Attenuation of Narcissus effect in pancake lens assembly

Patent metadata

Field	Value
Publication number	US-10691198-B1
Application number	US-201715712003-A
Country	US
Kind code	B1
Filing date	Sep 21, 2017
Priority date	Sep 21, 2017
Publication date	Jun 23, 2020
Grant date	Jun 23, 2020

Abstract

A pancake lens assembly includes a back optical element, a front optical element and an absorptive linear polarizer. The back optical element transmits a defined amount of light incident on a surface of the back optical element and reflects a remaining amount of the light incident on the surface of the back optical element. The front optical element is in optical series with the back optical element and positioned closer to an eye-box than the back optical element. The front optical element is configured to transmit toward the eye-box light received from the back optical element having a polarization parallel to a transmission axis of the front optical element. The absorptive linear polarizer is positioned between the front optical element and the eye-box. A transmission axis of the absorptive linear polarizer is oriented parallel to the polarization of the light being transmitted by the front optical element.

First claim

What is claimed is:

1. A lens assembly comprising:
a back optical element configured to:
transmit a defined amount of light incident on a surface of the back optical element, and
reflect a remaining amount of the light incident on the surface of the back optical element;

a front optical element in optical series with the back optical element and positioned closer to an eye-box than the back optical element, the front optical element configured to transmit toward the eye-box without changing an optical power, light received from the back optical element having a polarization parallel to a transmission axis of the front optical element; and
an absorptive linear polarizer directly adjacent to the front optical element and positioned between the front optical element and the eye-box, wherein a transmission axis of the absorptive linear polarizer is oriented parallel to the polarization of the light being transmitted by the front optical element.

2. The lens assembly of claim 1 , further comprising:
a waveplate positioned between the front optical element and the back optical element, the waveplate configured to:
in-couple polarized light, and
generate output light having different polarization than the in-coupled polarized light.

3. The lens assembly of claim 2 , wherein the waveplate comprises a quarter waveplate configured to generate the output light of circular polarization using the in-coupled light having linear polarization.

4. The lens assembly of claim 2 , wherein the waveplate comprises a quarter waveplate configured to generate the output light of linear polarization using the in-coupled light having circular polarization.

5. The lens assembly of claim 1 , wherein the back optical element is configured to:
transmit approximately 50% of the light incident on the surface of the back optical element; and
reflect approximately 50% of the light incident on the surface of the back optical element.

6. The lens assembly of claim 1 , wherein the front optical element is configured to transmit a first portion of light reflected from at least one surface of an eye in the eye-box having a first polarization parallel to the transmission axis of the front optical element.

7. The lens assembly of claim 6 , wherein the absorptive linear polarizer is configured to absorb a second portion of the reflected light having a second polarization perpendicular to the transmission axis of the front optical element.

8. The lens assembly of claim 1 , wherein the absorptive linear polarizer is laminated on a surface of the front optical element and configured to absorb a portion of light reflected from at least one surface of an eye in the eye-box having a polarization perpendicular to the transmission axis of the front optical element.

9. The lens assembly of claim 1 , further comprising a waveplate positioned between the absorptive linear polarizer and the eye-box configured to change polarization of light incident on a surface of the waveplate.

10. The lens assembly of claim 9 , wherein:
the waveplate comprises a quarter waveplate; and
the quarter wave plate polarizer and the absorptive linear polarizer mitigate reflections of light from at least one surface of an eye in the eye-box polarized in a direction of the light being transmitted by the front optical element.

11. The lens assembly of claim 1 , wherein the lens assembly is a component of a head-mounted display (HMD).

12. The lens assembly of claim 11 , wherein:
the back optical element is adjacent to an electronic display of the HMD;
the electronic display emits image light incident on the surface of the back optical element.

13. The lens assembly of claim 12 , further comprising:
a linear polarizer coupled to the electronic display that generates linearly polarized image light using the image light emitted from the electronic display; and
a quarter waveplate positioned between the linear polarizer and the back optical element that generates circularly polarized image light using the linearly polarized image light.

14. A head-mounted display (HMD) comprising:
an electronic display configured to emit image light;
a back optical element adjacent to the electronic display configured to transmit at least a portion of the image light;
a front optical element in optical series with the back optical element and positioned closer to an eye-box of the HMD corresponding to a location of a user's eye, the front optical element configured to transmit toward the eye-box without changing an optical power, at least the portion of the image light received from the back optical element having a polarization parallel to a transmission axis of the front optical element; and
an absorptive linear polarizer directly adjacent to the front optical element and positioned between the front optical element and the eye-box, wherein a transmission axis of the absorptive linear polarizer is oriented parallel to the polarization of at least the portion of the image light being transmitted by the front optical element.

15. The HMD of claim 14 , wherein the back optical element is configured to:
transmit approximately 50% of light incident on a surface of the back optical element; and
reflect approximately 50% of the light incident on the surface of the back optical element.

16. The HMD of claim 14 , wherein the front optical element is configured to transmit a first portion of light reflected from at least one surface of the user's eye having a first polarization parallel to the transmission axis of the front optical element.

17. The HMD of claim 16 , wherein the absorptive linear polarizer is configured to absorb a second portion of the reflected light having a second polarization perpendicular to the transmission axis of the front optical element.

18. The HMD of claim 14 , wherein the absorptive linear polarizer is laminated on a surface of the front optical element and configured to absorb a portion of light reflected from at least one surface of the user's eye having a polarization perpendicular to the transmission axis of the front optical element.

19. The HMD of claim 14 , further comprising a waveplate positioned between the absorptive linear polarizer and the eye-box configured to change polarization of light incident on a surface of the waveplate.

20. The HMD of claim 19 , wherein:
the waveplate comprises a quarter waveplate; and
the quarter waveplate and the absorptive linear polarizer mitigate reflections of light from at least one surface of the user's eye polarized in a direction of at least the portion of the image light being transmitted by the front optical element.

Assignees

• Facebook Tech Llc

Inventors

• Gollier Jacques
• Ouderkirk Andrew John

Classifications

• G02B27/0172

  characterised by optical features · CPC title

• G02B2027/0138

  comprising image capture systems, e.g. camera · CPC title

• G02B27/281

  used for attenuating light intensity, e.g. comprising rotatable polarising elements · CPC title

• G02B27/0018 Primary

  with means for preventing ghost images (anti-reflection coatings G02B1/11) · CPC title

• G02B27/0176

  characterised by mechanical features · CPC title