Projection parallel single-pixel measurement method based on time multiplexing coding

Abstract

The invention discloses a projection parallel single-pixel measurement method based on time multiplexing coding, which comprises the following steps of: circularly projecting a sequence diagram consisting of a full-white pattern, a full-black pattern and a four-step phase shift substrate fringe pattern to an object to be measured by using a projector, and synchronously shooting the object to be measured by using a camera; then, background light intensity and spectrum coefficients are calculated for a full white pattern and a full black pattern which are close to each other on the projection sequence; and finally, Fourier single-pixel imaging is performed on image pixels shot by all cameras in parallel. According to the time multiplexing parallel single-pixel coding method, the coding pattern is multiplexed on the time sequence while the effectiveness of parallel single-pixel measurement is ensured, so that the number of projection patterns can be reduced, and the coding efficiency is greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of computer vision three-dimensional measurement calculation, and in particular relates to a projection parallel single-pixel measurement method based on time multiplexing coding. Background Art

[0002] In recent years, parallel single-pixel measurement technology, with its advantages of high adaptability and high signal-to-noise ratio, can achieve highly adaptable three-dimensional reconstruction for complex lighting and reflection scenes in areas such as diffuse reflection, specular reflection, dark areas, sub-surface scattering and mutual reflection, and has begun to be increasingly widely used in the field of computer vision measurement and calculation.

[0003] With the rapid development of computer technology and the continuous updating of projection and imaging devices, parallel single-pixel measurement technology has been extended to high-speed dynamic three-dimensional scenes. However, existing methods still require at least hundreds of projections of base patterns to complete a measurement of the object to be measured, and the reconstruction efficiency is low. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a projection parallel single-pixel measurement method based on time multiplexing coding.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve the technical problem is: a projection parallel single-pixel measurement method based on time multiplexing coding, comprising the following steps:

[0006] S1, use a projector to cyclically project a full white pattern I onto the object to be measured. W 、All black pattern I B The camera synchronously captures the pattern of the object to be measured.

[0007] S2, for the all-white pattern I that is similar in the projection sequence W And all black pattern I B Calculate the background light intensity;

[0008] S3, assisting in calculating the spectrum coefficient according to the calculated background light intensity;

[0009] S4, for all image pixels captured by the camera (u c ,v c ) performs Fourier single-pixel imaging in parallel.

[0010] Furthermore, in step S1, the following formula is used to generate a four-step phase-shifted base fringe pattern:

[0011]

[0012] The fringe frequencies and directions of the phase-shifted fringes in the four-step phase-shifted base fringe pattern are different, corresponding to different spectral coefficients in Fourier single-pixel imaging According to the order of I1, I2 or I3, I4 and the spectral coefficients, the sequence S of the four-step phase-shifted base fringe pattern is cyclically arranged:

[0013]

[0014] The above two fringe combinations I1, I2 or I3, I4 can be selected as one, and the sequence S corresponds to N different coefficients under the same spectrum. Next, turn the all-white pattern I W And all black pattern I B Insert the beginning and end of sequence S to form a circular sequence: I W S1I B S2I W S3I B ... and cyclically project the sequence graph onto the object to be measured.

[0015] Furthermore, the step S2 comprises: in the acquired image sequence, each combination I W S i I B or I B S i I W A three-dimensional result can be calculated; when calculating the spectral coefficient, S i The white and black patterns adjacent to each other on the left and right are averaged to extract the background light intensity. For the spectrum coefficient numbered n, calculate the background light intensity A(u c ,v c ,i,n) and then use the unit with the same frequency The two fringe patterns can be used to calculate the spectral coefficients

[0016]

[0017] The spectrum coefficients are calculated in sequence according to the sampling path and filled into the spectrum. Finally, the reconstructed spectrum is imaged by inverse Fourier transform. The intensity distribution of the image reflects the image pixel (u c ,v c ) corresponds to the energy of the entire projector plane, that is, which positions on the projector target surface the energy received by the current point comes from.

