Publications by authors named "Axiu Cao"

The light homogenizing element is a crucial component of the illumination system of the lithography machine. Its primary purpose is to realize the uniform distribution of energy. However, it suffers from a common issue, which is angular spectrum discreteness, which significantly impacts light uniformity.

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An improved binary amplitude modulation-based phase retrieval method studied by means of simulations and experiments is presented in this paper. The idea of ptychography is introduced for the purpose of designing random binary amplitude masks. The masks have the features that part of the light transmission regions is overlapped with each other and the overlapping positions are randomly distributed.

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Microlenses can be widely used in integrated micro-optical systems. However, in some special applications, such as light field imaging systems, multifocal microlens arrays (MLA) are expected to improve imaging resolution. For the fabrication of multifocal MLA, the traditional fabrication method is no longer applicable.

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Double microlens arrays (MLAs) in series can be used to divide and superpose laser beam so as to achieve a homogenized spot. However, for laser beam homogenization with high coherence, the periodic lattice distribution in the homogenized spot will be generated due to the periodicity of the traditional MLA, which greatly reduces the uniformity of the homogenized spot. To solve this problem, a monolithic and highly integrated double-sided random microlens array (D-rMLA) is proposed for the purpose of achieving laser beam homogenization.

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The use of the diffractive optical element (DOE) can often significantly reduce the size and enhance the performance of the optical system, but it is mostly prevented by low diffraction efficiency and serious speckle noise due to the quantization error. In this paper, an error tracking-control-reduction (ETCR) algorithm is proposed to suppress the quantization error, which adjusts the accumulative action, controls the current state and predicts the trend of the error. The simulation and experiment results verify that the ETCR algorithm has high diffraction efficiency which can be comparable with the Gerchberg-Saxton (GS) and Modified GS algorithms.

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The miniaturized and integrated microlens array (MLA) can effectively achieve the beam homogenization, compactness and miniaturization of laser systems. When the high-coherence laser beam is homogenized by means of using the MLA, interference fringes will occur in the homogenized light spot due to the periodicity of the MLA, which seriously affects the uniformity of the homogenized light spot. To solve this problem, a novel random microlens array (rMLA) structure was proposed for the purpose of achieving beam homogenization.

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Divergent light illumination can effectively increase the diffraction angle of holographic projection. However, the achieved maximum image size is limited to the geometric enlargement of the hologram size with the existing double-sampling Fresnel diffraction algorithm. In this paper, an effective method for further magnifying the image is proposed.

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The naked-eye three-dimensional (3D) display technology without wearing equipment is an inevitable future development trend. In this paper, the design and fabrication of a flexible naked-eye 3D display film element based on a microstructure have been proposed to achieve a high-resolution 3D display effect. The film element consists of two sets of key microstructures, namely, a microimage array (MIA) and microlens array (MLA).

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In this study, double-sided polymer surface nanostructures are fabricated using twice nanoimprint lithography and metal deposition technique. We perform electrical property measurement on these double-sided surface nanostructures. Open-circuit voltage and short-circuit current of the as-prepared samples with double-sided surface nanostructures and conductive electrode are recorded using an oscilloscope with applying different external force.

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The artificial compound eye (ACE) structure is a new type of miniaturized, lightweight and intelligent imaging system. This paper has proposed to design a multi-spectral ACE structure to enable the structure to achieve multi-spectral information on the basis of imaging. The sub-eyes in the compound eye structure have been designed as diffractive beam splitting lenses with the same focal length of 20 mm, but with the different designed center wavelengths of 650 nm, 532 nm, and 445 nm, respectively.

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This paper presents an approach that is capable of producing a color image using a single composite diffractive optical element (CDOE). In this approach, the imaging function of a DOE and the spectral deflection characteristics of a grating were combined together to obtain a color image at a certain position. The DOE was designed specially to image the red, green, and blue lights at the same distance along an optical axis, and the grating was designed to overlay the images to an off-axis position.

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Quantum correlated imaging using the intensity fluctuations of thermal light possesses advantages of high resolution and strong anti-interference ability. The common method to produce pseudo-thermal light source is using a rotary ground glass and transmission of laser beam. In the present work, we propose a method for the fabrication of microwell arrays with randomly varied diameters, which could be used as a new structural element for pseudo-thermal speckle light source.

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Miniaturized bionic compound eyes featured with multi-aperture imaging have potential applications in the areas of micro opto-electro-mechanical-system. In this manuscript, we present a novel structure of the bionic compound eye with multiple focal lengths consists of an array of individual lenses with 1000 µm diameter. The simulation results of the designed multifocal bionic compound eye (MBCE) with two focal lengths of 190 mm and 44.

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We report a novel and non-iterative method for the generation of phase-only Fourier hologram for image projection. Briefly, target image is first added with a special quadratic phase and then padded with zeros. A complex Fourier hologram is generated via the simple fast Fourier transform.

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Vector optical field has recently gained interest in a variety of application fields due to its novel characteristics. Conventional approaches of generating vector optical fields have difficulties in forming highly continuous polarization and suffer from the issue of high energy utilization rates. In order to address these issues, in this study a single optical path was proposed to generate vector optical fields where the birefringent phase plate modulated a linear polarized light into a vector optical field, which was then demodulated to a non-uniform linear polarization distribution of the vector optical field by the polarization demodulation module.

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Iterative Fourier transform algorithms are widely used for creating holograms in holographic image projection. However, the reconstructed image always suffers from the speckle noise severely due to the uncontrolled phase distribution of the image. In this paper, a new iterative method is proposed to eliminate the speckle noise.

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Hollow nanospheres array is a special nanostructure with great applications in photonics, electronics and biochemistry. The nanofabrication technique with high resolution is crucial to nanosciences and nano-technology. This paper presents a novel nonconventional nano-conglutination technology combining polystyrenes spheres (PSs) self-assembly, conglutination and a lift-off process to fabricate the hollow nanospheres array with nanoholes.

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An economical method for fabricating spiral phase plate (SPP) with continuous surface is proposed in this paper. We use an interval to quantize a three dimensional surface of an SPP into two dimensional bars to form a binary mask. The exposure dose can be precisely distributed through this mask in the exposure process.

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