Calibration System and Method for FMCW Laser Rangefinder

Abstract

The present invention relates to the technical field of laser ranging, and discloses a calibration system and method for an FMCW laser rangefinder. The system includes a thermostatic and humidistatic chamber, a temperature control module disposed therein, a rangefinder to be calibrated, a measured object, a standard rangefinder, and a distance adjustment module. The emitted light beams of the rangefinder to be calibrated and the standard rangefinder are both projected onto the measured object. The temperature control module adjusts the working temperature of the rangefinder to be calibrated, and the distance adjustment module adjusts the distances of the rangefinder to be calibrated and the standard rangefinder from the measured object. Under different working temperatures and different distances of the rangefinder to be calibrated and the standard rangefinder from the measured object, the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module of the rangefinder to be calibrated are obtained by measuring the conditions of the light beams on the measured object, and the rangefinder to be calibrated is calibrated. The present invention can achieve high-precision measurement at different temperatures.

Description

Technical Field

[0001] The present invention relates to the technical field of laser ranging, and in particular to a calibration system and method for an FMCW laser rangefinder. Background Art

[0002] FMCW (Frequency Modulated Continuous Wave) laser rangefinders have many advantages such as high precision, long distance, and anti-interference, and are increasingly used in high-precision measurement scenarios. Compared with TOF (Time of flight) optical ranging, FMCW laser ranging has an accuracy advantage of several orders of magnitude; compared with triangulation laser ranging, FMCW laser ranging not only has higher accuracy but also a farther detection range.

[0003] Currently, the calibration of laser rangefinders mostly uses a standard ruler as a reference. The readings yi of the standard ruler and the readings xi of the ruler to be measured are obtained by moving multiple steps, and then the fitting line yi = k*xi + b between the readings of the standard ruler and the readings of the ruler to be measured is obtained by the least squares method, and the laser rangefinder is calibrated according to the fitting line. However, this method is only applicable to scenarios where the temperature is constant or the measurement accuracy is low. When the temperature changes during measurement, the wavelength of the laser, the length of the optical chip waveguide, and the refractive index will all change due to thermal expansion and contraction, resulting in errors in the ranging results of the laser. At the same time, the exact temperature value cannot be measured by an external value, and the temperature measurement probe cannot enter the laser or the inside of the optical chip, and other variables are needed for indirect measurement. And when the coefficient of thermal expansion is 10^-5, a deviation of 10 um will occur for a distance of 1 m, which cannot meet the requirements of high-precision measurement. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a calibration system and method for an FMCW laser rangefinder, which can achieve high-precision measurement at different temperatures.

[0005] To solve the above technical problem, the present invention provides a calibration system for an FMCW laser rangefinder, including a temperature and humidity chamber, a temperature control module, a rangefinder to be calibrated, a measured object, a standard rangefinder, and a distance adjustment module.

[0006] The temperature control module, the rangefinder to be calibrated, the measured object, the standard rangefinder, and the distance adjustment module are all arranged in the temperature and humidity chamber. The outgoing light beams of the rangefinder to be calibrated and the standard rangefinder are both projected onto the measured object. The temperature control module adjusts the operating temperature of the rangefinder to be calibrated, and the distance adjustment module adjusts the distances of the rangefinder to be calibrated and the standard rangefinder from the measured object.

[0007] Under different working temperatures and different distances between the rangefinder to be calibrated, the standard rangefinder and the object to be measured, the phase temperature coefficient, wavelength temperature coefficient and optical chip temperature coefficient of the optical module of the rangefinder to be calibrated are obtained by measuring the situation of the light beam on the object to be measured, and the rangefinder to be calibrated is calibrated.

[0008] In an embodiment of the present invention, the distance adjustment module includes three two-dimensional adjustment frames and a displacement platform. The rangefinder to be calibrated, the object to be measured, and the standard rangefinder are respectively arranged on the three two-dimensional adjustment frames, and the two-dimensional adjustment frame provided with the object to be measured is arranged on the displacement platform;

[0009] The object to be measured is located between the rangefinder to be calibrated and the standard rangefinder, and the displacement platform adjusts the distances between the object to be measured and the rangefinder to be calibrated and the standard rangefinder by moving the object to be measured;

[0010] The three two-dimensional adjustment frames adjust the relative positions of the rangefinder to be calibrated, the object to be measured and the standard rangefinder, so that the outgoing light beams of the rangefinder to be calibrated and the standard rangefinder are parallel and perpendicular to the object to be measured.

