Patent ID: 7692261

Claim:
A method for driving an optical sensor element having a lateral pin structure and including a p-type semiconductor region, an n-type semiconductor region, an i-type semiconductor region which is formed between the p-type semiconductor region and the n-type semiconductor region and which is lower in impurity concentration than the p-type semiconductor region and the n-type semiconductor region, an anode electrode connected to the p-type semiconductor region, and a cathode electrode connected to the n-type semiconductor region, the method comprising: applying a reverse bias voltage V b when detecting a photocurrent, the reverse bias voltage V b satisfying a following relation, V 1 <V b <V sat where V d denotes a reverse bias voltage between the anode electrode and the cathode electrode, I p denotes the photocurrent flowing between the anode electrode and the cathode electrode when the i-type semiconductor region is irradiated with light, V sat denotes a saturation voltage in I p -V d characteristics, and V 1 denotes a reverse bias voltage V d at a crosspoint of a tangential line at V d =0 for the I p -V d characteristics in a first region in which the reverse bias voltage V d is lower than the saturation voltage V sat and a straight line of the I p -V d characteristics in a second region in which the reverse bias voltage V d is the saturation voltage V sat or more.