High-speed scanning stroboscopic fringe-pattern projection technology for three-dimensional shape precision measurement

Abstract

A high-speed scanning stroboscopic fringe-pattern projection system is designed. A high-speed rotating polygon mirror and a line-structured laser cooperate to produce stable and unambiguous stroboscopic fringe patterns. The system combines the rapidity of the grating projection with the high accuracy of the line-structured laser light source. The fringe patterns have fast frame rate, great density, high precision, and high brightness, with convenience and accuracy in adjusting brightness, frequency, linewidth, and the amount of phase shift. The characteristics and the stability of this system are verified by experiments. Experimental results show that the finest linewidth can reach 40 μm and that the minimum fringe cycle is 80 μm. Circuit modulation makes the light source system flexibly adjustable, easy to control in real time, and convenient to project various fringe patterns. Combined with different light intensity adjustment algorithms and 3D computation models, the 3D topography with high accuracy can be obtained for objects measured under different environments or objects with different sizes, morphologies, and optical properties. The proposed system shows a broad application prospect for fast 3D shape precision measurements, particularly in the industrial field of 3D online detection for precision devices.

Towards Machine Vision Based Railway Assets Predictive Maintenance

“…The measuring principle with Gobo (Graphical optical blackout)-based high-speed Projection of fringe patterns with the use of high-speed cameras allows to record up to 10,000 3D images /s. There are many papers dealing with the 3D stereo measurement with projection patterns [15,16,17,18,19].…”

Vibration measurement by projection of phase-modulated and amplitude-modulated structured light

“…Time average holography and time average digital speckle pattern interferometry (DSPI) allow whole-field analyses and are very suitable for micro-vibration measurements. The dynamic range of those techniques can be enlarged with the help of stroboscopy (Hariharan et al, 1987;Watrasiewicz & Spicer, 1968;Yang et al, 2009;Yang et al, 2014) and phase-modulated reference beams (Barbosa & Lokberg & Høgmoen, 1976;Muramatsu, 1997). If the vibration amplitudes are too large to be measured by standard time average methods, doublepulse (Pedrini et al, 2002) or high-speed camera holography (Fu et al, 2007;Pedrini et al, 2006) are also useful tools for this purpose, even enabling the analysis of non-harmonic vibration phenomena.…”

Microscopic Three-Dimensional Measurement Based on Telecentric Stereo and Speckle Projection Methods

“…The microscopic fringe projection method, on the contrary, is studied widely and suitable for measuring microstructures whose dimensions are in the order of millimeters and above with the measurement accuracy from a few to tens of microns [ 9 , 10 , 11 ]. It can realize well 3D measurement of microstructures with different surfaces such as a gauge block [ 12 ], ball grid arrays (BGA) [ 13 , 14 ], coins [ 15 , 16 ], a wafer [ 17 ], an earphone diaphragm [ 18 ], and a step master [ 19 ], and can also perform dynamic measurements [ 20 , 21 ]. Due to a lack of suitable methods for system calibration and removing carrier-phase components from the measurement phases [ 22 ], it is difficult for its measurement accuracy to reach two or three microns and below.…”