Laser Doppler velocimeter indication error calibration device and method

Abstract

The present invention provides a laser Doppler velocimeter indication error calibration device to address the problems of complex structure, low upper reference speed limit, and danger in the prior art. The device comprises a single-frequency laser, a first wavelength meter, a second wavelength meter, a 1×2 fiber optic beam splitter, a 2×1 fiber optic coupler, and a fiber optic isolator. The device features a simple structure, low cost, a high safety factor, and a high reference speed. Furthermore, the present invention provides a laser Doppler velocimeter indication error calibration method.

Description

Technical Field

[0001] The present invention relates to the field of laser measurement and calibration, and in particular to a device and method for calibrating the indication error of a laser Doppler velocimeter. Background Art

[0002] In high-speed measurement, laser Doppler velocimetry is a non-contact measurement device that uses the laser Doppler effect to measure the speed of an object. Due to its excellent spatial resolution and good dynamic response capabilities, the device has been increasingly used in various fields in recent years. The test principle diagram is shown below. Figure 1 shown.

[0003] Currently, laser Doppler velocimeters are primarily calibrated using a standard source method. Since velocity is not a fundamental physical quantity but rather a physically derived quantity, it must be generated through other methods, such as the free-fall method, the standard rotational speed method, and the impact calibration method. These methods generate corresponding reference velocities, providing the "standard" velocity required by the laser Doppler velocimeter and completing the velocimeter calibration. However, existing calibration methods have the following disadvantages: 1. The equipment required to generate the reference velocity is complex and costly. The free-fall method requires an object to fall freely from a height, requiring highly accurate velocity measurement equipment to simultaneously measure the falling velocity of the object and the device being calibrated; the standard rotational speed method generally requires the use of a precision centrifuge to generate the standard rotational speed; and the impact calibration method requires a complex impact machine. 2. The upper limit of the reference velocity that existing calibration methods can provide is limited. Currently, the speeds that can be generated by generating a moving object are in the hundreds of meters per second range, and reference speeds exceeding kilometers per second are difficult to achieve. 3. Existing calibration methods require a high-speed moving object for high-speed calibration, which poses significant safety risks.

[0004] In view of the above problems, there is an urgent need to provide a new laser Doppler velocimeter indication error calibration device and method to solve the problems of the existing technology such as complex and high cost of the device, low reference speed, and great safety hazards. Summary of the Invention

[0005] In view of this, the present invention provides a laser Doppler velocimeter indication error calibration device with simple structure, low cost, high safety factor and high reference speed.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] A laser Doppler velocimeter indication error calibration device comprises: a single-frequency laser, a first wavelength meter, a second wavelength meter, a 1×2 optical fiber beam splitter, a 2×1 optical fiber coupler, and an optical fiber isolator; the single-frequency laser is connected to the main signal end of the 2×1 optical fiber coupler; the first branch signal end of the 2×1 optical fiber coupler is connected to the second wavelength meter, and the second branch signal end of the 2×1 optical fiber coupler is connected to the input end of the optical fiber isolator; the laser Doppler velocimeter to be tested is connected to the main signal end of the 1×2 optical fiber beam splitter, the first branch signal end of the 1×2 optical fiber beam splitter is connected to the output end of the optical fiber isolator, and the second branch signal end of the 1×2 optical fiber beam splitter is connected to the first wavelength meter; the optical fiber isolator is a unidirectional single-pass device; the first wavelength meter is used to detect the wavelength λ0 of the output light of the laser Doppler velocimeter to be tested; and the second wavelength meter is used to detect the wavelength λ1 of the light generated by the single-frequency laser.

[0008] Preferably, the single-frequency laser is a wavelength-tunable single-frequency laser, which is used to generate corresponding echo simulation signal light according to the laser Doppler velocimeter to be measured.

[0009] Preferably, the wavelength-tunable single-frequency laser is a distributed feedback straight-cavity (DFB) fiber laser.

