the target under test, and to perform photoelectric conversion on the laser beam reflected by the target under test to obtain the reflected electrical signal;

[0036] The microcontroller unit is also specifically used for:

[0037] The avalanche photodiode is controlled to generate a first mixing signal and a second mixing signal based on the second output signal and the reflected electrical signal;

[0038] The bandpass filter circuit is used for:

[0039] The first and second mixing signals are filtered out to obtain the measurement signal.

[0040] Optionally, the measurement signal generation module further includes: a first amplification circuit; the first amplification circuit is connected to the first analog switch and the laser diode respectively;

[0041] The first amplifier circuit is used to modulate the first output signal and send it to the laser diode.

[0042] Optionally, the measurement signal generation module further includes: a second amplifier circuit; the second amplifier circuit is connected to the second analog switch and the avalanche photodiode, respectively;

[0043] The second amplifier circuit is used to modulate the second output signal and send it to the avalanche photodiode.

[0044] Optionally, the measurement signal generation module further includes: a receiving lens; the avalanche photodiode is disposed at the focal point of the receiving lens;

[0045] The avalanche photodiode receives the laser beam reflected from the target being measured through the receiving lens.

[0046] Optionally, the measurement signal generation module further includes: a third amplification circuit; the third amplification circuit is connected to the avalanche photodiode and the bandpass filter circuit respectively;

[0047] The third amplifier circuit is used to modulate the first mixing signal and the second mixing signal and then send them to the bandpass filter circuit.

[0048] Optionally, the measurement signal generation module further includes: a high-voltage circuit; the high-voltage circuit is connected to the microcontroller unit and the avalanche photodiode respectively;

[0049] The microcontroller unit controls the amplification factor of the avalanche photodiode by controlling the output voltage of the high-voltage circuit.

[0050] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0051] This invention discloses a laser ranging sensor based on the laser phase method, comprising: a crystal oscillator, a microcontroller unit, a reference signal generation module, a measurement signal generation module, and an analog-to-digital converter (ADC). First, the crystal oscillator generates a first sine wave signal to drive the microcontroller unit. Then, the microcontroller unit: controls the reference signal generation module to generate a reference signal based on the first sine wave signal; controls the measurement signal generation module to generate a laser beam based on the first sine wave signal; controls the measurement signal generation module to generate a measurement signal based on the laser reflected from the target; calculates a reference phase based on the reference signal converted by the ADC; calculates a measurement phase based on the measurement signal converted by the ADC; and calculates the distance from the target to the laser ranging sensor based on the reference phase and the measurement phase. By jointly determining the distance based on the measurement phase and the reference phase, random errors are eliminated, and the measurement accuracy for long-distance measurements is improved. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 A block diagram of a laser ranging sensor based on the laser phase method provided in an embodiment of the present invention;

[0054] Figure 2 A schematic diagram illustrating the ranging principle of a ranging sensor utilizing the triangulation method;

[0055] Figure 3 A schematic diagram of the specific structure of a laser ranging sensor based on the laser phase method provided in an embodiment of the present invention;

[0056] Figure 4 This is a schematic diagram of the DDS structure;

[0057] Figure 5 This is a schematic diagram of the first amplifier circuit.

[0058] Figure 6 This is a schematic diagram of the second amplifier circuit.

[0059] Figure 7 This is a schematic diagram of the structure of the first or second analog switch;

[0060] Figure 8 This is a schematic diagram of the circuit structure consisting of a third amplifier circuit and a bandpass filter circuit.

[0061] Figure 9 This is a schematic diagram of a mixer filter circuit.

[0062] Symbol explanation:

[0063] Crystal oscillator—1, Microcontroller unit—2, Reference signal generation module—3, Measurement signal generation module—4, Analog-to-digital converter—5. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] The purpose of this invention is to provide a laser ranging sensor based on the laser phase method, which aims to improve the measurement accuracy of long-distance measurements.

[0066] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0067] Figure 1This is a block diagram of a laser ranging sensor based on the laser phase method provided in an embodiment of the present invention. Figure 3 A schematic diagram of the specific structure of the laser ranging sensor based on the laser phase method provided in this embodiment of the invention ( Figure 3 Solid arrows represent signal transmission, while dashed arrows represent control. (For example...) Figure 1 and Figure 3 As shown, the laser ranging sensor based on the laser phase method in this embodiment includes: a crystal oscillator 1, a microcontroller unit (MCU) 2, a reference signal generation module 3, a measurement signal generation module 4, and an analog-to-digital converter (ADC) 5.

