Spectral polarization depth camera based on double-spatial light modulator coding light source and stripe phase shift

Abstract

The invention discloses a spectral polarization depth camera based on a double-spatial light modulator coding light source and stripe phase shift, which belongs to the technical field of spectral light field depth imaging and comprises a light source module, an information compression module, a polarization modulation module and an image acquisition and processing module. Wherein the light source module is used for generating parallel light beams in a specific spectral range, the information compression module is used for spectrum and space coding, the polarization modulation module is used for separating polarization information of the light beams, and the image acquisition and processing module is used for receiving and processing the information. By means of the high-speed coding capacity of the spatial light modulator, seven-dimensional light field information of a target can be efficiently collected and reconstructed at the same time, and the seven-dimensional light field information comprises a two-dimensional space # imgabs0 #, a one-dimensional spectrum # imgabs1 #, a one-dimensional depth # imgabs2 # and a three-dimensional polarization # imgabs3 #.

Description

Technical Field

[0001] The patent of this invention belongs to the field of spectral light field depth imaging technology, and specifically relates to a spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift. Background Art

[0002] In recent years, with the continuous development of environmental monitoring, resource exploration, medical imaging and remote sensing, higher requirements have been placed on efficient and accurate imaging technology. Traditional imaging technology often relies on single optical information, such as two-dimensional images or limited spectral information, which cannot meet the needs of comprehensive analysis of target objects. Especially in complex scenes, such as surfaces with strong scattering and strong reflection, traditional imaging technology is difficult to efficiently obtain surface information while maintaining high resolution. This limitation makes traditional imaging methods face challenges in dealing with target identification and surface detail restoration in complex environments.

[0003] In order to deal with these problems, the concept of spectral-depth-polarization fusion imaging has emerged in recent years. This technology can provide more comprehensive multi-dimensional information about the target object by jointly collecting and processing the spectral, depth and polarization information of the object. This not only improves the spatial resolution and spectral resolution of imaging, but also solves the imaging problem in complex scenes to a certain extent. However, fusion imaging systems usually require synchronous acquisition of multi-dimensional information, such as spectral encoding, depth information extraction and polarization modulation. These operations often require multiple acquisitions of images under different conditions, resulting in a huge amount of data, which poses challenges to data storage and real-time processing. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift. The system uses a spatial light modulator and a partitioned polarizer to simultaneously acquire the spectrum, depth and polarization information of the target with high dynamics, thereby achieving multi-dimensional imaging.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The invention discloses a spectral polarization depth camera based on a dual spatial light modulator coded light source and fringe phase shift, which is characterized by comprising: a light source module, an information compression module, a polarization modulation module, and an image acquisition and processing module.

[0007] Furthermore, the light source module includes a light source, a collimating lens and a broadband filter.

[0008] Furthermore, the information compression module includes a first dispersive element, a first focusing lens, a first spatial light modulator, a second focusing lens, a second dispersive element, a third focusing lens, and a second spatial light modulator; the first dispersive element and the second dispersive element have the same size, shape, and dispersion performance; preferably, the spatial light modulator is a digital micromirror device.

[0009] Furthermore, the polarization modulation module includes a corner cube prism and a four-partition polarizer; the four areas of the four-partition polarizer correspond to a horizontal linear polarizer, a vertical linear polarizer, a 45° linear polarizer, a 1 / 4 wave plate with a horizontal fast axis, and a coaxial 45° linear polarizer.

[0010] Furthermore, the image acquisition and processing module includes a fourth focusing lens, an imaging detector, and a computer; the computer is connected to the first spatial light modulator, the second spatial light modulator, and the imaging detector, and is used to collect and process image information and restore seven-dimensional information of the target.

[0011] In order to solve the problems existing in the above-mentioned prior art, the present invention further discloses:

[0012] The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift includes the following steps:

[0013] S1, using a light source module to generate a parallel light beam with a specific spectral range.

[0014] S2, using an information compression module to perform spectral and spatial encoding on the parallel light beam in sequence.

[0015] S3, using a polarization modulation module to separate the polarization information of the light beam.

[0016] S4, using the imaging detector in the image acquisition and processing module to collect image information, the computer restores the seven-dimensional information of the target, the depth information is obtained by the phase shift fringe technology, and the spectrum information is restored by the compressed sensing technology.

