| 摘要 |
PURPOSE:To make possible the projection of a pit image to the same length as the unit length of pits regardless of the presence or absence of a grating and to read exactly information by making the length of the part where the grating is inscribed in the grating arrangement direction of the pits having the grating shorter than the pit length. CONSTITUTION:The grating shown by diagonal lines is formed to the information pit 33 of an optical card, etc. and the length of the part 34 inscribed with the grating is made shorter than the length of the pit 33. The length of the pit 32 in which the grating is not inscribed is made the same as the length of the pit 33. Light is made incident on such optical card from a light source 3 of an optical head 7 and the light reflected therefrom is projected onto a one-dimensional sensor array 6, by which the information is read. The light reflected by the grating is diffracted and scattered and the quantity of the light is small in the pit 33 in this state. There is no change of the quantity of the light and the quantity of the reflected light increases in the pit 32. The respective projected lengths 32'', 33'' for the pits 32, 33 of the reverse projected image 31 on the array 6 are thereby made equal. The exact reading is thus made possible with the device having the simplified circuitry.
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