| 摘要 |
<P>PROBLEM TO BE SOLVED: To accurately calibrate a deviation of a detection value caused by a change with the lapse of time in a sensing element, using the two sensing elements with an equal sensing characteristic. <P>SOLUTION: The present invention uses an a-Si TFT 1 and an a-Si TFT 2 having equal photoelectric transfer characteristic. Incident luminous energy of the a-Si TFT 1 is reduced by a filter 3 to delay the progress of light deterioration in the a-Si TFT 1. A light deterioration rate d<SB>2</SB>of the a-Si TFT 2 or a light deterioration rate d<SB>1</SB>of the a-Si TFT 1 is specified based on measured values i<SB>1</SB>', i<SB>2</SB>' of leak currents in the a-Si TFTs 1, 2, and based on an integrated illuminance-light deterioration rate profile data stored in a memory, and an illuminance of environmental light is found using the specified light deterioration rate d<SB>2</SB>or d<SB>1</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT |
