High-speed focal length switcher based on ferroelectric nematic liquid crystal

Abstract

The utility model discloses a high speed focal length switcher based on ferroelectric nematic phase liquid crystal, which comprises FLC half-wave plates, 1 / 4 wave plates and PB lenses, the FLC half-wave plates, the 1 / 4 wave plates, the PB lenses and the 1 / 4 wave plates are repeatedly arranged in a single level, transparent ultraviolet curing glue is adopted to paste all the elements in sequence, the FLC half-wave plates in each level are powered up and adjusted, and the focal length of the PB lenses is adjusted. And the left-handed and right-handed circular polarization switching effect of each level is realized, so that the convergence or divergence selection requirement of the final emergent level is met, and the switching function of multiple different focal lengths is realized. According to the utility model, a plurality of PB lenses with different focal lengths are integrated, and the adjustable phase half-wave plate is combined, so that the switching function of the plurality of focal lengths is realized; a ferroelectric nematic phase liquid crystal material is adopted in the phase-adjustable half-wave plate, so that the response time of the device is greatly shortened to be within 1ms, and the device has the characteristic of ultra-fast response; the device is high in integration level, small in size and weight, low in processing and driving cost, and suitable for a scene with a small space.

Description

Technical Field

[0001] The utility model relates to a high-speed light beam scanner, and particularly to a high-speed focal length switch based on ferroelectric nematic liquid crystal. Background Art

[0002] The existing focal length switching is mainly mechanical, such as the lens group in a single-lens reflex camera or a telescope. The relative position between the lenses can be changed by rotating the focusing ring, so as to realize the focal length switching of the lens group. This scheme has low precision, large volume and large weight, and the performance will be greatly restricted because the influence of inertia needs to be overcome during the movement. The new focal length switching technology mainly relies on the liquid crystal electro-control variable focal length lens group. The first one is to apply a non-uniform electric field on a uniform liquid crystal layer, and use a structured ITO electrode to apply a gradient electric field to the liquid crystal layer, so that the inclination angles of liquid crystal molecules at different positions gradually change, forming a gradient phase modulation on the incident light. This scheme also has certain disadvantages. The processing precision requirement and cost of ITO are relatively high, and the increase of the liquid crystal thickness may lead to the edge field effect, and the performance will be significantly reduced when the lens diameter exceeds 30 mm. At the same time, the response speeds of the existing schemes are all relatively slow, and it is difficult to meet the requirements of new application scenarios such as AR multi-plane display. Summary of the Utility Model

[0003] Purpose of the utility model: The purpose of the utility model is to provide a high-speed focal length switch based on ferroelectric nematic liquid crystal.

[0004] Technical solution: The device of the utility model includes an FLC half-wave plate, a quarter-wave plate and a PB lens, which are repeatedly arranged in a single level in the order of FLC half-wave plate - quarter-wave plate - PB lens - quarter-wave plate. Each component is pasted in sequence by using a transparent ultraviolet curing glue. By applying electricity to the FLC half-wave plate of each level for adjustment, the left and right circular polarization switching effects of each level are realized, so as to meet the requirements of the convergence or divergence selection of the final output level, and the switching function of multiple different focal lengths is realized.

[0005] Further, a pair of wires of the FLC half-wave plate are respectively connected to the ITO conductive surfaces of two glass substrates, and the magnitude of the electric field between the two glasses is controlled by outputting an alternating square wave signal with a specific frequency by a voltage controller.

[0006] Further, the initial slow axis direction of the FLC half-wave plate is at the angular bisector of the slow axis direction of the quarter-wave plate and the horizontal direction.

[0007] Further, the FLC half-wave plate is realized by using a liquid crystal cell with antiparallel orientation and injecting a ferroelectric nematic liquid crystal material FD4004N into it.

[0008] Further, the quarter-wave plate is a liquid crystal polymer film with a homogeneous orientation, a slow axis direction of 45°, and the retardation corresponding to the thickness needs to satisfy 1 / 4 of the designed wavelength.

[0009] Further, the PB lens has a radially-gradual orientation, with a smaller period towards the outside. The period size is determined by the designed wavelength and the focal length, and the thickness satisfies 1 / 2 of the designed wavelength.

[0010] Further, a single stage of the PB lens realizes the switching between a pair of converging and diverging.

[0011] Beneficial effects: Compared with the prior art, the present utility model has the following advantages: The present utility model integrates multiple PB lenses with different focal lengths and combines an adjustable-phase half-wave plate to realize the switching function of multiple focal lengths; ferroelectric nematic liquid crystal material is adopted in the adjustable-phase half-wave plate, greatly shortening the response time of the device to within 1 ms, and having the characteristic of ultra-fast response; high integration, small volume and weight, low processing and driving costs, and being suitable for scenarios with small space. Description of the Drawings

[0012] Figure 1 is a structural schematic diagram of the present utility model;

[0013] Figure 2 is a schematic diagram of the slow axis of the FLC half-wave plate. Detailed Embodiments

[0014] The technical solutions of the present utility model will be further described below with reference to the drawings.

[0015] As Figure 1 shown, taking a high-speed focal length switch of second-order ferroelectric nematic liquid crystal as an example, its basic structure is "FLC half-wave plate - quarter-wave plate - PB lens - quarter-wave plate - FLC half-wave plate - quarter-wave plate - PB lens". For each additional stage of cascading, one more layer of the structure "quarter-wave plate - FLC half-wave plate - quarter-wave plate - PB lens" is added, and the QWP is the quarter-wave plate.

