Diffraction Grating With a Spatially Varying Duty-Cycle

• US 20090128911A1
• Filed: 09/07/2006
• Published: 05/21/2009
• Est. Priority Date: 09/14/2005
• Status: Abandoned Application

• Current Assignee: Mirage Innovations Limited
• Original Assignee: Mirage Innovations Limited
• Inventors: Konforti, Naim, Itzkovitch, Moti, Neistein, Eyal
• Application Number:
  US11/991,492
• Publication Number:
  US 20090128911A1
• Time in Patent Office: Days
• US Class Current: 359/575
• CPC Class Codes: G02B 2027/011 comprising device for correcting geometrical aberrations, distortion
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 2027/0132 comprising binocular systems
• CPC Class Codes: G02B 2027/0174 holographic
• 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 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 5/1866 Transmission gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02B 6/0016 Grooves, prisms, gratings, scattering particles or rough surfaces
• CPC Class Codes: G02B 6/0038 Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide
• CPC Class Codes: G02B 6/2848 having refractive means, e.g. imaging elements between light guides as splitting, branching and/or combining devices, e.g. lenses, holograms

Abstract

A diffractive optical element is disclosed. The optical element comprises a grating having a periodic linear structure in at least one direction. The linear structure is characterized by non-uniform duty cycle selected to ensure non-uniform diffraction efficiency.

Claims

1. A diffractive optical element, comprising a grating having a periodic linear structure in at least one direction, said linear structure being characterized by non-uniform duty cycle selected such that said grating is described by non-uniform diffraction efficiency function;

wherein said non-uniform diffraction efficiency function is selected such that when a light ray impinges on said grating a plurality of times, a predetermined and substantially constant fraction of the energy of said light is diffracted at each impingement, and a light beam having a substantially uniform intensity profile for a predetermined range of wavelengths is provided.

2. An optical relay device, comprising a light transmissive substrate and a plurality of diffractive optical elements, wherein at least one diffractive optical element of said plurality of diffractive optical elements is the diffractive optical element of claim 1.

3. A system for providing an image to a user, comprising the optical relay device of claim 2, and an image generating system for providing said optical relay device with collimated light constituting said image.

5. The element of claim 1, wherein said linear structure is further characterized by non-uniform modulation depth selected in combination with said non-uniform duty cycle to provide said non-uniform diffraction efficiency function.

6. The element of claim 1, wherein said predetermined range of wavelengths extends from about 0.7λ

to about 1.3λ

, wherein λ

is a central value characterizing the said range.

7. The device of claim 2, wherein at least one grating of said plurality of diffractive optical elements is formed in said light transmissive substrate.

8. The device of claim 2, wherein at least one grating of said plurality of diffractive optical elements is attached to said light transmissive substrate.

9. The device of claim 2, wherein said plurality of diffractive optical elements comprises an input diffractive optical element, a first output diffractive optical element and a second output diffractive optical element.

10. The device of claim 9, wherein said input diffractive optical element is designed and constructed for diffracting light striking the device at a plurality of angles within a predetermined field-of-view into said substrate, such that light corresponding to a first partial field-of-view propagates via total internal reflection to impinge on said first output diffractive optical element, and light corresponding to a second partial field-of-view propagates via total internal reflection to impinge on said second output diffractive optical element, said first partial field-of-view being different from said second partial field-of-view.

11. The system of claim 3, wherein said image generating system comprises a light source, at least one image carrier and a collimator for collimating light produced by said light source and reflected or transmitted through said at least one image carrier.

12. The system of claim 3, wherein said image generating system comprises at least one miniature display and a collimator for collimating light produced by said at least one miniature display.

13. The system of claim 3, wherein said image generating system comprises a light source, configured to produce light modulated imagery data, and a scanning device for scanning said light modulated imagery data onto the optical relay device.

4. A method of diffracting light, comprising entrapping the light to propagate through a light transmissive substrate via total internal reflection, and using a diffractive optical element for diffracting the light out of said light transmissive substrate,

wherein said diffractive optical element comprises a grating having a periodic linear structure in at least one direction, said linear structure being characterized by non-uniform duty cycle selected such that said grating is described by non-uniform diffraction efficiency function;

wherein said non-uniform diffraction efficiency function is selected such that when a light ray impinges on said grating a plurality of times, a predetermined and substantially constant fraction of the energy of said light is diffracted at each impingement, and a light beam having a substantially uniform intensity profile for a predetermined range of wavelengths is provided.