阅读说明：本技术 一种用于制备彩色全息波导光栅的自动化曝光系统 (Automatic exposure system for preparing color holographic waveguide grating ) 是由 沈忠文 张宇宁 杨粲然 左濮深 韩月明 程皓 林加旻 李晓华 王保平 于 2020-05-22 设计创作，主要内容包括：本发明公开了一种用于制备彩色全息波导光栅的自动化曝光系统,所述自动化曝光系统包括曝光参数输入模块,曝光角度、曝光位置计算模块,以及激光光源、准直扩束装置、光束曝光角度调控装置、曝光位置调控装置及干板夹具等光路模块,所述系统可计算并电控调节曝光光束干涉角度、全息干板曝光位置等,实现自动化制备彩色全息波导光栅的效果。(The invention discloses an automatic exposure system for preparing a color holographic waveguide grating, which comprises an exposure parameter input module, an exposure angle and exposure position calculation module, and light path modules such as a laser light source, a collimation and beam expanding device, a light beam exposure angle regulation and control device, an exposure position regulation and control device, a dry plate clamp and the like.)

1. An automated exposure system for preparing a color holographic waveguide grating, comprising: the system comprises a grating parameter setting module, an exposure angle calculation module, an exposure position calculation module, an electric control drive control module and an interference exposure system, wherein the deflection angle of a reflector and the position of an exposure point are calculated by inputting the included angle between object light and reference light and a volume grating, so that a mechanical device is controlled to automatically adjust the position of the volume grating and the exposure light path, and the accuracy of the volume holographic grating exposure light path under different design parameters is met;

the grating parameter setting module is used for setting grating exposure parameters, including setting reproduction light incidence and diffraction angles, recording light wavelength, recording light intensity and exposure time;

the exposure angle calculation module calculates and obtains the interference angle of the reference light and the object light according to the grating parameter, the recording light wavelength and the grating exposure parameter based on the K vector circle and the Bragg diffraction theorem;

the exposure position calculation module is used for calculating the exposure position of the holographic dry plate according to the interference angle of the two beams of recording light and the relative position relationship between the object light and the reference light optical path on the exposure platform;

the electric control drive control module inputs a digital control signal to the drive controller by a computer according to the recorded light interference angle and the holographic dry plate exposure position, and the drive controller inputs current signals to the electric control rotary table and the electric control translation table and is used for controlling the rotation angle of the electric control rotary table and the displacement distance of the electric control translation table;

the interference exposure system comprises a single longitudinal mode laser, an electric control shutter, a light splitting, beam expanding and collimating optical system, an electric control recording light exposure angle regulating and controlling device and an electric control exposure position regulating and controlling device.

2. The automated exposure system for preparing a color holographic waveguide grating of claim 1, wherein: in the interference exposure system, the beam splitting, expanding and collimating optical system comprises a diaphragm, a dielectric film reflector, a beam splitting prism, a spatial optical filter and a collimating lens; laser beams emitted by the single longitudinal mode laser firstly pass through the electric control shutter, enter the space optical filter and are expanded into light spots with divergence angles, the light spots are shaped by the diaphragm and then pass through the collimating lens to form collimated light beams with corresponding sizes and shapes, and then the collimated light beams are divided into two beams of collimated light with equal energy through the beam splitter prism.

3. The automated exposure system for preparing a color holographic waveguide grating of claim 2, wherein: and the two beams of collimated light generated by the beam splitting, expanding and collimating optical system are respectively reflected by the dielectric film reflector to adjust the final interference angle of the light beams.

4. The automated exposure system for preparing a color holographic waveguide grating of claim 1, wherein: in the interference exposure system, the electric control recording light exposure angle regulation and control device consists of a plurality of sets of dielectric film reflectors, an electric control rotating platform and a driving controller, wherein the electric control rotating platform is used for regulating and controlling the angles of the dielectric film reflectors.

