Coordinate input device for accurate detection of coordinates of a point on a writing panel having an increased size

• US 6,256,023 B1
• Filed: 07/06/1998
• Issued: 07/03/2001
• Est. Priority Date: 07/11/1997
• Status: Expired due to Term

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Yano, Takashi, Tanaka, Makoto, Tsuda, Kunikazu
• Primary Examiner(s): Saras, Steven
• Assistant Examiner(s): KUMAR, SRILAKSHMI K
• Application Number:
  US09/111,129
• Time in Patent Office: 1,093 Days
• Field of Search: 178/18, 345/176-178
• US Class Current: 345/177
• CPC Class Codes: G06F 3/0436 in which generating transducers and detecting transducers are attached to a single acoustic waves transmission substrate

Abstract

A coordinate input device includes a writing panel which includes a writing surface having two vertical sides and two horizontal sides. A plurality of transmitting units transmit surface acoustic waves SAW to propagate the SAW within the writing panel in one of a vertical direction and a horizontal direction through reflection. A plurality of receiving units receive the SAW from the plurality of transmitting units through reflection, and output detection signals in response to the received SAW, so that coordinates of a specified point on the writing panel are detected based on the detection signals. A plurality of reflectors, provided on the four sides of the writing surface, reflect the SAW from the transmitting units inwardly to the writing panel and reflect the reflected SAW to the receiving units. In the coordinate input device, the plurality of reflectors, the plurality of transmitting units, and the plurality of receiving units are divided into at least two groups with respect to one of the vertical direction and the horizontal direction, respectively, and symmetrically placed about a predetermined line of the writing panel.

Claims

1. A coordinate input device comprising:

a writing panel including a writing surface having two vertical sides and two horizontal

a plurality of transmitting units for transmitting surface acoustic waves SAW to propagate the SAW within the writing panel in one of a vertical direction and a horizontal direction through reflection;

a plurality of receiving units for receiving the SAW from the pluraity of transmitting units through reflection, and for outputting detection signals in response to the received SAW, so that coordinates of a specified point on the writing panel are detected based on the detection signals; and

a plurality of reflectors provided on the four sides of the writing surface for reflecting the SAW from the transmitting units inwardly to the writing panel and for reflecting the reflected SAW to the receiving units,

wherein the plurality of reflectors, the plurality of transmitting units, and the plurality of receiving units are configured to output the detection signals with respect to both the vertical direction and the horizontal direction for each of the plurality of subdivision surfaces of the writing panel and the reflectors on at least one of the vertical sides and the horizontal sides are symmetrically placed about a predetermined line of symmetry of the writing panel and halves of said reflectors are arrayed at mutually opposite supplementary angles to said at least one of the vertical sides and the horizontal sides.

2. The coordinate input device according to claim 1, wherein the plurality of reflectors include:

first transmitting reflectors and first receiving reflectors provided on two opposing sides of the writing surface along a first half of the writing surface; and

second transmitting reflectors and second receiving reflectors provided on the opposing sides of the writing surface along a second half of the writing surface,

the plurality of transmitting units including;

a first transmitting unit for transmitting the SAW to the first transmitting reflectors; and

a second transmitting unit for transmitting the SAW to the second transmitting reflectors,

the plurality of receiving units including;

a first receiving unit for receiving the SAW from the first receiving reflectors; and

a second receiving unit for receiving the SAW from the second receiving reflectors,

wherein the first transmitting reflectors and the second transmitting reflectors are arrayed at a first supplementary angle and at a second supplementary angle, and the first receiving reflectors and the second receiving reflectors are arrayed at the second supplementary angle and at the first supplementary angle.

3. The coordinate input device according to claim 2, wherein the first transmitting reflectors reflect the SAW from the first transmitting unit to the first half of the writing surface and the first receiving reflectors reflect the SAW reflected by the first transmitting reflectors to the first receiving unit, and wherein the second transmitting reflectors reflect the SAW from the second transmitting unit to the second half of the writing surface and the second receiving reflectors reflect the SAW reflected by the second transmitting reflectors to the second receiving unit.

4. The coordinate input device according to claim 2, wherein the plurality of transmitting units and the plurality of receiving units are provided on the writing panel so as to prevent the first receiving unit from receiving the SAW from the second transmitting unit, and to prevent the second receiving unit from receiving the SAW from the first transmitting unit.

