Optical switching element, optical switching device, and color image displaying apparatus

• US 7,492,990 B2
• Filed: 12/04/2006
• Issued: 02/17/2009
• Est. Priority Date: 12/07/2005
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Hashiguchi, Tsuyoshi, Hirai, Hideaki
• Primary Examiner(s): Doan; Jennifer
• Application Number:
  US11/633,001
• Publication Number:
  US 20070127111A1
• Time in Patent Office: 806 Days
• Field of Search: 385/15, 385/16, 385/37, 385/129
• US Class Current: 385/37
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02F 1/21 by interference
• CPC Class Codes: G02F 1/213 Fabry-Perot type
• CPC Class Codes: G02F 1/225 in an optical waveguide structure
• CPC Class Codes: G02F 1/3136 of interferometric switch type
• CPC Class Codes: G02F 1/315 based on the use of controlled internal reflection
• CPC Class Codes: G02F 2201/16 series; tandem
• CPC Class Codes: G02F 2201/305 diffraction grating
• CPC Class Codes: G02F 2203/023 total internal reflection
• CPC Class Codes: G02F 2203/055 wavelength filtering

Abstract

An optical switching element includes a resonant reflection element and a driving unit. The resonant reflection element has a thickness portion functioning as a waveguide layer, with one surface in a thickness direction functioning as a total reflection surface and the other surface having formed thereon a fine periodic structure with fine asperities, the resonant reflection element resonant-reflecting light that is incident from the other surface and has a specific wavelength component. The driving unit varies a resonant wavelength of resonant reflection by varying at least one of a shape and a refractive index of the resonant reflection element.

Claims

1. A multiple wavelength optical switching element, comprising:

a plurality of optical switching elements, each of the plurality of optical switching elements further comprising;

a resonant reflection element having a thickness portion functioning as a waveguide layer, with one surface in a thickness direction functioning as a total reflection surface and other surface having formed thereon a fine periodic structure with fine asperities, the resonant reflection element resonant-reflecting specific wavelength component of light incident from the other surface; and

a driving unit that varies a resonant wavelength of resonant reflection by varying at least one of a shape and a refractive index of the resonant reflection element,

wherein the plurality of optical switching elements are of a transmission type, and

wherein the plurality of optical switching elements are arranged so as to be stacked in a light transmission direction, each of the plurality of optical switching elements having a resonant wavelength before driving by the driving unit is performed being different from a resonant wavelength after driving by the driving unit is performed, each of the plurality of optical switching elements capable of being driven independently, and each of the plurality of optical switching elements being configured to allow lights of other optical switching elements having resonant wavelengths before and after driving by the driving unit to pass through.

2. A color optical switching element, comprising the multiple wavelength optical switching element according to claim 1, wherein at least three of the optical switching elements are arranged so as to be stacked in a light transmission direction, and a resonant wavelength of each of the optical switching element is set to a value allowing light of a desired color to be displayed.

3. A multiple color optical switching device comprising:

the multiple wavelength optical switching element according to claim 1; and

a plurality of light sources,

wherein number is the plurality of light sources and the plurality of optical switching elements are equal, and wherein the plurality of light sources have different light-emission wavelength regions, each of the plurality light sources has a corresponding one of the plurality of optical switching elements and, in each of the plurality optical switching elements, one of a resonant wavelength before and after varying by a driving unit is in a light-emission wavelength region of the corresponding light source, with the resonant wavelength of each of the optical switching elements being varied by a corresponding driving unit to be inside or outside of the light-emission wavelength region of the corresponding light source, and

wherein light of a plurality of colors can be extracted via the multiple wavelength optical switching element.

