Vacuum light pipe stabilization system and method with seal protection

Abstract

This invention discloses a vacuum collimator stabilization system and method with sealed protection, relating to the field of optical device testing technology. The method includes: acquiring reference optical performance data in advance; simultaneously acquiring system status data when the optical system under test is installed in the vacuum collimator and undergoes formal testing; calculating pupil mapping transformation parameters based on the system status data and the reference optical performance data; performing pupil plane coordinate alignment and aberration correction on the reference optical performance data according to the pupil mapping transformation parameters to obtain reference optical performance data matching the current state; and performing difference operations or deconvolution operations on the acquired observed optical performance data and the reference optical performance data matching the current state to obtain the true optical performance data of the optical system under test. This invention can adapt to various optical performance testing scenarios, ensure the accuracy of the performance data of the system under test, and reduce misjudgments of the performance of the system under test.

Description

Technical Field

[0001] This invention relates to the field of optical device testing technology, and more specifically, to a vacuum optical tube stabilization system and method with sealed protection. Background Technology

[0002] In the field of performance calibration and acceptance of high-precision optical systems such as aerospace optical payloads and extreme ultraviolet lithography machine optical components, vacuum collimators, as core ground testing equipment, are widely used to simulate the infinity parallel light incident conditions in the vacuum environment of space, in order to achieve high-precision measurement of the wavefront aberrations of the optical system under test. In the actual testing process, in order to eliminate the interference of aberrations introduced by the vacuum collimator's own optical system on the measurement results, the engineering practice generally adopts a calibration-then-subtraction approach. That is, before formally measuring the optical system under test, the aberrations of the vacuum collimator itself are calibrated to obtain the corresponding reference aberration data. Then, the reference aberration is subtracted from the combined aberrations of the optical system under test and the vacuum collimator measured subsequently, thereby separating the true aberrations of the optical system under test and providing data support for the performance evaluation and optimization of the optical system.

[0003] The aforementioned aberration subtraction method is based on the superposition and decomposability of wavefront aberrations. It uses orthogonal polynomial systems such as Zernike polynomials to perform modal decomposition of the reference and observed aberrations, and then performs numerical subtraction on the same modal dimension. A key prerequisite for the effective implementation of this method is that the calibration process of the reference aberration and the observation process of the optical system under test are in a completely consistent measurement state. Specifically, this includes a perfect match between the pupil diameter, pupil center position, pupil plane rotation angle, and pupil plane scaling ratio corresponding to the reference and observed aberrations. Furthermore, it assumes that the aberrations of the vacuum collimator remain stable within one vacuuming cycle and do not change significantly over time.

[0004] However, in the actual operation of a vacuum collimator, the aforementioned default assumptions are systematically disrupted by various factors in the vacuum environment, leading to pupil mapping drift. During vacuuming, gas refilling, and temperature gradient changes, the observation window of the vacuum chamber deforms due to internal and external pressure differences and thermal stress. This deformation not only alters the refractive properties of the observation window itself but also causes the parallel beam passing through it to deflect, resulting in a shift in the pupil plane position. Heat exchange in a vacuum environment is primarily radiative. The lens barrel and support structure of the vacuum collimator undergo thermally induced micro-deformation during radiative heat exchange. This deformation directly causes a drift in the effective aperture position of the collimator, disrupting the consistency of the pupil aperture corresponding to the reference aberration and the observed aberration.

[0005] Turntables or six-degree-of-freedom platforms used to adjust the incident attitude of the light beam exhibit significant creep and hysteresis under vacuum conditions due to changes in lubrication. This leads to a decrease in the platform's repeatability and causes the pupil plane rotation angle and scaling ratio to deviate from the reference calibration state during observation. Simultaneously, the micro-vibrations generated during the operation of the vacuum pump unit are transmitted to the optical system of the vacuum collimator, causing the beam to oscillate slightly and periodically on the pupil plane. This oscillation is solidified into an equivalent geometric deviation during long-exposure measurements or averaging of multiple measurements, further exacerbating the pupil mapping drift. This non-physical residual can be misinterpreted as thermal aberrations generated by the tested optical system under vacuum, leading technicians to make incorrect assessments of the system's performance. In severe cases, this can cause deviations in the acceptance conclusions of high-precision optical systems, allowing unqualified optical components to enter subsequent production or assembly stages. This increases the risk of on-orbit failure of aerospace optical payloads and substandard lithography accuracy in lithography machines. Furthermore, misinterpretations can trigger unnecessary rework and optimization of the optical system, significantly increasing the research and development and manufacturing costs.

[0006] In view of this, the present invention proposes a vacuum light tube stabilization system and method with sealed protection to solve the above problems. Summary of the Invention

[0007] To overcome the aforementioned deficiencies of the prior art and achieve the above objectives, the present invention provides the following technical solution: a vacuum optical tube stabilization method with sealed protection, comprising:

[0008] Pre-acquire reference optical performance data;

[0009] When the optical system under test is installed in the vacuum collimator and undergoes formal testing, test data is collected simultaneously. The test data includes deformation data of the vacuum chamber observation window, thermal deformation data of the vacuum collimator lens barrel and support structure, and internal sensing data of the optical system under test. The test data is then time-aligned and denoised and fused to generate system status data.

[0010] Calculate pupil mapping transformation parameters based on system state data and reference optical performance data;

[0011] Based on the pupil mapping transformation parameters, pupil plane coordinate alignment and aberration correction are performed on the reference optical performance data to obtain reference optical performance data that matches the current state;

[0012] The collected observed optical performance data is compared with the reference optical performance data that matches the current state by performing differential or deconvolution operations to obtain the true optical performance data of the optical system under test.

[0013] Furthermore, the pupil mapping transformation parameters include pupil plane coordinate translation, pupil plane rotation angle deviation, pupil plane scaling ratio deviation, and reference aberration correction.

[0014] Furthermore, the reference aberration correction is determined jointly by the deformation data of the vacuum chamber observation window and the thermal deformation data of the vacuum collimator lens barrel and support structure. The reference aberration correction is constrained based on the internal sensing data of the optical system under test to eliminate the interference of the optical system under test's own changes on the pupil mapping transformation parameters.

[0015] Furthermore, the observation window deformation sensitivity coefficient and thermal deformation sensitivity coefficient are introduced as weighting coefficients;

[0016] The reference aberration correction is obtained by summing the observation window correction component and the thermal deformation correction component. The observation window correction component is obtained by mapping the eigenvector of the vacuum chamber observation window deformation data through the observation window deformation sensitivity matrix. The thermal deformation correction component is obtained by mapping the effective aperture drift estimate through the thermal deformation sensitivity matrix.

[0017] The effective aperture drift estimate was calculated based on the thermal deformation data of the vacuum collimator lens barrel and support structure.

[0018] Furthermore, an internal constraint weight is introduced to constrain the reference aberration correction amount. The internal constraint weight is set according to a piecewise function. The piecewise function is divided into segments based on the threshold value of the internal temperature change of the optical system under test. The greater the internal temperature change of the optical system under test, the lower the internal constraint weight.

[0019] Furthermore, the reference optical performance data matching the current state includes the set of reference wavefront aberration coefficients matching the current state, the reference point spread function image matching the current state, and the reference modulation transfer function curve matching the current state.

[0020] Furthermore, a reference wavefront aberration distribution with the effective aperture of the vacuum collimator as the domain is obtained in advance, and the reference wavefront aberration distribution is modally decomposed within the effective aperture to form a reference wavefront aberration coefficient set.

[0021] Furthermore, the reference wavefront aberration coefficient set is reconstructed into a reference wavefront aberration distribution, and then a geometric transformation is performed in the phase domain and the coefficients are re-decomposed to obtain a reference wavefront aberration coefficient set that matches the current state.

