CN102798354A - Binary stripe stack based sinusoidal grating generation method - Google Patents

Abstract

The invention discloses a binary stripe stack based sinusoidal grating generation method. The method provided by the invention comprises the following steps of: firstly generating a sinusoidal grating picture, and decomposing one sinusoidal grating picture into 8 binary pictures through a binary method, wherein each point of each binary picture represents a bit of each point of the original sinusoidal grating after binary, and the value only can be 1 or 1; and through projecting the 8 binary pictures, finally combining the 8 binary pictures into one sinusoidal grating picture. Through the method provided by the invention, a composite plane sinusoidal grating protecting picture E can be obtained, the range of the pixel value of each point of the projecting picture E is from 0 to 255, and is in sinusoidal distribution, and thus errors caused by the nonlinear response of a projector and a camera can be prevented.

Description

Sinusoidal grating generation method based on the stack of scale-of-two striped

Technical field

The invention belongs to projector and camera nonlinear response association area.Relate to the synthetic problem of sine streak grating.Be specially a kind of sinusoidal grating generation method based on the stack of scale-of-two striped.

Background technology

Optical three-dimensional measurement has widespread use in various fields such as industry detection automatically, production quality control, reverse engineer, biomedicine, virtual reality, the reproduction of the cultural relics, anthropological measuring.This huge application demand has been impelled the fast development of multiple optical measuring technique.Along with computer technology, digital picture are obtained the development of equipment and optical device, and a lot of three dimensional optical measuring technology have got into the stage of ripeness of commercial application, are also continuing to bring out with stylish method for three-dimensional measurement.Have noncontact, high precision, characteristics such as high-speed based on the optical 3-dimensional surface shape measurement method of fringe projection, be widely used in fields such as machine vision, the detection of face shape, profiling in kind, production quality control, biomedicine.

The measuring error of structured light measurement system has two main sources: phase displacement error and nonsinusoidal waveform error.Phase displacement error is because due to phase shift step pitch inaccurate, it usually is inevitably, but can the real-time phase shift correction technology of employing reduces in accurate phase changer and the measuring process through adopting.Along with the development of digital display technique, business-like digital projector (DLP) is used widely in structured light measurement system.Digital projector projection grating can be eliminated phase displacement error; But because design reasons; Projector and camera all have the character of gray scale nonlinear distortion, make that taking the sinusoidal grating projected fringe that obtains does not have good sine property, can bring phase error to measurement thereupon.The nonlinear distortion that projector has is called gradation distortion, and the input and output that are projector present the exponential function response relation.Gradation distortion will become the principal element that influences the measuring system measuring accuracy.

The existing method that reduces the non-linear measuring error that causes of gamma comprises: it is non-linear to utilize mathematical method directly to handle gamma; Increase the phase shift step number and reduce error; Adopt look-up table to preestablish error; Based on the spline curve fitting method.These methods can improve measuring accuracy greatly, but also have some defectives: the spline-fitting method need be through iteration repeatedly when phase calculation, and operand is bigger; Increase the increase that the phase shift step number means projection image quantity; Look-up table needs the plenty of time in the process of labeling projection appearance gamma value.The present invention proposes a kind ofly to this problem, solve nonlinear problem based on binary pattern.

Summary of the invention

The technical matters that solves

For solving the problem that prior art exists, the present invention proposes a kind of sinusoidal grating generation method based on the stack of scale-of-two striped.Can overcome projector and camera nonlinear response and theoretical scale-of-two picture stack generated sinusoidal grating through binary law.

Technical scheme

The present invention at first generates a sinusoidal grating picture, again through binary method, 1 sinusoidal grating picture is decomposed into 8 scale-of-two pictures.According to binary decomposition principle, each point of the former sinusoidal grating of each some representative of every binary picture carries out a position behind the scale-of-two, and value can only be 0 or 1.Through 8 scale-of-two pictures of projection, 8 scale-of-two pictures synthesize sinusoidal grating pictures the most at last.

