Display device including function to input information from screen by light
View Patent ↗In order to enhance accuracy of determination as to whether an object has contacted a screen and to enhance accuracy of calculation of a coordinate position of the object, edges of an imaged image are detected by an edge detection circuit 76 , and by using the edges, it is determined by a contact determination circuit 77 whether or not the object has contacted the screen. Moreover, in order to appropriately control sensitivity of optical sensors in response to external light, by a calibration circuit 93 , a drive condition of the optical sensors is changed based on output values of the optical sensors, which are varied in response to the external light.
1. A display device, comprising:
a display unit configured to display an image on a screen, and is an image of an object which has approached the screen, by using optical sensors; and
a sensor drive unit configured to change a drive condition of the optical sensors based on a statistical amount of output values of the optical sensors,
wherein the sensor drive unit outputs a control signal which controls the drive condition so that upper gradation values including a center in a histogram of gradation values obtained by modulating the output values can be set within a predetermined range,
wherein the sensor drive unit decides the control signal by using a table showing a relationship between an exposure time of the optical sensors, a precharge voltage thereof, and the predetermined range.
2. The display device according to claim 1 ,
wherein the drive condition is at least one of an exposure time and precharge time of the optical sensors.
3. The display device according to claim 1 ,
wherein the display unit is one configured to display, on a screen, a region which an object is made to approach, and
the sensor drive unit changes the drive condition based on a statistical amount of output values of the optical sensors arranged in a region on the screen, the region other than the region which the object is made to approach.
4. The display device according to claim 1 ,
wherein the sensor drive unit is capable changing the upper gradation values in response to sizes of the screen and the object.
5. The display device according to claim 1 ,
wherein the table is one, in which the exposure time is maximized in an allowable range, and the precharge voltage is changed.
6. The display device according to claim 1 ,
wherein the sensor drive unit decides the control signal by a linear search method by using the table.
7. The display device according to claim 1 ,
wherein the sensor drive unit decides the control signal by a binary search method by using the table.
8. The display device according to claim 1 ,
wherein the sensor drive unit uses gradation values of pixels which have been subjected to thinning processing performed for each of plural regions obtained by partitioning the screen in a fixed range.
9. The display device according to claim 1 ,
wherein the sensor drive unit provides a predetermined standby period between a point of time when the output values of the optical sensors are changed to an extent where the drive condition of the optical sensors is to be changed and a point of time when the drive condition of the optical sensors is actually changed.
10. The display device according to claim 9 , further comprising a hold unit configured to hold the statistical amount during the predetermined standby period.