There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

We introduce the concept of the perfect optical vortex whose dark hollow radius does not depend on the topological charge. It is shown analytically and experimentally that such a vortex can be approximately generated in the Fourier transforming optical system with a computer-controlled liquid-crystal spatial light modulator.

Generation of the "perfect" optical vortex using a liquid-crystal spatial light modulator

On-machine and in-process surface metrology for precision manufacturing

Micro-structured functional surfaces have achieved widespread applications in various advanced scientific, technological, industrial, and engineered fields due to their excellent performances, which are vitally limited by their feasible fabrication. Currently, ultra-precision machining, typically including ultra-precision diamond turning, ultra-precision diamond milling, ultra-precision diamond scratching, ultra-precision grinding, and ultra-precision polishing, is developed as a very-promising solution for the micro-structured functional surface fabrication with high quality, high efficiency, high flexibility, and low cost. Therefore, this paper aims to briefly review the current state of the art in the investigation into ultra-precision machining characteristics of micro-structured functional surfaces with a focus on their typical advanced applications as the significant achievements of their ultra-precision machining fabrication, discuss the key challenges, and further provide new insights into ultra-precision machining of micro-structured functional surfaces for the future research and their further advanced applications.

Advances in ultra-precision machining of micro-structured functional surfaces and their typical applications

Low-power integrated projection technology can play a key role in development of low-cost mobile devices with built-in high-resolution projectors. Low-cost 3D imaging and holography systems are also among applications of such a technology. In this paper, an integrated projection system based on a two-dimensional optical phased array with fast beam steering capability is reported. Forward biased p-i-n phase modulators with 200MHz bandwidth are used per each array element for rapid phase control. An optimization algorithm is implemented to compensate for the phase dependent attenuation of the p-i-n modulators. Using rapid vector scanning technique, images were formed and recorded within a single snapshot of the IR camera.

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Nanophotonic projection system.

This paper presents a disparity pattern-based autostereoscopic (DPA) 3D metrology system that makes use of a microlens array to capture raw 3D information of the measured surface in a single snapshot through a CCD camera. Hence, a 3D digital model of the target surface with the measuring data is generated through a system-associated direct extraction of disparity information (DEDI) method. The DEDI method is highly efficient for performing the direct 3D mapping of the target surface based on tomography-like operation upon every depth plane with the defocused information excluded. Precise measurement results are provided through an error-elimination process based on statistical analysis. Experimental results show that the proposed DPA 3D metrology system is capable of measuring 3D microstructured surfaces with submicrometer measuring repeatability for high precision and in situ measurement of microstructured surfaces.

Disparity pattern-based autostereoscopic 3D metrology system for in situ measurement of microstructured surfaces.

An on-chip optical trapping and sorting system composed of a microchamber and a microlens array (MLA) is demonstrated. The MLA focuses the incident light into multiple confocal spots to trap the particles within the microchamber. The SiO2/ZrO2 solgel material is introduced in the fabrication of MLA for its unique optical and chemical characters. Moreover, in order to prove the effectiveness of the system, experimental demonstration of multibeam trapping and locked-in transport of micropolymer particles in the microchamber is implemented. The system may easily be integrated as microfluidic devices, offering a simple and efficient solution for optical trapping and sorting of biological particles in lab-on-a-chip technologies.

Microlens-array-enabled on-chip optical trapping and sorting

The need to image objects through light-scattering materials is common in a range of applications. Different methods have been investigated to acquire the image of the object when diffusers are presented. In this paper, we demonstrate the object reconstruction with single-shot imaging based on the correlography principle and phase retrieval algorithm with coherent illumination. We prove the possibility of reconstructing positive and negative objects in both transmission and reflection modes with collimated and scattered light. Formulas for calculating the size of the object from the reconstructed image are presented. We also prove that the object can be retrieved from a small section of the raw speckle image. These interesting features will have broad potential applications in many areas (such as biomedicine, security and sensing).

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Lensless wide-field single-shot imaging through turbid media based on object-modulated speckles

A new real-time integral imaging pick-up and display method is demonstrated. This proposed method utilizes the dual-camera optical pick-up part to collect 3D information of real scene in real-time without pre-calibration. Elemental images are then provided by a computer-generated integral imaging part and displayed by a projection-type integral imaging display part. The theoretical analysis indicates the method is robust to the camera position deviation, which profits the real-time data processing. Experimental results show that the fully continuous, real 3D scene pick-up and display system is feasible with a throughput of 8 fps in real time. Further analysis predicts that the parallel optimization can be adopted by the proposed method for real-time 3D pick-up and display with a throughput of 25 fps.

Dual-camera enabled real-time three-dimensional integral imaging pick-up and display.

An approximate voxel model for integral imaging is proposed by ray tracing. By analyzing the case of corresponding pixels overlapping completely and partially in the image space, the voxel is defined with an appropriate approximation, and the voxel size and its distribution feature in imaging space are derived. The model is verified in a reconstruction experiment of a resolution target and compared with the calculation result of an integral imaging display or reconstruction system. The proposed model is simple and easy to calculate and thus useful for the evaluation and optimization of integral imaging systems.

Xing Zhao

Papers

Disparity pattern-based autostereoscopic 3D metrology system for in situ measurement of microstructured surfaces.

Microlens-array-enabled on-chip optical trapping and sorting

Lensless wide-field single-shot imaging through turbid media based on object-modulated speckles

Dual-camera enabled real-time three-dimensional integral imaging pick-up and display.

Voxel model for evaluation of a three-dimensional display and reconstruction in integral imaging.