CN111552018B - Quasi-rectangular narrow-band filter with wide cut-off and high transmittance - Google Patents
Quasi-rectangular narrow-band filter with wide cut-off and high transmittance Download PDFInfo
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- CN111552018B CN111552018B CN202010471578.0A CN202010471578A CN111552018B CN 111552018 B CN111552018 B CN 111552018B CN 202010471578 A CN202010471578 A CN 202010471578A CN 111552018 B CN111552018 B CN 111552018B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/20—Filters
- G02B5/28—Interference filters
- G02B5/285—Interference filters comprising deposited thin solid films
- G02B5/288—Interference filters comprising deposited thin solid films comprising at least one thin film resonant cavity, e.g. in bandpass filters
Abstract
The invention discloses a quasi-rectangular narrow-band filter with wide cut-off and high transmittance, which comprises a substrate, wherein the upper end surface and the lower end surface of the substrate are respectively provided with a main film system and a back film system, and the substrate adopts colored glass with high absorption coefficient in an ultraviolet visible region. The invention relates to a quasi-rectangular narrow-band filter with wide cut-off and high transmissivity, which uses a cut-off colored filter as a substrate, and one surface of the cut-off colored filter is plated with a four-cavity narrow-band film system, and the other surface of the cut-off colored filter is plated with a short-wave pass film system. By changing the reference wavelength, the narrow-band interference filters of different target wave bands can be obtained, and due to the characteristics of adjustable central wavelength, higher peak transmittance and high rectangularity, the narrow-band interference filters can be used for acquiring signals with extremely high accuracy on any wave band in the range of 400-2000nm, thereby preventing misjudgment of target signals and being beneficial to acquisition of weak signals.
Description
Technical Field
The invention relates to the technical field of quasi-rectangular narrow-band filters, in particular to a quasi-rectangular narrow-band filter with wide cut-off and high transmittance.
Background
In the field of optical thin films, filters with a ratio of half-bandwidth to central wavelength of less than 0.05, called narrow-band filters, have the main function of being selective to light, allowing the passage of light of a certain specific band and the cut-off of the other bands; the method has wide application, and is mainly applied to the fields of infrared imaging, gas detection, laser detection, optical fiber communication systems and the like; with the refinement and development of the photoelectric information system, people gradually improve the requirements on the optical performance of the photoelectric information system, including band-pass transmittance, cut-off depth, rectangularity, steepness and the like; in order to improve the accuracy of the whole optical system, reduce stray light interference and improve band-pass transmittance, people hope for realizing a quasi-rectangular narrow-band filter with wide cut-off and high transmittance;
fabry-perot structure filters are the most commonly used narrow-band interference filters, the basic structure of which is denoted by a (x, m, t):
A(x,m,1)＝Air|(HL)^x(m2H)(LH)^x|Sub，
or A (x, m,0) ═ Air | (LH) ^ x (m2L) (HL) ^ x | Sub,
wherein, (HL) x and (LH) x are reflecting layers of Fabry-Perot type narrow band filters, and are formed by overlapping single-layer films with the optical thickness of 1/4 central wavelength; x represents the number of reflective layers; 2H or 2L is a spacing layer of a Fabry-Perot type narrow-band filter, and the optical thickness of the spacing layer is 1/2 central wavelength; m represents the interference order of the narrow-band filter; t is 1, and represents that the spacing layer is a high-refractive-index film layer; t is 0, and represents that the spacing layer is a low-refractive-index film layer;
when the incident light enters the medium spacing layer, after the two reflecting surfaces of the spacing layer are subjected to multiple reflection and interference, only the light with certain specific wavelength based on the thickness of the spacing layer has high transmittance, while the transmittance of other wave bands is very low, and the band-pass characteristic is shown. The squareness is an important index for judging the performance of the filter, and refers to the ratio of the bandwidth with the transmission rate of 10% of the peak transmission rate of a narrow-band pass band to the bandwidth (half bandwidth) with the transmission rate of 50% of the peak transmission rate, and when the ratio is closer to 1, the more the squareness is, the higher the squareness is;
the Fabry-Perot filter has a passband which is approximately triangular; assuming that the energy of the incident light is uniformly distributed with wavelength, we can see that in any order of filter, half of the transmitted energy is outside the half width of the passband. Moreover, due to the structural limitation of Fabry-Perot, the cut-off band of the filter is usually short, and the requirement that people hope to reduce stray light interference is difficult to meet, so that the designed and prepared quasi-rectangular narrow-band filter capable of achieving both wide cut-off and high transmittance brings good social and economic values, and has a wide application prospect.