[0022] Furthermore, in a benchmark test configuration with no optical system under test and a stable vacuum environment, reference optical performance data of the vacuum collimator was collected, and the reference optical performance data of the vacuum collimator was processed into reference optical performance data.

[0023] A vacuum light tube stabilization system with sealed protection includes:

[0024] The performance testing module is used to acquire reference optical performance data in advance;

[0025] The data acquisition module is used to synchronously acquire test data when the optical system under test is installed on the vacuum collimator and undergoes formal testing. The test data includes deformation data of the vacuum chamber observation window, thermal deformation data of the vacuum collimator lens barrel and support structure, and internal sensing data of the optical system under test. The module performs time alignment and noise reduction fusion on the test data to generate system status data.

[0026] The parameter calculation module calculates the pupil mapping transformation parameters based on system state data and reference optical performance data;

[0027] The parameter correction module is used to perform pupil plane coordinate alignment and aberration correction on the reference optical performance data based on the pupil mapping transformation parameters, so as to obtain reference optical performance data that matches the current state.

[0028] The result calculation module is used to perform difference operations or deconvolution operations on the collected observed optical performance data and the reference optical performance data that matches the current state to obtain the true optical performance data of the optical system under test.

[0029] Compared with the prior art, the technical effects and advantages of the vacuum light tube stabilization system and method with sealed protection of the present invention are as follows:

[0030] This invention first acquires reference optical performance data of a vacuum collimator in advance. During the testing of the optical system under test, it simultaneously collects multi-source data such as the deformation of the observation window of the vacuum chamber, the thermal deformation of the lens barrel and support structure, and the internal sensors of the system under test. After time alignment, noise reduction and fusion, system status data is generated. Based on this data and the reference optical performance data, pupil mapping transformation parameters are calculated. Then, based on these parameters, pupil plane coordinate alignment and aberration correction are performed on the reference optical performance data to obtain reference data matching the current test state. Finally, the true optical performance data of the optical system under test is separated through differential or deconvolution operations.

[0031] This invention effectively solves the problems of pupil mapping drift caused by the gas extraction and thermal stabilization processes in a vacuum environment, leading to inconsistencies between the pupil coordinate systems of the reference aberration and the observed aberration, and consequently, modal crosstalk, offset subtraction, and residual anomalies. It also overcomes the shortcomings of traditional methods that treat the reference aberration as a fixed value and ignore time-varying drift under vacuum conditions. Its advantages include adaptability to various optical performance testing scenarios, ensuring the accuracy of the performance data of the system under test, reducing misjudgments of the system's performance, lowering R&D and manufacturing costs, and providing traceable test results, thus improving the reliability of acceptance conclusions. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a vacuum optical tube stabilization system with sealed protection according to an embodiment of the present invention;

[0033] Figure 2This is a flowchart of a vacuum optical tube stabilization method with sealed protection according to an embodiment of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be described in detail, clearly, and completely below with reference to the accompanying drawings. It should be particularly noted that the specific embodiments described below are only for better illustrating and explaining the technical solutions of the present invention, and are intended to enable those skilled in the art to better understand and implement the present invention, and should not be construed as limiting the scope of protection of the present invention. Without departing from the spirit and substance of the present invention, those skilled in the art can modify, adjust, or make equivalent substitutions based on the content disclosed in the present invention, and these should all be considered within the scope of protection of the present invention.

[0035] Example 1:

[0036] Please see Figure 1 As shown, this embodiment discloses a vacuum tube stabilization system with sealed protection, including a performance testing module, a data acquisition module, a parameter calculation module, a parameter correction module, and a result calculation module. Each module is connected via wired and / or wireless means to achieve data transmission.

[0037] The performance testing module is used to acquire reference optical performance data in advance.

[0038] To ensure that the reference optical performance data represents the inherent response of the vacuum collimator under the same measurement conditions, the stability of the vacuum environment is assessed before calibration, and vacuum stability thresholds and temperature stability thresholds are set. The vacuum stability threshold is used to constrain the pressure fluctuation within the vacuum cavity during the assessment time window, while the temperature stability threshold is used to constrain the temperature drift of key measuring points on the vacuum collimator's barrel and support structure during the assessment time window. These thresholds ensure that the wavefront changes introduced by gas refractive index variations and thermally induced micro-deformations of the structure are below the allowable wavefront error budget during calibration, thus preventing the solidification of environmental non-steady-state errors into the reference optical performance data. For example, the vacuum stability threshold can be set to 5 Pa, and the assessment time window to 300 seconds; the temperature stability threshold can be set to 0.2 degrees Celsius, and the assessment time window to 300 seconds.

[0039] When both the vacuum stability threshold and the temperature stability threshold are met, a reference plane mirror is placed on the optical path at the output end of the vacuum collimator. This allows the parallel light output from the vacuum collimator to be reflected by the reference plane mirror and return along the original optical path to the interferometer receiver. The interferometer acquires the interference fringe sequence within a preset acquisition window and performs phase demodulation and phase unwrapping to obtain the reference wavefront aberration distribution defined by the effective aperture of the vacuum collimator. The preset acquisition window covers the main period of the pumping unit's micro-vibration and ensures that the average phase jitter of the interference fringe sequence is lower than the wavefront measurement noise budget, thereby reducing the contamination of the reference wavefront aberration distribution by transient vibrations. For example, a preset acquisition window of 2 seconds can be used. After obtaining the reference wavefront aberration distribution, mode decomposition is performed on the distribution within the effective aperture to form a set of reference wavefront aberration coefficients. Modal decomposition employs an orthogonal polynomial system to construct a modal representation of wavefront aberrations. The reference wavefront aberration distribution is equal to the linear superposition of each modal basis function and its corresponding modal coefficient. Each modal coefficient characterizes the aberration contribution of the vacuum collimator to that mode. The linear superposition relationship projects the spatial distribution of wavefront aberrations onto a set of orthogonal bases, enabling subsequent corrections to be quantitatively calculated in the modal dimension. The reference wavefront aberration coefficient set is obtained through least-squares fitting. The least-squares fitting aims to minimize the residual energy between the reference wavefront aberration distribution and the modally reconstructed wavefront, thus obtaining stable modal coefficient estimates even in the presence of noise. To avoid underfitting due to excessively low mode order or amplified noise due to excessively high mode order, an upper limit for mode order and a root mean square (RMS) threshold for residuals are introduced. The upper limit for mode order limits the number of modes, and the RMS threshold for residuals limits the residual wavefront error after fitting. The upper limit for mode order is the minimum one that meets the RMS threshold for residuals, thereby reducing noise coupling and subsequent computational complexity while ensuring accuracy.

[0040] After obtaining the reference wavefront aberration coefficient set, to ensure that the reference optical performance data covers point spread function measurement and modulation transfer function testing scenarios, a pupil plane complex amplitude distribution is constructed based on the reference wavefront aberration coefficient set, and the imaging link is derived. First, the reference wavefront aberration distribution is reconstructed from the reference wavefront aberration coefficient set and converted into a phase distribution. The optical path difference, expressed in length, is converted into a dimensionless phase delay, allowing it to participate in the complex field calculation. The aperture amplitude distribution is obtained by normalizing the light intensity envelope collected by the interferometer within the effective aperture. The aperture amplitude distribution represents the amplitude weight of the output beam from the vacuum collimator on the effective aperture, used to characterize the influence of aperture illumination non-uniformity on the imaging response. The pupil plane complex amplitude distribution is jointly determined by the aperture amplitude distribution and the phase distribution. The amplitude and phase are uniformly expressed as a complex field on the effective aperture, thus enabling the derivation of the image plane response through diffraction propagation. A Fourier transform is performed on the pupil plane complex amplitude distribution to obtain the image plane complex amplitude distribution. The reference point spread function image is defined as the intensity of the image plane complex amplitude distribution and its energy is normalized. The reference point spread function image represents the spatial distribution of imaging energy of a point target by a vacuum collimator on the image plane, used to characterize image broadening and sidelobe tailing. The optical transfer function (OPF) is calculated based on the OPF image, and its amplitude is normalized to obtain the reference modulation transfer function (MTF) curve. The OPF is the Fourier transform of the OPF image, and the MTF curve represents the ratio of the OPF amplitude to the zero-frequency amplitude, indicating the vacuum collimator's ability to transfer target contrast at different spatial frequencies.

