CN112113516A - Color raster phase decomposition method - Google Patents
Color raster phase decomposition method Download PDFInfo
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- CN112113516A CN112113516A CN202010774161.1A CN202010774161A CN112113516A CN 112113516 A CN112113516 A CN 112113516A CN 202010774161 A CN202010774161 A CN 202010774161A CN 112113516 A CN112113516 A CN 112113516A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/25—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures by projecting a pattern, e.g. one or more lines, moiré fringes on the object
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
- G01B11/0608—Height gauges
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Abstract
The invention relates to a structured light technology, in particular to a color raster phase demodulation method, which comprises the following steps: mapping color to number according to the collected color grating to generate color code; solving a main value of the periodic stripe grating based on Fourier transform, completing main value enhancement optimization, analyzing a sinusoidal periodic grating signal through a frequency domain, filtering noise, and improving the adaptive capacity of the algorithm environment; analyzing the period of the main value and extracting a period line; calculating the grating period according to the period line, the color code and the main value; the phase is calculated using the period and the main value. The invention solves the defects of the traditional phase solution method, firstly avoids misleading of initial period errors to solution of other periods, and skillfully avoids error propagation; and compared with a black-white grating, the color grating reduces the acquisition noise of the camera and improves the robustness of the algorithm.
Description
Technical Field
The invention relates to a structured light technology, in particular to a color raster phase demodulation method.
Background
The phase can be calculated by a plurality of gratings in the current structured light technology, and the applicable scenes are static measurement, so that the single-grating phase-demodulation method has more application scenes and simple operation compared with the multi-grating phase-demodulation method, and has important significance for industrial landing and energized production and scientific research.
The traditional single-amplitude grating phase solution is mostly an iterative method, after a phase starting point is artificially selected, the next point is expanded one by one according to the adjacent period or the same period of the adjacent points, the method is only suitable for solving the smooth plane projection grating, and the influence on the image with the truncated grating, particularly on the grating with the truncated phase exceeding one period, is particularly great. Other solutions are mostly guidance methods, are developed one by one according to a guidance principle, use a large amount of time cost to exchange for precision, are improved in initial point positioning compared with the first method, but are not innovative in nature, still cannot get rid of error transmission, and do not support high concurrency.
Disclosure of Invention
In view of the problems in the prior art, the invention provides a color grating dephasing method, which solves the problems of low error conduction and efficiency of the traditional algorithm, the problems that the traditional algorithm is influenced by algorithm factors, and the measurement method can only be used in the environment that the measurement surface is smooth and static and a plurality of gratings are shot. The invention solves the problems, enhances the robustness of the algorithm, enriches the application environment of the algorithm, supports dynamic measurement, supports high concurrency and greatly improves the operation efficiency of the algorithm.
The specific technical scheme of the invention is as follows:
the experimental device comprises a monocular camera, a projector and a computer, wherein the projector is used for projecting a color grating image, the monocular camera is used for shooting the color grating image, the computer is used for calculating the phase, the camera is connected with the computer through a USB3.0 data line, the projector is connected with the computer through an HDMI connecting line, and the experimental device is characterized by comprising:
generating a camera image color code according to the color code;
encoding a color projection grating according to a pseudorandom sequence;
solving a main value of the periodic stripe grating based on Fourier transform;
extracting periodic lines according to the main value of the periodic stripe grating;
calculating the grating period according to the period lines, the color codes and the period stripe grating main values;
the phase is resolved according to the period and the period fringe grating principal value.
The above technical solution is further defined as follows:
optionally, the color projection grating is encoded according to a debruijn pseudorandom sequence.
Optionally, the color projection grating is encoded according to a debruijn pseudorandom sequence using three colors of red, green, and blue.
The color projection grating may encode 27 periods.
Optionally, color coding of the camera image is done using a color coding table.
Optionally, the main value of the periodic stripe grating is expressed by using a fourier transform formula as follows:
optionally, finding a point on the main value of the periodic stripe grating, querying color codes, recording colors, querying colors of two periods, recording colors, forming a random sequence by the three colors, corresponding to an actual period, traversing the main value of the periodic stripe grating, and solving to obtain the period.
The invention has the following beneficial effects:
1) compared with a black-and-white grating, the color grating is beneficial to the collection of a camera in natural light, and the robustness of the algorithm is improved;
2) the color grating solution phase uses a single picture, is used in a dynamic measurement environment, supports a mobile experiment and improves an algorithm essentially;
3) the color grating de-phasing algorithm supports high concurrency, greatly improves algorithm efficiency, saves time cost, supports real-time data processing, and enhances user experience;
4) the color grating solution phase avoids the transmission of error in a large range, which leads to the use of a large amount of error data;
drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that other drawings can be derived from them by a person skilled in the art without inventive effort.
FIG. 1 shows a detection flow diagram of an embodiment of the present invention;
FIG. 2 shows a schematic of the structure of an experiment of the present invention;
fig. 3 is a raster pattern.
Detailed Description
In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the following description is only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
As shown in fig. 1, the present invention includes:
step 1: and generating a camera image color code according to the color code.
The three colors of red, green and blue are digitally encoded, and an encoding basis is provided for image grating identification.
Step 2: the color projected sinusoidal grating is encoded according to a debruijn pseudorandom sequence.
Pseudo-random sequences are generated according to the following debruijn principle, and color projection sinusoidal gratings are generated according to a coding table.
The debruijn pseudorandom sequence B (k, n) is a cyclic sequence of k elements. All k elements of length n make up the sequence, occurring in its subsequence (in circular form), and only once.
Therefore, we generate a length-3 pseudorandom sequence using red, blue and green, where k is 3 and n is 3, and the period of the generated color projection sinusoidal grating is 27
And step 3: and solving the main value of the periodic fringe grating based on Fourier transform.