[0068] Crystal oscillator 1 is connected to the input terminal of microcontroller 2. The output terminal of microcontroller 2 is connected to the input terminal of reference signal generation module 3 and the input terminal of measurement signal generation module 4, respectively. The input terminal of analog-to-digital converter 5 is connected to the output terminal of reference signal generation module 3 and the output terminal of measurement signal generation module 4, respectively. The output terminal of analog-to-digital converter 5 is connected to the input terminal of microcontroller 2.

[0069] Crystal 1 is used to generate a first sine wave signal, thereby driving the microcontroller unit 2 to operate.

[0070] Microcontroller unit 2, used for:

[0071] The control reference signal generation module 3 generates a reference signal based on the first sine wave signal.

[0072] The control measurement signal generation module 4 generates a laser beam based on the first sine wave signal.

[0073] The control measurement signal generation module 4 generates a measurement signal based on the laser reflected by the target being measured.

[0074] The reference phase is calculated based on the reference signal after conversion by analog-to-digital converter 5.

[0075] The measurement phase is calculated based on the measurement signal after conversion by analog-to-digital converter 5.

[0076] The distance from the target to the laser rangefinder is calculated based on the reference phase and the measured phase.

[0077] As an optional implementation, the reference signal generation module 3 includes: a frequency divider, a digital frequency generator, a first analog switch, a second analog switch, and a mixing and filtering circuit.

[0078] The microcontroller unit 2 is connected to the frequency divider, the digital frequency generator, the first analog switch, and the second analog switch, respectively. The frequency divider and the digital frequency generator are both connected to the first analog switch, and the digital frequency generator is connected to the second analog switch. The first analog switch and the second analog switch are both connected to the mixing filter circuit, and the mixing filter circuit is connected to the analog-to-digital converter 5.

[0079] Frequency dividers are used for:

[0080] The first sine wave signal is divided by frequency to obtain the frequency-divided first sine wave signal.

[0081] Microcontroller unit 2 is specifically used for:

[0082] The digital frequency generator is controlled to generate a second, third, and fourth sine wave signal based on the first sine wave signal.

[0083] The first analog switch is controlled to output a first output signal based on the first sine wave signal and the second sine wave signal after frequency division; the first output signal is either the first sine wave signal or the second sine wave signal after frequency division.

[0084] The second analog switch is controlled to output a second output signal based on the third and fourth sine wave signals; the second output signal is either the third or the fourth sine wave signal.

[0085] The mixing and filtering circuit is used to generate a reference signal based on the first output signal and the second output signal.

[0086] As an optional implementation, the measurement signal generation module 4 includes: a frequency divider, a digital frequency generator, a first analog switch, a second analog switch, a laser diode, an avalanche photodiode, an avalanche photodiode (APD), and a bandpass filter circuit.

[0087] The microcontroller unit 2 is connected to the frequency divider, the digital frequency generator, the first analog switch, the second analog switch, and the avalanche photodiode. The frequency divider and the digital frequency generator are both connected to the first analog switch. The digital frequency generator is connected to the second analog switch. The first analog switch is connected to the laser diode. The second analog switch is connected to the avalanche photodiode. The avalanche photodiode is connected to the bandpass filter circuit. The bandpass filter circuit is connected to the analog-to-digital converter 5.

[0088] Frequency dividers are used for:

[0089] The first sine wave signal is divided by frequency to obtain the frequency-divided first sine wave signal.

[0090] Microcontroller unit 2 is specifically used for:

[0091] The digital frequency generator is controlled to generate a second, third, and fourth sine wave signal based on the first sine wave signal.

[0092] The first analog switch is controlled to output a first output signal based on the first sine wave signal and the second sine wave signal after frequency division; the first output signal is either the first sine wave signal or the second sine wave signal after frequency division.

[0093] The second analog switch is controlled to output a second output signal based on the third and fourth sine wave signals; the second output signal is either the third or the fourth sine wave signal.

[0094] Laser diodes are used for:

[0095] A laser beam is generated based on the first output signal and irradiates the target being tested.

[0096] Avalanche photodiodes are used to receive laser light reflected from a target and convert it into a photoelectric signal.