5. The automated exposure system for preparing a color holographic waveguide grating of claim 1, wherein: in the interference exposure system, the electric control exposure position regulating and controlling device consists of an electric control translation table, a dry plate holder and a driving controller, and can move the holographic dry plate to the position of the interference position of two beams of recording light obtained by calculation of the exposure position calculating module.

Technical Field

The invention belongs to the holographic optical technology, particularly relates to a holographic interference exposure technology, and particularly relates to an automatic exposure system for preparing a color holographic waveguide grating.

Background

The volume holographic grating is a diffraction grating prepared by utilizing holographic interference technology, and the grating is characterized in that interference fringes with alternate light and shade are formed in a photosensitive material through two coherent laser beams emitted by a laser, so that the refractive index distribution of the photosensitive material is changed according to the light and shade fringes, the refractive index in a light fringe area is increased, the refractive index in a dark fringe area is decreased in the interference exposure process, and finally a refractive index modulation grating is formed in the material.

Compared with the traditional engraved grating, the volume holographic grating has the advantages of less stray light, high + 1-order diffraction efficiency, good wavelength and angle selectivity and the like, so the volume holographic grating gradually replaces the traditional engraved grating in many fields. The grating can be divided into a reflection type holographic grating and a transmission type holographic grating according to the diffraction direction and the grating vector direction of the reproduced light beam, and the transmission type holographic grating is widely applied to the fields of light splitting devices in high-resolution spectrometers, solar collectors, optical communication and the like; compared with a transmission type volume holographic grating, the reflection type volume holographic grating has larger diffraction angle response bandwidth and narrower diffraction wavelength response bandwidth (lower dispersion), and is mainly applied to the field of holographic waveguide display.

In the practical application of the holographic waveguide display field, the volume holographic grating is used as a holographic optical coupling device for coupling light beams with image information into a waveguide for propagation and then coupling the light beams into human eyes. The grating period of the holographic waveguide grating is hundreds of nanometers, and the grating parameters of the input grating and the output grating are strictly symmetrical, so that the holographic waveguide grating has extremely high requirements on the precision of the preparation process of the holographic waveguide grating. At present, the traditional process for preparing the color volume holographic grating is to manually build a light path to adjust and record the light exposure angle, and the accuracy and consistency of the method are difficult to ensure. Meanwhile, different exposure light paths are required to be built for adjusting the angle of the recording light in the process of preparing the volume holographic grating with different parameters, so that the preparation time and difficulty are greatly increased. Therefore, how to rapidly adjust an exposure light path to realize a volume holographic grating preparation device with high consistency, good repeatability and high precision is a key research direction in the volume holographic technology nowadays.

Disclosure of Invention

The purpose of the invention is as follows: in order to improve the preparation efficiency and accuracy of the waveguide grating, improve the production efficiency and shorten the process time, the invention provides an automatic exposure system for preparing the color volume holographic grating.

The technical scheme is as follows: an automatic exposure system for preparing a color holographic waveguide grating calculates the deflection angle of a reflector and the position of an exposure point by inputting an included angle between object light, reference light and a light grating, and further controls a mechanical device to automatically adjust the position and the exposure light path of a volume grating so as to meet the precision of the exposure light path of the volume holographic grating under different design parameters, and the system comprises a grating parameter setting module, an exposure angle calculation module, an exposure position calculation module, an electric control drive control module and an interference exposure system;

the grating parameter setting module is used for setting grating exposure parameters, including setting reproduction light incidence and diffraction angles, recording light wavelength, recording light intensity and exposure time;

the exposure angle calculation module calculates and obtains the interference angle of the reference light and the object light according to the grating parameter, the recording light wavelength and the grating exposure parameter based on the K vector circle and the Bragg diffraction theorem;

the exposure position calculation module is used for calculating the exposure position of the holographic dry plate according to the interference angle of the two beams of recording light and the relative position relationship between the object light and the reference light optical path on the exposure platform;

the electric control drive control module inputs a digital control signal to the drive controller by a computer according to the recorded light interference angle and the holographic dry plate exposure position, and the drive controller inputs current signals to the electric control rotary table and the electric control translation table and is used for controlling the rotation angle of the electric control rotary table and the displacement distance of the electric control translation table;

the interference exposure system comprises a single longitudinal mode laser, an electric control shutter, a light splitting, beam expanding and collimating optical system, an electric control recording light exposure angle regulating and controlling device and an electric control exposure position regulating and controlling device.

