Laser wavelength measurement light path, measurement method and system

Abstract

The invention discloses a laser wavelength measurement light path, a measurement method and a system. The measuring light path comprises an optical fiber, a parabolic reflector, a 45-degree spectroscope, a wedge, a cylindrical lens, a linear array detector and the like. Incident light is changed into parallel light after passing through the optical fiber and the parabolic reflector; interference fringes are formed on the wedges after passing through the 45-degree spectroscope; and the interference fringes are converged to the linear array detector after passing through the 45-degree spectroscope and the cylindrical lens. The method comprises the following steps: calibrating a wedge by using laser with a known wavelength; during measurement, calibration data needs to be called to process the laser interference fringes to be measured, and the wavelength to be measured is obtained. A plurality of wedges with different heights are used for cooperative measurement, so that the measurement precision can be improved. The thermal expansion effect and the air refractive index change can influence the measurement precision, and in a high-precision wavelength measurement scene, a wedge made of a low-expansion material needs to be used for temperature control, and the air refractive index is calibrated in real time. According to the laser wavelength measurement optical path, the measurement method and the measurement system, the wavelength measurement with MHz precision can be realized.

Description

Technical Field

[0001] The present application relates to the field of laser wavelength measurement, and in particular, to a laser wavelength measurement optical path, measurement method and system. Background Art

[0002] High-precision laser wavelength measurement technology is a key technology in modern precision measurement science. It plays an important role in many fields such as optics, physics, materials science, biomedicine and precision manufacturing. High-precision laser measurement can not only provide accurate data of laser wavelength, but also is crucial for understanding and controlling the characteristics of lasers. It has an important impact on achieving more accurate optical system design, improving the performance of communication systems, and ensuring product quality in precision manufacturing and microelectronics. In recent years, laser application technology has developed rapidly, especially in the fields of precision measurement such as quantum communication, quantum control, quantum computing, cold atom physics, optical frequency standards and atom interferometers, which have made new progress, thus putting forward higher requirements for the measurement accuracy of laser wavelength. Therefore, it is very necessary to study the high-precision measurement methods and devices for laser wavelength. Summary of the invention

[0003] In order to solve the above technical problems, the present application provides a laser wavelength measurement optical path, measurement method and system, which realize high-precision measurement of wavelength by combining several wedge tips of different heights.

[0004] Specifically, the technical solution of this application is as follows:

[0005] In a first aspect, the present application discloses a laser wavelength measurement optical path, comprising:

[0006] Parallel beam shaper, composed of optical fiber and parabolic reflector, used to convert laser light into parallel light;

[0007] 45° beam splitter, located on the outgoing optical path of the parallel light beam, used for beam splitting;

[0008] A wedge tip, located behind the 45° beam splitter, is used to receive the parallel laser and form interference fringes, the upper surface of the wedge tip is coated with a partially transmissive and partially reflective film, and the bottom surface is coated with a high-reflective film;

[0009] The cylindrical lens is located between the linear array detector and the 45° beam splitter and is used to focus light along the stripe direction;

[0010] The interference fringes pass through the 45° beam splitter and cylindrical lens in sequence and converge to the linear array detector for detection;

[0011] The wedge tips include: first-stage wedge tips, second-stage wedge tips, third-stage wedge tips, etc.; wavelength measurement is performed by analyzing interference fringe data generated by the wedge tips; the wedge tips are fixed on a low-expansion material substrate, and the substrate temperature is controllable to suppress the influence of thermal expansion on wavelength measurement.

[0012] The first level of splitting needs to meet the following requirements:

[0013] βk≤N; or βμ×λ / Δλ≤N×μ;

[0014] The second level splitting and the third level splitting should meet the following conditions:

[0015] β×2D 一级 / λ<N;

[0016] │2D 二级 / λ-2D 二级 / (λ±δλ 一级 )│<1;

[0017] │2D 三级 / λ-2D 三级 / (λ±δλ 二级 )│<1;

[0018] The fringe spacing generated by the wedge tips at each level in the corresponding optical path satisfies:

[0019] L = λ / (2sinθ)≤N×μ;

[0020] Where k is the number of fringes; β is the detector resolution factor; μ is the detector pixel size; βμ is the detector resolution limit, and the β value range is 0<β≤1. β=1 means that the detector resolution limit is one pixel. System optimization can improve the resolution limit, and the corresponding β is less than 1; N is the number of detector pixels; Δλ is the wavelength change; λ is the wavelength; δλ 一级 : First-order wedge measurement uncertainty, δλ 二级 : Second-order wedge measurement uncertainty, D 一级 : Height of the first level wedge; D 二级 : Height of the second level wedge tip; D 三级 : height of the third-level wedge tip; θ: wedge tip inclination angle, sinθ≈tanθ≈θ; L: fringe spacing.

[0021] The wavelength measurement uncertainty of each level of the wedge is evaluated by the following formula:

[0022] δλ=βμ×2sinθ / k;

[0023] Where, δλ: wavelength measurement uncertainty; k: fringe order.

[0024] In a second aspect, the present application further discloses a laser wavelength measurement method, based on the wavelength measurement optical path described in any one of the above embodiments, comprising the following steps:

[0025] Using a laser of known wavelength to calibrate the wedge tip, respectively obtain data of the height of the wedge tip at each level changing with position, and archive them for future use;

[0026] The laser to be measured is incident, and interference fringes can be obtained respectively by the wedge tips at each level and their corresponding detectors; the calibration data is called, and the interference fringes of the laser to be measured are processed to obtain the wavelength of the laser to be measured;

[0027] The wedge tip is fixed on a low expansion material substrate, the substrate is temperature controlled, environmental parameters are monitored in real time during calibration and measurement, and calibration and measurement data are corrected to improve the accuracy of wavelength measurement.

[0028] The present application discloses a laser wavelength measurement method, wherein the laser of known wavelength is used to calibrate each level of the wedge tip, and the method comprises the following steps:

[0029] The coordinate axis associated with the position of the wedge tip is established on the linear array detector at the wavelength λ 0 The interference fringes are measured under the laser, and the position x of a fringe is selected. k As the position to be calibrated, assume that the order of the corresponding stripe is k; change the laser wavelength to λ 1 , the stripes will move when x k When the position of a new fringe coincides with the position of a new fringe, the order of the new fringe is recorded as m; although k and m are unknown, the change in the order of the fringe is certain, that is, km is certain; from the interference condition, the position x can be obtained k Corresponding wedge height D k ,as follows:

[0030] Dark pattern: 2D k / λ 0 = k;

[0031] Bright pattern: 2D k / λ 0 = k-1 / 2;

[0032] Dark pattern: 2D k / λ 1 =m;

[0033] Bright pattern: 2D k / λ 1 =m-1 / 2;

[0034] Δk = km;

[0035] λ 0 ,λ 1and Δk are both definite quantities, from which the position x can be determined k Corresponding wedge height D k ;

[0036] By changing the laser wavelength and selecting a new position to repeat the above steps, data of different positions and their corresponding wedge tip heights can be obtained. These data can be fitted to obtain a relationship curve between position and wedge tip height.

[0037] In some embodiments, when the wavelength tuning of the laser used for calibration is limited and insufficient to make the new and old interference fringes overlap, or the determination of fringes overlap is limited, the second method can be used for calibration, and the steps are as follows:

[0038] The coordinate axis associated with the position of the wedge tip is established on the linear array detector at the wavelength λ 0 The interference fringes are measured under the laser, and the positions of each level of fringes are recorded. k , x k+1 , ...; Assume that the corresponding wedge height at the stripe position is D k , D k+1 , ...; change the wavelength to λ 1 , record the new position x′ of each level of stripes k , x′ k+1 , ...; Assume that the corresponding wedge height is D' k , D′ k+1 ,……;

[0039] sinθ=λ 0 / 2(x k+1 -x k )=λ 0 / 2(x k+2 -x k+1 )=……=λ 1 / 2(x′ k+1 -x′ k )=λ 1 / 2(x′ k+2 -x′ k+1 )

[0040] =……=(D′ k -D k ) / (x′ k -x k )=(D′ k+1 -D k+1 ) / (x′ k+1 -x k+1 ) = ...;

[0041] By dark fringe condition: 2D k / λ 0 =2D′ k / λ 1= k;

[0042] We get: k = [2(x′ k -x k )sinθ / (λ 1 -λ 0 )];

[0043] Or by bright grain condition: 2D k / λ 0 =2D′ k / λ 1 = k-1 / 2;

[0044] We get: k = [2(x′ k -x k )sinθ / (λ 1 -λ 0 )+1 / 2];

[0045] Among them, sinθ is an intermediate quantity that does not need to be actually solved; […] indicates rounding (the same below);

[0046] After determining the fringe order k, the wedge height corresponding to each fringe position can be obtained as follows:

[0047] Dark pattern: D k = kλ 0 / 2,D k+1 =(k+1)λ 0 / 2,……,D′ k = kλ 1 / 2,D′ k+1 =(k+1)λ 1 / 2,……;

[0048] Bright grain: D k =(k-1 / 2)λ 0 / 2,D k+1 =(k+1-1 / 2)λ 0 / 2,……,D′ k =(k-1 / 2)λ 1 / 2,D′ k+1 =(k+1-1 / 2)λ 1 / 2,……;

[0049] By repeating the above steps under different wavelength conditions, the wedge tip height data corresponding to different position coordinates can be obtained. These data are fitted to obtain a relationship curve between the position coordinates and the corresponding wedge tip height.