4. A color optical switching device comprising:

the color optical switching element according to claim 2; and

a plurality of light sources,

wherein number of is the plurality of light sources and the plurality of optical switching elements forming the color optical switching element are equal,

wherein the plurality of light sources have different light-emission wavelength regions, wavelengths of light from the plurality of light are combined to construct a desired color, each of the plurality of light sources has a corresponding one of the optical switching elements, in each of the plurality optical switching element, one of a resonant wavelength before and after varying by the driving unit is in a light-emission wavelength region of the corresponding light source, with resonant wavelength of each of the optical switching elements being varied by a corresponding driving unit to be inside or outside of the light-emission wavelength region of the corresponding light source, and

wherein light of a desired color can be extracted via the color optical switching element.

8. A color projector comprising:

the color optical switching device of claim 4; and

a projection lens, the projection lens being configured to project color image light passing through the color optical switching device onto a screen.

9. A color optical switching element, comprising the multiple wavelength optical switching element according to claim 1,

wherein at least three of the plurality of optical switching elements are arranged so as to be stacked in a light transmission direction, and a resonant wavelength of each of the plurality of optical switching elements is set to a value that allows light of a desired color to be displayed, and

wherein the resonant wavelength of each of the plurality of optical switching elements is determined by refractive index (n) of the resonant reflection element, thickness (t1) of the fine periodic structure, thickness (t2) of the thickness portion, and fill factor (f), the fill factor defined by a ratio of a pitch Λ

of the fine periodic structure and a width W of a convex portion of the fine periodic structure, as f=W/Λ

.

10. The color optical switching element of claim 9, wherein the pitch, the fill factor, the thickness t2, and the thickness t1 of one of the optical switching elements are about 215 nm, about 0.5, about 20 nm, and about 90 nm, respectively.

11. The color optical switching element of claim 9, wherein the pitch, the fill factor, the thickness t2, and the thickness t1 of one of the optical switching elements are about 270 nm, about 0.5, about 20 nm, and about 90 nm, respectively.

12. The color optical switching element of claim 9, wherein the pitch, the fill factor, the thickness t2, and the thickness t1 of one of the optical switching elements are about 320 nm, about 0.5, about 20 nm, and about 90 nm, respectively.

5. An optical switching device comprising:

an optical switching element including a resonant reflection element having a thickness portion functioning as a waveguide layer, with one surface in a thickness direction functioning as a total reflection surface and other surface having formed thereon a fine periodic structure with fine asperities, the resonant reflection element resonant-reflecting specific wavelength component of light incident from the other surface;

a driving unit that varies a resonant wavelength of resonant refection by varying at least one of a shape and a refractive index of the resonant reflection element; and

a light source,

wherein the optical switching device is configured so that a resonant wavelength is varied by the driving unit to be inside or outside of a light-emission wavelength region of the light source, thereby allowing light extracted via the optical switching element to blink.

6. An image displaying apparatus comprising:

an array of optical switching elements, each of the optical switching element including a resonant reflection element having a thickness portion functioning as a waveguide layer, with one surface in a thickness direction functioning as a total reflection surface and other surface having formed thereon a fine periodic structure with fine asperities, the resonant reflection element resonant-reflecting specific wavelength component of light incident from the other surface;

a driving unit that varies a resonant wavelength of resonant refection by varying at least one of a shape and a refractive index of the resonant reflection element; and

a light source unit that irradiates each optical switching element of the optical switching element array with light having one of a resonant wavelength before varying by a driving unit and a resonant wavelength after varying thereby of an optical switching element forming the optical switching element array being included in a light-emission wavelength region.

7. An optical switching element array comprising:

a plurality of optical switching elements arranged in a two-dimensional array, each of the plurality of optical switching elements capable of being driven independently and further comprising;

a resonant reflection element having a thickness portion functioning as a waveguide layer, with one surface in a thickness direction functioning as a total reflection surface and other surface having formed thereon a fine periodic structure with fine asperities, the resonant reflection element resonant-reflecting specific wavelength component of light incident from the other surface; and

a driving unit that varies a resonant wavelength of resonant reflection by varying a shape and a refractive index of the resonant reflection element,

wherein the plurality of optical switching elements are of a transmission type.