CN114624877A - Design method of large-field-of-view diffraction lens working in infrared band - Google Patents
Design method of large-field-of-view diffraction lens working in infrared band Download PDFInfo
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- CN114624877A CN114624877A CN202210257098.3A CN202210257098A CN114624877A CN 114624877 A CN114624877 A CN 114624877A CN 202210257098 A CN202210257098 A CN 202210257098A CN 114624877 A CN114624877 A CN 114624877A
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- 238000000034 method Methods 0.000 title claims abstract description 27
- 238000013461 design Methods 0.000 title claims abstract description 14
- 230000003287 optical effect Effects 0.000 claims abstract description 44
- 239000000463 material Substances 0.000 claims abstract description 13
- 238000005457 optimization Methods 0.000 claims abstract description 8
- 238000003754 machining Methods 0.000 claims description 4
- 230000035772 mutation Effects 0.000 claims description 4
- 230000006835 compression Effects 0.000 claims description 2
- 238000007906 compression Methods 0.000 claims description 2
- 238000012545 processing Methods 0.000 abstract description 7
- 238000010191 image analysis Methods 0.000 abstract 1
- 239000002245 particle Substances 0.000 abstract 1
- 238000010586 diagram Methods 0.000 description 4
- 230000004075 alteration Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000006978 adaptation Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000007516 diamond turning Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- GNPVGFCGXDBREM-UHFFFAOYSA-N germanium atom Chemical compound [Ge] GNPVGFCGXDBREM-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0012—Optical design, e.g. procedures, algorithms, optimisation routines
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1876—Diffractive Fresnel lenses; Zone plates; Kinoforms
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Abstract
The invention discloses a design method of a large-field-of-view diffraction lens working in an infrared band, which is different from the prior method that approximate microstructure height is obtained by a phase inversion or optimization method, but the microstructure is directly calculated, and a self-defined surface type which can be loaded by optical design software is provided, and the self-defined surface type can obtain a sudden change structure which is not contained in the prior optical design software and is similar to a Fresnel lens. The obtained microstructure can be further processed by using a ray tracing method, for example, defocusing is calculated, and data such as PSF (particle swarm optimization) can be further subjected to image analysis, processing and other operations. The invention can directly calculate and simulate the height of the microstructure through the wavelength and the material refractive index required in the optical design, and is suitable for both visible light and infrared bands.
Description
Technical Field
The invention relates to the technical field of optical lenses, in particular to a design method of a large-field-of-view diffraction lens working in an infrared band.
Background
With the presentIn the development of optical technology, the requirement of optical system resolution is higher and higher, and according to the resolution formula
Where λ is the operating wavelength of the optical system and D is the aperture of the optical system. From this equation, when the resolution is increased, the resolution θ needs to be decreased, which requires the aperture D of the optical system to be continuously increased, and the increase of the aperture causes problems such as high precision required for processing, complex optical system, and heavy optical system. This results in limited lightweight imaging of optical systems, especially for portable devices such as cell phone cameras, and space telescopes that require a launch vehicle for shipping, which present significant challenges. Furthermore, the high precision optical system brings with it the need for high precision machining techniques for lenses and very tight tolerance assignments, which is very disadvantageous for the mass production of optical systems.
With the development of semiconductor micro-nano processing and optics, researchers have begun to use diffractive optical systems as a solution to replace conventional catadioptric optical systems. The diffraction lens has strong negative dispersion, so a large number of optical structures such as refraction/diffraction optical systems, double/multilayer diffraction elements and Schupmann achromatic optical structures are designed to eliminate the dispersion of the diffraction lens. However, most of these structures severely limit the field of view to a small range and still require a rear optical system for aberration correction. The high precision alignment required for dual/multi-layer diffractive elements, for example, also leaves this structure in the process of simulation. These structures limit the use of diffractive lenses in large field-of-view optical systems.
Disclosure of Invention
The invention provides a design method of a diffraction lens, which aims to solve the problems that the field of view of an optical system is limited and the optical system is relatively bulkier due to the fact that the existing diffraction optical system achieves the purpose of achromatism.
In order to solve the above problems, the present invention provides the following technical solutions:
a design method of a large-field-of-view diffraction lens working in an infrared band is provided, wherein the diffraction lens consists of annular zones with different microstructures, and the microstructure solving step comprises the following steps:
step S1, determining the working target wave band, and determining the optical material used in the optical design of the wave band;
step S2, determining the aperture and focal length data of the needed diffraction lens;
step S3, according to the working wavelength and the refractive index of the needed material, the microstructure height is solved; specifically, the height of each microstructure is calculated according to a phase compression formula, wherein the expression is as follows:
wherein HdoeIs the microstructure height, p is the parameter of the microstructure height, λ0N is the refractive index of the desired material for the operating wavelength of the diffractive lens;
step S4, determining the maximum radius of each zone according to the height of the microstructure, and calculating the curvature radius data of the zone, wherein the expression is as follows:
wherein HdoeIs the height of the microstructure, RmaxC is the curvature radius of the solved point, and k is the conc coefficient of the solved point;
and step S5, obtaining the microstructure data of the diffraction lens according to the aperture, the focal length, the microstructure height and the curvature radius of the diffraction lens.