[0050] The present application discloses a laser wavelength measurement method, which further includes: obtaining a wavelength value to be measured by first-stage wedge cutting, specifically including the following steps:

[0051] When the laser of the wavelength to be measured is incident, the first-stage wedge will measure the interference fringes, and the fringes position x k , x k+1 , ...; and the corresponding wedge height is obtained from the coordinate curve of the first wedge as D k , D k+1 ,……;

[0052] λ 测0 =2(D k+1 -D k )=2(D k+2 -D k+1 ), λ 测0 is the rough value of the measured wavelength;

[0053] Dark pattern: k = [2D k / λ 测0 ],k+1=[2D k+1 / λ 测0 ], …;

[0054] Bright fringe: k = [2D k / λ 测0 +1 / 2],k+1=[2D k+1 / λ 测0 +1 / 2], ...;

[0055] Dark pattern: λ 测1 =2D k / k=2D k+1 / (k+1)=……;

[0056] Bright grain: λ 测1 =2D k / (k-1 / 2)=2D k+1 / (k+1-1 / 2)=……;

[0057] Output λ from the above formula 测0 and λ 测1 Before calculating the result, we can take the average value to reduce the error; 测0 The relative uncertainty limit of is 1 / N, where N is the number of pixels in the detector; 测1 The relative uncertainty limit is μ 1 ×2sinθ 1 / k,θ 1 and μ 1 They are respectively the top angle of the first-stage wedge and the detector pixel size corresponding to the wedge.

[0058] In some embodiments, the laser wavelength measurement method further includes: obtaining a wavelength value to be measured by a second-stage wedge, specifically including the following steps:

[0059] When the laser of the wavelength to be measured is incident, interference fringes are measured by the first and second level wedges, wherein the measurement data obtained by the first level wedge is processed according to claim 7 to obtain the wavelength measurement value λ 测1 ;

[0060] The interference fringe position of the second wedge tip is x K , x K+1 , ...; and the corresponding wedge height is obtained from the calibration curve of the second wedge as D K , D K+1 ,……;

[0061] Dark pattern: K = [2D K / λ 测1 ],K+1=[2D K+1 / λ 测1 ], …;

[0062] Bright grain: K = [2D K / λ 测1 +1 / 2],K+1=[2D K+1 / λ 测1 +1 / 2], ...;

[0063] Dark pattern: λ 测2 =2D K / K=2D K+1 / (K+1)=……;

[0064] Bright grain: λ 测2 =2D K / (K-1 / 2)=2D K+1 / (K+1-1 / 2)=……;

[0065] Output λ from the above formula 测2 Before calculating the result, we can take the average value to reduce the error; 测2 The relative uncertainty limit is μ 2 ×2sinθ 2 / K,θ 2 and μ 2 are the second-stage wedge apex angle and the corresponding detector pixel size respectively.

[0066] In some embodiments, the laser wavelength measurement method further includes: obtaining a wavelength value to be measured by a third-level wedge, specifically including the following steps:

[0067] The laser to be measured is incident, and interference fringes are measured by the first, second and third level wedges. The fringes of the first and second level wedges are processed according to claims 7-8 to obtain the measured value λ 测2 ;

[0068] The interference fringe position of the third wedge is xM , x M+1 , ...; and the corresponding wedge height is obtained from the calibration curve of the third wedge as D M , D M+1 ,……;

[0069] Dark pattern: M = [2D M / λ 测2 ],M+1=[2D M+1 / λ 测2 ], …;

[0070] Bright lines: M = [2D M / λ 测2 +1 / 2],M+1=[2D M+1 / λ 测2 +1 / 2], ...;

[0071] Dark pattern: λ 测3 =2D M / M=2D M+1 / (M+1)=……;

[0072] Bright grain: λ 测3 =2D M / (M-1 / 2)=2D M+1 / (M+1-1 / 2)=……;

[0073] Output λ from the above formula 测3 Before calculating the result, we can take the average value to reduce the error; 测3 The relative uncertainty limit is μ 3 ×2sinθ 3 / K,θ 3 and μ 3 are the third-level wedge apex angle and the corresponding detector pixel size respectively.

[0074] In a third aspect, the present application further discloses a laser wavelength measurement system, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the laser wavelength measurement method described in any one of the above embodiments of the claims.

[0075] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0076] First, a wavelength measurement optical path using a single wedge and a detector to achieve a wavelength measurement accuracy of 0.0001nm or better was proposed, and a wavelength measurement optical path using a multi-stage wedge and a detector to achieve a measurement accuracy of 0.001pm or better was proposed, which also provided a technical solution for higher-precision wavelength measurement.

[0077] Secondly, a scheme for wedge calibration and a method for high-precision wavelength measurement are proposed. During the calibration and measurement process, the wedge height (the optical path is proportional to the wedge height) and the fringe order are always anchored, and the fringe order is measured to be completely accurate and error-free. This allows the wedge height to be calibrated to a very high precision, eliminating measurement errors caused by other possible factors. The wavelength measurement accuracy is limited only by the resolution of the measuring device to the changes in the interference fringes, thereby improving the accuracy of wavelength measurement.

[0078] Third, a detailed analysis was conducted on the uncertainty of the wavelength measurement results, and the constraints that need to be met for high-precision wavelength measurement were determined. The technical route of how to use the method described in this application to implement multiple wedge tips to gradually improve the measurement accuracy was explained, which has guiding significance for the design and development of high-precision wavelength measurement devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] The preferred implementation scheme will be described below in a clear and understandable manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present application.

[0080] Figure 1 This is a schematic diagram of the principle of the laser wavelength measurement method of this application;

[0081] Figure 2 A schematic diagram of an embodiment of a laser wavelength measurement optical path disclosed in the present application;

[0082] Figure 3 Schematic diagram of the displacement of interference fringes;

[0083] Figure 4 Schematic diagram of the displacement of interference fringes and their coincidence with the next level fringes;

[0084] Figure 5 A schematic diagram of another embodiment of a laser wavelength measurement optical path disclosed in the present application;

[0085] Figure 6 A schematic diagram of another embodiment of a laser wavelength measurement optical path disclosed in the present application;

[0086] Figure 7 A flowchart of the steps of an embodiment of a laser wavelength measurement method disclosed in the present application;

[0087] Figure 8 In the embodiment of the present application, the position x of the k-th level stripe is selected. k Schematic diagram of

[0088] Fig. 9 This is a schematic diagram of the stripes moving left and right in the embodiment of the present application;

[0089] Fig.10A fitting image of the detector pixel position and the wedge tip height at the corresponding position in one embodiment of a laser wavelength measurement method of the present application;

[0090] Fig.11 This is a fitting image of the detector pixel position and the wedge tip height at the corresponding position in another embodiment of a laser wavelength measurement method of the present application.

[0091] Reference numerals:

[0092] 10, wedge; 20, linear array detector; 30, interference fringes; 40, optical fiber; 50, parabolic reflector; 60, 45° beam splitter; 70, cylindrical lens; 11, first-order wedge; 12, second-order wedge; 13, third-order wedge; D, wedge height; H, wedge length; θ, wedge inclination angle. DETAILED DESCRIPTION

[0093] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0094] It should be understood that when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or collections.

