Invention patent of variable shear rate wavefront sensor based on random coding hybrid grating (2)

The present invention realizes changing the shear rate through the transmission device as follows:

During the measurement process, the rotating part is adjusted clockwise or counterclockwise along the optical axis direction, and then the grating holder is driven by the screw to move linearly along the optical axis direction within the specified distance range inside the sensor, thereby driving the distance between the random coding hybrid grating and the CCD to change continuously; the wavefront to be measured diffracts after passing through the random coding hybrid grating to generate four sub-wavefronts with tilts, and a four-wavefront lateral shear interference pattern is generated on the image plane and collected by the CCD. Since the shear rate of the interference pattern is determined by the distance between the random coding hybrid grating and the CCD, the sensor can realize continuous adjustment of the lateral shear interference shear rate.

The shear rate β of the sensor of the present invention is: where D is the incident beam aperture, λ is the incident light wavelength, d is the grating pitch, and H is the phase grating thickness; L is the distance between the random coding hybrid grating and the CCD, and its adjustment range is 0.8mm-11mm. Since a certain distance is required between the grating and the CCD to protect the CCD, a minimum distance of 0.8mm is required, and the corresponding shear rate β range is 0.0155-0.1937.

The present invention needs to use different shear rates for wavefronts with different distortion amounts to balance accuracy and sensitivity. For wavefronts with larger PV (Peak-to-Valley) values, a small shear rate is required to ensure accuracy. For wavefronts with smaller PV values, a large shear rate can be appropriately selected to increase sensitivity. Compared with a system with an unchangeable shear rate, a single shear rate cannot be applied to multiple types of wavefronts, while a wavefront sensor with a variable shear rate can be used for accurate wavefront measurement of more objects, and the adjustment device is simple and flexible.

The beneficial effects of the present invention are as follows:

The variable shear rate wavefront sensor based on the random coding hybrid grating provided by the present invention can accurately adjust the distance between the random coding hybrid grating and the CCD by adjusting the transmission parts on the wavefront sensor. On the basis of the original random coding grating measurement of the distorted wavefront, the shear rate of the four-wavefront lateral shearing interference pattern can be continuously adjusted. The wavefront sensor has high integration, simple structure, convenient adjustment, flexible measurement, high precision and enhanced universality.

The grating Fraunhofer diffraction has only four strict diffraction orders, so there is no need for an order selection window, and there is no Talbot effect on the observation surface. The distance between the grating and the CCD directly determines the shear rate. The sensor has high integration, simple structure and convenient adjustment. By adjusting the random coding hybrid grating to move forward and backward to obtain different shear rates, the four-wavefront lateral shearing interference is realized, and the transient wavefront can be detected in real time, and the biological cells can be quantitatively phase detected. The continuously adjustable shear amount enables the wavefront sensor to select the best shear rate for a specific wavefront to be measured, and the measurement is flexible, the measurement accuracy is high, and the universality is enhanced.

Excerpted from: Jingnaike Optoelectronics Invention Patent