Furthermore, in the interference exposure system, the beam splitting, expanding and collimating optical system comprises a diaphragm, a dielectric film reflecting mirror, a beam splitting prism, a spatial optical filter, a collimating lens and other precise optical devices. Laser beams emitted by the single longitudinal mode laser firstly pass through the electric control shutter, enter the space optical filter and are expanded into light spots with a certain divergence angle, the light spots are shaped by the diaphragm and then pass through the collimating lens to form collimated light beams with a certain size and shape, and then the collimated light beams are divided into two beams of collimated light with equal energy by the beam splitter prism.

The electric control recording light exposure angle regulation and control device is composed of one set or more than one set of dielectric film reflecting mirrors, an electric control rotating platform and a driving controller, and the electric control rotating platform is used for regulating and controlling the angles of the dielectric film reflecting mirrors.

And the two beams of collimated light generated by the beam splitting, expanding and collimating optical system are respectively reflected by the dielectric film reflector to adjust the final interference angle of the light beams.

The electric control exposure position regulating and controlling device consists of an electric control translation table, a dry plate holder and a driving controller, and can move the holographic dry plate to the position of the interference of two beams of recording light obtained by calculation of the exposure position calculating module.

Has the advantages that: compared with the prior art, the method calculates the deflection angle of the reflector and the position of the exposure point by inputting the included angle between the object light, the reference light and the volume grating, thereby controlling a mechanical device to automatically adjust the position and the exposure light path of the volume grating, meeting the requirement of the precision of the exposure light path of the volume holographic grating under different design parameters, enabling the precision of the electric control rotation angle to reach 0.05 degree and the precision of the electric control displacement to reach 60 microns, saving the time for manually adjusting the exposure light path, improving the exposure efficiency and providing guarantee for the mass production of the volume holographic grating with different grating parameters.

Drawings

FIG. 1 is a schematic diagram of the system of the present invention;

FIG. 2 is a schematic diagram of the calculation of the intersection point of two laser beams according to the present invention;

FIG. 3 is a schematic diagram of a beam expanding, collimating and beam splitting optical system in the system of the present invention;

FIG. 4 is a schematic view of an interference exposure system in embodiment 1;

FIG. 5 is a schematic view of an interference exposure system in embodiment 2;

fig. 6 is a schematic view of an interference exposure system in embodiment 3.

Detailed description of the preferred embodiments

In order to explain the technical solutions disclosed in the present invention in detail, the present invention will be further explained with reference to the accompanying drawings and specific examples.

The invention relates to an automatic exposure system for preparing a color holographic waveguide grating. The deflection angle of the reflector and the position of an exposure point are calculated by inputting the included angle between object light, reference light and the optical grating, so that the mechanical device is controlled to automatically adjust the position and the exposure light path of the volume holographic grating, the requirement on the precision of the exposure light path of the volume holographic grating under different design parameters is met, the precision of an electric control rotation angle can reach 0.05 degree, the precision of electric control displacement can reach 60 micrometers, the time for manually adjusting the exposure light path can be saved, the exposure efficiency is improved, and the guarantee is provided for the mass production of the volume holographic grating with different grating parameters. And to implement automated parameter calculation and control processes, including the need to achieve different accuracies based on the combinatorial design of existing exposure control devices.

The automatic exposure system of the invention is shown in figure 1 and mainly comprises a grating parameter setting module, an exposure angle calculation module, an exposure position calculation module, an electric control drive control module and an interference exposure system.

