TOUCH PANEL AND DRIVING METHOD OF THE SAME

• US 20100328269A1
• Filed: 06/15/2010
• Published: 12/30/2010
• Est. Priority Date: 06/25/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: KUROKAWA, Yoshiyuki
• Granted Patent: US 8,982,099 B2
• Time in Patent Office: Days
• US Class Current: 345/175
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/042 by opto-electronic means

Abstract

It is an object to provide a touch panel which includes an A/D converter circuit and has a function of image shooting with high resolution and high-level gray scale and at high operation speed. A touch panel includes a plurality of pixels each provided with a display element and a photo sensor, an A/D converter to which a first potential is applied from a photo sensor, and a reading circuit. The A/D converter includes an oscillation circuit which changes the oscillating frequency of a first signal to be generated in accordance with the first potential and stops oscillating when a second potential is applied thereto from the reading circuit, and a counter circuit which generates a second signal having a discrete value determined in accordance with the oscillating frequency.

Claims

1. A touch panel comprising:

a plurality of pixels each comprising a display element and a photo sensor; and

an A/D converter configured to be supplied with a first potential from the photo sensor, the A/D converter comprising an oscillation circuit and a counter circuit,

wherein the oscillation circuit is configured to generate a first signal having an oscillation frequency determined in accordance with the first potential, and

wherein the counter circuit is configured to generate a second signal having a discrete value determined in accordance with the oscillation frequency.

2. The touch panel according to claim 1,

wherein the oscillation circuit starts oscillating when a second potential is applied thereto,

wherein a period from when the oscillation circuit starts oscillating to when the first signal has a toggle is approximately half an oscillation cycle of the oscillation circuit, and

wherein the first signal is used as a least significant bit of the A/D converter.

3. The touch panel according to claim 1,

wherein the display element comprises a transistor, a storage capacitor, and a liquid crystal element,

wherein the photo sensor comprises a photo diode, and

wherein the transistor, the storage capacitor, the liquid crystal element, and the photo diode are formed over the same substrate.

4. A touch panel comprising:

a plurality of pixels each comprising a display element and a photo sensor; and

an A/D converter configured to be supplied with a first potential from the photo sensor, the A/D converter comprising an oscillation circuit and a counter circuit.

wherein the oscillation circuit comprises a latch circuit,

wherein the oscillation circuit is configured to generate a first signal having an oscillation frequency determined in accordance with the first potential, and to store a potential of the first signal by applying a second potential to the latch circuit, and

wherein the counter circuit is configured to generate a second signal having a discrete value determined in accordance with the oscillation frequency.

5. The touch panel according to claim 4,

wherein the oscillation circuit starts oscillating when a third potential is applied thereto,

wherein a period from when the oscillation circuit starts oscillating to when the first signal has a toggle is approximately half an oscillation cycle of the oscillation circuit, and

wherein a potential of the first signal is stored by application of the second potential to the latch circuit and the stored potential is used as a least significant bit of the A/D converter.

6. The touch panel according to claim 4,

wherein the display element comprises a transistor, a storage capacitor, and a liquid crystal element,

wherein the photo sensor comprises a photo diode, and

wherein the transistor, the storage capacitor, the liquid crystal element, and the photo diode are formed over the same substrate.

7. A driving method of a touch panel comprising the steps of:

applying a first potential from a photo sensor included in each of a plurality of pixels to an A/D converter,

generating a first signal by an oscillation circuit included in the A/D converter, the first signal having an oscillation frequency determined in accordance with the first potential, and

generating a second signal by a counter circuit included in the A/D converter, the second signal having a discrete value determined in accordance with the oscillation frequency.

8. The driving method of a touch panel according to claim 7,

wherein the oscillation circuit starts oscillating when a second potential is applied thereto,

wherein a period from when the oscillation circuit starts oscillating to when the first signal has a toggle is approximately half an oscillation cycle of the oscillation circuit, and

wherein the first signal is used as a least significant bit of the A/D converter.

9. The driving method of a touch panel according to claim 7,

wherein the plurality of pixels each comprising a display element and the photo sensor,

wherein the display element comprises a transistor, a storage capacitor, and a liquid crystal element,

wherein the photo sensor comprises a photo diode, and

wherein the transistor, the storage capacitor, the liquid crystal element, and the photo diode are formed over the same substrate.

10. A driving method of a touch panel comprising the steps of:

applying a first potential from a photo sensor included in each of a plurality of pixels to an A/D converter,

generating a first signal by an oscillation circuit included in the A/D converter, the first signal having an oscillation frequency determined in accordance with the first potential,

storing a potential of the first signal by applying a second potential to a latch circuit, and

generating a second signal by a counter circuit included in the A/D converter, the second signal having a discrete value determined in accordance with the oscillation frequency after storing the potential of the first signal by applying the second potential to the latch circuit.

11. The driving method of a touch panel according to claim 10,

wherein the oscillation circuit starts oscillating when a third potential is applied thereto,

wherein a period from when the oscillation circuit starts oscillating to when the first signal has a toggle is approximately half an oscillation cycle of the oscillation circuit,

wherein the potential of the first signal is stored by application of the second potential to the latch circuit, and

wherein the stored potential is used as a least significant bit of the A/D converter.

12. The driving method of a touch panel according to claim 10,

wherein the plurality of pixels each comprising a display element and the photo sensor,

wherein the display element comprises a transistor, a storage capacitor, and a liquid crystal element,

wherein the photo sensor comprises a photo diode, and

wherein the transistor, the storage capacitor, the liquid crystal element, and the photo diode are formed over the same substrate.