| 摘要 |
PURPOSE:To easily and accurately correct shading by correcting shading due to the unevenness of a lens or a light source by means of a slit having optionally adjustable structure. CONSTITUTION:Characters or codes irradiated by the light source are optically formed as their image on an image sensor 30 through a lens 20 and the image on the image forming face is electrically scanned by the image sensor 30 to obtain a video signal. Shading is corrected by arranging the slit 10 constituted by superposing thin plates on the front side of the lens 20 and sliding the plates respectively in the right and left direction. A liquid crystal slit can be also applied to the slit.
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