Display device with optical sensor included and image reading method employing same

An image reading method for obtaining an image of an object to be scanned by a display device with photosensors that has a plurality of photosensors in a pixel region,

• the display device with photosensors comprising:
• a visible light source that radiates visible light to a pixel region;
• an invisible light source that radiates invisible light to the pixel region;
• a light source control circuit that turns on and off the invisible light source;
• first photosensors that detect an amount of received light when the invisible light source is on;
• second photosensors that detect an amount of received light when the invisible light source is off;
• a memory that has a first region and a second region, the first region storing first reference data obtained from each of the first and second photosensors when the invisible light source is on, the second region storing second reference data obtained from each of the first and second photosensors when the invisible light source is off;
• and
• a calibration circuit that calibrates data obtained from the first photosensors and the second photosensors when the invisible light source is on and off, respectively, by using the data stored in the first region and the second region,
• the image reading method comprising:
• detecting an amount of light reflected by an object to be scanned that is placed on the pixel region, by turning the invisible light source off and the visible light source on, and by causing only display pixels respectively nearest to the third photosensors within a prescribed range in the pixel region to be in a display state and causing other display pixels within said range to be in a non-display state;
• and
• overwriting data obtained from the third photosensors in one of the first region and the second region of the memory.