Multiple phase light modulation using binary addressing

• US 5,606,441 A
• Filed: 02/24/1994
• Issued: 02/25/1997
• Est. Priority Date: 04/03/1992
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Boysel, R. Mark, Florence, James M.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Dudek, James A.
• Application Number:
  US08/201,307
• Time in Patent Office: 1,097 Days
• Field of Search: 359/93, 359/94, 359/95, 359/291, 359/292, 359/204, 359/212, 359/223, 359/224, 359/846, 359/849, 359/243, 359/263, 359/246
• US Class Current: 349/33
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G03H 1/08 Synthesising holograms, i.e. holograms synthesized from objects or objects from hologramsusing electric digital computers G06F; G06T
• CPC Class Codes: G03H 1/0841 Encoding method mapping the synthesized field into a restricted set of values representative of the modulator parameters, e.g. detour phase coding
• CPC Class Codes: G03H 1/2294 Addressing the hologram to an active spatial light modulator
• CPC Class Codes: G03H 2001/0066 for wavefront matching wherein the hologram is arranged to convert a predetermined wavefront into a comprehensive wave, e.g. associative memory recognition using holographic masks G06V10/88
• CPC Class Codes: G03H 2001/085 Kinoform, i.e. phase only encoding wherein the computed field is processed into a distribution of phase differences
• CPC Class Codes: G03H 2001/0858 Cell encoding wherein each computed values is represented by at least two pixels of the modulator, e.g. detour phase coding
• CPC Class Codes: G03H 2223/13 Phase mask
• CPC Class Codes: G03H 2225/24 Having movable pixels, e.g. microelectromechanical systems [MEMS]
• CPC Class Codes: G03H 2225/31 Amplitude only
• CPC Class Codes: G03H 2225/32 Phase only
• CPC Class Codes: G03H 2225/55 Having optical element registered to each pixel
• CPC Class Codes: G03H 2240/41 Binary
• CPC Class Codes: G03H 2240/42 Discrete level
• CPC Class Codes: G09F 9/372 the positions of the elements being controlled by the application of an electric field

Abstract

A method for multiple phase light modulation, said method comprising providing a pixel (20) having at least two modulating elements (22), (24). The method further comprising addressing said at least two modulating elements (22), (24) whereby light incident on said addressed element undergoes discrete phase changes between addressable states. The method further comprises resolving light from said at least two modulating elements (22), (24), into a response having at least three unique phases. Other devices, systems and methods are also disclosed.

Claims

1. A method for multiple phase light modulation using an array of pixels, said method comprising:

providing a first and second set of address electrodes;

providing a pixel having a first and second movable reflective element, said first movable reflective element being associated with said first set of address electrodes and said second movable reflective element being associated with said second set of address electrodes, each of said first and second elements being vertically translated in response to address voltages placed on their respective set of address electrodes;

addressing said movable reflective elements by placing voltages upon the set of address electrodes associated therewith, said voltages operable to vertically translate said movable reflective elements such that light incident thereon undergoes a discrete change in phase; and

combining light from said movable reflective elements into a single response having at least three unique phases.

2. The method of claim 1, wherein at least one of said movable reflective elements is vertically translated by an odd multiple of one fourth of a selected light wavelength whereby a π

radian phase difference exists between light reflected from said at least one vertically translated reflective element and another non-vertically translated reflective element.

3. The method of claim 1, wherein said movable reflective elements are vertically differentiated by an odd multiple of one eighth of a selected light wavelength whereby a π

/2 radian phase difference exists between light reflected from said first movable reflective element and said second movable reflective element.

4. The method of claim 1 wherein said first and said second sets of address electrodes each consist of a singular address electrode.

5. The method of claim 1 wherein said step of addressing said movable reflective elements is binary addressing.

6. A multiple phase light modulator having pixels, said pixels comprising:

a first modulating element switchable between at least two addressable states;

a second modulating element, switchable between at least two addressable states, adjacent to said first modulating element and formed such that said second modulating element will effect a phase difference between light incident thereon and light incident on and acted upon by said first modulating element;

addressing circuitry underlying said first and second modulating elements, said addressing circuitry capable of physically altering said modulating elements whereby discrete phase changes may be induced corresponding to said at least two addressable states of said modulating elements; and

a mixer for combining the responses from said first and second modulating elements into a single response having a phase state that is one of a plurality of possible phase states that is dependent upon the addressed states of said first and second modulating elements.