[0010] Preferably, the laser Doppler velocimeter to be measured obtains the velocity measurement indication u according to the echo simulation signal light output by the single-frequency laser S The indication error of the laser Doppler velocimeter to be measured is calculated based on the speed measurement indication, the wavelength λ0 of the light emitted by the laser Doppler velocimeter to be measured detected by the first wavelength meter, and the wavelength λ1 of the light generated by the single-frequency laser detected by the second wavelength meter.

[0011] The invention provides a method for calibrating the indication error of a laser Doppler velocimeter with low cost, high safety factor and high reference speed.

[0012] To achieve this purpose, the present invention adopts the following technical solutions:

[0013] A method for calibrating an indication error of a laser Doppler velocimeter comprises the following steps:

[0014] Step S1, selecting or setting a first wavelength meter, a second wavelength meter, a fiber beam splitter, a fiber coupler, a fiber isolator, and a single-frequency laser according to a velocity calibration range and an operating wavelength of the laser Doppler velocimeter to be measured;

[0015] Step S2: constructing a laser Doppler velocimeter indication error calibration device as described above, and starting the laser Doppler velocimeter to be tested and the single-frequency laser to preheat the equipment;

[0016] Step S3: The outgoing light of the laser Doppler velocimeter to be measured enters the first wavelength meter through the 1×2 optical fiber beam splitter to complete the working wavelength detection and obtain the wavelength λ0;

[0017] Step S4: The single-frequency laser output light is split into two beams through a 2×1 fiber coupler. One beam enters the second wavelength meter to complete the simulated echo wavelength detection and obtain the wavelength λ1; the other beam enters the laser Doppler velocimeter through a fiber isolator and a 1×2 fiber beam splitter to obtain the speed measurement value u of the laser Doppler velocimeter. S ;

[0018] Step S5: Calculate reference speed u B， ;

[0019] Step S6: Calculate the indication error of the laser Doppler velocimeter to be measured.

[0020] Preferably, in step S5, the formula Calculate the reference speed u B , where c represents the speed of light in vacuum. The formula is calculated with the speed of the target approaching the laser Doppler velocimeter as the positive direction.

[0021] Preferably, in step S6, the laser Doppler velocimeter indication error e to be measured is (u S -u B ) / u B .

[0022] Preferably, in step S1, according to the speed calibration point and the wavelength of the laser Doppler velocimeter to be measured, the formula The wavelength of the single-frequency laser is obtained by calculation, wherein c represents the speed of light in a vacuum, and the speed of the target when approaching the laser Doppler velocimeter is used as the positive direction in the calculation formula.

[0023] The present invention also provides a laser Doppler velocimeter with a simple structure, low cost, high safety factor, high measurable speed, and self-calibration. To achieve this purpose, the present invention adopts the following technical solutions:

[0024] A laser Doppler velocimeter is provided with the laser Doppler velocimeter indication error calibration device as described above.

[0025] A laser Doppler velocimeter uses the above-mentioned laser Doppler velocimeter indication error calibration method.

[0026] The beneficial effects of the present invention are:

[0027] The Doppler velocity measurement system calibration device and method of the present invention eliminates the need for a moving object and only requires a single-frequency laser to provide the corresponding wavelength. Compared to traditional methods, the calibration device has a simpler structure and lower costs. This calibration scheme employs an echo simulation method, eliminating the need to accelerate the object to the corresponding speed, resulting in a higher safety factor for the calibration device. The calibration scheme of the present invention enables speed calibration of 10 km / s. Based on the correspondence between the velocimeter's operating wavelength and the echo simulation wavelength, the present invention enables calibration at different speeds by simply changing the output wavelength of the single-frequency laser, resulting in a relatively low level of implementation. The scheme of the present invention can be used to calibrate the indication error of a laser Doppler velocimeter, further improving the measurement system of laser Doppler velocimeters. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a schematic diagram of the principle of laser Doppler velocimetry.

