A dual feedback spectral detection method

Abstract

The application discloses a double-feedback spectrum detection method applied to a Fourier transform spectrometer, which comprises the following steps: measuring a moving mirror by using a grating ruler and obtaining a displacement A of the moving mirror, and simultaneously measuring the moving mirror by using a laser and obtaining a displacement A of the moving mirror; judging whether the difference between the displacement A and the displacement A is less than an error threshold value; if the difference is less than the error threshold value, outputting the displacement A; and if the difference is greater than or equal to the error threshold value, outputting the displacement A and determining that the laser measurement is abnormal. The grating ruler is arranged to perform supplementary measurement, and the measurement result is compared with the result measured by the laser in real time, so that the error measurement data of the laser can be found in time and replaced, thereby ensuring that the result of the displacement of the moving mirror is always correct, and the reliability of the measurement result is improved, and the damage of the moving mirror to the measuring instrument caused by the error movement of the moving mirror due to the output of the error data parameter is avoided.

Description

Technical Field

[0001] The present invention mainly relates to the technical field of spectrometers, and in particular to a double-feedback spectrum detection method. Background Art

[0002] The principle of a Michelson interferometer is that an incident beam of light is split into two by a beam splitter. Each beam is reflected by its corresponding mirror (a moving mirror and a stationary mirror), where it interferes with the other and produces interference fringes. The different optical path lengths of the two beams can be adjusted by adjusting the motion of the moving mirror, resulting in different interference patterns. Determining these interference patterns requires the motion distance parameter of the moving mirror, which requires high-precision measurement of this motion distance parameter.

[0003] In the prior art, a single laser is used to measure the motion distance parameter. However, as a precision instrument, the laser has high requirements for the environmental conditions of use, such as temperature and platform stability. Generally, it can only be used as a laboratory instrument, which is not conducive to productization and measurement in environments outside the laboratory. In addition, this single detection method has obvious defects. For example, when the laser is prone to temperature drift after working for a long time, due to the lack of another detection method to calibrate it, it is difficult to detect the measurement error caused by temperature drift, which affects the measurement results. At the same time, when the laser fails or freezes due to external interference, the motion distance measurement of the moving mirror will completely disappear, resulting in the loss of control of the moving mirror and easy damage to the instrument. Therefore, there is an urgent need for a dual-feedback spectral detection method that uses a laser to measure distance while using another form of supplementary measurement to promptly detect and replace the erroneous measurement data of the laser and avoid the complete disappearance of the motion distance measurement of the moving mirror, which may cause damage to the instrument. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a dual-feedback spectrum detection method.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A dual-feedback spectrum detection method, applied to a Fourier transform spectrometer, comprises the following steps:

[0007] Step S1, using a grating ruler to measure the moving mirror and obtain its displacement A1, and at the same time using a laser to measure the moving mirror and obtain its displacement A2;

[0008] Step S2, determining whether the difference between the displacement A1 and the displacement A2 is less than an error threshold;

[0009] Step S3: if the difference is less than the error threshold, output the displacement A2;

[0010] Step S4: If the difference is greater than or equal to the error threshold, the displacement A1 is output and it is determined that the laser measurement is abnormal.

[0011] As a further improvement of the above technical solution:

[0012] The following steps are also included:

[0013] Step S5 , obtaining the interference fringe signal of the target light beam, and combining it with the displacement A2 output in step S3 or the displacement A1 output in step S4 to calculate and obtain the wavelength and / or amplitude information of the target light beam.

[0014] A laser emits a laser beam, which is transmitted through a beam splitter prism A to form a split beam A. The split beam A is reflected by a moving mirror and then re-enters the beam splitter prism A and is reflected by it. The laser beam is reflected by the beam splitter prism A to form a split beam B. The split beam B is reflected by a static mirror and then re-enters the beam splitter prism A and is refracted by it. The split beam A reflected by the beam splitter prism A and the beam B refracted by the beam splitter prism A merge to form an interference light A. The interference light A is reflected by the beam splitter prism B and enters the detector A, and is transmitted through the beam splitter prism B and enters the detector B. The detectors A and B are respectively connected to a processing module signal, and the processing module calculates the displacement A2 based on the interference fringe signals collected by the detectors A and B.