[0041] The final reference optical performance data includes a set of reference wavefront aberration coefficients, a reference point spread function image, and a reference modulation transfer function curve. This allows the reference optical performance data to serve as a benchmark input for generating reference optical performance data that matches the current state in subsequent steps, and provides a unified benchmark for subtraction calculations of vacuum collimators in wavefront aberration measurement, point spread function measurement, and modulation transfer function testing scenarios.

[0042] The data acquisition module is used to synchronously acquire test data when the optical system under test is installed on the vacuum collimator and undergoes formal testing. The test data includes deformation data of the vacuum chamber observation window, thermal deformation data of the vacuum collimator lens barrel and support structure, and internal sensing data of the optical system under test. The module performs time alignment and noise reduction fusion on the test data to generate system status data.

[0043] Before and after the observation of the optical system under test, the system is started and continuously run until the observation is completed. A unified timestamp is written for each multi-source sensor reading, and a unified sampling sequence is established. To ensure that multi-source sensor readings can be fused under the same measurement state, a time alignment threshold is set. This threshold limits the timestamp deviation of different sensors under the same sampling sequence index to no more than a preset upper limit, ensuring that the interpolation error of the state variables is less than the allowable error budget for pupil mapping drift correction. For example, the time alignment threshold can be set to 5 milliseconds. When the timestamp deviation of a multi-source sensor reading exceeds the time alignment threshold, linear interpolation resampling is performed on that multi-source sensor reading to align it to the unified sampling sequence. Unit conversion is performed on the multi-source sensor readings, and the units are unified. The unit conversion uses meters, radians, degrees Celsius, Pascals, and meters per second squared as the target unit system to ensure that the physical quantities used in subsequent calculations of pupil mapping transformation parameters can directly participate in the same computational chain.

[0044] After unifying the timestamps and unit conversions, the multi-source sensor readings are denoised and anomaly removed to form stable state inputs. A denoising cutoff frequency is set to limit the cutoff frequency of the low-pass filter, retaining low-frequency changes related to vacuum chamber observation window deformation, vacuum collimator lens barrel and support structure thermal deformation, and platform attitude drift, while suppressing high-frequency noise before the micro-vibrations of the pumping unit solidify into equivalent geometric deviations within the observation integration time. For example, a denoising cutoff frequency of 20 Hz can be set. An anomaly removal threshold is set to determine whether the instantaneous jumps in the multi-source sensor readings exceed the physical reach range, ensuring that the removed data mainly comes from communication jitter, instantaneous saturation, or optical measurement lock-off rather than actual state changes. For example, an anomaly removal threshold of 3 times the standard deviation can be set. For multi-source sensor readings exceeding the anomaly removal threshold, median replacement is performed and a replacement mark is retained. The replacement mark is used to reduce the confidence weight of the corresponding data when calculating the pupil mapping transformation parameters later. Set an upper limit for the fusion weight. The upper limit of the fusion weight is used to limit the degree of dominance of any single sensor on the system state data, and prevent single-point drift or occasional anomalies from causing the system state data to deviate from the true state. For example, the upper limit of the fusion weight can be 0.6. When there are multiple redundant observations of the same state quantity, weighted fusion is used and the weight of the single source is pruned to not exceed the upper limit of the fusion weight.

[0045] At the state quantity construction level, the deformation data of the vacuum chamber observation window is obtained from the readings of the observation window deformation sensor. This data characterizes the impact of the surface shape changes caused by pressure difference and thermal stress during vacuuming and refilling on the optical path. To ensure a feasible acquisition path for the vacuum chamber observation window deformation data, a multi-point displacement measurement configuration is adopted. P non-contact displacement measurement points are arranged circumferentially and radially on the non-vacuum side outside the observation window, and signal transmission is achieved through sealed leads. The non-contact displacement measurement points are arranged away from the inside of the vacuum chamber to reduce the impact of the sealing protection structure on measurement stability. The displacement sequence obtained from the multi-point displacement measurement constitutes the surface shape height sampling value of the observation window. Modal fitting is performed on the surface shape height sampling value to reconstruct an equivalent representation of the surface shape height distribution of the observation window. The modal fitting uses a set of modal basis functions consistent with the reference wavefront aberration coefficient set and outputs a set of observation window surface shape modal coefficients. This ensures that the vacuum chamber observation window deformation data not only includes the change in the surface shape height distribution of the observation window over time but also has a dimensional interface consistent with the subsequent calculation of reference aberration corrections. To avoid under-constrained fitting due to too few measurement points, a lower limit on the number of measurement points is introduced to ensure that the number of fitting modes does not exceed the number of independent measurement equations and to leave redundancy to suppress noise. For example, when the number of fitting modes is 15, the lower limit on the number of measurement points can be 30.

[0046] To ensure that the deformation data of the vacuum chamber observation window directly reflects the impact of the window deformation on the optical path, and to obtain an estimated beam tilt angle from the beam pupil position monitor, the estimated beam tilt angle characterizes the change in the deflection angle of the principal ray of the parallel beam passing through the observation window relative to the reference reference. Changes in the observation window shape alter the transmission equivalent prism effect and refraction characteristics, causing a deflection of the principal ray. The estimated beam tilt angle corresponds to the quantified result of this deflection angle. The estimated beam tilt angle is obtained by calculating the centroid of the light spot center in the pupil position monitoring image acquired by the pupil position monitoring camera and converting it using the geometric calibration relationship of the monitoring optical path. The centroid calculation is performed by thresholding the light spot area and then calculating the gray-level weighted center. To suppress the bias of the centroid by background stray light and dark current, a centroid extraction threshold is introduced, retaining only pixels significantly higher than the background noise in the centroid calculation. This avoids the accumulation of weak background during integration, preventing center drift. For example, the centroid extraction threshold can be the background mean plus five times the background standard deviation. By simultaneously outputting the set of modal coefficients of the observation window surface shape and the estimated value of the beam tilt angle, the deformation data of the vacuum chamber observation window can characterize the degree of damage to the consistency of the measurement state caused by the observation window deformation on two levels: surface shape change and optical path deflection. This provides a traceable state input for subsequent pupil mapping transformation parameter solving and reference aberration correction calculation.

[0047] Thermal deformation data of the vacuum collimator's barrel and support structure are obtained from strain and temperature sensor readings. This data includes temperature changes and structural strain changes at key measuring points on the barrel. An estimated effective aperture drift is calculated to characterize the drift trend of the vacuum collimator's effective aperture position. To convert temperature and strain changes into an estimated effective aperture drift, thermal deformation and strain transformation coefficients are introduced. The estimated effective aperture drift equals the thermal deformation coefficient multiplied by the weighted average of the temperature changes at key measuring points on the barrel, plus the strain transformation coefficient multiplied by the weighted average of the structural strain changes. Within the linear approximation range of thermal expansion and elastic deformation, the effective aperture position drift can be driven by both temperature field changes and structural strain and can be approximated by a linear mapping. For example, the thermal deformation coefficient can be taken as 2 micrometers per degree Celsius, and the strain transformation coefficient can be taken as 0.5 micrometers per microstrain.