[0017] Furthermore, in step S1, the light source generates a light intensity distribution of of light beams.

[0018] Furthermore, in step S2, after the parallel light beam is dispersed by the first dispersion element, it is focused by the first focusing lens on the first spatial light modulator for spectral encoding, and then focused by the second focusing lens on the second dispersion element for light combination to obtain:

[0019]

[0020] in, is the first spatial light modulator loaded on the The transfer function corresponding to the coded aperture is: The light intensity distribution obtained after passing through the coded aperture; the light beam after spectral coding is focused by the third focusing lens on the second spatial light modulator for spatial stripe coding, and is obtained after being reflected by the object:

[0021] I 1 ( i , k ) ( x , y , l ) = R ( x , y , l ) I 0 ( i ) ( x , y , l ) [ A （ x , y ）+B( x , y )cos( ϕ ( x , y )+ 2 π ( k − 1 ) / 4 ) ]

[0022] in, is the object in position ,wavelength The reflectivity under It is the background component of the fringe code, providing a reference intensity for the fringe light. is the modulation amplitude of the stripe code, which determines the light and dark contrast of the stripes. is the fringe phase, reflecting the depth information of the object. The serial number of the fringe code loaded on the second spatial light modulator, is the phase shift step number of the fringe coding. Each spectrally encoded beam will produce four fringe images with different phase shift steps.

[0023] Furthermore, in step S3, the corner cube prism (15) divides the light beam into four identical beams, which pass through the four-partition polarizer to form four different polarization states: horizontal (H), vertical (V), 45 degrees (45) and right-hand circular polarization (RC). The camera receives a spliced ​​image including the light intensities of the four polarization states, which are respectively:

[0024] I 2 ( i , k ) = [ I H ( i , k ) ( x , y , l ) I V ( i , k ) ( x , y , l ) I 45 ( i , k ) ( x , y , l ) I RC ( i , k ) ( x , y , l ) ]

[0025] in, represents the horizontal polarization intensity of the light beam after the i-th spectral encoding and the k-th spatial encoding. Correspondingly, is the vertical polarization intensity, is the 45 degree polarization intensity, is the right-hand circular polarization intensity. The light intensity of each polarization state can be expressed as:

[0026]

[0027] in, Represents different polarization states, Indicates The modulation function of the polarization state.

[0028] Furthermore, in step S4, the fourth focusing lens (17) focuses the light beam on the imaging detector, and the computer processes the information to obtain the depth, spectrum and polarization information of the target; in order to simplify the complexity of the calculation, a set of the clearest images is selected. To calculate the depth information of the object and apply it globally, the phase of the stripes can be calculated by the following formula:

[0029] After obtaining the phase distribution, the depth information of the object can be obtained through the relationship between the fringe phase and depth:

[0030]

[0031] in, It is the central wavelength within the spectral range; the spectral information is restored through compressed sensing technology, which can effectively process high-dimensional data of spectral and spatial encoding and reduce the number of measurements. Before reconstruction, in order to eliminate the influence of spatial encoding, complete spectral information needs to be obtained:

[0032]

[0033] in I police j ( k ) = [ I police j ( 1 , k ) I police j ( 2 , k ) ... I police j ( N , k ) ] , using this as the input of the reconstruction network, the spectral signals under different polarization states can be reconstructed by solving the following optimization problem:

[0034]

[0035] in I 0 = [ I 0 ( 1 ) I 0 ( 2 ) ... I 0 ( N ) ] = [ F ( 1 ) F ( 2 ) ... F ( N ) ] S , is the regularization parameter, is the regularization term; the polarization information corresponding to the spectrum is solved by the following formula:

[0036] [ r i ϕ ] = [ ( R H − R V ) 2 + ( 2 R 45 − R H − R V ) 2 + ( 2 R RC − R H − R V ) 2 R H + R V 1 2 tan -1 ( 2 R 45 − R H − R V R H − R V ) sin -1 ( 2 R RC − R H − R V ( R H − R V ) 2 + ( 2 R 45 − R H − R V ) 2 + ( 2 R RC − R H − R V ) 2 ) ]

[0037] This enables spectral polarization depth imaging of objects.

