TWI859788B - Immersed holographic shooting structure - Google Patents

Abstract

An immersion holographic filming structure has a medium in a liquid state, a recording material immersed in the medium, and a rotation center is defined on the recording material. The recording material rotates in the medium about the rotation center, and the recording material extends an imaginary center line perpendicular to the recording light direction to both sides about the rotation center; wherein there is a rotation angle between the recording material and the imaginary center line, the long side of the recording material is defined as a hypotenuse, and a first side and a second side are respectively extended from both ends of the hypotenuse in a direction away from the recording material, and an imaginary prism is respectively formed in the medium above and below the recording material to sandwich the recording material, and the angle of the bottom angle of the imaginary prism is equal to the rotation angle.

Description

Immersed holographic shooting structure

The present invention relates to grating manufacturing, and in particular to an immersion holographic filming structure.

Currently, there is a shooting structure for producing holographic grating materials, which is to sandwich the recording material between two prisms to produce the grating material. The relationship between the recording light and the reconstructed light of the grating material is closely related to the bottom angle of the prism.

However, since the wavelengths of commercial lasers are currently fixed to a few specific types, if one wants to obtain reconstruction light of other wavelengths using a grating material made from recorded light of a certain commercial laser wavelength, it is necessary to change the bottom angle of the prism to achieve this. Therefore, when reconstruction light of different wavelengths is required, prisms of different bottom angles are required, and some bottom angles have very difficult values, making the production and quantity of prisms more troublesome and not economical.

In view of this, how to solve the above problems is the primary issue that the present invention aims to solve.

The main purpose of the present invention is to provide an immersion holographic shooting structure, in which a recording material is immersed in a liquid medium, and the angle between the recording material and an imaginary center line is changed by rotating the recording material, and the angle is equal to the angle of the bottom angle of the imaginary prism. The angle of the bottom angle of the imaginary prism is changed, and the wavelength of the reconstructed light is changed accordingly, so as to produce a holographic grating material that meets the expectations, and has the effect of improving precision and versatility.

To achieve the above-mentioned purpose, the present invention provides an immersion holographic filming structure, including: A medium in liquid state; A recording material disposed in the medium, and a rotation center is defined on the recording material, the recording material rotates in the medium about the rotation center, and the recording material extends an imaginary center line to both sides perpendicular to the recording light direction about the rotation center; There is a rotation angle between the recording material and the imaginary center line, the long side of the recording material is defined as a hypotenuse, and a first side and a second side perpendicular to and intersecting the first side are respectively extended from both ends of the hypotenuse in a direction away from the recording material, and an imaginary prism is respectively formed in the medium on both sides of the recording material to sandwich the recording material, and the bottom angle of the imaginary prism is equal to the rotation angle.

Preferably, the refractive index of the recording material is close to the refractive index of the medium.

The above-mentioned objects and advantages of the present invention can be more clearly understood from the following detailed description of the selected embodiments and the accompanying drawings.

Please refer to Figures 1 to 7, which are the immersion holographic shooting structure provided by the present invention, which has a medium 1 and a recording material 2, wherein:

The medium 1 is in liquid state and is contained in a transparent container.

The recording material 2 is immersed in the medium 1, and a rotation center C is defined on the recording material 2. The recording material 2 rotates in the medium 1 about the rotation center C, and the recording material 2 extends an imaginary center line L to both sides perpendicular to the direction of a recording light 51 about the rotation center C. The refractive index of the recording material 2 is close to that of the medium 1.