[0095] In order to simplify the drawings, only the parts related to the invention are schematically shown in each figure, and they do not represent the actual structure of the product. In addition, in order to simplify the drawings and facilitate understanding, in some figures, only one of the parts with the same structure or function is schematically drawn or marked. In this article, "one" not only means "only one", but also means "more than one".

[0096] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0097] In this document, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0098] In addition, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0099] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the specific implementation methods of the present application will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings and other implementation methods can be obtained based on these drawings without creative work.

[0100] The laser wavelength measurement principle used in this application is as follows Figure 1 As shown, the incident laser is incident from the upper surface of the wedge tip 10, and when reflected from the upper and lower surfaces of the wedge tip 10, interference fringes 30 are generated. The generated interference fringes 30 are received by the linear array detector 20. Figure 1 , where D is the height of the wedge tip; H is the length of the wedge tip; θ is the inclination angle of the wedge tip.

[0101] Optionally, in the present application, λ is set as the wavelength of the incident laser; L is the spacing of the generated interference fringes; μ is the pixel size of the linear array detector; N is the number of pixels of the linear array detector; k is the fringe order of a certain interference fringe generated; x k is the position of the kth order fringe. When the laser wavelength changes, the interference fringe spacing and fringe order will change, from which the information of the laser wavelength can be obtained, thus accurately measuring the wavelength.

[0102] The present application discloses an embodiment of a laser wavelength measurement optical path, such as Figure 2 As shown, including:

[0103] A parallel beam shaper, which is composed of an optical fiber 40 and a parabolic reflector 50, wherein the light outlet of the optical fiber 40 is located at the focus of the parabolic reflector 50, and is used to convert the laser into parallel light;

[0104] A 45° beam splitter 60, located on the outgoing optical path of the parallel light beam, for receiving the laser and performing beam splitting;

[0105] The primary wedge tip 11 is located behind the 45° beam splitter 60 and is used to receive the parallel laser. The upper surface of the wedge tip is coated with a partially transmissive and partially reflective film and the bottom surface is coated with a highly reflective film, and interference fringes are formed on the upper surface of the wedge tip.

[0106] The interference fringes are sequentially passed through a 45° beam splitter 60 and a cylindrical lens 70 and converged to a linear array detector, where the interference fringes 30 are detected by the linear array detector 20;

[0107] The wavelength is measured by analyzing the interference fringe data generated by the wedge tip 11;

[0108] In order to improve the measurement accuracy, an optical path is formed by multiple groups of wedge tips of different heights. The wedge tips are named first-level wedge tip, second-level wedge tip, third-level wedge tip, etc. from low to high. Each wedge tip constitutes a group of measurement optical paths. The laser beam to be measured is split and passes through these measurement optical paths respectively, thereby gradually improving the wavelength measurement resolution and measurement accuracy.

[0109] The parameters of the wedge-tip and linear array detectors should meet the following conditions:

[0110] (1) L = λ / (2sinθ) ≤ N×μ;

[0111] (2) D / sinθ ≥ βμ×λ / Δλ;

[0112] (3) βk ≤ N or βμ×λ / Δλ ≤ N×μ;

[0113] Among them, L is the spacing of the generated interference fringes; λ is the wavelength of the incident laser; θ is the inclination angle of the wedge tip; D is the height of the wedge tip; β is the resolution coefficient of the linear array detector; μ is the pixel size of the linear array detector; Δλ is the change in the wavelength of the incident laser; N is the number of pixels in the linear array detector; k is the fringe order of a certain interference fringe generated.

[0114] Formula (1) indicates that the linear array detector can detect at least one interference fringe.

[0115] Formula (2) indicates that when the wavelength changes by Δλ, the interference fringes on the wedge tip move at least greater than the minimum value that the detector can resolve, which is βμ.

[0116] Formula (3) indicates that the wavelength changes by Δλ, causing the k±1-level fringes to overlap with the original k-level fringes, and the detector can distinguish the difference between the new and old fringes.

[0117] The linear array detector resolution coefficient β described in formulas (2) and (3) can be a decimal, and βμ represents the minimum value of the interference fringe change that can be read and resolved by the hardware and software involved in the detector.

[0118] Because θ is very small, sinθ≈tanθ≈θ. Choosing sinθ, tanθ or θ for expression does not affect the physical meaning of the formula and the meaning of the formula described in this application.

[0119] The physical meaning of formula (2) is that when the wavelength changes by a small amount Δλ, the interference fringes will move slightly. The detector must be able to distinguish the slight movement of the fringes in the detection area to achieve high-precision wavelength measurement, such as Figure 3 Taking the example of a slight rightward movement of a bright fringe, using bright fringe / dark fringe or rightward / leftward movement as a demonstration does not affect the understanding of the physical meaning of formula (2).

[0120] The physical meaning of formula (3) is that when the wavelength changes by a small amount, so that the k+1 level / or k-1 level fringe of the new interference fringe overlaps with the k level fringe of the original interference fringe, and the two adjacent fringes of the two interference fringes overlap, the detector must be able to distinguish the difference between the new and old fringes in the detection area, otherwise high-precision measurement cannot be achieved. Figure 4 Here, we take the example of a k-1 level bright fringe moving to the right and coinciding with the original k level bright fringe. The selection of bright fringe or dark fringe and the selection of fringe level k±1 do not affect the understanding of the physical meaning of formula (3).

[0121] If the wavelength measurement accuracy requirement is not too high, a single wedge tip and detector combination may be able to simultaneously satisfy the constraints described in formulas (2) and (3), that is, a single wedge tip and detector combination can complete the required wavelength measurement; however, when the wavelength measurement accuracy requirement is higher, a single wedge tip and detector combination cannot simultaneously satisfy the constraints described in formulas (2) and (3). In this case, multiple wedge tip and detector combinations are required to satisfy one of the conditions described in formulas (2) or (3), that is, multiple wedge tip and detector combinations can jointly complete higher-precision wavelength measurement.

[0122] If two or more wedges are used to perform high-precision wavelength measurement, the relationship between the wedges needs to meet additional conditions. We denote the heights of the first-stage wedge, the second-stage wedge, etc. as D 一级 , D 二级 , D 三级 , ..., etc.; let the wavelength measurement uncertainty be δλ, then the conditions that need to be met at each level of wedge are:

[0123] (4)β×2D 一级 / λ<N;

[0124] │2D 二级 / λ-2D 二级 / (λ±δλ 一级 )│<1;

[0125] │2D三级 / λ-2D 三级 / (λ±δλ 二级 )│<1;……;etc.

[0126] The physical meaning of formula (4) is: the height of the first-order wedge must satisfy the constraint of formula (3); the uncertainty in the measurement of the wavelength of the first-order wedge cannot cause an error of ≥1 in the fringe order of the second-order wedge, that is, the wavelength accuracy measured by the first-order wedge is sufficient to determine the interference fringe order of the second-order wedge; the uncertainty in the measurement of the wavelength of the second-order wedge cannot cause an error of ≥1 in the fringe order of the third-order wedge, that is, the wavelength accuracy measured by the second-order wedge is sufficient to determine the interference fringe order of the third-order wedge; the corresponding conditions for higher-order wedges are similar.

[0127] The wavelength measurement uncertainty of each level of wedge is evaluated by the following formula:

[0128] (5)δλ=βμ×2sinθ / k;

[0129] Among them, k is the fringe order corresponding to the wedge tip; sinθ is the sine corresponding to the inclination angle of the wedge tip. Because the inclination angle is very small, it can be approximated as sinθ≈tanθ≈θ, etc.

[0130] It can be seen from formula (5) that as the height of the wedge increases, the number of fringes also increases accordingly, and the measurement uncertainty decreases accordingly. By combining multiple wedge optical paths, high-precision wavelength measurement can be achieved.

[0131] Embodiment 1 of the wavelength measurement optical path: The present application provides an embodiment of a laser wavelength measurement optical path, and its optical structure is designed as follows Figure 2 As shown, the laser wavelength measurement optical path only includes the first group of measurement optical paths.

[0132] It includes an optical fiber 40 , a parabolic reflector 50 , a 45° beam splitter 60 , a first-order split tip 11 , a cylindrical lens 70 and a linear array detector 20 .

[0133] The spectral response range of the linear array detector is 350nm-1100nm, and the pixel specification is 3.5um×16384 for example, that is, the pixel size μ=3.5um, and the number of pixels N=16384.

