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By using the time-division multiplexing characteristics of the projector and the integral exposure characteristics of the charge coupled device (CCD) camera, a super-grayscale and real-time computer-generated Moiré profilometry based on video grating projection is proposed. The traditional digital static grating is of 256-grayscale at most. If an expected super-grayscale grating with a maximum grayscale of 766 is designed and divided into three 256-grayscale fringe patterns with balanced grayscale as far as possible, they can be synthesized into a repeated playing video grating instead of the traditional static grating. When the video grating is projected onto the measured object, as long as the exposure time is set to three times the refresh cycle of the video grating, the super-grayscale deformed patterns in the 766-grayscale can be captured with a 10-bit CCD camera, so that the deformed patterns are realistic. The digital error in computer-generated Moiré profilometry is effectively reduced. In addition, this method can expand the linear range of the deformed pattern by 20% in computer Moiré profilometry. Therefore, the proposed method has the perspectives of high accuracy and real-time measurement. Theoretical analysis and experimental results demonstrate the validity and capability of the proposed method.

A computer-generated moire profilometry based on flat image demodulation is proposed. A sinusoidal fringe pattern and its background light are modulated by two-frequency carrier fringes, respectively, to combine a composite grating. While this composite grating is projected onto the measured object, the composite deformed pattern can be captured by CCD camera. So the sinusoidal deformed pattern and its corresponding flat image can be demodulated from the composite deformed pattern. And the AC component of sinusoidal deformed pattern is calculated by the subtraction between the demodulated sinusoidal deformed pattern and the flat image. Compared with normal computer-generated moire profilometry, a more intact AC component can be obtained directly no matter how severe the frequency aliasing condition is. Meanwhile, the three-dimensional (3D) shape of object can be reconstructed only using this composite deformed pattern which shows the application in real-time measurement. Experimental results show the feasibility and validity of the proposed method.

A computer-generated moiré profilometry based on algebraic addition instead of algebraic multiplication is proposed. Firstly, the two AC components of the captured fringe patterns on the reference plane with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pi /2$$\end{document}π/2 phase difference are retrieved and saved in advance. While measuring, two sinusoidal gratings with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pi$$\end{document}π phase difference are projected onto the measured object alternatively, and the corresponding deformed patterns are captured. Then the AC component of the captured deformed pattern can be separated exactly. When the positive and negative AC component of the captured deformed pattern are added to the two prestored AC components respectively, two moiré fringes only reflect sine and cosine of the object’s phase information can be successfully generated via a series of data processing procedures. Finally, the phase distribution of the measured object can be extracted by arctangent of the ratio of these two moiré fringes. Compared with computer-generated moiré profilometry based on algebraic multiplication, this proposed method can reduce the effect of high frequency noise and residual DC component on measurement and improve the measurement accuracy. While compared with \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pi$$\end{document}π phase shifting FTP, this method can measure more complex objects with better measurement capability. Experimental results verify the feasibility and validity of the proposed method.

A single-shot phase measuring profilometry (PMP) based on color binary grating with intervals is proposed. In traditional PMP based on binary grating, the width for non-zero transmittance of the binary grating is always 1/2 periods rigorously. In our proposed method, a color binary grating is introduced in which three binary gratings with the same period and the same width for non-zero transmittance less than 1/3 periods are misaligned 1/3 periods one another and programmed in red (R), green (G) and blue (B) channels respectively. Because the widths for non-zero transmittance in R, G and B channels of the introduced color binary grating are all less than 1/3 periods and misaligned 1/3 periods one another, the color overlap can be avoided from the source. When measuring the object, only a single-shot deformed pattern needs to be captured and three nearly unbroken sinusoidal deformed patterns with an equivalent phase-shifting of 2 π ∕ 3 can be extracted from R, G and B components of the captured color deformed pattern. So the 3D shape of the measured object can be successfully reconstructed with three-step PMP. Experiment results show the feasibility of the proposed method. Due to its single-shot feature, it is promising to measure the dynamic objects.

Color phase-shifting fringe projection is one of the single-shot three-dimensional shape measurement techniques based on fringe projection profilometry. In practice, the nonlinearity and color crosstalk of the projector-camera system yield undesired phase errors when using phase-shifting algorithm. In this paper, an active phase error suppression method based on hue pre-correction is proposed. Theoretical analysis of phase error is performed taking account of the gamma nonlinearity of the camera. Based on the analysis, the distortion of hue component of the acquired color fringe pattern is employed to represent the overall phase error induced by the combined effect of nonlinearity and color crosstalk. In this method, the hue is pre-corrected to be linear by measuring the function of the combined effect and modifying the computer-generated hue according to the source-distorted relationship. Then, the new modified color fringe pattern can be generated and saved for the further measurement of objects. Experimental results demonstrate the feasibility of the proposed method and it can effectively suppress the induced overall phase error caused by the nonlinearity and color crosstalk of the projector-camera system.