[0016] The FLC half-wave plate is realized by using a liquid crystal cell with antiparallel orientation and injecting a ferroelectric nematic liquid crystal material FD4004N (DIC) into it. Each stage of the FLC half-wave plate has a pair of wires respectively connected to the ITO conductive surfaces of two glass substrates, and the magnitude of the electric field between the two glasses can be controlled by outputting an AC square wave signal with a specific frequency through a voltage controller. The 1 / 4 wave plate and the PB lens are both thin films made of liquid crystal polymer materials, which can be peeled off and reserved after being prepared on a glass substrate. The orientation of the QWP is a uniform orientation, the slow axis direction is 45°, and the retardation corresponding to the thickness needs to meet 1 / 4 of the designed wavelength. The orientation of the PB lens is gradually changing along a radial direction, and the period becomes smaller towards the outside. The period size is determined by the designed wavelength and the focal length, and the thickness meets the half-wave condition of the designed wavelength. Schematic diagram of the PB lens module, the black solid line and the dotted line respectively represent left-handed and right-handed circularly polarized light, one shows a converging effect and the other shows a diverging effect.

[0017] As Figure 2 shown, the schematic diagram of the slow axis of the FLC half-wave plate. The red color is the initial state, and the black solid line and the dotted line are the slow axis directions of the liquid crystal molecules when positive and negative voltages are applied respectively.

[0018] Each PB lens prepared in this way only corresponds to a fixed focal length. We design and prepare multiple PB lenses with different focal lengths, and realize the switching of multiple focal lengths by cascading PB lenses, phase half-wave plates and wave plates. After the PB lens, 1 / 4 wave plate and FLC half-wave plate are prepared, each component is pasted together in sequence with a transparent ultraviolet curing glue, and attention should be paid to keeping the relative angles between the components consistent with the design. The slow axis direction of the 1 / 4 wave plate forms a 45° angle with the horizontal direction, and the initial slow axis direction of the FLC is on the angular bisector of the slow axis direction of the 1 / 4 wave plate and the horizontal direction.

[0019] When the device is in use, by applying or not applying voltage to the FLC phase retarder at each level, the switching effect of left-handed and right-handed circular polarization at each level can be realized, so as to meet the selection requirements of final outgoing convergence / divergence, and the switching function of multiple different focal lengths can be realized. Each layer of PB lens structure can realize the switching of a pair of convergence / divergence. Therefore, n layers of PB lens structures with different focal lengths can realize 2n focal length switches. For example, if it is necessary to converge the incident light beam to the state with the smallest focal length, the incident polarization state of each FLC half-wave plate is adjusted to left-handed circular polarization. If it is necessary to diverge the incident light beam to the state with the largest divergence angle, the incident polarization state of each FLC half-wave plate is adjusted to right-handed circular polarization. Through the power-on adjustment of each layer of FLC half-wave plate, the switching function of all focal lengths is realized. Taking a 2-layer device as an example, there are a total of 4 focal lengths with ±2 levels, and the single-switching combined switching speed can be less than 1 ms.

Claims

1. A high-speed focal length switch based on ferroelectric nematic liquid crystal, characterized in that: It includes an FLC half-wave plate, a quarter-wave plate, and a PB lens. The arrangement of FLC half-wave plate - quarter-wave plate - PB lens - quarter-wave plate is repeated for each single stage. Transparent ultraviolet curable glue is used to paste each component in sequence. By applying an electric current to the FLC half-wave plate of each stage for adjustment, the switching effect of left-handed and right-handed circular polarization for each stage is achieved, thus meeting the requirements of convergence or divergence selection for the final output stage and realizing the switching function of multiple different focal lengths.

2. The high-speed focal length switch based on ferroelectric nematic liquid crystal according to claim 1, wherein: The FLC half-wave plate has a pair of wires respectively connected to the ITO conductive surfaces of two glass substrates, and the magnitude of the electric field between the two glasses is controlled by outputting an alternating square wave signal with a specific frequency through a voltage controller.

3. The high-speed focal length switch based on ferroelectric nematic liquid crystal according to claim 1, wherein: The initial slow axis direction of the FLC half-wave plate is on the angular bisector of the slow axis direction of the quarter-wave plate and the horizontal direction.

4. The high-speed focal length switch based on ferroelectric nematic liquid crystal according to claim 1, characterized in that: The FLC half-wave plate is realized by using a liquid crystal cell with anti-parallel orientation and injecting a ferroelectric nematic liquid crystal material FD4004N into it.

5. The high-speed focal length switch based on ferroelectric nematic liquid crystal according to claim 1, characterized in that: The quarter-wave plate is a liquid crystal polymer film with a homogeneous orientation, the slow axis direction is 45°, and the retardation corresponding to the thickness needs to meet 1 / 4 of the designed wavelength.

6. The high-speed focal length switch based on ferroelectric nematic liquid crystal according to claim 1, characterized in that: The PB lens has a radial gradient orientation, the period becomes smaller towards the outside, and the period size is determined by the designed wavelength and the focal length, and the thickness meets 1 / 2 of the designed wavelength.

7. The high-speed focal length switch based on ferroelectric nematic liquid crystal according to claim 1, wherein: Each single stage of the PB lens realizes the switching between a pair of convergence or divergence.

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