Zoom liquid crystal lens assembly

Abstract

The invention discloses a zoom liquid crystal lens assembly which comprises a common lens, an adjustable liquid crystal wave plate and two liquid crystal polarization lenses. The liquid crystal wave plate and the liquid crystal polarizing lens are externally connected with an electrode group, the electrode group comprises a first electrode layer and a second electrode layer, the first electrode layer and the second electrode layer are arranged between the adjustable liquid crystal wave plate and the liquid crystal polarizing lens, and the electrode group is regulated and controlled by an external electric field; the liquid crystal wave plate is used for adjusting the rotation direction of incident light in a circular polarization state, and the common lens is a positive lens and is used for maintaining all focal lengths of the zoom lens group to be positive focal lengths. By controlling the polarization state of incident light and the external voltage, focal length switching of the liquid crystal polarization lens can be achieved, the purpose of equal-interval zooming is achieved through the optimized lens distance and focal length, the zooming effect of seven positions is achieved in combination with the liquid crystal polarization zooming lens set, and good application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid crystal lenses, and in particular to a variable focus liquid crystal lens assembly. Background Art

[0002] Lenses are widely used in daily life and scientific research and are one of the basic optical devices. The speed of light propagation in media and air is different. Traditional optical lenses use this property to control the shape of optical materials and modulate the wavefront through the optical path difference caused by light from different paths, which has the effect of deflecting the light beam. Liquid crystal is an intermediate state between solid and liquid, it has the fluidity of liquid and the anisotropic grid of crystal. Liquid crystal molecules are modulated by an external electric field, so that compared with solid-state lenses, liquid crystal lenses can use external electric fields to adjust their optical properties according to usage requirements. Liquid crystal polarization lens is a geometric phase optical element that focuses and controls polarized light beams by modulating the geometric phase difference of light wavefronts.

[0003] However, lenses with variable focus capabilities only have a limited number of zooms. For specific usage scenarios, it is difficult to achieve equal-interval zoom and to achieve the above-mentioned equal-interval zoom function through different lens spacing and focal lengths. To this end, we propose a variable focus liquid crystal lens assembly to address the problem of how liquid crystal lenses can achieve multi-point zoom and achieve different numbers of zooms. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a variable focus liquid crystal lens assembly.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A variable focus liquid crystal lens assembly includes a common lens, an adjustable liquid crystal wave plate and two liquid crystal polarization lenses;

[0007] The liquid crystal wave plate and the liquid crystal polarization lens are externally connected to an electrode group, the electrode group includes a first electrode layer and a second electrode layer, the first electrode layer and the second electrode layer are arranged between the adjustable liquid crystal wave plate and the liquid crystal polarization lens, and the electrode group is regulated by an external electric field;

[0008] The liquid crystal wave plate is used to adjust the rotation direction of the circular polarization state of the incident light, and the ordinary lens is a positive lens, which is used to maintain that all focal lengths of the zoom lens group are positive focal lengths;

[0009] The formula for the focal length of the three-light combination consisting of the ordinary lens and the liquid crystal polarizing lens is:

[0010] ψ=ψ0+ψ1+ψ2-d 01 ψ0(ψ1+ψ2)-d 12ψ2(ψ0+ψ1)+d 01 d 12 ψ0ψ1ψ2

[0011] Among them, ψ0, ψ1 and ψ2 are the optical powers of the three light groups, d 01 and d 12 are the spatial intervals between the three light groups respectively; the focal length of the lens group is calculated by this formula.

[0012] Preferably, the range of the parameters is defined as follows: 100 mm < f < 200 mm, 5 mm < d < 10 mm, wherein f is the focal length, and d is the spatial interval between the light groups.

[0013] Preferably, the liquid crystal polarization lens is prepared using a Mach-Zehnder interference optical path. After the ultraviolet laser passes through a pinhole filter, it is collimated by a collimating lens and then separated into an S light beam and a P light beam by a polarization beam splitter prism. The S light is a linearly polarized light parallel to the incident plane, and the P light is a linearly polarized light perpendicular to the incident plane.

[0014] Preferably, the S light and the P light are respectively reflected by a reflector and arrive at the same polarization beam splitter prism, thereby achieving the superposition of the two beams of light.

[0015] Preferably, a lens is placed on the S optical path to transform the plane wave into a spherical wave.

