Narrowband filter divergence angle error analysis model and system
By establishing a narrow-band filter divergence angle error analysis model, the impact of divergence angle on spectral transmittance is analyzed, and the problem of insufficient spectral testing accuracy in the existing technology is solved, and more accurate film design and preparation is achieved.
Patent Information
- Application Number
- CN202411679230.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-22
- Publication Date
- 2025-03-11
AI Technical Summary
The spectral test of narrowband filters in the prior art cannot accurately analyze the impact of divergence angle on spectral transmittance, resulting in errors in measurement accuracy and cannot effectively guide film design and preparation.
A narrowband filter divergence angle error analysis model was established. This model analyzed the spectral transmittance changes at different divergence angles and incident angles by constructing the spectral characteristics within the beam cone angle and the transmittance equation of the thin film sample.
Through this model, the changes in spectral transmittance can be accurately calculated, the film design and preparation process can be optimized, and the accuracy and reliability of spectral testing can be improved.
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Figure CN119598063A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of spectrum analysis, and in particular relates to a narrow-band filter divergence angle error analysis model and system. Background Art
[0002] The application scenarios of LiDAR detection systems require stable performance of bandpass filters. The current spectral drift problem of bandpass filters will affect the accuracy and reliability of detection. In laser detection and imaging systems, bandpass filters play a key role and play a vital role in the development of optoelectronic systems and laser technology. Bandpass filters have become a bottleneck problem that directly affects the improvement of detection distance and imaging resolution.
[0003] Using filters is an effective way to improve the signal-to-noise ratio. Optical filters can change the spectral intensity distribution of incident light according to specified needs. The noise of the return light, which originally had a large noise, is weakened after being filtered by the filter. In the process of suppressing noise, if the transmission bandwidth of the filter is too wide, much larger than the width of the signal light, then the light entering the detector after filtering may contain a large amount of noise, which is not conducive to the imaging of the detector. With the continuous improvement of the requirements for the detection capability of return light, it is objectively necessary to have a narrower transmission bandwidth and a higher peak transmittance of the filter.
[0004] The commonly used spectrophotometer tests the spectral transmittance curve of the narrow-band filter. The test curve shows a decrease in transmittance compared to the design curve.
[0005] When testing narrowband filters, the existence of divergence angle will cause non-vertical incidence of light, thereby introducing wavelength angle drift error, which is manifested as the central wavelength moving toward the short-wave direction, the passband peak transmittance decreases, the bandwidth widens, and the steepness of the transition zone tends to decrease. This results in a certain error in measurement accuracy when using a common spectrophotometer for testing, and the design of optical films is based on ideal parallel light. The test results cannot guide the accuracy of the preparation process and design.
[0006] Therefore, it is particularly important to analyze the influence of angle on central wavelength, peak transmittance and half-width, as well as the cone angle effect of the beam incident angle, and to establish a divergence angle error analysis model for narrowband filters. Summary of the invention
[0007] The present invention aims to solve at least one of the technical problems existing in the prior art.
[0008] According to one aspect of the present invention, a narrowband filter divergence angle error analysis model is provided. The narrowband filter divergence angle error analysis model is based on
[0009] Construct, where F(λ) represents the spectral characteristics within the beam cone angle, θ is the incident angle, λ is the central wavelength of the beam, and θ max is the beam cone angle, θ 0 is the incident angle of the light beam, f(λ,θ) is the transmittance of the thin film sample; B and C both represent the eigenvalues of the characteristic matrix, n j0 is the direct optical admittance of the jth film, η j is the tilted optical admittance of the jth film, δ j is the phase thickness of the j-th film, i is an imaginary unit, η G is the optical admittance of the substrate, j = 1, 2, ... k, k is the total number of film layers; d j is the thickness of the jth film layer, θ j is the refraction angle of the jth film; Y is the combined admittance, R is the reflectivity, T is the transmittance, T s,p is the transmittance of the combination of s component and p component, T s is the transmittance of the s component, T p is the transmittance of the p component, η 0 Represents the optical admittance of the incident medium.
