A type of atomic terahertz holographic imaging device

Abstract

This invention relates to the field of terahertz imaging technology, specifically disclosing an atomic terahertz holographic imaging device, comprising a terahertz source, a terahertz phase modulation module, an atomic fluorescence imaging module, and an image acquisition and processing module. The terahertz phase modulation module is used to modulate the terahertz signal after irradiating a sample object. The atomic fluorescence imaging module is used to receive the processed sample terahertz signal and generate a visible light image. The image acquisition and processing module is used to acquire the visible light image and use an algorithm to reconstruct and obtain a terahertz holographic image with the original phase information. The terahertz phase modulation module includes a sample holder, a terahertz mirror, a pupil, a first terahertz lens, and a second terahertz lens. This atomic terahertz holographic imaging device can be applied in practice, achieving high-resolution imaging, acquiring phase information to achieve holographic imaging, and also enabling rapid imaging to realize terahertz holographic imaging.

Description

Technical Field

[0001] This invention relates to the field of terahertz imaging technology, and more specifically to an atomic terahertz holographic imaging device. Background Technology

[0002] Terahertz imaging, as one of the key technologies of terahertz, allows terahertz waves to penetrate materials such as ceramics, fat, fabric, and plastics, but not easily penetrate metals. Moreover, it is harmless to the human body. Due to these excellent properties of terahertz, it has a wide range of applications in security inspection, non-destructive testing, and other fields.

[0003] Traditional terahertz imaging devices are mostly based on electronic detectors. When performing high-resolution imaging, they require complex cooling equipment. When performing phase imaging, they need to scan and calculate multiple times, making it impossible to present images quickly and conveniently. Moreover, currently, terahertz imaging devices do not have the functions of high resolution, high-speed imaging, and real-time phase imaging at the same time. Summary of the Invention

[0004] In view of the above problems, the present invention aims to provide an atomic terahertz holographic imaging device that can be applied in practice. On the one hand, it can achieve high-resolution imaging, and on the other hand, it can acquire phase information to achieve holographic imaging. At the same time, it can also achieve rapid imaging to realize terahertz holographic imaging.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] An atomic terahertz holographic imaging device includes: a terahertz source, a terahertz phase modulation module, an atomic fluorescence imaging module, and an image acquisition and processing module.

[0007] The terahertz phase modulation module is used to modulate the terahertz signal after irradiating the sample object.

[0008] The atomic fluorescence imaging module is used to receive the processed terahertz signal of the sample and generate a visible light image.

[0009] The image acquisition and processing module is used to acquire visible light images and use algorithms to reconstruct terahertz holographic images with original phase information.

[0010] The terahertz phase modulation module includes: a sample holder, a terahertz mirror, a pupil, a first terahertz lens, and a second terahertz lens.

[0011] The sample holder, the first terahertz lens, the pupil, and the second terahertz lens are arranged sequentially along the optical path.

[0012] The terahertz reflector is used to deliver terahertz waves to the sample holder in an oblique irradiation manner.

[0013] The first terahertz lens and the second terahertz lens are configured to form a 4F imaging system, and the pupil is positioned in the Fourier plane.

[0014] The first terahertz lens is used to focus the terahertz wave at the edge of the pupil, and the pupil filters out stray light other than the cutoff frequency.

[0015] The second terahertz lens is used to focus the terahertz waves passing through the edge of the pupil together with the terahertz waves passing through the object in the atomic fluorescence imaging module.

[0016] In at least one embodiment of the atomic terahertz holographic imaging device provided in this disclosure, the atomic fluorescence imaging module includes: a probe laser, a coupling laser, a Rydberg laser, a coupling mirror, a dichroic mirror, and an atomic gas cell.

[0017] The probe laser is used to generate probe light.

[0018] The coupled laser is used to generate coupled light.

[0019] The Rydberg laser is used to provide Rydberg light to the atomic gas chamber.

[0020] The coupled light reflector is used to deliver coupled light to the dichroic mirror.

[0021] The dichroic mirror is used to transmit the probe light and coupling light to the atomic gas cell.

[0022] In at least one embodiment of the atomic terahertz holographic imaging apparatus provided in this disclosure, the sample holder is a rotatable sample holder.

