Funai Electric Company Ltd.

Tadashi Tachibana

Yasunori Kuwayama

Shoji Saito

The magnitude (Ga) of an impact applied to a lens holder is constantly monitored based on an output of an impact sensor. When it is determined that Ga exceeds Gth, focus servo is released, and the lens holder is provided with a force to make it move away from a disk. Upon recheck of Ga, when it is determined that Ga is now equal to or less than Gth, the force having been provided to the lens holder is cancelled, and the focus servo is resumed.

Optical disk device capable of preventing collision between disk and objective lens, and control method thereof

When an optical disc is set to the motor, the slice level is set to a slice level Sk as a reference slice level and a measured jitter value A (S, S) is produced. The slice level is incremented in steps of a fixed quantity Si (S). Then, a measured jitter value B obtained at the incremented slice level is compared with the previous measured jitter value A (S, S). This sequence of process is repeated, and when the measured jitter value A is smaller than the counter value, it is judged that the jitter changes its quantity varying direction to a decreasing direction. Then, the incrementing operation of the slice level is immediately stopped, and the slice level is decremented in steps of another fixed quantity Sd (&#x3c;Si). The previous measured jitter value C is compared with a measured jitter value D after the slice level is decremented (Sto S). When the measured jitter value C is smaller than the counter jitter value, it is judged that the slice level detected at that time is an optimum slice level.

Image reading device for an optical device

In a disc apparatus, a tracking error signal from an optical pickup is outputted to a micro-computer. The micro-computer discriminates a disc that is different in bit density (track pitch) based on amplitude and/or waveform of the tracking error signal.

Disc apparatus with a disc discriminating function

A disc reading apparatus includes a microcomputer. The microcomputer calculates, based on amount data, an outer radius (RM) of an area that is recording data. The reading speed on the determined outer radius is set to a previously set speed (V.sub.2) for the outer circumference. When reading desired data, a radius of an inner circumference (r) of the data-recorded area is calculated from time information (identification data) to calculate a reading speed (V.sub.n) for reading the data. That is, since the disc contains data recorded such that the linear velocity per unit area becomes constant, the position of a pick-up and the reading speed are represented by a generally inversely proportional linear equation. Therefore, the reading speed (V.sub.n) can be calculated based on the inner radius (r) of the area recording the data to be read, the inner and outer radii (RS, RM) of the data-recorded area, and previously set inner and outer speeds (V.sub.1, V.sub.2).

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Daito, Japan

Tadashi Tachibana