[0010] According to another aspect of the present invention, a narrow-band filter divergence angle error analysis system is provided, which includes: a sample stage, a collimated optical path, a first and a second polarizer, an attenuation plate, an aperture and a spectrometer; the sample stage is used to place a narrow-band filter sample to be tested; the light signal output by the laser is irradiated onto the sample after passing through the collimated optical path and the first polarizer, and the laser after passing through the sample enters the spectrometer after passing through the second polarizer, the attenuation plate and the aperture; the spectrometer performs photoelectric conversion on the light signal output by the optical path system to obtain spectral data of the narrow-band filter sample; and the narrow-band filter divergence angle error analysis model as described above is used to obtain changes in spectral transmittance based on the spectral data.
[0011] By applying the technical solution of the present invention, a narrow-band filter divergence angle error analysis model and system are provided. In view of the large difference between spectral data and theoretical design, the cone angle effect of the light beam incident angle is analyzed, and a formula for constructing a narrow-band filter divergence angle error analysis model is provided. The change in spectral transmittance can be calculated according to different divergence angles and different incident angles. This model is helpful for theoretically analyzing the influence of divergence angle on spectral transmittance, so as to optimize the design and preparation process of the film. Compared with the prior art, the technical solution of the present invention can solve the technical problem that the spectral test of narrow-band filters in the prior art cannot meet the use requirements. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0013] Figure 1 A schematic diagram of a narrow-band filter divergence angle error analysis system provided according to a specific embodiment of the present invention is shown;
[0014] Figure 2 A schematic diagram showing the test results of high-precision spectral characteristics at different angles is shown;
[0015] Figure 3 A schematic diagram showing the incident light beam onto the sample. DETAILED DESCRIPTION
[0016] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0017] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.
[0018] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values of the parts and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values.
[0019] According to a specific embodiment of the present invention, a narrow-band filter divergence angle error analysis model is provided. The narrow-band filter divergence angle error analysis model is based on
[0020] Construct, where F(λ) represents the spectral characteristics within the beam cone angle, θ is the incident angle, λ is the central wavelength of the beam, and θ max is the beam cone angle, θ 0 is the incident angle of the light beam, f(λ,θ) is the transmittance of the thin film sample; B and C both represent the eigenvalues of the characteristic matrix, n j0 is the direct optical admittance of the jth film, η j is the tilted optical admittance of the jth film, δ j is the phase thickness of the j-th film, i is an imaginary unit, η G is the optical admittance of the substrate, j = 1, 2, ... k, k is the total number of film layers; d j is the thickness of the jth film layer, θ j is the refraction angle of the jth film; Y is the combined admittance, R is the reflectivity, T is the transmittance, T s,p is the transmittance of the combination of s component and p component, T s is the transmittance of the s component, T p is the transmittance of the p component, η 0 Represents the optical admittance of the incident medium.
[0021] By applying this configuration, a narrow-band filter divergence angle error analysis model is provided. In view of the large difference between the spectral data and the theoretical design, the cone angle effect of the beam incident angle is analyzed, and the construction formula of the narrow-band filter divergence angle error analysis model is given. The change of spectral transmittance can be calculated according to different divergence angles and different incident angles. This model is conducive to theoretically analyzing the influence of divergence angle on spectral transmittance, so as to optimize the design and preparation process of the film.
[0022] In common spectrophotometer tests, the spectral data differs greatly from the theoretical design. The present invention analyzes the influence of the divergence angle on the peak transmittance by taking into account the small divergence angle (light cone angle) of the laser beam to build a narrow-band filter divergence angle error analysis model.
[0023] Due to the propagation characteristics of light, the light beam diverges or focuses. When the light beam is projected onto the target surface at a certain cone angle, the maximum cone angle of the projection point comes from the maximum cone angle of the incident light beam, that is, the projection range of the light beam. This effect affects the size of the irradiated area on the target surface and the distribution of light intensity. Figure 3 A schematic diagram of the parameters when a circular beam is incident vertically on the sample surface is given.