[0097] The microcontroller unit 2 is also specifically used for:

[0098] The avalanche photodiode is controlled to generate a first mixing signal and a second mixing signal based on the second output signal and the reflected electrical signal.

[0099] Bandpass filter circuit, used for:

[0100] The first and second mixing signals are filtered out to obtain the measurement signal.

[0101] As an optional implementation, the measurement signal generation module 4 further includes: a first amplifier circuit; the first amplifier circuit is connected to the first analog switch and the laser diode respectively.

[0102] The first amplifier circuit is used to modulate the first output signal and send it to the laser diode.

[0103] As an optional implementation, the measurement signal generation module 4 further includes a second amplifier circuit; the second amplifier circuit is connected to the second analog switch and the avalanche photodiode respectively.

[0104] The second amplifier circuit is used to modulate the second output signal and send it to the avalanche photodiode.

[0105] As an optional implementation, the measurement signal generation module 4 further includes: a receiving lens; an avalanche photodiode is disposed at the focal point of the receiving lens.

[0106] Avalanche photodiodes receive laser light reflected from the target object through a receiving lens.

[0107] As an optional implementation, the measurement signal generation module 4 further includes a third amplifier circuit; the third amplifier circuit is connected to the avalanche photodiode and the bandpass filter circuit respectively.

[0108] The third amplifier circuit is used to modulate the first and second mixing signals and then send them to the bandpass filter circuit.

[0109] As an optional implementation, the measurement signal generation module 4 also includes a high-voltage circuit; the high-voltage circuit is connected to the microcontroller unit 2 and the avalanche photodiode respectively.

[0110] The microcontroller unit 2 controls the amplification factor of the avalanche photodiode by controlling the output voltage of the high-voltage circuit.

[0111] The specific circuit structure of each component in the laser ranging sensor based on the laser phase method in this embodiment is as follows:

[0112] (1) As Figure 4 As shown, the circuit structure of DDS is as follows:

[0113] JZ1 is a passive crystal oscillator, and U2 is a DDS. Pins 2 and 4 of JZ1 are grounded. Pin 1 of JZ1 is connected to pin 2 of U2, and pin 3 of JZ1 is connected to pin 3 of U2. Pin 1 of U2 is connected to one end of capacitor C16 and then to a 3.3V power supply. The other end of C16 is grounded. Pins 4 and 5 of U2 are both connected to the MCU's I / O pins. Pin 10 of U2 outputs a sine wave signal with a frequency of f1. Pin 9 of U2 is connected to one end of resistor R12. The other end of R12 outputs a sine wave signal with a frequency of f3. Pin 8 of U2 is grounded. Pin 7 of U2 is connected to one end of capacitor C38, one end of capacitor C37, and one end of inductor L9. The other end of L9 is connected to a 3.3V power supply. The other ends of capacitors C37 and C38 are grounded. Pin 6 of U2 outputs a sine wave signal with a frequency of f2.

[0114] (2) Figure 5 As shown, the circuit structure of the first amplifier circuit is as follows:

[0115] A sinusoidal signal with frequency f1 is input to one end of resistor R1. The other end of R1 is connected to one end of inductor L6. The other end of L6 is connected to one end of capacitor C12 and one end of inductor L4. The other end of C12 is grounded. The other end of L4 is connected to one end of capacitor C7 and one end of capacitor C13. The other end of C7 is grounded. The other end of C13 is connected to one end of resistor R32, one end of resistor R7, and pin 1 of transistor Q5. The other end of R7 is grounded. The other end of R32... One end of inductor L11, one end of capacitor C49, and a 3.3V power supply are connected. The other end of C49 is grounded. The other end of L11 is connected to pin 2 of Q5 and one end of capacitor C50. Pin 3 of Q5 is grounded. The other end of C50 is connected to one end of inductor L13. The other end of L13 is connected to one end of capacitor C52 and one end of inductor L15. The other end of C52 is grounded. The other end of L15 is connected to one end of capacitor C51. The other end of C51 outputs the modulation signal of the first amplifier circuit.

