Wavefront Coding Technology Research Articles

Design of online damage images detection system for large-aperture mirrors of high power laser facility based on wavefront coding technology

The laser transport system of the high power laser facility is mainly composed of large-aperture laser transport mirrors (TMs). Obtaining the high-resolution online damage images during the operation, which is of great significance for operating safely of the mirrors and the facility. Based on wavefront coding, pan-tilt scanning and image stitching technologies, an online laser-damage images detection system is designed, and it can achieve high-precision detection of surface characteristics of large-aperture laser transport mirrors. The preliminary simulation proves that the system can solve the depth of field matching problem caused by pan-tilt tilt imaging and achieve higher resolution.

The suppression of aero-optical aberration of conformal dome by wavefront coding

The aero-optical aberration of conformal dome (AOACD) is difficult to correct and would cause serious image degradation. Wavefront coding (WFC) image technique includes the optics and the digital processing steps to achieve the final high-quality images and it can be used to control the optical aberrations. In this paper, a strategy for correcting the AOACD is presented based on WFC technology. The thermal-structure simulation results of the conformal dome are obtained by using ANSYS. The performance degradation of the conformal optical system affected by aero-optical effect is analyzed by using CODEV. Then, a typical generalized cubic phase mask is inserted into the pupil plane of the conformal optical system to suppress its aero-optical aberration. The simulation results show that (1) the image degradation is mainly caused by the refractive index distribution of the conformal dome rather than its deformation; (2) the utilization of WFC technology could suppress AOACD effectively. This work is of consequence in conformal optics and aero-optics.

The dynamic aberrations suppression of conformal optical system by wavefront coding

In conformal optics, the dynamic aberrations of conformal optical system (DACOS) are difficult to correct and would cause serious image degradation. In this work, we propose a method based on wavefront coding (WFC) technology to suppress the DACOS. A conformal dome with highly significant dynamic aberrations (about ±8λ) is established and its aberration characteristics are investigated using Zernike aberration theory. A simple cubic phase mask (CPM) is inserted in its pupil plane to suppress residual dynamic aberrations after preliminary aberration correction. The simulation results show that, the utilization of WFC technology could not only suppress the DACOS efficiently, but also reduce physical imaging elements, which could in turn relax the alignment and fabrication tolerances. This work is of consequence in conformal optical systems design.

Imaging and image restoration of an on-axis three-mirror Cassegrain system with wavefront coding technology.

Wavefront coding (WFC) technology is adopted in the space optical system to resolve the problem of defocus caused by temperature difference or vibration of satellite motion. According to the theory of WFC, we calculate and optimize the phase mask parameter of the cubic phase mask plate, which is used in an on-axis three-mirror Cassegrain (TMC) telescope system. The simulation analysis and the experimental results indicate that the defocused modulation transfer function curves and the corresponding blurred images have a perfect consistency in the range of 10 times the depth of focus (DOF) of the original TMC system. After digital image processing by a Wiener filter, the spatial resolution of the restored images is up to 57.14 line pairs/mm. The results demonstrate that the WFC technology in the TMC system has superior performance in extending the DOF and less sensitivity to defocus, which has great value in resolving the problem of defocus in the space optical system.

The alignment and imaging experiment of a telescope with wavefront coding technology

Wavefront coding (WFC) is kind of computational imaging technique that controls misfocus and misfocus-related aberrations of optical systems by appending a specially designed phase distribution to the pupil function. This technology has been applied in many fields to increase the performance or/and reduce the cost of imaging systems. The application of WFC technology on an off-axis three-mirror anastigmatic (TMA) system has been proposed in our previous work. In this letter, we describe the alignment, the imaging experiment and image restoration of an actual TMA system with WFC technology. 2014 中文 Optics Letters.

Experimental study of an off-axis three mirror anastigmatic system with wavefront coding technology

Wavefront coding (WFC) is a kind of computational imaging technique that controls defocus and defocus related aberrations of optical systems by introducing a specially designed phase distribution to the pupil function. This technology has been applied in many imaging systems to improve performance and/or reduce cost. The application of WFC technology in an off-axis three mirror anastigmatic (TMA) system has been proposed, and the design and optimization of optics, the restoration of degraded images, and the manufacturing of wavefront coded elements have been researched in our previous work. In this paper, we describe the alignment, the imaging experiment, and the image restoration of the off-axis TMA system with WFC technology. The ideal wavefront map is set to be the system error of the interferometer to simplify the assembly, and the coefficients of certain Zernike polynomials are monitored to verify the result in the alignment process. A pinhole of 20 μm diameter and the third plate of WT1005-62 resolution patterns are selected as the targets in the imaging experiment. The comparison of the tail lengths of point spread functions is represented to show the invariance of the image quality in the extended depth of focus. The structure similarity is applied to estimate the relationship among the captured images with varying defocus. We conclude that the experiment results agree with the earlier theoretical analysis.

Design of an off-axis three-mirror anastigmatic optical system with wavefront coding technology

Wavefront coding (WFC) technology can extend the depth of focus of an optical system, which makes the application of this technology to space cameras extremely attractive. This paper introduces the application of wavefront coding to three-mirror anastigmatic optical systems. A transition model is established, in which the secondary mirror is regarded as the wavefront coding element and redesigned according to mathematical calculation. A comparison of modulation transfer function (MTF) behavior between the traditional system and the innovative system with wavefront coding technology is provided. The MTF behavior of both on-axis and off-axis field-of-view points remains the same in spite of the extended depth of focus. It is also observed that the system becomes very insensitive to aberration related to defocus through WFC technology. Errors in optical design and its improvement are discussed. The linear transition model is proven to be an acceptable one. Finally, an extension factor for the depth of focus is defined, and its effect is presented graphically.