[0024] Beam energy at cone angle 2θ max The energy distribution within the cone angle is C(θ), assuming that the beam energy distribution is uniform, that is, C(θ) = 1. Then when the beam enters the sample at an angle θ, the spectral characteristics within the cone angle of the beam can be expressed as
[0025]
[0026] Where F(λ) represents the spectral characteristics within the cone angle of the beam, θ is the incident angle, λ is the central wavelength of the beam, and θ max is the beam cone angle, θ 0 is the incident angle of the light beam, f(λ,θ) is the transmittance or reflectance of the thin film sample. The present invention studies the transmission spectrum, so f(λ,θ)=T(λ,θ), T(λ,θ) represents the transmittance.
[0027] Narrowband filters are made of multiple layers of high and low refractive index materials. The parameters of any optical thin film system include reflection, transmission and phase, which are determined by the combined admittance of the incident interface and the multilayer film interface in the thin film system.
[0028] The characteristic matrix of the multilayer film system of the narrowband filter can be expressed as
[0029]
[0030] It includes all the key parameters of the film, where B and C represent the eigenvalues of the characteristic matrix, η j is the tilted optical admittance of the jth film, δ j is the phase thickness of the j-th film, i is an imaginary unit, η G is the optical admittance of the substrate, j = 1, 2, ... k, k is the total number of film layers.
[0031] The phase thickness δ of the jth film j for
[0032]
[0033] Among them, n j is the tilted optical admittance of the jth film, d j is the thickness of the jth film layer, θ j is the refraction angle of the jth film layer, which can be calculated based on the law of refraction.
[0034] The optical admittance η j is the tilted optical admittance of the j-th film,
[0035]
[0036] n j0 is the direct optical admittance of the jth film; for the p component, η j =n j0 / cosθ j , for the s component,
[0037] η j =n j0 cosθ.
[0038] The combined admittance is
[0039] Y=C / B (5)
[0040]
[0041]
[0042] T=(T s +T p ) / 2 (8)
[0043]
[0044] Among them, Y is the combined admittance, R is the reflectivity, T is the transmittance, and T s,p is the transmittance of the combination of s component and p component, T s is the transmittance of the s component, T p is the transmittance of the p component, η 0 Represents the optical admittance of the incident medium.
[0045] According to the spectral characteristics of the film of formula (1) and the characteristic matrix of the film of formula (2) to formula (9), a divergence angle error analysis model is established. The model can calculate the change of spectral transmittance according to different divergence angles and different incident angles.
[0046] like Figure 1 As shown, according to another aspect of the present invention, a narrow-band filter divergence angle error analysis system is provided, the system comprising: a sample stage, a collimated light path, first and second polarizers, an attenuation plate, an aperture, and a spectrometer;
[0047] Sample stage, used to place the narrowband filter sample to be tested.
[0048] The light signal output by the laser is irradiated onto the sample after passing through the collimated optical path and the first polarizer. The laser after passing through the sample enters the spectrometer after passing through the second polarizer, the attenuation plate and the aperture.
[0049] The spectrometer performs photoelectric conversion on the optical signal output by the optical path system to obtain the spectral data of the narrow-band filter sample; based on the spectral data, the narrow-band filter divergence angle error analysis model as described above is used to obtain the change in spectral transmittance.
[0050] In the present invention, the sample stage can use a sample holder or a sample turntable to place the sample to be tested at a desired angle and position. According to experimental needs, the angle and position of the sample holder or the sample turntable are adjusted to ensure that the laser is normally irradiated on the sample to be tested.
[0051] In the collimated light path, a lens can be used to collimate the laser. The collimating lens can reduce the divergence of the laser beam, making it more parallel and focused.
