CN-121995624-A - Annular band pupil modulation high-contrast star crown instrument transmittance smooth design and working method

CN121995624ACN 121995624 ACN121995624 ACN 121995624ACN-121995624-A

Abstract

The invention discloses a ring-belt pupil modulation high-contrast star crown instrument transmittance smooth design and a working method. The method carries out annular radial transmissivity gradual change modulation on the telescope pupil, and realizes the inhibition of fixed star Jiang Yanshe light. The design concept of the annular zone transmittance gradient pupil modulation adopts limited annular zones, the transmittance of each annular zone is the same, and the energy distribution of the star at the pupil position of the optical system is changed by further restricting the transmittance difference between adjacent annular zones, so that the optimal high-contrast imaging performance is realized. The modulation band makes the transmittance design curve of the modulation band integrally smooth by restraining the transmittance difference of adjacent bands, can overcome the manufacturing process difficulty caused by severe transition of the transmittance of the traditional optical filter, further ensures the processing precision, can relieve the problems of wave front phase transition and the like caused by abrupt change of the thickness of a film, and further finally improves the high contrast imaging performance of the whole system.

Inventors

Dou Jiangpei
CHEN XIANGPENG

Assignees

中国科学院南京天文光学技术研究所

Dates

Publication Date: 20260508
Application Date: 20260303

Claims (7)

1. A ring belt pupil modulation high-contrast star crown instrument transmittance smooth design and working method are characterized in that a ring belt transmittance gradual change pupil modulation technology is adopted to conduct ring-shaped radial transmittance gradual change modulation on a telescope pupil to inhibit fixed star Jiang Yanshe light, the ring belt transmittance gradual change pupil modulation adopts an equal-width and limited ring belt, the transmittance of the same ring belt is consistent to change the energy distribution of the fixed star at the pupil position of an optical system to achieve optimal high-contrast imaging performance, the transmittance modulation belt of the limited belt is used for restraining the transmittance difference between adjacent belts to enable a final transmittance design curve to be integrally smooth so as to ensure the processing precision of transmittance stripe paper sheets, and the transmittance gradual change modulation method comprises the following steps: Determining the imaging contrast requirement of a system, improving the contrast performance of final imaging by increasing the number of endless belts, and determining the number of modulation belts; setting initial transmittance distribution of a modulation annular zone, and introducing a smoothness constraint factor for limiting transmittance difference between adjacent annular zones; Establishing a composite evaluation function containing contrast performance and transmittance smoothing indexes, synchronously adjusting transmittance values of all bands in an optimization process, and ensuring smooth transition of high-contrast imaging performance and transmittance curves through setting the composite evaluation function; step four, the initial transmittance value of the annular belt is brought into a high contrast imaging calculation simulation system, and the transmittance value of each belt is independently updated through an iterative optimization algorithm; And fifthly, calculating imaging contrast in the target detection area in real time, judging whether the preset ultrahigh contrast performance is met, calculating a total transmittance smoothness constraint factor of the ring, and judging whether the preset smoothness performance is met.
2. The method for smoothing the transmittance of an annulus pupil modulated high contrast star crown instrument according to claim 1, wherein the smoothness constraint factor adopts a root mean square slope value, and the transmittance difference between adjacent annuli is constrained by minimizing the root mean square slope value, thereby improving the stability of the manufacturing process, wherein a decrease in the root mean square slope value indicates an improvement in the smoothness performance, an increase in the root mean square slope value, and a decrease in the smoothness performance.
3. The ring belt pupil modulated high contrast coronagraph transmittance smoothing design and operation method of claim 2, wherein the smoothness constraint factor is expressed as follows: ; Where T represents the transmittance value of each zone and N represents the number of zones.
4. The method for smoothly designing and operating the ring-belt pupil modulated high-contrast star crown according to claim 1, wherein the contrast performance is referenced to an objective function, the objective function is a ratio of a sum of point spread functions in an optimized region to a sum of point spread functions in a central region, the objective function value is reduced to indicate that the contrast performance is improved, the objective function value is increased to indicate that the contrast performance is reduced.
5. The method of claim 4, wherein the electric field intensity of the constant star light in the pupil plane of the optical system is expressed as: ; Wherein the method comprises the steps of Is a pupil function; At the back focal plane of the imaging system, the Point Spread Function (PSF) can be expressed as the square of the pupil function modulo: ; Wherein the method comprises the steps of Representing a fourier transform; The contrast objective function is expressed as: ; Where I PSF(optimized) represents the optimized intra-region point spread function and I PSF(core) represents the central intra-region point spread function.
6. The method according to claim 1, wherein the composite evaluation function is formed by combining a contrast performance objective function and a smoothness constraint factor through product, and is used for simultaneously constraining contrast improvement and curve smoothness in an iterative process, and the composite evaluation function is expressed as: ; wherein n, m is an index; The contrast objective function is expressed as: ; Wherein I PSF(optimized) represents the optimized intra-region point spread function, and I PSF(core) represents the central intra-region point spread function; The smoothness constraint factor is expressed as follows: ; Where T represents the transmittance value of each zone and N represents the number of zones.
7. The method of claim 1, wherein a point spread function image of a high contrast dark field is obtained on a back focal plane imaged by a ring-belt pupil modulated high contrast coronagraph system, and an imaging contrast after amplitude modulation is tested in a diagonal direction.

