New Precise Calibration Method of Recorded Disc Level Using Laser Beam
Light pattern method is often used for the calibration of recorded level of disc records. A number of problems, however, are involved in the level calibration of high frequency range by using of the light pattern method. For example, as frequency increases, the ends of light pattern become obscure causing such problems like larger error in the measurement of the light pattern width. Intending to solve these problems, LASER was used as the light source so as the light pattern can be observed as the array of bright lines with different brightness. On the theoretical analysis of this phenomenon, following points were made clearly; 1) Bright lines are arranged at equal intervals and the intervals are affected by the frequency but are free from the influence of the recorded level. 2) the number of bright lines affected by both frequency and recorded level. Therefore, the approximate recorded level can be obtained by counting the number of the bright lines. 3) the bright lines have different brightness respectively and the brightness is affected by frequency and recorded level. The array, therefore, can be utilized for the calibration of recorded level of high accuracy.
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