The film system structure is formed by connecting more than two single-cavity Fabry-Perot filters in series by using a low-refraction layer with the optical thickness of 1/4 central wavelength:
double cavities: a. the1(x1,m1,t1)LA2(x2,m2,t2)
Three-cavity: a. the1(x1,m1,t1)LA2(x2,m2,t2)LA3(x3,m3,t3)
Four cavities: a. the1(x1,m1,t1)LA2(x2,m2,t2)LA3(x3,m3,t3)LA4(x4,m4,t4)
……
Using Y (A) in the text1，A2)，Y(A1，A2，A3)，Y(A1，A2，A3，A4) Etc.; compared with a single-cavity narrowband filter, the transmission band of the multi-cavity narrowband filter is no longer a peak, the shape of the pass band is closer to a rectangle, the cut-off degree can be rapidly improved, but the ripple of the transmission pass band is increased, the peak transmissivity is reduced, the contradiction among the wide cut-off degree, the high transmission degree and the high squareness is the biggest obstacle of the design of the high-performance narrowband filter, so that the quasi-rectangular narrowband filter with the wide cut-off degree and the high transmission degree is designed, and the problem is solved.
Disclosure of Invention
The invention aims to provide a quasi-rectangular narrow-band filter with wide cut-off and high transmissivity, so as to solve the problems in the prior art.
In order to achieve the purpose, the invention provides the following technical scheme: a quasi-rectangular narrow-band filter with wide cut-off and high transmittance comprises a substrate, wherein a main film system and a back film system are respectively arranged on the upper end face and the lower end face of the substrate.
Preferably, the substrate is colored glass with high absorption coefficient in the ultraviolet visible region.
Preferably, the colored glass may be any of cut-off colored glasses WB260, WB280, WB300, WB360, WB380, JB400, JB420, JB450, JB470, JB490, JB510, CB535, CB550, CB565, CB580, HB600, HB610, HB630, HB640, HB650, HB670, HB680, HB700, HB715, HB780, HB800, HB830, HB850, and the like.
Preferably, the initial film system structure of the main film system is as follows:
Y＝Sub|A1(x,1,0)HA2(y,1,0)HA3(z,1,0)HA4(m,1,0)|Air
A1(x,1,0)＝(LH)^x(2L)(HL)^x
A2(y,1,0)＝(LH)^y(2L)(HL)^y
A3(z,1,0)＝(LH)^z(2L)(HL)^z
A4(m,1,0)＝(LH)^m(2L)(HL)^m
(x, y, z, m is an integer selected from 1 to 5 according to specific requirements).
Preferably, the film system structure of the back film system is short wave pass:
Sub|(0.5LH0.5L)^pq(HL)^n|Air
(p, q, n are selected according to specific requirements).
Preferably, the quasi-rectangular narrow-band filter with wide cut-off and high transmittance is prepared by the following specific steps:
a1, in order to reduce the thickness of the main film system, the substrate material in the invention is colored glass with high absorption coefficient in the ultraviolet and visible light region, different degrees of absorption in different visible light region wave bands are realized by adjusting different colorants and ion concentrations, thereby showing the cut-off of different wave bands, and the substrate material mainly plays the roles of the previous cut-off secondary peak and the reduction of the thickness of the main film system;
a2, in the above film system, Sub represents a substrate; h represents a high index material of optical thickness 1/4 and may be HfO2，Ta2O5，Ti3O5Or TiO2Any one of (a); l represents low refractive index material MgF with the thickness of 1/4 optical thickness2Or SiO2Any one of (a); air represents Air; because the filter has higher requirements on the transmittance and the rectangularity of the center wavelength of a band-pass transmission area, 4 resonant cavity film systems are provided for the front main film system, and the rising and falling gradient of the pass band of the filter and the transmittance of a center wave band are effectively improved; the back film stack adopts 2 post-cut-off film stacks for superposition, and can effectively cut off the secondary peak of the long wave band;
a3, using a cut-off colored filter as a substrate, plating a four-cavity narrow-band film system on one surface of the substrate, and plating a short-wave pass film system on the other surface of the substrate; by changing the reference wavelength, the narrow-band interference filters of different target wave bands can be obtained, and due to the characteristics of adjustable central wavelength, higher peak transmittance and high squareness, the narrow-band interference filters can be used for obtaining signals with extremely high accuracy on any wave band in the range of 400-2000nm, thereby preventing misjudgment of target signals and being beneficial to obtaining weak signals.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention relates to a quasi-rectangular narrow-band filter with wide cut-off and high transmittance. By changing the reference wavelength, the narrow-band interference filters of different target wave bands can be obtained.
