Wavelimeter based on band-pass filter and wavelength measurement calibration method
Through a wavelength meter based on bandpass filter, the combination of bandpass filter and camera is used to solve the problems of insufficient accuracy and complex structure of existing wavelength measurement methods, and achieve fast, accurate and low-cost wavelength measurement, and facilitate integrated use.
Patent Information
- Application Number
- CN202411737033.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-29
- Publication Date
- 2025-02-25
AI Technical Summary
The existing wavelength measurement methods have problems such as insufficient accuracy, complex structure, high cost and difficulty in integrating and using it.
Using a wavelength meter based on a bandpass filter, the spectral responses of different wavelengths are measured by a combination of a single-mode optical fiber, a bandpass filter and a camera, and the light field intensity distribution is recorded through the camera to calculate the wavelength of the incident light.
It realizes fast and accurate wavelength measurement, with a simple structure, low cost and small size, which is easy to integrate and carry, and ensures accuracy through calibration methods.
Smart Images
Figure CN119509717A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of laser wavelength measurement, and in particular to an optical wavelength measurement device based on a bandpass filter and a wavelength measurement calibration method. Background Art
[0002] Wavelength measurement technology plays a vital role in many disciplines such as physics, optics and engineering. In particular, it plays a core role in high-tech fields such as optical communications, laser technology, spectral analysis and material science.
[0003] Traditional wavelength measurement methods include spectroscopy and interferometry. Spectroscopy relies on prisms or diffraction gratings to disperse light into spectra of different wavelengths, and wavelength measurement is performed by analyzing the spectrum. However, it is difficult to achieve high accuracy due to the influence of dispersion element technology and detector resolution. Interferometry includes three measurement methods: Fizeau interferometry, Fabry Perot interferometry, and Michelson interferometry. They are sensitive to environmental factors and have complex structures and operations. Summary of the invention
[0004] The present invention aims to provide a wavelength meter based on a bandpass filter and a wavelength measurement calibration method, which can measure the wavelength quickly and accurately, has a simple structure, does not contain any moving structure, is easy to use and has low cost.
[0005] To this end, the technical solution adopted by the present invention is: a wavelength meter based on a bandpass filter, comprising a single-mode optical fiber, and a bandpass filter and a camera arranged in sequence along the propagation direction of the incident light; the single-mode optical fiber is used to receive the incident light of the wavelength to be measured; the bandpass filter is placed at a certain angle relative to the direction of the incident light, so that the incident light is incident at a certain angle when it reaches the bandpass filter, and the bandpass filter will produce different spectral responses to incident light of different wavelengths, thereby causing different changes in the light field intensity distribution after passing through the bandpass filter; the camera is used to capture and record the light field intensity distribution after passing through the bandpass filter.
[0006] As a preferred embodiment of the above scheme, the wavelength meter based on the bandpass filter further includes a first fiber coupler and a lens, and the two are sequentially arranged between the single-mode optical fiber and the bandpass filter along the propagation direction of the incident light; the distance between the lens and the first fiber coupler, the distance between the lens and the bandpass filter, the distance between the bandpass filter and the camera, and the angle at which the bandpass filter is placed are fixed to ensure that the light field intensity distribution will not change due to position changes.
[0007] More preferably, the camera is a CCD or CMOS camera.
[0008] Further preferably, the single-mode optical fiber adopts a polarization-maintaining optical fiber, which makes the polarization state of the incident light consistent, ensuring that the light field intensity distribution will not change due to the change of the polarization state.
[0009] Further preferably, the light beam enters the bandpass filter at a certain incident angle, and at different positions of the bandpass filter, the incident angle at each position can be calculated by the following formula:
[0010]
[0011] Where: θ0 is the deflection angle of the bandpass filter, in rad; d is the distance between the incident light focus and the center of the bandpass filter, in m; (x i ,y i ) is the coordinate of a point on the bandpass filter, the origin of the coordinate is the center of the bandpass filter, the unit is m; θ i is the incident angle corresponding to a point on the bandpass filter, in rad.
[0012] More preferably, the central peak wavelength of the bandpass filter is 800 nanometers, the bandwidth is 10 nanometers, and when the incident angle changes from 0 degrees to 30 degrees, the transmission central wavelength moves from 800 nanometers to 770 nanometers.