[0048] The incident parallel beam pupil plane offset data is obtained from the beam pupil plane position monitor readings. This data includes the translation of the beam center in the pupil plane coordinate system and an estimated beam tilt angle. The beam center translation is calculated from the intensity centroid of the pupil plane monitoring image. A centroid extraction threshold is set to suppress the bias of the centroid by background stray light, retaining only the effective spot area exceeding the background noise for centroid calculation. For example, the centroid extraction threshold can be the background mean plus 5 times the background standard deviation.

[0049] Platform attitude deviation data is obtained from readings of the platform attitude sensors. This data includes the deflection angle deviation and distance scaling variation relative to the expected attitude. The deflection angle deviation is determined by the difference between the readings of the high-precision angle sensor and the autocollimator, while the distance scaling variation is determined by the difference in readings of the displacement sensor. Platform repeatability error data is obtained from the platform attitude sensor readings and reciprocating positioning records. This data is obtained by calculating the root mean square (RMS) of the residual error from multiple positioning results of the same target attitude. The RMS of the residual error represents the repeatability capability of the platform under the influence of creep and hysteresis in a vacuum environment.

[0050] Micro-vibration data of the pumping unit is obtained from the vibration accelerometer readings. This data includes acceleration timing and corresponding spectral amplitudes. The spectral amplitudes are calculated using a discrete Fourier transform within a fixed-length time window. This time window balances frequency resolution and real-time performance, ensuring that the main pump frequency and its harmonics are distinguishable in the spectrum without introducing excessive delays; for example, a 2-second time window can be used. Internal sensor data of the optical system under test is obtained from the readings of its internal sensors. This data includes temperature changes, structural deformation changes, and internal alignment offsets. These data are used in subsequent steps to determine whether the variations in the observed optical performance data may originate from the optical system itself.

[0051] The system status data is a set of state variables organized according to a unified timestamp. The set of state variables includes the deformation data of the vacuum chamber observation window, the thermal deformation data of the vacuum collimator lens barrel and support structure, the pupil plane offset data of the incident parallel beam, the platform attitude deviation data, the platform repeatability error data, the micro-vibration data of the pumping unit, and the internal sensing data of the optical system under test.

[0052] The parameter calculation module calculates the pupil mapping transformation parameters based on system state data and reference optical performance data.

[0053] To ensure that the observed optical performance data and system status data can be correlated under the same measurement conditions, the consistency of the measurement triggering conditions is determined before starting the optical performance testing device, and trigger synchronization thresholds and exposure stabilization thresholds are set. The trigger synchronization threshold is used to limit the deviation between the acquisition trigger timestamp of the optical performance testing device and the unified timestamp of the system status data to no more than a preset upper limit. The exposure stabilization threshold is used to limit the fluctuation amplitude of the incident light flux within the observation integration time to no more than a preset upper limit. The trigger synchronization threshold and the exposure stabilization threshold ensure that the observation error introduced by trigger asynchrony and light flux drift is lower than the allowable error budget for pupil mapping drift correction. For example, the trigger synchronization threshold can be set to 5 milliseconds, and the exposure stabilization threshold can be set to 1%.

[0054] When both the trigger synchronization threshold and the exposure stabilization threshold are met, the optical performance testing device acquires observation optical performance data of the combined optical system according to a preset test sequence. The preset test sequence and the reference optical performance data maintain the same acquisition path and calibration link, introducing only the optical system under test into the output optical path of the vacuum collimator, ensuring that the observation results reflect the combined response of the optical system under test and the vacuum collimator. To cover wavefront aberration measurement, point spread function measurement, and modulation transfer function testing, the optical performance testing device adopts a unified observation data structure and generates corresponding data components in different test modes. In wavefront aberration measurement mode, the interferometer acquires the interference fringe sequence and performs phase demodulation and phase unrolling to obtain the combined wavefront aberration distribution. Then, within the effective aperture, modal decomposition of the combined wavefront aberration distribution is performed to obtain the set of combined wavefront aberration coefficients. The combined wavefront aberration distribution is equal to the linear superposition of each modal basis function and the corresponding combined wavefront aberration coefficient. The main spatial components of the combined system wavefront error are orthogonally projected using the set of combined wavefront aberration coefficients, allowing subsequent corrections to be performed consistently in the modal dimension. In the point spread function measurement mode, the imaging detector acquires a spot image on the image plane and performs dark field subtraction and flat field normalization to obtain the observation point spread function image. The observation point spread function image represents the spatial energy distribution of the point target after imaging by the combined system, and is used to characterize the resolution and scattering tail of the combined system. In the modulation transfer function test mode, the imaging detector acquires an image of the target and calculates the contrast transfer along a preset spatial frequency direction to obtain the observation modulation transfer function curve. The value of the observation modulation transfer function curve at each spatial frequency is the ratio of the image plane modulation degree to the object plane modulation degree. This ratio represents the contrast preservation capability of the combined system for details at that spatial frequency.

[0055] While collecting optical performance data from the combined optical system, the optical performance testing device simultaneously extracts system status data and establishes an observation association index. The observation association index is jointly determined by the observation data timestamp, the unified timestamp of the system status data, and the trigger synchronization threshold. When the difference between the observation data timestamp and the unified timestamp of the system status data does not exceed the trigger synchronization threshold, the index number of the system status data is written into the observation association index, ensuring that each frame of combined optical system performance data corresponds to one piece of system status data. To suppress the impact of micro-vibration and short-term flicker of the pumping unit on single-frame observations, an observation frame number and a consistency threshold are set. The observation frame number limits the number of frames continuously acquired in the same test mode, and the consistency threshold limits the difference between adjacent frame observation results to no more than a preset upper limit. Without significantly extending the test time, the observation frame number and consistency threshold are used to filter out unlocked frames, jitter-abnormal frames, and luminous flux-abnormal frames through multi-frame consistency screening. For example, the observation frame number can be 20, and the consistency threshold can be set to 30 nm for the root mean square of the wavefront aberration residual or 0.1 pixel for the centroid drift of the main peak of the point spread function. The optical performance testing device performs cumulative averaging on observation frames that meet the consistency threshold and retains the difference statistics before and after averaging. The difference statistics are used as input for observation confidence in subsequent steps.

[0056] The observed optical performance data includes one or more of the following: a set of combined wavefront aberration coefficients, a spread function image of the observation point, and an observed modulation transfer function curve. This allows the observed optical performance data to be used in subsequent steps, together with the system state data, as input for calculating the pupil mapping transformation parameters and separating the true optical performance data of the optical system under test.

[0057] Reference optical performance data is used to provide a set of reference wavefront aberration coefficients, a reference point spread function image, and a reference modulation transfer function curve for the vacuum collimator under benchmark testing configuration. System state data is used to characterize the deformation of the vacuum chamber observation window, thermal deformation of the vacuum collimator barrel and support structure, pupil plane shift of the incident parallel beam, platform attitude deviation, platform repeatability error, micro-vibration of the pumping unit, and comprehensive deviation of the internal state of the tested optical system at the time of formal testing. A homomorphic window length is set, which is used to select the state segment corresponding to the observed optical performance data on the time axis of the system state data, covering the average integration time of the observation frames and suppressing the influence of transient anomalies on the solution. For example, the homomorphic window length can be 10 seconds. The statistics of the system state data within the homomorphic window length are used as valid inputs for this step, thereby ensuring that the pupil mapping drift correction parameters are calculated for the same observation conditions and avoiding miscorrection caused by timing mismatch.