[0023] In at least one embodiment of the atomic terahertz holographic imaging device provided in this disclosure, the wavelength of the probe light is 852 nm.

[0024] The wavelength of the coupled light is 1470 nm.

[0025] The wavelength of the Rydberg light is 822 nm.

[0026] In at least one embodiment of the atomic terahertz holographic imaging device provided in this disclosure, the pupil is a metal pupil.

[0027] In at least one embodiment of the atomic terahertz holographic imaging device provided in this disclosure, the atomic fluorescence imaging module and the image acquisition and processing module are configured to be connected via fiber optic cones.

[0028] In at least one embodiment of the atomic terahertz holographic imaging device provided in this disclosure, the image acquisition and processing module includes a computer and a CCD camera.

[0029] The CCD camera is configured to be electrically connected to the computer and is used to acquire fluorescence images.

[0030] In at least one embodiment of the atomic terahertz holographic imaging device provided in this disclosure, a relay lens is also provided, which is located between the CCD camera and the atomic gas cell, and the relay lens is used to adjust the imaging effect.

[0031] In at least one embodiment of the atomic terahertz holographic imaging device provided in this disclosure, the atomic gas chamber is a cesium atomic gas chamber.

[0032] The beneficial effects of this invention are as follows:

[0033] 1. The terahertz waves in this invention have good penetrability, and can penetrate most dielectric materials and non-polar liquids, enabling non-destructive testing of their internal structures.

[0034] 2. Compared with existing terahertz holographic imaging devices, the present invention has a simpler structure, lower cost, and is easier to operate.

[0035] 3. The terahertz phase modulation module in this invention has a simple and reliable structure, is easy to adjust, and has a higher spatial bandwidth product compared with traditional off-axis holographic imaging, enabling detection in the terahertz band.

[0036] 4. The image processed by the image acquisition and processing module in this invention has the characteristics of high resolution, high spatial bandwidth product and contains original phase information. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0038] Figure 1 This is a schematic diagram of the atomic terahertz holographic imaging device in Example 1.

[0039] Figure 2 This is a schematic diagram of the atomic terahertz holographic imaging device in Example 2.

[0040] In the picture:

[0041] 10. Terahertz sources;

[0042] 20. Terahertz phase modulation module; 21. Sample holder; 22. Terahertz mirror; 23. Pupil; 24. First terahertz lens; 25. Second terahertz lens;

[0043] 30. Atomic fluorescence imaging module; 31. Probe laser; 32. Coupler laser; 33. Rydberg laser; 34. Coupler mirror; 35. Dichroic mirror; 36. Atomic gas cell;

[0044] 40. Image acquisition and processing module; 41. Computer; 42. CCD camera;

[0045] 50. Fiber optic cone;

[0046] 60. Relay lens. Detailed Implementation

[0047] The technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments, not all embodiments.

[0048] This invention proposes an atomic terahertz holographic imaging method and apparatus, comprising the following:

[0049] After the terahertz source emits terahertz waves, they pass through the sample holder in the terahertz phase modulation module and illuminate the first terahertz lens. The incident angle of the illumination light is controlled to obliquely illuminate the sample to meet the cutoff frequency condition. Simultaneously, the sample is rotated so that the terahertz wave scans to capture complete sample information. The terahertz illumination light passing through the object becomes scattered light, and after passing through the metal pupil, it interferes with the sample light after passing through the second terahertz lens and enters the atomic fluorescence imaging module.

[0050] The laser using the three wavelengths described above employs a three-step excitation method to coherently excite atoms from the ground state to the initial Rydberg state. When the terahertz wave after interference interacts with the atoms, it incoherently transfers the atoms from the initial Rydberg state to a specific Rydberg state. When the atoms de-excite from this specific Rydberg state, the spontaneously generated fluorescence is in the visible light band. The resulting fluorescence image contains the intensity and phase information of the terahertz waves. Finally, an optical CCD camera is used to receive the image and save it in TIF format.

[0051] The terahertz off-axis interferogram received by the CCD camera entering the atomic gas cell contains the real part of a complex analytic function. The complex analytic function is recovered using a MATLAB algorithm, from which the complex amplitude image is extracted. This method possesses the analyticity of complex functions and imposes no constraints on the samples. Even when the autocorrelation in the frequency space of the complex amplitude image and the interferogram completely overlaps, the analyticity remains unchanged, achieving a higher spatial bandwidth product than traditional off-axis holographic imaging.