Please continue to refer to Figure 2. First, a recording material 2 is placed, and an emitter 41 emits a recording light 51 with a wavelength of 300 to 850 nm. The recording light 51 passes through an electronic shutter 42, a filter 43, and a collimating lens 44 and then enters the medium 1. After penetrating the recording material 2, the recording light passes through the medium 1 and is reflected back by the reflector 45 to form an object light 52. The recording light 51 and the object light 52 will form interference in the recording material 2. Accordingly, as shown in FIG. 3 , the recording material 2 can be modulated into a volume hologram 2′ (polarization-selective volume hologram gratings, PVHGs) that can diffract the reconstruction light at an angle of _θd of about 48.19 degrees after being incident with the reconstruction light of a wavelength of 200 to 600 nm, thereby converting the transmitted light into P polarized light, where _θd is the diffraction angle caused by the incident reconstruction light. Alternatively, as shown in FIG. 4 , the recording material 2 can be modulated into a volume hologram 2′ that can diffract the reconstruction light at an angle of _θd of about 60 degrees after being incident with the reconstruction light of a wavelength of 200 to 600 nm, thereby converting the transmitted light into S polarized light. Alternatively, as shown in FIG. 3 , the recording material 2 can be modulated into a volume hologram 2' in which, after being incident with reconstruction light having a wavelength of 200 to 600 nm, the reconstruction light is diffracted at an angle _θd of about 85 degrees, thereby converting the transmitted light into P-polarized light.

Please refer to Figures 5 to 7. When the S and P polarized light are just separated (the peaks and troughs of the S and P polarized light patterns, respectively), the values of the equivalent modulated refractive index (effective refractive modulation) N ₁ on the horizontal axis are approximately 1.2 (as shown in Figure 5) and 0.75 (as shown in Figure 6), respectively. The equivalent modulated refractive index N ₁ =n ₁ ·d ₂ /λ ₂ , where n ₁ is the amplitude of the modulated refractive index, which is proportional to the exposure time t; d ₂ is the thickness of the recording material 2 after exposure; λ ₂ is the wavelength of the reconstruction light. From the above formula, it can be seen that the equivalent modulated refractive index N ₁ is positively correlated with the thickness d ₂ of the recording material 2 after exposure and the exposure time t.

The thickness _d2 of the recording material 2 after exposure and the exposure time t cannot increase infinitely, so the value of _n1 cannot increase infinitely either. Therefore, the value of _N1 has a certain range, so that the thickness _d2 of the recording material 2 after exposure and the exposure time t can be controlled within a reasonable range. In addition, the diffraction angle θ _d caused by the incident reconstruction light also affects the value of the equivalent modulated refractive index N _1. As shown in FIG. 5 , when the diffraction angle θ _d is 48.19 degrees, the equivalent modulated refractive index N ₁ is approximately 1.2; as shown in FIG. 6 , when the diffraction angle θ _d is 60 degrees, the equivalent modulated refractive index N ₁ is approximately 0.75. Therefore, the larger the diffraction angle θ _d caused by the incident reconstruction light, the smaller the equivalent modulated refractive index N ₁ , so that the thickness d ₂ and exposure time t of the recording material 2 after exposure are within a reasonable range, and the S and P polarized light can be effectively separated.

Furthermore, when the diffraction angle _θd is greater than 81 degrees, the S and P polarized lights can be almost completely separated. For example, as shown in Figure 7, when the diffraction angle _θd is 85 degrees, the equivalent modulation refractive index _N1 is approximately 0.15. At this time, the S and P polarized lights are almost completely separated, thereby recording the thickness _d2 of the material 2 after exposure and the exposure time t to obtain more reasonable conditions and design space.

In addition, the relationship between the recorded light wavelength λ ₁ , the reconstructed light wavelength λ ₂ and the angle θ _p1 of the prism bottom angle is: Where _nf1 is the refractive index of the recording material corresponding to the recording light; _nf2 is the refractive index of the recording material corresponding to the reconstruction light; _np is the refractive index of the medium corresponding to the recording light; _d1 is the thickness of the recording material before exposure; _d2 is the thickness of the recording material after exposure. From the above formula, it can be seen that the laser light (i.e., recording light) emitted by common commercial laser emitters has a preset wavelength _λ1 . Therefore, under a certain recording light wavelength _λ1 , different reconstruction light wavelengths _λ2 can be obtained by changing the angle _θp1 of the bottom angle of the prism.

It should be noted that incomplete separation of S and P polarized light is sometimes necessary in actual situations. Under the same diffraction angle, such as Figure 5, adjusting the equivalent modulation refractive index _N1 can achieve incomplete separation of S and P polarized light, and adjusting the angle _θp1 of the bottom angle of the prism can obtain different reconstructed light wavelengths _λ2 , and thus obtain different equivalent modulation refractive indices _N1 . Accordingly, changing the angle _θp1 of the bottom angle of the prism can also achieve the effect of incomplete separation of S and P polarized light.

