ABSTRACT
Clarifying the aberrations arising from freeform surfaces is of great significance for maximizing the potential of freeform surfaces in the design of optical systems. However, the current precision in calculating aberration contribution of freeform surface terms for non-zero field of view is insufficient, impeding the development of freeform imaging systems with larger field of view. This paper proposes a high-precision analysis of aberration contribution of freeform surface terms based on nodal aberration theory, particularly for non-zero field points. Accurate calculation formulas of aberrations generated by Zernike terms on freeform surface are presented. Design examples illustrate that the calculation error of the provided formulas is 78% less than that of conventional theoretical values. Building upon high-precision analysis, we propose an optimization method for off-axis freeform surface systems and illustrate its effectiveness through the optimization of an off-axis three-mirror system. This research extends the applicability of nodal aberration theory in aberration analysis, offering valuable insights for the optimal design and alignment of optical freeform systems.
ABSTRACT
In this paper, a design method of diffraction structure based on metasurface is proposed for light splitting and focusing simultaneously. In the method, firstly, the light field calculation model of the proposed structure is established based on Fresnel diffraction and the transmittance function is calculated. Then, the model structural parameter selection mechanism is determined, and the spectrum resolution equation of the structure is derived. Simulation results indicate that the proposed method can offer a broader working bandwidth and enhanced higher resolution compared to off-axis meta-lens. Moreover, this proposed method can be deployed in high-resolution, wide-band ultra-compact spectrometer systems potentially.
ABSTRACT
Herein, we propose a super-oscillation optical field foveated local super-resolution imaging method. Firstly, the post-diffraction integral equation of the foveated modulation device is constructed, the objective function and constraints are established, and the structural parameters of the amplitude modulation device are optimally solved by using genetic algorithm. Secondly, the solved data have been input into the software for point diffusion function analysis. We have studied the super-resolution performance of different ring band amplitude types, and find the 8-ring 0-1 amplitude type has the best super-resolution performance. Finally, the principle experimental device is built according to the simulation parameters, and the super-oscillatory device parameters is loaded onto the amplitude type spatial light modulator for the principle experiments, in which the super-oscillation foveated local super-resolution imaging system is able to perform high image contrast imaging in the whole field of view and super-resolution imaging in the foveated field of view area. As a result, this method achieves the 1.25 times super-resolution magnification in the foveated field of view area, which realizes the super-resolutio n imaging of local field while keeping the resolution of other fields unchanged. Experiments verify the feasibility and effectiveness of our system.
ABSTRACT
Conventional imaging methods will cause a serious distortion for large object plane imaging with a limited object-to-sensor distance (OTSD). Here, we propose an imaging method based on the combination of microlens arrays and aperture arrays to realize the low-distortion, large object plane imaging range (OPIR) and compact design imaging at a close OTSD. Two-stage microlens arrays are utilized to reduce the distance between the object and sensor with low distortion, and two-stage aperture arrays are sandwiched between the microlens arrays to eliminate stray light between different microlenses. The theoretical analysis and simulation results indicate that our proposed method can realize low-distortion imaging with a large OPIR when the OTSD is seriously limited. This imaging method can be used widely in small-size optical devices where the OTSD is extremely limited.
ABSTRACT
In this paper, an infrared target adaptive detection method based on the receptive field and lateral inhibition (LI) of the human visual system is proposed. In the proposed method, the direction parameters of a Gabor filter are adaptively determined according to the gradient direction, so that edges in the image can be detected without manual intervention. Meanwhile, background prediction based on LI is used for regulating the gray value in the image to achieve background suppression and target enhancement. Experimental results indicate that the proposed method can extract both the small target and the area target from a complex background, and has satisfactory target detection ability.
