Display device
A display device with a touch pad function is provided which reduces the elements required to form a photo sensor while still accurately detecting input coordinate positions. The display device includes a display part on which a plurality of pixels are arranged in a matrix array, a plurality of photo detection circuits which are arranged in a matrix array in the inside of the display part, wherein each photo detection circuit of the plurality of photo detection circuits includes: a photo sensor which converts an incident light into a optical current corresponding to intensity of the incident light, an integral capacitance which integrates the optical current converted by the photo sensor, and a comparator to which a voltage of the integral capacitance is inputted, and the comparator includes a transistor of an open drain output type with a grounded source.
1. A display device comprising:
a display part on which a plurality of pixels are arranged in a matrix array; and
a plurality of photo detection circuits which are arranged in a matrix array in the inside of the display part, wherein
the display part includes:
a plurality of X output lines and a plurality of Y output lines which intersect the plurality of X output lines, and
each photo detection circuit of the plurality of photo detection circuits includes:
a photo sensor which converts an incident light into an optical current corresponding to intensity of the incident light;
an integral capacitance which is connected in series to one end of the photo sensor and integrates the optical current which is converted by the photo sensor, and
a comparator to which a voltage of the integral capacitance is inputted, said comparator comprising first and second transistors, each having a control electrode thereof connected to a node between the photo sensor and the integral capacitor, wherein each of the first and second transistors has a grounded source,
wherein the first transistor has a drain coupled to one of the plurality of X output lines, and
wherein the second transistor has a drain coupled to one of the plurality of Y output lines.
2. A display device according to claim 1 , wherein the display device includes a reset line which is connected to another end of the photo sensor, and
an integrated capacitance initializing voltage which initializes the integrated capacitance is applied to the reset line in an initial stage of a detection period for detecting a photo detection circuit to which light is radiated out of the plurality of photo detection circuits.
3. A display device according to claim 1 , wherein said comparator of each of said photo detection circuits is configured to determine whether or not the voltage of the integral capacitance has exceeded a predetermined voltage threshold to thereby determine whether a portion of the display part where the photo detection circuit is located has been touched.
4. A display device comprising:
a display part on which a plurality of pixels are arranged in a matrix array; and
a plurality of photo detection circuits which are arranged in a matrix array in the inside of the display part, wherein
each photo detection circuit of the plurality of photo detection circuits includes:
a photo sensor which converts an incident light into a optical current corresponding to intensity of the incident light;
an integral capacitance which integrates the optical current converted by the photo sensor; and
a comparator to which a voltage of the integral capacitance is inputted; and
the comparator includes a transistor of an open drain output type with a grounded source,
wherein said comparator of each of said photo detection circuits is configured to determine whether or not the voltage of the integral capacitance has exceeded a predetermined voltage threshold to thereby determine whether a portion of the display part where the photo detection circuit is located has been touched.
5. A display device according to claim 4 , wherein an initializing voltage which initializes the integral capacitance is applied to the integral capacitance via a reset line.
6. A display device according to claim 5 , wherein the X output circuit and the Y output circuit detect the optical currents in multiple gray scales by performing the detection of voltages of the X output lines and the Y output lines plural times during one detection period for detecting the photo detection circuit to which light is radiated out of the plurality of photo detection circuits.
7. A display device according to claims 4 or 5 , wherein the photo sensor is constituted of a diode.
8. A display device according to claim 7 , wherein the photo sensor is constituted of a thin film transistor adopting the diode connection.
9. A display device according to any one of claims 4 or 5 , wherein the photo detection circuit is provided for each pixel out of the plurality of pixels.
10. A display device according to claim 9 , wherein the display device is a liquid crystal display device, and
each pixel out of the plurality of pixels includes a first sub pixel having a first-color color filter, a second sub pixel having a second-color color filter which differs in color from the first-color, and a third sub pixel having a third-color color filter which differs in color from the first-color and second-color, and
the color filters are not arranged on a region where the photo detection circuit is formed.
11. A display device according to claim 4 , wherein the comparator includes first and second transistors of an open drain output type with a grounded source.
12. A display device according to claim 11 , wherein the first and second transistors have a control electrode thereof connected to a node between the photosensor and the integral capacitance.