[0116] (3) Figure 6 As shown, the circuit structure of the second amplifier circuit is as follows:

[0117] A sine wave signal with a frequency of f2 is input to one end of resistor R2. The other end of R2 is connected to one end of inductor L12. The other end of L12 is connected to one end of capacitor C39 and one end of inductor L2. The other end of C39 is grounded. The other end of L2 is connected to one end of capacitor C4 and one end of C6. The other end of C4 is grounded. The other end of C6 is connected to one end of resistor R3 and one end of R6, and pin 1 of transistor Q2. The other end of R6 is grounded. The other end of R3 is connected to one end of inductor L1. One end of capacitor C1 is connected to a 3.3V power supply. The other end of C1 is grounded. The other end of L1 is connected to pin 2 of Q2 and one end of capacitor C30. Pin 3 of Q2 is grounded. The other end of C30 is connected to one end of inductor L5. The other end of L5 is connected to one end of capacitor C3. The other end of C3 outputs the modulation signal of the second amplifier circuit.

[0118] (4) Figure 7 As shown, the circuit structure of the first analog switch or the second analog switch is as follows:

[0119] U3 is an analog switch (either the first or second analog switch). Pin 6 of U3 is connected to the MCU. Pin 5 of U3 is connected to one end of capacitor C28 and the 3.3V power supply. The other end of C28 is grounded. Pin 2 of U3 is grounded. Pins 1 and 3 of U3 are input to two sine wave signals respectively. Pin 4 of U3 is the output signal. When pin 6 of U3 is high, pins 1 and 4 of U3 are connected; when pin 6 is low, pins 2 and 4 of U3 are connected.

[0120] (5) Figure 8As shown, the structure of the circuit consisting of the third amplifier circuit and the bandpass filter circuit is as follows:

[0121] D1 is an APD. One end of D1 is connected to the output of the high-voltage circuit, and the other end of D1 is connected to one end of resistor R535. The other end of R535 is connected to one end of capacitor C512, one end of resistor R585, one end of capacitor C546, and pin 2 of operational amplifier U22A. The other end of capacitor C512 is grounded. The other end of resistor R585 is connected to one end of resistor R1. The other end of resistor R1 is connected to one end of resistor R555 and one end of resistor R503. The other end of resistor R555 is connected to one end of capacitor C526, and the other end of capacitor C526 is grounded. The other end of resistor R503 is connected to one end of capacitor C546, pin 1 of operational amplifier U22A, and one end of resistor R556. The other end of resistor R556 is connected to one end of capacitor C564, and the other end of capacitor C564 is grounded. The other end of resistor R546 is connected to one end of capacitor C592 and one end of capacitor C590. The other end of capacitor C590 is connected to one end of resistor R560 and pin 6 of operational amplifier U22B. The other end of resistor R560 is connected to pin 7 of operational amplifier U22B. Pin 7 of operational amplifier U22B outputs a measurement signal. The 3.3V power supply is connected to one end of resistor R80. The other end of resistor R80 is connected to one end of capacitor C6 and one end of resistor R509. The other end of capacitor C6 is grounded. The other end of resistor R509 is connected to one end of resistor R550, one end of capacitor C510, pin 3 of operational amplifier U22A, pin 5 of operational amplifier U22B, and one end of capacitor C574. The other ends of capacitor C574, resistor R550, and capacitor C510 are all grounded.

[0122] (6) Figure 9 As shown, the circuit structure of the mixer filter circuit is as follows:

[0123] One end of capacitor C12 is connected to one end of resistor R18 and then to the output signal of the first analog switch. The other end of capacitor C12 is grounded. The other end of resistor R18 is connected to one end of capacitor C31. The other end of capacitor C31 is connected to one end of resistor R30, one end of resistor R22, and pin 1 of transistor Q7. The other end of resistor R22 is connected to one end of capacitor C43, one end of R20, and one end of capacitor C27. One end of capacitor C27 is connected to a 3.3V power supply. The other ends of capacitor C27 and capacitor C43 are both grounded. The other end of resistor R20 is connected to pin 2 of transistor Q7, one end of capacitor C23, and one end of resistor R8. The other end of capacitor C23 is grounded. Pin 3 of transistor Q7 is connected to one end of capacitor C36 and one end of resistor R9. The other end of resistor R9 is grounded. The other end of capacitor C36 is connected to one end of resistor R36 and then to one end of capacitor C12. Then, it is connected to the output signal of the second analog switch. The other end of capacitor C12 is grounded. The other end of resistor R8 is connected to one end of resistor R43 and one end of capacitor C26 respectively. The other end of capacitor C26 is grounded. The other end of resistor R43 is connected to one end of capacitor C35 and one end of capacitor C17 respectively. The other end of capacitor C35 is connected to one end of R44 and pin 4 of operational amplifier U7 respectively. Pin 4 of U7 outputs the mixing signal. The other end of capacitor C17 is connected to the other end of resistor R44 and pin 3 of operational amplifier U7 respectively. Pin 2 of operational amplifier U7 is grounded. Pin 1 of operational amplifier U7 is connected to one end of resistor R41, one end of capacitor C15 and one end of resistor R42 respectively. The other end of resistor R42 is connected to a 3.3V power supply. The other ends of capacitor C15 and resistor R41 are both grounded. Pin 5 of operational amplifier U7 is connected to one end of capacitor C45 and then connected to a 3.3V power supply. The other end of capacitor C45 is grounded.