[0058] After determining the homomorphic window length, the pupil plane geometric drift is first calculated to address the modal crosstalk issue caused by the reference optical performance data and the observed optical performance data being in different pupil coordinate systems. The incident parallel beam pupil plane offset data and platform attitude deviation data are used together to construct the pupil plane geometric drift, which includes pupil plane coordinate translation, pupil plane rotation angle deviation, and pupil plane scaling ratio deviation. The pupil plane coordinate translation is determined by the average value of the incident parallel beam pupil plane offset data within the homomorphic window length; the pupil plane rotation angle deviation is determined by the average value of the deflection angle deviation in the platform attitude deviation data within the homomorphic window length; and the pupil plane scaling ratio deviation is determined by the average value of the distance scaling change in the platform attitude deviation data within the homomorphic window length. To suppress the contamination of mean estimation by discrete jumps caused by platform repetitive positioning errors, a geometric drift confidence threshold is introduced. This threshold limits the variance of the pupil-plane geometric drift within the homomorphic window length to a preset upper limit. The mean is only used as the geometric correction input when the drift statistics are stable; otherwise, the window is marked as a low-confidence window and its corresponding weight is reduced in subsequent solutions. For example, the geometric drift confidence threshold can be set to 0.05 mm² for the translation variance and 0.05 mm² for the rotation variance. Radius square, scaling variance The pupil plane coordinate translation, pupil plane rotation angle deviation, and pupil plane scaling ratio deviation calculated above represent the rigid body translation, in-plane rotation, and proportional scaling offset of the effective pupil coordinate system relative to the benchmark test configuration at the observation time. This offset causes the reference wavefront aberration coefficient set to suffer from non-orthogonal projection leakage of basis functions in the observation coordinate system, resulting in non-physical residuals in simple mode subtraction. Therefore, solving for the pupil plane geometric drift first can restore the mode alignment conditions from the source, reduce crosstalk, and improve the interpretability of the subtraction.

[0059] After obtaining the pupil plane geometric drift, to address the issue that the aberrations of the vacuum collimator itself no longer maintain reference consistency due to changes in the environment and structural state during the vacuuming cycle, a reference aberration correction is calculated and used to adaptively update the reference wavefront aberration coefficient set. The reference aberration correction is defined as a set of correction coefficients, which has the same modal dimension as the reference wavefront aberration coefficient set. This allows each modal coefficient in the reference wavefront aberration coefficient set to receive a corresponding incremental correction based on system state data. This incorporates the drift caused by the deformation of the vacuum chamber observation window and the thermal deformation of the vacuum collimator's barrel and support structure into the reference end, reducing non-physical residuals in subsequent subtraction calculations.

[0060] The reference aberration correction is obtained by summing the observation window correction component and the thermal deformation correction component. The observation window correction component is obtained by mapping the eigenvectors of the vacuum chamber observation window deformation data through the observation window deformation sensitivity matrix, while the thermal deformation correction component is obtained by mapping the effective aperture drift estimate through the thermal deformation sensitivity matrix. The observation window deformation sensitivity matrix is ​​used to convert the eigenvectors of the vacuum chamber observation window deformation data into a set of correction coefficients with the same modal dimension as the reference wavefront aberration coefficient set. The thermal deformation sensitivity matrix is ​​used to convert the effective aperture drift estimate into a set of correction coefficients with the same modal dimension as the reference wavefront aberration coefficient set, allowing the observation window correction component and the thermal deformation correction component to be directly added in the same dimension to form the reference aberration correction. The physical meaning of this mapping and summation is that, under small deformation conditions, the influence of changes in the refractive properties of the observation window and the thermally induced micro-deformation of the structure on the wavefront aberration can be superimposed along the modal dimension and reflected in the reference wavefront aberration coefficient set in the form of a set of correction coefficients.

[0061] The feature vector of the vacuum chamber observation window deformation data is constructed from the vacuum chamber observation window deformation data. The construction method involves preprocessing the surface height distribution of the observation window within the effective light-transmitting aperture of the observation window and performing modal projection. The preprocessing includes extracting surface height sampling values ​​within the effective light-transmitting aperture of the observation window and removing rigid body terms, so that the subsequent projection only reflects the influence component of the surface deformation on the optical path. Modal projection uses a set of modal basis functions consistent with the reference wavefront aberration coefficient set. The projection coefficients are calculated according to the inner product of the modal basis functions and the surface height sampling values ​​within the effective light-transmitting aperture of the observation window. The projection coefficients form the feature vector of the vacuum chamber observation window deformation data, so that the feature vector of the vacuum chamber observation window deformation data and the set of correction coefficients are in the same modal expression system, which facilitates mapping through the observation window deformation sensitivity matrix.

[0062] The effective aperture drift estimate is calculated based on the thermal deformation data of the vacuum collimator barrel and its supporting structure. The thermal deformation data includes the temperature changes and structural strain changes at key measuring points on the barrel. The effective aperture drift estimate is calculated using a preset conversion relationship between these temperature changes and structural strain changes, expressed in meters, to characterize the drift in effective aperture position caused by changes in thermal state. This allows the thermal deformation sensitivity matrix to map this drift into a set of modal dimension correction coefficients, forming a thermal deformation correction component.

[0063] The observation window deformation sensitivity matrix and the thermal deformation sensitivity matrix were obtained through pre-calibration, which was performed under a benchmark test configuration. During the pre-calibration process, multiple sets of eigenvectors and corresponding wavefront aberration coefficient increments of the vacuum chamber observation window deformation data were collected, along with multiple sets of effective aperture drift estimates and corresponding wavefront aberration coefficient increments. Based on these multiple sets of samples, the observation window deformation sensitivity matrix and the thermal deformation sensitivity matrix were fitted and solved. To control the norm of the fitting results and avoid excessive fluctuations due to sample noise, a sensitivity matrix regularization weight was introduced. This weight constrains the norm of the observation window deformation sensitivity matrix and the thermal deformation sensitivity matrix within the fitting target. The logic for setting the sensitivity matrix regularization weight is to limit the amplitude of the sensitivity matrix within an acceptable range for the fitting residuals. The sensitivity matrix regularization weight can be set to 0.1.

[0064] Through the above construction and calibration, the reference aberration correction amount can correspond one-to-one with the reference wavefront aberration coefficient set in the form of a set of correction coefficients according to mode. When the deformation data of the vacuum chamber observation window and the thermal deformation data of the vacuum collimator lens barrel and support structure change, the reference wavefront aberration coefficient set is updated, so that the subsequent subtraction operation is performed under the conditions of consistent pupil coordinate system and consistent state response.

[0065] After the reference aberration correction is calculated, the vibration equivalent correction is further calculated to address the issue of micro-vibrations of the pumping unit becoming fixed as equivalent imaging degradation during observation integration and multi-frame averaging. The vibration equivalent correction is determined by the micro-vibration data of the pumping unit. The root mean square of acceleration and the dominant frequency amplitude are calculated from the micro-vibration data within the homomorphic window length, and a vibration equivalent coefficient is introduced to convert the root mean square of acceleration into the image plane blur scale. The image plane blur scale is equal to the vibration equivalent coefficient multiplied by the root mean square of acceleration. During the observation integration time, the high-frequency micro-motions of the platform and optical components will cause time-averaged broadening of the point spread function image. The broadening scale is approximately proportional to the excitation intensity. The vibration equivalent coefficient establishes a quantitative correlation between the mechanical vibration intensity and the imaging degradation intensity. The vibration equivalence coefficient is calibrated by comparing the change in the full width at half maximum (FWHM) of the main peak in the point spread function image under different vibration levels. For example, when the root mean square of acceleration is 0.2 m / s², the FWHM of the main peak in the point spread function image increases by 0.1 pixels, so the vibration equivalence coefficient can be taken as 0.5 pixels per m / s². The vibration equivalence correction is used to introduce consistent degradation compensation to the reference point spread function image or reference modulation transfer function curve when adjusting the reference optical performance data in the next step, thereby avoiding misjudging the broadening caused by vibration as aberration or resolution reduction of the tested optical system.