Description

Annular band pupil modulation high-contrast star crown instrument transmittance smooth design and working method Technical Field The invention belongs to the technical field of astronomical optics high contrast imaging, and particularly relates to a star crown instrument pupil transmittance gradient modulation filter for solar system external planet direct imaging and an optimal design method thereof. Background Direct imaging of the outer planet is a great challenge in astronomical research. Because of the large intensity difference between stars and planets, contrast in the visible band needs to be better than 10 -9, and therefore a coronagraph system must be used to suppress the intense diffracted light of the stars. Pupil modulation based on transmittance gradient is one of the core techniques of high contrast star crown instruments. Conventional optimization algorithms tend to produce solutions where the transmittance of adjacent regions varies too much, which means that there will be significant differences in the thickness of the metal film layers of adjacent regions during actual processing. The abrupt change in structure not only greatly increases the control difficulty and the manufacturing cost of the film coating process, but also causes the problems of wave front phase jump and the like due to abrupt change of the film thickness, and influences the contrast performance of the system. Disclosure of Invention The invention aims to solve the problem that the manufacturing process is difficult due to the fact that the transmittance gradient modulation of the existing annular zones causes large transmittance difference between adjacent annular zones, and the final high-contrast imaging performance is degraded due to the influence of processing errors. In order to achieve the above purpose, the present invention provides the following technical solutions: A ring belt pupil modulation high contrast star crown instrument transmissivity smooth design and working method adopts ring belt transmissivity gradual change pupil modulation technology, the transmissivity of each ring belt is the same, and circular radial transmissivity gradual change modulation is carried out. The modulation scheme improves contrast performance by optimizing the annulus transmittance distribution while optimizing the smoothness performance between adjacent annuli, and is considered as pupil amplitude modulation completion when the contrast performance reaches 10 -7 and the smoothness performance index reaches expectations. Further, the smoothness performance takes a smoothness constraint factor as a reference, the smoothness constraint factor is a root-mean-square slope value of the girdle, the root-mean-square slope value is reduced to indicate that the smoothness performance is improved, and the root-mean-square slope value is increased to indicate that the smoothness performance is reduced. Further, the smoothness constraint factor is expressed as: Where T represents the transmittance value of each zone and N represents the number of zones. The electric field strength of the constant star light in the pupil plane can be expressed as: Wherein the method comprises the steps of Is a pupil function. At the back focal plane of the imaging system, the point spread function can be expressed as the square of the pupil function modulo: Wherein the method comprises the steps of Representing the fourier transform. From the formula, it can be seen that the point spread function I PSF is related to the amplitude a, and that the square of the amplitude is the transmittance, and that the annular pupil modulation scheme achieves the purpose of changing the energy distribution of the light by changing the amplitude of the light. Further, the contrast objective function is the ratio of the sum of the point spread functions in the optimized region to the sum of the point spread functions of the reference region, the objective function is reduced, which indicates that the contrast performance is improved, the objective function is increased, which indicates that the contrast performance is reduced, and the contrast objective function is expressed as: further, the contrast performance objective function and the smoothness constraint factor are combined by a product, and are used for simultaneously constraining contrast improvement and curve smoothness in the iterative process, and the composite evaluation function is expressed as: where n, m is an index. Further, optimizing parameters of the composite evaluation function, controlling amplitude values of all the endless belts by using an iterative optimization algorithm, calculating a composite evaluation function value, judging whether the comprehensive performance is improved according to the trend of the composite evaluation function, if the trend of the composite evaluation function is improved, which means that the comprehensive performance is reduced, changing algorithm parameters and the pa