CN-122016253-A - Large-range polarization-maintaining characteristic detection system and method based on calculation matching reflection loop

CN122016253ACN 122016253 ACN122016253 ACN 122016253ACN-122016253-A

Abstract

The invention provides a large-range polarization-preserving characteristic detection system and method based on a calculation matching reflection loop, and the large-range polarization-preserving characteristic detection system comprises an imaging ellipsometer, a non-polarizing beam splitter, a light spot amplifying reflector group and a corner reflector, wherein the imaging ellipsometer adopts an imaging Mueller matrix spectroscopic ellipsometer, a polarization state generator and a CMOS polarization detector are arranged in the imaging ellipsometer, the type and the amplifying magnification of the light spot amplifying reflector group are matched with the type and diameter parameters of a curved surface optical element to be detected in a calculation mode, the linear polarized light spot output by the imaging ellipsometer is amplified to the size of the full-coverage curved surface optical element to be detected, and the amplification magnification of an auxiliary reflector is calculated and determined according to the diameter of the curved surface to be detected through the calculation matching reflection loop.

Inventors

LI ZIZHENG
SHAO MINGQIANG
WANG YIPING
PENG JINGXIAO
LIU XINXIN
LV TIANXIANG
Liang Shanxiang
HE ZHUOHUI
TU RONGXIN

Assignees

中山大学

Dates

Publication Date: 20260512
Application Date: 20260216

Claims (10)