Technical scheme of the present invention is:

Said a kind of sinusoidal grating generation method based on the stack of scale-of-two striped is characterized in that: may further comprise the steps:

Step 1: the sinusoidal grating striped picture A that generates at least two cycles;

Step 2: according to the scale-of-two reconstruction formula:

$I(x,y)=\underset{i=1}{\overset{8}{\mathrm{\Σ}}}{2}^{(8-i)}{M}_i(x,y)$

Sinusoidal grating striped picture A reconstruct is decomposed into 8 scale-of-two picture { M _i(i=1,2 ..., 8), wherein (x, the y) coordinate figure of pixel among the expression picture A, I (x, the y) gray-scale value of expression sinusoidal grating picture A each point, M _iThe scale-of-two picture that expression reconstruct obtains, 8 scale-of-two pictures are formed set of pictures B; At scale-of-two picture M _iIn, work as M _i(x, y)=0 o'clock, (x, gray-scale value y) is 0 to this point, works as M _i(x, y)=1 o'clock, (x, gray-scale value y) they are 255 to this point;

Step 3: every scale-of-two picture among the set of pictures B is projected on the testee respectively, and take the projection image on the testee respectively through the CCD camera, obtain 8 projection images, 8 projection images are formed set of pictures C; Utilize big Tianjin threshold method that every projection image among the set of pictures C is done binary conversion treatment, 8 scale-of-two pictures that obtain after the processing are formed set of pictures D;

Step 4: 8 scale-of-two pictures among the set of pictures D are carried out reverse overlap-add procedure according to the scale-of-two reconstruction formula in the step 2, thereby obtain the sinusoidal grating image E of generation.

Said a kind of sinusoidal grating generation method based on the stack of scale-of-two striped, it is characterized in that: the angle of the shooting visual angle of CCD camera and projector optical axis is 20 ° ~ 40 ° in the step 3.

Beneficial effect

Can obtain the plane sinusoidal grating projection image E that opening and closing become through the present invention, the scope of the pixel value of projection image E each point is 0 to 255, and becomes Sine distribution, thereby has avoided the nonlinear response of projector and camera and the error that causes.

Description of drawings

Fig. 1 is sinusoidal grating figure.

Fig. 2 (a) obtains the sine streak raster pattern for through the projection camera plane.

Fig. 2 (b) is an image middle line intensity profile situation map.

The picture of Fig. 2 (c) for obtaining after the Fast Fourier Transform (FFT).

Fig. 3 is 8 binary pictures and corresponding sinusoidal grating figure.

Fig. 4 (a) is after taking 8 binary pictures, synthetic sine streak raster pattern.

Fig. 4 (b) is an image middle line intensity profile situation map.

The figure of Fig. 4 (c) for obtaining after the Fast Fourier Transform (FFT).

Embodiment

Below in conjunction with specific embodiment the present invention is described:

Based on the sinusoidal grating generation method of scale-of-two striped stack, may further comprise the steps in the present embodiment:

Step 1: the sinusoidal grating striped picture A that generates at least two cycles; Shown in accompanying drawing 1, the generation one-period is 3 sinusoidal grating striped picture A in the present embodiment.

In order to compare; (model C P270 BenQ) projects to standard sine grating picture on the testee, takes the projection image on the testee through CCD camera (model MVD-500SM) to use resolution to be set to the projector of 1024*768; Obtaining resolution is the 1024*768 projection image; Shown in accompanying drawing 2 (a), wherein the angle of the shooting visual angle of camera and projector optical axis is 20 ° ~ 40 °, gets 30 ° in the present embodiment.In order to contrast, get the intensity profile of middle row, shown in accompanying drawing 2 (b), and picture carried out Fast Fourier Transform (FFT), the result is shown in accompanying drawing 2 (c).