[0018] The beneficial effect of the present invention is that the present invention uses a time-multiplexed parallel single-pixel encoding method to ensure the effectiveness of parallel single-pixel measurement while multiplexing encoding patterns in a time series, thereby reducing the number of projection patterns and greatly improving encoding efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a flow chart of the traditional parallel single-pixel measurement method;

[0020] Figure 2 This is a flow chart of the parallel single-pixel measurement method based on time multiplexing of the present invention;

[0021] Figure 3 Schematic diagram of projection pattern sequence of the parallel single-pixel measurement method based on time multiplexing of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described below with reference to the accompanying drawings and embodiments.

[0023] The general process of parallel single-pixel 3D measurement is as follows: Figure 1 As shown:

[0024] S1, use a projector to cyclically project a full white pattern I onto the object to be measured. W 、All black pattern I B The camera synchronously captures the pattern of the object to be measured.

[0025] S2, uses Fourier single-pixel imaging for all image pixels captured by the camera;

[0026] S3, extracting pixel coordinates of direct illumination components on each imaging plane using epipolar constraint and gray value centroid method;

[0027] S4, converts the pixel coordinates into point clouds through system calibration.

[0028] The above measurement method is to first project a series of Fourier basis fringe patterns, and then use a camera to capture the projected image at a certain angle to the projection direction; each pixel on the camera target surface is regarded as a single pixel detector, and as the projection basis pattern is switched, a single pixel point (u c ,v c ) will receive the corresponding changing light intensity. Further, according to the Fourier single pixel method, two-dimensional single pixel imaging is performed on each pixel point on the camera target surface. The intensity distribution of the image reflects the camera pixel (u c ,v c ) and the energy correspondence of the entire projector plane, that is, the current point (u c ,v c )Which positions on the projector target surface the energy received comes from.

[0029] Further applying epipolar constraints on the imaging surface can determine the pixel (u c ,v c ) Received illumination components: Select the direct illumination component (ud ,v d ), and the interfering indirect lighting component (u id ,v id ); Using the grayscale centroid method, we can further determine (u d ,v d ) pixel position; then through the system calibration conversion, the camera pixel (u c ,v c )-projector plane point (u d ,v d )-world coordinates (X, Y, Z). By performing the above single-pixel imaging, direct illumination component positioning, and coordinate transformation in parallel on all pixel points on the camera target surface, a complete three-dimensional point cloud of the object can be obtained.

[0030] Reference Figure 2 As shown, the present invention discloses a projection parallel single-pixel measurement method based on time multiplexing coding, which includes the following steps.

[0031] S1, use a projector to cyclically project a full white pattern I onto the object to be measured. W 、All black pattern I B The camera synchronously captures the pattern of the object to be measured, which is composed of a sequence diagram consisting of a four-step phase-shifted base fringe pattern.

[0032] This step uses the following formula to generate a four-step phase-shifted base fringe pattern.

[0033]

[0034] The fringe frequencies and directions of the phase-shifted fringes in the four-step phase-shifted base fringe pattern are different, corresponding to different spectral coefficients in Fourier single-pixel imaging According to the order of I1, I2 or I3, I4 and the spectral coefficients, the sequence S of the four-step phase-shifted base fringe pattern is cyclically arranged:

[0035]

[0036] The above two fringe combinations I1, I2 or I3, I4 can be selected as one, and the sequence S corresponds to N different coefficients under the same spectrum. Next, turn the all-white pattern I W And all black pattern I B Insert the beginning and end of sequence S to form a circular sequence: I W S1I B S2I W S3I B ... and cyclically project the sequence graph onto the object to be measured.

[0037] S2, for the all-white pattern I that is similar in the projection sequence WAnd all black pattern I B Calculate the background light intensity; for example, black s white s black s white, the first all black and the first all white are counted as the background light intensity, but the second white is not used.

