OPTICAL ELEMENT WITH A FRESNEL STRUCTURE, AND DISPLAY DEVICE WITH SUCH AN OPTICAL ELEMENT

• US 20160349512A1
• Filed: 07/25/2014
• Published: 12/01/2016
• Est. Priority Date: 07/26/2013
• Status: Active Grant

• Current Assignee: Tooz Technologies GmbH
• Original Assignee: Carl Zeiss AG (Carl-Zeiss-Stiftung)
• Inventors: MENKE, Christoph, SCHMIDT, Eduard, SINGER, Wolfgang, KERWIEN, Norbert
• Granted Patent: US 11,204,498 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0012 Optical design, e.g. procedures, algorithms, optimisation routines
• CPC Class Codes: G02B 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 3/08 with discontinuous faces, e.g. Fresnel lens diffractive Fresnel lenses G02B5/1876
• CPC Class Codes: G02B 5/09 Multifaceted or polygonal mirrors , e.g. polygonal scanning mirrors; Fresnel mirrors

Abstract

Provided is an optical element with a Fresnel structure with several Fresnel segments. Each Fresnel segment has an optically active facet, the shape of which is part of a predetermined surface. The predetermined surfaces of the optically active facets differ in terms of their curvature profile.

Claims

1. An optical element, comprising:

a Fresnel structure including several Fresnel segments, wherein each Fresnel segment has an optically active facet, wherein the shape of the optically active facet is part of a predetermined surface, and wherein each of the predetermined surfaces of the optically active facets of each of the several Fresnel segments has a different curvature profile.

2. The optical element according to claim 1, wherein, because of the different curvature profiles of the predetermined surfaces, the optically active facets cannot be assembled to form a continuously differentiable surface.

3. The optical element according to claim 1, wherein the predetermined surfaces have no mirror or rotational symmetry.

4. The optical element according to claim 1, wherein the predetermined surfaces have no translational symmetry.

5. The optical element according to claim 1, wherein the Fresnel structure is formed on a boundary surface of the optical element.

6. The optical element according to claim 5, wherein the boundary surface is curved.

7. The optical element according to claim 1, wherein the Fresnel segments neighbour each other directly.

8. The optical element according to claim 1, wherein the Fresnel segments are spaced apart from each other.

9. The optical element according to claim 1, wherein the Fresnel structure provides an optical imaging function.

10. The optical element according to claim 1, wherein the optically active facets are arranged next to each other along a first direction and extend in the form of strips transverse to the first direction.

11. The optical element according to claim 1, wherein the optically active facets are arranged next to each other along a first direction and along a second direction running transverse to the first direction.

12. The optical element according to claim 1, wherein the optically active facets are formed as reflective facets.

13. The optical element according to claim 1,

wherein the Fresnel structure is formed as a reflective Fresnel structure configured to deflect light bundles incident on the Fresnel structure along a direction of incidence into a direction of emergence,

wherein the optically active facets are formed reflective and are arranged next to each other, and at least two directly neighbouring facets include a first reflective section and an adjoining second reflective section,

wherein the reflectivity of the first reflective section is greater than the reflectivity of the second reflective section, and

wherein, viewed in the direction of incidence, the second reflective section of a first reflective facet lies in front of the first reflective section of the directly neighbouring reflective facet, with the result that the part of the incident light bundle that is transmitted by the second reflective section of the first reflective facet strikes the first reflective section of the directly neighbouring reflective facet, in order to be deflected.

14. The optical element according to claim 13, in which the second reflective section of the reflective facets includes in each case a first area which adjoins the first reflective section and a second area which adjoins the first area, wherein the second area of the first facet, viewed in the direction of incidence, lies in front of the first area of the directly neighbouring facet.

15. The optical element according to claim 14, in which the reflectivity of the first area is greater than the reflectivity of the second area.

16. A display device comprising:

an optical element according to claim 1,

a holder that can be fitted on the head of a user,

an image-generating module which generates an image and is secured to the holder, and

an imaging optical system which is secured to the holder and which has the optical element and images the generated image, when the holder is fitted on the head, such that the user can perceive it as a virtual image,

wherein the image generated by the image-generating module is coupled into the optical element via a coupling-in section of the optical element, guided in the optical element, by one or more reflections, to a coupling-out section and coupled out of the optical element via the coupling-out section, wherein at least one of the coupling-in and coupling-out section includes the Fresnel structure.

17. A method for producing an optical element according to claim 1, the method comprising:

a) providing an individual surface description for each optically active facet;

b) optimizing the shape of the surface characterized by the surface description for each optically active facet, in order to determine the predetermined surface;

c) generating the production data on the basis of the thus-determined predetermined surfaces; and

d) producing the optical element on the basis of the production data.

18. The method according to claim 17, wherein in step c), for each facet, the part of the determined predetermined surface which characterizes the optically active facet is arranged computationally on a curved base surface.