| 摘要 |
PROBLEM TO BE SOLVED: To provide a reader which can highly precisely read the surface of a read object at high speed regardless of the change of a peripheral temperature. SOLUTION: A marking reader 10 is formed of an illumination LED 24 irradiating an image pickup area C with illumination light, and area sensor 26 which image-picks up the surface of a coin A and a control part 42 deciding illumination time when illumination is radiated. The control part 42 is formed of a first timer circuit 52 clocking a time interval t1 which changes while depending on the peripheral temperature, a second timer circuit 54 clocking a time interval t2 which depends on the peripheral temperature and whose peripheral temperature dependency differs from that of the time interval t1 and an illumination control signal generation circuit 58 deciding the illumination time of the illumination LED 24 based on the time intervals t1 and t2. The illumination control signal generation circuit 58 decides illumination time so that the product of illumination intensity and illumination time becomes an almost constant value regardless of the peripheral temperature.
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