Further, the microstructure height increases with increasing p, where p is a positive integer greater than 1, with p values around 200 being preferred.
Further, after the data of each annular zone is obtained, the user-defined surface is loaded by using optical design software, and the data is input for optimization.
Further, the optical design software obtains the surface profile with the mutation structure by loading the custom profile, and the flow of optimizing and solving the surface profile coordinate comprises the following steps:
step S11, determining the previous surface of the microstructure, determining the offset of the end point of the surface relative to the center of the incident surface according to the data of the surface, and forming the microstructure of the previous surface of the diffraction lens;
step S12, determining the radial coordinate of the Z-th area starting point, and determining the offset relative to the previous surface end point;
step S13, adding the offset of the previous surface at the specified point of S12 to obtain the total offset of the end point of the area;
step S14, determining the radial coordinate of the given point, determining the area where the given point is located, and calculating the total offset of the given point; wherein the given point is a non-end point;
in step S15, a diffraction lens cross-sectional view is drawn based on the data.
Further, the diffraction lens coordinate data obtained after the optimization is used for processing.
The technical scheme provided by the invention has the following beneficial effects:
1. the invention has simple design principle and high efficiency.
2. The problem that the existing optical design software cannot obtain a mutation structure similar to a Fresnel lens is solved.
3. Has certain technical characteristics and is difficult to imitate.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a design scheme for a large field of view diffractive lens operating in the infrared band provided by the present invention;
FIG. 2 is a flow chart of the custom surface calculation provided by the present invention;
FIG. 3 is a diagram of a system dot-column resulting from optimization of optical design software;
FIG. 4 is a schematic cross-sectional view of a diffractive lens;
fig. 5 is a schematic diagram of the diffraction lens obtained by processing.
Detailed Description
The invention is further described with reference to the following figures and specific examples.
The present example provides a method for designing a large field of view diffractive lens operating in the infrared band, wherein the large field of view diffractive lens is composed of microstructures having a height difference and a mutation structure calculated according to an aspheric formula. The method is combined with optical design software, and designs the large-field diffraction lens with simple principle, convenient processing and excellent performance, and concretely, as shown in figure 1, the method comprises the following steps:
s1, determining the working target wave band, and determining the optical material used in the optical design of the wave band; wherein the optical material is a material with easy processing performance in the target working waveband; specifically, the present embodiment is designed for an incident wavelength band at 9-11 μm in the infrared wavelength band, with 9 μm as the center wavelength, and the optical material used is germanium (refractive index of 4).
S2, determining the aperture, focal length and other data of the required diffraction lens; the diameter of the diffraction lens is 50mm, the focal length is 74.878mm, the F number is 4.5, and the angle of field is 21 degrees.
S3, calculating the height of the microstructure according to the working wavelength and the refractive index of the required material; wherein, selecting p as 20, calculating the height of the microstructure, and the expression is as follows:
wherein HdoeIs the height of the microstructure, RmaxFor the maximum radius of each zone, c is the radius of curvature of the sought point, and k is the conic coefficient of the sought point.
S4, determining data such as curvature radius and the like according to the height of the microstructure; the expression is as follows:
wherein HdoeIs the height of the microstructure, RmaxFor the maximum radius of each zone, c is the radius of curvature of the sought point, and k is the conic coefficient of the sought point.
S5, the diffraction lens microstructure data is obtained from the data.
And after the data of each annular band is obtained, loading a user-defined surface by using optical design software, and inputting the data for optimization. Specifically, in this embodiment, the maximum radius of each zone is (in mm): 2.5,5,7.5,10,12,13.75,15.3,16.7,18,19.22,20.37,21.45,22.48,23.47,24.42,25.5, the conic coefficient of each zone being 0, the radius of curvature of each zone being respectively (in mm): 229.214, 229.381,229.650,229.894,230.106,230.276,230.431,230.590,230.740,230.917,231.092,231.226, 231.414, 231.602, 231.839, 231.975.
