Nonlinear Correction Method of Light Intensity in Gray Scale Fringe Projection and Phase Correction Method Based on the Method

Abstract

The invention discloses a gray fringe projection light intensity nonlinear correction method and a phase correction method based on the method. Gray scale lookup tables are established for measurement datum planes and surfaces of objects to be measured respectively in fringe projection measurement, and light intensity correction is performed on actual measurement fringes of the measurement datum planes and the surfaces of objects to be measured, so that the light nonlinearity of the measurement fringes is reduced, and the phase measurement accuracy is improved. Not only is inherent light intensity gamma distortion of a projector and a camera considered, but also differences of light intensity reflection characteristics of the surfaces of the measurement datum planes and different areas of the objects to be measured in the setup procedure of the lookup tables are considered, so that the light intensity correction method is more effective than existing methods, corrected fringes are closer to ideal values, and the measurement accuracy can be improved substantially through the method.

Description

【Technical field】 [0001] The invention belongs to the field of optical three-dimensional measurement, and relates to a method for nonlinearly correcting light intensity of projected fringes in fringe projection three-dimensional measurement. 【Background technique】 [0002] As one of the optical three-dimensional measurement techniques, fringe projection three-dimensional profilometry has great application prospects in the fields of archaeological measurement, face measurement, and planar vibration measurement. It can be predicted that fringe projection 3D profilometry will play an important role in the future 3-D printing technology. [0003] In fringe projection three-dimensional profilometry, the high-precision acquisition of characteristic phase is the guarantee of high-precision measurement. However, due to the inherent nonlinear characteristics of projected light intensity or collected light intensity of the projector, CCD and other hardware itself, as well as the diff...

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Problems solved by technology

[0004] The document "Phase error compensation for a3-D shape measurement system based on the phase-shifting method" proposes a non-linear correction method for light intensity with excellent performance: measure and fit the gamma curve of the projector, and use the phase shift method to solve the formula Obtain the phase value of the fringe under the influence of the γ characteristic And the difference Δφ between it and the phase value without the influence of the γ characteristic, based on which the look-up table is established It is used for subsequent phase compensation; this method can better reduce the error caused by the gamma characteristic of the projector to the projected fringe phase, but as mentioned in the article, this method is suitable for the projected fringe measurement situation using the phase shift method, in the Fourier The effectiveness of the application of transform profilometry has not been confirmed, and the γ correction claimed by the author in the article is only for the projector and does not involve the CCD

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