[0134] This example has only one primary wedge tip, the height of the designed wedge tip is 350 microns, and the inclination angle of the wedge tip is 0.0001 radians. The production of the primary wedge tip can be completed by the following steps: two circular glass sheets are brought close together, two quartz wires with a diameter of 350 microns are inserted into the glass gaps at both ends of the glass sheets to form a small angle, and then fixed by mechanical compression or chemical bonding.

[0135] It can be seen from the various specifications of this embodiment that within the detector spectral response range of 350nm-1100nm, the conditions such as L=λ / (2sinθ)≤N×μ and βk=β×2D / λ≤N (taking β=1) are satisfied; the relative uncertainty limit that can be achieved in the wavelength measurement of this embodiment is:

[0136] E=δλ / λ=βμ×2sinθ / (λk)=μ×sinθ / D=1×10 -6 (take β = 1);

[0137] The thermal expansion coefficient of quartz material is about 5.5×10 -7 / ℃, which means that the height of the wedge tip will increase by about 5×10 -7 Relative change; it is possible to consider temperature control of the wedge tip in order to achieve stable and reliable wavelength measurement; temperature control is performed on the side or bottom of the wedge tip with a temperature control accuracy of 0.1°C, so that the influence of thermal expansion effect is reduced to 5×10 -8 , much smaller than 1×10 -6 , which can be regarded as eliminating the influence of thermal expansion factors.

[0138] In some embodiments, the two glass pieces that make up the primary cleave tip may not be circular.

[0139] In some embodiments, a cylindrical reflector may be used instead of a cylindrical lens, and only the position of the linear array detector needs to be changed.

[0140] In some embodiments, the inclination angle, height and detector pixel specifications of the first-level wedge may be different from those set in this embodiment, but must meet the constraints described in this application, and the measurement accuracy limit is determined by E=δλ / λ=βμ×2sinθ / (λk)~μ×sinθ / D.

[0141] In some embodiments, the quartz wire used to make the cleavage tip can be replaced by a quartz sheet, or other materials with low thermal expansion effect, including but not limited to ultra-low thermal expansion glass / ULE glass, etc.

[0142] In some embodiments, temperature control of the wedge tip may not be necessary, but the wavelength measurement accuracy may be reduced.

[0143] Embodiment 2 of the wavelength measurement optical path: The present application provides another embodiment of a laser wavelength measurement optical path, wherein the laser wavelength measurement optical path includes a first group of measurement optical paths and a second group of measurement optical paths.

[0144] Specifically, in the first embodiment of the above wavelength measurement optical path ( Figure 2 ), a set of similar and relatively independent measurement optical paths is added, and its optical structure is as follows Figure 5 As shown. Among them, Figure 2The middle-level wedge 11 and its corresponding linear array detector 20 are the same as those described in the above embodiment; the linear array detector 20 is a first linear array detector. Figure 5 The design height of the secondary wedge 12 is 35 mm, and the inclination angle of the wedge is 0.0001 radians; the linear array detector 20 corresponding to the secondary wedge 12 is a second linear array detector, and its specifications are the same as those of the aforementioned first linear array detector.

[0145] The production of the secondary split tip in this embodiment can be completed by the following steps: use ultra-low thermal expansion glass / ULE glass to make a hollow base frame with a length of 35 mm, and fix the two circular glass pieces that constitute the split tip at both ends of the base frame to form a small angle.

[0146] From the specifications of the wedge tips and detectors in this embodiment, it can be seen that the design height of the secondary wedge tip is 35 mm to meet the requirements of |2D 二级 / λ-2D 二级 / (λ±δλ 一级 )│<1The above-mentioned condition constraints meet the requirements within the detector spectral response range of 350nm-1100nm.

[0147] The relative uncertainty that can be achieved in measuring wavelength in this embodiment is:

[0148] E=δλ / λ=βμ×2sinθ / (λk)=μ 二级 ×sinθ 二级 / D 二级 =1×10 -8 (take β = 1);

[0149] The thermal expansion coefficient of ultra-low thermal expansion glass / ULE glass is generally 10 -8 / ℃, to achieve a relative uncertainty of 1×10 -8 To measure the wavelength accurately, the temperature of the cleaved substrate must be controlled. If the temperature control accuracy is set to 0.01°C, the influence of thermal expansion effect is reduced to 1×10 -10 , the influence of thermal expansion effect is considered to be eliminated.

[0150] In addition, environmental factors such as temperature, humidity and pressure can affect the refractive index of air, which can affect the uncertainty of wavelength measurement by about 1×10 -8 So, for a relative uncertainty of 1×10 -8 To achieve high-precision wavelength measurement, the environmental conditions must be monitored in real time, and the measurement results must be corrected according to the environmental parameters to achieve high-precision wavelength measurement. This application does not elaborate on how temperature, humidity, and pressure affect the refractive index of air and how to eliminate or correct these effects.

[0151] In some embodiments, the two glass pieces that make up the secondary cleave tip may not be circular.

[0152] In some embodiments, a cylindrical reflector may be used instead of a cylindrical lens, and only the position of the linear array detector needs to be changed.

[0153] In some embodiments, the ultra-low thermal expansion glass / ULE glass material used to make the secondary cleave tip can be replaced by other low thermal expansion materials.

[0154] In some embodiments, the inclination angle, height, and detector pixel specifications of the secondary wedge tip may be different from those set in this embodiment, and only need to meet the |2D 二级 / λ-2D 二级 / (λ±δλ 一级 )│<1The above conditions can be used, and the final measurement accuracy limit is E=δλ / λ~μ 二级 ×sinθ 二级 / D 二级 Decide.

[0155] Embodiment 3 of the wavelength measurement optical path: The present application provides another embodiment of a laser wavelength measurement optical path, wherein the laser wavelength measurement optical path comprises a first group of measurement optical paths, a second group of measurement optical paths and a third group of measurement optical paths.

[0156] Specifically, based on the second embodiment of the wavelength measurement optical path, this embodiment adds a group of similar and relatively independent measurement optical paths, whose optical structure is as follows: Figure 6 The first and second level wedges and their corresponding two linear array detectors are the same as those described in the above embodiment; the third level wedge 13 is designed to have a height of 35 cm and a wedge inclination of 0.0001 radians; the linear array detector 20 corresponding to the third level wedge is a third linear array detector, and its specifications are the same as those of the first linear array detector or the second linear array detector.

[0157] Specifically, Figure 2 The first set of measurement optical paths, Figure 5 The second set of measurement optical paths and Figure 6 In the third group of measurement optical paths, the devices with the same label have the same device format, but the devices with the same label in different optical paths are not the same. Figure 2 , Figure 5 , Figure 6 The formats of the linear array detector 20, interference fringes 30, optical fiber 40, parabolic reflector 50, 45° beam splitter 60, cylindrical lens 70 and other devices are the same as those described in an embodiment of a laser wavelength measurement optical path disclosed in the present application.

[0158] The production process of the third-level wedge in this embodiment is similar to that of the second-level wedge: a hollow base frame with a length of 35 cm is made using ultra-low thermal expansion glass / ULE glass, and two circular glass pieces constituting the wedge are fixed at both ends of the base frame to form a small angle.

[0159] From the specifications of the wedges and detectors in this embodiment, it can be seen that the design height of the three-stage wedge is 35 cm to meet the requirements of |2D 三级 / λ-2D 三级 / (λ±δλ 二级 )│<1The above-mentioned condition constraints meet the requirements within the detector spectral response range of 350nm-1100nm.

[0160] The relative uncertainty that can be achieved in measuring wavelength in this embodiment is:

[0161] E=δλ / λ=βμ×2sinθ / (λk)=μ 三级 ×sinθ 三级 / D 三级 =1×10 -9 (take β = 1);

[0162] To achieve a relative uncertainty of 1×10 -9 For accurate wavelength measurement, the wedge-shaped substrate skeleton made of ultra-low thermal expansion glass / ULE glass material needs to be temperature-controlled at the zero expansion point. The temperature control accuracy can be set to 0.01°C or 0.001°C, so that the influence of thermal expansion effect on the uncertainty of wavelength measurement can be ignored.

[0163] In addition, to achieve a relative uncertainty of 1×10 -9 High-precision wavelength measurement also requires real-time monitoring of environmental factors such as temperature, humidity and pressure, and correction of measurement results based on environmental parameters to ultimately achieve high-precision wavelength measurement.

