| 摘要 |
PURPOSE:To achieve a highly accurate measurement of the S/N ratio with a simple construction by employing a linear array of numerous ON-OFF type light receiving elements as a photo detector. CONSTITUTION:A fine light beam 14 from a light source 11 is introduced to the surface of an area plate 10b at an angle theta from a slant direction with a light transmission path 13. The reflect light is received with a photo detector 12 to be converted to an electrical signal. The photo detector 12 is made up of a photo diode array in which numerous ON-OFF type light receiving elements 12a-12n are arranged linearly and placed in the direction of receiving the reflected light 18 from the area plate 10b in such a manner as to be orthogonal to the reflected light 18. |