1. A large-scale polarization-preserving characteristic detection system based on a calculation matching reflection loop, which is characterized by comprising: the imaging ellipsometer adopts an imaging Mueller matrix spectroscopic ellipsometer, and a polarization state generator PSG and a CMOS polarization detector are arranged in the imaging Mueller matrix spectroscopic ellipsometer and are used for outputting stable linear polarized light and finishing the accurate detection and analysis of the polarization state; the non-polarized beam splitter NPBS is used for realizing the separation and beam combination of an incident light path and a reflected light path, transmitting the incident light along a preset direction and guiding the returned reflected light to the CMOS polarization detector; the light spot amplifying reflector group is a single auxiliary reflector, and the type and the amplification ratio of the auxiliary reflector are matched with the type and the diameter parameters of the curved surface optical element to be detected in a calculating way and are used for amplifying the linearly polarized light spots output by the imaging ellipsometer to the size of the curved surface optical element to be detected in a full coverage way; the corner reflector is of a multi-surface right-angle reflecting structure and is used for enabling an incident light beam to return along an original path in an original incident direction; The light-emitting end of the imaging ellipsometer is in butt joint with the light-entering end of the non-polarizing beam splitter, the transmission end of the non-polarizing beam splitter is in butt joint with the light spot amplifying reflecting mirror group, the light-emitting end of the light spot amplifying reflecting mirror group faces the detection surface of the curved surface optical element to be detected, the light-emitting direction of the reflected light of the curved surface optical element to be detected faces the corner reflector, the reflected light of the corner reflector is transmitted to the non-polarizing beam splitter after passing through the curved surface optical element to be detected and the light spot amplifying reflecting mirror group, and the reflection end of the non-polarizing beam splitter is in butt joint with the light-entering end of the CMOS polarization detector.
2. The large-scale polarization-preserving characteristic detection system based on a calculation matching reflection loop of claim 1, wherein the type of the auxiliary reflector corresponds to the type of the curved optical element to be detected one by one, and when the curved optical element to be detected is an off-axis parabolic mirror OAP, the auxiliary reflector is an auxiliary off-axis parabolic mirror; when the curved surface optical element to be detected is a hyperboloid mirror, the auxiliary reflecting mirror is an auxiliary hyperboloid mirror; When the curved surface optical element to be measured is a free-form surface mirror, the auxiliary reflecting mirror is an auxiliary free-form surface mirror.
3. A large-scale polarization maintaining characteristic detection system based on a calculated matching reflection loop as set forth in claim 2, wherein the auxiliary mirror has a magnification ratio The method comprises the following steps: In the formula, The diameter of the curved surface optical element to be measured; is the maximum spot size of the imaging ellipsometer.
4. The large-scale polarization-preserving characteristic detection system based on the calculation matching reflection loop of claim 1, further comprising a collimating lens and an imaging lens, wherein the collimating lens is an anti-spherical-aberration plano-convex lens, and is arranged between the imaging ellipsometer and the non-polarizing beam splitter NPBS and used for collimating a light beam emitted by the laser source into parallel light; The imaging lens is a double-cemented achromatic lens and is arranged between the non-polarized beam splitter NPBS and the CMOS polarization detector, and is used for precisely imaging polarized light reflected by the non-polarized beam splitter NPBS to a focal plane of the CMOS detector.
5. The system for detecting wide range polarization maintaining characteristics based on a computed matching reflection loop as set forth in claim 4, further comprising a polarization analyzer PSA disposed between the non-polarizing beam splitter NPBS and the CMOS polarization detector for performing polarization analysis on the returned reflected light to extract the reflected light 、 Phase difference of polarization components Amplitude ratio And converting the optical polarization signal into an electric signal and transmitting the electric signal to the CMOS polarization detector.
6. The large-range polarization-maintaining characteristic detection method based on the calculation matching reflection loop is characterized by comprising the following steps of: s1), calculating and matching to obtain an auxiliary reflector with a corresponding type and an amplification factor according to the type and diameter parameters of the curved surface optical element to be detected, and constructing a large-range polarization-maintaining characteristic detection system; S2), starting an imaging ellipsometer, setting the detection wavelength of the imaging ellipsometer, outputting linearly polarized light, adjusting the size of a light spot to the maximum, transmitting the incident light to an auxiliary reflector through a non-polarized beam splitter NPBS, amplifying the incident light by the auxiliary reflector, then entering the central area of a curved surface optical element to be detected, and reflecting the light to a corner reflector through the curved surface optical element to be detected; s3), the non-polarized beam splitter NPBS reflects the returned reflected light to the CMOS polarization detector, and the CMOS polarization detector collects the parameters of the reflected light; S4, compensating phase distortion introduced by the optical component through a data analysis module of the imaging ellipsometer, and then collecting the phase difference of reflected light collected by each region of the curved surface optical element to be tested Comparing the phase difference with the reference phase difference of the incident light in the step S1), calculating to obtain phase difference offset of each area, and generating a polarization maintaining characteristic phase difference distribution map of the curved optical element to be detected; s5), if the phase difference offset of the whole area of the curved surface optical element to be detected is smaller than or equal to the polarization maintaining judgment threshold value, judging that the polarization maintaining characteristics of the curved surface optical element to be detected are qualified; If the phase difference offset of the local area is larger than the polarization maintaining judgment threshold, marking the position and the parameter of the distortion area, and adjusting the parameters and the positions of the collimating lens and the imaging lens for secondary measurement after geometric distortion correction.
7. The method for detecting the large-scale polarization-maintaining characteristic based on the calculation matching reflection loop as claimed in claim 6, wherein in the step S1), a standard polaroid is adopted to calibrate the large-scale polarization-maintaining characteristic detection system under the detection wavelength, and a reference phase difference is recorded ; The core of the calibration of the large-range polarization-preserving characteristic detection system is that the linear polarized light output by an imaging ellipsometer is transmitted in a closed loop manner through an empty light path without a curved surface to be detected, and then the phase difference acquired by a CMOS polarization detector is obtained Is 0 deg..
8. The method for detecting the large-scale polarization maintaining characteristics based on the calculation matching reflection loop according to claim 6, wherein in the step S4), the error is induced by the system factor stripping elimination device, and the phase distortion introduced by the optical component is compensated, as follows: ; Wherein, the As a factor of the transmittance of the PSA, As a factor of the transmittance of the PSG, Is a sample true signal; representing measured light intensity values for combinations of PSG and PSA polarization conditions; Representing the system light intensity constant.
9. The method for detecting the large-scale polarization maintaining characteristics based on the calculation matching reflection loop according to claim 6, wherein in the step S5), the geometric distortion correction object is field curvature and distortion error of a detection system, wherein the correction of the field curvature error obtains a flat field mapping model through focal plane fitting, and the pixel data of a curved focal plane is projected to a standard flat field; correcting the distortion error, namely calibrating the distortion coefficient to obtain a pixel scaling model, scaling pixels in the edge area in equal proportion, and matching the magnification of the central area; For each pixel point collected by the CMOS detector Original coordinates of (c) Performing field curvature correction to convert the curved focal plane coordinates into standard flat field coordinates The method comprises the following steps: ; ; In the formula, Is the deviation value of the actual focal plane and the standard flat field focal plane; the correction coefficient is the field curvature; the radial distance from the pixel point to the center of the curved surface; For corrected standard flat field coordinates Performing distortion correction to obtain coordinates after distortion correction The method comprises the following steps: ; ; In the formula, Is a distortion correction coefficient; The effective detection radius of the curved optical element to be detected; is the relative radial position of the pixel point; Then the coordinates after distortion correction Remapping the geometric distortion corrected phase difference data matrix with the actual physical coordinates of the curved optical element to be measured; based on the corrected phase difference data matrix, marking a distortion region with a phase difference offset larger than a polarization-preserving judgment threshold value, and recording the corrected physical center coordinates of the distortion region And area radius 。
10. The method for detecting wide-range polarization maintaining characteristics based on a calculated matching reflection loop as claimed in claim 9, wherein in step S5), said parameters of said collimating lens include a focal length of said collimating lens Axial position of collimating lens Radial position of collimator lens The parameters of the imaging lens comprise the focal length of the imaging lens Axial position of imaging lens And imaging lens radial position ; If the abnormal area is the curved surface edge area of the curved surface optical element to be measured, fine-tuning the radial position of the collimating lens The optical axis of the incident parallel light is shifted to the abnormal area to ensure the full coverage of the abnormal area, and the radial position of the imaging lens is finely adjusted Matching the optical axis offset of the reflected light to enable an imaging light spot of the abnormal region to be positioned at the center of a pixel matrix of the CMOS detector; if the phase difference data of the abnormal region has blurring and noise points, fine-tuning the axial position of the imaging lens Adjusting the imaging focal plane position to precisely image the reflected light to the photosensitive surface of the CMOS detector, or fine-tuning the axial position of the collimating lens Optimizing the collimation of the incident light; And if the spot size of the abnormal area is not matched with the actual physical area, finely adjusting the focal length of the collimating lens and the focal length of the imaging lens.