[0066] To eliminate the interference of variations in the tested optical system itself on the correction of the vacuum collimator, an internal constraint weight is introduced during the result fusion stage. This internal constraint weight is determined by the internal sensing data of the tested optical system and affects the update magnitude of the reference aberration correction. When the internal sensing data of the tested optical system indicates a significant temperature change or internal alignment shift, the change in the observed optical performance data may include contributions from the tested optical system itself. In this case, the absorption ratio of the reference aberration correction to the observed changes should be reduced to prevent over-subtraction that would cause the true aberrations of the tested optical system to be canceled out. For example, the internal constraint weight can be set using a piecewise function: when the internal temperature change of the tested optical system does not exceed 1 degree Celsius, the internal constraint weight is 1; when the internal temperature change exceeds 1 degree Celsius but does not exceed 3 degrees Celsius, the internal constraint weight is 0.7; and when the internal temperature change exceeds 3 degrees Celsius, the internal constraint weight is 0.4. The internal constraint weight is a suppression factor for the update intensity of the reference aberration correction, ensuring that the correction process is preferentially interpreted as a component of vacuum collimator state drift only when the tested optical system is stable. This reduces the risk of misjudgment and improves the reliability of the acceptance conclusion. If observed optical performance data exists, the overall deviation trend is used for consistency verification. A deviation consistency threshold is set to determine whether the correction direction predicted by the system state data is consistent with the overall deviation trend of the observed optical performance data. This prevents sensitive system mismatch from causing the correction direction to be opposite and amplifying the residual. For example, the deviation consistency threshold can be set to a correlation coefficient of 0.6. If the correlation coefficient is less than the deviation consistency threshold, the correction output corresponding to the current homomorphic window length is marked as a low-confidence output and its usage weight is reduced in the next step.

[0067] The pupil mapping transformation parameters include pupil plane coordinate translation, pupil plane rotation angle deviation, pupil plane scaling ratio deviation, reference aberration correction, and vibration equivalent correction. The pupil plane coordinate translation, pupil plane rotation angle deviation, and pupil plane scaling ratio deviation are used to align the reference optical performance data with the pupil plane coordinates in the next step, thereby restoring the same pupil coordinate system conditions between the reference and observed optical performance data. The reference aberration correction is used to adaptively update the reference wavefront aberration coefficient set in the next step, thereby eliminating the influence of time-varying drift of the vacuum collimator's own aberrations on the subtraction results. The vibration equivalent correction is used to introduce broadening degradation compensation consistent with observations into the reference point spread function image and reference modulation transfer function curve in the next step, thereby reducing vibration solidification errors. The confidence flags corresponding to the internal constraint weights and deviation consistency thresholds are associated and stored with the pupil mapping transformation parameters, allowing the pupil mapping transformation parameters to be selectively used in subsequent steps and supporting traceable error analysis.

[0068] The parameter correction module is used to perform pupil plane coordinate alignment and aberration correction on the reference optical performance data based on the pupil mapping transformation parameters, so as to obtain reference optical performance data that matches the current state.

[0069] By transforming the pupil mapping parameters, the reference optical performance data is converted from the pupil coordinate system configured in the benchmark test to the pupil coordinate system consistent with the observed optical performance data. The time-varying aberrations and vibration degradation of the vacuum collimator under the current system state are incorporated into the reference optical performance data to obtain reference optical performance data that matches the current state. This ensures that subsequent difference operations or deconvolution operations meet the premise of the same coordinate system and the same state response, thereby reducing modal crosstalk and non-physical residuals.

[0070] To ensure the numerical stability and repeatability of pupil plane coordinate alignment, the reference wavefront aberration coefficient set is first reconstructed into a reference wavefront aberration distribution. Then, a geometric transformation is performed in the phase domain, and the coefficients are decomposed again into a reference wavefront aberration coefficient set matching the current state. Specifically, a reference pupil plane grid coordinate is established within the effective aperture, and a preset sampling grid is defined so that the grid sampling interval can cover the highest effective spatial frequency corresponding to the effective aperture, thereby avoiding resampling aliasing after geometric transformation. For example, when the effective aperture diameter is 200 mm, the preset sampling grid can be 512×512. Based on the reference pupil plane grid coordinate and the reference wavefront aberration coefficient set, the reference wavefront aberration distribution is calculated. The reference wavefront aberration distribution is equal to the weighted sum of the values ​​of each modal basis function at the reference pupil plane grid coordinate and the corresponding reference wavefront aberration coefficient. The modal coefficient set is restored to the wavefront optical path difference spatial distribution on the effective aperture so that geometric alignment can be performed at the same physical quantity level subsequently.

[0071] Subsequently, the observation pupil plane grid coordinates are constructed based on the pupil mapping transformation parameters. The observation pupil plane grid coordinates are obtained from the reference pupil plane grid coordinates through proportional scaling, in-plane rotation, and in-plane translation. The transformation relationship is that the observation pupil plane grid coordinates equal the scaling factor multiplied by the rotated result of the reference pupil plane grid coordinates, plus the translation vector. The scaling factor is determined by the pupil plane scaling ratio deviation, the rotation angle is determined by the pupil plane rotation angle deviation, and the translation vector is determined by the pupil plane coordinate translation amount. The pupil coordinate system configured for the benchmark test is mapped to the effective pupil coordinate system at the observation time, ensuring that the reference optical performance data and the observation optical performance data share the same pupil center, the same pupil aperture, and the same pupil plane angular reference in a geometric sense. Reverse resampling is performed on the reference wavefront aberration distribution based on the observation pupil plane grid coordinates. Bicubic interpolation is used for reverse resampling to reduce interpolation errors while maintaining phase continuity, resulting in the reference wavefront aberration distribution after pupil plane coordinate alignment.

[0072] After obtaining the reference wavefront aberration distribution after pupil plane coordinate alignment, a reference aberration correction is superimposed to achieve adaptive updating of the time-varying aberration state of the vacuum collimator itself. The reference aberration correction and the set of reference wavefront aberration coefficients have the same modal dimension; therefore, the reference aberration correction is first reconstructed into a reference aberration correction distribution, and then summed with the reference wavefront aberration distribution after pupil plane coordinate alignment. The reference aberration correction distribution is obtained by weighted summation of the corresponding correction coefficients of each modal basis function and the reference aberration correction. The wavefront drift caused by the deformation of the vacuum chamber observation window and the thermal deformation of the vacuum collimator's barrel and support structure is incorporated into the reference reference in the form of a spatial distribution of phase errors, thereby updating the reference reference from a static reference to an equivalent reference under the current system state. To avoid overcompensation under abnormal or low-confidence conditions, a correction limiting system is introduced. This system limits the peak and valley values ​​of the reference aberration correction distribution to a preset upper limit, ensuring that the correction amount does not exceed the upper limit of aberration drift that may occur in similar devices during a single-cycle vacuuming process, thus preventing correction divergence. For example, the correction limiting system can be set to 300 nanometers. When the peak and valley values ​​exceed the correction limiting system, the reference aberration correction distribution is proportionally clipped, and a clipping mark is output. After superposition, the aberration-corrected reference wavefront aberration distribution is obtained.

[0073] To enable subsequent differential operations in the modal dimension, the aberration-corrected reference wavefront aberration distribution needs to be re-decomposed to obtain a set of reference wavefront aberration coefficients matching the current state. Therefore, least-squares fitting is performed on the aberration-corrected reference wavefront aberration distribution within the effective aperture corresponding to the observation pupil grid coordinates, using a residual root mean square threshold as the fitting stopping condition. By setting the residual root mean square threshold, sufficient fitting accuracy of the modal representation to the aberration-corrected reference wavefront aberration distribution is ensured without excessively absorbing interpolation noise; for example, a residual root mean square threshold of 50 nanometers can be used. The resulting set of coefficients is the set of reference wavefront aberration coefficients matching the current state.