[0038] The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift proposed in the present invention has the following characteristics:

[0039] 1. Traditional spectral measurement methods will generate a large amount of redundant data. The module for collecting spectral information in the patent of this invention combines compressed sensing technology, which greatly reduces the amount of data collection.

[0040] 2. The patent of this invention can simultaneously obtain the spectrum, depth and full Stokes polarization information of the target, realize multi-dimensional optical information acquisition and analysis, and help to understand the structure and properties of the sample in multiple dimensions.

[0041] 3. This patented invention combines active spectral imaging, depth imaging, and passive polarization imaging, greatly improving the dynamic range of the imaging system and making it suitable for working under more complex lighting conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 : Schematic diagram of the optical path structure of the patent of the present invention; wherein: 1-information compression module; 2-information compression module; 3-collimating reflector; 4-image acquisition and processing module; 5-light source; 6-collimating lens; 7-broadband filter; 8-first dispersion element; 9-first focusing lens; 10-first spatial light modulator; 11-second focusing lens; 12-second dispersion element; 13-third focusing lens; 14-second spatial light modulator; 15-corner cone prism; 16-four-partition polarizer; 17-fourth focusing lens; 18-imaging detector; 19-computer.

[0043] Figure 2 :Image acquisition flow chart of the patent of this invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the patent of the present invention to clearly and completely describe the technical solutions in the embodiments of the patent of the present invention. Obviously, the described embodiments are only part of the embodiments of the patent of the present invention, not all of them. Based on the embodiments in the patent of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the patent of the present invention.

[0045] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "back", "left", "right", "horizontal", "vertical", "top", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0046] The present invention is further described below in conjunction with the accompanying drawings:

[0047] Figure 1 This is the optical path structure diagram of the patent of the present invention, including a light source module 1, an information compression module 2, a polarization modulation module 3, and an image acquisition and processing module 4.

[0048] Furthermore, the light source module includes a light source 5 , a collimating lens 6 and a broadband filter 7 .

[0049] Furthermore, the information compression module includes a first dispersion element 8, a first focusing lens 9, a first spatial light modulator 10, a second focusing lens 11, a second dispersion element 12, a third focusing lens 13, and a second spatial light modulator 14; the first dispersion element 8 and the second dispersion element 12 have opposite dispersion directions and the same performance.

[0050] Furthermore, the polarization modulation module includes a corner cube prism 15 and a four-partition polarizer 16; the four regions of the four-partition polarizer 16 are a horizontal linear polarizer, a vertical linear polarizer, a 45° linear polarizer, a 1 / 4 wave plate with a horizontal fast axis and a coaxial 45° linear polarizer.

[0051] Furthermore, the image acquisition processing module includes a fourth focusing lens 17 , an imaging detector 18 , and a computer 19 ; the computer 19 is connected to the first spatial light modulator 10 , the second spatial light modulator 14 , and the imaging detector 18 .

[0052] Reference Figure 1 , the imaging method of the present invention is as follows:

[0053] S1, using the light source module 1 to generate a parallel light beam in a specific spectral range.

[0054] S2, using the information compression module 2 to perform spectral encoding and spatial encoding on the parallel light beam in sequence.

[0055] S3, using the polarization modulation module 3 to separate the polarization information of the encoded light beam.

[0056] S4, using the imaging detector 18 in the image acquisition and processing module 4 to collect target information, and the computer 19 to restore the seven-dimensional information of the target.

[0057] Specifically, in the above step S1, the light source generates a light intensity distribution of of light beams.

[0058] Specifically, in the above step S2, after the parallel light beam is dispersed by the first dispersion element 8, it is focused by the first focusing lens 9 on the first spatial light modulator 10 for spectral encoding, and then focused by the second focusing lens 11 to the second dispersion element 12 for light combination to obtain:

[0059]

[0060] in, is the first spatial light modulator 10 loaded with The transfer function corresponding to the coded aperture is: is the light intensity distribution obtained after passing through the coded aperture; the light beam after spectral coding is focused by the third focusing lens 13 on the second spatial light modulator 14 for spatial stripe coding, and is obtained after being reflected by the object:

[0061] I 1 ( i , k ) ( x , y , l ) = R ( x , y , l ) I 0 ( i ) ( x , y , l ) [ A （ x , y ）+B( x , y )cos( ϕ ( x , y )+ 2 π ( k − 1 ) / 4 ) ]

[0062] in, is the object in position ,wavelength The reflectivity under is the background light intensity after fringe coding, indicating the reference light intensity after fringe coding reduction. It is the modulation amplitude of the fringe code, which indicates the amplitude of light intensity variation in the fringe image and determines the light and dark contrast of the fringe. is the fringe phase, reflecting the depth information of the object. The serial number of the stripe code loaded on the second spatial light modulator 14, is the phase shift step number of the fringe coding. Each spectrally encoded beam will produce four fringe images with different phase shift steps.

