Radial Runout Of Tracks

The following requirements shall be met with the disk rotating at scanning velocity.

- Frequencies below 500 Hz. The radial runout of any Physical Track, i.e. the variation of the distance between the Physical Track and the centre of the centre hole, shall not exceed 140 µm, peak-to-peak. The acceleration shall not exceed 0,4 m/s 2 .

- Frequencies above 500 Hz. The noise in the radial tracking signal is measured in the closed loop situation of the radial servo in a frequency band from 500 Hz to 10 kHz. (zero dB point of the open-loop transfer function of the servo: 200 Hz; cross-over points of the lead network: 65 Hz and 650 Hz; see figure 5). The rms value of the noise in the residual error signal shall correspond to a tracking error of less than 0,03 µm, integration time 20 ms.

In addition, to avoid strong single frequency noise contributions, this rms value shall be less than 0,01 µm when measured with a scanning filter with a width of 100 Hz over a range from 500 Hz to 10 kHz.

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