[0124] The working principle of the laser ranging sensor based on the laser phase method in this embodiment includes:

[0125] A crystal oscillator generates a sine wave signal with a frequency of f0 (i.e., the first sine wave signal), which is input to the MCU driver (the MCU core operates, and after passing through the MCU's internal circuitry, the output remains unchanged). The sine wave signal with a frequency of f0 is then input to a Direct Digital Synthesizer (DDS) (the digital frequency generator used here is a DDS) and a frequency divider. After being divided by N by the frequency divider, a sine wave signal with a frequency of f0 / N (i.e., the divided first sine wave signal) is output, where N is a non-zero integer. The MCU controls the DDS to output sine wave signals with frequencies of f1, f2, and f3 (representing the second, third, and fourth sine wave signals, respectively). The second sine wave signal and the divided first sine wave signal pass through a first analog switch. The first output signal of the first analog switch is controlled by the MCU. At any given moment, the frequency ft of the first output signal can only be f1 or f0 / N. After passing through a first amplification circuit, the first output signal is modulated onto a laser diode, causing the laser diode to emit a laser beam containing the frequency and phase information of the first output signal.

[0126] The third and fourth sine wave signals are input to the second analog circuit. The second output signal of the second analog circuit is controlled by the MCU. At any given time, the frequency fr of the second output signal can only be either f2 or f3. After passing through the second amplifier circuit, the second output signal is modulated onto the APD. The amplification factor of the APD is controlled by the high voltage output of the high voltage circuit; the higher the voltage, the greater the amplification factor. Simultaneously, the high voltage output of the high voltage circuit is controlled by the MCU. The APD receives the laser light reflected from the target object, carrying the frequency and phase information of the first output signal. It converts this into an electrical signal (i.e., the reflected electrical signal) carrying the frequency and phase information of the first output signal. The first and second output signals are mixed internally within the APD to generate two signals with frequencies of ft+fr and ft-fr (the first and second mixing signals), which are then output. After passing through the third amplifier circuit and a bandpass filter circuit with a center frequency of ft-fr, the APD outputs a sine wave signal with a frequency of ft-fr and a phase of P0, i.e., the measurement signal. The measurement signal is output to the ADC, converted into a digital signal, and received by the MCU. The MCU then performs a Fourier transform to calculate the phase value P0 (i.e., the measurement phase). During the measurement process, due to the different reflectivity of the measured object, the measurement signal magnitude is different. The MCU will dynamically adjust the output voltage of the high voltage circuit to adjust the amplification factor of the APD, and ultimately achieve the purpose of adjusting the measurement signal magnitude.

[0127] Simultaneously, the first output signal and the second output signal are input to the mixing and filtering circuit. Inside the mixing circuit, two sine wave signals with frequencies of ft+fr and ft-fr are first generated. After low-pass filtering or band-pass filtering, a sine wave signal with frequency of ft-fr is output, which is the reference signal. The reference signal is input to the ADC, converted by the ADC, and received by the MCU. After Fourier transform, the phase P1 (i.e., the reference phase) is calculated.

[0128] Although the reference signal and the measured signal have the same frequency, their phases are not the same. Because the phase of the output sine wave signal after a DDS is powered off and then powered back on is random, it cannot be guaranteed that the phase of the output signal will be exactly the same each time. By combining the measured signal and the reference signal, random errors are eliminated, and measurement accuracy is improved.

[0129] A specific implementation scheme based on the above principles:

[0130] f0 = 25MHz, N = 2, f0 / 2 = 12.5MHz, speed of light C = 3 * 10⁸ m / s, f1 = 12.5MHz - 10KHz, f2 = 125MHz, f3 = 125MHz – 10KHz.