[0011] In an embodiment of the present invention, it further includes an optical platform, which is arranged in the constant temperature and humidity chamber. The two two-dimensional adjustment frames provided with the rangefinder to be calibrated and the standard rangefinder are arranged on the optical platform, and the displacement platform provided with the object to be measured and one two-dimensional adjustment frame is arranged on the optical platform.

[0012] In an embodiment of the present invention, the rangefinder to be calibrated includes an optical module, a control and data acquisition and processing unit. The optical module includes a laser and an optical chip, and the laser and the optical chip respectively include temperature measurement probes;

[0013] The temperature control module is arranged on the surface of the rangefinder to be calibrated. When the temperature control module adjusts the temperature in the constant temperature and humidity chamber, the temperature measurement probe detects the working temperatures of the laser and the optical chip.

[0014] In an embodiment of the present invention, the outgoing light beam of the rangefinder to be calibrated is generated by the laser, and the beam generated by the laser is modulated using a non-linear sine wave.

[0015] In an embodiment of the present invention, the accuracy of the standard rangefinder is better than that of the rangefinder to be calibrated, and the accuracy of the temperature control module is less than or equal to 0.1 °C; the temperature of the constant temperature and humidity chamber is 26 °C ± 0.1 °C, the humidity is 50 ± 5% RH, the compressor of the constant temperature and humidity chamber is external, and the accuracy of the temperature measurement probe is less than or equal to 0.1 °C.

[0016] The present invention also provides a calibration method for an FMCW laser rangefinder, comprising the following steps:

[0017] Place the rangefinder to be calibrated, the object to be measured, and the standard rangefinder in a constant temperature and humidity chamber, and project the emitted light beams of the rangefinder to be calibrated and the standard rangefinder onto the object to be measured;

[0018] Adjust the operating temperature of the rangefinder to be calibrated, and adjust the distances of the rangefinder to be calibrated and the standard rangefinder from the object to be measured; under different operating temperatures and different distances of the rangefinder to be calibrated and the standard rangefinder from the object to be measured, obtain the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module of the rangefinder to be calibrated by measuring the situation of the light beam on the object to be measured, and calibrate the rangefinder to be calibrated.

[0019] In an embodiment of the present invention, the calibration method for the phase temperature coefficient dφ / dt of the optical module is specifically as follows:

[0020] Adjust the operating temperature of the rangefinder to be calibrated to cause a temperature change in the optical module of the rangefinder to be calibrated, and obtain the phase value Φ of the light beam of the rangefinder to be calibrated and the operating temperature value T at different operating temperatures;

[0021] After the temperature change of the overall adjustment reaches the preset value, use the least squares method to fit Φ and T to obtain a fitting curve, and take the slope of the fitting curve as the phase temperature coefficient dφ / dt of the optical module.

[0022] In an embodiment of the present invention, the calibration methods for the wavelength temperature coefficient dλ / dt and the optical chip temperature coefficient dL / dt are specifically as follows:

[0023] Move the object to be measured to adjust the distances of the object to be measured from the rangefinder to be calibrated and the standard rangefinder. Each time the object to be measured is moved, adjust the operating temperature of the rangefinder to be calibrated to cause a temperature change in the optical module of the rangefinder to be calibrated;

[0024] When moving the object to be measured and adjusting the operating temperature each time, obtain the displacement x(0) of the object to be measured and the distance value xd(0) of this movement, the displacement x(i) of the rangefinder to be calibrated and the distance value xd(i) of this movement, the displacement y(i) of the standard rangefinder and the distance value yd(i) of this movement, the temperature Tb of the laser in the current rangefinder to be calibrated, and the temperature Tc of the optical chip;

[0025] The displacement fitting function of the standard rangefinder and the distance fitting function of the standard rangefinder are obtained by least squares fitting. The slope k(Tb) of the displacement fitting function is taken as the wavelength λ of the laser beam emitted by the laser at the current temperature Tb of the laser, and the slope kd(Tc) of the distance fitting function is taken as the link length L of the optical chip at the current temperature Tc of the optical chip.