[0052] The present invention adjusts the laser direction, polarization, power and other parameters through the entire measuring optical path system to control the angle and position of the sample to be measured. Finally, the output grayscale image is processed to obtain a spectrum curve.
[0053] As a specific embodiment of the present invention, Figure 1 As shown, a reflector can be set in the optical path to adjust the direction of the laser.
[0054] In the present invention, an ultra-high resolution spectrometer can be used to perform photoelectric conversion on the optical signal output by the optical path system. The spectrometer can cover the working wavelength range of the white light laser and has sufficient resolution and accuracy.
[0055] As a specific embodiment of the present invention, the spectral data of 5° and 10° were tested using a high-precision system. Figure 2 As the angle increases, the narrowband shifts more toward the short wavelength, accompanied by a decrease in transmittance and a widening of the half-height width.
[0056] The test results are shown in Table 1. At 0°, the central wavelength is 532.00nm, the peak transmittance is 87.23%, and the half-width is 0.79nm; at 5°, the central wavelength is 531.22nm, the peak transmittance is 67.03%, and the half-width is 0.85nm; at 10°, the central wavelength is 528.83nm, the peak transmittance is 52.65%, and the half-width is 1.07nm. This also verifies the influence of the light cone angle on the narrowband filter.
[0057] Table 1 High-precision spectral characteristics test results
[0058]
[0059] Through high-precision spectral testing, parameters such as central wavelength, passband width, peak transmittance, etc. can be obtained more accurately, thus better guiding the design and preparation work. Therefore, high-precision spectral characteristic testing is of great significance in the performance test and evaluation of filters, and can provide strong support for the design and preparation of narrow-band filters.
[0060] Aiming at the problem that the spectral data differs greatly from the theoretical design, the present invention analyzes the cone angle effect of the incident light beam, and establishes an error analysis model of the cone angle of the incident light beam on the light transmittance. Based on the error analysis model, a high-precision spectral characteristic test scheme is provided, which provides strong support for the design and preparation of narrow-band filters.
[0061] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.
[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.
Claims
1. A narrowband filter divergence angle error analysis model, characterized in that: The narrowband filter divergence angle error analysis model is based on Y=C / B, T=(T s +T p ) / 2, Construct, where F(λ) represents the spectral characteristics within the beam cone angle, θ is the incident angle, λ is the central wavelength of the beam, and θ max is the beam cone angle, θ0 is the beam incident angle, f(λ,θ) is the transmittance of the film sample; B and C both represent the eigenvalues of the characteristic matrix, n j0 is the direct optical admittance of the jth film, η j is the tilted optical admittance of the jth film, δ j is the phase thickness of the j-th film, i is an imaginary unit, η G is the optical admittance of the substrate, j = 1, 2, ... k, k is the total number of film layers; d j is the thickness of the jth film layer, θ j is the refraction angle of the jth film; Y is the combined admittance, R is the reflectivity, T is the transmittance, T s,p is the transmittance of the combination of s component and p component, T s is the transmittance of the s component, T p is the transmittance of the p component, and η0 represents the optical admittance of the incident medium.
2. A narrowband filter divergence angle error analysis system, characterized in that: The narrowband filter divergence angle error analysis system comprises: a sample stage, a collimated light path, first and second polarizers, an attenuation plate, an aperture and a spectrometer; Sample stage, used to place the narrowband filter sample to be tested. The light signal output by the laser is irradiated onto the sample after passing through the collimated optical path and the first polarizer. The laser after passing through the sample enters the spectrometer after passing through the second polarizer, the attenuation plate and the aperture. The spectrometer performs photoelectric conversion on the optical signal output by the optical path system to obtain the spectral data of the narrowband filter sample; and obtains the change of spectral transmittance based on the spectral data using the narrowband filter divergence angle error analysis model as claimed in claim 1.
3. The narrowband filter divergence angle error analysis system according to claim 2, characterized in that: A lens is used in the collimated light path to collimate the laser.