Optical scanning-type touch panel

• US 20010002694A1
• Filed: 01/18/2001
• Published: 06/07/2001
• Est. Priority Date: 08/18/1998
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Iwamoto, Yasuhide, Sano, Satoshi, Nakazawa, Fumihiko, Yamaguchi, Nobuyasu, Iida, Atsuo
• Granted Patent: US 6,492,633 B2
• Time in Patent Office: Days
• US Class Current: 250/221
• CPC Class Codes: G06F 3/0423 using sweeping light beams, e.g. using rotating or vibrating mirror

Abstract

In order to measure a scanning light cut-off region, an output of a light receiving element and a threshold value set by an MPU are compared by a comparator and a region where the former is smaller than the latter is measured as the scanning light cut-off region. During one cycle of optical scanning, this threshold value is switched in a plurality of stages according to the scanning angle. By accurately measuring the scanning light cut-off region, the correct position and size of an indicator such as a finger or pen are calculated.

Claims

1. An optical scanning-type touch panel comprising:

a light retro-reflecting member disposed outside a predetermined area;

at least two light transmitting and receiving sections, each having an optical scanner for angularly scanning light in a plane substantially parallel to the predetermined area and a light receiving element for receiving reflected light from a portion of the light retro-reflecting member, which portion was illuminated with light;

a measuring section for measuring a scanning light cut-off region formed in the predetermined area by an indicator, based on a scanning angle of said optical scanner and a result of receiving light by said light receiving element;

a calculating section for calculating a position and size of the indicator according to a result of the measurement performed by said measuring section;

an angle detecting section for detecting an angle of the scanning light; and

a memory section for storing a plurality of reference values of different levels,

wherein said measuring section measures the scanning light cut-off region by comparing the result of receiving light by said light receiving element with one reference value selected from the plurality of reference values stored in said memory section according to the angle of the scanning light detected by said angle detecting section.

2. The optical scanning-type touch panel as set forth in

claim 1

,

wherein a large reference value is selected when the angle of the scanning light is small, and a small reference value is selected when the angle of the scanning light is large.

3. The optical scanning-type touch panel as set forth in

claim 1

,

wherein said angle detecting section includes an optical scanning start detector for detecting a start of optical scanning and a timer having the function of measuring time, and detects the angle of the scanning light according to an elapsed time measured by said timer from a time at which the start of optical scanning was detected by said optical scanning start detector.

4. The optical scanning-type touch panel as set forth in

claim 2

,

wherein said angle detecting section includes an optical scanning start detector for detecting a start of optical scanning and a timer having the function of measuring time, and detects the angle of the scanning light according to an elapsed time measured by said timer from a time at which the start of optical scanning is detected by said optical scanning start detector.

5. The optical scanning-type touch panel as set forth in

claim 3

,

wherein said optical scanning start detector detects timing of starting reception of light of not lower than a predetermined level by said light receiving element as the start of optical scanning.

6. The optical scanning-type touch panel as set forth in

claim 4

,

wherein said optical scanning start detector detects timing of starting reception of light of not lower than a predetermined level by said light receiving element as the start of optical scanning.