[0164] In some embodiments, the two glass pieces that make up the tertiary cleave tip may not be circular.

[0165] In some embodiments, a cylindrical reflector may be used instead of a cylindrical lens, and only the position of the linear array detector needs to be changed.

[0166] In some embodiments, the ultra-low thermal expansion glass / ULE glass material used to make the tertiary cleave tip can be replaced by other low thermal expansion materials.

[0167] In some embodiments, the inclination angle, height and detector pixel specifications of the three-stage wedge tip may be different from those set in this embodiment, and only need to meet the |2D 三级 / λ-2D 三级 / (λ±δλ 二级)│<1The above conditions can be used, and the final measurement accuracy limit is E=δλ / λ~μ 三级 ×sinθ 三级 / D 三级 Decide.

[0168] Although a preferred embodiment of the laser wavelength measurement optical path of the present application has been described, those skilled in the art can learn from the present application the basic creative concept of the high-precision wavelength meter design and may make other changes and modifications to these embodiments, including but not limited to: continuing to increase the number of wedges; changing the height and angle parameters of the wedges at each level; changing the specification parameters of the detectors at each level; and combining wedges and detectors with other different parameters for measurement.

[0169] Based on the same concept, the present application also discloses a method for measuring laser wavelength, which is applied to the laser wavelength measurement optical path described in any of the above embodiments, such as Figure 7 As shown, a method for measuring laser wavelength in this embodiment includes the following steps:

[0170] S100, wedge tip calibration: using a laser with a known wavelength to calibrate the wedge tip, respectively obtaining data of the height of the wedge tip at each level changing with position, and respectively archiving the data for future use;

[0171] S200, wavelength measurement: laser light of the wavelength to be measured is incident, and the linear array detectors of each level of wedge tip and its corresponding optical path can respectively obtain corresponding interference fringes; the archived calibration data is called, and the obtained interference fringes of the laser light to be measured are processed to obtain the wavelength of the laser light to be measured.

[0172] Optionally, in this embodiment, the wedge tip is fixed on a low-expansion material substrate, and the wedge tip substrate is temperature controlled. During the wedge tip calibration and wavelength measurement process, the environmental parameters are monitored in real time, and the calibration data and measurement data are corrected to improve the accuracy of wavelength measurement.

[0173] The present application discloses a method for measuring laser wavelength, wherein there are two ways of wedge calibration, which can be selected and used according to the actual situation. There are also different steps for wavelength measurement, corresponding to wavelength measurement optical paths with different numbers of wedges and different measurement accuracy.

[0174] An embodiment of a method for measuring laser wavelength disclosed in the present application, wherein the steps of “wedge calibration” are as follows:

[0175] The coordinate axis associated with the position of the wedge tip is established on the linear array detector. 0 The interference fringes are measured under the laser, and the position x of any fringes is selected. kAssume that the order of the corresponding fringe is k; slowly change the wavelength of the laser, the interference fringe will move slowly. 1 When the calibration position coincides with the position of a new fringe, the order of the new fringe is recorded as m; although the order k and the order m are unknown, the order of the fringe movement is determined, that is, km can be determined by counting the fringe movement; from the interference condition, the calibration position x can be obtained k The corresponding wedge height D k Then select other positions and repeat the above steps for calibration, and fit the obtained wedge tip height data to obtain the relationship curve between the wedge tip height and the position, which is the calibration result.

[0176] Step 1: Establish a coordinate axis by taking the linear array detector as part of the coordinate axis.

[0177] Step 2: Measure known wavelength λ 0 The corresponding interference fringes. Select the position x of one of the fringes k , either bright or dark fringe is acceptable, k is the fringe level, and the k value is unknown, such as Figure 8 As shown. Increasing or decreasing the wavelength of the laser will cause the stripes to move left or right. Fig. 9 shown.

[0178] When position x k The point coincides with a certain fringe, either a bright fringe or a dark fringe, and the number of fringe movements Δk and the corresponding wavelength λ are recorded. 1 . And the current position x k The number of new fringes at is denoted by m.

[0179] According to the interference condition, the position x k The corresponding wedge height D k Should meet:

[0180] (6)2D k / λ 0 = k(dark pattern) or 2D k / λ 0 = k-1 / 2 (bright lines);

[0181] (7)2D k / λ 1 =m(dark pattern) or 2D k / λ 1 =m-1 / 2(bright lines);

[0182] (8) Δk = km;

[0183] In the above formulas (6), (7), and (8), λ 0 , 1and Δk are known, the position x can be uniquely determined by solving the equation k The corresponding wedge height D k .

[0184] Step 3: Change the laser wavelength and select a new position for calibration. You can get a set of data on the wedge tip height corresponding to different positions. These data are tabulated as follows:

[0185] Coordinate axis position x <![CDATA[x k ]]> <![CDATA[x i ]]> <![CDATA[x j ]]> <![CDATA[x l ]]> <![CDATA[x s ]]> <![CDATA[x p ]]> <![CDATA[x d ]]> <![CDATA[x f ]]> <![CDATA[x g ]]> <![CDATA[x h ]]> …… Wedge tip height D <![CDATA[D k ]]> <![CDATA[D i ]]> <![CDATA[D j ]]> <![CDATA[D l ]]> <![CDATA[D s ]]> <![CDATA[D p ]]> <![CDATA[D d ]]> <![CDATA[D f ]]> <![CDATA[D g ]]> <![CDATA[D h ]]> ……

[0186] Step 4: With x as the horizontal coordinate and D as the vertical coordinate, fit the data of position x and wedge height D to obtain the wedge height corresponding to any horizontal axis coordinate on the linear array detector. Fig.10 shown.

[0187] The slope of the fitted image is related to the wedge tip inclination angle θ, which indicates the size of sinθ, tanθ or θ.

[0188] In some embodiments, for a position x k The corresponding wedge height D k The above method can be used to measure multiple times, and then average or fit to get the final D k value.

[0189] In some embodiments, when selecting stripes, only bright stripes may be selected, only dark stripes may be selected, or both bright stripes and dark stripes may be selected. However, it should be noted that the interference conditions corresponding to bright stripes and dark stripes are different.

[0190] Preferably, the present embodiment involves determining the interference fringe position, and the fringe position information can be read from a detector or obtained through software fitting processing.

[0191] Another embodiment of a laser wavelength measurement method of the present application specifically explains the second wedge calibration step. When the wavelength tuning of the laser used for wedge calibration is limited and insufficient to complete the overlap of the new interference fringes with the original interference fringes, or the determination of the overlap of the interference fringes is limited, the second method can be used to perform wedge calibration. As follows:

[0192] The coordinate axis associated with the position of the wedge tip is established on the linear array detector. 0 The interference fringes are measured under the laser, and the positions of each level of fringes are recorded. k , x k+1 , ...; and assume that the corresponding wedge height at the stripe position is D k , D k+1 , ...; Change the wavelength to make the stripes move, the wavelength is λ 1 , record the new position x′ of each level of fringes k , x′ k+1, ...; and assume that the corresponding wedge height is D' k , D′ k+1 , ...; According to the interference condition, we can get different positions x k , x k+1 , ..., x′ k , x′ k+1 , ... The corresponding wedge height D k , D k+1 , ..., D′ k , D′ k+1 , etc. Then change the laser wavelength, select other positions to repeat the calibration steps, and fit the obtained wedge height data to obtain the relationship curve between the wedge height and the position, which is the calibration result. The specific steps are as follows:

[0193] Step 1: Take the linear array detector as part of the coordinate axis and establish a coordinate axis;

[0194] Step 2: The known wavelength λ 0 The laser is incident, the interference fringes are measured, and the positions of each level of fringes are recorded. k , x k+1 , ...; and assume that the corresponding wedge height at the stripe position is D k , D k+1 ,……;

[0195] Step 3: Change the wavelength to move the stripes, carefully observe the stripes of each level in step 2 move to new positions, and record the new positions x′ of each level of stripes k , x′ k+1 , ...; and assume that the corresponding wedge height is D' k , D′ k+1 , ...; at the same time, record the wavelength λ at this time 1 ;

[0196] Step 4: According to the wedge interference condition, the formula is as follows:

[0197] (9) sinθ=λ 0 / 2(x k+1 -x k )=λ 0 / 2(x k+2 -x k+1 )=……=λ 1 / 2(x′ k+1 -x′ k )=λ 1 / 2(x′ k+2 -x′ k+1 )=……=(D′ k -D k ) / (x′ k -xk )=(D′ k+1 -D k+1 ) / (x′ k+1 -x k+1 ) = ...;