[0016] Preferably, the liquid crystal polarization lens includes a first liquid crystal polarization lens and a second liquid crystal polarization lens, and the relationship between the focal length and the wavelength of the liquid crystal polarization lens is:

[0017] Among them, F is the focal length used, λ is the wavelength used, λ0 is the exposure wavelength, and Z0 is the propagation distance of the spherical wave from the rear focus of the ordinary lens.

[0018] Preferably, the focal length of the liquid crystal polarization lens can be controlled by controlling the exposure position Z0.

[0019] Preferably, a λ / 2 wave plate is placed before the first polarization beam splitter prism to adjust the linear polarization direction of the laser and indirectly adjust the splitting ratio of the two beams of light; a λ / 4 wave plate is placed before the next polarization beam splitter prism to convert the two orthogonal linear polarized lights into two orthogonal circular polarized lights.

[0020] The invention provides a variable focus liquid crystal lens assembly, which has the following beneficial effects:

[0021] The focal length of the liquid crystal polarization lens can be switched by controlling the polarization state of the incident light and the external voltage, and the purpose of equal-interval zooming can be achieved by optimizing the lens spacing and focal length. Combined with the liquid crystal polarization zoom lens group, a zoom effect in 7 positions is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic structural diagram of a liquid crystal polarization variable focus lens group of a variable focus liquid crystal lens assembly proposed by the present invention;

[0023] Figure 2 A schematic structural diagram of a liquid crystal polarization variable focus lens group of a variable focus liquid crystal lens assembly proposed by the present invention;

[0024] Figure 3 A distribution diagram of the point distances of a zoom system of a zoom liquid crystal lens assembly proposed by the present invention;

[0025] Figure 4 This is a morphology image of a variable focus liquid crystal lens assembly proposed by the present invention under a polarized light microscope;

[0026] Figure 5 A liquid crystal polarization lens interference exposure optical path of a variable focus liquid crystal lens assembly proposed by the present invention;

[0027] Figure 6 This is an experimental imaging diagram of Example 2 of a variable focus liquid crystal lens assembly proposed by the present invention. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0029] Example 1

[0030] Reference Figure 1-5 , a variable focus liquid crystal lens assembly, comprising a common lens, an adjustable liquid crystal wave plate and two liquid crystal polarization lenses;

[0031] The liquid crystal wave plate and the liquid crystal polarization lens are externally connected to an electrode group, the electrode group includes a first electrode layer and a second electrode layer, the first electrode layer and the second electrode layer are arranged between the adjustable liquid crystal wave plate and the liquid crystal polarization lens, and the electrode group is regulated by an external electric field;

[0032] The liquid crystal wave plate is used to adjust the rotation direction of the circular polarization state of the incident light, and the ordinary lens is a positive lens, which is used to maintain that all focal lengths of the zoom lens group are positive focal lengths;

[0033] The formula for the focal length of the three-light combination consisting of the ordinary lens and the liquid crystal polarizing lens is:

[0034] ψ=ψ0+ψ1+ψ2-d 01 ψ0(ψ1+ψ2)-d 12 ψ2(ψ0+ψ1)+d 01 d12 ψ0ψ1ψ2

[0035] Among them, ψ0, ψ1 and ψ2 are the optical powers of the three light groups, d 01 and d 12 are the spatial intervals between the three light groups respectively; the focal length of the lens group is calculated by this formula.

[0036] As a technical optimization solution of the present invention, the range of the parameters is limited as follows: 100mm<f<200mm, 5mm<d<10mm, where f is the focal length and d is the spatial interval between each light group.

[0037] As a technical optimization solution of the present invention, the liquid crystal polarization lens is prepared by using a Mach-Zehnder interference optical path. After the ultraviolet laser passes through a pinhole filter, it is collimated by a collimating lens and then divided into a beam of S light and a beam of P light by a polarization splitter prism. The S light is a linear polarized light parallel to the incident plane, and the P light is a linear polarized light perpendicular to the incident plane.

[0038] As a technical optimization solution of the present invention, the S light and the P light are respectively reflected by a reflector and arrive at the same polarization beam splitter prism, thereby realizing the superposition of the two beams of light.

[0039] As a technical optimization solution of the present invention, a lens is placed on the S optical path to transform the plane wave into a spherical wave.

[0040] As a technical optimization solution of the present invention, the liquid crystal polarization lens includes a first liquid crystal polarization lens and a second liquid crystal polarization lens, and the relationship between the focal length and the wavelength of the liquid crystal polarization lens is:

[0041] Among them, F is the focal length used, λ is the wavelength used, λ0 is the exposure wavelength, and Z0 is the propagation distance of the spherical wave from the rear focus of the ordinary lens.

