Single-Shot Phase Measuring Profilometry Based on Quaternary Grating Projection

In this paper, we propose a new single-shot three-dimensional (3D) measuring method based on quaternary grating projection. In traditional binary grating phase measuring profilometry (PMP), a multi-step or color fringe pattern are usually used to extract the sinusoidal fringes. In our proposed method, by using the DLP4500’s 2-bit gray coding mode, the grayscale is quaternary. The three non-zero grayscales cyclically arranged in equal width, and the fourth grey value is 0 which is not encoded in the fringe pattern but represents the shadow information in the deformed pattern, where a quaternary grating is encoded. When the DLP4500 projects the quaternary grating onto the measured object, the charge coupled device (CCD) captures the corresponding deformed pattern synchronously. Three frames of binary deformed patterns with 1/3 duty cycle and a relative displacement of 1/3 period can be decomposed by the segmentation algorithm proposed in this paper. Three sinusoidal deformed patterns with a 2π/3 shift-phase can be obtained by extracting the fundamental frequency of the three binary deformed patterns correspondingly, and the 3D shape of the object can be reconstructed by PMP. Experimental results show the effectiveness and feasibility of the proposed method. Because the DLP4500 only needs 2-bit coded grating for projection, the refresh rate of the projected grating is as high as 1428 Hz, which will have a broad application prospect in real time and fast online measurement.

SIMULASI LENSA GRATING TERHADAP EFISIENSI DIFRAKSI GRATING PADA SISTEM PEMISAH CAHAYA SPEKTRAL CONCENTRATED PHOTOVOLTAIC/THERMAL

A spectral beam splitting concentrated photovoltaic/thermal (SBS CPVT) system is a new technology in PV areas . In order to split the sunlight, the grating lens is used in this study. The tool of this study is G-Solver software which simulates the diffraction efficiency of visible light and infrared light of the blazed and binary grating lens. The aim of this paper is to analyze the potential of the diffraction efficiency of grating lens when applied in SBS CPVT. The result show that binary grating, the highest diffraction efficiency for the visible light is also almost unchanged for the aspect ratio from 1.4 to 2, but the peak wavelength shift from around 360 nm to 510 nm, while, for IR light, the diffraction efficiency decrease from aspect ratio 1.4 to 2. On the other hand, blazed grating, The highest diffraction efficiency for the visible light is almost unchanged for the aspect ratio from 1.4 to 2, but the peak wavelengths shift from around 350 nm to 500 nm. While IR light, the diffraction efficiency decrease with the aspect ratio 1.4 to 2

A stroboscopic online three-dimensional measurement for fast rotating object with binary dithered patterns

In the three-dimensional (3D) measurement, phase measuring profilometry (PMP) requires no less than three deformed sinusoidal patterns, limiting its applications to static scenarios only. In this paper, a stroboscopic online PMP for fast rotating object with binary dithered patterns is proposed. N frames of novel circular binary grating patterns are designed to measure a rotating object. A defocused digital light projector projects the designed patterns onto the object with stroboscopic method, the corresponding deformed patterns can be “frozen” by charge-coupled device (CCD) camera. Owing to the repeatability and periodicity of rotating movement, a synchronization control unit is used to keep the object at the fixed position in each “frozen” deformed pattern. Every projected pattern is shifted from the previous pattern by a factor of 2π/N. This method makes the images of the object appear stationary in the deformed patterns. The experimental results show the accurate 3D shape of fast rotating object can be reconstructed with the proposed method.