[0074] To ensure that the reference data generation path for point spread function (PSF) measurement and modulation transfer function (MTF) testing is consistent with the wavefront aberration, the reference PSF image and the reference MTF curve matching the current state are uniformly generated from the pupil plane complex amplitude distribution, instead of directly performing a geometric transformation on the reference PSF image as the main path. The pupil plane complex amplitude distribution is constructed based on the aberration-corrected reference wavefront aberration distribution and the aperture amplitude distribution. The aperture amplitude distribution is obtained by normalizing the light intensity envelope within the effective aperture acquired by the interferometer, and combined with the current aperture occlusion mask to obtain the current aperture transmission distribution. The wavefront phase distribution is obtained by converting the aberration-corrected reference wavefront aberration distribution according to the working wavelength. The pupil plane complex amplitude distribution is equal to the product of the aperture amplitude distribution and the current aperture transmission distribution, multiplied by the phase factor, which is the complex field distribution of the vacuum collimator on the effective aperture in the current system state. A Fourier transform is performed on the pupil plane complex amplitude distribution to obtain the image plane complex amplitude distribution. The spread function image of the reference point matching the current state is defined as the intensity of the image plane complex amplitude distribution and its energy is normalized, representing the equivalent imaging energy spatial distribution of the vacuum collimator on the point target under the current system state. Based on the spread function image of the reference point matching the current state, the optical transfer function is calculated and its amplitude is normalized to obtain the reference modulation transfer function curve matching the current state. The reference modulation transfer function curve matching the current state represents the vacuum collimator's ability to transfer contrast at different spatial frequencies under the current system state. The spatial frequency coordinates are calibrated using the same method as the observed optical performance data, converted from the image plane sampling interval and magnification calibration, to ensure comparability between the reference modulation transfer function curve and the observed modulation transfer function curve. For example, when the image plane sampling interval is 5 micrometers, the corresponding Nyquist spatial frequency is 100 per millimeter.

[0075] To incorporate the degradation introduced by the pumping unit's micro-vibrations into the reference end, the spread function image of the reference point matching the current state is subjected to degradation homogenization processing based on the vibration equivalent correction. A vibration blur kernel width is set, determined by the vibration equivalent correction and characterizing the equivalent broadening scale caused by the pumping unit's micro-vibrations during the observation integration process. This broadening is incorporated into the spread function image of the reference point matching the current state through convolution, ensuring that subsequent separation based on deconvolution operations does not misattribute vibration degradation to the measured optical system. For example, the vibration blur kernel width can be 0.2 pixels. To avoid boundary artifacts introduced by convolution, the introduced boundary expansion width should be no less than three times the vibration blur kernel width, so that the effective convolution area is not affected by boundary filling. For example, when the vibration blur kernel width is 0.2 pixels, the boundary expansion width can be 1 pixel. After convolution, the spread function image of the reference point matching the current state is renormalized, and the reference modulation transfer function curve matching the current state is updated synchronously to reflect the same vibration degradation level.

[0076] In computationally accelerated scenarios, image coordinate transformation can be used to approximate the reconstruction path of the pupil plane complex amplitude distribution, but the approximation must meet certain applicable ranges. These approximation ranges are constrained by small rotation thresholds, small scaling thresholds, and small pupil shift thresholds. By setting these thresholds, the main lobe morphology can be approximately preserved, and the impact of aberration distribution changes on the point spread function morphology can be ignored. Therefore, image domain geometric processing will not introduce considerable morphological errors. For example, the small rotation threshold can be 0.2 degrees, the small scaling threshold can be 0.2%, and the small pupil shift threshold can be 0.2% of the effective aperture diameter. When the approximation range is met, geometric uniformity processing is performed on the reference point spread function image, and an approximation marker is output. The approximation marker is stored in association with the result for traceability and acceptance testing.

[0077] The output of pupil plane coordinate alignment and aberration correction performed on the reference optical performance data based on the pupil mapping transformation parameters is the reference optical performance data matched to the current state. This matched reference optical performance data includes one or more of the following: a set of reference wavefront aberration coefficients matched to the current state, a reference point spread function image matched to the current state, and a reference modulation transfer function curve matched to the current state. It is stored in association with a preset sampling grid, a correction limiting system, a residual root mean square threshold, a vibration blur kernel width, a boundary expansion width, an approximate applicable range, a clipping mark, and an approximation mark. The matched reference optical performance data is used for subsequent difference or deconvolution operations with the observed optical performance data, ensuring that the subtraction process is completed under a consistent pupil coordinate system and a consistent vacuum collimator state response. This suppresses non-physical residuals and improves the reliability and traceability of the true optical performance data of the measured optical system.

[0078] The result calculation module is used to perform difference operations or deconvolution operations on the collected observed optical performance data and the reference optical performance data that matches the current state to obtain the true optical performance data of the optical system under test.

[0079] The reference optical performance data matching the current state includes a set of reference wavefront aberration coefficients matching the current state, a reference point spread function image matching the current state, and a reference modulation transfer function curve matching the current state. The observed optical performance data includes a combined set of wavefront aberration coefficients, an observed point spread function image, and an observed modulation transfer function curve. Assuming that the reference optical performance data matching the current state and the observed optical performance data are in the same pupil coordinate system and share the same vacuum collimator state response, the vacuum collimator contribution in the observed optical performance data is removed to obtain the true optical performance data of the tested optical system. This avoids misjudging pupil mapping drift and the time-varying aberrations of the vacuum collimator itself as performance degradation of the tested optical system in a vacuum environment.

[0080] To make differential or deconvolution operations feasible and reduce non-physical residuals, the subtraction conditions are quickly verified and the verification results are output before subtraction. The subtraction conditions include wavelength consistency, reference plane consistency, common pupil consistency, occlusion consistency, image plane scale consistency, and imaging condition consistency. To this end, a wavelength consistency threshold is set to constrain the difference between the working wavelengths of the reference and observation; a reference plane drift threshold is set to constrain the axial offset of the observed wavefront reference plane relative to the reference reference plane; a common pupil error threshold is set to constrain the residual pupil mapping error after pupil plane coordinate alignment; an occlusion consistency threshold is set to constrain the consistency of the effective aperture occlusion mask; and an image plane scale consistency threshold is set to constrain the consistency of the image plane sampling interval and magnification calibration. These thresholds ensure that the reference quantity and the observed quantity can be linearly superimposed or satisfy a cascaded system approximation relationship under the same physical definition, thus enabling the subtraction operation to succeed. For example, the wavelength consistency threshold can be set to 0.2 nm, the reference plane drift threshold to 5 μm, the con-pupil error threshold to 0.02, the occlusion consistency threshold to the ratio of the occlusion area difference to the effective aperture area not exceeding 0.5%, and the image plane scale consistency threshold to the relative error of the sampling interval not exceeding 0.2%. If any threshold is not met, the current observation sample is marked as a low-confidence sample and a low-confidence label is output, so that subsequent evaluations can remove this result or reduce its weight.

[0081] When the observed optical performance data includes a set of combined wavefront aberration coefficients and the subtraction condition is met, the true wavefront aberration coefficient set of the optical system under test is obtained by subtracting the wavefront aberration coefficients. Under the same reference plane and the same effective aperture mapping, the wavefront aberration of the combined system can be approximated as a linear superposition of the contribution from the vacuum collimator and the contribution from the optical system under test. Thus, the contribution from the optical system under test can be separated by subtracting each item. To suppress the influence of higher-order noise, a higher-order suppression weight is introduced to attenuate the higher-order mode coefficients. Since higher-order mode measurement noise accounts for a higher proportion, moderate attenuation is beneficial to improving robustness. For example, the higher-order suppression weight is 1 when the mode number is no more than 15, 0.6 when the mode number is greater than 15 but no more than 36, and 0.3 when the mode number is greater than 36.