[0131] Using the "indirect measuring frequency method", f0 / 2 and f1 form one measuring scale λ1=C / f0=12m; f2 and f3 form another measuring scale λ2=2*C / f2=1.2m.

[0132] Where λ1 is used to ensure the range of the ranging sensor, and λ2 is used to ensure the ranging accuracy of the ranging sensor. Based on the experience of the laser phase method ranging principle, the phase accuracy of the Fourier transform after the ADC acquires a measurement signal for one cycle is 2 to 3 degrees. The worst accuracy of the laser ranging sensor can be calculated as follows: 3 / 360*120cm=1cm.

[0133] The following is the specific workflow: During distance measurement, the MCU controls the DDS to output signals with frequencies of f1, f2, and f3 respectively; the MCU first controls the frequency of the first output signal of the first analog switch to ft = 12.5MHz, and controls the frequency of the second output signal of the second analog switch to fr = 12.5MHz–10KHz; the measured distance d1 = (P0-P1) / 360*λ1; the MCU then controls the frequency of the first output signal of the first analog switch to ft = 125MHz; controls the frequency of the second output signal of the second analog switch to fr = 12.5MHz–10KHz; the measured distance d2 = (P0-P1)' / 360*λ2; since the actual distance d may be longer than the measuring scale λ2, the actual formula for d2 should be: d2 = (P0-P1)' / 360*λ2 + n*λ2. d1 is used to accurately calculate the value of n in the above formula, thereby calculating the final distance.

[0134] Based on the above, the frequency of the measurement signal is 10kHz. Each distance measurement requires acquiring one cycle of the measurement signals from measuring scale 1 and measuring scale 2, taking 0.2ms. The control and calculation time does not exceed 0.1ms. When using a Universal Asynchronous Receiver / Transmitter (UART) for data transmission at a baud rate of 115200 baud and a data frame size of 6 bytes, the total measurement transmission time is 0.35ms, and the ranging speed can reach 2857Hz. When using a smaller lens, the sensor size can be made very small. The laser ranging sensor based on the laser phase method of this invention can achieve the specifications shown in Table 1, while existing laser ranging sensors based on the triangulation method can achieve the specifications shown in Table 2. Comparing Tables 1 and 2, the scheme proposed in this invention has significant advantages over the triangulation ranging principle scheme in terms of measurement distance, accuracy, and size. This scheme uses the laser phase ranging principle, and the accuracy can reach 1cm within the measurement range.

[0135] Table 1 Specifications of Laser Ranging Sensors Based on Laser Phase Method

[0136] accuracy 1cm frequency 2850Hz size 20*16*7mm

[0137] Table 2 Specifications of laser rangefinders based on triangulation

[0138]

[0139]

[0140] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0141] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the device and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A laser ranging sensor based on the laser phase method, characterized in that, include: Crystal oscillator, microcontroller unit, reference signal generation module, measurement signal generation module, and analog-to-digital converter; The crystal oscillator is connected to the input terminal of the microcontroller unit, the output terminal of the microcontroller unit is connected to the input terminal of the reference signal generation module and the input terminal of the measurement signal generation module, respectively, the input terminal of the analog-to-digital converter is connected to the output terminal of the reference signal generation module and the output terminal of the measurement signal generation module, respectively; the output terminal of the analog-to-digital converter is connected to the input terminal of the microcontroller unit. The crystal oscillator is used to generate a first sine wave signal, thereby driving the microcontroller unit to operate; The microcontroller unit is used for: The reference signal generation module is controlled to generate a reference signal based on the first sine wave signal; The measurement signal generation module is controlled to generate a laser beam based on the first sine wave signal; The measurement signal generation module is controlled to generate a measurement signal based on the laser light reflected by the target being measured; The reference phase is calculated based on the reference signal after being converted by the analog-to-digital converter. The measurement phase is calculated based on the measurement signal after conversion by the analog-to-digital converter. The distance from the target to the laser rangefinder is calculated based on the reference phase and the measurement phase. The reference signal generation module includes: a frequency divider, a digital frequency generator, a first analog switch, a second analog switch, and a mixing and filtering circuit; The microcontroller unit is connected to the frequency divider, the digital frequency generator, the first analog switch, and the second analog switch, respectively. The frequency divider and the digital frequency generator are both connected to the first analog switch. The digital frequency generator is connected to the second analog switch. The first analog switch and the second analog switch are both connected to the mixing and filtering circuit. The mixing and filtering circuit is connected to the analog-to-digital converter. The frequency divider is used for: The first sine wave signal is divided by frequency to obtain the frequency-divided first sine wave signal; The microcontroller unit is specifically used for: The digital frequency generator is controlled to generate a second sine wave signal, a third sine wave signal, and a fourth sine wave signal based on the first sine wave signal; The first analog switch is controlled to output a first output signal based on the first sine wave signal and the second sine wave signal after frequency division; the first output signal is either the first sine wave signal or the second sine wave signal after frequency division. The second analog switch is controlled to output a second output signal based on the third sine wave signal and the fourth sine wave signal; the second output signal is either the third sine wave signal or the fourth sine wave signal. The mixing and filtering circuit is used to generate the reference signal based on the first output signal and the second output signal.