[0198] (10)2D k / λ 0 =2D′ k / λ 1 = k(dark pattern);

[0199] 2D k / λ 0 =2D′ k / λ 1 = k-1 / 2 (bright lines);

[0200] (11) k = [2(x′ k -x k )sinθ / (λ 1 -λ 0 )](dark pattern);

[0201] k=[2(x′ k -x k )sinθ / (λ 1 -λ 0 )+1 / 2](bright pattern);

[0202] Among them, [] means taking an integer, sinθ is only used as an intermediate quantity and does not need to be actually solved. The above formula can be used to calculate the fringe order k, and then the corresponding wedge height at different positions can be calculated:

[0203] (12)D k = kλ 0 / 2,D k+1 =(k+1)λ 0 / 2,……,D′ k = kλ 1 / 2,D′ k+1 =(k+1)λ 1 / 2, ... (dark pattern);

[0204] D k =(k-1 / 2)λ 0 / 2,D k+1 =(k+1-1 / 2)λ 0 / 2,……,D′ k =(k-1 / 2)λ 1 / 2,D′ k+1

[0205] =(k+1-1 / 2)λ 1 / 2, ... (bright lines);

[0206] Step 5: Change the laser wavelength and select other positions for calibration. The resulting data is listed as follows:

[0207] Coordinate axis position x <![CDATA[x k ]]> <![CDATA[x k+1 ]]> <![CDATA[x k+2 ]]> …… <![CDATA[x′ k ]]> <![CDATA[x′ k+1 ]]> <![CDATA[x′ k+2 ]]> …… Wedge tip height D <![CDATA[D k ]]> <![CDATA[D k+1 ]]> <![CDATA[D k+2 ]]> …… <![CDATA[D′ k ]]> <![CDATA[D′ k+1 ]]> <![CDATA[D′ k+2 ]]> ……

[0208] Step 6: Fit the data obtained in step 5 to obtain the wedge tip height corresponding to any position on the detector. Fig.11 As shown in FIG. 1 , the slope of the fitting curve is related to the wedge tip inclination angle θ, which indicates the size of sinθ, tanθ or θ.

[0209] In some embodiments, when selecting stripes, only bright stripes may be selected, only dark stripes may be selected, or both bright stripes and dark stripes may be selected. However, it should be noted that the interference conditions corresponding to bright stripes and dark stripes are different.

[0210] Specifically, the positions of the interference fringes can be determined by reading from a detector or by fitting or processing with software.

[0211] In the above two embodiments of wedge tip calibration, the obtained fitting curve should be a straight line in most cases, and the slope of the straight line is related to the wedge tip inclination angle θ, but there are some cases where the fitting curve is not a strict straight line. For example, due to the manufacturing accuracy, the wedge tip inclination angle has a slight jump at a certain place; because the application always anchors the wedge tip height corresponding to the stripe position (which has a strict linear relationship with the optical path) during the calibration and measurement process, the wedge tip inclination angle is only used as an intermediate quantity in the calculation process, and even if the wedge tip inclination angle has a jump, it does not affect the calibration or measurement accuracy of the application.

[0212] Another embodiment of the method for measuring laser wavelength of the present application will explain the steps of "wavelength measurement" in detail. The wedge calibration must be completed before wavelength measurement, so the following wavelength measurement steps are all based on the premise that the wedge calibration data has been obtained and archived for backup. This embodiment corresponds to the case where there is only one wedge, or only one primary wedge is used for measurement and output of measurement results. The steps of wavelength measurement are as follows:

[0213] When the laser with wavelength λ to be measured is input, the first-stage wedge tip and its corresponding linear array detector 1 will measure a set of interference fringes and record the position x of the fringes. k , x k+1 , ...; and the wedge height D corresponding to the fringe position is obtained from the calibration curve of the first wedge k , D k+1 ,……;

[0214] The rough value of the wavelength to be measured is denoted as λ 测0 , according to the interference condition, λ 测0 It can be determined by the following formula:

[0215] (13)λ 测0 =2(D k+1 -D k )=2(D k+2 -D k+1 ) = ...;

[0216] At the same time, 测0 The relative uncertainty of measurement is determined by the following formula:

[0217] (14)δλ 测0 / λ 测0 ≈1 / N, where N is the number of pixels in the linear array detector;

[0218] The rough value λ 测0 Substitute and determine the order of interference fringes of the wavelength to be measured, as follows:

[0219] (15) k = [2D k / λ 测0 ],k+1=[2D k+1 / λ 测0 ], ... (dark pattern);

[0220] k=[2D k / λ 测0 +1 / 2],k+1=[2D k+1 / λ 测0 +1 / 2], ... (bright lines);

[0221] [] indicates integer;

[0222] The wavelength measurement result corresponding to the first-order wedge is:

[0223] (16)λ 测1 =2D k / k=2D k+1 / (k+1)=……(dark pattern);

[0224] λ 测1 =2D k / (k-1 / 2)=2D k+1 / (k+1-1 / 2)=……(bright lines);

[0225] (17)δλ 测1 / λ 测1 ≈μ 1 ×2sinθ 1 / (λ 测1 ×k);

[0226] Among them, θ 1 and μ 1are respectively the top angle of the first-stage wedge and the pixel size of the linear array detector corresponding to the wedge, and k is the number of fringe levels corresponding to the first-stage wedge.

[0227] For a first-stage wedge with an inclination angle of 0.0001 radians and a height of 350 microns, and a linear array detector with a pixel size of 3.5 microns and 16,384 pixels, the relative uncertainty of wavelength measurement that can be achieved by the first-stage wedge is E-6.

[0228] In some embodiments, the stripes may be selected as light stripes or dark stripes, or light stripes and dark stripes may be recorded simultaneously; for the sake of simplicity, this application does not elaborate, and those skilled in the art may deduce it by themselves according to the relevant contents of this application;

[0229] In some embodiments, equations (13) and (16) output λ 测0 and λ 测1 Before calculating the results, you can take the average value to make full use of the measurement data and reduce errors.

[0230] Another embodiment of a laser wavelength measurement method of the present application will explain in detail the wavelength measurement steps in the case of collaborative measurement involving multiple wedges. In response to the high requirements for wavelength measurement accuracy, the wavelength measurement optical path needs to include multiple wedges and corresponding multiple linear array detectors, and the premise of measurement is still to complete the wedge calibration. Taking a wavelength measurement device including three wedges as an example, the specific steps are as follows:

[0231] Step 1: Input the laser with the wavelength λ to be measured, and each wedge tip and its corresponding detector will obtain the corresponding interference fringe data; record the interference fringe position x obtained by the first-level wedge tip and its corresponding linear array detector 1 k , x k+1 , ...; and the corresponding wedge height D is obtained from the calibration curve of the first wedge k , D k+1 , ...; record the interference fringe position x' obtained by the secondary wedge tip and its corresponding linear array detector 2 m , x' m+1 , ...; and obtain the corresponding wedge height D' from the calibration curve of the secondary wedge m , D' m+1 , ...; record the interference fringe position x obtained by the three-level wedge tip and its corresponding linear array detector 3" n , x” n+1 , ...; and the corresponding wedge height D" is obtained from the calibration curve of the three-level wedge n , D” n+1 ,……;

[0232] Step 2: Use the data obtained by the first-stage wedge and its corresponding linear array detector 1 to obtain λ 测1The details of this step are as shown in the above embodiment: firstly, a rough value λ of the wavelength to be measured is obtained from the interference fringes. 测0 ; Use wavelength to roughly measure the value λ 测0 Determine the order of interference fringes corresponding to the first-order wedge tip; then use the wedge tip height and fringing order corresponding to the fringes to obtain the wavelength measurement result λ corresponding to the first-order wedge tip 测1 ;

[0233] Step 3: The wavelength measurement result λ corresponding to the first wedge 测1 Combined with the interference fringe data corresponding to the secondary wedge tip, the order of the interference fringe corresponding to the secondary wedge tip is determined as follows:

[0234] (18)m=[2D' m / λ 测1 ],m+1=[2D' m+1 / λ 测1 ], ... (dark pattern);

[0235] m=[2D' m / λ 测1 +1 / 2],m+1=[2D' m+1 / λ 测1 +1 / 2], ... (bright lines);

[0236] [] indicates integer;

[0237] Then the wavelength measurement result corresponding to the secondary wedge is:

[0238] (19)λ 测2 =2D' m / m=2D' m+1 / (m+1)=……(dark pattern);

[0239] λ 测2 =2D' m / (m-1 / 2)=2D' m+1 / (m+1-1 / 2)=……(bright lines);

[0240] (20)δλ 测2 / λ 测2 ≈μ 2 ×2sinθ 2 / (λ 测2 ×m);

[0241] Among them, θ 2 and μ 2 are respectively the top angle of the second-stage wedge and the pixel size of the linear array detector 2 corresponding to the wedge, and m is the number of fringe levels corresponding to the second-stage wedge.

