| 摘要 |
PURPOSE:To smoothen and make smaller the noise level of an audio output in an audio frequency band, by arranging the supporting point of a needle arm so that the resonance frequency of the needle arm related to a distance between a supporting part and supporting point of a scanning needle becomes higher than the audio frequency. CONSTITUTION:A needle arm 40 consists of a base part 41, axis part 42 and an intermediate part 70 which is arranged between the base part and axis part and has larger sectional area than that of the axis part 42. The intermediate part 70 is formed integral with the base part 41 and axis part 42 and consists of the 1st part 71 having the same sectional area as that of the axis part 42, and the 2nd part 72 of a flat plate shape mounted on the top surface of the 1st part. Actually, they are constituted by mounting the 2nd part 72 on the axis part on the base side of a conventional needle arm. The supporting point of the needle arm 40 exists in the boundary part between the axis part 42 and the intermediate part 70, and a distance Z between the supporting point P' and needle supporting part becomes shorter by the length R of the intermediate part 70 than that of the conventional one. Namely, a distance Z' is nearly halved, and a resonance frequency becomes about four times to exceed the upper limit of the audio frequency band. |