[0042] As a technical optimization solution of the present invention, the focal length of the liquid crystal polarization lens can be controlled by controlling the exposure position Z0.

[0043] As a technical optimization solution of the present invention, a λ / 2 wave plate is placed before the first polarization beam splitter prism to adjust the linear polarization direction of the laser and indirectly adjust the splitting ratio of the two beams of light; a λ / 4 wave plate is placed before the next polarization beam splitter prism to convert the two orthogonal linear polarized lights into two orthogonal circular polarized lights.

[0044] When preparing the liquid crystal polarization lens: place an empty liquid crystal box made of a glass substrate with a light-controlled orientation film (ROP) spin-coated on an ITO substrate in a light field for exposure, and the spatial polarization distribution can be "recorded" in the orientation film. The exposure time is 8 minutes, and the thickness of the liquid crystal box is 5um. After the exposure, the empty liquid crystal box is placed on a heating platform at 120°C, and a nematic phase liquid crystal is injected, whose birefringence Δn = 0.165 (589nm, 20°C), and the preparation of the liquid crystal polarization lens is completed;

[0045] Then set the focal length of the ordinary lens L0 to 100mm. Under the 633mm wavelength light source, the focal lengths and f1 and f2 of the two liquid crystal polarization lenses L1 and L2 are 143mm and 196mm respectively, the effective aperture is 18mm, and the distance d between the lenses is 01 =9.5mm,d 12 =8mm, the camera is placed on the back focal plane of the imaging lens L1. lc The function of the wave plate is to change the polarization state of light. It can be placed in front of the liquid crystal polarization lens. For easy operation, the liquid crystal wave plate is placed at the front of the system.

[0046] The two liquid crystal polarization lenses and the liquid crystal wave plate are connected to external voltages, and the zoom function of the system is completely controlled by three groups of electrical signals from the electrode group. By utilizing the characteristics of liquid crystal molecules being modulated by electric fields, the liquid crystal polarization lens is controlled by voltage to switch between focal length and F, or the liquid crystal wave plate is controlled to switch the incident light between left-handed circular polarization and right-handed circular polarization, thereby achieving the purpose of zooming.

[0047] Example 2

[0048] In order to verify the liquid crystal polarization zoom lens group described in the above-mentioned embodiment 1, an imaging system was built, using right-handed circularly polarized light with a wavelength of 633nm. The imaging target was a transmissive resolution plate. The light was emitted from the resolution plate and became parallel light through the liquid crystal polarization zoom lens group. After propagating for a distance, it passed through an imaging lens L I (f I =40mm), converges to the camera (the camera is located at the imaging lens L I At the back focal length of the resolution board, the camera will capture a clear image of the resolution board.

[0049] Apply electrical signals of different focal lengths through the electrode group, and move the resolution board back and forth continuously to find a clear imaging position. Figure 6 (a) to (g) in the figure, the position is at the front focal length of the liquid crystal polarization zoom lens group;

[0050] Figure 6(a) to (g) are arranged from right to left according to the imaging position of the resolution plate, and their distances from the liquid crystal polarization lens L2 are 48.3mm, 59.4mm, 64.8mm, 83.8mm, 108.5mm, 145.3mm, and 237.5mm, respectively. Obviously, as the imaging position distance increases, it also means that the focal length of the liquid crystal polarization zoom lens group increases, the lateral magnification decreases, and the image becomes smaller and smaller.

[0051] It can be seen from the above that the liquid crystal polarization zoom lens group realizes the function of multi-point zoom by electrically controlling different electrical signals, and has certain feasibility.

[0052] When in use: When preparing the liquid crystal polarization lens: place an empty liquid crystal box made of a glass substrate with a light-controlled orientation film (ROP) spin-coated on an ITO substrate in a light field for exposure, and this spatial polarization distribution can be "recorded" in the orientation film. The exposure time is 8 minutes, and the thickness of the liquid crystal box layer is 5um. After the exposure, place the empty liquid crystal box on a heating platform at 120°C, inject nematic liquid crystal, whose birefringence Δn = 0.165 (589nm, 20°C), and the preparation of the liquid crystal polarization lens is completed; then set the focal length of the ordinary lens L0 to 100mm, and under a 633mm wavelength light source, the focal lengths and f1 and f2 of the two liquid crystal polarization lenses L1 and L2 are 143mm and 196mm respectively, the effective aperture is 18mm, and the distance d between the lenses is 01 =9.5mm,d 12 =8mm, the camera is placed on the back focal plane of the imaging lens L1. Liquid crystal wave plate P lc The function of the system is to only change the polarization state of light. It only needs to be placed in front of the liquid crystal polarization lens. For the convenience of operation, the liquid crystal wave plate is placed at the front of the system. The two liquid crystal polarization lenses and the liquid crystal wave plate are connected to external voltages. The zoom function of the system is all controlled by 3 groups of electrical signals from the electrode group. By utilizing the characteristics of liquid crystal molecules modulated by electric fields, the liquid crystal polarization lens is controlled by voltage to switch between focal length and F, or the liquid crystal wave plate is controlled to switch the incident light between left-handed circular polarization and right-handed circular polarization to achieve the purpose of zooming.