[0063] Specifically, in the above step S3, the corner cube prism 15 divides the light beam into four identical beams, which pass through the four-partition polarizer 16 to form four different polarization states: horizontal (H), vertical (V), 45 degrees (45) and right-hand circular polarization (RC). The camera receives a spliced ​​image, including the light intensities of these four polarization states, which are:

[0064] I 2 ( i , k ) = [ I H ( i , k ) ( x , y , l ) I V ( i , k ) ( x , y , l ) I 45 ( i , k ) ( x , y , l ) I RC ( i , k ) ( x , y , l ) ]

[0065] The light intensity of each polarization state can be expressed as:

[0066]

[0067] in, Represents different polarization states, Indicates The modulation function of the polarization state.

[0068] Specifically, in the above step S4, the fourth focusing lens (17) focuses the light beam on the imaging detector (18), and the computer 19 processes the information to obtain the depth, spectrum and polarization information of the target; in order to simplify the complexity of the calculation, a set of the clearest images is selected. To calculate the depth information of the object and apply it globally, the phase of the stripes can be calculated by the following formula:

[0069]

[0070] After obtaining the phase distribution, the depth information of the object can be obtained through the relationship between the fringe phase and depth:

[0071]

[0072] in, The central wavelength spectral information within the spectral range is restored through compressed sensing technology. Compressed sensing can effectively process high-dimensional data of spectral and spatial encoding and reduce the number of measurements. Before reconstruction, in order to eliminate the influence of spatial encoding, complete spectral information needs to be obtained:

[0073]

[0074] in I police j ( k ) = [ I police j ( 1 , k ) I police j ( 2 , k ) ... I police j ( N , k ) ] , using this as the input of the reconstruction network, the spectral signals under different polarization states can be reconstructed by solving the following optimization problem:

[0075]

[0076] in I 0 = [ I 0 ( 1 ) I 0 ( 2 ) ... I 0 ( N ) ] = [ F ( 1 ) F ( 2 ) ... F ( N ) ] S , is the regularization parameter, is the regularization term; the polarization information corresponding to the spectrum is solved by the following formula:

[0077] [ r i ϕ ] = [ ( R H − R V ) 2 + ( 2 R 45 − R H − R V ) 2 + ( 2 R RC − R H − R V ) 2 R H + R V 1 2 tan -1 ( 2 R 45 − R H − R V R H − R V ) sin -1 ( 2 R RC − R H − R V ( R H − R V ) 2 + ( 2 R 45 − R H − R V ) 2 + ( 2 R RC − R H − R V ) 2 ) ]

[0078] This enables spectral polarization depth imaging of objects.

[0079] The above content is only for explaining the technical idea of ​​the patent of the present invention, and cannot be used to limit the protection scope of the patent of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the patent of the present invention shall fall within the protection scope of the claims of the patent of the present invention.

Claims

1. Spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift, It is characterized in that include: A light source module (1), an information compression module (2), a polarization modulation module (3), and an image acquisition and processing module (4).

2. The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift according to claim 1, It is characterized in that The light source module (1) comprises a light source (5), a collimating lens (6) and a broadband filter (7).

3. The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift according to claim 1, It is characterized in that The information compression module (2) comprises a first dispersive element (8) (such as a prism, a grating, etc.), a first focusing lens (9), a first spatial light modulator (10), a second focusing lens (11), a second dispersive element (12) (such as a prism, a grating, etc.), a third focusing lens (13), and a second spatial light modulator (14); wherein the first dispersive element (8) and the second dispersive element (12) have the same size, shape, and dispersive performance, and are symmetrically arranged with the first spatial light modulator (10) as the center.

