A variable resolution computational ghost imaging method for axially moving targets

Abstract

This invention relates to a variable-resolution ghost imaging method for axially moving targets, comprising: determining the axial speed and distance of the moving target, as well as the size of the moving target and the distance from the moving target to the optical projection system; setting speckle parameters; generating a human-eye-like non-uniform variable-resolution speckle pattern with high resolution at the fovea, low resolution around the periphery, and a uniformly varying radius of the fovea region based on the speckle parameters, the moving target's motion parameters, and scene information; projecting the human-eye-like non-uniform variable-resolution speckle onto the axially moving target for sampling and measuring the reflected light intensity; and performing a second-order correlation operation between the reflected light intensity and the projected speckle information to obtain the final reconstructed image. This invention utilizes a human-eye-like non-uniform speckle pattern with a varying fovea radius to reconstruct axially moving targets, maintaining a constant proportion of the fovea region occupied by the target during movement, thereby improving the imaging quality of axially moving targets.

Description

Technical Field

[0001] This invention relates to the field of photoelectric imaging technology, and in particular to a variable resolution computational ghost imaging method for axially moving targets. Background Technology

[0002] Ghost imaging is a novel imaging technique based on the quantum or classical correlation properties of light field fluctuations. It acquires target image information by measuring the intensity correlation function between a reference light field and a target detection light field. It can correlate the two-dimensional light field intensity distribution of the light source with the total light intensity of the echo light field carrying target modulation information, thereby obtaining target feature parameters. Compared with traditional optical imaging methods, ghost imaging technology has advantages such as low noise, low cost, and small size, thus showing great application prospects and significant potential value in fields such as target tracking, medical imaging, microscopic imaging, optical encrypted transmission, and scattering imaging.

[0003] Traditional ghost imaging methods involve two optical paths: a signal path containing the target object, where the signal light illuminates the object, and the reflected or transmitted light is received by a single-pixel detector lacking spatial resolution. The other beam propagates freely without any processing and is called the reference beam; its intensity distribution is detected by a detector with spatial resolution. The light source is a pseudo-thermal source, generated by a laser illuminating a rotating frosted glass plate or phase plate. Furthermore, if a spatial light modulator or digital micromirror device replaces the rotating frosted glass or phase plate to generate the pseudo-thermal light field, the reference path in the two-arm system can be omitted, and its random light field can be replaced by a pre-coded speckle field. This method is also known as single-arm computational ghost imaging, which greatly simplifies the configuration of the ghost imaging system.

[0004] The illumination projection pattern required for target modulation in computational ghost imaging is generated by computer encoding. The non-uniform variable-resolution speckle pattern generated using a mimicking human retinal structure corresponds to higher resolution in the fovea, which can optimize the imaging quality of the central region of interest to some extent. For computational ghost imaging of moving targets, image degradation due to motion is a significant problem compared to static targets. For axial motion, variable-resolution computational ghost imaging can effectively control the target within a fixed speckle light field. However, there is still room for improvement in further enhancing the imaging quality and suppressing motion-induced image degradation. Summary of the Invention

[0005] The purpose of this invention is to provide a variable resolution computational ghost imaging method for axially moving targets, thereby improving the imaging capability of existing variable resolution computational ghost imaging methods for axially moving objects.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A variable-resolution computational ghost imaging method for axially moving targets includes:

[0008] The axial velocity and distance of the moving target, as well as the size of the moving target and the distance of the moving target from the optical projection system, are determined to obtain the motion parameters and scene information of the moving target;

[0009] Set speckle parameters, and generate human-eye non-uniform variable resolution speckle with high central fovea resolution, low surrounding resolution, and uniformly varying central fovea radius based on the speckle parameters, motion parameters of the moving target, and scene information.

[0010] The human-eye-like non-uniform variable resolution speckle pattern is projected onto an axially moving target for sampling, and the reflected light intensity is measured.

[0011] The reflected light intensity value and the projected speckle information are subjected to a second-order correlation operation to obtain the final reconstructed image.

[0012] Preferably, the human-eye non-uniform variable resolution speckle is projected onto the axially moving target surface through a spatial light modulator and an optical lens, and the detection value corresponding to the human-eye non-uniform variable resolution speckle is measured.

[0013] Preferably, the speckle parameters include: speckle resolution, radius of the central concave region, maximum discrete angle, and maximum discrete ring number.

[0014] Preferably, based on the speckle parameters, a human-eye-like non-uniform variable resolution speckle pattern with a uniformly varying radius of the central fovea region is generated according to the sampling number, and the generation formula is as follows: (1)

[0015] r0(i)=r0(1)+v*t(i)*(a / L) (1)

[0016] Where r0(i) is the radius of the central concave region of the i-th speckle pattern, v is the axial velocity of the target object, t(i) is the motion time corresponding to the i-th speckle pattern, a represents the spatial size of the target object, and L is the distance between the target object and the projection system.