7. The modulator of claim 6, said modulator further comprising:

a third modulating element, switchable between at least two addressable states, adjacent to said first modulating element and formed such that said third modulating element will effect a phase difference between light incident thereon and light incident on and acted upon by said first modulating element; and

a fourth modulating element, switchable between at least two addressable states, adjacent to said second and third modulating elements and diagonally opposed to said first modulating element and formed such that said fourth modulating element will effect a phase difference between light incident thereon and light incident on and acted upon by said second and third modulating elements.

8. The modulator of claim 6, wherein said modulating elements are switchable between two addressable states.

9. The modulator of claim 6, wherein said at least two modulating elements are movable reflective elements which are vertically translated in response to an address voltage being placed on their respective address electrodes.

10. The modulator of claim 9, wherein at least one of said at least two movable reflective elements is vertically translated by an odd multiple of one fourth of a selected light wavelength whereby a π

radian phase difference exists between light reflected from said at least one vertically translated reflective element and another non-vertically translated reflective element.

11. The modulator of claim 9, wherein said at least two movable reflective elements are vertically differentiated by an odd multiple of one eighth of a selected light wavelength whereby a π

/2 radian phase difference exists between light reflected from one of said at least two movable reflective elements and another of said at least two movable reflective elements.

12. A method for multiple phase light modulation using an array of pixels, said method comprising:

providing a first set of address electrodes;

providing a first modulating element associated with said first set of address electrodes and switchable between at least two states,

providing a second set of address electrodes;

providing a second modulating element associated with said second set of address electrodes and switchable between at least two states, adjacent to said first modulating element whereby said first and second modulating elements together form a single pixel when light reflected therefrom are combined into a single response, said second modulating element being normally perpendicularly offset from said first modulating element such that a phase difference is effected between light incident thereon and light incident on and acted upon by said first modulating element; and

illuminating said single pixel comprising said first and second modulating elements with a coherent light source impinging upon said first and second modulating elements in a perpendicular fashion, whereby said light reflected from said single pixel is combined into a single response.

13. A method for multiple phase light modulation using an array of pixels, said method comprising:

providing a pixel having at least two reflective modulating elements which are vertically responsive to an address voltage being placed on their respective address electrodes, said modulating elements being addressable to at least two unique states represented by a certain degree of vertical translation;

addressing at least one of said at least two modulating elements by applying a voltage to said at least one modulating element to vertically translate said at least one modulating element by an odd multiple of one fourth of a selected light wavelength whereby a π

radian phase difference exists between light reflected from said at least one addressed modulating element and the other of said at least two modulating elements; and

combining light from said at least two modulating elements into a single response such that said single response is one of at least three unique phases that result from the differing combinations of said addressed states of said at least two modulating elements.

14. The method of claim 13, wherein said at least two modulating elements are vertically differentiated by an odd multiple of one eighth of a selected light wavelength whereby a π

/2 radian phase difference exists between light reflected from said at least one addressed modulating element and the other of said at least two modulating elements.

15. A multiple phase light modulator having pixels, said pixels comprising:

a first modulating element switchable between at least two addressable states;

a second modulating element, switchable between at least two addressable states, adjacent to said first modulating element and formed such that said second modulating element will effect a phase difference between light incident thereon and light incident on and acted upon by said first modulating element;

addressing circuitry underlying said first and second modulating elements, said addressing circuitry capable of vertically translating by an odd multiple of one fourth of a selected light wavelength said first modulating element by placing a voltage on its respective address electrode, such that a π

radian phase difference is established between light reflected from said first modulating element and said second modulating element; and

a mixer for combining the responses from said first and second modulating elements into a single response having a phase state that is one of a plurality of possible phase states that is dependent upon the addressed states of said first and second modulating elements.

16. The modulator of claim 15, wherein said first and second modulating elements are vertically differentiated by an odd multiple of one eighth of a selected light wavelength whereby a π

/2 radian phase difference exists between light reflected from said first and said second modulating elements.