[0052] Example 1

[0053] like Figure 1As shown, an atomic terahertz holographic imaging device includes a terahertz source 10, a terahertz phase modulation module 20, an atomic fluorescence imaging module 30, and an image acquisition and processing module 40.

[0054] Specifically, the terahertz phase modulation module 20 is used to modulate the terahertz signal after irradiating the sample object.

[0055] Specifically, the atomic fluorescence imaging module 30 is used to receive the processed sample terahertz signal and generate a visible light image.

[0056] Specifically, the image acquisition and processing module 40 is used to acquire visible light images and use algorithms to reconstruct and obtain terahertz holographic images with original phase information.

[0057] In this embodiment, the terahertz phase modulation module 20 includes a sample holder 21, a terahertz reflector 22, a pupil 23, a first terahertz lens 24, and a second terahertz lens 25.

[0058] Specifically, the sample holder 21, the first terahertz lens 24, the pupil 23, and the second terahertz lens 25 are arranged sequentially along the optical path.

[0059] Specifically, the terahertz mirror 22 is used to deliver terahertz waves to the sample holder 21 in an oblique illumination manner. The first terahertz lens 24 and the second terahertz lens 25 are configured to form a 4F imaging system, and the pupil 23 is positioned at the Fourier plane.

[0060] Specifically, the first terahertz lens 24 is used to focus a portion of the terahertz wave at the edge of the pupil 23, and the pupil 23 filters out stray light other than the cutoff frequency.

[0061] Specifically, the second terahertz lens 25 is used to focus the terahertz waves passing through the edge of the pupil 23 together with the terahertz waves passing through the object into the atomic fluorescence imaging module 30.

[0062] In this embodiment, the atomic fluorescence imaging module 30 includes a probe laser 31, a coupling laser 32, a Rydberg laser 33, a coupling mirror 34, a dichroic mirror 35, and an atomic gas cell 36.

[0063] Specifically, probe laser 31 is used to generate probe light. Coupler laser 32 is used to generate coupler light. Rydberg laser 33 is used to provide Rydberg light to atomic gas chamber 36.

[0064] Specifically, the coupling light reflector 34 is used to deliver the coupling light to the dichroic mirror 35. The dichroic mirror 35 is used to deliver the probe light and the coupling light to the atomic gas cell 36.

[0065] In this embodiment, the sample holder 21 is a rotatable sample holder 21.

[0066] In this embodiment, the wavelength of the probe light is 852 nm. The wavelength of the coupling light is 1470 nm. The wavelength of the Rydberg light is 822 nm.

[0067] In this embodiment, the pupil 23 is a metallic pupil 23.

[0068] In this embodiment, the atomic fluorescence imaging module 30 and the image acquisition and processing module 40 are configured to be connected via an optical fiber taper 50.

[0069] In this embodiment, the image acquisition and processing module 40 includes a computer 41 and a CCD camera 42. The CCD camera 42 is configured to be electrically connected to the computer 41 and is used to acquire fluorescence images.

[0070] In this embodiment, the atomic gas chamber 36 is a cesium atomic gas chamber.

[0071] Example 2

[0072] like Figure 2 As shown, this embodiment discloses an atomic terahertz holographic imaging device, which differs from Embodiment 1 in that it also has a relay lens 60, which is located between the CCD camera 42 and the atomic gas chamber 36. The relay lens 60 is used to adjust the imaging effect.

[0073] The working method of the atomic terahertz holographic imaging device in Embodiment 1 will be disclosed below to further illustrate its working principle.

[0074] The operation of an atomic terahertz holographic imaging device includes the following steps:

[0075] 1. Place the object to be imaged on the sample holder and turn on the terahertz source.

[0076] 2. Turn on the probe laser, coupling laser, and Rydberg laser to deliver 852nm probe light, 1470nm coupling light, and 822nm Rydberg light into the atomic gas chamber. Use a three-step excitation method to coherently excite the atom from the ground state to the initial Rydberg state. When the terahertz wave interacts with the atom, it incoherently transfers the atom from the initial Rydberg state to a specific Rydberg state.

