Invention patent for variable shear rate wavefront sensor based on random coded hybrid grating （1）

Technical field

The present invention relates to a variable shear rate wavefront sensor based on random coded hybrid grating, mainly involving the field of optical wavefront detection and quantitative phase detection.

Background technology

The lateral shearing technology is based on the principle of common-path shearing interference. It does not require an additional reference optical path, has strong anti-interference ability, good seismic isolation effect, and high stability. It can achieve high-precision detection in a general detection environment and is suitable for the measurement of optical system aberrations, spherical and aspherical surface shapes, and biological cell phase information.

The traditional lateral shearing interferometer needs to collect two strictly orthogonal lateral shearing interference patterns to reconstruct the original wavefront. The optical path structure involved is relatively complex, and the adjustment process is cumbersome, which is not conducive to instrumentation and universal detection. The four-wavefront lateral shearing interferometer can use a single image to obtain shearing interference patterns in two orthogonal directions, which can greatly simplify the optical path structure, reduce the instrument size, greatly reduce the difficulty of measurement operation, and facilitate integration and instrumentation. Due to the common path characteristics of the four wavefronts, the interference fringes are extremely stable, which is more conducive to detection in a general environment. The key and difficulty of the four-wavefront lateral shearing interferometer lies in the design of the grating that produces four sub-wavefronts.

The existing four-wavefront lateral shearing interferometers include the cross-grating lateral shearing interferometer, the improved Hartmann template lateral shearing interferometer (MHM) and the random coded hybrid grating. The cross-grating's spectroscopic effect will produce multiple diffraction orders in two orthogonal directions for the wavefront to be measured, but the order selection window is required to select the 1st order diffraction light. It can be used for high-precision wavefront detection, but the instrument adjustment mechanism has extremely high precision requirements and the detection operation is complicated. On the basis of the cross-grating, the MHM introduces a phase grating to suppress most of the irrelevant orders. The advantage is that there is no need for an order selection window, the structure is compact, and the adjustment is convenient. However, since the remaining ±5 and ±7 orders will still interfere with the four-wavefront interference, and there is a Talbot effect when adjusting the observation surface to set the shear rate, only a relatively ideal four-wavefront interference can be obtained at a specific position, and the shear rate cannot be fully set arbitrarily. The randomly coded hybrid grating based on light flux constraint uses an amplitude grating and a phase grating for phase adjustment. It does not require an order selection window. The diffracted light contains only four identical sub-waves, which can be used for four-wavefront lateral shearing interference. For devices where the distance between the randomly coded grating and the CCD cannot be adjusted, the diversity of its detection objects is limited. Therefore, it is necessary to propose a wavefront sensor device that can achieve arbitrary shear rates for more universal high-precision wavefront detection.

Invention Content

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a variable shear rate wavefront sensor based on a randomly coded hybrid grating.

A variable shear rate wavefront sensor based on a random coded hybrid grating; a transmission device capable of realizing a variable shear rate is designed based on an existing sensor; specifically, it includes a transmission device, a random coded hybrid grating, a matching fixture, and a CCD; the transmission device includes a rotating part, a grating mounting part, and a screw, and the inner ring of the rotating part is provided with a spiral line with a thread; the upper part of the matching fixture is arranged between the rotating part and the grating mounting part, and the lower part is used to fix the entire transmission device to the CCD; a long strip groove is opened on the inner wall of the rotating part, and a threaded hole is opened on the outer wall of the grating mounting part, and the screw fixes the rotating part and the matching fixture together, and the other end of the screw is arranged in the groove of the inner wall of the rotating part; the random coded hybrid grating is arranged at one end of the grating mounting part close to the CCD.

Excerpted from: Jingnaike Optoelectronics Invention Patent