This paper presents a thorough comparison between the digital-light-processing (DLP) technology and liquid-crystaldisplay (LCD) projection technology on high-quality 3D shape measurement. Specifically, each individual color channel and the combination of three channels together are studied with the focused sinusoidal pattern (FSP) method and defocused binary pattern (DBP) method. Experimental data indicated that for slow speed measurements, because of its higher contrast, DLP has the advantage for the DBP, or when the precision synchronization is presented for FSP method. Since LCD does not have rigorous timing requirements, it provides more flexibility for system development for FSP method.
KEYWORDS: Digital Light Processing, Projection systems, Liquid crystal on silicon, 3D metrology, Cameras, Binary data, Signal to noise ratio, Quality measurement, Fringe analysis, Phase shifts
This paper presents a thorough comparison between the digital-light-processing (DLP) technology and liquid-crystal-onsilicon
(LCoS) technology on high-quality 3D shape measurement. Specifically, we will study not only each individual
color, but also the combination of different color (i.e., white light). The binary defocusing and focused sinusoidal fringe
projection methods will be evaluated under all these scenarios. Experimental data demonstrated that for slow speed measurements,
DLP has better fringe contrast and thus higher signal to noise ratio (SNR) for better quality 3D shape measurement
when the binary defocusing method is employed, or when proper synchronization is present when the focus
sinusoidal method is used; and LCoS provides more flexibility for system development when the focus sinusoidal method
is employed.
Single reference-phase-based methods have been extensively utilized in digital fringe projection systems, yet they might not provide the maximum sensitivity given a hardware system configuration. This paper presents an innovative method to improve the measurement quality by utilizing two orthogonal phase maps. Specifically, two reference phase maps generated from horizontal and vertical (i.e., orthogonal) fringe patterns projected are combined into a vector reference phase map through a linear combination for depth extraction. The experiments have been conducted to verify the superiority of the proposed method over a conventional single reference-phase-based approach.
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