Description

Large-range polarization-maintaining characteristic detection system and method based on calculation matching reflection loop Technical Field The invention relates to the technical field of optical devices, in particular to a large-range polarization-maintaining characteristic detection system and method based on a calculation matching reflection loop. Background Curved optical elements such as off-axis parabolic mirrors, hyperboloid mirrors, free-form surface mirrors and the like are widely applied to high-end optical systems such as laser communication, astronomical observation, precise spectrum analysis, high-end lithography and the like by virtue of excellent performances of the curved optical elements in aspects of beam collimation, focusing, angle conversion and aberration suppression. In these applications, especially in polarization sensitive optical systems, the polarization-preserving properties of the curved optical element directly determine the polarization-state fidelity and overall performance of the system—if the curved element generates uncontrollable polarization-state distortion during the beam reflection, signal attenuation, phase shift, and even information loss can result. From the current state of academic research and technical application, the existing curved surface polarization characteristic detection technology is mainly based on the design of a traditional ellipsometer (UE) or an early Return Path Ellipsometer (RPE), when the traditional UE measures a curved surface, if the normal direction of the surface is obviously inclined, reflected light cannot reach a detector, the position of the detector needs to be frequently adjusted, and the inclined normal direction of the surface can cause the reference system of a Polarization State Generator (PSG) to be mismatched with the p/s polarization direction, so that additional measurement errors are introduced. Although the stability of the early-stage return path ellipsometer RPE is improved through a loop reflection design, the early-stage return path ellipsometer RPE is mostly constructed based on a spherical mirror or a plane mirror, for example, the return path ellipsometer RPE based on the spherical mirror can only be measured in the center or near-center area of a rotating wafer, and cannot adapt to an Imaging Ellipsometer (IE) with a large beam diameter, the return path ellipsometer RPE based on the plane mirror does not solve the problem of large-range coverage, can only realize small-range local detection, and cannot meet the requirements of large-caliber curved surface full-area polarization-preserving detection. The existing curved optical element polarization characteristic detection technology has obvious limitation, and can be generalized into three core pain points by combining academic research results and engineering application practices, namely, the detection range and the suitability of light beams are limited, the traditional UE depends on small light spot incidence, only local area detection can be realized, and the error is easy to introduce in point-by-point splicing. Even if the early RPE adopts a loop design, the early RPE is limited by a reflector structure, cannot adapt to the imaging detection requirement of a large beam diameter, can only cover a small-range area (generally not more than 50mm multiplied by 50 mm), is difficult to cover a large-caliber curved surface edge area, and is easy to miss the problem of edge polarization distortion. Secondly, the problem of matching between polarization interference and a reference system is outstanding, the traditional UE has no closed loop optical path design, the reflection of an element interface, air scattering and optical path offset in optical path transmission all introduce additional polarization change, the mismatch of the reference system can aggravate errors when the surface is inclined, and the early RPE reduces the interference of the optical path offset but does not solve the systematic distortion compensation problem in the polarization state transmission process and is difficult to accurately distinguish from the self polarization distortion of a curved surface. Thirdly, the suitability of the curved surface is insufficient, the prior art is designed aiming at a specific type of curved surface (such as a rotary wafer), a general scheme capable of adapting to multiple complex curved surfaces such as an off-axis parabolic mirror (OAP), a hyperboloid, a free curved surface and the like is not formed, for example, the RPE based on a spherical mirror is only applicable to a small-size curved surface with rotational symmetry, and cannot adapt to an asymmetric free curved surface. Therefore, there is a need for a curved surface polarization maintaining detection method that has a wide range of coverage, low interference, high accuracy and strong adaptability. Disclosure of Invention Aiming at the defects of small detection range, more polarization interfe