阅读说明：本技术 一种新型三维中空形光场生成方法与装置 (Novel three-dimensional hollow light field generation method and device ) 是由 朱大钊 丁晨良 匡翠方 徐良 李海峰 刘旭 于 2021-08-03 设计创作，主要内容包括：本发明公开了一种新型三维中空形光场调控方法和装置,属于光学工程领域。该方法使用两种旋向相反的0-2π涡旋相位板对偏振光的两个分量分别调至,在转化成圆偏光,两个分量的光干涉形成一种复杂的柱状矢量偏振光,聚焦形成新型三维中空光场。该装置,包括起偏器、半波片、滤波透镜、滤波小孔、准直透镜、第一锥透镜、第二锥透镜、DMD、SLM,第一1/4波片、反射镜和第二1/4波片。相对于传统的方法产生更高质量的3D HLF,并且利用SLM的偏振选择特性,可以采用单路光形成3D HLF且不产生相干缺陷。本发明采用SLM调控光束可以同时实现像差优化,采用环形光束可以挡掉中心低频部分进一步提高光束质量。(The invention discloses a novel three-dimensional hollow light field regulation and control method and device, and belongs to the field of optical engineering. The method uses two 0-2 pi vortex phase plates with opposite rotation directions to adjust two components of polarized light respectively, and after the two components are converted into circular polarized light, the light of the two components interferes to form a complex columnar vector polarized light, and a novel three-dimensional hollow light field is formed by focusing. The device comprises a polarizer, a half-wave plate, a filter lens, a filter pore, a collimating lens, a first cone lens, a second cone lens, a DMD (digital micromirror device), an SLM (Selective laser modulation), a first 1/4 wave plate, a reflecting mirror and a second 1/4 wave plate. Compared with the traditional method, the method can generate the 3D HLF with higher quality, and the single-path light can be adopted to form the 3D HLF without generating coherent defects by utilizing the polarization selection characteristic of the SLM. The invention adopts the SLM to regulate and control the light beam to simultaneously realize aberration optimization, and adopts the annular light beam to block the central low-frequency part so as to further improve the light beam quality.)

1. The utility model provides a novel three-dimensional hollow light field generates device includes in proper order along the light path: polarizer (1), 1/2 half-wave plate (2), filter lens (3), filtering aperture (4), collimating lens (5), first cone lens (6), second cone lens (7), DMD (8), SLM (9), first 1/4 wave plate (10), speculum (11) and second 1/4 wave plate (12), its characterized in that: after entering the device, light beams are converted into linearly polarized light through a polarizer (1), the linearly polarized light is converged by a filter lens (3) after passing through an 1/2 wave plate (2), a filter small hole (4) is formed in the focal plane of the filter lens (3), and the light beams passing through the filter small hole (4) are collimated into parallel light again through a collimating lens (5);

the collimated parallel light sequentially passes through the first cone lens (6) and the second cone lens (7) and enters the DMD (8), the light beam is reflected to the left half screen of the SLM (9) by the DMD (8), then is reflected to the reflecting mirror (11), is reflected by the reflecting mirror (11) and then enters the right half screen of the SLM (9), the light beam passes through the first 1/4 wave plate (10) twice between the SLM (9) and the reflecting mirror (11), and the light beam is emitted from the right half screen of the SLM (9) and passes through the second 1/4 wave plate (12).

2. The novel three-dimensional hollow-shaped light field generating device according to claim 1, wherein: the s-component and p-component energies are made the same by rotating 1/2 wave plate (2).

3. The novel three-dimensional hollow-shaped light field generating device according to claim 1, wherein: the filtering small hole (4) is used for filtering stray light at the edge and improving the number of light beams.

4. The novel three-dimensional hollow-shaped light field generating device according to claim 1, wherein: the first cone lens (6) and the second cone lens (7) form a lens group for modulating the energy distribution of the light beam to enable the energy distribution of the cross section of the light beam to be annular.

5. The novel three-dimensional hollow-shaped light field generating device according to claim 1, wherein: different phase diagrams are loaded on the left half screen and the right half screen of the SLM (9), vortex phases are loaded on the left side, and vortex phases with starting points changing along with the radius and opposite in rotation direction are loaded on the right side.

6. The novel three-dimensional hollow-shaped light field generating device according to claim 1, wherein: the s-light and the p-light are converted into circularly polarized light with opposite handedness by the second 1/4 wave plate 12, and are coherently superposed to form a light beam with a complex polarization state distribution, and the light beam is focused to form the 3D HLF.