[0029] Figure 2 This is a schematic diagram of a laser Doppler velocimeter indication error calibration device provided by a specific embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of a method for calibrating the indication error of a laser Doppler velocimeter provided by a specific embodiment of the present invention.

[0031] In the figure, 1, laser Doppler velocimeter to be measured; 2, single-frequency laser; 3, first wavelength meter; 4, second wavelength meter; 5, 1×2 fiber beam splitter; 6, 2×1 fiber coupler; 7, fiber isolator; DETAILED DESCRIPTION

[0032] A laser Doppler velocimeter indication error calibration device comprises: a single-frequency laser 2, a first wavelength meter 3, a second wavelength meter 4, a 1×2 optical fiber beam splitter 5, a 2×1 optical fiber coupler 6, and an optical fiber isolator 7; the single-frequency laser 2 is connected to the main signal end of the 2×1 optical fiber coupler 6; the first signal-dividing end of the 2×1 optical fiber coupler 6 is connected to the second wavelength meter 4, and the second signal-dividing end of the 2×1 optical fiber coupler 6 is connected to the input end of the optical fiber isolator 7; the laser Doppler velocimeter 1 to be tested is connected to the main signal end of the 1×2 optical fiber beam splitter 5, the first signal-dividing end of the 1×2 optical fiber beam splitter 5 is connected to the output end of the optical fiber isolator 7, and the second signal-dividing end of the 1×2 optical fiber beam splitter 5 is connected to the first wavelength meter 3; the optical fiber isolator 7 is a unidirectional, single-pass device; the first wavelength meter 3 is used to detect the wavelength λ0 of the output light of the laser Doppler velocimeter 1 to be tested; and the second wavelength meter 4 is used to detect the wavelength λ1 of the light generated by the single-frequency laser 2.

[0033] Preferably, the single-frequency laser is a wavelength-tunable single-frequency laser 2, which is used to generate corresponding echo simulation signal light according to the laser Doppler velocimeter 1 to be measured.

[0034] Preferably, the wavelength-tunable single-frequency laser 2 is a distributed feedback straight-cavity (DFB) fiber laser.

[0035] Preferably, the laser Doppler velocimeter 1 to be measured obtains the velocity measurement indication u according to the echo simulation signal light output by the single-frequency laser 2. S The indication error of the laser Doppler velocimeter 1 to be measured is calculated based on the speed measurement indication, the wavelength λ0 of the light emitted by the laser Doppler velocimeter 1 to be measured detected by the first wavelength meter 3, and the wavelength λ1 of the light generated by the single-frequency laser 2 to be measured detected by the second wavelength meter 4.

[0036] The invention provides a method for calibrating the indication error of a laser Doppler velocimeter with low cost, high safety factor and high reference speed.

[0037] To achieve this purpose, the present invention adopts the following technical solutions:

[0038] A method for calibrating an indication error of a laser Doppler velocimeter comprises the following steps:

[0039] Step S1, selecting or setting a first wavelength meter 3, a second wavelength meter 4, a fiber beam splitter, a fiber coupler, a fiber isolator 7, and a single-frequency laser 2 according to a velocity calibration range and an operating wavelength of the laser Doppler velocimeter 1 to be measured;

[0040] Step S2: constructing a laser Doppler velocimeter indication error calibration device as described above, turning on the laser Doppler velocimeter 1 and the single-frequency laser 2 to be tested to preheat the equipment;

[0041] Step S3: The outgoing light of the laser Doppler velocimeter 1 to be measured enters the first wavelength meter 3 through the 1×2 optical fiber beam splitter 5 to complete the working wavelength detection and obtain the wavelength λ0;

[0042] Step S4: The light emitted by the single-frequency laser 2 is split into two beams through the 2×1 fiber coupler 6. One beam enters the second wavelength meter 4 to complete the simulated echo wavelength detection and obtain the wavelength λ1; the other beam enters the laser Doppler velocimeter through the fiber isolator 7 and the 1×2 fiber beam splitter 5 to obtain the speed measurement value u of the laser Doppler velocimeter. S ;

[0043] Step S5: Calculate reference speed u B， ;

[0044] Step S6: Calculate the indication error of the laser Doppler velocimeter 1 to be measured.

