Active versus passive projector nonlinear gamma compensation method for high-quality fringe pattern generation

Abstract

This paper presents our comparing study on active and passive methods for compensating the phase error induced by the projector nonlinear gamma effect. The active method modifies the fringe patterns before their projection; and the passive method, in contrast, compensates for the phase error after capturing fringe patterns. Our study finds that the active method tends to provides more consistent high-quality fringe patterns regardless the amount of projector's defocusing; yet the effectiveness of the passive method is sensitive to the measurement conditions, albeit the passive method could provide equally good quality phase under the optimal calibration condition. Experimental results will be presented to compare these two different methods. KeywordsNonlinear gamma, phase error, structured light, phase shifting, projector defocusing Copyright 2014 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. ABSTRACTThis paper presents our comparing study on active and passive methods for compensating the phase error induced by the projector nonlinear gamma effect. The active method modifies the fringe patterns before their projection; and the passive method, in contrast, compensates for the phase error after capturing fringe patterns. Our study finds that the active method tends to provides more consistent high-quality fringe patterns regardless the amount of projector's defocusing; yet the effectiveness of the passive method is sensitive to the measurement conditions, albeit the passive method could provide equally good quality phase under the optimal calibration condition. Experimental results will be presented to compare these two different methods.

Deflectometry for specular surfaces: an overview

“…Likewise, in most computer screens and projectors the relationship between the digital gray level and luminance depends on the graphics driver and its setting, is usually nonlinear, and often does not span the full input or output range. These deviations may be interpreted as harmonics in the fringe profile, and comprehensive recipes have been given on how to suppress them by an appropriate design of the phasereconstruction method (Surrel, 2000;Burke, 2012); however, typically the screen or projector is linearized by a look-up table or a fitted function before use (Ma et al, 2012;Zhang, 2014). Thus, systematic phase errors can be removed almost completely.…”

Deflectometry for specular surfaces: an overview

“…Likewise, in most computer screens and projectors the relationship between the digital gray level and luminance depends on the graphics driver and its setting, is usually non-linear, and often does not span the full input or output range. These deviations may be interpreted as harmonics in the fringe profile, and comprehensive recipes have been given on how to suppress them by an appropriate design of the phase-reconstruction method [447,448]; however, typically the screen or projector is linearized by a look-up table or a fitted function before use [449,450]. Thus, systematic phase errors can be removed almost completely.…”

Structured light system calibration method with optimal fringe angle

“…It is important to note that to correct the nonlinear gamma effect of the projector, we applied an active gamma compensation method as introduced in [30].…”