KEYWORDS: Video, 3D metrology, Composites, RGB color model, 3D modeling, Optical engineering, CCD cameras, Fluctuations and noise, Cameras, Phase shifts
A color-coded computer-generated Moiré profilometry (CGMP) with real-time 3D measurement and synchronous monitoring video collection is proposed. In this method, a sinusoidal grating and the direct current (DC) component of it are encoded in the blue and red channels of a color composite grating, respectively. This color composite grating is projected onto the measured object, and a corresponding color deformed pattern is sampled by an RGB camera. A monochrome sinusoidal deformed pattern and a flat image are demodulated from the color deformed pattern by color separation. The flat image reflects the DC component of the monochrome sinusoidal deformed pattern and the monitoring image in real time. The DC component of the monochrome sinusoidal deformed pattern is efficiently figured out by multiplying the flat image with an introduced coefficient, even though the DC spectrum and the first-order spectrum of the monochrome sinusoidal deformed pattern overlap. By establishing a color-coded CGMP, the 3D shape of the measured object is reconstructed successfully. Due to its single-shot feature, the 3D information and synchronizing monitoring video are sampled in real time. Some static objects and moving objects are measured to verify the feasibility, validity, and accuracy of the proposed method.
Liquid crystal materials don’t emit light, and its phase difference is connections with viewing angle. In general, the brightness of liquid crystal displays (LCD) is limited and the color shift apparently exists at large viewing angles. Furthermore, the same problem is also emerged in organic light emitting diode (OLED) displays. Microcavity resonance effect in OLED seriously affects the luminance and brings about “blue shift” as viewing angle increases. We propose an optical film with micro-prism to improve the viewing angle characteristics of LCD and OLED, which can increase the brightness and decrease the color shift. Excellent agreements supported by simulations and experiments are obtained. The proposed optical film is coated on a 75in. 8K (7680×4320) LCD to measure the optical parameters. When the viewing (polar) angle is between ±60° and a white pattern is displayed, the maximum color shift Δμ'v' can be decreased from 0.027 to 0.006 after the proposed optical film is introduced. Moreover, the brightness at large viewing angles is enhanced obviously, both theoretical and experimental results are proved that the luminance is about 5%~40% higher than previous when the viewing angle ranges from 30° to 60° correspondingly.
A real-time computer-generated moiré profilometry (CGMP) with adaptive filtering algorithm is proposed. In CGMP proposed previously, only one static sinusoidal grating needs to be projected onto the measured object and only one deformed pattern caused by the object needs to be captured, which is ideal for real-time three-dimensional (3-D) measurement. By means of generating moiré fringes between the captured deformed pattern and the prestored fringe patterns on the reference plane via computer, the 3-D shape of the measured object can be reconstructed successfully. In phase calculating, this method needs to extract the DC component by filtering. If filtering operation required manual intervention each time, its real-time measuring feature may be limited. For this, an adaptive filtering algorithm based on the maximum fundamental frequency component proportion evaluation function is proposed. It can automatically retrieve an object’s phase information according to the Fourier spectrum distributions of different measured objects without any manual intervention. Experimental results demonstrate the feasibility and validity of the real-time 3-D measuring application.
A real-time three-dimensional (3-D) shape measurement based on single-shot color binary fringe (CBF) projection is proposed. In the traditional 3-D shape measurement methods based on binary fringe projection, the duty cycle of the binary fringe is always set to 1/2, so as to approximate the sinusoidal fringe by defocusing projection. In the proposed method, the binary fringe with a duty cycle of 1/3 is introduced. It is found that although the duty cycle is not 1/2, a nearly unbroken sinusoidal fringe pattern can be extracted from the captured fringe pattern by a filtering operation in the spatial frequency domain. In order to realize real-time 3-D shape measurement, a composite CBF was designed, in which three monochromatic binary fringes share the same duty cycle of 1/3 but misaligned 1/3 periods one by one are encoded in red (R), green (G), and blue (B) channels. When this composite CBF is projected onto the measured object, only one color-deformed pattern (CDP) needs to be captured and three monochromatic sinusoidal deformed patterns with a phase-shifting of 2π / 3 one another can be extracted from the single-shot captured CDP. So the 3-D shape of the measured object can be reconstructed with three-step phase measuring profilometry. The experimental results show the feasibility and validity of the proposed method. It can either effectively avoid the color overlapping in traditional color sinusoidal fringe or avoid the grayscale nonlinearity of sinusoidal fringe caused by the effect of gamma.
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