[0013] At the same time, the present invention also provides a wavelength measurement calibration method using the above-mentioned wavelength meter based on the bandpass filter, comprising the following steps:
[0014] Step 1: According to the wavelength range to be measured, the distance d between the incident light focus and the center position of the bandpass filter and the deflection angle θ0 of the bandpass filter are selected and determined;
[0015] Step 2, connect the instruments required for calibration to the bandpass filter-based wavelength meter;
[0016] Prepare the tunable laser, beam splitter, second fiber coupler, third fiber coupler and commercial wavelength meter required for calibration; first connect the tunable laser to the beam splitter, the tunable laser is used to realize laser output, the beam splitter is used to split the laser output of the tunable laser into two paths, the second fiber coupler and the third fiber coupler are respectively arranged on two optical paths, so that one path of light is transmitted through the second fiber coupler and enters the wavelength meter based on the bandpass filter, and the other path of light is reflected through the third fiber coupler and enters the commercial wavelength meter with high accuracy;
[0017] Step 3: setting a series of uniformly distributed wavelengths within the wavelength range to be measured for calibration;
[0018] The laser is output through a tunable laser, and the calibration light wavelength measured by a commercial wavelength meter and the light field intensity distribution photographed by a wavelength meter based on a bandpass filter are recorded at the same time. After analyzing the above series of calibration wavelengths and their corresponding light field intensity distributions, a calibration curve of the relationship between wavelength and light field intensity distribution is obtained;
[0019] Step 4: After the calibration is completed, the tunable laser, beam splitter, second fiber coupler, third fiber coupler and commercial wavelength meter required for the calibration are removed. At this time, the wavelength meter based on the bandpass filter can independently complete the measurement of the light wavelength within the selected wavelength range.
[0020] Preferably, the commercial wavelength meter is commercially available and has an accuracy of 0.0001 nanometers.
[0021] Furthermore, the tunable laser can achieve laser output with a wavelength ranging from 780 nanometers to 805 nanometers.
[0022] The present invention has the following beneficial effects: by biasing the bandpass filter, the incident light is incident at a certain angle when it reaches the bandpass filter. For incident light of different wavelengths, the bandpass filter will produce different spectral responses, so that the light field intensity distribution after passing through the bandpass filter will produce different changes. Then, a camera is used to shoot and record the light field intensity distribution after passing through the bandpass filter. The wavelength of the incident light is calculated through the relationship between the wavelength and the light field intensity distribution. (1) The price of existing commercial high-precision wavelength meters ranges from hundreds of thousands to millions, while the present wavelength meter has a simple structure and low cost; (2) It is simple and convenient to operate, with fast measurement speed and accurate measurement; (3) Existing commercial high-precision wavelength meters are large in size and difficult to integrate for use, while the present wavelength meter is small in size and easy to integrate and carry.
[0023] At the same time, for different bias angles of the bandpass filter, an existing commercial wavelength meter can be used for rapid calibration to further ensure the accuracy of the wavelength meter. After the calibration is completed, the commercial wavelength meter can be removed without additional cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a structural schematic diagram of a wavelength meter based on a bandpass filter proposed by the present invention.
[0025] Figure 2 It is a schematic diagram of a device used for calibrating a wavelength meter based on a bandpass filter proposed by the present invention.
[0026] Figure 3 It is a principle diagram for calculating the incident angles corresponding to different positions of the bandpass filter proposed by the present invention.
[0027] Figure 4 The bandpass filter proposed by the present invention is placed at an angle of 16 degrees, and the light field intensity distribution corresponding to incident light of different wavelengths photographed by a CCD camera.
[0028] Among them, 11. single-mode optical fiber, 12. optical fiber coupler, 13. lens, 14. bandpass filter, 15. camera, 20. tunable laser, 30. beam splitter, 40. optical fiber coupler, 50. commercial wavelength meter. DETAILED DESCRIPTION
[0029] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.
[0030] like Figure 1 , Figure 3 As shown, a wavelength meter based on a bandpass filter is mainly composed of a single-mode optical fiber 11, and a first optical fiber coupler 12, a lens 13, a bandpass filter 14 and a camera 15 arranged in sequence along the propagation direction of the incident light.