[0026] At different operating temperatures, the distances between the rangefinder to be calibrated and the standard rangefinder from the object to be measured are adjusted to obtain the slopes k(Tn) of different displacement fitting functions and the slopes kd(Tn) of different distance fitting functions.

[0027] Until the change in the adjusted operating temperature reaches a preset value, the fitting function of the slopes k(Tn) of different displacement fitting functions is obtained by least squares fitting, and the slope of the fitting function of the slopes k(Tn) of different displacement fitting functions is taken as the wavelength temperature coefficient dλ / dt; the fitting function of the slopes kd(Tn) of different distance fitting functions is obtained by least squares fitting, and the slope of the fitting function of the slopes kd(Tn) of different distance fitting functions is taken as the optical chip temperature coefficient dL / dt.

[0028] In an embodiment of the present invention, the calibration of the rangefinder to be calibrated is specifically as follows:

[0029] During the process of moving the object to be measured and adjusting the operating temperature, the wavelength of the laser beam emitted by the laser corresponding to the data with the smallest temperature fluctuation and the link length of the optical chip are selected as the initial wavelength λ0 of the laser beam emitted by the laser and the initial link length L0 of the optical chip, and the temperature with the smallest temperature fluctuation is taken as the initial operating temperature T0. Combining the phase temperature coefficient dφ / dt, wavelength temperature coefficient dλ / dt, and optical chip temperature coefficient dL / dt of the optical module, the calibration of the rangefinder to be calibrated is completed to obtain the calibrated rangefinder.

[0030] The above technical solution of the present invention has the following advantages compared with the prior art:

[0031] By designing and calculating the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module of the rangefinder to be calibrated, and calculating the measured value by combining the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module during the ranging process of the rangefinder, the rangefinder can achieve high-precision measurement at different temperatures, expanding the application range of the FMCW laser rangefinder and ensuring the output of high-precision measurement values. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] To make the content of the present invention easier to be clearly understood, the following further elaborates on the present invention in detail according to specific embodiments of the present invention in combination with the accompanying drawings, where:

[0033] Figure 1 is a structural block diagram of the system of the present invention,

[0034] Figure 2 is a schematic diagram of the sine wave of the sine wave modulated interference phase output,

[0035] Figure 3 is a calibration flow chart of the inventive method,

[0036] Figure 4 is a flow chart of adjusting the optical paths of the standard rangefinder and the rangefinder to be calibrated in the embodiment of the present invention. Specific Embodiments

[0037] The following further illustrates the present invention in combination with the accompanying drawings and specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the exemplified embodiments are not used as a limitation to the present invention.

[0038] Referring to Figure 1 As shown, the present invention discloses a calibration system for an FMCW laser rangefinder, including a constant temperature and humidity chamber, a temperature control module, a rangefinder to be calibrated, a measured object, a standard rangefinder, and a distance adjustment module. The temperature control module, the rangefinder to be calibrated, the measured object, the standard rangefinder, and the distance adjustment module are all arranged in the constant temperature and humidity chamber. The emitted light beams of the rangefinder to be calibrated and the standard rangefinder are both projected onto the measured object. The temperature control module adjusts the working temperature of the rangefinder to be calibrated, and the distance adjustment module adjusts the distances of the rangefinder to be calibrated and the standard rangefinder from the measured object; the constant temperature and humidity chamber is used to provide a stable test environment and avoid errors caused by temperature and humidity. The temperature control module is used to heat the rangefinder to be calibrated to change the temperature of the internal laser and optical chip (the actual temperature value is measured by a temperature measuring probe). The standard rangefinder serves as a standard tool to provide accurate displacement information. The measured object is a rigid and smooth object, and the distance measured by the rangefinder is the distance to the measured object. Under different working temperatures and different distances of the rangefinder to be calibrated and the standard rangefinder from the measured object, the phase temperature coefficient (dφ / dt), wavelength temperature coefficient (dλ / dt), and optical chip temperature coefficient (dL / dt) of the optical module of the rangefinder to be calibrated are obtained by measuring the situation of the light beam on the measured object, and the rangefinder to be calibrated is calibrated.

