An underwater ghost imaging system based on Bessel beam

Abstract

The present invention discloses an underwater ghost imaging system based on Bessel beams, and the underwater ghost imaging system includes an adjustable light source, a collimating optical lens group, an axicon, a first converging lens, a light modulation device, a second converging lens, a light intensity detector, and a computer. The present invention utilizes an axicon to convert an initially incident Gaussian beam into a zero-order Bessel beam with non-diffraction and self-recovery characteristics, which is applied to underwater ghost imaging technology and can reduce the influence of diffraction effects and medium scattering. Compared with the current underwater ghost imaging method using Gaussian beams, the present invention has a simple structure and can be flexibly adjusted. At the same time, it can still be combined with a variety of existing optimization algorithms, which helps to improve the signal-to-noise ratio and clarity of the reconstructed image and achieve high-resolution and long-distance underwater imaging.

Description

Technical Field

[0001] The invention belongs to the technical field of underwater target imaging detection, and relates to an underwater ghost imaging system, and in particular to an underwater ghost imaging system based on a Bessel light beam. Background Art

[0002] Underwater imaging technology is an important technology for underwater detection and is widely used in underwater target identification, tracking and ocean detection. The presence of a large amount of scattering media in the water will cause image blur, and the rapid attenuation of light in the water will cause underexposure of the imaging detector. Increasing the illumination of the light source will enhance the scattering effect, resulting in the inability to take into account both the imaging quality and the imaging distance at the same time. At the same time, the electronic noise caused by sediment particles will also affect the imaging quality. These effects are more obvious in turbid water, making it difficult for traditional optical imaging systems to observe the target.

[0003] Ghost imaging technology uses a bucket detector without spatial resolution to collect light intensity information, and uses the correlation between object morphology and light intensity fluctuations for imaging. It has high noise robustness and can work in low-contrast or even turbid environments that are invisible to traditional optical systems when used for underwater imaging. The current problem with this technology is that when using traditional Gaussian beams for illumination, light waves will experience multiple scattering and attenuation when propagating in water, resulting in poor imaging quality and low resolution. Summary of the invention

[0004] In order to solve the shortcomings of the background technology, the present invention provides an underwater ghost imaging system based on Bessel beams. The system has a compact structure and can be flexibly adjusted. Combined with the non-diffraction and self-recovery properties of Bessel beams, the imaging quality of ghost imaging technology can be improved, and it has strong application potential in the fields of national defense security, underwater resource exploration, scientific research, etc.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] An underwater ghost imaging system based on Bessel beams comprises an adjustable light source, a collimating optical lens group, an axicon, a first converging lens, a light modulation device, a second converging lens, a light intensity detector, and a computer, wherein:

[0007] The adjustable light source is used to emit a Gaussian light beam to the collimating lens group;

[0008] The collimating optical lens assembly is used to collimate and expand the Gaussian light beam output by the adjustable light source to reduce the divergence angle of the light beam;

[0009] The axicon is used to convert the Gaussian beam collimated by the collimating optical lens assembly into a zero-order Bessel beam;

[0010] The first converging lens is used to converge the zero-order Bessel light beam reflected by the target object to the effective modulation area of ​​the light modulation device;

[0011] The light modulation device is used to modulate the zero-order Bessel light beam reflected by the target object through speckle and reflect the modulated light beam;

[0012] The second converging lens is used to converge the light beam modulated by the light modulating device;

[0013] The light intensity detector is used to collect the intensity information of the light beam after being converged by the second converging lens;

[0014] The first end of the computer is connected to the light modulation device for sending speckles to the light modulation device, and the second end of the computer is connected to the light intensity detector for controlling the light intensity detector to collect light intensity information and reconstruct the target object image according to the light intensity information.

[0015] In the present invention, the adjustable light source is provided with a power adjustment module, and the operating wavelength is 532nm.

[0016] In the present invention, the collimating optical lens group expands the light spot output by the adjustable light source into a circular light spot with an adjustable diameter of 10 to 30 mm.

[0017] In the present invention, the light modulation device is a digital micromirror chip DMD, and the projected speckle is an orthogonal Fourier cosine sequence.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The present invention uses an axicon to transform the initially incident Gaussian beam into a zero-order Bessel beam with non-diffraction and self-recovery characteristics, which is applied to underwater ghost imaging technology to reduce the influence of diffraction effect and medium scattering. Compared with the current underwater ghost imaging method using Gaussian beams, the present invention has a simple structure and can be flexibly adjusted, which helps to improve the signal-to-noise ratio and clarity of the reconstructed image and achieve high-resolution and long-distance underwater imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the composition of the underwater ghost imaging system based on Bessel beam;

[0021] Figure 2 This is the energy distribution diagram of the zero-order Bessel beam spot generated by the axicon;

