Optical switching element and image display device

Abstract

The present invention provides an optical switching element causing less loss of light and permitting high response, thinning of an optical system for illumination, and the realization of an image display device exhibiting precise grayscale properties. In the optical switching element, an extraction surface of a light extraction unit mounted to a thin film is brought into contact with the total reflection surface of a light guide serving as a light guide unit comprising a glass plate or the like for transmitting light by total reflection, or near at a distance from the total reflection, surface for allowing extraction of evanescent waves, to extract the incident light transmitted through the light guide and emit the extracted light to the outside through an emission member. Such optical switching permits the light extract unit to be operated in a range of approximately a wavelength or half a wavelength, thereby providing an optical switching element capable of high-speed operation and having high contrast because the incident light does not leak due to total reflection during an off time.

What is claimed is:  
     
         1 . An optical switching element, comprising: 
 a light guide unit having a total reflection surface that can transmit light by total reflection; and    a light extraction unit having a transmissive extraction surface, the transmissive extraction surface being movable between a first position at or less than an extraction distance from the total reflection surface such that an evanescent wave can leak, and a second position greater than the extraction distance from the total reflection surface.    
     
     
         2 . The optical switching element according to  claim 1 , the light extraction unit further comprising an emission member that emits light extracted by the transmissive extraction surface.  
     
     
         3 . The optical switching element according to  claim 2 , the emission member comprising at least one of an emission surface and a reflection surface which is disposed at an angle relative to the total reflection surface.  
     
     
         4 . The optical switching element according to  claim 2 , the emission member comprising at least one of a micro prism and a micro lens.  
     
     
         5 . The optical switching element according to  claim 2 , the emission member comprising an optical element shaped as at least one of a truncated cone and a truncated pyramid which expands in an emission direction.  
     
     
         6 . The optical switching element according to  claim 2 , the emission member having a light scattering ability.  
     
     
         7 . The optical switching element according to  claim 2 , the emission member emitting light by the extracted light.  
     
     
         8 . The optical switching element according to  claim 7 , the emission member including a fluorescent agent.  
     
     
         9 . The optical switching element according to  claim 1 , the light extraction unit having wavelength selectivity.  
     
     
         10 . The optical switching element according to  claim 1 , the light extraction unit being of a transmission type which guides extracted light in a direction opposite to the transmissive extraction surface, the light extraction unit being provided on an emission side of the optical switching element relative to the light guide unit.  
     
     
         11 . The optical switching element according to  claim 1 , the light extraction unit being a reflection type which guides extracted light to the transmissive extraction surface, the light extraction unit being provided on a side opposite to an emission side of the optical switching element relative to the light guide unit.  
     
     
         12 . The optical switching element according to  claim 1 , the light extraction unit being of at least one of a scattering type which scatters extracted light extracted by the transmissive extraction surface, and an emission type which emits light by extracted light, and a light absorbing layer is disposed on a side opposite to an emission side of the optical switching element relative to the light guide unit.  
     
     
         13 . The optical switching element according to  claim 1 , further comprising a static light processing unit provided on an emission side of the optical switching element where extracted light extracted by the light extraction unit is emitted.  
     
     
         14 . The optical switching element according to  claim 13 , the light processing unit having a wavefront converting function.  
     
     
         15 . The optical switching element according to  claim 13 , the light processing unit having a wavelength selecting function.  
     
     
         16 . The optical switching element according to  claim 13 , the light processing unit having at least one of a scattering and light emitting function.  
     
     
         17 . The optical switching element according to  claim 1 , further comprising a spacer and a thin film laminated on the light guide unit via the spacer so that the light extraction unit is supported by the thin film.  
     
     
         18 . The optical switching element according to  claim 10 , further comprising a spacer and a transmissive thin film laminated on the emission side of the optical switching element relative to the light guide via the spacer so that the light extraction unit is supported by the transmissive thin film.  
     
     
         19 . The optical switching element according to  claim 11 , further comprising a spacer and a reflective thin film laminated on the side opposite to the emission side of the optical switching element relative to the light guide via the spacer so that the light extraction unit is supported by the reflective thin film.  
     
     
         20 . The optical switching element according to  claim 17 , further comprising a driving unit that can drive the light extraction unit supported by the thin film.  
     
     
         21 . The optical switching element according to  claim 20 , the driving unit being capable of electrostatically driving the light extraction unit.  
     
     
         22 . The optical switching element according to  claim 21 , further comprising a transparent electrode provided on the total reflection surface.  
     
     
         23 . The optical switching element according to  claim 21 , the light extraction unit further comprising an emission member that emits light extracted by the transmissive extraction surface, and a transparent electrode is provided on a light guide side of the emission member.  
     
     
         24 . The optical switching element according to  claim 21 , the spacer having a prismatic shape for supporting the light extraction unit at each of four positions.  
     
     
         25 . The optical switching element according to  claim 21 , the thin film being joined to the spacer by electrostatic thermal junction.  
     
     
         26 . An image display device comprising a plurality of optical switching elements, each of the optical switching elements having a structure according to  claim 1 , the optical switching elements being disposed in a two-dimensional form, the light guide unit of each of the optical switching elements being connected to transmit light.  
     
     
         27 . The image display device according to  claim 26 , further comprising a spacer and a thin film laminated on the light guide unit of each of the optical switching elements via the spacer, for supporting the light extraction unit of each of the optical switching elements.  
     
     
         28 . The image display device according to  claim 27 , the spacer having a prismatic shape for supporting the light extraction unit of each of the optical switching elements at each of four positions.  
     
     
         29 . The image display device according to  claim 27 , the thin film being joined to the spacer by electrostatic thermal junction.  
     
     
         30 . The image display device according to  claim 27 , further comprising a driving unit that can drive the light extraction unit of each of the optical switching elements supported by the thin film.  
     
     
         31 . The image display device according to  claim 30 , the driving unit comprising a scanning electrode and a sub-scanning electrode perpendicular to the scanning electrode so that at least one of the scanning electrode and the sub-scanning electrode is disposed on the light guide unit of at least one of the optical switching elements, the other being disposed on at least one of the thin film and the light extraction unit of each of the optical switching elements.  
     
     
         32 . The image display device according to  claim 31 , wherein the at least one of the scanning electrode and the sub-scanning electrode provided on the light guide unit is a transparent electrode.  
     
     
         33 . The image display device according to  claim 27 , each of the light extraction units having wavelength selectivity.  
     
     
         34 . The image display device according to  claim 27 , further comprising a light source that can supply light of primary colors to the light guide unit of each of the optical switching elements in a time division manner.  
     
     
         35 . A method of manipulating light, comprising the step of: 
 moving a transmissive extraction surface of a light extraction unit between a first position at or less than an extraction distance from a total reflection surface of a light guide unit such that evanescent light can leak, and a second position greater than the extraction distance from the total reflection surface.    
     
     
         36 . The method according to  claim 35 , further comprising the step of emitting light extracted by the transmissive extraction surface with an emission member of the light extraction unit.