This paper presents a method to simultaneously get 3D hand and palmprint information by projecting composite color
fringe patterns. The existing researches mainly focus on 2D biological features, and the extracted features from 2D image
are distorted by pressure or lose the third dimensional information. But 3D features with non-contact operation can
obtain the characteristic distribution patterns without distortion, and simultaneously obtain real hand morphology and the
global properties of hand and palmprint. A prototype 3D imaging system is designed to capture and process the
composite color fringe patterns on the hand surface. The hardware configuration comprises a DLP (digital light
processing) projector, a color CCD camera with fireware port and a personal computer (PC). In order to fast acquire 3D
accurate shape data, sinusoidal and binary fringe patterns are coded into red, green and blue channels to generate
composite color fringe pattern images. The DLP projector projects composite RGB fringe patterns onto the surface of
human hands. From another viewpoint, the CCD camera captures the images and saves them into the computer for postprocessing.
Wrapped phase information can be calculated from the sinusoidal fringe patterns with high precision. While
the absolute fringe order of each sinusoidal fringe pattern is determined by the binary fringe pattern sequences. The
absolute phase map of each pixel can be calculated by combining the obtained wrapped phase and the absolute fringe
order. Some experimental results on human hands show that the proposed method correctly obtains the absolute phase
(shape) data of hand and palmprint.
This paper presents an absolute phase calculation method from one composite RGB fringe pattern image by using
the windowed Fourier transform (WFT) algorithm and the optimum three-frequency selection method. Three fringe
patterns having the optimum fringe numbers are coded into the red, green and blue channels of a composite color
image. The generated composite RGB image is projected onto a measured object surface from a Digital Light
Processing (DLP) projector and the deformed fringe patterns captured by a color CCD camera from a different
viewpoint. The wrapped phase information will be calculated by the WFT algorithm. The WFT algorithm limits the
processed image to a small area, so it can give much better phase near edges or discontinuities than FT algorithm.
Applying the WFT algorithm to the three fringe patterns obtains three wrapped phase maps. An absolute phase map
is calculated pixel by pixel from one composite RGB fringe pattern image after applying the optimum threefrequency
selection method to the three obtained wrapped phase maps. Therefore, the proposed method can
measure absolute phase of objects having discontinuous surfaces from one snapshot image. Experimental results on
moving discontinuous objects show that the proposed method reliably obtains the absolute phase information.
We present a simple calibration method of the phase-based 3D imaging systems based on an uneven fringe
projection method. The relationship between absolute phase and depth is linear and independent of pixel position,
which can be represented by a polynomial function. By designing a plate having discrete markers with known
separate distance in between on the plate surface and projecting uneven fringe pattern onto it, one can calculate the
absolute phase of the centre on each marker. The 3D coordinates of all the markers can be obtained by a general
CCD camera calibration method. So coefficient set of the polynomial function are determined by using the obtained
absolute phase and depth of all the markers. The proposed method was applied to calibrate a phase-based 3D
imaging system. Experimental results and performance evaluation show that the proposed calibration method can
easily build up the accurate relationship between absolute phase and depth information data.
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