[0017] Preferably, the human-eye-like non-uniform variable resolution speckle projection is applied to the axially moving target object for sampling, ensuring that the target motion time and projection time are the same, and that the start and end times are the same.

[0018] Preferably, after sampling, the reflected light intensity value S is measured using a single-pixel detector. n (x,y):

[0019]

[0020] Among them, P n (x,y) represents the projected speckle information, and I(x,y) represents the target object information.

[0021] Preferably, the light intensity value S n (x,y) and the projected speckle information P n Perform a second-order correlation operation on (x,y) and obtain the final reconstructed image I(x,y) through the host computer:

[0022]

[0023] Where N is the total number of projected speckle patterns. This represents the average value of the light intensity detected. This represents the average value of the speckle information.

[0024] The beneficial effects of this invention are as follows:

[0025] Compared with the traditional variable resolution ghost imaging method with a fixed central fovea radius, the present invention utilizes a human-eye-like non-uniform speckle pattern that continuously adjusts the size of the region of interest in the central fovea during the movement of the target object. This maintains the proportion of the speckle central fovea region occupied by the target during the movement. Compared with the human-eye-like non-uniform speckle pattern with a fixed central fovea radius, it can better maintain the stability in the speckle light field, reduce image degradation caused by motion, and improve the imaging quality of axially moving target objects. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the variable resolution ghost imaging method for axially moving targets according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the optical projection system according to an embodiment of the present invention;

[0029] Figure 3 This is a comparison of the reconstruction results of the traditional fixed central concave radius calculation ghost imaging method and the variable resolution calculation ghost imaging method for axially moving targets, according to an embodiment of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] This embodiment discloses a variable resolution ghost imaging method for axially moving targets, the flowchart of which is shown below. Figure 1 As shown, the applied system architecture is as follows: Figure 2 As shown, the specific implementation steps are as follows:

[0033] Step 1: Predetermine the target's axial velocity v and distance (represented as v*t), as well as the target's size a and the target's distance L from the optical projection system.

[0034] In this implementation example, the movement speed v is set to 2 mm / s, the movement time is 2.5 s, and the movement distance is 5 mm. The ratio a / L between the target size and the distance L from the target to the optical projection system is 0.0625.

[0035] Step 2: Set the illumination speckle parameters to be projected, including speckle resolution m*m, concave region radius r0, maximum discrete angle P, and maximum discrete ring number Q. Generate a human-eye-like non-uniform variable resolution speckle pattern with high resolution in the concave region and low resolution around the periphery. Based on the parameters from Step 1, generate a human-eye-like non-uniform variable resolution speckle pattern with a uniformly varying concave region radius according to the sampling quantity. The generation formula is as follows:

[0036] r0(i)=r0(1)+v*t(i)*(a / L) (1)

[0037] Where r0(i) is the radius of the central concave region of the i-th speckle pattern, v is the axial velocity of the target object, t(i) is the motion time corresponding to the i-th speckle pattern, a represents the spatial size of the target object, and L is the distance between the target object and the projection system.

[0038] In this implementation example, the speckle resolution used is 64*64, and the corresponding resolution of the reconstructed image of the axially moving target is also 64*64. The minimum value of r0 is 21, and the maximum value is 23. Four different sampling numbers were set: 1024, 1229, 1434, and 1638. The corresponding number of non-uniform speckle patterns with varying concave radii are 1024, 1229, 1434, and 1638, respectively.

[0039] according to Figure 2 The system principle structure is as follows: LED light source 1 emits an illumination beam that shines on spatial light modulator 2 and is projected onto the surface of target object 4 moving axially through optical lens 3.

[0040] Step 3: Project the above-mentioned human-eye-like non-uniform speckle onto the target object moving axially and sample it, ensuring that the target movement time and projection time are the same and the start and end times are the same, and use a single-pixel detector to measure the reflected light intensity value.

[0041]

[0042] Among them, the speckle information is P n (x,y), the light intensity value collected by the single-pixel detector is denoted as S. n The reflectivity information of the target is I(x,y).

[0043] according to Figure 2 The system's principle and structure are as follows: a spatial light modulator 2 and a lens 3 project a computer-generated, human-eye-inspired, non-uniform speckle illumination pattern onto the surface of an axially moving target 4. The reflected light intensity is received by a single-pixel detector 5, which measures the detection value corresponding to each speckle illumination pattern. The light intensity detection value is acquired by a data acquisition card 6.

[0044] Step 4: Convert the light intensity value S obtained in Step 3 into a value that represents the light intensity value S. n (x,y) and the projected speckle information P n A second-order correlation operation is performed on (x,y) to obtain the final reconstructed image I(x,y) on the host computer 9.