[0015] The target light beam is transmitted through the beam splitter prism A to form a split light beam C, which is reflected by the moving mirror and enters the beam splitter prism A again and is reflected by it; the target light beam is reflected by the beam splitter prism A to form a split light beam D, which is reflected by the static mirror and enters the beam splitter prism A again and is refracted by it; the split light beam C reflected by the beam splitter prism A and the light beam D refracted by the beam splitter prism A merge to form an interference light beam B, which is incident on the detector C; the detector C is connected to the signal of the processing module, and the processing module calculates the wavelength and / or amplitude information of the target light beam based on the interference fringe signal obtained by the detector C and the displacement A2 output in step S3 or the displacement A1 output in step S4.

[0016] The laser beam is directed toward the edge of the dichroic prism A, and the target beam is directed toward the center of the dichroic prism A.

[0017] The grating ruler is installed on the driver, the movable part of the driver is connected to the moving mirror, and the movable part is fixed to the reading head of the grating ruler.

[0018] The moving direction of the movable part is parallel to the laser beam emitted by the laser.

[0019] The laser is configured as a helium-neon laser.

[0020] Compared with the prior art, the advantages of the present invention are:

[0021] In the technical solution of the present application, the displacement of the moving mirror is measured by both a grating ruler and a laser, and the measurement results of the two are compared. Since the grating ruler has high stability and its results can be considered to be always correct, when the difference between the displacement A and the displacement A is less than the error threshold, it can be inferred that the laser measurement is in a stable state. Since its measurement accuracy is higher, the displacement A is selected as the output result; when the difference between the displacement A and the displacement A is greater than or equal to the error threshold, it can be determined that the laser measurement is in an invalid state. At this time, the displacement A with relatively low accuracy but correct is selected as the output result. In this way, compared with the method of measuring in the prior art using only a single mode, the technical solution provided by the present application sets a grating ruler for supplementary measurement and compares its measured results with the results measured by the laser in real time. It can timely discover the erroneous measurement data of the laser and replace it, thereby ensuring that the output result of the moving mirror displacement is always correct, thereby improving the reliability of the measurement result and avoiding the damage to the measuring instrument caused by the output of erroneous data parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of the dual-feedback spectral detection method;

[0023] Figure 2 It is a schematic diagram of the structure of Fourier transform spectrometer;

[0024] Figure 3 It is a comparative diagram of the sampling points set in the prior art and the present application.

[0025] in:

[0026] 1. Moving mirror; 2. Beam splitter prism A; 3. Static mirror; 4. Beam splitter prism B; 5. Detector A; 6. Detector B; 7. Processing module; 8. Detector C; 9. Driver;

[0027] a1, target beam; a2, laser beam; a3, sub-beam A; a4, sub-beam B; a5, interference light A; a6, sub-beam C; a7, sub-beam D; a8, interference light B. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figures 1 to 3 As shown, the dual-feedback spectrum detection method of this embodiment is applied to a Fourier transform spectrometer and includes the following steps:

[0030] Step S1, using a grating ruler to measure the moving mirror 1 and obtain its displacement A1, and at the same time using a laser to measure the moving mirror 1 and obtain its displacement A2;

[0031] Step S2, determining whether the difference between the displacement A1 and the displacement A2 is less than an error threshold;

[0032] Step S3: if the difference is less than the error threshold, output the displacement A2;

[0033] Step S4: If the difference is greater than or equal to the error threshold, the displacement A1 is output and it is determined that the laser measurement is abnormal.

[0034] Specifically, when using a grating ruler for measurement, the displacement A1 can be read directly through the grating ruler; when using a laser for measurement, the laser emits a laser beam a2, which is transmitted through the dichroic prism A2 to form a split beam Aa3, which is reflected by the moving mirror 1 and enters the dichroic prism A2 again and is reflected by it; the laser beam a2 is reflected by the dichroic prism A2 to form a split beam Ba4, which is reflected by the static mirror 3 and enters the dichroic prism A2 again and is refracted by it; the split beam Aa3 reflected by the dichroic prism A2 and the beam Ba4 refracted by the dichroic prism A2 merge to form an interference light Aa5, which is reflected by the dichroic prism B4 and enters the detector A5, and is transmitted through the dichroic prism B4 and enters the detector B6; the detector A5 and the detector B6 are respectively connected to the signal of the processing module 7, and the processing module 7 calculates the displacement A2 based on the interference fringe signals collected by the detectors A5 and B6.