[0039] In this embodiment, the distance adjustment module includes three two-dimensional adjustment frames and a displacement platform. The rangefinder to be calibrated, the object to be measured, and the standard rangefinder are respectively arranged on the three two-dimensional adjustment frames. The two-dimensional adjustment frame provided with the object to be measured is arranged on the displacement platform. The object to be measured is located between the rangefinder to be calibrated and the standard rangefinder. The displacement platform adjusts the distance between the object to be measured and the rangefinder to be calibrated and the standard rangefinder by moving the object to be measured. The three two-dimensional adjustment frames adjust the relative positions of the rangefinder to be calibrated, the object to be measured, and the standard rangefinder, so that the outgoing light beams of the rangefinder to be calibrated and the standard rangefinder are parallel and perpendicular to the object to be measured. The displacement platform is provided with an adjustment motor, and under the control of the program, the adjustment motor can automatically adjust the displacement platform so that the moving direction of the displacement platform is parallel to the light beams of the rangefinder to be calibrated and the standard rangefinder. The two-dimensional adjustment frame is provided with an XY adjustment motor, and can automatically complete the adjustment to make the light beam parallel to the displacement platform and perpendicular to the object to be measured in cooperation with the algorithm.

[0040] In this embodiment, the calibration system of the FMCW laser rangefinder further includes an optical platform, which is arranged in the constant temperature and humidity chamber. The two two-dimensional adjustment frames provided with the rangefinder to be calibrated and the standard rangefinder are arranged on the optical platform. The displacement platform provided with the object to be measured and one two-dimensional adjustment frame is arranged on the optical platform. The optical platform is used to provide a stable base and reduce the influence of external vibration.

[0041] In this embodiment, the rangefinder to be calibrated includes an optical module, a control and data acquisition and processing unit. The optical module includes a laser and an optical chip, and the laser and the optical chip respectively include a temperature measurement probe. The temperature control module is attached to the surface of the rangefinder to be calibrated. When the temperature in the constant temperature and humidity chamber is adjusted by the temperature control module, the temperature measurement probe detects the operating temperatures of the laser and the optical chip.

[0042] The outgoing light beam of the rangefinder to be calibrated is generated by the laser, and the beam generated by the laser is modulated using a non-linear sine wave. As Figure 2 shown, the sine wave modulation interference phase output is still a sine wave. There will be a reference arm inside the optical chip. When the external distance remains unchanged and the temperature of the reference arm changes, thermal expansion and contraction will occur, resulting in changes in the reference arm. The change value of the phase average value is directly related to the temperature. Similarly, the temperature change value can be directly calculated based on the phase change value.

[0043] The angular frequency mean value |ωb| = Δω * ωmτ / π, the phase change value ΔΦ = 2π|ωb|t. When the distance remains unchanged, 2π|ωb| is a constant, and the time t depends on the optical path L. Therefore, the change in phase is directly linearly related to the temperature.

[0044] Displacement value = (phase / 2π) * wavelength λ, so the change in displacement is directly related to the wavelength; distance value = (phase of the measurement arm / phase of the reference arm) * length of the reference arm. Therefore, with the measurement arm unchanged, the distance value is directly related to the length of the reference arm.

[0045] In this embodiment, the accuracy of the standard rangefinder is better than that of the rangefinder to be calibrated, and the accuracy of the temperature control module is less than or equal to 0.1 °C; the temperature of the constant temperature and humidity chamber is 26 °C ± 0.1 °C, the humidity is 50 ± 5% RH, the compressor of the constant temperature and humidity chamber is external, the air outlet of the constant temperature and humidity chamber does not face the optical platform, the wind speed is < 0.1 m / s, and the accuracy of the temperature measurement probe needs to be less than or equal to 0.1 °C.

