In this paper, we propose a holographic capture and projection system of real objects based on tunable zoom lenses. Different from the traditional holographic system, a liquid lens-based zoom camera and a digital conical lens are used as key parts to reach the functions of holographic capture and projection, respectively. The zoom camera is produced by combing liquid lenses and solid lenses, which has the advantages of fast response and light weight. By electrically controlling the curvature of the liquid-liquid surface, the focal length of the zoom camera can be changed easily. As another tunable zoom lens, the digital conical lens has a large focal depth and the optical property is perfectly used in the holographic system for adaptive projection, especially for multilayer imaging. By loading the phase of the conical lens on the spatial light modulator, the reconstructed image can be projected with large depths. With the proposed system, holographic zoom capture and color reproduction of real objects can be achieved based on a simple structure. Experimental results verify the feasibility of the proposed system. The proposed system is expected to be applied to microprojection and three-dimensional display technology.

In this work, we propose an active optical zoom system. The zoom module of the system is formed by a liquid lens and a spatial light modulator (SLM). By controlling the focal lengths of the liquid lens and the encoded digital lens on the SLM panel, we can change the magnification of an image without mechanical moving parts and keep the output plane stationary. The magnification can change from 1/3 to 3/2 as the focal length of the encoded lens on the SLM changes from infinity to 24 cm. The proposed active zoom system is simple and flexible, and has widespread application in optical communications, imaging systems, and displays.

The random phase method and quadratic phase method are most widely used in the generation of non-iterative phase holograms. However, the former leads to the reconstruction being severely disturbed by speckle noise, with serious loss of detailed information, and the latter leads to the reconstruction being contaminated with ringing artifacts. To solve these problems, we present a novel, to the best of our knowledge, method capable of generating non-iterative phase holograms, hereafter referred to as hybrid-phase-only holograms (HPOHs). Our proposal is to use a weight factor to combine the random phase and quadratic phase to generate a hybrid phase mask. The hybrid phase mask is then superimposed on the target image to obtain a complex hologram by simple Fourier transform. Followed by retaining the phase of the complex hologram, we can generate the corresponding HPOH. The effects of different weight factors on the holographic reconstructions are discussed. Numerical simulations of reconstruction quality associated with the proposed method, random phase method, and quadratic phase method are presented for comparison purposes. Optical experiments based on liquid crystal on silicon also demonstrate the validity of the method.

In a classical metasurface-based holographic display system, a clear holographic reconstruction image can be obtained only in the back-focal-plane of the lens. However, when the receiving plane deviates from the focal plane, the reconstructed holographic image suffers from degradations that limit the quality of the images. Hence, we propose a novel metasurface-based holographic display to realize clearly continuous imaging within the specified position range by superimposing the meta-axilens phase. It can effectively relieve the alignment requirements of the imaging system. Firstly, the parameters and properties of alldielectric meta-atom is analyzed. Then we compare and demonstrate two sets of metasurface-based optical elements (metaaxicon, meta-lens, and meta-axilens), made by silicon meta-atoms working at 610 nm. Furthermore, we show that the metasurface hologram with the axilens phase can form a series of the relatively clear holographic images away from the focal plane. Our proposal suggests a method to reconstruct holographic wavefront in different planes simultaneously, and one can find their application domain, such as 3D biological imaging, spectroscopy, optical information storage, and encryption.

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In this paper, we propose a holographic zoom system based on a liquid lens. By loading a divergent spherical wave, the focus planes of the reconstructed image and the zero-order diffraction beam induced by the liquid crystal on silicon (LCoS) can be separated . By controlling the focal lengths of the liquid lens and the encoded digital lens on the spatial light modulator panel, we can change the magnification of the reconstructed image very quickly, without mechanical parts and keeping the output plane stationary. Keywords Spatial light modulator; liquid lens; zoom system. d d d r d.( 4 )

A stereovision-based disparity evaluation algorithm was developed for rice crop field recognition. The gray level intensities and the correlation relation were integrated to produce the disparities of stereo-images. The surface of ground and rice were though as two rough planes, but their disparities waved in a narrow range. The cut/uncut edges of rice crops were first detected and track through the images. We used a step model to locate those edge positions. The points besides the edges were matched respectively to get disparity values using area correlation method. The 3D camera coordinates were computed based on those disparities. The vehicle coordinates were obtained by multiplying the 3D camera coordinates with a transform formula. It has been implemented on an agricultural robot and evaluated in rice crop field with straight rows. The results indicated that the developed stereovision navigation system is capable of reconstructing the field image.

To provide better reconstruction quality, it takes more time for iterative algorithms, especially when multiple holograms need to be computed. A non-iterative method for calculating a phase hologram with adaptive weighted constraints is proposed, which iteratively calculates the optimized phase with a rectangular aperture as the amplitude and multiplies the initial quadratic phase as the initial complex amplitude. Subtraction feedback is introduced to improve the visual effect and avoid the overcompensation problem of division feedback. The proposed method is suitable for generating non-iterative phase holograms with different sizes, and it can further be applied to the calculation of color holograms. It improves computational speed under the premise of ensuring reconstruction quality and can adapt to the needs of different systems with different sizes or different location requirements for holographic reconstruction. Optical experiments also demonstrate the effectiveness of this method.