[0035] Measuring the moving mirror 1 with a grating ruler has the characteristics of high stability and relatively low measurement accuracy, while measuring the moving mirror 1 with a laser has the characteristics of high measurement accuracy and relatively low stability. In the technical solution of the present application, the displacement of the moving mirror 1 is measured by a grating ruler and a laser at the same time, and the measurement results of the two are compared. Since the grating ruler has high stability and its results can be considered to be always correct, when the difference between the displacement A1 and the displacement A2 is less than the error threshold, it can be inferred that the laser measurement is in a stable state, and because its measurement accuracy is higher, the displacement A2 is selected as the output result; when the difference between the displacement A1 and the displacement A2 is greater than or equal to the error threshold, it can be judged that the laser measurement is in a failed state, and at this time, the relatively low-accuracy but correct displacement A1 is selected as the output result. In this way, compared with the method of using only a single mode for measurement in the prior art, the technical solution provided by the present application sets a grating ruler for supplementary measurement, and compares its measured results with the results measured by the laser in real time. It can promptly discover the erroneous measurement data of the laser and replace it, thereby ensuring that the output result of the displacement of the moving mirror 1 is always correct, thereby improving the reliability of the measurement result, and avoiding the damage to the measuring instrument caused by the corresponding erroneous movement of the moving mirror 1 due to the output of erroneous data parameters.

[0036] In this embodiment, the following steps are also included:

[0037] Step S5 , obtaining the interference fringe signal of the target light beam a1 , and combining the displacement A2 output in step S3 or the displacement A1 output in step S4 to calculate and obtain the wavelength and / or amplitude information of the target light beam a1 .

[0038] Specifically, the target light beam a1 is transmitted through the dichroic prism A2 to form a split light beam Ca6, which is reflected by the moving mirror 1 and enters the dichroic prism A2 again and is reflected by it; the target light beam a1 is reflected by the dichroic prism A2 to form a split light beam Da7, which is reflected by the static mirror 3 and enters the dichroic prism A2 again and is refracted by it; the split light beam Ca6 reflected by the dichroic prism A2 and the light beam Da7 refracted by the dichroic prism A2 merge to form an interference light Ba8, which is incident on the detector C8; the detector C8 is signal-connected to the processing module 7, and the processing module 7 calculates the wavelength and / or amplitude information of the target light beam a1 based on the interference fringe signal obtained by the detector C8 and the displacement A2 output in step S3 or the displacement A1 output in step S4.

[0039] Furthermore, the existing technology uses a zero-crossing sampling method, whereby a sample is taken each time the light wave reaches zero. Therefore, the sampling frequency is directly affected by the wavelength, which makes it difficult for the measurable spectral range to reach the visible light region, significantly limiting the application range of Fourier transform spectrometers. The technical solution disclosed in this application, by setting the sampling frequency, enables high-speed continuous position sampling, allowing for unlimited shortening of the sampling interval. This increases the upper limit of the Fourier transform spectrometer's measurement wavelength, allowing it to cover the visible light region and thus expand its application range.

[0040] In this embodiment, the laser beam a2 is directed toward the edge of the beam splitter prism A2, and the target beam a1 is directed toward the center of the beam splitter prism A2. Since the energy of the laser beam a2 is stronger than that of the target beam a1, when the laser beam a2 is too close to the target beam a1, it is easy to interfere with the target beam a1, thereby affecting the measurement results. Specifically, the laser beam a2 has a small aperture, and the incident reflection area is the edge of the beam splitter prism A2, while the target beam a1 has a large aperture, and the incident reflection area is the center of the beam splitter prism A2. Although the two beams share optical components, they can be separated by separating the irradiation areas to avoid interference. In other words, through such a setting, the present application can provide reliable measurement data without adding optical components.

[0041] In this embodiment, the grating ruler is mounted on the driver 9. The movable portion of the driver 9 is connected to the moving mirror 1 and fixed to the grating ruler's reading head. The movable portion of the driver 9 is the component that connects to and drives the moving mirror 1 to reciprocate. The displacement of the movable portion determines the movement of the moving mirror 1. Therefore, by measuring the movable portion with the grating ruler, the displacement data of the moving mirror 1 can be derived, thereby providing support for subsequent calculations. Specifically, the grating ruler's reading head is fixedly connected to the movable portion of the driver 9. When the movable portion moves, the reading head measures it while following the movement, thereby obtaining displacement information of the movable portion.