[0046] As Figure 3 and Figure 4 shown, the present invention also discloses a calibration method for an FMCW laser rangefinder, including the following steps:

[0047] S1: Place the rangefinder to be calibrated, the object to be measured, and the standard rangefinder in a constant temperature and humidity chamber, and project the outgoing beams of the rangefinder to be calibrated and the standard rangefinder onto the object to be measured.

[0048] S2: Adjust the operating temperature of the rangefinder to be calibrated, and adjust the distances of the rangefinder to be calibrated and the standard rangefinder from the object to be measured; under different operating temperatures and different distances of the rangefinder to be calibrated and the standard rangefinder from the object to be measured, obtain the phase temperature coefficient (dφ / dt), wavelength temperature coefficient (dλ / dt), and optical chip temperature coefficient (dL / dt) of the optical module of the rangefinder to be calibrated by measuring the situation of the light beam on the object to be measured, and calibrate the rangefinder to be calibrated.

[0049] S2-1: The calibration method for the phase temperature coefficient dφ / dt of the optical module is specifically as follows:

[0050] S2-1-1: Keep the displacement platform stationary, and adjust the operating temperature of the rangefinder to be calibrated through the temperature control module in a static state to cause a temperature change in the optical module of the rangefinder to be calibrated. The change gradient of the operating temperature is controlled at 0.1 °C / min (too large a gradient will cause other non-linear effects). Obtain the phase value Φ of the light beam of the rangefinder to be calibrated and the operating temperature value T at different operating temperatures. Specifically, in this embodiment, the phase value Φ of the interferometer and the temperature value T of the optical chip temperature measurement probe are recorded once per second.

[0051] S2-1-2: After the temperature change of the overall adjustment reaches the preset value (10 °C in this embodiment), the least squares method is used to fit Φ and T to obtain the fitting curve Φ = dΦ / dt * T + b. The constant term b will fluctuate and change during actual use, but it does not affect the slope dΦ / dt. The slope of the fitting curve is used as the phase temperature coefficient dφ / dt of the optical module.

[0052] S2-2: The calibration methods for the wavelength temperature coefficient dλ / dt and the optical chip temperature coefficient dL / dt are specifically as follows:

[0053] S2-2-1: Move the displacement platform, and the temperature control module adjusts the temperature. The displacement platform is moved once and the temperature is adjusted once in each round. The adjustment range needs to be controlled within a temperature fluctuation of <0.01 °C per round to ensure the temperature stability within each round.

[0054] Move the object under test to adjust the distances between the object under test and the rangefinder to be calibrated and the standard rangefinder. Each time the object under test is moved, the operating temperature of the rangefinder to be calibrated is adjusted to cause a temperature change in the optical module of the rangefinder to be calibrated;

[0055] S2-2-2: When moving the object under test and adjusting the operating temperature each time, obtain the displacement x(0) of the object under test and the distance value xd(0) of this movement, the displacement x(i) of the rangefinder to be calibrated and the distance value xd(i) of this movement, the displacement y(i) of the standard rangefinder and the distance value yd(i) of this movement, the temperature Tb of the laser in the current rangefinder to be calibrated, and the temperature Tc of the optical chip.

[0056] S2-2-3: Use the least squares method to fit to obtain the displacement fitting function of the standard rangefinder as y(i) = k(Tb) * (x(i) - x(0)) + b1 and the distance fitting function of the standard rangefinder as yd(i) = kd(Tc) * (xd(i) - xd(0)) + b2. The slope k(Tb) of the displacement fitting function is used as the wavelength λ of the emitted light beam of the laser at the current temperature Tb of the laser, and the slope kd(Tc) of the distance fitting function is used as the link length L of the optical chip at the current temperature Tc of the optical chip.