An improved 2+1 phase-shifting algorithm based on the flat image fitting calibration is proposed. The 2+1 phase-shifting algorithm proposed by Zhang uses one uniform gray image whose gray is the same as the mean gray of the phase-shifting sinusoidal grating patterns instead of one of these grating patterns in traditional three-step phase measuring profilometry to reduce measuring error caused by motion. It maintains that the light intensity distribution of captured flat image is equal to the dc component of the captured phase-shifting deformed patterns. But extensive experimental results show that there is a certain inconsistency between the light intensity distribution of the captured flat image and the dc component of the deformed patterns. It will bring some nonnegligible errors. So a calibration procedure is introduced before measuring to obtain a calibration coefficient between the captured flat image and the dc component of the captured fringe pattern by the least squares fit. While measuring, the veritable dc component of the captured deformed pattern is extracted by just multiplying the calibration coefficient with captured flat image. Thus, the above nonnegligible errors can be effectively improved. Furthermore, the proposed algorithm is more flexible because its shifting-phase is no longer fixed to be π /2 but optional. The experimental results show the effectiveness and practicability of the improved 2+1 phase-shifting algorithm.

A color-coded computer-generated Moire 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.

The three-dimensional reconstruction in phase-measuring profilometry (PMP) usually involves the phase error caused by the gamma effect of the projector. In this study, the relationship between the ...

A three-dimensional measurement method based on frequency-carrier computer-generated moire fringe is proposed. By projecting two sinusoidal gratings with π phase difference each other onto the measured object respectively and capturing the corresponding deformed patterns, the AC component of the deformed pattern can be extracted. When this AC component is respectively multiplied by actively designed computer-generated sinusoidal grating and cosinoidal grating with the same frequency, two new fringes containing frequency-carrier moire components can be obtained. After low-pass filtering, the frequency-carrier moire fringes can be extracted to achieve object’s phase retrieval. As long as the DC component of the actively designed sinusoidal grating and cosinoidal grating are all controlled to be zero, the effect of inaccuracy elimination of the deformed pattern’s background light component on measuring accuracy can be reduced evidently. The frequency of the actively designed grating can be determined as 1/4 lines per pixel to ensure the maximum distance between each adjacent spectrum peaks of the new generated fringe so as to get the best measurement effect. The proposed method has good application ability in the limited number of projection frames and other scenes, and can achieve high measurement accuracy by projecting only two fringe patterns. Experimental results verify the feasibility and validity of the proposed method.

In order to explore the feasibility of the application of natural lighting technology in industrial buildings and the energy saving potential, through simulation, We will compare and analyze the change of indoor light environment and energy consumption in cigarette factory joint workshops under the scheme of increasing the skylight’s quantity or change the material of skylight roof, and aim to provide the proposal of the lighting products’ performance parameters. The results show that the optimized joint workshops’ daylight factor, uniformity and illumination all meet requirements of the standard and create a more comfortable light environment. The optimized joint workshops’ lighting energy consumption for the whole year decreases 201.7MWh, air conditioning energy consumption increases 1.1MWh, and the total energy consumption of the building reduce 200.6MWh.

An improved computer-generated moiré profilometry (CGMP) with flat image calibration is proposed. In CGMP, the purification of the AC component plays a decisive role. While a composite grating modulated with both the sinusoidal grating and its background light substitutes for the sinusoidal grating itself, the sinusoidal deformed pattern and flat image can be demodulated from the captured pattern. It is found that the sinusoidal deformed pattern and flat image may deviate, which is caused by ambient light. So flat image calibration is conducted to obtain a purer AC component that can effectively suppress the influence of ambient light and ensure the measurement accuracy, even if spectrum aliasing exists. Experimental results show the feasibility and validity of the proposed method.