[0031] Among them, the single-mode optical fiber 11, and the bandpass filter 14 and camera 15 arranged in sequence along the propagation direction of the incident light are essential components of the wavelength meter based on the bandpass filter. The single-mode optical fiber 11 is used to receive the incident light of the wavelength to be measured. The bandpass filter 14 is the core component of the wavelength meter. It is placed at a certain angle relative to the direction of the incident light so that the incident light is incident at a certain angle when it reaches the bandpass filter 14. For incident light of different wavelengths, the bandpass filter 14 will produce different spectral responses, so that the light field intensity distribution after passing through the bandpass filter 14 will produce different changes. The camera 15 is used to shoot and record the light field intensity distribution after passing through the bandpass filter 14. It is best to use polarization-maintaining optical fiber for the single-mode optical fiber 11 to make the polarization state of the incident light consistent, to ensure that the light field intensity distribution will not change due to the change in the polarization state, and to further improve the measurement accuracy of the wavelength meter. The camera 15 is best to use a CCD or CMOS camera.
[0032] The performance can be further improved by installing the first optical fiber coupler 12 and the lens 13. The lens 13 is used to expand the incident light so that the light spot size is more compatible with the size of the bandpass filter 14.
[0033] The distance between the lens 13 and the first optical fiber coupler 12, the distance between the lens 13 and the bandpass filter 14, the distance between the bandpass filter 14 and the camera 15, and the angle at which the bandpass filter 14 is placed are fixed to ensure that the light field intensity distribution does not change due to position changes.
[0034] The light of the wavelength to be measured is incident from the single-mode optical fiber 11 and the optical fiber coupler 12. After being amplified by the lens 13, the light beam will have a divergence angle, and the bandpass filter 14 is set at a certain angle, so the light beam will enter the bandpass filter 14 at a certain incident angle. At different positions of the bandpass filter 14, the incident angle of each position can be calculated by the following formula:
[0035]
[0036] Where: θ0 is the deflection angle of the bandpass filter, in rad; d is the distance between the incident light focus and the center of the bandpass filter, in m; (x i ,y i ) is the coordinate of a point on the bandpass filter, the origin of the coordinate is the center of the bandpass filter, the unit is m; θ i is the incident angle corresponding to a point on the bandpass filter, in rad.
[0037] The central transmission wavelength of the bandpass filter 14 changes with the incident angle. As the incident angle increases, the central transmission wavelength of the bandpass filter 14 moves toward the short-wave direction.
[0038] Since the incident angles at different positions of the bandpass filter 14 are different, the transmission center wavelengths at different positions are different. When light of different wavelengths is incident, the transmittance at the same position of the bandpass filter 14 is different, and the light field intensity after passing through the bandpass filter 14 will change differently.
[0039] For different incident angles, the bandpass filter has its corresponding transmittance curve. Combined with the above calculation of the incident angle at each position, the transmittance curve at each position of the bandpass filter can be obtained. When the bandpass filter is placed at a certain angle θ0, the wavelength range that can be measured is: at this incident angle, the transmittance corresponding to this wavelength range changes monotonically, and the change is obvious. Use camera 15 to shoot the light field intensity distribution of light beams of different wavelengths after passing through the bandpass filter 14. By analyzing the light field intensity distribution of incident light of different wavelengths after passing through the bandpass filter 14, the corresponding relationship between wavelength and light field intensity distribution can be obtained.
[0040] A wavelength measurement calibration method using the above-mentioned wavelength meter based on the bandpass filter comprises the following steps:
[0041] Step 1: According to the wavelength range to be measured, select and determine the distance d between the focus of the incident light and the center position of the bandpass filter 14, and the deflection angle θ0 of the bandpass filter 14.
[0042] It is best to select the wavelength range to be measured and then select a bandpass filter whose transmittance changes significantly within the selected wavelength range at different incident angles; set the deflection angle of the bandpass filter so that at the deflection angle, the transmittance in the selected wavelength range changes monotonically, and make the transmittance per unit wavelength change as large as possible to achieve higher accuracy.
[0043] Step 2: Connect the instruments required for calibration to the bandpass filter-based wavelength meter.
[0044] like Figure 2As shown, the tunable laser 20, beam splitter 30, second fiber coupler 40.1, third fiber coupler 40.2 and commercial wavelength meter 50 required for calibration are prepared; first, the tunable laser 20 is connected to the beam splitter 30, the tunable laser 20 is used to realize laser output, the beam splitter 30 is used to split the laser output of the tunable laser 20 into two paths, the second fiber coupler 40.1 and the third fiber coupler 40.2 are respectively arranged on two optical paths, so that one path of light is transmitted through the second fiber coupler 40.1 and enters the wavelength meter 10 based on the bandpass filter, and the other path of light is reflected through the third fiber coupler 40.2 and enters the commercial wavelength meter 50 with a high accuracy.