[0057] S2-2-4: Adjust the temperature of the temperature control module to continue the next round. At different operating temperatures, adjust the distances between the rangefinder to be calibrated and the standard rangefinder and the object under test to obtain the slopes k(Tn) of different displacement fitting functions and the slopes kd(Tn) of different distance fitting functions;

[0058] S2-2-5: After the adjusted working temperature change reaches the preset value (10 °C in this embodiment), use the least squares method to fit the slopes k(Tn) of different displacement fitting functions to obtain the fitting function λ = dλ / dt * Tn + bλ of the slopes k(Tn) of different displacement fitting functions, and use the slope dλ / dt of the fitting function of the slopes k(Tn) of different displacement fitting functions as the wavelength temperature coefficient dλ / dt; use the least squares method to fit the slopes kd(Tn) of different distance fitting functions to obtain the fitting function L = dL / dt * Tn + bl of the slopes kd(Tn) of different distance fitting functions, and use the slope dL / dt of the fitting function of the slopes kd(Tn) of different distance fitting functions as the optical chip temperature coefficient dL / dt.

[0059] S2-3: Calibrate the rangefinder to be calibrated, specifically:

[0060] During the process of moving the object to be measured and adjusting the working temperature, select the wavelength of the outgoing beam of the laser and the link length of the optical chip corresponding to the data when the temperature fluctuation is the smallest as the initial wavelength λ0 of the outgoing beam of the laser and the initial link length L0 of the optical chip, and use the temperature when the temperature fluctuation is the smallest as the initial working temperature T0 (because the temperatures corresponding to λ and L are measured by two temperature sensors, so it is necessary to map them to the same temperature according to the temperature coefficients of λ and L). dΦ / dt is mainly used to calculate the accurate temperature value inversely, so the initial phase Φ0 is not required. Combine the phase temperature coefficient dφ / dt, wavelength temperature coefficient dλ / dt, and optical chip temperature coefficient dL / dt of the optical module to complete the calibration of the rangefinder to be calibrated to obtain the calibrated rangefinder. In this embodiment, write the phase temperature coefficient (dφ / dt), wavelength temperature coefficient (dλ / dt), optical chip temperature coefficient (dL / dt), initial wavelength λ0 of the outgoing beam of the laser, initial link length L0 of the optical chip, and initial working temperature T0 of the optical module into the rangefinder to be calibrated to complete the calibration.

[0061] When using the calibrated rangefinder for ranging, the calibrated rangefinder will record the initial phase Φ0 every time it is initially powered on. Calculate the temperature change value ΔT according to the phase change value ΔΦ during ranging and the phase temperature coefficient dΦ / dt of the optical module. Calculate the current accurate wavelength value using the temperature change value ΔT and the wavelength temperature coefficient dλ / dt. Calculate the current link length of the optical chip using the temperature change value ΔT and the optical chip temperature coefficient dL / dt. Calculate the accurate distance measurement value according to the current accurate wavelength value and the current link length of the optical chip.

[0062] The present invention has the following advantages compared with the prior art:

[0063] 1. The present invention designs and calculates the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module of the rangefinder to be calibrated. Compared with the simple linear fitting in the prior art, the internal temperature of the optical module can be accurately calculated through multiple calibrated variables, and then the optical module parameters can be accurately calculated through the temperature change value, so as to calculate an accurate measurement distance value, enabling the rangefinder to achieve high-precision measurement at different temperatures, expanding the application range of the FMCW laser rangefinder, and ensuring high-precision output.

[0064] 2. The present invention calibrates multiple variables such as the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module. At the same time, during the calibration process of multiple variables, all devices are placed on an optical platform, and the optical platform is placed in a constant temperature and humidity chamber to minimize other variables as much as possible, making the calibration accuracy higher.

[0065] 3. A temperature measurement probe is set inside the optical module of the rangefinder to be calibrated. Compared with the traditional external or mainboard temperature measurement, the working temperature data of the optical module is more accurate, and the calibration accuracy is greatly improved.

[0066] 4. The verticality of the emitted light beam is adjusted through the distance adjustment module, and the calibration process is flexible and easy to operate.

[0067] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0068] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of processes and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in one Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0069] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including instruction means embodying the functionality specified in the flowchart Figure 1 one or more flowcharts and / or boxes Figure 1 specified in the function of the box or boxes.