2. The laser ranging sensor based on the laser phase method according to claim 1, characterized in that, The measurement signal generation module includes: a frequency divider, a digital frequency generator, a first analog switch, a second analog switch, a laser diode, an avalanche photodiode, an avalanche photodiode, and a bandpass filter circuit. The microcontroller unit is connected to the frequency divider, the digital frequency generator, the first analog switch, the second analog switch, and the avalanche photodiode. The frequency divider and the digital frequency generator are both connected to the first analog switch. The digital frequency generator is connected to the second analog switch. The first analog switch is connected to the laser diode. The second analog switch is connected to the avalanche photodiode. The avalanche photodiode is connected to the bandpass filter circuit. The bandpass filter circuit is connected to the analog-to-digital converter. The frequency divider is used for: The first sine wave signal is divided by frequency to obtain the frequency-divided first sine wave signal; The microcontroller unit is specifically used for: The digital frequency generator is controlled to generate a second sine wave signal, a third sine wave signal, and a fourth sine wave signal based on the first sine wave signal; The first analog switch is controlled to output a first output signal based on the first sine wave signal and the second sine wave signal after frequency division; the first output signal is either the first sine wave signal or the second sine wave signal after frequency division. The second analog switch is controlled to output a second output signal based on the third sine wave signal and the fourth sine wave signal; the second output signal is either the third sine wave signal or the fourth sine wave signal. The laser diode is used for: A laser beam is generated based on the first output signal and irradiated onto the target under test. The avalanche photodiode is used to receive the laser beam reflected by the target under test, and to perform photoelectric conversion on the laser beam reflected by the target under test to obtain the reflected electrical signal; The microcontroller unit is also specifically used for: The avalanche photodiode is controlled to generate a first mixing signal and a second mixing signal based on the second output signal and the reflected electrical signal; The bandpass filter circuit is used for: The first and second mixing signals are filtered out to obtain the measurement signal.

3. The laser ranging sensor based on the laser phase method according to claim 2, characterized in that, The measurement signal generation module further includes: a first amplifier circuit; the first amplifier circuit is connected to the first analog switch and the laser diode respectively; The first amplifier circuit is used to modulate the first output signal and send it to the laser diode.

4. The laser ranging sensor based on the laser phase method according to claim 2, characterized in that, The measurement signal generation module further includes: a second amplifier circuit; the second amplifier circuit is connected to the second analog switch and the avalanche photodiode respectively; The second amplifier circuit is used to modulate the second output signal and send it to the avalanche photodiode.

5. The laser ranging sensor based on the laser phase method according to claim 2, characterized in that, The measurement signal generation module further includes: a receiving lens; the avalanche photodiode is disposed at the focal point of the receiving lens; The avalanche photodiode receives the laser beam reflected from the target being measured through the receiving lens.

6. The laser ranging sensor based on the laser phase method according to claim 2, characterized in that, The measurement signal generation module further includes: a third amplifier circuit; the third amplifier circuit is connected to the avalanche photodiode and the bandpass filter circuit respectively; The third amplifier circuit is used to modulate the first mixing signal and the second mixing signal and then send them to the bandpass filter circuit.

7. The laser ranging sensor based on the laser phase method according to claim 2, characterized in that, The measurement signal generation module further includes a high-voltage circuit; the high-voltage circuit is connected to the microcontroller unit and the avalanche photodiode respectively. The microcontroller unit controls the amplification factor of the avalanche photodiode by controlling the output voltage of the high-voltage circuit.

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