[0045] Step 3: Set a series of uniformly distributed wavelengths within the wavelength range to be measured for calibration.
[0046] The laser is output through the tunable laser 20, and the calibration light wavelength measured by the commercial wavelength meter 50 and the light field intensity distribution photographed by the wavelength meter 10 based on the bandpass filter are recorded at the same time. After analyzing the above series of calibration wavelengths and their corresponding light field intensity distributions, a calibration curve of the relationship between wavelength and light field intensity distribution is obtained.
[0047] The tunable laser 20 can achieve laser output with a wavelength ranging from 780 nanometers to 805 nanometers. The commercial wavelength meter 50 is a commercially available product with any model, and can achieve accurate wavelength measurement with an accuracy of preferably 0.0001 nanometer.
[0048] Step 4: After the calibration is completed, the tunable laser 20, beam splitter 30, second fiber coupler 40.1, third fiber coupler 40.2 and commercial wavelength meter 50 required for the calibration are removed. At this time, the wavelength meter 10 based on the bandpass filter can independently complete the measurement of the light wavelength within the selected wavelength range.
[0049] Combination Figure 1 As shown in FIG. 4 , in this example, the central peak wavelength of the selected bandpass filter 14 is 800 nanometers and the bandwidth is 10 nanometers. When the incident angle changes from 0 degrees to 30 degrees, its transmission center wavelength moves from 800 nanometers to 770 nanometers.
[0050] The bandpass filter 14 is placed at an angle θ0 = 16°. The incident angle θ at each position on the bandpass filter 14 is calculated according to the above formula. i Combined with the transmission curve of the bandpass filter 14 at this incident angle, the transmittance of light beams of different wavelengths at each position on the filter 14 can be calculated. The bandpass filter 14 can be placed with a deflection of 16 degrees to achieve wavelength measurement in the range of 787 nanometers to 789 nanometers. Figure 4The light field intensity distribution corresponding to different wavelengths when the bandpass filter 14 is placed at an angle of 16 degrees is shown: A is 787.5050 nanometers, B is 787.9900 nanometers, and C is 788.4600 nanometers. The changes in the light field intensity distribution corresponding to different wavelengths can be clearly observed.
[0051] Before measuring, you can use an existing commercial wavelength meter to calibrate the relationship between wavelength and light field intensity distribution. Figure 2 As shown: the wavelength adjustment range of the tunable laser 20 is 780 nanometers to 805 nanometers. The beam splitter 30 divides the laser into two paths, one of which is transmitted through the second fiber coupler 40.1 and enters the wavelength meter 10 based on the bandpass filter proposed by the present invention; the other is reflected through the third fiber coupler 40.2 and enters the commercial wavelength meter 50 with an accuracy of 0.0001 nanometers.
[0052] In this embodiment, a series of wavelengths for calibration are set from 787 nanometers to 789 nanometers, and the commercial wavelength meter 50 is used to measure the accurate wavelength, accurate to 0.0001 nanometer; at the same time, the wavelength meter 10 based on the bandpass filter proposed in the present invention is used to record the light field intensity distribution corresponding to the wavelength, and the relationship curve between the wavelength and the light field intensity distribution is obtained by analyzing the light field intensity distribution corresponding to different wavelengths. After that, the wavelength of the unknown wavelength to be measured in the range of 787 nanometers to 789 nanometers can be measured by the wavelength meter based on the bandpass filter proposed in the present invention, and the root mean square error of the measurement result is less than 0.002 nanometers.
[0053] In addition, the calibration method can also be calibrated by using a known laser wavelength. In this case, there is no need to use a commercial wavelength meter. For example, the wavelength of a He-Ne laser can be used for calibration.
[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A wavelength meter based on a bandpass filter, characterized in that: The invention comprises a single-mode optical fiber (11), and a band-pass filter (14) and a camera (15) which are sequentially arranged along the propagation direction of the incident light; the single-mode optical fiber (11) is used to receive the incident light of the wavelength to be measured; the band-pass filter (14) is placed at a certain angle relative to the direction of the incident light, so that the incident light is incident at a certain angle when it reaches the band-pass filter (14); for incident light of different wavelengths, the band-pass filter (14) will produce different spectral responses, thereby causing different changes in the light field intensity distribution after passing through the band-pass filter (14); and the camera (15) is used to photograph and record the light field intensity distribution after passing through the band-pass filter (14).