[0070] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide steps for implementing the functionality specified in the flowchart Figure 1 one or more flowcharts and / or boxes Figure 1 steps specified in the function of the box or boxes.

[0071] Obviously, the above embodiments are merely examples for clear illustration and are not limitations on the implementation. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A calibration system for an FMCW laser rangefinder, characterized in that: It includes a thermostatic and humidistatic chamber, a temperature control module, a rangefinder to be calibrated, a measured object, a standard rangefinder, and a distance adjustment module. The temperature control module, the rangefinder to be calibrated, the measured object, the standard rangefinder, and the distance adjustment module are all arranged inside the thermostatic and humidistatic chamber. The emitted light beams of the rangefinder to be calibrated and the standard rangefinder are both projected onto the measured object. The temperature control module adjusts the operating temperature of the rangefinder to be calibrated, and the distance adjustment module adjusts the distances of the rangefinder to be calibrated and the standard rangefinder from the measured object. Under different operating temperatures and different distances of the rangefinder to be calibrated and the standard rangefinder from the measured object, the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module of the rangefinder to be calibrated are obtained by measuring the situation of the light beam on the measured object, and the rangefinder to be calibrated is calibrated. The calibration of the rangefinder to be calibrated is specifically as follows: During the process of moving the measured object and adjusting the operating temperature, the wavelength of the emitted light beam of the laser and the link length of the optical chip corresponding to the data when the temperature fluctuation is the smallest are selected as the wavelength of the emitted light beam of the initial laser and the link length of the initial optical chip, and the temperature when the temperature fluctuation is the smallest is used as the initial operating temperature. Combining the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module, the calibration of the rangefinder to be calibrated is completed to obtain the calibrated rangefinder.

2. The calibration system of the FMCW laser rangefinder according to claim 1, characterized in that: The distance adjustment module includes three two-dimensional adjustment frames and a displacement platform. The rangefinder to be calibrated, the measured object, and the standard rangefinder are respectively arranged on the three two-dimensional adjustment frames, and the two-dimensional adjustment frame provided with the measured object is arranged on the displacement platform. The measured object is located between the rangefinder to be calibrated and the standard rangefinder, and the displacement platform adjusts the distances of the measured object from the rangefinder to be calibrated and the standard rangefinder by moving the measured object. The three two-dimensional adjustment frames adjust the relative positions of the rangefinder to be calibrated, the measured object, and the standard rangefinder, so that the emitted light beams of the rangefinder to be calibrated and the standard rangefinder are parallel and perpendicular to the measured object.

3. The calibration system of the FMCW laser rangefinder according to claim 2, characterized in that: It also includes an optical platform. The optical platform is arranged inside the thermostatic and humidistatic chamber. The two two-dimensional adjustment frames provided with the rangefinder to be calibrated and the standard rangefinder are arranged on the optical platform, and the displacement platform provided with the measured object and one two-dimensional adjustment frame is arranged on the optical platform.

4. The calibration system of the FMCW laser rangefinder according to any one of claims 1-3, characterized in that: The rangefinder to be calibrated includes an optical module, a control and data acquisition and processing unit. The optical module includes a laser and an optical chip, and the laser and the optical chip respectively include temperature measurement probes. The temperature control module is arranged on the surface of the rangefinder to be calibrated. When the temperature control module adjusts the temperature inside the thermostatic and humidistatic chamber, the temperature measurement probes detect the operating temperatures of the laser and the optical chip.

5. The calibration system of the FMCW laser rangefinder according to claim 4, characterized in that: The emitted light beam of the rangefinder to be calibrated is generated by the laser, and the beam generated by the laser uses non-linear sine wave modulation.

6. The calibration system of the FMCW laser rangefinder according to claim 4, characterized in that: The accuracy of the standard rangefinder is better than that of the rangefinder to be calibrated, and the accuracy of the temperature control module is less than or equal to 0.1 °C; the temperature of the thermostatic and humidistatic chamber is 26 °C ± 0.1 °C, the humidity is 50 ± 5% RH, the compressor of the thermostatic and humidistatic chamber is external, and the accuracy of the temperature measurement probe is less than or equal to 0.1 °C.

