Optical position detecting device and recording medium including a detection of dust on a light retro-reflector

• US 7,075,054 B2
• Filed: 05/19/2004
• Issued: 07/11/2006
• Est. Priority Date: 04/14/2000
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Iwamoto, Yasuhide, Sano, Satoshi, Nakazawa, Fumihiko, Yamaguchi, Nobuyasu
• Primary Examiner(s): LE, QUE TAN
• Application Number:
  US10/848,007
• Publication Number:
  US 20040218479A1
• Time in Patent Office: 783 Days
• Field of Search: 250/221, 250/559.4
• US Class Current: 250/221
• CPC Class Codes: G02B 5/124 plural reflecting elements forming part of a unitary plate or sheet
• CPC Class Codes: G06F 3/0423 using sweeping light beams, e.g. using rotating or vibrating mirror

Abstract

The position of a light blocking object is detected not only within a display screen, but also outside the display screen. With the use of the function of detecting the position in a region outside the display screen, it becomes possible to provide virtual buttons in this region and detect dust around a light retro-reflector. Dirt on the light retro-reflector is detected based on the levels of light receiving signals of optical units.

Claims

1. An optical position detecting device comprising:

a light retro-reflector provided outside a predetermined region;

at least two optical transceivers, each including an optical scanning unit for angularly scanning light in a plane substantially parallel to the predetermined region and a light receiving unit for receiving reflected light from a portion of said light retro-reflector irradiated with the scanning light; and

a detector for detecting presence of a light blocking object in a region optically scanned by said optical scanning units when a level of light received by said light receiving unit is lower than a predetermined first level and for detecting a position of the light blocking object based on scanning angles of said optical scanning units in this scanning, said optical position detecting device being characterized by further comprising;

a comparing unit for comparing the level of light received by said light receiving unit with a second level higher than the first level; and

a judging unit for making a judgment that said light retro-reflector is dirty when the level of light received by said light receiving unit is higher than the first level and lower than the second level.

2. A computer-readable recording medium having a program recorded thereon for an optical position detecting device comprising:

a light retro-reflector provided outside a predetermined region; and

at least two optical transceivers, each including an optical scanning unit for angularly scanning light in a plane substantially parallel to the predetermined region and a light receiving unit for receiving reflected light from a portion of said light retro-reflector irradiated with the scanning light, the program causing a computer to detect dirt on said light retro-reflector, said recording medium being characterized in that the program includes program code means for causing the computer to make a comparison between a level of light received by said light receiving unit and a predetermined first level and a predetermined second level higher than the first level; and

program code means for causing the computer to make a judgment that said light retro-reflector is dirty when the level of light received by said light receiving unit is higher than the first level and lower than the second level.

3. A computer-readable recording medium having a program recorded thereon for an optical position detecting device comprising:

a light retro-reflector provided outside a predetermined region; and

at least two optical transceivers, each including an optical scanning unit for angularly scanning light in a plane substantially parallel to the predetermined region and a light receiving unit for receiving reflected light from a portion of said light retro-reflector irradiated with the scanning light, the program causing a computer to detect dust on or around said light retro-reflector, said recording medium being characterized in that the program includes program code means for causing the computer to execute detection of a light blocking object present in a region optically scanned by said optical scanning units when a level of light received by said light receiving unit is lower than a predetermined level;

program code means for causing the computer to execute calculation of a position of the light blocking object based on scanning angles of said optical scanning units and results of receiving light by said light receiving units; and

program code means for causing the computer to detect dust on or around said light retro-reflector based on a time during which the level of light received by said light receiving unit is lower than the predetermined level and the calculated position of the light blocking object.