2. The center wavelength is adjustable, and the optical fiber has the characteristics of higher peak transmittance and high rectangularity, so that the optical fiber and the optical fiber can be used for acquiring signals with extremely high accuracy at any wave band within the range of 400-2000nm, prevent misjudgment of target signals and facilitate acquisition of weak signals.
Drawings
FIG. 1 is a front view of the main structure of the present invention;
fig. 2 is a schematic view of the wavelength of the present invention.
In the figure: 1. a main film system; 2. a substrate; 3. the back film is provided.
Detailed Description
The embodiment of the application solves the problems in the prior art by providing the quasi-rectangular narrow-band filter with wide cut-off and high transmittance; the following will clearly and completely describe the technical solutions in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Examples
Referring to fig. 1-2, the present embodiment provides a quasi-rectangular narrow-band filter with wide cut-off and high transmittance, which includes a substrate 2, and a main film system 1 and a back film system 3 respectively disposed on the upper end surface and the lower end surface of the substrate 2.
Wherein, the substrate 2 adopts colored glass with high absorption coefficient in the ultraviolet visible region;
the initial film system structure of the main film system 1 is as follows:
Y＝Sub|A1(x,1,0)HA2(y,1,0)HA3(z,1,0)HA4(m,1,0)|Air
A1(x,1,0)＝(LH)^x(2L)(HL)^x
A2(y,1,0)＝(LH)^y(2L)(HL)^y
A3(z,1,0)＝(LH)^z(2L)(HL)^z
A4(m,1,0)＝(LH)^m(2L)(HL)^m
x, y, z and m are selected from an integer from 1 to 5 according to specific requirements;
the film system structure of the back film system 3 is short wave pass:
Sub|(0.5LH0.5L)^pq(HL)^n|Air
p, q and n are selected according to specific requirements;
in this embodiment, the initial film stack of the main film system 1 is a four-cavity fabry-perot symmetric film stack; the back film system 3 is a short-wave-pass film system, in order to reduce the film thickness of the main film system 1, the material of the substrate 2 in the invention is colored glass with high absorption coefficient in an ultraviolet visible region, different degrees of absorption in different visible region wave bands are realized by adjusting different coloring agents and ion concentrations, so that the cut-off of different wave bands is shown, and in the invention, the material of the substrate 2 mainly plays the roles of cutting off a secondary peak before and reducing the thickness of the main film system 1; in the above film system, Sub represents a substrate; h represents a high index material of optical thickness 1/4 and may be HfO2，Ta2O5，Ti3O5Or TiO2Any one of (a); l represents a low refractive index material MgF with a thickness of 1/4 optical thickness2Or SiO2Any one of (a); air represents Air; because the filter has higher requirements on the transmittance and the rectangularity of the center wavelength of a band-pass transmission area, 4 resonant cavity film systems are provided for the main film system 1 on the front surface, and the rising and falling gradient of the pass band of the filter and the transmittance of a center wave band are effectively improved; the back film stack adopts 2 post-cut-off film stacks for superposition, and can effectively cut off the long-wave band secondary peak; the higher the peak transmittance, the more and more accurate the obtained signal; the squareness is an important index for determining the performance of a filter, and refers to the ratio of the bandwidth with a narrow pass band transmittance of 10% of the peak transmittance to the bandwidth half bandwidth with a transmittance of 50% of the peak transmittance,when the ratio is closer to 1, the higher the rectangle degree is; the higher the rectangle degree is, the fewer the spurious signals are, and the signals with higher accuracy can be obtained;
the main film system of the optical filter adopts a plurality of resonant cavity structures, and the resonant cavities in the middle layer have higher level, so that the band-pass rectangularity and the central wave band transmittance of the optical filter are improved; tantalum pentoxide with high transmittance in the visible-near infrared is selected as a film-system high-refractive-index material, and silicon dioxide is selected as a low-refractive-index material; the front film layer and the back film layer are respectively realized by a vacuum coating method, tantalum pentoxide and silicon dioxide materials are alternately evaporated on two surfaces of the substrate;
