Divergence angle error correction model of narrow-band optical filter and application of divergence angle error correction model

Abstract

The invention provides a divergence angle error correction model for a narrow-band filter and application thereof, and the divergence angle error correction model for the narrow-band filter is constructed by analyzing the influence of the angle of a divergence angle on the central wavelength, the peak transmittance and the full width at half maximum. An actual test spectrum curve is calculated by using the divergence angle error correction model, and compared with a theoretical design curve, the design and preparation work of the narrow-band optical filter can be better guided. According to the technical scheme, the technical problem that in the prior art, spectrum testing of the narrow-band optical filter cannot meet the use requirement can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of spectrum analysis, and in particular relates to a divergence angle error correction model of a narrow-band filter and an application thereof. 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 spectral transmittance curve of the narrow-band filter tested by a commonly used spectrophotometer shows that the test curve drifts toward the short-wave direction, the transmittance decreases, and the half-width becomes wider compared to the design curve.

[0005] The key to testing narrowband filters lies in the center wavelength, bandwidth, steepness resolution, and cutoff depth test accuracy. When testing narrowband filters, the existence of the divergence angle will cause non-vertical incidence of light, thereby introducing wavelength angle drift errors, which are manifested as the center 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 thin 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 establish a divergence angle error correction model for narrowband filters by analyzing the influence of angle on central wavelength, peak transmittance and half-width, as well as analyzing the cone angle effect of the beam incident angle. 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 divergence angle error correction model for a narrowband filter is provided. The divergence angle error correction model for the narrowband filter is based on Corrected central wavelength, according to Corrected peak transmittance, according to Corrected FWHM.

[0009] According to another aspect of the present invention, an application of a divergence angle error correction model for a narrowband filter is provided. The narrowband filter uses the divergence angle error correction model as described above to correct the divergence angle error. The narrowband filter after the divergence angle error correction can better meet actual measurement requirements.

[0010] By applying the technical solution of the present invention, a divergence angle error correction model for a narrow-band filter and its application are provided. Aiming at the problem that the spectral data differs greatly from the theoretical design, the influence of the angle on the central wavelength, peak transmittance and half-width is analyzed, and the cone angle effect of the incident angle of the light beam is analyzed. A divergence angle error correction model for a narrow-band filter is constructed, which can correct the central wavelength, peak transmittance and half-width according to the divergence angle. The actual test spectral curve calculated by the divergence angle error correction model of the narrow-band filter of the present invention is more realistic than the theoretical design curve, and the measurement error is smaller. Compared with the prior art, the technical solution of the present invention can solve the technical problem that the spectral test of the narrow-band filter in the prior art cannot meet the use requirements. DETAILED DESCRIPTION

[0011] 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 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.

[0012] 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.

[0013] 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. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method 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 can have different values.

[0014] According to a specific embodiment of the present invention, a divergence angle error correction model of a narrow-band filter is provided. The divergence angle error correction model of the narrow-band filter is based on Corrected central wavelength, according to Corrected peak transmittance, according to Corrected half-width, where λ is the center wavelength of the filter, λ0 is the center wavelength of the filter when the incident angle is 0°, θ0 is the oblique incidence angle, and n is the equivalent refractive index of the film system spacer layer; T is the peak transmittance at oblique incidence, N0 and N1 are the optical admittances of the two media respectively, θ1 is the beam exit angle, and t is the transmittance of the spacer layer; 2Δλ is the passband width of the narrowband filter, m is the interference order, R1 and R2 are the reflectivity of the reflective film system on both sides of the spacer layer, T 12 is the transmittance of the reflective layer.

[0015] By applying this configuration, a divergence angle error correction model for a narrowband filter is provided. By analyzing the influence of the divergence angle on the central wavelength, peak transmittance and half-height width, a divergence angle error correction model for a narrowband filter is constructed. The actual test spectrum curve is calculated using the divergence angle error correction model of the present invention and compared with the theoretical design curve, which can better guide the design and preparation of narrowband filters.

[0016] In common spectrophotometer tests, the spectral data differs greatly from the theoretical design, and the influence of the divergence angle on the central wavelength, peak transmittance and half-height width is analyzed.

[0017] (1) Effect of angle on central wavelength

[0018] When the incident light is at an angle of θ0, the central wavelength of the filter is n is the equivalent refractive index of the spacer layer of the film system. When the incident light is obliquely incident, the optical admittance of different polarized light will change. According to the optical admittance of the film, as the incident angle increases, the central wavelengths of the s component and the p component will gradually separate and produce obvious differences. The central wavelength separation of the s component and the p component is Δλ. s,p According to formula (1), we can obtain:

[0019]

[0020] Among them, Δλ s,p is the center wavelength separation of the s component and the p component, λ0 is the center wavelength of the filter when the incident angle is 0°, θ0 is the oblique incident angle, and n is the equivalent refractive index of the film spacer layer.

