A high-precision wide-spectrum wavelength measurement device and method

Abstract

The invention discloses a high-precision wide-spectrum wavelength measurement device and method, belonging to the technical field of wavelength measurement. The wavelength measurement device includes a linear filter, a Fizeau interferometer, a photodetector, a spectrometer and a linear detector. The spectrometer is used to split the laser beam to be measured to obtain multiple beams; the linear filter is used to roughly measure the laser wavelength, and the approximate range value of the laser wavelength is obtained by the photodetector; the Fizeau interferometer measures a more accurate laser wavelength value based on the value measured by the linear filter, and the specific value is obtained by the linear detector. The wavelength measurement method uses a measurement method combining a linear filter and a Fizeau interferometer, takes the wavelength value measured by the linear filter as the measurement basis of the Fizeau interferometer, calculates the wavelength value of a higher order, takes the average value of the wavelength at two orders, reduces the error, and not only improves the measurement speed, but also increases the measurement spectrum range and improves the measurement accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of wavelength measurement, and in particular relates to a high-precision wide-spectrum wavelength measurement device and method. Background Art

[0002] Infrared laser spectrometers are widely used, covering scientific research, industrial production, medicine and biology, food safety and other aspects. For wavelength measurement, infrared laser spectrometers need to meet the requirements of high precision, wide range, good wavelength repeatability and accuracy to ensure the accuracy and reliability of the measurement results.

[0003] Among the methods of laser wavelength measurement based on the interference principle, the main methods are Fizeau interference type, Fabry-Perot interference type and Michelson interference type.

[0004] The Michelson interferometer measurement method requires the introduction of a reference laser and has a built-in mechanical scanning component, which is greatly affected by vibration. The Fabry-Perot interferometer measurement method has poor measurement accuracy because the cavity structure is very sensitive to temperature and optical power changes.

[0005] The currently existing Fizeau interferometry measurement method uses a single optical path to obtain interference fringes, which has high measurement accuracy and sensitivity, but cannot take into account both measurement accuracy and speed. Summary of the invention

[0006] In view of the shortcomings of the existing interference type wavelength measurement method, which is limited by the relationship between measurement accuracy and measurement range, the purpose of the present invention is to propose a measurement device and method that combines a linear filter and a Fizeau interferometer cavity to solve the measurement problem that the Fizeau interferometer type cannot take into account both measurement accuracy and spectral range.

[0007] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0008] According to a first aspect of the present invention, a high-precision wide-spectrum wavelength measurement device is proposed, comprising: a spectrometer, a linear filter, a photodetector, a Fizeau interferometer cavity and a linear array detector, the spectrometer is used to split the laser beam to be measured to generate a first light beam and a second light beam, the linear filter and the photodetector are sequentially arranged on the transmission light path of the spectrometer along the light transmission direction, the linear filter is used to receive the first light beam and modulate the light signal into a signal whose light intensity varies linearly with the wavelength, and then the photodetector detects the signal; the Fizeau interferometer cavity and the linear array detector are sequentially arranged on the reflection light path of the spectrometer along the light transmission direction, the second light beam interferes after entering the Fizeau interferometer cavity to generate interference fringes; the linear array detector is used to measure the interference fringes and obtain the period value and phase value of the interference fringes.

[0009] Furthermore, the light splitting device uses a light splitter with a transmission and reflection ratio of 50:50.

[0010] Furthermore, the Fizeau interference cavity is composed of a protective glass, a cylindrical glass body, a wedge-shaped cylindrical glass body and a protective shell. The side walls of the protective glass, the side walls of the cylindrical glass body and the side walls of the wedge-shaped cylindrical glass body are fixed to the side walls of the protective shell in sequence. When viewed along the optical axis, the front surface of the cylindrical glass body is aligned with the front surface of the protective glass, and the plane of the wedge-shaped cylindrical glass body is aligned with the rear surface of the protective glass; the rear surface of the cylindrical glass body and the rear surface of the wedge-shaped cylindrical glass body are coated with a spectroscopic film.