Step 2: according to the scale-of-two reconstruction formula:

$I(x,y)=\underset{i=1}{\overset{8}{\mathrm{\Σ}}}{2}^{(8-i)}{M}_i(x,y)$

Sinusoidal grating striped picture A reconstruct is decomposed into 8 scale-of-two picture { M _i(i=1,2 ..., 8), wherein (x, the y) coordinate figure of pixel among the expression picture A, I (x, the y) gray-scale value of expression sinusoidal grating picture A each point, M _iThe scale-of-two picture that expression reconstruct obtains, M _iIn i represent binary position, M _i(x, value y) is 0 or 1; 8 scale-of-two pictures are formed set of pictures B; At scale-of-two picture M _iIn, work as M _i(x, y)=0 o'clock, (x, gray-scale value y) is 0 to this point, works as M _i(x, y)=1 o'clock, (x, gray-scale value y) they are 255 to this point; Sinusoidal grating striped picture A resolves into 8 binary images shown in accompanying drawing (3);

Step 3: use resolution to be set to projector (the model C P270 of 1024*768; BenQ) project to every scale-of-two picture among the set of pictures B on the testee respectively; And take the projection image on the testee respectively through CCD camera (model MVD-500SM), and obtaining resolution is 8 projection images of 1024*768,8 projection images are formed set of pictures C; Wherein the angle of the shooting visual angle of camera and projector optical axis is 20 ° ~ 40 °, gets 30 ° in the present embodiment.Utilize big Tianjin threshold method that every projection image among the set of pictures C is done binary conversion treatment, 8 scale-of-two pictures that obtain after the processing are formed set of pictures D;

Step 4: 8 scale-of-two pictures among the set of pictures D are carried out reverse overlap-add procedure according to the scale-of-two reconstruction formula in the step 2, thereby obtain the sinusoidal grating image E of generation, shown in accompanying drawing 4 (a).In order to compare, get the intensity profile of middle row, shown in accompanying drawing 4 (b), and picture carried out Fast Fourier Transform (FFT), the result is shown in accompanying drawing 4 (c).

The image of the sinusoidal grating that the sinusoidal grating image through contrast standard and 8 scale-of-two picture stacks generate can be found clearly that the pixel value that adopts the scale-of-two picture to handle each point in the sinusoidal grating image that generates is 0 to 255, and become Sine distribution.And directly the pixel minimum of the sinusoidal grating image each point of projection is not 0, and does not become Sine distribution.Institute of the present invention elaboration method has overcome the non-linear corresponding problem of projector and camera.

Claims (2)

1. sinusoidal grating generation method based on scale-of-two striped stack is characterized in that: may further comprise the steps:

Step 1: the sinusoidal grating striped picture A that generates at least two cycles;

Step 2: according to the scale-of-two reconstruction formula:

$I(x,y)=\underset{i=1}{\overset{8}{\mathrm{\Σ}}}{2}^{(8-i)}{M}_i(x,y)$

Sinusoidal grating striped picture A reconstruct is decomposed into 8 scale-of-two picture { M _i(i=1,2 ..., 8), wherein (x, the y) coordinate figure of pixel among the expression picture A, I (x, the y) gray-scale value of expression sinusoidal grating picture A each point, M _iThe scale-of-two picture that expression reconstruct obtains, 8 scale-of-two pictures are formed set of pictures B; At scale-of-two picture M _iIn, work as M _i(x, y)=0 o'clock, (x, gray-scale value y) is 0 to this point, works as M _i(x, y)=1 o'clock, (x, gray-scale value y) they are 255 to this point;

Step 3: every scale-of-two picture among the set of pictures B is projected on the testee respectively, and take the projection image on the testee respectively through the CCD camera, obtain 8 projection images, 8 projection images are formed set of pictures C; Utilize big Tianjin threshold method that every projection image among the set of pictures C is done binary conversion treatment, 8 scale-of-two pictures that obtain after the processing are formed set of pictures D;

Step 4: 8 scale-of-two pictures among the set of pictures D are carried out reverse overlap-add procedure according to the scale-of-two reconstruction formula in the step 2, thereby obtain the sinusoidal grating image E of generation.

2. according to the said a kind of sinusoidal grating generation method based on the stack of scale-of-two striped of claim 1, it is characterized in that: the angle of the shooting visual angle of CCD camera and projector optical axis is 20 ° ~ 40 ° in the step 3.

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