[0053] In summary: the zoom liquid crystal lens assembly can realize the focal length switching of the liquid crystal polarization lens by controlling the polarization state of the incident light and the external voltage, and achieve the purpose of equal-interval zooming by optimizing the lens spacing and focal length. Combined with the liquid crystal polarization zoom lens group, a zoom effect in 7 positions is achieved.

[0054] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A variable focus liquid crystal lens assembly, It is characterized in that It includes an ordinary lens, an adjustable liquid crystal wave plate and two liquid crystal polarization lenses; The liquid crystal wave plate and the liquid crystal polarization lens are externally connected to an electrode group, the electrode group includes a first electrode layer and a second electrode layer, the first electrode layer and the second electrode layer are arranged between the adjustable liquid crystal wave plate and the liquid crystal polarization lens, and the electrode group is regulated by an external electric field; The liquid crystal wave plate is used to adjust the rotation direction of the circular polarization state of the incident light, and the ordinary lens is a positive lens, which is used to maintain that all focal lengths of the zoom lens group are positive focal lengths; The formula for the focal length of the three-light combination consisting of the ordinary lens and the liquid crystal polarizing lens is: ψ=ψ 0 +ψ 1 +ψ 2 -d 01 ψ 0 (ψ 1 +ψ 2 )-d 12 ψ 2 (ψ 0 +ψ 1 )+d 01 d 12 ψ 0 ψ 1 ψ 2 Among them, ψ 0 , 1 and ψ 2 are the focal lengths of the three optical groups, d 01 and d 12 are the spatial intervals between the three light groups respectively; the focal length of the lens group is calculated by this formula.

2. A variable focus liquid crystal lens assembly according to claim 1, It is characterized in that The range of the limited parameters is as follows: 100mm<f<200mm, 5mm<d<10mm, where f is the focal length and d is the spatial interval between each light group.

3. The variable focus liquid crystal lens assembly according to claim 1, It is characterized in that The liquid crystal polarization lens is prepared by using the Mach-Zehnder interference optical path. After the ultraviolet laser passes through the pinhole filter, it is collimated by the collimating lens and then divided into a beam of S light and a beam of P light by a polarization beam splitter prism, wherein the S light is linearly polarized light parallel to the incident plane, and the P light is linearly polarized light perpendicular to the incident plane.

4. The variable focus liquid crystal lens assembly according to claim 3, It is characterized in that The S light and the P light are respectively reflected by the reflector and arrive at the same polarization beam splitter prism, thereby realizing the superposition of the two beams of light.

5. The variable focus liquid crystal lens assembly according to claim 3, It is characterized in that A lens is placed on the S optical path to transform its plane wave into a spherical wave.

6. The variable focus liquid crystal lens assembly according to claim 1, It is characterized in that The liquid crystal polarization lens includes a first liquid crystal polarization lens and a second liquid crystal polarization lens. The relationship between the focal length and the wavelength of the liquid crystal polarization lens is: Among them, F is the focal length, λ is the wavelength, 0 is the exposure wavelength, Z 0 is the propagation distance of the spherical wave from the rear focus of an ordinary lens.

7. The variable focus liquid crystal lens assembly according to claim 6, It is characterized in that By controlling the exposure position Z 0 , the focal length of the liquid crystal polarization lens can be controlled.

8. The variable focus liquid crystal lens assembly according to claim 3, It is characterized in that A λ / 2 wave plate is placed before the first polarization beam splitter to adjust the linear polarization direction of the laser and indirectly adjust the splitting ratio of the two beams of light; a λ / 4 wave plate is placed before the next polarization beam splitter to convert the two orthogonal linear polarized beams into two orthogonal circular polarized beams.

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