PURPOSE: To eliminate reading operation from being unstable owing to bad surface states of the marking surface of a body to be recognized due to painting, water wetting, etc., by sensing a nonmarking and a marking area on the marking surface in the form of variation in atmospheric pressure.
CONSTITUTION: A marking pattern sensor 11 scans over the marking surface 12 of the body 1 to be recognized, and when a small ball 17 as the probe of the sensor 11 is over the nonmarking area 15 on the marking surface 12, the small ball 17 is moved up from the circular edge 19a of an element 19 to form a gap S between the both, so the atmospheric pressure in a cylinder 20 is released continuously to the air through the gap S. Therefore, an atmospheric pressure-electric transducing element 18 outputs a low-level signal. When the scan is advanced until the sensor 11 moves to over the marking area 16 on the marking surface 12, the small ball 17 falls in the groove (g) in the marking area 16 and the gap S left so far is eliminated to raise the atmospheric pressure in the cylinder body 20. Therefore, the transducing element 18 outputs a high- level signal.
INAGAKI YUUSHI
IKEDA HIROYUKI
NAKAJIMA MASAHITO
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