The grating parameter setting module is used for setting grating exposure parameters, such as reproduction light incidence and diffraction angles, recording light wavelength, recording light intensity, exposure time and the like.

And the exposure angle calculation module calculates and obtains the interference angle of the reference light and the object light according to exposure parameters such as grating parameters, recording light wavelength and the like based on the K vector circle and the Bragg diffraction theorem.

And the exposure position calculation module is used for calculating the exposure position of the holographic dry plate according to the interference angle of the two beams of recording light and the relative position relationship between the object light and the reference light path on the exposure platform. As shown in fig. 2, the lying plane of the holographic plate is parallel to the x-axis. The position of the mirror 1 is represented by (x) taking the mirror 2 shown in FIG. 2 as the origin of coordinates₀,y₀) The known value, (X, Y) is the coordinates of the intersection of the two diverging beams. Theta₁And theta₂The angular deflection of the two mirrors.

From geometrical relationships

The above two equations hold for arbitrary wavelength reproduction light.

Wherein the content of the first and second substances,

θ′＝π-θ

is to record the included angle of light and satisfy the following formula

Namely, it is

Wherein k is₀、k₁For recording the magnitude of the light wave vector, λ₀、λ₁The recording light and the reproduction light have different wavelengths.

From the above formula and geometric relationship, the coordinates (X, Y) of the convergence point of the two recorded beams are

Therefore, the track of the exposure point of the holographic dry plate can be deduced according to a convergent point coordinate calculation formula, so that the translation track of the electrically controlled translation stage can be further deduced.

The electric control drive control module inputs a digital control signal to the drive controller by a computer according to the recorded light interference angle and the holographic dry plate exposure position, and the drive controller further inputs current signals to the electric control rotary table and the electric control translation table and is used for controlling the rotation angle of the electric control rotary table and the displacement distance of the electric control translation table.

The interference exposure system comprises a single longitudinal mode laser, an electric control shutter, a light splitting, beam expanding and collimating optical system, an electric control recording light exposure angle regulating and controlling device, an electric control exposure position regulating and controlling device and the like.

As shown in fig. 3, the beam splitting, expanding and collimating optical system includes a diaphragm, a dielectric film mirror, a beam splitting prism, a spatial light filter, a collimating lens, and other precision optical devices. Laser beams emitted by a single longitudinal mode laser firstly enter a spatial light filter 201 to be expanded into beams with a certain divergence angle, the expanded beams pass through a collimating lens 202 to form collimated beams, the size of light spots of the collimated beams is adjusted through a diaphragm 203, the collimated beams are divided into two beams of collimated light with equal energy through a beam splitter prism 204, and one beam of collimated light is reflected by a dielectric film reflecting mirror 205 and then keeps parallel with the other beam of collimated light.

The electric control recording light exposure angle regulating and controlling device consists of one or more sets of medium film reflecting mirrors, an electric control rotating platform, a driving controller and other optical precision devices, wherein the electric control rotating platform is used for regulating and controlling the angles of the medium film reflecting mirrors.

Two beams of collimated light generated by the beam splitting, expanding and collimating optical system are respectively reflected by the dielectric film reflector to adjust the final interference angle of the light beams.

The electric control exposure position regulating and controlling device consists of precise optical devices such as an electric control translation table, a dry plate holder, a driving controller and the like, and can move the holographic dry plate to the position of the interference of two beams of recording light obtained by calculation of the exposure position calculating module.

Specific optical path designs of the different interferometric exposure systems of the present invention are described in detail below, as shown in FIGS. 4-6. The recording light exposure angle and the exposure point position of the interference exposure system are regulated and controlled according to the calculation results of the exposure angle calculation module and the exposure position calculation module. The on-off of the light path is controlled by an electric control shutter, when the light path is automatically adjusted according to the exposure parameter calculation result, the shutter is opened, and the opening time is determined by the exposure time input by the grating parameter calculation module. After exposure is finished, the shutter is closed.