2. A wavelength meter based on a bandpass filter according to claim 1, characterized in that: The invention also comprises a first optical fiber coupler (12) and a lens (13), and the two are sequentially arranged between the single-mode optical fiber (11) and the band-pass filter (14) along the propagation direction of the incident light; the distance between the lens (13) and the first optical fiber coupler (12), the distance between the lens (13) and the band-pass filter (14), the distance between the band-pass filter (14) and the camera (15), and the angle at which the band-pass filter (14) is placed are fixed to ensure that the light field intensity distribution does not change due to position changes.
3. A wavelength meter based on a bandpass filter according to claim 1 or 2, characterized in that: The camera (15) is a CCD or CMOS camera.
4. A wavelength meter based on a bandpass filter according to claim 1 or 2, characterized in that: The single-mode optical fiber (11) adopts a polarization-maintaining optical fiber, which makes the polarization state of the incident light consistent, ensuring that the light field intensity distribution will not change due to the change of the polarization state.
5. A wavelength meter based on a bandpass filter according to claim 1, characterized in that: The light beam enters the bandpass filter (14) at a certain incident angle. At different positions of the bandpass filter (14), the incident angle at each position can be calculated by the following formula: Where: θ0 is the deflection angle of the bandpass filter, in rad; d is the distance between the incident light focus and the center of the bandpass filter, in m; (x i ,y i ) is the coordinate of a point on the bandpass filter, the origin of the coordinate is the center of the bandpass filter, the unit is m; θ i is the incident angle corresponding to a point on the bandpass filter, in rad.
6. A wavelength meter based on a bandpass filter according to claim 1, characterized in that: The central peak wavelength of the bandpass filter (14) is 800 nanometers and the bandwidth is 10 nanometers. When the incident angle changes from 0 degrees to 30 degrees, the transmission central wavelength moves from 800 nanometers to 770 nanometers.
7. A wavelength measurement calibration method using a wavelength meter based on a bandpass filter according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: According to the wavelength range to be measured, the distance d between the focal point of the incident light and the center position of the band-pass filter (14) and the deflection angle θ0 of the band-pass filter (14) are selected and determined; Step 2, connect the instruments required for calibration to the bandpass filter-based wavelength meter; Prepare a tunable laser (20), a beam splitter (30), a second optical fiber coupler (40.1), a third optical fiber coupler (40.2) and a commercial wavelength meter (50) required for calibration; first, connect the tunable laser (20) to the beam splitter (30); the tunable laser (20) is used to realize laser output; the beam splitter (30) is used to split the laser output of the tunable laser (20) into two paths; the second optical fiber coupler (40.1) and the third optical fiber coupler (40.2) are respectively arranged on two optical paths, so that one path of light is transmitted through the second optical fiber coupler (40.1) and enters the wavelength meter (10) based on the bandpass filter, and the other path of light is reflected through the third optical fiber coupler (40.2) and enters the commercial wavelength meter (50) with a high accuracy; Step 3: setting a series of uniformly distributed wavelengths within the wavelength range to be measured for calibration; The tunable laser (20) outputs laser light, and simultaneously records the calibration light wavelength measured by a commercial wavelength meter (50) and the light field intensity distribution photographed by a wavelength meter (10) based on a bandpass filter, and after analyzing the above series of calibration wavelengths and the corresponding light field intensity distributions, obtains a calibration curve of the relationship between wavelength and light field intensity distribution; Step 4: After the calibration is completed, the tunable laser (20), beam splitter (30), second fiber coupler (40.1), third fiber coupler (40.2) and commercial wavelength meter (50) required for the calibration are removed. At this time, the wavelength meter (10) based on the bandpass filter can independently complete the measurement of the wavelength of light within the selected wavelength range.
8. The wavelength measurement calibration method based on a bandpass filter wavemeter according to claim 7, characterized in that: The commercial wavelength meter (50) is commercially available and has an accuracy of 0.0001 nanometers.
9. The wavelength measurement calibration method based on a bandpass filter wavemeter according to claim 7, characterized in that: The tunable laser (20) can achieve laser output with a wavelength ranging from 780 nanometers to 805 nanometers.