[0011] Furthermore, the protective glass side wall, the cylindrical glass body side wall, the wedge-shaped cylindrical glass body side wall and the protective shell side wall are fixed in sequence by bonding using a laser welding process.

[0012] Furthermore, the ratio of transmittance to reflectivity of the beam splitting film is 3:7.

[0013] According to a second aspect of the present invention, a method for measuring laser wavelength using the high-precision wide-spectrum wavelength measurement device is provided, the method comprising:

[0014] The laser wavelength value is measured according to the linear filter and the photodetector ,set up In Level and Between the interference fringes;

[0015] Pre-calibrated wedge angle according to the Fizeau interferometer The phase of the interference fringes generated by the Fizeau interferometer is obtained by the linear detector. , and obtain the wavelength Corresponding height ;

[0016] Calculate the height according to the following formula :

[0017] ;

[0018] Among them, int() is the rounding function;

[0019] The level is calculated according to the following formula :

[0020] ;

[0021] Calculate according to the following formula Level height :

[0022] ;

[0023] Calculate according to the following formula Level height :

[0024] ;

[0025] Calculate according to the following formula Wavelength value at level :

[0026] ;

[0027] Calculate according to the following formula Wavelength value at level :

[0028] ;

[0029] Get the final wavelength value:

[0030] .

[0031] The Fizeau interferometer cavity needs to be calibrated before use. During the calibration, a laser with a known wavelength is used according to Wedge angle of Fizeau interferometer To perform calibration, Indicates the known wavelength of the calibration laser, in μm; Indicates the interference fringe spacing in mm.

[0032] Through the above-mentioned design scheme, the present invention can bring the following beneficial effects: the present invention proposes a high-precision wide-spectrum wavelength measurement device and method, which uses a measurement method combining a linear filter and a Fizeau interferometer cavity to solve the measurement problem that the Fizeau interferometer type cannot take into account both measurement accuracy and spectral range, and has the advantages of high accuracy, wide wavelength range coverage and fast response. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present application. The exemplary embodiments of the present invention and their descriptions are used to understand the present invention and do not constitute improper limitations of the present invention. In the drawings:

[0034] Figure 1 It is a schematic structural diagram of a high-precision wide-spectrum wavelength measurement device provided in an embodiment of the present application;

[0035] Figure 2 This is the front view of the Fizeau interferometer cavity;

[0036] Figure 3 This is the right view of the Fizeau interferometer cavity;

[0037] Figure 4 It is a schematic diagram of the example principle;

[0038] In the figure: 10 is the outer shell; 11 is the optical fiber; 12 is the light collimator; 13 is the spectrometer; 14 is the linear filter; 15 is the photodetector; 16 is the Fizeau interferometer cavity; 17 is the linear detector; 16-1 is the protective glass; 16-2 is the cylindrical glass body; 16-3 is the wedge-shaped cylindrical glass body; 16-4 is the protective shell. DETAILED DESCRIPTION

[0039] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the usual meanings understood by people with ordinary skills in the field to which the present invention belongs. It should be understood that the terms "first" and "second" are only used for descriptive purposes, and the characteristics of being limited to "first" and "second" do not represent any order, quantity or importance, but are only used to distinguish different components.

[0040] like Figure 1 , Figure 2 and Figure 3 As shown, the present invention provides a high-precision wide-spectrum wavelength measuring device, the wavelength measuring device is provided with a shell 10, the shell 10 is provided with a light inlet, the optical fiber 11, the light collimator 12 and the spectrometer 13 are placed in the shell 10 and placed on the incident light path of the light inlet, the spectrometer 13 adopts a spectroscope with a transmission and reflection ratio of 50:50, the laser is injected from the light inlet, is received by the spectrometer 13, and the laser to be measured is divided into two light beams, namely the first light beam and the second light beam, the linear filter 14 and the photodetector 15 are located on the light path where the first light beam is located, namely the transmission light path of the spectrometer 13, the Fizeau interferometer 16 and the linear detector 17 are located on the light path where the second light beam is located, namely the reflection light path of the spectrometer 13.