Therefore, the recording material 2 provided by the present invention has a rotation angle θ with the imaginary center line L, the long side of the recording material 2 is defined as a hypotenuse 31, and a first side 32 and a second side 33 perpendicular to and intersecting the first side 32 are respectively extended from both ends of the hypotenuse 31 in a direction away from the recording material 2, and an imaginary prism 3 with a right angle is respectively formed in the medium 1 on both sides of the recording material 2 to clamp the recording material 2, and the angle θ _p1 of the bottom angle of the imaginary prism 3 is equal to the rotation angle θ, and different angles θ _p1 of the bottom angle of the imaginary prism 3 are obtained by changing the rotation angle θ between the recording material 2 and the imaginary center line L.

In summary, the recording material 2 is immersed in the medium 1, and the recording material 2 is rotated in the medium 1 about the rotation center C, thereby changing the rotation angle θ between the recording material 2 and the imaginary center line L. Since the angle θ _p1 of the bottom angle of the imaginary prism 3 is equal to the rotation angle θ, the angle θ p1 of the bottom angle of the imaginary prism 3 can be adjusted to obtain different angles θ _p1 . Furthermore, when only the wavelength of existing commercial laser light is selected as the recording light wavelength λ ₁ , there is no need to manufacture a right-angle prism corresponding to the reconstruction light wavelength λ _2. Only the rotation angle θ of the recording material 2 needs to be adjusted to obtain different reconstruction light wavelengths λ ₂ , so as to manufacture a volume hologram that meets the expectations, thereby having the effect of improving precision and versatility.

The disclosure of the above embodiments is only used to illustrate the present invention, not to limit the present invention. Therefore, any change in numerical values or replacement of equivalent elements should still fall within the scope of the present invention.

In summary, those familiar with the art will be able to understand that the present invention can achieve the aforementioned purpose and is in compliance with the provisions of the Patent Law, and therefore can file an application in accordance with the law.

Medium 1 Recording material 2 Volume hologram 2' Imaginary prism 3 Hypotenuse 31 First side 32 Second side 33 Emitter 41 Electronic shutter 42 Filter 43 Collimating lens 44 Reflector 45 Recording light 51 Object light 52 Rotation center C Imaginary center line L

Figure 1 is a schematic diagram of the equipment for preparing a volume hologram of the present invention. Figure 2 is a schematic diagram of the rotation angle of the recording material of the present invention. Figure 3 is a schematic diagram of the diffraction phenomenon caused by the incident reconstruction light of the present invention on the volume hologram. Figure 4 is a schematic diagram of the diffraction phenomenon caused by the incident reconstruction light of the present invention on the volume hologram at different angles. Figure 5 is a schematic diagram of the curves of S and P polarized light when θ _d is 48.19 degrees of the present invention. Figure 6 is a schematic diagram of the curves of S and P polarized light when θ _d is 60 degrees of the present invention. Figure 7 is a schematic diagram of the curves of S and P polarized light when θ _d is 85 degrees of the present invention.

Medium 1 Recording material 2 Imaginary prism 3 Hypotenuse 31 First side 32 Second side 33 Emitter 41 Electronic shutter 42 Filter 43 Collimating lens 44 Reflector 45 Recording light 51 Object light 52 Rotation center C Imaginary center line L

Claims (2)

An immersion holographic filming structure includes: a medium in liquid state; a recording material immersed in the medium, and a rotation center is defined on the recording material. The recording material rotates in the medium about the rotation center, and the recording material extends an imaginary center line perpendicular to the recording light direction from the rotation center to both sides; wherein there is a rotation angle between the recording material and the imaginary center line, the long side of the recording material is defined as a hypotenuse, and a first side and a second side perpendicular to and intersecting the first side are respectively extended from both ends of the hypotenuse in a direction away from the recording material, and an imaginary prism is respectively formed in the medium on both sides of the recording material to sandwich the recording material, and the bottom angle of the imaginary prism is equal to the rotation angle. An immersion holographic shooting structure as described in claim 1, wherein the refractive index of the recording material is close to the refractive index of the medium.

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