[0042] In this embodiment, the movable portion moves in a direction parallel to the laser beam a2 emitted by the laser. Because the movement of the movable mirror 1 is required to produce movement toward or away from the beam splitter prism A2, when the movable portion moves in a direction parallel to the laser beam a2, the movable mirror 1 is driven to move synchronously in a direction parallel to the laser beam a2, thereby producing movement toward or away from the beam splitter prism A2.

[0043] In this embodiment, the laser is configured as a He-Ne laser. More specifically, the He-Ne laser is a temperature-compensated frequency-stabilized laser, which can compensate for temperature drift caused by operating at different ambient temperatures and long-term operation of the laser, thereby ensuring measurement accuracy as much as possible.

[0044] Although the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Any person skilled in the art can, without departing from the scope of the technical solution of the present invention, utilize the technical content disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A dual-feedback spectrum detection method, characterized in that: Applied to Fourier transform spectrometer, including the following steps: Step S1, using a grating ruler to measure the moving mirror (1) and obtain its displacement A1, and at the same time using a laser to measure the moving mirror (1) and obtain its displacement A2; Step S2, determining whether the difference between the displacement A1 and the displacement A2 is less than an error threshold; Step S3: if the difference is less than the error threshold, output the displacement A2; Step S4: if the difference is greater than or equal to the error threshold, output the displacement A1 and determine that the laser measurement is abnormal; Step S5, obtaining the interference fringe signal of the target light beam (a1), and combining the displacement A2 output in step S3 or the displacement A1 output in step S4 to calculate and obtain the wavelength and / or amplitude information of the target light beam (a1); The laser emits a laser beam (a2), which is transmitted through a beam splitter prism A (2) to form a beam splitter A (a3), which is reflected by a moving mirror (1) and then enters the beam splitter prism A (2) again and is reflected by it; the laser beam (a2) is reflected by the beam splitter prism A (2) to form a beam splitter B (a4), which is reflected by a static mirror (3) and then enters the beam splitter prism A (2) again and is refracted by it; the beam splitter A (a3) ​​reflected by the beam splitter prism A (2) The interference light A (a5) is merged with the light beam B (a4) refracted by the dichroic prism A (2) to form an interference light beam. The interference light beam A (a5) is reflected by the dichroic prism B (4) and enters the detector A (5), and is transmitted by the dichroic prism B (4) and enters the detector B (6). The detector A (5) and the detector B (6) are respectively connected to the signal of the processing module (7). The processing module (7) calculates the displacement A2 based on the interference fringe signals collected by the detectors A (5) and B (6).

2. The dual-feedback spectrum detection method according to claim 1, characterized in that: The target light beam (a1) is transmitted through the dichroic prism A (2) to form a split light beam C (a6), and the split light beam C (a6) is reflected by the moving mirror (1) and then enters the dichroic prism A (2) again and is reflected by it; the target light beam (a1) is reflected by the dichroic prism A (2) to form a split light beam D (a7), and the split light beam D (a7) is reflected by the static mirror (3) and then enters the dichroic prism A (2) again and is refracted by it; the split light beam C (a6) reflected by the dichroic prism A (2) and The light beam D (a7) refracted by the dichroic prism A (2) converges to form an interference light beam B (a8), and the interference light beam B (a8) is incident on the detector C (8); the detector C (8) is connected to the signal of the processing module (7), and the processing module (7) calculates the wavelength and / or amplitude information of the target light beam (a1) based on the interference fringe signal obtained by the detector C (8) and the displacement A2 output in step S3 or the displacement A1 output in step S4.

3. The dual-feedback spectrum detection method according to claim 2, wherein: The laser beam (a2) is directed toward the edge of the dichroic prism A (2), and the target beam (a1) is directed toward the center of the dichroic prism A (2).

4. The dual-feedback spectrum detection method according to any one of claims 1 to 3, characterized in that: The grating ruler is mounted on a driver (9), a movable portion of the driver (9) is connected to a moving mirror (1), and the movable portion is fixed to a reading head of the grating ruler.

5. The dual-feedback spectrum detection method according to claim 4, characterized in that: The moving direction of the movable part is parallel to the laser beam (a2) emitted by the laser.

6. The dual-feedback spectrum detection method according to any one of claims 1 to 3, characterized in that: The laser is configured as a helium-neon laser.

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