In a display device with optical sensors, a recognition processing portion (22) performs recognition processing on a scan picture generated by optical sensors (2), and calculates a position. A mode control portion (24) determines whether or not the mode is standby so that the recognition processing portion (22) is stopped from operating. At the time of transition to the standby mode, decimated image memory (25) stores a decimated image with a decreased number of pixels. The mode control portion (24) performs pixel-by-pixel comparison between the stored decimated image and a decimated image supplied anew, and exits the standby mode when the number of pixels whose difference in pixel values is greater than or equal to a first threshold is greater than or equal to a second threshold. Here, the first and second thresholds are appropriately set in accordance with an ambient luminance L from a luminance sensor (20), and therefore, any change in the image can be accurately distinguished from noise, thereby preventing the standby mode from being or not being cancelled by mistake.