Double-layer CD reading head based on phase turnover

Abstract

In the double-layer CD reading head based on phase turnover, the laser beam emitted by the laser source and through collimation lens is splited in the first beam splitter mirror, the transparent laser is made to pass through the first phase board, the second beam splitter mirror, the third beam splitter mirror and the objective and focused onto the first layer of the double-layer CD; and the reflected laser is made to pass through the second reflector, the first reflector, the second phase board, the negative lens, the third beam splitter mirror and the objective and is focused onto the second layer of the double-layer CD. The two laser beams join finally in the detector. The present invention has simple structure and can read precisely CD with relatively high storage density.

Description

technical field [0001] The invention relates to a read-out head for a double-layer optical disc based on phase inversion, in particular suitable for reading a double-layer digital video disc (referred to as DVD). Background technique [0002] The prior art [1] (see J.Taylor, DVD Demystified (McGraw-Hill, New York, 1997)) uses a dual-layer DVD reading system that first focuses on reading information on one layer, and then changes it mechanically. The focus is on the second level, because it is time-sharing reading, which affects the data reading speed. [0003] The prior art [2] (see S. Stankovic, et al, "Integrated optical pickup system for axialdual focus", Appl. ) system, so that it has different focal lengths for the two polarization states of the transverse electric mode (TE) and the transverse magnetic mode (TM), so that different layers can be read by using beams of different polarization states. [0004] Prior art [3] (see R.Katayama, et al, "Dual-wavelength optical...

AI Technical Summary

Problems solved by technology

Both structures of the above-mentioned prior art [2] and [3] have the problems of complex structure and high cost

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