[0242] Step 4: Measure the wavelength corresponding to the secondary wedge 测2Combined with the interference fringe data corresponding to the three-level wedge tip, the order of the interference fringe corresponding to the three-level wedge tip is determined as follows:

[0243] (21)n=[2D” n / λ 测2 ],n+1=[2D” n+1 / λ 测2 ], ... (dark pattern);

[0244] n=[2D” n / λ 测2 +1 / 2], n+1=[2D” n+1 / λ 测2 +1 / 2], ... (bright lines);

[0245] [] indicates integer;

[0246] The wavelength measurement result corresponding to the third-level wedge tip is:

[0247] (22)λ 测3 =2D” n / n=2D” n+1 / (n+1)=……(dark pattern);

[0248] λ 测3 =2D” n / (n-1 / 2)=2D” n+1 / (n+1-1 / 2)=……(bright lines);

[0249] (23)δλ 测3 / λ 测3 ≈μ 3 ×2sinθ 3 / (λ 测3 ×n);

[0250] Among them, θ 3 and μ 3 are respectively the top angle of the third-level wedge and the pixel size of the linear array detector 3 corresponding to the wedge, and n is the number of fringe levels corresponding to the third-level wedge.

[0251] In some embodiments, the stripes may be selected as light stripes or dark stripes, or light stripes and dark stripes may be recorded simultaneously; for the sake of simplicity, this application does not elaborate, and those skilled in the art may deduce it by themselves according to the relevant contents of this application;

[0252] In some embodiments, equations (19) and (22) output λ 测2 and λ 测3 Before calculating the results, you can take the average value to make full use of the measurement data and reduce errors.

[0253] For a secondary wedge with an inclination angle of 0.0001 radians and a height of 35 mm, and the specification of the linear array detector 2 is 3.5 microns × 16384, the relative uncertainty of wavelength measurement that can be achieved by combining the secondary wedge with the aforementioned primary wedge is E-8; for a tertiary wedge with an inclination angle of 0.0001 radians and a height of 35 cm, and the specification of the linear array detector 3 is 3.5 microns × 16384, the relative uncertainty of wavelength measurement that can be achieved by combining the tertiary wedge with the aforementioned primary and secondary wedges is E-9; thus, for a single-frequency laser with a wavelength of 780 nm to be measured, the achievable measurement accuracy is 0.0008 pm.

[0254] In some embodiments, the wavelength measurement device includes more than three wedge tips and corresponding detectors. In this case, the measurement result λ of the third wedge tip needs to be continued. 测3 To determine the order of the fourth-order wedge fringes, and according to the above steps and interference conditions, the wavelength measurement result λ of the fourth-order wedge is obtained. 测4 For more wedge tips and detectors, the above steps can be performed step by step to finally obtain the wavelength measurement value.

[0255] Based on the same concept, the present application also discloses a laser wavelength measurement system, including a memory, a processor and a computer program stored in the memory, wherein the processor executes the software program to implement the steps of the laser wavelength measurement method in any of the above embodiments.

[0256] Specifically, an embodiment of a laser wavelength measurement system includes: a data acquisition module, a wedge calibration module, a storage module, a wavelength measurement module, a display module, etc.

[0257] The data acquisition module is used to collect the interference fringe data of each linear array detector and transmit it to the computer for data archiving and data processing;

[0258] The wedge tip calibration module is used to calibrate each wedge tip using a laser of known wavelength to obtain calibration data of each wedge tip;

[0259] The storage module is used to sequentially store the calibration data of each level of the wedge tip for future use; and is also used to store the historical data of wavelength measurement for monitoring and analyzing the changes in the measured wavelength over a period of time;

[0260] The wavelength measurement module is used to analyze the interference fringes measured under the incident condition of the wavelength to be measured, call the archived wedge calibration data, obtain the wavelength value to be measured, and output the uncertainty of the wavelength measurement;

[0261] The display module is used for human-computer interaction and wavelength measurement result display. There are a series of scenarios that require human-computer interaction during the calibration and measurement process; when the measurement is completed, the measurement results also need to be fed back and displayed.

[0262] In some embodiments, the function of the display module is provided by the wavelength measurement software interface, the computer communicates with the linear array detector in real time, and all data collection, processing, feedback, display, etc. are completed on the computer;

[0263] In some embodiments, hardware and software related to data acquisition and processing are integrated in a mobile display module, and related data acquisition, processing, feedback, display, etc. are all completed on this mobile display module; this mobile display module is equivalent to a dedicated display screen and a dedicated processor.

[0264] The laser wavelength measurement optical path, measurement method and system of the present application have the same technical concept, and the technical details of the three embodiments are applicable to each other. In order to reduce repetition, they will not be repeated here.

[0265] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, only the division of the above-mentioned program modules is used as an example for illustration. In actual applications, the above-mentioned functions can be assigned to different program modules as needed, that is, the internal structure of the device can be divided into different program units or modules to complete all or part of the functions described above. The program modules in the embodiment can be integrated into a processing unit, or each unit can exist physically separately, or two or more units can be integrated into a processing unit, and the above-mentioned integrated unit can be implemented in the form of hardware or in the form of software program units. In addition, the specific names of the program modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application.

[0266] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0267] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A laser wavelength measurement optical path, characterized in that: include: Parallel beam shaper, composed of optical fiber and parabolic reflector, used to convert laser light into parallel light; 45° beam splitter, located on the outgoing optical path of the parallel light beam, used for beam splitting; A wedge tip, located behind the 45° beam splitter, is used to receive the parallel light and form interference fringes, the upper surface of the wedge tip is coated with a partially transmissive and partially reflective film, and the bottom surface is coated with a high-reflective film; The cylindrical lens is located between the linear array detector and the 45° beam splitter and is used to focus light along the stripe direction; The interference fringes pass through the 45° beam splitter and cylindrical lens in sequence and converge to the linear array detector for detection; The wedge tips include: a first-stage wedge tip, a second-stage wedge tip, and a third-stage wedge tip; wavelength measurement is performed by analyzing interference fringe data generated by the wedge tips; the wedge tips are fixed on a low-expansion material substrate, and the substrate temperature is controllable to suppress the influence of thermal expansion on wavelength measurement.

2. A laser wavelength measurement optical path as claimed in claim 1, characterized in that: The first level of splitting needs to meet the following requirements: βk≤N; or βμ×λ / Δλ≤N×μ; The second level splitting and the third level splitting should meet the following conditions: β×2D 一级 / λ<N; │2D 二级 / λ-2D 二级 / (λ±δλ 一级 )│<1; │2D 三级 / λ-2D 三级 / (λ±δλ 二级 )│<1; The stripe spacing generated by the wedge tips at each level in the corresponding optical path satisfies: L = λ / (2sinθ) ≤ N×μ; Where k is the number of fringes; β is the detector resolution factor; μ is the detector pixel size; βμ is the detector resolution limit, and the β value range is 0<β≤1. β=1 means that the detector resolution limit is one pixel. System optimization can improve the resolution limit, and the corresponding β is less than 1; N is the number of detector pixels; Δλ is the wavelength change; λ is the wavelength; δλ 一级 : First-order wedge measurement uncertainty, δλ 二级 : Second-order wedge measurement uncertainty, D 一级 : Height of the first level wedge; D 二级 : Height of the second level wedge tip; D 三级 : height of the third-level wedge tip; θ: wedge tip inclination angle, sinθ≈tanθ≈θ; L: fringe spacing.

3. A laser wavelength measurement optical path as claimed in claims 1 and 2, characterized in that: The wavelength measurement uncertainty corresponding to each level of the wedge tip is evaluated by the following formula: δλ=βμ×2sinθ / k; Where, δλ: wavelength measurement uncertainty; k: fringe order.