[0045]

[0046] Depend on Figure 3 The reconstruction experiments were compared between the traditional fixed concave radius computational ghost imaging method and the variable resolution computational ghost imaging method for axially moving targets. The results show that, under specific sampling numbers or sampling rates, for axially moving targets, the proposed variable concave radius human-eye-inspired non-uniform speckle pattern can further improve the reconstruction effect of axially moving targets under the same motion mode and parameters, enhance imaging quality, and reduce the adverse effects of motion-induced image degradation on the reconstruction results.

[0047] This invention discloses a variable-resolution ghost imaging method for axially moving targets. After presetting motion parameters, target size, and distance from the projection system, a human-eye-like non-uniform variable-resolution speckle pattern with a high-resolution central fovea and low-resolution surrounding area is generated via computer encoding. Furthermore, a human-eye-like non-uniform variable-resolution speckle pattern with a uniformly varying radius of the central fovea region is generated based on the motion parameters and the aforementioned scene information. This variable-radius non-uniform speckle pattern is projected onto the target moving along the optical axis. Reconstruction calculations are performed using light intensity values ​​measured by a single-pixel detector and speckle information to obtain a reconstructed image of the axially moving target. This invention utilizes human-eye-like non-uniform speckle with a varying central fovea radius to reconstruct axially moving targets, maintaining a constant proportion of the central fovea region occupied by the target during movement. Compared to human-eye-like non-uniform speckle with a fixed central fovea radius, this method improves the imaging quality of axially moving targets and mitigates image degradation caused by motion.

[0048] The beneficial effects of this invention are as follows:

[0049] Compared with the traditional variable resolution ghost imaging method with a fixed central fovea radius, the present invention utilizes a human-eye-like non-uniform speckle pattern that continuously adjusts the size of the region of interest in the central fovea during the movement of the target object. This maintains the proportion of the speckle central fovea region occupied by the target during the movement. Compared with the human-eye-like non-uniform speckle pattern with a fixed central fovea radius, it can better maintain the stability in the speckle light field, reduce image degradation caused by motion, and improve the imaging quality of axially moving target objects.

[0050] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A variable-resolution ghost imaging method for axially moving targets, characterized in that, include: The axial velocity and distance of the moving target, as well as the size of the moving target and the distance of the moving target from the optical projection system, are determined to obtain the motion parameters and scene information of the moving target; Set speckle parameters, and generate human-eye non-uniform variable resolution speckle with high central fovea resolution, low surrounding resolution, and uniformly varying central fovea radius based on the speckle parameters, motion parameters of the moving target, and scene information. Among them, based on the speckle parameters, a human-eye-like non-uniform variable resolution speckle pattern with a uniformly varying radius of the central concave region is generated according to the sampling number, and the generation formula is as follows (1): r0(i)=r0(1)+v*t(i)*(a / L)(1) Where r0(i) is the radius of the central concave region of the i-th speckle pattern, v is the axial velocity of the target object, t(i) is the motion time corresponding to the i-th speckle pattern, a represents the spatial size of the target object, and L is the distance between the target object and the projection system. The human-eye-like non-uniform variable resolution speckle pattern is projected onto an axially moving target for sampling, and the reflected light intensity is measured. The reflected light intensity value and the projected speckle information are subjected to a second-order correlation operation to obtain the final reconstructed image.

2. The variable resolution ghost imaging method for axially moving targets according to claim 1, characterized in that, The non-uniform variable resolution speckle pattern of the human eye is projected onto the axially moving target surface using a spatial light modulator and an optical lens, and the detection value corresponding to the non-uniform variable resolution speckle pattern of the human eye is measured.

3. The variable resolution ghost imaging method for axially moving targets according to claim 1, characterized in that, The speckle parameters include: speckle resolution, radius of the central concave region, maximum discrete angle, and maximum discrete ring number.

4. The variable resolution ghost imaging method for axially moving targets according to claim 1, characterized in that, The human-eye-like non-uniform variable resolution speckle projection is applied to the axially moving target object for sampling. During sampling, the target motion time and projection time are kept the same, and the start and end times are also the same.

5. The variable resolution ghost imaging method for axially moving targets according to claim 4, characterized in that, After sampling, the intensity value S of the reflected light is measured using a single-pixel detector. n (x,y): Among them, P n (x,y) represents the projected speckle information, and I(x,y) represents the target object information.

6. The variable resolution ghost imaging method for axially moving targets according to claim 5, characterized in that, The light intensity value S n (x,y) and the projected speckle information P n Perform a second-order correlation operation on (x,y) and obtain the final reconstructed image I(x,y) through the host computer: Where N is the total number of projected speckle patterns. This represents the average value of the light intensity detected. This represents the average value of the speckle information.

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