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Japanese Patent JP3888175

B2

PROBLEM TO BE SOLVED: To ensure appreciate reading by solving a disadvantage resulting from reflection of illuminating light on a protective layer surface, for a reading object whose surface has a transparent protective layer.
SOLUTION: Reflection of illuminating light radiated from illuminating light sources is minimized on the protective layer surface, and even if the illuminating light reflects on the protective layer surface, the light is prevented from being projected (incident) on a light receiving sensor, so that a disadvantage resulting from reflection of the illuminating light on the protective layer surface can be solved. A first imaginary protective layer plate P1 is set in a position within a total focal length L of an imaging optical system I, and a second imaginary protective layer plane P2 parallel thereto is set in a position outside it. The illuminating light sources are arranged in an area A where an incident angle θ1 to the first imaginary protective layer plane P1 is not larger than Brewster's angle about the protective layer, and the border to a maximal visual field V of the light receiving sensor E is incident on the second imaginary protective layer plane P2 from outside an imaginary reflected ray R reflected on the second imaginary protective layer plane P2.

Hisashi Shigusa
Toshiharu Ishibashi

JP2002032301A

February 28, 2007

February 08, 2002

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株式会社デンソー

G06K7/10; (IPC1-7): G06K7/10

JP7225890A
JP5011049A
JP2000231599A
JP7093461A
JP8287177A
JP9128474A
JP7006198A
JP11203391A

Tsuyoshi Sato

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