According to one embodiment, a display device includes a display pixel allocated at a matrix state in a display area, an image-reading device which detects strength of capacitive coupling by a dielectric material coming close to or making contact with the display area, and a control portion which controls each transistor of the image-reading device. The present invention uses measurements of RR intervals to detect, in particular but not exclusively, atrial fibrillation of a patient. The integrated circuit device wafer is measured to obtain a present set of process parameter values. The calculation circuit is provided between the input unit and the output unit.