| 摘要 |
A MAGNETIC RECORDING MEDIUM HAVING A SUBSTRATE DISC WITH MICROSCOPIC BUMPS FORMED BY FOCUSING A LASER BEAM, WHEREIN SPACINGS D BETWEEN ADJACENT MICROSCOPIC BUMPS IN THE CIRCUMFERENTIAL DIRECTION OF THE DISC ARE VARIED SO THAT THE FORMULA "1 < [(DMAX - DMIN)/DAVG] X 100 () < 200" IS SATISFIED, WHEREIN DMAX, DMIN AND DAVG ARE THE MAXIMUM, MINIMUM AND AVERAGE SPACINGS, RESPECTIVELY, AS DETERMINED BY A METHOD WHEREIN 2.5OF THE TOTAL NUMBER OF SPACINGS D, HAVING THE LARGEST DIMENSIONS, AND 2.5OF THE TOTAL NUMBER OF SPACINGS D, HAVING THE SMALLEST DIMENSIONS, ARE EXCLUDED; AND DMAS, DMIN AND DAVG ARE MEASURED ON THE REMAINING 95OF THE TOTAL NUMBER OF SPACINGS D. THE BUMP SPACING VARIATION IS ATTAINED, FOR EXAMPLE, BY MODULATING THE PULSE REPETITION FREQUENCY F OF LASER BEAM SO THAT THE RATIO OF "(FMAX - FMIN)/FAVG" IS MAINTAINED IN THE RANGE OF 0.01 TO 100, WHEREIN FMAX, FMIN AND FAVG ARE THE MAXIMUM, MINIMUM AND AVERAGE VALUES, RESPECTIVELY, OF THE F OF LASER BEAM.
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