[0082] When the observed optical performance data includes the observation point spread function image and the subtraction condition is met, optical transfer function domain separation is preferentially adopted, with point spread function deconvolution as an equivalent implementation. Both optical transfer function domain separation and point spread function deconvolution are existing cascaded system separation methods. Optical transfer function domain separation satisfies the multiplicative relationship under the incoherent imaging approximation, while point spread function deconvolution is used to invert the degradation kernel in the image domain. To improve numerical stability, a deconvolution stabilization factor is introduced to suppress noise amplification near zero in the frequency domain. For example, the deconvolution stabilization factor can be set to... To suppress deconvolution artifacts, a non-negativity constraint threshold is introduced to zero out and normalize negative pixels in the true point spread function image of the tested optical system; for example, the non-negativity constraint threshold can be set to 0. When the spatial invariance condition is not met or the observation signal-to-noise ratio is insufficient, the operation is converted to differential operation and a method label is output.

[0083] When the observed optical performance data includes the observed modulation transfer function (MTF) curve and the subtraction condition is met, the true MTF curve of the optical system under test is obtained by MTF normalization compensation. The true MTF curve of the optical system under test is equal to the observed MTF curve divided by the reference MTF curve matching the current state. Under the incoherent imaging approximation, the normalization relationship is approximately multiplicative of the combined system's optical transfer function, thus the contribution of the MTF to the optical system under test can be separated by the ratio. To avoid instability in high-frequency division, a lower limit for modulation transfer is introduced to trim the reference MTF curve matching the current state; for example, the lower limit can be 0.05. To eliminate the overall scaling caused by luminous flux drift, a low-frequency normalization reference is introduced to normalize the true MTF curve of the optical system under test; for example, the preset low-frequency bandwidth corresponding to the low-frequency normalization reference can be 0.05 per millimeter.

[0084] To verify that the separation results have not been over-subtracted or incorrectly subtracted, the actual optical performance data of the optical system under test is checked against the internal sensor data of the optical system under test, and a consistency conclusion is generated. The consistency check is an existing means of ensuring the reliability of the results. By setting a consistency comparison threshold, it is determined whether the optical results match the changes in the internal state. For example, the consistency comparison threshold can be set to a defocus mode difference of 60 nanometers and a centroid shift difference of 0.2 pixels. If the consistency comparison threshold is not met, an over-subtraction risk flag or a residual drift risk flag is output to support the retest decision in the acceptance process.

[0085] The true optical performance data of the optical system under test includes one or more of the following: the true wavefront aberration coefficient set of the optical system under test, the true point spread function image of the optical system under test, and the true modulation transfer function curve of the optical system under test. This enables the output results to achieve traceable reliability decisions in engineering acceptance and performance optimization.

[0086] Example 2:

[0087] Please see Figure 2 As shown, this embodiment provides a vacuum optical tube stabilization method with sealed protection, including:

[0088] Pre-acquire reference optical performance data;

[0089] When the optical system under test is installed in the vacuum collimator and undergoes formal testing, test data is collected simultaneously. The test data includes deformation data of the vacuum chamber observation window, thermal deformation data of the vacuum collimator lens barrel and support structure, and internal sensing data of the optical system under test. The test data is then time-aligned and denoised and fused to generate system status data.

[0090] Calculate pupil mapping transformation parameters based on system state data and reference optical performance data;

[0091] Based on the pupil mapping transformation parameters, pupil plane coordinate alignment and aberration correction are performed on the reference optical performance data to obtain reference optical performance data that matches the current state;

[0092] The collected observed optical performance data is compared with the reference optical performance data that matches the current state by performing differential or deconvolution operations to obtain the true optical performance data of the optical system under test.

[0093] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0094] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for stabilizing a vacuum optical tube with sealed protection, characterized in that, include: Pre-acquire reference optical performance data; When the optical system under test is installed in the vacuum collimator and undergoes formal testing, test data is collected simultaneously. The test data includes deformation data of the vacuum chamber observation window, thermal deformation data of the vacuum collimator lens barrel and support structure, and internal sensing data of the optical system under test. The test data is then time-aligned and denoised and fused to generate system status data. The pupil mapping transformation parameters are calculated based on system state data and reference optical performance data. The pupil mapping transformation parameters include pupil plane coordinate translation, pupil plane rotation angle deviation, pupil plane scaling ratio deviation, and reference aberration correction. The reference aberration correction is determined by the deformation data of the vacuum chamber observation window and the thermal deformation data of the vacuum collimator lens barrel and support structure. The reference aberration correction is constrained by the internal sensing data of the optical system under test to eliminate the interference of the changes of the optical system under test on the pupil mapping transformation parameters. The observation window deformation sensitivity matrix and the thermal deformation sensitivity matrix are introduced as weighting coefficients; The reference aberration correction is obtained by summing the observation window correction component and the thermal deformation correction component. The observation window correction component is obtained by mapping the eigenvector of the vacuum chamber observation window deformation data through the observation window deformation sensitivity matrix. The thermal deformation correction component is obtained by mapping the effective aperture drift estimate through the thermal deformation sensitivity matrix. The effective aperture drift estimate was calculated based on the thermal deformation data of the vacuum collimator barrel and its support structure. Based on the pupil mapping transformation parameters, pupil plane coordinate alignment and aberration correction are performed on the reference optical performance data to obtain reference optical performance data that matches the current state; The collected observed optical performance data is compared with the reference optical performance data that matches the current state by performing differential or deconvolution operations to obtain the true optical performance data of the optical system under test.

2. The method for stabilizing a vacuum optical tube with sealed protection according to claim 1, characterized in that, An internal constraint weight is introduced to constrain the reference aberration correction. The internal constraint weight is set according to a piecewise function. The piecewise function is divided into segments based on the threshold value of the internal temperature change of the optical system under test. The greater the internal temperature change of the optical system under test, the lower the internal constraint weight.

3. The method for stabilizing a vacuum optical tube with sealed protection according to claim 1, characterized in that, The reference optical performance data matching the current state includes the set of reference wavefront aberration coefficients matching the current state, the reference point spread function image matching the current state, and the reference modulation transfer function curve matching the current state.

4. The method for stabilizing a vacuum optical tube with sealed protection according to claim 3, characterized in that, A reference wavefront aberration distribution with the effective aperture of the vacuum collimator as the domain is obtained in advance. The reference wavefront aberration distribution is then decomposed into modes within the effective aperture to form a set of reference wavefront aberration coefficients.

5. The method for stabilizing a vacuum optical tube with sealed protection according to claim 4, characterized in that, The reference wavefront aberration coefficient set is reconstructed into a reference wavefront aberration distribution, and then a geometric transformation is performed in the phase domain and the aberration is re-decomposed to obtain a reference wavefront aberration coefficient set that matches the current state.

6. The method for stabilizing a vacuum optical tube with sealed protection according to claim 1, characterized in that, In a benchmark test configuration with no optical system under test and a stable vacuum environment, reference optical performance data of a vacuum collimator is collected and processed into reference optical performance data.

7. A vacuum optical tube stabilization system with sealed protection, used to implement the vacuum optical tube stabilization method with sealed protection as described in any one of claims 1-6, characterized in that, include: The performance testing module is used to acquire reference optical performance data in advance; The data acquisition module is used to synchronously acquire test data when the optical system under test is installed on the vacuum collimator and undergoes formal testing. The test data includes deformation data of the vacuum chamber observation window, thermal deformation data of the vacuum collimator lens barrel and support structure, and internal sensing data of the optical system under test. The module performs time alignment and noise reduction fusion on the test data to generate system status data. The parameter calculation module calculates the pupil mapping transformation parameters based on system state data and reference optical performance data; The parameter correction module is used to perform pupil plane coordinate alignment and aberration correction on the reference optical performance data based on the pupil mapping transformation parameters, so as to obtain reference optical performance data that matches the current state. The result calculation module is used to perform difference operations or deconvolution operations on the collected observed optical performance data and the reference optical performance data that matches the current state to obtain the true optical performance data of the optical system under test.

Images