Low voltage liquid crystal lens with variable focal length

• US 20110043717A1
• Filed: 04/20/2009
• Published: 02/24/2011
• Est. Priority Date: 04/24/2008
• Status: Active Grant

• Current Assignee: Hong Kong University of Science and Technology
• Original Assignee: Hong Kong University of Science and Technology
• Inventors: Kwok, Hoi Sing, Valyukh, Sergiy, Chigrinov, Vladimir Grigorievich
• Granted Patent: US 8,471,999 B2
• Time in Patent Office: Days
• US Class Current: 349/33
• CPC Class Codes: G02F 1/133305 Flexible substrates, e.g. plastics, organic film
• CPC Class Codes: G02F 1/133784 by rubbing
• CPC Class Codes: G02F 1/29 for the control of the position or the direction of light beams, i.e. deflection
• CPC Class Codes: G02F 1/291 Two-dimensional analogue deflection
• CPC Class Codes: G02F 1/294 Variable focal length devices

Abstract

Disclosed herein is a liquid crystal lens with a variable focal length. The gradient profile of the liquid crystals molecules that causes the gradient profile of the refractive index is achieved by inducing non-uniformly distributed anchoring energy and an external electric or magnetic field applied to the liquid crystal layer. Unlike existing electrically controlled liquid crystal lens, the external electric or magnetic field has a uniform spatial distribution within the liquid crystal layer. The focal length of the liquid crystal lens is controlled via the non-uniformly distributed anchoring energy and by varying the uniformly distributed electric or magnetic field.

Claims

1. A liquid crystal optical device having a variable focal length, comprising:

at least one liquid crystal layer residing between a first substrate and a second substrate; and

one or more alignment layers associated with respective ones of the first substrate and the second substrate, wherein the one or more alignment layers have an anchoring energy that is spatially non-uniform in a predetermined way.

2. The liquid crystal optical device according to claim 1, wherein the at least one liquid crystal layer, the first and the second substrates, and the alignment layer are transparent.

3. The liquid crystal optical device according to claim 1, wherein one of the first and the second substrates has a reflective surface facing the at least one liquid crystal layer.

4. The liquid crystal optical device according to claim 1, wherein at least one of the first and the second substrates is a flexible substrate or a glass substrate.

5. The liquid crystal optical device according to claim 1, wherein at least one of the first and second substrates has an electrode pattern thereon.

6. The liquid crystal optical device according to claim 1, wherein the one or more alignment layers include a material with a photo-induced alignment property, and the spatially non-uniform distribution of anchoring energy is induced by at least one of a non-uniform illumination, a non-uniform polarization, and a non-uniform thickness of the alignment layer.

7. The liquid crystal optical device according to claim 1, wherein the spatially non-uniform distribution of anchoring energy is induced by a non-uniform rubbing applied to the alignment layer.

8. The liquid crystal optical device according to claim 1, wherein the alignment layer comprises multiple distinct materials and the non-uniform spatial distribution of the anchoring energy is induced by spatially varying the concentrations of the multiple distinct materials.

9. The liquid crystal optical device according to claim 1, wherein the non-uniform distribution of the anchoring energy of the alignment layer is induced by an ink-jet printing process, wherein a size of a droplet is a continuously varied corresponding to a change of a thickness of the one or more alignment layers.

10. The liquid crystal optical device according to claim 1, wherein at least one of the first and the second substrates has a flat surface.

11. The liquid crystal optical device according to claim 1, wherein at least one of the first and the second substrates has a curved surface.

12. The liquid crystal optical device according to claim 4, wherein a spatially uniform voltage is applied through the electrode pattern across a thickness of the at least one liquid crystal layer for controlling the variable focal length.

13. The liquid crystal optical device according to claim 4, wherein a spatially variable voltage is applied through the electrode pattern across a thickness of the at least one liquid crystal layer for controlling the variable focal length.

14. The liquid crystal optical device according to claim 1, wherein a spatially uniform magnetic field is applied through the electrode pattern across a thickness of the at least one liquid crystal layer for controlling the variable focal length.

15. The liquid crystal optical device according to claim 1, wherein a spatially variable magnetic field is applied through the electrode pattern across a thickness of the at least one liquid crystal layer for controlling the variable focal length.

16. A method for controlling a variable focal length of a liquid crystal optical device, comprising:

applying at least one of an electric field and a magnetic filed to a liquid crystal layer residing between a first substrate and a second substrate, wherein at least one of the first and the second substrate includes an alignment layer having anchoring energy with a non-uniform spatial distribution across the alignment layer; and

varying at least one of the voltage and the magnetic field to modify the variable focal length of the liquid crystal optical device.

17. The method of claim 16, wherein the at least one of the voltage and the magnetic field has a uniform spatial distribution across the liquid crystal layer.

18. The method of claim 16, wherein the non-uniform spatial distribution of the anchoring energy is induced by a non-uniform rubbing applied to the alignment layer.

19. The method of claim 16, wherein the alignment layer includes a material with a photo-induced alignment property, and the non-uniform spatial distribution of the anchoring energy is induced by at least one of a non-uniform illumination, a non-uniform polarization, a non-uniform transmission and a non-uniform thickness of the alignment layer.

20. The method of claim 19, wherein the non-uniform polarization includes exposing the alignment layer through photo-masks and the photo-masks comprise liquid crystal cells producing a controllable modification of a polarization of a transmitted light.

21. The method of claim 19, wherein the non-uniform illumination includes exposing the alignment layer through photo-masks and the photo-masks comprise liquid crystal cells producing a controllable transmission of light.

22. The method of claim 20, wherein at least one of a light pattern of the non-uniform polarization and an intensity is formed by utilizing a mask including a liquid crystal spatial light modulator.

23. The method of claim 20, wherein at least one of the non-uniform polarization and an intensity is controlled at each point sequentially by utilizing a polarization modulator and a scanned light beam.

24. The method of claim 20, further including forming the non-uniform spatial distribution of the anchoring energy by utilizing two or more sequential exposures through gray-level masks, wherein each of the two or more sequential exposures has at least one of a type, an orientation, a state of polarization, and an intensity.

25. The method of claim 16, wherein the alignment layer comprising two different materials and wherein the non-uniform spatial distribution of the anchoring energy is induced by spatially varying the concentrations of the at least two different materials.

26. The method of claim 25, wherein the concentrations of the at least two different materials are varied in accordance with at least a screen printing process and a diffusion process.