[0041] In this embodiment, the laser enters the fiber collimator 12 from the optical fiber 11, and the fiber collimator 12 converts the transmission light in the optical fiber 11 into parallel light. The parallel light is emitted into the splitting device 13, which is used to split the parallel light beam into a transmitted light beam and a reflected light beam, that is, a first light beam and a second light beam with a splitting ratio of 50:50.

[0042] The linear filter 14 modulates the optical signal into a signal whose light intensity varies linearly with the wavelength, and then the photodetector 15 detects the signal; the linear detector 17 is used to measure the phase and period of the interference fringes formed after the light beam passes through the Fizeau interferometer cavity 16.

[0043] According to the interference formula ,in is the wavelength of the laser to be measured, is the refractive index of the Fizeau interferometer cavity 16, is the thickness of the Fizeau interferometer cavity 16, is the interference order, and it can be obtained that, when other parameters remain unchanged, the thickness of the Fizeau interference cavity 16 The larger the value, the larger the maximum order of the interference fringes, and the higher the final wavelength accuracy. However, accurate positioning measurement cannot be performed over a wider wavelength range.

[0044] The linear filter 14 converts wavelength detection into light intensity detection, which not only has a fast measurement speed but also a wide spectrum range, thus making up for the above-mentioned shortcomings. As the measurement basis of the Fizeau interferometer cavity 16, the wavelength value of a higher order is calculated, and the average value of the wavelength at two orders is taken, which reduces the error and not only improves the measurement speed, but also increases the measurement spectral range and improves the measurement accuracy.

[0045] The Fizeau interference cavity 16 is composed of a protective glass 16-1, a cylindrical glass body 16-2, a wedge-shaped cylindrical glass body 16-3 and a protective shell 16-4. The side walls of the protective glass 16-1, the cylindrical glass body 16-2 and the wedge-shaped cylindrical glass body 16-3 are bonded to the side walls of the protective shell 16-4 in sequence. When viewed along the optical axis, the front surface of the cylindrical glass body 16-2 is aligned with the front surface of the protective glass 16-1, and the plane of the wedge-shaped cylindrical glass body 16-3 is aligned with the rear surface of the protective glass 16-1; the rear surfaces of the cylindrical glass body 16-2 and the wedge-shaped cylindrical glass body 16-3 are coated with a spectroscopic film with a transmittance-reflectivity ratio of 3:7 to form suitable interference fringes.

[0046] In particular, the bonding of the above components can be completed using a laser welding process, which has the characteristics of high precision and high joint strength and can reduce errors.

[0047] In particular, the protective shell 16-4 is made of 4J36 material, which is an iron-nickel alloy with an ultra-low expansion coefficient. Its main components include 64% iron and 36% nickel. Its expansion coefficient is very small in the range of 20°C to 100°C, or even close to zero. The protective shell 16-4 made of this alloy will hardly deform when the external temperature changes. Welding the optical element and the protective shell 16-4 can reduce the influence of temperature on the protective glass 16-1, the cylindrical glass body 16-2 and the wedge-shaped cylindrical glass body 16-3, thereby reducing the error caused by temperature.

[0048] The second light beam forms interference fringes on the linear detector 17 after passing through the Fizeau interferometer cavity 16, and then is incident on the linear detector 17. The linear detector 17 can convert the interference fringes into electrical signals for measuring the phase of the interference fringes.

[0049] In particular, in order to improve the measurement accuracy, the linear filter 14 needs to be calibrated before use. A laser with a known wavelength is used for measurement to observe whether the known wavelength value and the light intensity value measured by the photodetector 15 are in a linear relationship of the linear filter 14. If not, calibration is performed.

