Position detection system and projection display system

Abstract

An optical position detection system includes a light output unit that outputs lights toward a first detection target and a second detection target, and a first light receiving unit that receives a first reflected light from the first detection target and a second light receiving unit that receives a second reflected light from the second detection target having different wavelengths, wherein the first detection target has a first reflection filter that reflects the first reflected light and the second detection target has a second reflection filter that reflects the second reflected light.

What is claimed is: 
     
         1 . A position detection apparatus comprising:
 a light output unit that outputs light toward a first detection target and a second detection target;   a first light receiving unit that receives light and detects, by distinguishing wavelengths of the light, a first reflected light reflected by the first detection target;   a second light receiving unit that receives light and detects, by distinguishing wavelengths of the light, a second reflected light reflected by the second detection target; and   a position detection unit that detects positions of the first detection target and the second detection target based on detection values of the first and second light receiving units.   
     
     
         2 . The position detection apparatus according to  claim 1 , wherein the first light receiving unit and the second light receiving unit are provided in one photodetector. 
     
     
         3 . The position detection apparatus according to  claim 2 , wherein an angle formed by a line connecting the light output unit and the first detection target and a line connecting the photodetector and the first detection target is 10 degrees or less, and an angle formed by a line connecting the light output unit and the second detection target and a line connecting the photodetector and the second detection target is 10 degrees or less. 
     
     
         4 . A projection display system comprising:
 the position detection system according to  claim 1 ; and   an image irradiation system that projects an image on a reference surface.   
     
     
         5 . A light reflecting device for a position detection apparatus comprising:
 a detection target that is held by a user's hand; and   a reflection filter on the detection target that reflects light having a predetermined wavelength.   
     
     
         6 . The light reflecting device according to  claim 5 , wherein the reflection filter has a frequency filter and a retroreflector that reflects incident light in an opposite direction to an incident direction. 
     
     
         7 . The light reflecting device according to  claim 6 , wherein the retroreflector has a prism shape. 
     
     
         8 . The light reflecting device according to  claim 6 , wherein the frequency filter is provided by coating or bonding on a surface of the retroreflector. 
     
     
         9 . A method comprising:
 outputting light toward a first detection target and a second detection target;   detecting a first reflected light reflected by the first detection target and a second reflected light reflected by the second detection target by distinguishing wavelengths of the light reflected by the first and second detection targets; and   detecting positions of the first detection target and the second detection target based on a detection value of the received light.   
     
     
         10 . The method of  claim 9  wherein:
 the first and second detection targets are holdable by a user's hand; and wherein: 
 the first and second detection targets reflect light of different wavelegnths.