In this example, the diffraction lens is optimized by using optical design software, and a flow chart of a user-defined surface DLL loaded by the optical design software is shown in fig. 2, and the light spot distribution in the infrared range under the conditions including vertical incidence and large-angle incidence is obtained through simulation. Fig. 3 is a system point diagram of incident light at various angles after passing through an optical system, and the point diagram shows that light spot distribution is located in airy disk under different incident angles, belongs to a diffraction limited system, and shows that the diffraction lens has an excellent large-field-of-view function in a working waveband.
From the resulting data, a cross-sectional view of the diffractive lens is drawn, as shown in FIG. 4.
Fig. 5 shows the diffraction lens finally obtained by machining by using a diamond turning technique, and the diffraction lens has the characteristics of convenience in machining and small error.
In summary, the invention can determine the microstructure height of the diffraction lens by selecting the parameter p according to the wavelength of the diffraction lens and the optical material required by focusing, and can obtain the specific parameter of each coordinate by reasonably setting the maximum radial coordinate of each zone. The used microstructures are quadric surfaces, complex configurations do not exist, the tolerance of the diffraction lens to errors is good, and the imaging function of the single-chip large-view-field lens can be realized.
Further, it should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or terminal that comprises the element.
Finally, it should be noted that while the above describes a preferred embodiment of the invention, it will be appreciated by those skilled in the art that, once having the benefit of the teaching of the present invention, numerous modifications and adaptations may be made without departing from the principles of the invention and are intended to be within the scope of the invention. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the embodiments of the invention.
Claims (5)
1. A design method of a large-field diffraction lens working in an infrared band is characterized in that the diffraction lens consists of annular zones with different microstructures, and the microstructure solving step comprises the following steps:
step S1, determining the working target wave band, and determining the optical material used in the optical design of the wave band;
step S2, determining the aperture and focal length data of the needed diffraction lens;
step S3, according to the working wavelength and the refractive index of the needed material, the microstructure height is solved; specifically, the height of each microstructure is calculated according to a phase compression formula, wherein the expression is as follows:
wherein HdoeIs the microstructure height, p is the parameter of the microstructure height, λ0N is the refractive index of the desired material for the operating wavelength of the diffractive lens;
step S4, according to the height of the microstructure, determining the maximum radius of each zone, and calculating the curvature radius data of the zone, wherein the expression is as follows:
wherein HdoeIs the height of the microstructure, RmaxC is the curvature radius of the solved point, and k is the conc coefficient of the solved point;
and step S5, obtaining the microstructure data of the diffraction lens according to the aperture, the focal length, the microstructure height and the curvature radius of the diffraction lens.
2. The method of claim 1 wherein the microstructure height increases with increasing p, where p is a positive integer greater than 1, and wherein p has a value of about 200 is more effective.
3. The method of claim 1, wherein the data for each zone is obtained and then optimized by inputting data by loading a custom surface using optical design software.
4. The method as claimed in claim 3, wherein the optical design software obtains the surface profile with a mutation structure by loading a custom profile, and the process of performing the optimization solution on the coordinates of the surface profile comprises:
step S11, determining the data of the previous surface of the microstructure, determining the offset of the end point of the surface relative to the center of the incident surface, and forming the microstructure of the previous surface of the diffraction lens;
step S12, determining the radial coordinate of the Z-th area starting point, and determining the offset relative to the previous surface end point;
step S13, adding the offset of the previous surface at the specified point of S12 to obtain the total offset of the end point of the area;
step S14, determining the radial coordinate of the given point, determining the area where the given point is located, and calculating the total offset of the given point; wherein the given point is a non-end point;
in step S15, a diffraction lens cross-sectional view is drawn based on the data.
5. The method of designing a large field of view diffractive lens operating in the infrared band as claimed in claim 3, characterized in that the machining is performed using the diffraction lens coordinate data obtained after the optimization.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10186231A (en) * | 1996-10-24 | 1998-07-14 | Asahi Optical Co Ltd | Method for designing diffraction lens |
| CN112394523A (en) * | 2019-08-19 | 2021-02-23 | 上海鲲游光电科技有限公司 | Dodging element, random rule manufacturing method and system thereof and electronic device |
| CN113281830A (en) * | 2021-05-19 | 2021-08-20 | 烟台艾睿光电科技有限公司 | Lens and optical lens |
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- 2022-03-16 CN CN202210257098.3A patent/CN114624877B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10186231A (en) * | 1996-10-24 | 1998-07-14 | Asahi Optical Co Ltd | Method for designing diffraction lens |
| CN112394523A (en) * | 2019-08-19 | 2021-02-23 | 上海鲲游光电科技有限公司 | Dodging element, random rule manufacturing method and system thereof and electronic device |
| CN113281830A (en) * | 2021-05-19 | 2021-08-20 | 烟台艾睿光电科技有限公司 | Lens and optical lens |
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