5 results about "Point diffraction interferometer" patented technology

This invention discloses a system error calibration method for a phase-shifting point diffraction interferometer based on mask rotation. The proposed method requires a simple hardware structure and, compared to traditional point diffraction interferometer calibration methods, does not add any additional optical modules, enabling sub-nanometer-level system error calibration. The proposed method precisely controls the mask rotation angle by rotating alignment marks, making the diffraction error caused by pinhole diffraction a variable before and after rotation. Furthermore, it utilizes the orthogonality and parity-even symmetry properties of Zernike polynomials in the unit circle domain to calibrate the pinhole diffraction error. Compared to conventional mask replacement methods and rotating the optical system under test methods, this method further reduces system error; and compared to methods that involve multiple pinhole rotations and averaging, it reduces operational complexity.

The invention provides a point diffraction interferometer, comprising: a laser (100) suitable for generating collimated laser; the frequency shifting assembly (200) comprises a first acousto-optic frequency shifter (201) which is suitable for enabling the collimated laser to generate diffraction and obtaining two beams of first sub-laser with a frequency difference; the second acousto-optic frequency shifter (202) is matched with the first acousto-optic frequency shifter (201), so that the two beams of first sub-laser with the frequency difference are diffracted respectively, and two beams of second sub-laser which are parallel and have the frequency difference are obtained; a diffraction assembly (300) configured to diffract the two beams of second sub-laser to generate reference light with a spherical wave front and measurement light with the spherical wave front; wherein the measuring light is reflected by the to-be-measured element after entering the to-be-measured element, and reflected light carrying surface shape information of the to-be-measured element (600) is obtained; and the interference assembly (400) is matched with the diffraction assembly (300) and is suitable for enabling the reference light and the reflected light to generate interference to obtain an interference signal, and the interference signal is used for determining the surface shape information of the element to be detected.

This application relates to the field of wavefront detection technology, specifically to a four-wave phase-shifting point diffraction interferometer for wavefront detection, aiming to solve the problems of limited performance and susceptibility to environmental interference in dynamic scenarios of traditional point diffraction interferometers. The point diffraction interferometer includes: a beam splitting module, a test arm modulation module, a reference arm modulation module, a beam combining interferometer module, and a detection and restoration module. The test arm modulation module is sequentially equipped with a first focusing lens, a plane mirror, a beam splitter grating, and a first collimating lens. The reference arm modulation module is sequentially equipped with a second focusing lens, a plane mirror, a filter, a second collimating lens, and a partitioned fixed phase modulation element. The beam combining interferometer module combines the beams from the test arm and the reference arm. The detection and restoration module includes a photodetector and a data processing unit for acquiring the wavefront phase of the incident distorted wavefront. This application's four-wave phase-shifting point diffraction interferometer for wavefront detection significantly improves the performance and stability of wavefront detection.

The invention discloses a phase shift point diffraction interferometer system error calibration method based on mask rotation. According to the point diffraction interferometer system error calibration method provided by the invention, the required hardware structure is simple, and compared with a traditional point diffraction interferometer calibration method, no additional optical module is added, and sub-nano-scale system error calibration can be realized. According to the phase shift point diffraction interferometer system error calibration method provided by the invention, the rotation angle of the mask is accurately controlled by rotating the alignment mark, so that the diffraction error caused by pinhole diffraction becomes a variable before and after rotation, and the pinhole diffraction error is calibrated by using the orthogonal property and odd-even symmetry property of a Zernike polynomial in a unit circle domain; compared with a conventional mask replacement method and a method for rotating the optical system to be measured, the system error is further reduced; compared with a method of averaging by rotating a pinhole for multiple times, the operation complexity is reduced.

This invention discloses a method and system for precise alignment of a point diffraction interferometer under test mirror based on image information. The method involves moving the under test mirror to achieve focusing on the reflecting mirror; and determining the average light intensity I of the area occupied by the point diffraction source's emission end. m The average light intensity value I of b pixels occupied by the light spot reflected by the mirror under test m '; Determine the amount of light intensity that needs to be increased for the light spot on the test mirror, so that the increased light intensity I m '≥I m ; Calculate the distance d between the reflected light spot of the enhanced mirror and the centroid of the point diffraction source's exit end. x and d y The relationship N between the number of pulses sent by the motor drive control system and the distance is obtained. x and N y According to N x and N y The system drives a stepper motor to operate; it calculates the distance between the converged light spot of the test mirror and the exit end of the point diffraction source based on the acquired image, and completes alignment when they coincide. Based on the acquired image information, it achieves precise alignment between the reflected light spot of the test mirror and the exit end of the point diffraction source under visualization conditions, reducing translation, tilt, and defocus errors introduced by misalignment.