研究目的
To propose a practical and accurate correction method for the misalignment removal of free-form surfaces in non-null interferometric testing systems based on computer modeling.
研究成果
The proposed method effectively corrects misalignments in free-form surface testing, achieving high accuracy with PV value errors better than 1/30λ compared to profilometer results. It avoids mechanical adjustments in the actual setup by relying on computer modeling, making it practical and versatile for free-form surfaces with sophisticated degrees of freedom.
研究不足
The method depends on the accuracy of system modeling, including parameters like refractive index, thickness, and radius of curvature of components. It may be affected by modeling errors and requires a high-precision computer model. The correction accuracy for rotation error is limited by the discernibility of Moire fringes, and for surfaces with great departure, irregular subaperture stitching might be needed in the future.
1：Experimental Design and Method Selection:
The method involves computer modeling of the interferometric configuration, with misalignment aberrations (axial location error, rotation error, non-axial attitude error) corrected step by step using specific techniques such as continuous axial curve matching, Moire-fringe technology, and coordinate conversion for valid calculation areas.
2：Sample Selection and Data Sources:
A biconic surface with specific parameters (e.g., Rx=242 mm, Ry=238 mm, kx=-
3：2, ky=-8) is used as the test sample. Interferograms are collected using a CCD detector. List of Experimental Equipment and Materials:
Includes a non-null interferometric testing system based on Twyman-Green structure, beam expander, beam splitter, reference mirror with PZT, partial null lens (PNL), free-form surface under test, displacement measuring interferometer (DMI), and CCD detector.
4：Experimental Procedures and Operational Workflow:
The procedure involves setting up the theoretical model, moving the test surface, collecting interferograms, correcting axial location error via curve matching, correcting rotation error using Moire fringes, correcting non-axial attitude error via VCA and conversion, and reconstructing figure error using the ROR algorithm.
5：Data Analysis Methods:
Zernike polynomials are used for fitting wavefronts, phase-shifting algorithms for demodulation, and reverse optimizing reconstruction (ROR) for figure error calculation.
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