In traditional composite-structured-light profilometry, the N-frame carrier gratings and modulated phase-shifting sinusoidal gratings must share a 256-greyscale dynamic range, which is the standard for commercial digital light projectors (DLPs). Additionally, each of the demodulated phase-shift gratings must possess a 43-greyscale dynamic range. This decreases the greyscale dynamic range for each of the demodulated gratings and compresses the phase information. Consequently, measurement accuracy is a challenge, even for incomplete reconstructions. To solve this problem, we propose a new composite-structured-light profilometry using greyscale expansion. Specifically, a composite video is synthesised using three different purposefully designed patterns, each possessing a 256-greyscale dynamic range. These patterns are used as the composite-structured-light to replace the traditional static composite grating. After projecting the repetitive video onto a measured object and controlling the exposure time of the charge-coupled device camera, the deformed composite 766-greyscale pattern can be stably captured. Furthermore, after demodulation, the dynamic range of the deformed demodulated patterns can be expanded up to 229. Numerical and experimental results indicate that the proposed method can be used to divide the single 256-greyscale DLP standard and accurately reconstruct measured objects.

A dynamic phase measuring profilometry (PMP) based on tricolor binary fringe combined time-division multiplexing principle is proposed. Only one tricolor binary fringe combined by red (R), green (G), and blue (B) binary fringes with the same fringe width but without any color overlapping one another is needed and sent into the flash memory of a high-speed digital light projector (HDLP) in advance. A specialized time-division multiplexing timing sequence is designed to control the HDLP to project the tricolor binary fringe saved in the flash memory onto the measured dynamic object separately and sequentially at 234 fps, at the same time, the projected light source mode is set as monochrome mode which means that all the RGB LEDs remain lighting. Meanwhile, it also triggers a high frame rate monochrome camera synchronized with the HDLP to capture the corresponding deformed patterns in R, G and B channels. By filtering, the nearly unbroken phase-shifting sinusoidal deformed patterns for three-step PMP can be extracted from the captured deformed patterns. It is equivalent to the three-dimensional (3D) shape reconstruction of the measured dynamic object at 78 fps. Experimental results verify the feasibility and the validity of the proposed method. It is effective for measuring the dynamic object and can avoid the color cross-talk effectively.

A real-time computer-generated moire 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 moire 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.

Recently, a computer-generated moiré profilometry was proposed by our research group. It can effectively avoid the influence of the transient caused by moiré fringes’ direct acquisition and generally owns a higher accuracy. But when the spatial spectrum of the captured deformed pattern is severely aliased caused by the measured object, the accuracy of this method may be affected to some extent due to the impure background light component extraction. So, a high precision computer-generated moiré profilometry based on background light component’s accurate elimination is proposed. By adding an additional special phase-shifting sinusoidal grating to accurately extract valid information in the spatial domain and improve the sinusoidal feature of the pattern, the measurement precision can be improved effectively. Though the single-shot feature is broken, the real-time measuring feature is still maintained successfully. Experimental results show the feasibility and validity of the proposed method.

A new 3D measuring method based on computer-generated moire fringes is proposed. The two AC components of the 0-degree and 90-degree phase-shifted fringe patterns on reference plane are prepared in advance. While the AC component of the single-shot deformed pattern is multiplied by the two prepared AC components, respectively, two computer-generated moire fringes can be retrieved. The ratio of the two computer-generated moire fringes is just the tangent of the phase modulated by the object. It is of great potential in real-time or even dynamical 3D measurement due to its single-shot deformed pattern feature, and it avoids the influences of the object's reflectivity simultaneously. Compared to the Fourier transform profilometry, its error is smaller due to its higher first-order spectrum. Experimental results show the feasibility and validity of the proposed method.

An orthogonal modulated computer-generated moire profilometry is proposed. Only one composite grating in which two sinusoidal fringe patterns with a π phase difference are modulated by two other orthogonal sinusoidal fringe patterns with different frequencies respectively is projected on the object. While a single-shot deformed composite pattern is captured, the two sinusoidal deformed patterns with a π phase difference are demodulated from the deformed composite pattern. The AC component of deformed pattern is calculated by subtraction of the two demodulated deformed patterns. If this AC component of deformed pattern is respectively multiplied by the two AC components of fringe patterns of reference plane with a π ∕ 2 phase difference prepared and saved in computer in advance, two computer generated moire fringes which just respectively stand for sine and cosine of phase modulated by the height of the object relative to the reference plane are extracted. The tangent of the modulated phase is obtained by the ratio of these two moire fringes. So the three-dimensional (3D) shape of object can be reconstructed using only one deformed composite pattern. Both simulation and experimental results demonstrate the feasibility and validity of the proposed method. It has potential in real-time 3D measurement due to its single-shot feature.

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.