5. The coordinate input device according to claim 2, wherein the plurality of transmitting units and the plurality of receiving units are provided on the writing panel such that the first transmitting unit and the second receiving unit do not confront with each other via the writing surface, and wherein the second transmitting unit and the first receiving unit do not confront with each other via the writing surface.

6. The coordinate input device according to claim 1, wherein the plurality of reflectors are symmetrically placed about a vertical center line of the writing panel.

7. The coordinate input device according to claim 1, wherein the plurality of reflectors are symmetrically placed about both a vertical center line of the writing panel and a horizontal center line of the writing panel.

8. The coordinate input device according to claim 1, further comprising a damping member, provided at each of four peripheral edges of the writing panel, for damping SAW which are outwardly reflected by the reflectors on a corresponding one of the four sides of the writing surface, so as to prevent the outwardly reflected SAW from being reflected to the receiving units other than a corresponding receiving unit related to said reflectors.

9. The coordinate input device according to claim 8, wherein the plurality of reflectors are symmetrically placed about both a vertical center line of the writing panel and a horizontal center line of the writing panel.

10. The coordinate input device according to claim 1, further comprising a damping member, provided at a central position of the reflectors on each of the four sides of the writing surface, for damping the SAW from the transmitting units other than a corresponding transmitting unit related to said reflectors.

11. The coordinate input device according to claim 10, wherein the plurality of reflectors are symmetrically placed about both a vertical center line of the writing panel and a horizontal center line of the writing panel.

12. The coordinate input device according to claim 2, wherein the plurality of reflectors further include third transmitting reflectors and third receiving reflectors provided on the vertical sides of the writing surface along a first half of a shorter length of the writing surface, and fourth transmitting reflectors and fourth receiving reflectors provided on the vertical sides of the writing surface along a second half of the shorter length of the writing surface,

wherein the plurality of transmitting units further include a third transmitting unit for transmitting the SAW to the third transmitting reflectors and a fourth transmitting unit for transmitting the SAW to the fourth transmitting reflectors, and the plurality of receiving units further include a third receiving unit for receiving the SAW from the third receiving reflectors and a fourth receiving unit for receiving the SAW from the fourth receiving reflectors,

wherein the third transmitting reflectors and the fourth transmitting reflectors are arrayed at the second supplementary angle and at the first supplementary angle and symmetrically placed about a horizontal center line of the writing panel, and the third receiving reflectors and the fourth receiving reflectors are arrayed at the first supplementary angle and at the second supplementary angle and symmetrically placed about the horizontal center line of the writing panel.

13. The coordinate input device according to claim 12, wherein the plurality of reflectors are provided on the writing panel such that the third transmitting reflectors reflect the SAW from the third transmitting unit in inward directions to the first half of the shorter length of the writing surface and the third receiving reflectors reflect the inwardly reflected SAW from the third transmitting reflectors to the third receiving unit.

14. The coordinate input device according to claim 13, wherein the fourth transmitting reflectors reflect the SAW from the fourth transmitting unit in inward directions to the second half of the shorter length of the writing surface and the fourth receiving reflectors reflect the inwardly reflected SAW from the fourth transmitting reflectors to the fourth receiving unit.

15. The coordinate input device according to claim 1, wherein the writing panel is transparent and covers a display screen of an image display system.

16. An image display system comprising:

a transparent writing panel covering a display screen of the image display system, the writing panel including a writing surface having two vertical sides and two horizontal sides, the writing surface being divided into a plurality of subdivision surfaces.

a plurality of transmitting units for transmitting surface acoustic waves SAW to propagate the SAW within the writing panel in one of a vertical direction and a horizontal direction through reflection;

a plurality of receiving units for receiving the SAW from the plurality of transmitting units through reflection, and for outputting detection signals in response to the received SAW;

a plurality of reflectors provided on the four sides of the writing surface for reflecting the SAW from the transmitting units inwardly to the writing panel and for reflecting the reflected SAW to the receiving units; and

a control unit for detecting coordinates of a specified point on the writing panel based on the detection signals from the plurality of receiving units,

wherein the plurality of reflectors, the plurality of transmitting units, and the plurality of receiving units are configured to output the detection signals with respect to both the vertical direction and the horizontal direction for each of the plurality of subdivision surfaces of the writing panel and the reflectors on at least one of the vertical sides and the horizontal sides are symmetrically placed about a predetermined line of symmetry of the writing panel and halves of said reflectors are arrayed at mutually opposite supplementary angles to said at least one of the vertical sides and the horizontal sides.