[0022] In the figure, 101 is an adjustable light source, 102 is a collimating optical group, 103 is an axicon, 104 is a first converging lens, 105 is a light modulation device, 106 is a second converging lens, 107 is a light intensity detector, and 108 is a computer. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below in conjunction with the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0024] The present invention provides an underwater ghost imaging system based on Bessel beams, such as Figure 1 As shown, the underwater ghost imaging system includes an adjustable light source 101, a collimating optical lens group 102, an axicon 103, a first converging lens 104, a light modulation device 105, a second converging lens 106, a light intensity detector 107, and a computer 108, wherein:

[0025] The adjustable light source 101 is used to emit a 532nm Gaussian beam with adjustable power to the collimating lens group 102;

[0026] The collimating optical lens group 102 is used to collimate and expand the Gaussian light beam output by the adjustable light source 101, and output a circular light spot with an adjustable diameter of 10 to 30 mm;

[0027] The axicon mirror 103 is used to convert the Gaussian beam after being collimated by the collimating optical lens assembly 102 into a zero-order Bessel beam;

[0028] The first converging lens 104 is used to converge the zero-order Bessel light beam reflected by the target object to the effective modulation area of ​​the light modulation device 105;

[0029] The light modulation device 105 is a digital micromirror chip DMD, which is used to project an orthogonal Fourier cosine speckle sequence to modulate the zero-order Bessel light beam and reflect the modulated light beam;

[0030] The second converging lens 106 is used to converge the light beam modulated by the light modulating device 105;

[0031] The light intensity detector 107 is used to collect the intensity information of the light beam after being converged by the second converging lens 106;

[0032] The first end of the computer 108 is connected to the light modulation device 105 for sending speckles to the light modulation device 105, and the second end of the computer 108 is connected to the light intensity detector 107 for controlling the light intensity detector 107 to collect light intensity information and reconstruct the target image according to the light intensity information.

[0033] In the present invention, the cross-sectional intensity of the zero-order Bessel beam converted by the axicon 103 from the Gaussian beam collimated by the collimating optical lens assembly 102 can be obtained by the following formula. The light intensity simulation result is as follows: Figure 2 shown.

[0034] I(r)=J02 (k(n-1)rγ)

[0035] Where I represents the cross-sectional light intensity, γ represents the bottom angle of the axicon, k represents the wave vector, n represents the refractive index of the axicon, r represents the cross-sectional coordinate, and J0 represents the zero-order Bessel function of the first kind.

[0036] In the present invention, the underwater ghost imaging system is installed in the following manner: first, the adjustable light source 101 is fixed, and the collimating optical lens group 102 and the axis cone mirror 103 are installed in front of the adjustable light source 101 along the light beam propagation direction; then the light modulator 105 is fixed, and the first converging lens is installed between the target and the light modulator 105, so that the light beam reflected by the target is concentrated in the effective modulation area of ​​the light modulator 105 after converging; then the position of the second converging lens 106 and the light intensity detector 107 is adjusted so that the modulated light beam enters the center of the photosensitive area of ​​the light intensity detector 107 after converging.

[0037] The arrangement of the positional relationship of the components in the system of the above installation method is only an example of the present invention, and those skilled in the art may also make adjustments according to actual conditions, which is not limited here.

Claims

1. An underwater ghost imaging system based on Bessel beam, characterized in that The underwater ghost imaging system comprises an adjustable light source, a collimating optical lens group, an axicon, a first converging lens, a light modulation device, a second converging lens, a light intensity detector, and a computer, wherein: The adjustable light source emits a Gaussian beam toward the collimating lens group; The collimating optical lens assembly collimates and expands the Gaussian light beam output by the adjustable light source to reduce the divergence angle of the light beam; The axicon mirror converts the Gaussian beam collimated by the collimating optical lens assembly into a zero-order Bessel beam; The first converging lens converges the zero-order Bessel light beam reflected by the target object to the effective modulation area of ​​the light modulation device; The light modulation device modulates the zero-order Bessel light beam reflected by the target object through speckle and reflects the modulated light beam; The second converging lens converges the light beam modulated by the light modulating device; The light intensity detector collects the intensity information of the light beam after being converged by the second converging lens; The first end of the computer is connected to the light modulation device to send speckle to the light modulation device, and the second end of the computer is connected to the light intensity detector to control the light intensity detector to collect light intensity information and reconstruct the target object image according to the light intensity information; The light modulation device is a digital micromirror chip DMD, and the projected speckle is an orthogonal Fourier cosine sequence.

2. The underwater ghost imaging system based on Bessel beam according to claim 1, characterized in that The adjustable light source is provided with a power adjustment module, and the operating wavelength is 532nm.

3. The underwater ghost imaging system based on Bessel beam according to claim 1, characterized in that The collimating optical lens group expands the light spot output by the adjustable light source into a circular light spot with an adjustable diameter of 10~30mm.

4. The underwater ghost imaging system based on Bessel beam according to claim 1, characterized in that The axicon lens converts the Gaussian beam collimated by the collimating optical lens assembly into a zero-order Bessel beam. The cross-sectional intensity is obtained by the following formula: in, Represents the cross-sectional light intensity represents the base angle of the axicon, represents the wave vector, represents the refractive index of the axicon, are cross-sectional coordinates, is the zero-order Bessel function of the first kind.

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