7. A calibration method for an FMCW laser rangefinder, characterized in that, Including: Place the rangefinder to be calibrated, the object to be measured, and the standard rangefinder in the thermostatic and humidistatic chamber, and project the outgoing light beams of the rangefinder to be calibrated and the standard rangefinder onto the object to be measured; Adjust the operating temperature of the rangefinder to be calibrated, and adjust the distances of the rangefinder to be calibrated and the standard rangefinder from the object to be measured; under different operating temperatures and different distances of the rangefinder to be calibrated and the standard rangefinder from the object to be measured, obtain the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module of the rangefinder to be calibrated by measuring the light beam situation on the object to be measured, and calibrate the rangefinder to be calibrated; The calibration of the rangefinder to be calibrated is specifically as follows: during the process of moving the object to be measured and adjusting the operating temperature, select the wavelength of the outgoing light beam of the laser and the link length of the optical chip corresponding to the data when the temperature fluctuation is the smallest as the wavelength of the outgoing light beam of the initial laser and the link length of the initial optical chip, and use the temperature when the temperature fluctuation is the smallest as the initial operating temperature, and complete the calibration of the rangefinder to be calibrated in combination with the phase temperature coefficient, wavelength temperature coefficient, and optical chip temperature coefficient of the optical module to obtain the calibrated rangefinder.

8. The calibration method of the FMCW laser rangefinder according to claim 7, characterized in that: The calibration method of the phase temperature coefficient dφ / dt of the optical module is specifically as follows: Adjust the operating temperature of the rangefinder to be calibrated to cause a temperature change in the optical module of the rangefinder to be calibrated, and obtain the phase value Φ of the light beam of the rangefinder to be calibrated and the operating temperature value T at different operating temperatures; After the temperature change of the overall adjustment reaches the preset value, use the least squares method to fit Φ and T to obtain a fitting curve, and use the slope of the fitting curve as the phase temperature coefficient dφ / dt of the optical module.

9. The calibration method of the FMCW laser rangefinder according to claim 7, characterized in that: The calibration methods of the wavelength temperature coefficient dλ / dt and the optical chip temperature coefficient dL / dt are specifically as follows: Move the object to be measured to adjust the distances of the object to be measured from the rangefinder to be calibrated and the standard rangefinder, and adjust the operating temperature of the rangefinder to be calibrated each time the object to be measured is moved to cause a temperature change in the optical module of the rangefinder to be calibrated; When moving the object to be measured and adjusting the operating temperature each time, obtain the displacement x(0) of the object to be measured and the distance value xd(0) of this movement, the displacement x(i) of the rangefinder to be calibrated and the distance value xd(i) of this movement, the displacement y(i) of the standard rangefinder and the distance value yd(i) of this movement, the temperature Tb of the laser in the current rangefinder to be calibrated, and the temperature Tc of the optical chip. The displacement fitting function of the standard rangefinder and the distance fitting function of the standard rangefinder are obtained by least squares fitting. The slope k(Tb) of the displacement fitting function is used as the wavelength λ of the laser beam emitted by the laser at the current temperature Tb of the laser, and the slope kd(Tc) of the distance fitting function is used as the link length L of the optical chip at the current temperature Tc of the optical chip. At different operating temperatures, the distances between the rangefinder to be calibrated and the standard rangefinder from the object to be measured are adjusted to obtain the slopes k(Tn) of different displacement fitting functions and the slopes kd(Tn) of different distance fitting functions. Until the change in the adjusted operating temperature reaches a preset value, the least squares method is used to fit the slopes k(Tn) of different displacement fitting functions to obtain the fitting function of the slopes k(Tn) of different displacement fitting functions, and the slope of the fitting function of the slopes k(Tn) of different displacement fitting functions is used as the wavelength temperature coefficient dλ / dt; the least squares method is used to fit the slopes kd(Tn) of different distance fitting functions to obtain the fitting function of the slopes kd(Tn) of different distance fitting functions, and the slope of the fitting function of the slopes kd(Tn) of different distance fitting functions is used as the optical chip temperature coefficient dL / dt.

Images