7. A novel three-dimensional hollow light field generation method comprises the following steps:

firstly, laser emitted by a laser is collimated into parallel beams;

secondly, enabling the light beam to pass through a 4f system, placing a small hole in the focal plane of the 4f system, and carrying out small hole filtering to obtain a high-quality Gaussian light beam;

thirdly, enabling the obtained Gaussian beam to pass through a group of conical lens pairs, wherein each conical lens pair consists of two conical lenses with opposite directions and is used for forming an annular beam;

step four, using a diaphragm to filter stray light at the edge of the light beam;

step five, converting the parallel light beams into linear polarized light through a polarizer; rotating the polarizer to maximize the energy passing through the polarizer; the linear polarized light is orthogonally decomposed into two components, p polarized light and s polarized light;

sixthly, performing phase modulation on the p component by adopting a 0-2 pi vortex phase mask to enable the p component to have a vortex wavefront phase;

step seven, modulating the s component by adopting a vortex phase mask with another starting point changing along with the radius and opposite rotation direction;

and step eight, focusing the light beam after passing through an 1/4 wave plate to obtain the 3D HLF.

Technical Field

The invention belongs to the field of optical engineering, and particularly relates to a novel three-dimensional hollow light field generating device.

Background

A three-dimensional Hollow Light Field (3D Hollow Light Field, hereinafter referred to as "3D HLF") is a focused Light Field in which the Light Field in the central region is zero or low in intensity and the periphery is surrounded by a high-intensity Light Field. Such 3D HLFs have extremely wide applications in fields such as optical measurements, laser machining manufacturing, optical imaging, optical tracking, etc. Particularly, the PPI laser direct writing technology proposed in recent years is a technology for improving the resolution of the traditional laser printing device, and forms a hollow light spot by using another light beam to inhibit the action area of a solid light spot for laser direct writing, so that a higher characteristic size is obtained, and the printing resolution is improved. In addition, in the optical super-resolution technology, both the STED technology (stimulated emission depletion) and the FED technology (fluorescence emission difference) based on the spot scanning imaging system use a hollow light field. The STED technology inhibits a fluorescence light emitting region through a hollow light field, reduces a system Point Spread Function (PSF), and further improves resolution. The FED technology equivalently reduces the PSF of the system in space and time through secondary imaging, and finally improves the contrast and the resolution of the image. It can be seen that, although the principles of the two techniques are different, the hollow light field is a key factor that limits the imaging quality of the two techniques.

Although the current 3D HLF is widely applied and the technical scheme is gradually mature, the contradiction problem caused by the fact that the 3D HLF is generated by adopting single-path continuous light and the defect is caused by light beam coherence cannot be solved. The invention provides a device for generating a novel 3D HLF based on the polarization principle, solves the problems to a certain extent, and can obtain a 3D HLF with higher quality.

Disclosure of Invention

The invention aims to provide a novel 3D HLF generation method. By using the method, the 3D HLF with high quality and no coherent defect can be generated under the condition of single beam light, and the method can be used for further improving the resolution and the precision of the two-photon laser printing device.

The purpose of the invention is realized by the following technical scheme:

the utility model provides a novel three-dimensional hollow light field generates device includes in proper order along the light path: the device comprises a polarizer, an 1/2 half-wave plate, a filter lens, a filter pinhole, a collimating lens, a first cone lens, a second cone lens, a DMD, an SLM, a first 1/4 wave plate, a reflector and a second 1/4 wave plate, wherein light beams are converted into linearly polarized light through the polarizer after entering the device, the light beams are converged by the filter lens after the linearly polarized light passes through the 1/2 wave plate, the filter pinhole is arranged on the focal plane of the filter lens, and the light beams passing through the filter pinhole are collimated into parallel light again by the collimating lens;

the collimated parallel light sequentially passes through the first cone lens and the second cone lens to be incident to the DMD, the light beam is reflected to the left half screen of the SLM by the DMD, then reflected to the reflector, reflected by the reflector and then incident to the right half screen of the SLM, the light beam passes through the first 1/4 wave plate twice between the SLM and the reflector, and the light beam emitted from the right half screen of the SLM passes through the second 1/4 wave plate.

Further, the s-component and p-component energies are made the same by rotating 1/2 the waveplate.

Furthermore, the filtering aperture is used for filtering stray light at the edge and improving the quality of light beams.

Furthermore, the first cone lens and the second cone lens form a lens group for modulating the energy distribution of the light beam to make the energy distribution of the cross section of the light beam annular.

Further, different phase diagrams are loaded on the left half screen and the right half screen of the SLM, vortex phases are loaded on the left side, and vortex phases with starting points changing along with the radius and opposite in rotation direction are loaded on the right side.

Further, the s light and the p light are converted into circularly polarized light with opposite rotation directions by the second 1/4 wave plate 12, and are coherently superposed to form a light beam with complex polarization state distribution, and the light beam is focused to form the 3D HLF.

