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.

/pdf/nanophotonic-projection-system-sjpe7euu4l.pdf

Nanophotonic projection system.

To obtain satisfactory performance in characterizing optical freeform surfaces with local features, this paper proposes a model of a radial basis function with slope-based shape factor and distribution (RBF-SSD). Compared to previous RBF-slope models with only slope-based shape factors, the RBF-SSD model relates both shape factors and distribution with the surface slope, ensuring greater fitting ability can be achieved when fitting a surface with local features. Fitting experiments for two different surfaces demonstrated the fitting ability of the RBF-SSD model. An off-axis three-mirror system with 3  °    ×  3.6  °   field of view was designed as an example to show the optical design efficacy of our model.

Model of radial basis functions with slope-based shape factor and distribution for optical freeform surface

An optimized remote material detection scheme based on the laser filament-induced plasma spectroscopy and light detection and ranging (FIPS-LIDAR) is proposed in this work. The elemental composition and concentration of aerosol are measured by FIPS-LIDAR. By focusing the femtosecond laser with a large aperture (Φ41 cm) concave mirror and coaxial fluorescence collection scheme, the remote detection of aerosol in air at μg/m3 level has been realized at a distance of 30 m. The limit of detection for Na+ in aerosol droplets is 8 ppm (3 μg/m3 in air), which is the lowest detection limit that has been reported using millijoule femtosecond laser pulse (4.4 mJ). Furthermore, using spectral preprocessing and optimization of the proposed significance of peak (SOP) algorithm, feature peak signals are extracted from weak signals and the limit of detection can be further decreased to 1.4 μg/m3.

Detection of 1.4 μg/m3 Na+ in aerosol at a 30 m distance using 1 kHz femtosecond laser filamentation in air.

We report an integral imaging method with continuous imaging space. This method simultaneously reconstructs real and virtual images in the virtual mode, with a minimum gap that separates the entire imaging space into real and virtual space. Experimental results show that the gap is reduced to 45% of that in a conventional integral imaging system with the same parameters.

https://iopscience.iop.org/article/10.1088/1674-1056/22/5/054202/pdf

Continuous imaging space in three-dimensional integral imaging

Provided is a light-operated echo wall mode generating system based on an azobenzene material. The system comprises a broadband light source, a 365nm ultraviolet source, an ultraviolet polarizing film, a conical fiber for generating an evanescent field, a clamping device and U-shaped frame of the conical fiber, a quartz microspherical cavity plated with an azobenzene thin film, a three-dimensional adjusting frame, a microobjective, a CCD, an optical fiber for connection, a display device and the like. The system achieves a light-operated echo wall system through sensitization processing on a micro-resonant cavity on the basis of a traditional micro-resonant cavity-conical fiber coupling system. In addition, due to the narrow linewidth property of the echo wall mode and the sensitivity of the azobenzene material to ultraviolet light, the device can be used for precision measurement of intensity of the ultraviolet light. The light-operated echo wall mode generating system can achieve the echo wall mode of different optical properties by adjusting the intensity and polarization state of the ultraviolet light and changing the size of the microspherical cavity and the thickness of the azobenzene thin film. The light-operated echo wall mode generating system has the advantages of being compact in structure, capable of achieving light-operated tuning of the optical property of the echo wall mode, high in ultraviolet light sensing sensitivity and the like.

Light-operated echo wall mode generating system based on azobenzene material

Autostereoscopy based three-dimensional (3D) digital reconstruction has been widely applied in the field of medical science, entertainment, design, industrial manufacture, precision measurement and many other areas. The 3D digital model of the target can be reconstructed based on the series of two-dimensional (2D) information acquired by the autostereoscopic system, which consists multiple lens and can provide information of the target from multiple angles. This paper presents a generalized and precise autostereoscopic three-dimensional (3D) digital reconstruction method based on Direct Extraction of Disparity Information (DEDI) which can be used to any transform autostereoscopic systems and provides accurate 3D reconstruction results through error elimination process based on statistical analysis. The feasibility of DEDI method has been successfully verified through a series of optical 3D digital reconstruction experiments on different autostereoscopic systems which is highly efficient to perform the direct full 3D digital model construction based on tomography-like operation upon every depth plane with the exclusion of the defocused information. With the absolute focused information processed by DEDI method, the 3D digital model of the target can be directly and precisely formed along the axial direction with the depth information.

A defocus-information-free autostereoscopic three-dimensional (3D) digital reconstruction method using direct extraction of disparity information (DEDI)

Xing Zhao

Papers

Model of radial basis functions with slope-based shape factor and distribution for optical freeform surface

Detection of 1.4 μg/m3 Na+ in aerosol at a 30 m distance using 1 kHz femtosecond laser filamentation in air.

Continuous imaging space in three-dimensional integral imaging

Light-operated echo wall mode generating system based on azobenzene material

A defocus-information-free autostereoscopic three-dimensional (3D) digital reconstruction method using direct extraction of disparity information (DEDI)