Research On Imaging Method Of Wavefront Coding System Based On Cubic Phase Plate Rotation

Wavefront coding imaging technology is a combination of optical encoding and image decoding.By adding a phase plate to the pupil plane of an existing optical imaging system,the optical transfer function and the point spread function of the optical system can be made larger in the range of focal depth Not sensitive to defocus within,to avoid the loss of some spatial frequencies.Since the distribution of the point spread function of the wavefront coding system of the third phase plate approximates the isosceles triangle,the morphology and distribution are basically the same under different defocusing magnitudes.Thus,the same restoration algorithm can be used to reconstruct the middle-level blurred images with different defocus positions.However,due to the boundary effect of the main decoding algorithm,the signal-to-noise ratio of the restored image is reduced and the image is unnatural.The details are lost more seriously.In this paper,three non-rotationally symmetrical phase plate and image fusion algorithms are studied.In view of the existing problems of the reconstructed image,the corresponding solutions are proposed,so as to effectively improve the signal-noise ratio of the image and improve the image quality.In this paper,the method based on the rotation of the phase plate and image fusion is discussed base on the theoretical analysis of the wavefront coding system and the phase function expression of the cubic phase plate.According to the theoretical analysis of the wave-front coding system and the phase function expression of the cubic phase plate,this paper analyzed and utilized the feature that the phase function expression would be invariant in the new coordinate system when the phase plate rotates at different angles around the z-axis.First of all,this paper deduces the change of pupil function of three-phase plate without eccentric rotation in the system,and analyzes the influence of the position of phase plate on the system's point spread function and imaging.It is concluded that when the three phase plates rotate only about the pupil axis,the distribution and shape of the point spread function will also be rotated,and the system modulation transfer function will also rotate accordingly,and the reconstructed image also appears fuzzy in different directions.Subsequently,an improved Laplacian pyramid image fusion algorithm and Fourier transform spectral fusion algorithm are proposed.The different reconstructed images are decomposed into different spatial frequency bands respectively.The fusion criterion of average gradient and regional energy is adopted for the features and details of different frequency bands of different decomposition layers to highlight the fusion of different reconstructed images in different frequency bands and details.In the frequency domain,according to different reconstructed images with different spectral amplitudes,the spectral amplitudes are compared and the maximum spectral fusion rules are retained for fusion.Finally,the experiment platform was constructed based on the wavefront coded infrared imaging lens and thermal imager in laboratory,and the actual experiment was carried out.This imaging method can make the system within the operating temperature range from the image quality of the ambient temperature changes,but also increase the amount of information in the image and improve the image signal to noise ratio.Subjective and objective evaluation methods were used to compare the imaging methods proposed by traditional optics and wavefront coding systems and papers to get the results we expected.