[0045] Preferably, in step S5, the formula Calculate the reference speed u B , where c represents the speed of light in vacuum. The formula is calculated with the speed of the target approaching the laser Doppler velocimeter as the positive direction.

[0046] Preferably, in step S6, the indication error e of the laser Doppler velocimeter 1 to be measured is (u S -u B ) / u B .

[0047] Preferably, in step S1, according to the speed calibration point and the wavelength of the emitted light of the laser Doppler velocimeter 1 to be measured, the formula The wavelength of the single-frequency laser 2 is calculated, wherein c represents the speed of light in a vacuum, and the speed of the target approaching the laser Doppler velocimeter is used as the positive direction in the calculation formula.

[0048] When calibrating a laser Doppler velocimeter, the velocity measurement range and operating wavelength of the velocimeter are determined. According to the formula The wavelength range for echo simulation can be calculated. For example, if the operating wavelength of a laser Doppler velocimeter is 1550 nm (i.e., λ0 = 1550 nm), the velocity calibration range is 0-10 km / s, and the velocity direction is away from the laser Doppler velocimeter, then according to the formula, the echo simulation wavelength range is (1550-1550.1) nm. This means that the output wavelength adjustment range of the single-frequency laser, λ1, is (1550-1550.1) nm. By setting different single-frequency laser output wavelengths, different velocity calibration points can be constructed.

[0049] The present invention also provides a laser Doppler velocimeter with a simple structure, low cost, high safety factor, high measurable speed, and self-calibration. To achieve this purpose, the present invention adopts the following technical solutions:

[0050] A laser Doppler velocimeter is provided with the laser Doppler velocimeter indication error calibration device as described above.

[0051] A laser Doppler velocimeter uses the above-mentioned laser Doppler velocimeter indication error calibration method.

[0052] The Doppler velocity measurement system calibration device and method of the present invention eliminates the need for a moving object and only requires a single-frequency laser to provide the corresponding wavelength. Compared to traditional methods, the calibration device has a simpler structure and lower costs. This calibration scheme employs an echo simulation method, eliminating the need to accelerate the object to the corresponding speed, resulting in a higher safety factor for the calibration device. The calibration scheme of the present invention enables speed calibration of 10 km / s. Based on the correspondence between the velocimeter's operating wavelength and the echo simulation wavelength, the present invention enables calibration at different speeds by simply changing the output wavelength of the single-frequency laser, resulting in a relatively low level of implementation. The scheme of the present invention can be used to calibrate the indication error of a laser Doppler velocimeter, further improving the measurement system of laser Doppler velocimeters.

[0053] In addition, it will be appreciated by those skilled in the art that example embodiments are provided to make this disclosure comprehensive and to fully convey its scope to those skilled in the art. Many specific details (such as examples of specific components, devices, and methods) are given to provide a comprehensive understanding of this disclosure. It will be understood by those skilled in the art that it is not necessary to adopt specific details, that example embodiments can be implemented in many different forms, and that example embodiments should not be construed as limiting the scope of this disclosure. In some example embodiments, well-known device structures and well-known technologies are not described in detail.