In 1983, m.takeda et al used fourier transform for measuring three-dimensional surface shapes of objects, and proposed fourier transform profilometry, which uses one-dimensional fast fourier transform for measuring three-dimensional surface shapes of structured light fields. The method comprises the steps of projecting a sinusoidal grating onto the surface of a measured object through a projection system, obtaining deformation stripes modulated by the height distribution of the object through a camera system, sending the deformation stripes into a computer through an image acquisition system for fast Fourier transform, filtering and inverse Fourier transform, and solving the height distribution information of the object.
Fourier transform formula:
assuming that the period is 2 pi and the number of nodes is N, h-2 pi/N.
And 4, step 4: and extracting the period line according to the main value.
The (0,2 pi) main value, i.e. wrapped phase, is obtained through step 3, and in order to calculate continuous phase information by unwrapping the wrapped phase, a periodic line of main value variation needs to be extracted.
And 5: and calculating the grating period according to the period line, the color code and the main value.
Finding a point on the main value, inquiring color codes, recording colors, inquiring colors of two periods, recording colors, forming a random sequence by three colors after inquiry, corresponding to an actual period, traversing the main value, and solving to obtain the period.
The algorithm is as follows:
taking a point a on the main value, taking a point a1 at a corresponding position on the periodic line, and recording the corresponding value of a on the color code if a1 is 1; if a1 is not equal to 1, in decision a, if a >0, look forward to take the previous value on the periodic line until the value is 1, otherwise look backward to record the corresponding value of a on the color code. If the last period of the image, or the first period, is the case where the periodic line cannot be found in the half period, the reverse search is required.
Then, based on the color of the two subsequent cycles, if 323, a lookup into the random code starts with a third number, so the point is in the third cycle.
And sequentially unfolding to obtain the period of the whole graph.
Step 6: the phase is resolved according to the period and the period fringe grating principal value.
And (4) sequentially unfolding according to the relation between the main value (wrapping phase) and the period of the periodic stripe grating to obtain the unfolding phase of the shooting grating.
In fig. 3, the code for blue is "1", the code for green is "2", and the code for red is "3". In the encoding example, if the three raster colors in the screenshot are green, green and red, the corresponding period code is "223", the 15 th period is found in the pseudorandom sequence period "313231233113332232111222121", 15 × 2 pi + a of phase unwrapping (a is the wrapping phase), and each point and the corresponding period are sequentially traversed to obtain the unwrapped phase of the whole graph.
In conclusion, the method solves the defects of the traditional phase solution method, firstly avoids misleading of errors in the initial period to solution in other periods, and skillfully avoids error propagation; and compared with a black-white grating, the color grating reduces the acquisition noise of the camera and improves the robustness of the algorithm.
Claims (7)
1. A color raster demodulation phase method, comprising:
generating a camera image color code according to the color code;
encoding a color projection grating according to a pseudorandom sequence;
solving a main value of the periodic stripe grating based on Fourier transform;
extracting a periodic line according to the main value;
calculating the grating period according to the period lines, the color codes and the period stripe grating main values;
the phase is resolved according to the period and the period fringe grating principal value.
2. The color raster demodulation phase method of claim 1, characterized in that: the color projection grating is encoded according to a debruijn pseudorandom sequence.
3. The color raster demodulation phase method of claim 2, characterized in that: and encoding the color projection grating by adopting red, green and blue colors according to the debruijn pseudo-random sequence.
4. The color raster demodulation phase method of claim 3, characterized in that: the period of the color projection grating is 27.
5. The color raster demodulation phase method of claim 1, characterized in that: and completing the color coding of the camera image by using the color coding table.
6. The color raster demodulation phase method of claim 1, characterized in that: the main value of the periodic stripe grating is expressed by a Fourier transform formula as follows:
7. the color raster demodulation phase method of claim 1, characterized in that: finding a point on the main value of the periodic stripe grating, inquiring color codes, recording colors, inquiring colors of two periods, recording colors, forming a random sequence by three colors, corresponding to an actual period, traversing the main value of the periodic stripe grating, and solving to obtain the period.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120008150A1 (en) * | 2010-04-23 | 2012-01-12 | Nikon Corporation | Autofocus system and method |
| CN102496167A (en) * | 2011-12-07 | 2012-06-13 | 天津理工大学 | Pseudo-color coding method for phase modulated digital image |
| CN105180904A (en) * | 2015-09-21 | 2015-12-23 | 大连理工大学 | High-speed moving target position and posture measurement method based on coding structured light |
| CN110057319A (en) * | 2019-02-20 | 2019-07-26 | 西安理工大学 | A kind of high speed three-dimensional measurement method of a wide range of reflectivity changes object |
| CN110398199A (en) * | 2019-07-05 | 2019-11-01 | 内蒙古能建数字信息科技有限公司 | A kind of track clearance detection method |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120008150A1 (en) * | 2010-04-23 | 2012-01-12 | Nikon Corporation | Autofocus system and method |
| CN102496167A (en) * | 2011-12-07 | 2012-06-13 | 天津理工大学 | Pseudo-color coding method for phase modulated digital image |
| CN105180904A (en) * | 2015-09-21 | 2015-12-23 | 大连理工大学 | High-speed moving target position and posture measurement method based on coding structured light |
| CN110057319A (en) * | 2019-02-20 | 2019-07-26 | 西安理工大学 | A kind of high speed three-dimensional measurement method of a wide range of reflectivity changes object |
| CN110398199A (en) * | 2019-07-05 | 2019-11-01 | 内蒙古能建数字信息科技有限公司 | A kind of track clearance detection method |
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