[0050] In particular, the Fizeau interferometer cavity 16 needs to be calibrated before use. During the calibration, a laser with a known wavelength is used to calibrate the wedge angle of the Fizeau interferometer cavity 16. Calibration is performed using Calibrate, where: is the wedge angle of the Fizeau interferometer cavity 16, in mrad; It represents the known wavelength of the calibration laser in μm. It represents the interference fringe spacing in mm.

[0051] The Fizeau interferometer cavity 16 is made of low-expansion glass-ceramics combined with zero-expansion materials to reduce the influence of slight deformation of the Fizeau interferometer cavity 16 on the measurement due to external temperature changes.

[0052] In this embodiment, combined with Figure 4 The method of measuring laser wavelength using a high-precision wide-spectrum wavelength measurement device is described:

[0053] The laser wavelength value is measured by the linear filter 14 and the photodetector 15 ,set up In Level and Between the interference fringes;

[0054] According to the pre-calibrated wedge angle of the Fizeau interference cavity 16 The phase of the interference fringes generated by the Fizeau interferometer 16 is obtained by the linear detector 17. , and obtain the wavelength Corresponding height ;

[0055] Calculate the height according to the following formula :

[0056] ;

[0057] Among them, int() is the rounding function;

[0058] The level is calculated according to the following formula :

[0059] ;

[0060] Calculate according to the following formula Level height :

[0061] ;

[0062] Calculate according to the following formula Level height :

[0063] ;

[0064] Calculate according to the following formula Wavelength value at level :

[0065] ;

[0066] Calculate according to the following formula Wavelength value at level :

[0067] ;

[0068] Get the final wavelength value:

[0069] .

[0070] In summary, the present invention proposes a high-precision wide-spectrum wavelength measurement device and method, which uses a measurement method that combines a linear filter 14 and a Fizeau interferometer cavity 16 to solve the measurement problem that the Fizeau interferometer type cannot take into account both measurement accuracy and spectral range, and has the advantages of high accuracy, wide wavelength range coverage and fast response.

Claims

1. A method for measuring the wavelength of a laser using a high-precision wide-spectrum wavelength measuring device, the high-precision wide-spectrum wavelength measuring device comprising a spectrometer (13), a linear filter (14), a photodetector (15), a Fizeau interferometer (16) and a linear detector (17), the spectrometer (13) being used for splitting a laser beam to be measured to generate a first light beam and a second light beam, the linear filter (14) and the photodetector (15) being sequentially arranged on a transmission light path of the spectrometer (13) along a light transmission direction, the linear filter (14) being used for receiving the first light beam and modulating the light signal into a signal whose light intensity varies linearly with the wavelength, and then the photodetector (15) detecting the signal; the Fizeau interferometer (16) and the linear detector (17) being sequentially arranged on a reflection light path of the spectrometer (13) along a light transmission direction, the second light beam interfering after entering the Fizeau interferometer (16) to generate interference fringes; the linear detector (17) being used for measuring the interference fringes and obtaining a period value and a phase value of the interference fringes; It is characterized in that The method includes: The laser wavelength value is measured according to the linear filter (14) and the photoelectric detector (15). ,set up In Level and Between the interference fringes; According to the pre-calibrated wedge angle of the Fizeau interferometer cavity (16) The phase of the interference fringes generated by the Fizeau interferometer cavity (16) is obtained by the linear detector (17). , and obtain the wavelength Corresponding height ; Calculate the height according to the following formula : ； Among them, int() is the rounding function; The level is calculated according to the following formula : ； Calculate according to the following formula Level height : ； Calculate according to the following formula Level height : ； Calculate according to the following formula Wavelength value at level : ； Calculate according to the following formula Wavelength value at level : ； Get the final wavelength value: 。 2. The method according to claim 1, It is characterized in that The Fizeau interferometer cavity (16) needs to be calibrated before use. During the calibration, a laser with a known wavelength is used according to Wedge angle of the Fizeau interferometer (16) To perform calibration, Indicates the known wavelength of the calibration laser, in μm; Indicates the interference fringe spacing in mm.

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