[0038] In this step, in the acquired image sequence, each combination I W S i I B or I B S i I W A three-dimensional result can be calculated; when calculating the spectral coefficient, S i The white and black patterns adjacent to each other on the left and right are averaged to extract the background light intensity. For the spectrum coefficient numbered n, calculate the background light intensity A(u c ,v c ,i,n) and then use the unit with the same frequency The two fringe patterns can be used to calculate the spectral coefficients

[0039]

[0040] The spectrum coefficients are calculated in sequence according to the sampling path and filled into the spectrum. Finally, the reconstructed spectrum is imaged by inverse Fourier transform. The intensity distribution of the image reflects the image pixel (u c ,v c ) corresponds to the energy of the entire projector plane, that is, which positions on the projector target surface the energy received by the current point comes from.

[0041] S3, assisting in calculating the spectrum coefficient according to the calculated background light intensity.

[0042] S4, for all image pixels captured by the camera (u c ,v c ) performs Fourier single-pixel imaging in parallel.

[0043] Compared with the parallel single-pixel 3D measurement method in the prior art, the three-step phase shift encoding method with the least number of patterns, the measurement method of the present invention can calculate the spectrum coefficient of a frequency using only two fringe patterns while retaining the measurement effectiveness, greatly compressing the redundancy in the encoding (only retaining 2 / 3 of the patterns of the original method), and improving the measurement efficiency by 33%. The schematic diagram of the projection pattern sequence is shown in Figure 3 shown.

[0044] The above embodiments are only illustrative of the principles and effects of the present invention, as well as some embodiments of its application. For those skilled in the art, several modifications and improvements may be made without departing from the creative concept of the present invention, and all of these belong to the protection scope of the present invention.

Claims

1. A projection parallel single pixel measurement method based on time multiplexing coding, characterized in that: The following steps are included S1, use a projector to cyclically project a full white pattern I onto the object to be measured. W 、All black pattern I B The camera synchronously photographs the object to be measured by using a sequence diagram consisting of a four-step phase-shifted base fringe pattern; S2, for the all-white pattern I that is similar in the projection sequence W And all black pattern I B Calculate the background light intensity; S3, calculating the spectrum coefficient according to the calculated background light intensity; S4, for all image pixels captured by the camera (u c ,v c ) performs Fourier single-pixel imaging in parallel.

2. The method for projected parallel single-pixel measurement based on time multiplexing coding according to claim 1, characterized in that: In step S1, the following formula is used to generate a four-step phase-shifted base fringe pattern: The fringe frequencies and directions of the phase-shifted fringes in the four-step phase-shifted base fringe pattern are different, corresponding to different spectral coefficients in Fourier single-pixel imaging According to the order of I1, I2 or I3, I4 and the spectral coefficients, the sequence S of the four-step phase-shifted base fringe pattern is cyclically arranged: Select one of the above two fringe combinations I1, I2 or I3, I4, and the sequence S corresponds to N different coefficients under the same spectrum. Sequentially change the all-white pattern I W And all black pattern I B Insert the beginning and end of sequence S to form a circular sequence: I W S1I B S2I W S3I B ... and cyclically project the sequence graph onto the object to be measured.

3. A projection parallel single pixel measurement method based on time multiplexing coding according to claim 1 or 2, characterized in that: The step S2 comprises: in the acquired image sequence, each combination I W S i I B or I B S i I W Calculate a three-dimensional result; use S to calculate the spectral coefficients i The white and black patterns adjacent to each other are averaged to extract the background light intensity A(u c ,v c ,i,n): For the spectrum coefficient numbered n, calculate the background light intensity A(u c ,v c ,i,n) and then use Calculate the spectral coefficients of the two fringe patterns The spectrum coefficients are calculated sequentially according to the sampling path and filled into the spectrum, and finally the reconstructed spectrum is imaged by inverse Fourier transform.

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