EP-4735926-A1 - ADJUSTABLE OPTICAL ELEMENT

Abstract

An optical element (100) comprises a substrate (110) and a conductive portion (120) configured to, upon application of an electrical current therethrough, generate heat through joule heating. The substrate is configured to receive heat generated in the conductive portion and, in response, undergo thermal expansion so as to change the curvature of a surface of the optical element. A method of changing the curvature of an optical element is also provided. The method comprises generating heat within the optical element so as to cause thermal expansion within the optical element.

Inventors

• ZERULLA, Dominic Karsten
• O'TOOLE, Silas Dan

Assignees

• University College Dublin, National University of Ireland

Dates

Publication Date

20260506

Application Date

20240628

Claims (19)

1. 1. An optical element comprising: a substrate; and a conductive portion configured to, upon application of an electrical current therethrough, generate heat through joule heating; wherein the substrate is configured to receive heat generated in the conductive portion and, in response, undergo thermal expansion so as to change the curvature of a surface of the optical element.
2. 2. The optical element of claim 1, wherein the conductance throughout the conductive portion is non-uniform.
3. 3. The optical element of claim 1 or claim 2, wherein the change in curvature of the optical element modifies the focal length of the optical element.
4. 4. The optical element of any preceding claim, wherein the thickness of the conductive portion is non-uniform.
5. 5. The optical element of any preceding claim, wherein the conductive portion comprises a plurality of dopants.
6. 6. The optical element of claim 5, wherein the distribution of dopants throughout the conductive portion is non-uniform.
7. 7. The optical element of any preceding claim, wherein the conductive portion comprises a plurality of conductive elements.
8. 8. The optical element of claim 7, wherein the conductance of each conductive element is non-uniform.
9. 9. The optical element of claim 7 or claim 8, wherein the distribution of conductive elements throughout the conductive portion is non-uniform.
10. 10. The optical element of any of claims 7-9, wherein the conductive elements are individually operable.
11. 11. The optical element of any preceding claim, wherein the conductive portion is, or comprises, a coating applied to the substrate.
12. 12. The optical element of any preceding claim, wherein the conductive portion is, or comprises, a portion of the substrate.
13. 13. The optical element of claim 12, wherein the conductive portion is, or comprises, a surface of the substrate.
14. 14. The optical element of any of claims 3-13, wherein the optical element comprises two conductive portions, each conductive portion being associated a different surface of the optical element; and wherein the conductance throughout each conductive portion is distributed such that, upon application of an electrical current through one conductive portion, joule heating causes thermal expansion of the substrate so as to modify the curvature of the surface associated with that conductive portion.
15. 15. The optical element of any preceding claim, wherein the optical element is a lens.
16. 16. The optical element of any of claims 1-14, wherein the optical element is a mirror.
17. 17. A method of changing the curvature of an optical element, the method comprising: generating heat within the optical element so as to cause thermal expansion within the optical element.
18. 18. The method of claim 17, wherein the step of generating heat comprises applying a current to the optical element to generate heat through joule heating.
19. 19. The method of claim 17 or claim 18, wherein the optical element comprises a substrate and a conductive region, and wherein generating heat comprises generating heat in the conductive region.

Description

ADJUSTABLE OPTICAL ELEMENT This present invention relates to an optical element with an adjustable focal length. More particularly, the present invention relates an optical element with a focal length which is adjustable in response to the generation of heat through the application of an electrical current. Background In modern optics, there is an increasing demand for lenses with a wide range of focal lengths. Further, modern optical systems often require real-time fine adjustments to the focal length when in use. For example, zoom objective lenses, such as those used in digital cameras, comprise a plurality of lenses which form a complex system. Such lens systems typically utilize moving (sliding) lenses for zooming and focussing actions, which requires movement of substantial (heavy) lenses over macroscopic distances. There is a high level of energy input required to move the lenses, and the adjustments can be time consuming. Further, the space needed for a well corrected combination of lenses, as required for modern optical systems, is substantial. This means that systems have to be simplified if they are to be integrated into the space available in devices such as integrated cameras in smartphones, USB cameras, and other devices. Further, there is demand for fully aberration corrected lenses, which require non- spherical elements with a high-fidelity shape. These are difficult and expensive to produce. An optical element that addresses at least some of these issues is desired. Summary of Invention According to a first aspect of the invention, there is provided an optical element. The optical element comprises a substrate. The optical element comprises a conductive portion configured to, upon application of an electrical current therethrough, generate heat through joule heating. The substrate is configured to receive heat generated in the conductive portion and, in response, undergo thermal expansion so as to change the curvature of a surface of the optical element. Changing the curvature of the surface may modify the focal length of the optical element. Having an optical element with a focal length that is adjustable through the application of a current enables dynamic optical systems to be formed without requiring multiple moving lenses. This greatly simplifies the design of dynamic optical systems. Using thermal expansion to change the curvature, and therefore the focal length, of the optical element enables fine control of the focal length. A user can determine the required temperature change required to create a specific curvature, and so the focal length can be controlled with fine detail. Using joule heating to cause thermal expansion to change the focal length of the optical element ensures that the focal length can be adjusted rapidly. The focal length adjustment may take place on microsecond timescales. The focal length adjustment may take place on millisecond timescales. Using such rapid adjustments enables the optical element to be used in situations requiring rapid focal length adjustments. The conductance throughout the conductive portion may be non-uniform. The conductance throughout the conductive portion may be distributed such that, upon application of an electrical current through the conductive portion, joule heating causes thermal expansion of the substrate so as to modify the curvature of a surface of the substrate. Having a non-uniform conductive portion may ensure that the amount of heat transferred to the substrate varies across the substrate. Varying the amount of heat transferred into the substrate results in different amounts of local thermal expansion across the substrate, meaning specific curvatures and shapes can be created through the application of current through the conductive portion. The thickness of the conductive portion may be non-uniform. Having a conductive portion with non-uniform thickness causes the conductive portion to have non-uniform conductance. The conductive portion may comprise a plurality of dopants. The distribution of dopants throughout the conductive portion may be non-uniform. Dopants may increase the conductivity of the conductive region. Dopants may decrease the conductivity of the conductive region. Having a non-uniform distribution of dopants creates a non-uniform conductance throughout the conductive portion. The conductive portion may comprise a plurality of conductive elements. The conductance of each conductive element may be non-uniform. The distribution of conductive elements throughout the conductive portion may be non-uniform. The conductive elements may be conductive tracks or traces. The conductive elements may be individually operable. Having individually operable conductive elements enables generation of heat in specific areas, thus enabling the creation of arbitrary bespoke surface curvatures. The conductive portion may be, or comprise, a coating applied to the substrate. The conductive portion may be, or comprise, a portion