the colored glass may be any of cut-off colored glasses WB260, WB280, WB300, WB360, WB380, JB400, JB420, JB450, JB470, JB490, JB510, CB535, CB550, CB565, CB580, HB600, HB610, HB630, HB640, HB650, HB670, HB680, HB700, HB715, HB780, HB800, HB830, HB850, and the like, and any of them may be selected depending on the narrowband central band;
the preparation of a narrow-band filter with a center wavelength of 600nm is taken as an example:
base material: colored glass JB510
The initial film system structure of the main film system 1 is as follows:
Sub|(LH)^42L(HL)^4H
(LH)^32L(HL)^3H
(LH)^42L(HL)^4H
(LH)^32L(HL)^3|Air
the film system structure of the back film system 3 is short wave pass:
Sub|(0.5LH0.5L)^151.07(HL)^9|Air
in order to improve the plating precision of the narrow-band filter, the deviation of the central wavelength of the filter is less than 5nm, and a light control system with higher precision is required to monitor the film thickness;
a PerkinElemerSpectrum Fourier transform spectrometer is adopted to test a narrow-band filter with the center wavelength of 603nm, and the final test performance of the filter is as follows:
1. the central wavelength lambda 0 is 603 nm;
2. the half bandwidth Delta lambda is 22 nm;
3. peak transmittance T-97.33%;
4. the squareness degree n is 1.1;
5. the cut-off depth Tc of the sub-peak of 250-1000nm in the designated area is less than 0.5 percent, and the width is 750 nm;
6. the product appearance is as follows: square or round; the plane mirror and the meniscus lens may be used.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (1)
1. A quasi-rectangular narrow-band filter with wide cut-off and high transmission, comprising a substrate (2), characterized in that: the upper end surface and the lower end surface of the substrate (2) are respectively provided with a main film system (1) and a back film system (3);
the substrate (2) adopts colored glass with high absorption coefficient in an ultraviolet visible region;
the colored glass is any one of cut-off colored glasses WB260, WB280, WB300, WB360, WB380, JB400, JB420, JB450, JB470, JB490, JB510, CB535, CB550, CB565, CB580, HB600, HB610, HB630, HB640, HB650, HB670, HB680, HB700, HB715, HB780, HB800, HB830 and HB 850;
the film system structure of the back film system (3) is short wave pass:
Sub|(0.5LH0.5L)^p q(HL)^n|Air
p, q, n are conventional coefficients;
the initial membrane system structure of the main membrane system (1) is as follows:
Y = Sub| A1(x, 1, 0) H A2(y, 1, 0) H A3(z, 1, 0) H A4(m, 1, 0) |Air
A1(x, 1, 0) = (LH)x (2L) (HL)x
A2(y, 1, 0) = (LH)y (2L) (HL) y
A3(z, 1, 0) = (LH)z (2L) (HL)z
A4(m, 1, 0) = (LH)m (2L) (HL)m
x, y, z and m are any integer of 1-5;
sub represents a substrate; h represents high-refractive-index material HfO with the thickness of 1/4 optical thickness2，Ta2O5，Ti3O5Or TiO2Any one of (a); l represents a low refractive index material MgF with a thickness of 1/4 optical thickness2Or SiO2Any one of (a); air stands for Air.
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| JP2002258036A (en) * | 2001-02-28 | 2002-09-11 | Kyocera Corp | Multilayer thin film optical filter |
| CN201725051U (en) * | 2010-07-06 | 2011-01-26 | 北京金吉奥梦科技有限公司 | Optical device and optical filter for identifying faces |
| CN101986174B (en) * | 2010-11-26 | 2012-05-23 | 中国科学院上海技术物理研究所 | Medium-wave infrared narrow band filter with wavelength of 5.25 microns |
| CN103217730B (en) * | 2013-04-18 | 2015-07-08 | 同济大学 | Narrow-band negative filter plate membrane system with gradually-changing optical thicknesses |
| CN103278874A (en) * | 2013-05-28 | 2013-09-04 | 上海梅轩实业有限公司 | Manufacturing method for machine vision filter |
| CN104155712B (en) * | 2014-08-15 | 2017-01-25 | 中国科学院上海技术物理研究所 | Near-infrared filter for optical communication |
| CN105549142A (en) * | 2016-03-03 | 2016-05-04 | 郑光威 | Dielectric film transmission type spatial narrowband filter combined device |
| CN106405709B (en) * | 2016-11-16 | 2018-12-28 | 天津津航技术物理研究所 | A kind of broadband cut-off ultra-narrow band pass filter |
| CN109212647B (en) * | 2018-10-31 | 2021-05-11 | 天津津航技术物理研究所 | Ultra-wideband cut-off filter with adjustable pass band |
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