4. A laser wavelength measurement method, characterized in that: Based on the wavelength measurement optical path described in claims 1-3, the following steps are included: Using a laser of known wavelength to calibrate the wedge tip, respectively obtain data of the height of the wedge tip at each level changing with position, and archive them for future use; The laser to be measured is incident, and interference fringes can be obtained respectively by the wedge tips at each level and their corresponding detectors; the calibration data is called, and the interference fringes of the laser to be measured are processed to obtain the wavelength of the laser to be measured; The wedge tip is fixed on a low expansion material substrate, the substrate is temperature controlled, environmental parameters are monitored in real time during calibration and measurement, and calibration and measurement data are corrected to improve the accuracy of wavelength measurement.

5. A laser wavelength measurement method as claimed in claim 4, characterized in that: The method of using lasers of known wavelength to calibrate the wedge tips of each level comprises the following steps: The coordinate axis associated with the position of the wedge tip is established on the linear array detector, and the interference fringes are measured under the laser with wavelength λ0. The position x where a fringe is located is selected. k As the position to be calibrated, assume that the corresponding fringe order is k; change the laser wavelength to λ1, the fringe will move, when x k When the position of a new fringe coincides with the position of a new fringe, the order of the new fringe is recorded as m; although k and m are unknown, the change in the order of the fringe is certain, that is, km is certain; from the interference condition, the position x can be obtained k Corresponding wedge height D k ,as follows: Dark pattern: 2D k / λ0=k; Bright pattern: 2D k / λ0=k-1 / 2; Dark pattern: 2D k / λ1=m; Bright pattern: 2D k / λ1=m-1 / 2; Δk = km; λ0, λ1 and Δk are all definite quantities, from which the position x can be determined k Corresponding wedge height D k ; By changing the laser wavelength and selecting a new position to repeat the above steps, data of different positions and their corresponding wedge tip heights can be obtained. These data can be fitted to obtain a relationship curve between position and wedge tip height.

6. A laser wavelength measurement method as claimed in claim 5, characterized in that: When the wavelength tuning of the laser used for calibration is limited and insufficient to make the new and old interference fringes overlap, or the determination of fringe overlap is limited, the second method can be used to calibrate the wedge tip. The steps are as follows: The coordinate axis associated with the position of the wedge tip is established on the linear array detector, and the interference fringes are measured under the laser with wavelength λ0, and the position x of each level of fringes is recorded. k , x k+1 , ...; Assume that the corresponding wedge height at the stripe position is D k , D k+1 , ...; Change the wavelength to λ1 and record the new position x′ of each level of fringes k , x′ k+1 , ...; Assume that the corresponding wedge height is D' k , D′ k+1 ,……; sinθ=λ0 / 2(x k+1 -x k )=λ0 / 2(x k+2 -x k+1 )=……=λ1 / 2(x′ k+1 -x′ k )=λ1 / 2(x′ k+2 -x′ k+1 ) =……=(D′ k -D k ) / (x′ k -x k )=(D′ k+1 -D k+1 ) / (x′ k+1 -x k+1 )=……; By dark fringe condition: 2D k / λ0=2D′ k / λ1=k; get: k=[2(x′ k -x k )sinθ / (λ1-λ0)]; Or by bright grain condition: 2D k / λ0=2D′ k / λ1=k-1 / 2; get: k=[2(x′ k -x k )sinθ / (λ1-λ0)+1 / 2]; Among them, sinθ is an intermediate quantity that does not need to be actually solved; […] indicates rounding (the same below); After determining the fringe order k, the wedge tip height corresponding to each fringe position can be obtained as follows: Dark fringe: D k = kλ0 / 2, D k+1 = (k + 1)λ0 / 2, ……, D′ k = kλ1 / 2, D′ k+1 = (k + 1)λ1 / 2, ……; Bright fringe: D k =(k - 1 / 2)λ0 / 2, D k+1 =(k + 1 - 1 / 2)λ0 / 2, ……, D′ k =(k - 1 / 2)λ1 / 2, D′ k+1 =(k + 1 - 1 / 2)λ1 / 2, ……; By repeating the above steps under different wavelength conditions, the wedge tip height data corresponding to different position coordinates can be obtained. These data are fitted to obtain a relationship curve between the position coordinates and the corresponding wedge tip height.

7. A laser wavelength measurement method as claimed in claim 6, characterized in that: Also includes: The wavelength value to be measured is obtained by the first-stage wedge, which specifically includes the following steps: When the laser of the wavelength to be measured is incident, the first-stage wedge will measure the interference fringes, and the fringes position x k , x k+1 , ...; and the corresponding wedge height is obtained from the coordinate curve of the first wedge as D k , D k+1 ,……; λ 测0 =2(D k+1 -D k )=2(D k+2 -D k+1 ), λ 测0 is the rough value of the measured wavelength; Dark pattern: k = [2D k / λ 测0 ],k+1=[2D k+1 / λ 测0 ], …; Bright fringe: k = [2D k / λ 测0 +1 / 2],k+1=[2D k+1 / λ 测0 +1 / 2], ...; Dark pattern: λ 测1 =2D k / k=2D k+1 / (k+1)=……; Bright grain: λ 测1 =2D k / (k-1 / 2)=2D k+1 / (k+1-1 / 2)=……; Output λ from the above formula 测0 and λ 测1 Before calculating the result, we can take the average value to reduce the error; 测0 The relative uncertainty limit of is 1 / N, where N is the number of pixels in the detector; 测1 The relative uncertainty limit is μ1×2sinθ1 / k, where θ1 and μ1 are the apex angle of the first-stage wedge and the detector pixel size corresponding to the wedge, respectively.

8. A laser wavelength measurement method as claimed in claim 7, characterized in that: Also includes: The wavelength value to be measured is obtained by the second-stage wedge, which specifically includes the following steps: When the laser of the wavelength to be measured is incident, interference fringes are measured by the first and second level wedges, wherein the measurement data obtained by the first level wedge is processed according to claim 7 to obtain the wavelength measurement value λ 测1 ; The interference fringe position of the second wedge tip is x K , x K+1 , ...; and the corresponding wedge height is obtained from the calibration curve of the second wedge as D K , D K+1 ,……; Dark pattern: K = [2D K / λ 测1 ],K+1=[2D K+1 / λ 测1 ], …; Bright grain: K = [2D K / λ 测1 +1 / 2],K+1=[2D K+1 / λ 测1 +1 / 2], ...; Dark pattern: λ 测2 =2D K / K=2D K+1 / (K+1)=……; Bright grain: λ 测2 =2D K / (K-1 / 2)=2D K+1 / (K+1-1 / 2)=……; Output λ from the above formula 测2 Before calculating the result, we can take the average value to reduce the error; 测2 The relative uncertainty limit is μ2×2sinθ2 / K, where θ2 and μ2 are the second-stage wedge apex angle and the corresponding detector pixel size, respectively.

9. A laser wavelength measurement method as claimed in claim 8, characterized in that: Also includes: The wavelength value to be measured is obtained by the third-level wedge, which specifically includes the following steps: The laser to be measured is incident, and interference fringes are measured by the first, second and third level wedges. The fringes of the first and second level wedges are processed according to claims 7-8 to obtain the wavelength measurement value λ 测2 ; The interference fringe position of the third wedge is x M , x M+1 , ...; and the corresponding wedge height is obtained from the calibration curve of the third wedge as D M , D M+1 ,……; Dark pattern: M = [2D M / λ 测2 ],M+1=[2D M+1 / λ 测2 ], …; Bright lines: M = [2D M / λ 测2 +1 / 2],M+1=[2D M+1 / λ 测2 +1 / 2], ...; Dark pattern: λ 测3 =2D M / M=2D M+1 / (M+1)=……; Bright grain: λ 测3 =2D M / (M-1 / 2)=2D M+1 / (M+1-1 / 2)=……; Output λ from the above formula 测3 Before calculating the result, we can take the average value to reduce the error; 测3 The relative uncertainty limit is μ3×2sinθ3 / K, where θ3 and μ3 are the third-order wedge apex angle and the corresponding detector pixel size, respectively.

10. A laser wavelength measurement system, comprising a memory, a processor and a computer program stored in the memory, characterized in that: The processor executes the computer program to implement the steps of the laser wavelength measurement method according to any one of claims 4 to 9.

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