[0021] Taking the UV3600 spectrophotometer as an example, the divergence half angle is 4.76°, and the filter center wavelength λ0 is 532nm when the incident angle θ0 is 4.76°.

[0022]

[0023] The equivalent refractive index n of the film system spacer layer is 1.48.

[0024] (2) Effect of angle on peak transmittance

[0025] Transmittance is the ratio of the vertical component of the transmitted light intensity to the vertical component of the incident light intensity. When the incidence is oblique, the transmittance is

[0026]

[0027] Wherein, T is the peak transmittance at oblique incidence, N0 and N1 are the optical admittances of the two media, θ1 is the light beam exit angle, and t is the transmittance of the spacer layer.

[0028] According to formula (3), when the incidence is vertical, the transmittance T 0° for

[0029]

[0030] According to formula (3) and formula (4), it can be seen that as the light cone angle increases, the spectral transmittance at the design wavelength decreases.

[0031] Film structure Sub|(LH) 7 12L(HL) 7 | Air as an example, when the light beam is incident vertically, the transmittance T 0° for

[0032]

[0033] Among them, N1 is 1.48 and N0 is 1.

[0034] When the divergence half angle is 4.76°,

[0035]

[0036] Where N1 is 1.48, N0 is 1, θ0 is 4.76°, θ1 is 3.21°, and the transmittance T is calculated. 4.76° =64.43%.

[0037] It can be seen from formula (5) to formula (8) that when using the UV3600 spectrophotometer for testing, the spectral transmittance of the narrowband filter decreases as the divergence angle increases.

[0038] (3) Effect of angle on half-width

[0039] The half-wave transmittance of a narrowband filter is

[0040]

[0041] Wherein, T0 is the vertical transmittance and Δθ is the tilt change angle.

[0042] When the two reflective films of the all-dielectric filter are symmetrical,

[0043]

[0044] Among them, R 12 is the reflectivity, T 12 is the transmittance of the reflective layer.

[0045] The passband width 2Δλ of a narrowband filter is

[0046]

[0047] and

[0048] therefore,

[0049] Where x is the number of high refractive index material layers in the reflective layer, m is the interference order, the reflectivity of the upper and lower reflective layers of R1 and R2, and n is g is the substrate refractive index, n L is the refractive index of the low refractive index layer, n H is the refractive index of the high refractive index layer. As the light cone angle increases, the half-height width of the narrowband filter will widen.

[0050] Film structure Sub|(LH) 7 12L(HL) 7 |Air as an example, at a wavelength of 532nm, the refractive index of Ta2O5 is 2.17, the refractive index of SiO2 is 1.48, and the refractive index of the substrate is 1.46. The transmittance of the reflective layer is T 12 =1.85×10 -2 Substituting into equation (11), we obtain the passband width of the film system: 2Δλ = 0.52 nm.

[0051] When the divergence half angle is 4.76°, the passband width of the narrowband filter is

[0052]

[0053] Among them, N1 is 1.48, N0 is 1, θ0 is 4.76°, and θ1 is 3.21°.

[0054] According to formula (11) and formula (14), it can be seen that when using the UV3600 spectrophotometer for testing, the half-width of the narrow-band filter will be widened.

[0055] From the above analysis, we can know that the divergence angle error correction model of the narrowband filter is based on Corrected central wavelength, according to Corrected peak transmittance, according to Corrected FWHM.

[0056] According to another aspect of the present invention, an application of a divergence angle error correction model for a narrowband filter is provided. The narrowband filter uses the above-mentioned divergence angle error correction model for the narrowband filter to correct the divergence angle error.

[0057] 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.

[0058] 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 divergence angle error correction model for a narrowband filter, characterized in that: The divergence angle error correction model of the narrowband filter is based on Corrected central wavelength, according to Corrected peak transmittance, according to Corrected half-width, where λ is the center wavelength of the filter, λ0 is the center wavelength of the filter when the incident angle is 0°, θ0 is the oblique incidence angle, and n is the equivalent refractive index of the film system spacer layer; T is the peak transmittance at oblique incidence, N0 and N1 are the optical admittances of the two media respectively, θ1 is the beam exit angle, and t is the transmittance of the spacer layer; 2Δλ is the passband width of the narrowband filter, m is the interference order, R1 and R2 are the reflectivity of the reflective film system on both sides of the spacer layer, T 12 is the transmittance of the reflective layer.

2. Application of a divergence angle error correction model for a narrowband filter, characterized in that: The narrowband filter adopts the divergence angle error correction model of the narrowband filter as claimed in claim 1 to correct the divergence angle error.

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