| 摘要 |
PROBLEM TO BE SOLVED: To prevent malfunctions due to the irregularly reflected light by shielding the light irregularly reflected at the inner surface of upper/lower half cases constituting a magnetic tape cassette or at a tape reel, before entering into light transmission holes. SOLUTION: Light shielding walls 41 are provided with wall parts 41a, 41b different in height from the inner surfaces of the upper/lower half cases 2 near the light source side of the light transmission holes 48 formed in the upper/lower half cases 2, then the straight-advancing light (a) projected from the light source L is passed through the light transmission holes 48 and is received by an optical sensor S. On the other hand, the light irregularly reflected by the inner surface or the tape reel is shielded with the light shielding walls 41, and it does not enter into the light transmission holes 48. Consequently, the erroneous operation is not generated even when the magnetic tape is blurred, and the time when the tape comes up to the end is surely detected so as to make the operation to transit to the next mode.
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