Diffractive optical elements with graded edges

• US 9,910,276 B2
• Filed: 06/30/2015
• Issued: 03/06/2018
• Est. Priority Date: 06/30/2015
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Vallius, Tuomas, Sainiemi, Lauri, Levola, Tapani, Mattila, Marco
• Primary Examiner(s): Pichler, Marin
• Application Number:
  US14/788,174
• Publication Number:
  US 20170003504A1
• Time in Patent Office: 980 Days
• Field of Search: 359567, 359569
• CPC Class Codes: G02B 2027/0125 Field-of-view increase by wavefront division
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/0081 with means for altering, e.g. enlarging, the entrance or exit pupil
• 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 27/4205 having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 5/1819 Plural gratings positioned on the same surface, e.g. array of gratings plural diffractive elements positioned sequentially along the optical path G02B27/4272
• CPC Class Codes: G02B 5/1852 using mechanical means, e.g. ruling with diamond tool, moulding

Abstract

In an optical system that includes a waveguide with multiple diffractive optical elements (DOEs) incorporating diffraction gratings, light exiting a trailing edge of an upstream DOE enters a leading edge of a downstream DOE. One or more of the DOEs may include a leading and/or a trailing edge that have a graded profile. At a graded trailing edge of an upstream DOE, grating height smoothly decreases from full height to shallow height as a function of the proximity to the trailing edge. At a graded leading edge of the downstream DOE grating height smoothly increases from shallow height to full height as a function of distance away from the leading edge. By reducing a sharp boundary at the interface between the upstream and downstream DOEs, the graded profiles of the DOE edges enable optical resolution to be maintained decreasing sensitivity to misalignment between the DOEs that may occur during manufacturing.

Claims

1. An optical system, comprising:

a substrate of optical material configured as a waveguide;

a first diffractive optical element (DOE) disposed on the waveguide and configured as an in-coupling grating to receive, as an input, one or more optical beams that propagate in the first DOE and exit at a trailing edge of the first DOE; and

a second DOE disposed on the waveguide and configured for pupil expansion of the one or more optical beams along a first direction,

in which the trailing edge of the first DOE is located on the waveguide at an interface with a leading edge of the second DOE, wherein the one or more optical beams exiting at the trailing edge, enter at the leading edge of the second DOE, and

wherein the trailing edge and leading edge are graded so that a grating height of each of the first DOE and the second DOE increases as a function of distance from the interface, and wherein the grating height increases linearly as a function from the distance from the interface so that profiles of the graded leading and trailing edges are wedge-shaped.

2. The optical system of claim 1 further including a third DOE disposed on the waveguide and configured for pupil expansion of the optical beams along a second direction, and further configured as an out-coupling grating to couple, as an output from the waveguide, one or more optical beams with expanded pupil relative to the input.

3. The optical system of claim 1 in which the grating height in the first DOE decreases approximately linearly from a full height upstream from the trailing edge to a shallow height at the trailing edge of the first DOE.

4. The optical system of claim 1 in which the grating height in the first DOE decreases approximately linearly from a full height upstream from the trailing edge to zero height at the trailing edge of the first DOE.

5. The optical system of claim 1 in which the grating height in the second DOE increases approximately linearly from a shallow height at the leading edge to a full height downstream from the leading edge.

6. The optical system of claim 1 in which either the first DOE or second DOE is a straight diffraction grating or a slanted diffraction grating.

7. The optical system of claim 1 in which the one or more optical beams received as the input emanate as a virtual image produced by a micro-display or imager.

8. The optical system of claim 1, wherein ends opposite the trailing edge and leading edge of the first and second DOEs, respectively, have gratings of a greater height than at the respective trailing and leading edges.