[0077] 3. When an atom de-excites from this specific Rydberg state, the spontaneously emitted fluorescence is in the visible light band and is received by an optical CCD camera.

[0078] 4. Adjust the terahertz mirror to obliquely incident the terahertz wave and rotate the sample stage. The terahertz wave incident directly onto the object is the illumination light, while the obliquely incident terahertz wave is the reference light. The pupil in the Fourier plane filters out light that does not meet the cutoff frequency condition, and the oblique illumination avoids twin images appearing on the same optical axis. The two beams of light penetrate the sample and form an off-axis interference image in the atomic gas cell. Rotate the sample stage to obtain complete image information of the object.

[0079] 5. The fluorescence intensity distribution is consistent with the terahertz intensity distribution. Fluorescence images are obtained through a CCD camera and sent to a computer. The image is processed using an algorithm, and a terahertz holographic image with phase information is reconstructed based on the intensity-phase relationship.

[0080] Although embodiments of this application have been shown and described above, the scope of protection of this invention is not limited thereto. Any variations or substitutions that can be conceived without inventive effort should be covered within the scope of protection of this invention. Unless expressly stated otherwise, no element, action or instruction used herein should be construed as critical or necessary.

Claims

1. An atomic terahertz holographic imaging device, characterized by, It comprises a terahertz source, a terahertz phase modulation module, an atomic fluorescence imaging module and an image acquisition and processing module. The terahertz phase modulation module is used for modulating the terahertz signal after irradiating the sample object. The atomic fluorescence imaging module is used for receiving the processed sample terahertz signal and generating a visible light image. The image acquisition and processing module is used for acquiring the visible light image and using an algorithm to restore a terahertz holographic image with original phase information. The terahertz phase modulation module comprises a sample holder, a terahertz mirror, a pupil, a first terahertz lens and a second terahertz lens. The sample holder, the first terahertz lens, the pupil and the second terahertz lens are arranged in sequence along the optical path. The terahertz mirror is used to transport the terahertz wave to the sample holder in an oblique irradiation manner. The first terahertz lens and the second terahertz lens are configured to constitute a 4F imaging system, and the pupil is configured at the Fourier plane. The first terahertz lens is used to converge the terahertz wave on the pupil, and the stray light other than the cutoff frequency is filtered out by the pupil. The second terahertz lens is used to converge the terahertz wave passing through the edge of the pupil together with the terahertz wave passing through the object in the atomic fluorescence imaging module.

2. The atomic terahertz holographic imaging device according to claim 1, wherein, The atomic fluorescence imaging module comprises a probe light laser, a coupling light laser, a Rydberg laser, a coupling light mirror, a dichroic mirror and an atomic cell. The probe light laser is used to generate probe light. The coupling light laser is used to generate coupling light. The Rydberg laser is used to provide Rydberg light for the atomic cell. The coupling light mirror is used to transport the coupling light to the dichroic mirror. The dichroic mirror is used to transport the probe light and the coupling light to the atomic cell.

3. The atomic terahertz holographic imaging device of claim 1, wherein, The sample holder is a rotatable sample holder.

4. The atomic terahertz holographic imaging device of claim 2, wherein, The wavelength of the probe light is 852nm. The wavelength of the coupling light is 1470nm. The wavelength of the Rydberg light is 822nm.

5. The atomic terahertz holographic imaging device of claim 1, wherein, The pupil is a metal pupil.

6. The atomic terahertz holographic imaging device of claim 1, wherein, The atomic fluorescence imaging module and the image acquisition and processing module are configured to be connected through a fiber optic taper.

7. The atomic terahertz holographic imaging device according to claim 6, wherein, The image acquisition and processing module comprises a computer and a CCD camera. The CCD camera is configured to be electrically connected with the computer, and the CCD camera is used to acquire a fluorescence image.

8. The atomic terahertz holographic imaging device according to claim 7, wherein, There is also a relay lens between the CCD camera and the atomic cell, which is used to adjust the imaging effect.

9. The atomic terahertz holographic imaging device of claim 2, wherein, The atomic cell is a cesium atomic cell.

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