4. The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift according to claim 1, It is characterized in that The polarization modulation module (3) comprises a corner cube prism (15) and a four-zone polarizer (16); the four zones of the four-zone polarizer (16) are respectively a horizontal linear polarizer, a vertical linear polarizer, a 45° linear polarizer, a quarter wave plate with a fast axis along the horizontal direction, and a coaxial 45° linear polarizer.

5. The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift according to claim 1, It is characterized in that The image acquisition processing module (4) comprises a fourth focusing lens (17), an imaging detector (18), and a computer (19); the computer (19) is connected to the first spatial light modulator (10), the second spatial light modulator (14), and the imaging detector (18).

6. The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift according to claim 1, It is characterized in that The following steps are involved: S1, using a light source module (1) to generate a parallel light beam in a specific spectral range; S2, using the information compression module (2) to perform spectral encoding and spatial encoding on the parallel light beam, so as to realize active spectral depth imaging capable of detecting L bands; S3, using the polarization modulation module (3) to separate the polarization information of the encoded light beam to achieve passive polarization imaging; S4, using the image acquisition processing module (4) to collect image information, and using the computer (19) to restore the seven-dimensional information of the object , which includes two-dimensional spatial information , depth information , spectral information , polarization degree , polarization angle and phase difference .

7. The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift according to claim 6, It is characterized in that In step S1, the light source generates a light intensity distribution of of light beams.

8. The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift according to claim 6, It is characterized in that In the step S2, after being dispersed by the first dispersive element (8), the parallel light beam is focused by the first focusing lens (9) on the first spatial light modulator (10) for spectral encoding, and then focused by the second focusing lens (11) on the second dispersive element (12) for light combination to obtain: in, is the first spatial light modulator (10) loaded with The transfer function corresponding to the coded aperture is: is the light intensity distribution obtained after passing through the coded aperture; the light beam after spectral coding is focused by the third focusing lens (13) on the second spatial light modulator (14) for spatial stripe coding, and is obtained after being reflected by the object: in, is the object in position ,wavelength The reflectivity under It is the background component of the fringe code, providing a reference intensity for the fringe light. is the modulation amplitude of the stripe code, which determines the light and dark contrast of the stripes. is the fringe phase, reflecting the depth information of the object. the serial number of the stripe code loaded on the second spatial light modulator (14), is the phase shift step number of the fringe coding. Each spectrally encoded beam will produce four fringe images with different phase shift steps.

9. The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift according to claim 6, It is characterized in that In step S3, the corner cube prism (15) divides the light beam into four identical beams, which pass through the four-partition polarizer (16) to form four different polarization states: horizontal (H), vertical (V), 45 degrees (45) and right-hand circular polarization (RC). The imaging detector (18) receives a spliced ​​image, including the light intensities of the four polarization states, which are respectively: in, represents the horizontal polarization intensity of the light beam after the i-th spectral encoding and the k-th spatial encoding. Correspondingly, is the vertical polarization intensity, is the 45 degree polarization intensity, is the right-hand circular polarization intensity. The light intensity of each polarization state can be expressed as: in, Represents different polarization states, Indicates The modulation function of the polarization state.

10. The spectral polarization depth camera based on dual spatial light modulator coded light source and fringe phase shift according to claim 6, It is characterized in that In step S4, the fourth focusing lens (17) focuses the light beam on the imaging detector (18), and the computer (19) processes the information to obtain the depth, spectrum and polarization information of the target; in order to simplify the complexity of the calculation, a set of the clearest images is selected. To calculate the depth information of the object and apply it globally, the phase of the stripes can be calculated by the following formula: After obtaining the phase distribution, the depth information of the object can be obtained through the relationship between the fringe phase and depth: in, It is the central wavelength within the spectral range; the spectral information is restored through compressed sensing technology, which can effectively process high-dimensional data of spectral and spatial encoding and reduce the number of measurements. Before reconstruction, in order to eliminate the influence of spatial encoding, complete spectral information needs to be obtained: in , using this as the input of the reconstruction network, the spectral signals under different polarization states can be reconstructed by solving the following optimization problem: in , is the regularization parameter, is the regularization term; the polarization information corresponding to the spectrum is solved by the following formula: This enables spectral polarization depth imaging of objects.

Images