Method and apparatus for an optical path length extender

• US 10,401,639 B2
• Filed: 11/21/2016
• Issued: 09/03/2019
• Est. Priority Date: 08/12/2016
• Status: Active Grant

• Current Assignee: Avegant Corp
• Original Assignee: Avegant Corp
• Inventors: Evans, Allan Thomas, Gross, Andrew John, Dewald, D. Scott
• Primary Examiner(s): Alexander, William R
• Assistant Examiner(s): Washington, Tamara Y.
• Application Number:
  US15/358,040
• Publication Number:
  US 20180045973A1
• Time in Patent Office: 1,016 Days
• Field of Search: 359298-304
• CPC Class Codes: G02B 27/28 for polarising used in stereoscopes G02B30/25
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34
• CPC Class Codes: G02B 30/25 using polarisation techniques
• CPC Class Codes: G02B 5/3058 comprising electrically conductive elements, e.g. wire grids, conductive particles
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: G02F 2201/17 Multi-pass arrangements, i.e. arrangements to pass light a plurality of times through the same element, e.g. by using an enhancement cavity
• CPC Class Codes: H04N 2213/001 Constructional or mechanical details
• CPC Class Codes: H04N 23/75 by influencing optical camera components

Abstract

A system to adjust light path length using a digital light path length modulator. The digital light path modulator includes an optical path length extender (OPLE) and a polarization modulator. The OPLE has two light paths having different path lengths, so light with a first polarization is directed through a first light path, and the light with a second polarization is directed through a second light path through the OPLE.

Claims

1. A system to adjust light path length comprising a digital light path length modulator, the digital light path length modulator comprising:

a polarization modulator to receive polarized light and to modulate a polarization of some or all of the polarized light; and

an optical path length extender (OPLE) having an entry surface and an exit surface, to direct the light entering the OPLE with a first polarization through the entry surface and along a first light path through the OPLE to exit through the exit surface, and to direct the light entering the OPLE with a second polarization through the entry surface and along a second light path through the OPLE to exit through the exit surface, the second light path through the OPLE having a light path length two or more times longer than the first light path length through the OPLE;

wherein the OPLE is a longitudinal OPLE, and the light entering the OPLE with the second polarization is reflected back towards the entry surface, prior to exiting the OPLE through the exit surface.

2. The system of claim 1, wherein the longitudinal OPLE comprises:

a quarter wave plate, changing a type of polarization between a circular polarization and a linear polarization, such that the light entering the OPLE has circular polarization, and the light exiting the OPLE has linear polarization.

3. The system of claim 1, wherein the longitudinal OPLE includes:

a quarter wave plate to change the polarization of the light between a circular polarization and a linear polarization;

a wire grid polarizer to pass the light having a particular polarization through, and to reflect the light with a different polarization; and

a partially reflective coating to reflect a portion of the light, reversing the circular polarization of the light, such that the reflected light is passed through the wire grid polarizer to exit the OPLE.

4. The system of claim 3, wherein the partially reflective coating is on the entry surface of the longitudinal OPLE, the quarter wave plate is in a center of the OPLE, and the wire grid polarizer is on the exit surface of the longitudinal OPLE.

5. The system of claim 1, wherein the first light path traverses the longitudinal OPLE one time, and the second light path traverses the longitudinal OPLE three times, reflecting off a wire grid polarizer and a partially reflective coating, such that a second light path length through the longitudinal OPLE is a multiple of the first light path length.

6. The system of claim 1, wherein the polarization of the light entering the OPLE is a circular polarization, and the light with the second polarization is converted between the circular polarization and a linear polarization multiple times.

7. The system of claim 1, further comprising:

a second digital light path length modulator, the second digital light path length modulator comprising;

a second polarization modulator, to receive the polarized light exiting from the OPLE, and to modulate the polarization of some or all of the polarized light; and

a second OPLE to further alter relative light path lengths;

thereby creating a plurality of digitally selectable path lengths.

8. The system of claim 7, wherein the second OPLE is not a longitudinal OPLE.

9. The system of claim 1, wherein the longitudinal OPLE includes:

a quarter wave plate to change the polarization of the light between a circular polarization and a linear polarization;

a wire grid polarizer to pass the light having a particular polarization through, and to reflect the light with a different polarization; and

a partially reflective coating to reflect a portion of the light, reversing the circular polarization of the light, such that the reflected light is passed through the wire grid polarizer to exit the OPLE.

10. The system of claim 9, wherein the partially reflective coating is on the entry surface of the longitudinal OPLE, the quarter wave plate between the entry surface and the exit surface of the OPLE, and the wire grid polarizer is on the exit surface of the longitudinal OPLE.

11. A system comprising:

an optical path length extender (OPLE) having two light paths having different path lengths, such that light entering the OPLE with a first polarization is directed through a first light path, and light entering the OPLE with a second polarization is directed through a second light path having a light path length two or more times longer than the first light path length through the OPLE,

wherein the OPLE is a longitudinal OPLE in which the light entering the OPLE with the first polarization passes through the OPLE and exits through an exit surface of the OPLE, and the light entering the OPLE with the second polarization is reflected back through the OPLE prior to exiting through the exit surface of the OPLE.

12. The system of claim 11, wherein the light entering the OPLE with the second polarization passes through the OPLE three times prior to exiting through the exit surface.

13. The system of claim 11, wherein:

the light entering the OPLE with the second polarization is converted to a third polarization,

the light with the third polarization is reflected back from a wire grid polarizer,

the light with the third polarization is converted to the second polarization,

the light with the second polarization is reflected back from a partially reflective surface thereby being converted to the first polarization, and

the light converted to the first polarization passes through the OPLE through the first light path.

14. The system of claim 11, further comprising:

a quarter wave plate to convert the light with the first polarization to a third polarization, and the light with the second polarization to a fourth polarization.

15. The system of claim 11, further comprising:

a partially reflective layer to reflect light;

a quarter wave plate to change polarization between circular polarization and linear polarization; and

a wire grid polarizer, to reflect light with the second polarization and pass light with the first polarization.

16. The system of claim 15, wherein the light entering the OPLE has a circular polarization, and the light exiting the OPLE has a linear polarization.

17. The system of claim 16, wherein a first reflection is from the wire grid polarizer, and a second reflection is from the partially reflective layer.

18. The system of claim 15, wherein the partially reflective coating is on the entry surface of the longitudinal OPLE, the quarter wave plate is between the entry surface and the exit surface of the OPLE, and the wire grid polarizer is on the exit surface of the longitudinal OPLE.

19. The system of claim 11, further comprising:

a second digital light path length modulator, the second digital light path length modulator comprising;

a second polarization modulator, to receive the polarized light exiting from the OPLE, and to modulate the polarization of some or all of the polarized light; and

a second OPLE to further alter relative light path lengths;

thereby creating a plurality of digitally selectable path lengths.