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Most of the current ultraviolet (UV) optical lenses have narrow working band, which results in the decrease of their application adaptability. It is becasue of the fewer lens materials for UV lens design, and further it is difficult for the correction of UV color aberration. By applying the optical structure of negative-positive lenses overlapping distribution together with quasi-double Gaussian symmetry, as well as utilizing the wide spectral transmittance of fused quartz material and calcium fluoride material, an optical system with wide ultraviolet spectrum was designed, which also had the advantages of large relative aperture, wide field of view and high resolution. Its working wavelength was from 240 nm to 360 nm and the UV working bandwidth reached to 120 nm. All of the lenses in the designed UV optical system were spherical lenses, which could be fabricated and measured easily. Taking the central wavelength of 300 nm as the reference wavelength, the maximum lateral color aberration of the designed UV optical system was less than one pixel size over the full field of view. In the cut-off frequency of 50 lp·mm−1, the modulation transfer function (MTF) value was better than 0.4. The root mean square (RMS) value of image spot diagram in each field was better than 10 μm. The design results show that the designed UV optical system with wide UV spectrum has good imaging quality, high resolution and small color aberration, which satisfies the design requirements.

We introduce a partially coherent beam, called a multi-hyperbolic sine-correlated (MHSC) beam, by employing a multi-hyperbolic sine function to modulate the spectral degree of coherence. Based on the extended Huygens–Fresnel principle and second-order moments of the Wigner distribution function, we derive the analytical expressions for the spectral intensity, the root-mean-square (rms) angular width and the M 2 factor in turbulent atmosphere. Numerical results show that the intensity profile, which keeps the dark-hollow invariant in free space, will be gradually destroyed by the turbulence along the propagation distance. We believe that the MHSC beams have significant advantage over the hyperbolic sine-correlated beams for reducing the turbulence-induced degradation, especially for the MHSC beams with a higher beam order N . The effects of the beams parameters and the turbulent atmosphere on the beam quality are analyzed in detail.

International audience; We propose a method to generate beams according to transmission limitation condition by using the multi-distance phase retrieval algorithm. Propagation properties of hollow beams were determined by several intensity patterns along the travel axis. Predicted beams were obtained using a two-step phase filtering from a Gaussian beam with fundamental mode. An iterative phase retrieval method was employed for calculating the phase distribution in the filtering mask. This beam generation approach matched special propagation characteristics of the beams in practical applications.

With the development of modern precision optical fabrication and measurement technologies, optical freeform surfaces have been widely employed in different applications, especially in off-axis refl...

In coherent diffraction imaging systems, mulplex measurement on unknown object can enhance the quality of output image. We apply angular mulplexing scheme to capture several diffracting images. A tilt diffraction model is used for addressing the illumination beam in the imaging process. And an iterative phase retrieval algorithm is desingend and adopted to recover the image of sample. Numerical simulation results are provied to test the imaging method. This approach can be used to enhance the quality of reconstructed images in coherent diffraction imaging.

By utilizing the extended Huygens-Fresnel principle, we derive the analytical formulas for the cross-spectral density matrix elements of a radially polarized multi-Gaussian Schell-model (RPMGSM) beam propagating in oceanic turbulence. Effects of beam parameters and oceanic turbulence parameters on the propagation properties of RPMGSM beams are investigated in detail by numerical simulation. Our results show that the RPMGSM beam with larger beam order M has an advantage over the radially polarized Gaussian Schell-model beam for reducing turbulence-induced degradation. Compared with temperature-induced turbulence fluctuation, the salinity-induced turbulence fluctuation makes a greater contribution to the influence on propagation properties of RPMGSM beams.

The precision single point diamond turning technique has been a promising technology for generating small and medium-sized freeform optical elements with high surface quality. In this paper, we present an extremely off-axis freeform optical system with a large 10.0 mm pupil diameter and a low 3.0 F-number over a wide 28° field of view. It is composed of two freeform aluminum mirrors, which are fabricated efficiently by the single point diamond turning machine. The manufacturing strategy and parameters are estimated rationally and comprehensively, based on the freeform surface characters. The freeform aluminum mirror surface can reach submicron surface accuracy and achieve nanometer surface roughness. The final assembled prototype of the off-axis two-mirror freeform display optical system has the advantages of compactness, a broad spectrum, and good display imaging performance.

We derive several analytical expressions for the root-mean-square (rms) angular width and the M(2)-factor of the multi-sinc Schell-model (MSSM) beams propagating in non-Kolmogorov turbulence with the extended Huygens-Fresnel principle and the second-order moments of the Wigner distribution function. Numerical results show that a MSSM beam with dark-hollow far fields in free space has advantage over the one with flat-topped or multi-rings far fields for reducing the turbulence-induced degradation, which will become more obvious with larger dark-hollow size. Beam quality of MSSM beams can be further improved with longer wavelength and larger beam width, or under the condition of weaker turbulence. We also demonstrate that the non-Kolmogorov turbulence has significantly less effect on the MSSM beams than the Gaussian Schell-model beam.

We introduce a new kind of partially coherent beam, non-uniformly Hermite–Gaussian correlated beam, by employing a non-uniformly Hermite function to modulate the spectral degree of coherence. The evolution of such scalar beam on propagation in free space and turbulent atmosphere are investigated. It is demonstrated that the spectral intensity distributions exhibit extraordinary propagation characteristics, such as self-focusing and laterally shifted intensity maxima. The position of the maximum intensity and the intensity profile can be controlled by the order of the Hermite function. The results can be useful in free-space optical communications and beam shaping.

A new approach of eye locating from facial images based on area-blocks pairing and multi-angle template is proposed. In this paper, we first get the face region using skin-color model and extract the edge of face region, then obtain the blocks of suspected eye areas by morphological processing. Last, we can locate the position of eyes accurately using area-blocks pairing and multi-angle template matching. This approach is steady for image-whirling. The experimental results have shown the effectiveness and the robustness of our proposed algorithm.