A novel three-dimensional hollow light field generation method comprises the following steps:

firstly, laser emitted by a laser is collimated into parallel beams;

secondly, enabling the light beam to pass through a 4f system, placing a small hole in the focal plane of the 4f system, and carrying out small hole filtering to obtain a high-quality Gaussian light beam;

thirdly, enabling the obtained Gaussian beam to pass through a group of conical lens pairs, wherein each conical lens pair consists of two conical lenses with opposite directions and is used for forming an annular beam;

step four, using a diaphragm to filter stray light at the edge of the light beam;

step five, converting the parallel light beams into linear polarized light through a polarizer; rotating the polarizer to maximize the energy passing through the polarizer; the linear polarized light is orthogonally decomposed into two components, p polarized light and s polarized light;

sixthly, performing phase modulation on the p component by adopting a 0-2 pi vortex phase mask to enable the p component to have a vortex wavefront phase;

step seven, modulating the s component by adopting a vortex phase mask with another starting point changing along with the radius and opposite rotation direction;

and step eight, focusing the light beam after passing through an 1/4 wave plate to obtain the 3D HLF.

The invention has the beneficial effects that: compared with the traditional method, the method generates the 3DHLF with higher quality, and can form the 3D HLF by adopting single-path light without generating coherent defects. The device provided by the invention can simultaneously realize aberration optimization by adopting the SLM to regulate and control the light beam, and can further improve the light beam quality by adopting the annular light beam to block off the central low-frequency part.

Drawings

FIG. 1 is a schematic diagram of the 3D HLF generation method of the present invention.

Fig. 2 is a schematic structural diagram of a novel 3D HLF generation apparatus according to the present invention.

Fig. 3a and 3b are diagrams of 3D HLF generated by the conventional method and 3D HLF generated by the method of the present invention, respectively.

Detailed Description

The invention will be further explained with reference to the drawings.

As shown in fig. 1, the basic principle of the present invention is as follows:

the incident beam is decomposed into two orthogonal components, an s-component and a p-component. And regulating the p component by adopting a 0-2 pi vortex phase mask, regulating the s component by adopting another vortex phase mask, wherein 0-2 pi vortex phase masks for regulating the s light have different 0 phase starting points on different radiuses, and the rotation direction is opposite to the vortex direction of the vortex phase masks for regulating the p component. The modulated light beams are combined, converted into circularly polarized light with opposite rotation directions through the same 1/4 wave plate, and the two beams are interfered to form columnar vector polarized light with a complex polarization state. The beam is focused to obtain the desired 3D HLF.

As shown in fig. 2, an apparatus for generating a 3D HLF according to the present invention sequentially includes, along an optical path: polarizer 1, 1/2 wave plate 2, filter lens 3, filter aperture 4, collimating lens 5, first axicon 6, second axicon 7, DMD (digital micromirror device) 8, SLM (spatial light modulator) 9, first 1/4 wave plate 10, mirror 11 and second 1/4 wave plate 12. After entering the device, the light beam is converted into linearly polarized light through the polarizer 1, the linearly polarized light is converged by the filter lens 3 after passing through the 1/2 wave plate 2, the focal plane of the filter lens 3 is provided with the filter aperture 4, and the light beam passing through the filter aperture 4 is collimated into parallel light again by the collimating lens 5. The collimated parallel light sequentially passes through the first axicon 6 and the second axicon 7 and enters the DMD 8. The light beam is reflected to the left half screen of the SLM 9 by the DMD 8, then reflected to the reflecting mirror 11, reflected by the reflecting mirror 11 and then incident to the right half screen of the SLM 9, passes through the first 1/4 wave plate 10 twice between the SLM 9 and the reflecting mirror 11, and exits from the right half screen of the SLM 9 through the second 1/4 wave plate 12.

Wherein 1/2 wave plate 2 is used to rotate the polarization direction. The linearly polarized light can be split into two orthogonal components, the s-component and the p-component, and rotating 1/2 plate 2 can adjust the energy ratio of the two components. The two components are theoretically made to be identical in energy.

Wherein, the filtering aperture 4 is used for filtering stray light at the edge and improving the quality of light beams.

The first cone lens 6 and the second cone lens 7 form a lens group for modulating the energy distribution of the light beam to make the energy distribution of the cross section of the light beam annular.

The DMD 8 is used to further shape the energy of the light beam, so that the energy distribution of the annular light beam is more uniform.

Different phase diagrams are loaded on the left half screen and the right half screen of the SLM 9, vortex phases are loaded on the left side, and vortex phases with starting points changing along with the radius and opposite in rotation direction are loaded on the right side. Since the SLM device has polarization selectivity, it is assumed here to respond only to s light. When the beam is incident on the left half-screen of the SLM 9, only the s-light is vortex phase modulated. After twice passing through the first 1/4 wave plate 10, the handedness is rotated by 90 degrees, and the s light and the p light are interchanged. When the light beam is incident on the right half screen, the previously modulated p light becomes s light, which is modulated by the phase mask on the right half screen.

Further, the s-light and the p-light are converted into circularly polarized light with opposite handedness by the second 1/4 wave plate 12, and are coherently superposed to form a light beam with a complex polarization state distribution, which is focused to form the desired 3D HLF.

The above description is only exemplary of the preferred embodiments of the present invention, and is not intended to limit the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.