Claims

1. A laser Doppler velocimeter indication error calibration device, characterized in that: include: A single-frequency laser, a first wavelength meter, a second wavelength meter, a 1×2 fiber beam splitter, a 2×1 fiber coupler, and a fiber isolator are provided. The single-frequency laser is connected to the main signal end of the 2×1 fiber coupler. The first signal-drop end of the 2×1 fiber coupler is connected to the second wavelength meter, and the second signal-drop end of the 2×1 fiber coupler is connected to the input end of the fiber isolator. The laser Doppler velocimeter to be tested is connected to the main signal end of the 1×2 fiber beam splitter, the first signal-drop end of the 1×2 fiber beam splitter is connected to the output end of the fiber isolator, and the second signal-drop end of the 1×2 fiber beam splitter is connected to the first wavelength meter. The fiber isolator is a unidirectional, single-pass device. The first wavelength meter is used to detect the wavelength λ0 of the output light of the laser Doppler velocimeter to be tested. The second wavelength meter is used to detect the wavelength λ1 of the light generated by the single-frequency laser.

2. The laser Doppler velocimeter indication error calibration device according to claim 1, characterized in that: The single-frequency laser is a wavelength-tunable single-frequency laser, which is used to generate corresponding echo simulation signal light according to the laser Doppler velocimeter to be measured.

3. The laser Doppler velocimeter indication error calibration device according to claim 2, characterized in that: The wavelength-tunable single-frequency laser is a distributed feedback straight cavity (DFB) fiber laser.

4. The laser Doppler velocimeter indication error calibration device according to claim 1, characterized in that: The laser Doppler velocimeter to be measured obtains the velocity measurement indication u according to the echo simulation signal light output by the single-frequency laser S The indication error of the laser Doppler velocimeter to be measured is calculated based on the speed measurement indication, the wavelength λ0 of the light emitted by the laser Doppler velocimeter to be measured detected by the first wavelength meter, and the wavelength λ1 of the light generated by the single-frequency laser detected by the second wavelength meter.

5. A method for calibrating the indication error of a laser Doppler velocimeter, characterized in that: The following steps are involved: Step S1, selecting or setting a first wavelength meter, a second wavelength meter, a fiber beam splitter, a fiber coupler, a fiber isolator, and a single-frequency laser according to a velocity calibration range and an operating wavelength of the laser Doppler velocimeter to be measured; Step S2: constructing a laser Doppler velocimeter indication error calibration device according to any one of claims 1 to 4, and starting the laser Doppler velocimeter to be tested and the single-frequency laser to preheat the equipment; Step S3: The outgoing light of the laser Doppler velocimeter to be measured enters the first wavelength meter through the 1×2 optical fiber beam splitter to complete the working wavelength detection and obtain the wavelength λ0; Step S4: The single-frequency laser output light is split into two beams through a 2×1 fiber coupler. One beam enters the second wavelength meter to complete the simulated echo wavelength detection and obtain the wavelength λ1; the other beam enters the laser Doppler velocimeter through a fiber isolator and a 1×2 fiber beam splitter to obtain the speed measurement value u of the laser Doppler velocimeter. S ; Step S5: Calculate reference speed u B， ; Step S6: Calculate the indication error of the laser Doppler velocimeter to be measured.

6. A method for calibrating the indication error of a laser Doppler velocimeter according to claim 5, characterized in that: In step S5, the formula Calculate the reference speed u B , where c represents the speed of light in vacuum. The formula is calculated with the speed of the target approaching the laser Doppler velocimeter as the positive direction.

7. The method for calibrating the indication error of a laser Doppler velocimeter according to claim 5, wherein: In step S6, the laser Doppler velocimeter indication error e=(u S -u B ) / u B .

8. The method for calibrating the indication error of a laser Doppler velocimeter according to claim 5, wherein: In step S1, according to the speed calibration point and the wavelength of the laser Doppler velocimeter to be measured, the formula The wavelength of the single-frequency laser is obtained by calculation, wherein c represents the speed of light in a vacuum, and the speed of the target when approaching the laser Doppler velocimeter is used as the positive direction in the calculation formula.

9. A laser Doppler velocimeter, characterized in that: A laser Doppler velocimeter indication error calibration device according to any one of claims 1 to 4.

10. A laser Doppler velocimeter, characterized in that: The method applies a laser Doppler velocimeter indication error calibration method as described in any one of claims 5 to 8.

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