Differential phase detection device and tracking error signal detection apparatus using the same

摘要

A differential phase detection device (70) and a tracking error signal detection apparatus using the same are provided. The differential phase detection device (70) includes a slicer (75) for slicing and digitizing each of first through fourth input signals (a,b,c,d) received from a photodetector (50). A first synthesizer (77) synthesizes the first signal (a) and the third signal (c) to generate a first synthesis signal (sa), and a second synthesizer (79) synthesizes the second signal (b) and the fourth signal (d) to generate a second synthesis signal (sb). A single phase difference detector (85) is used to compare the phase of the first synthesis signal (sa) with the phase of the second synthesis signal (sb) to generate a first phase difference signal (pa) and a second phase difference signal (pb), and a matrix circuit performs subtraction on the first and second phase difference signals (pa,pb) to output a differential phase signal, such as a Tracking Error Signal (TES). Advantageously, the pair of synthesizers (77,79) avoid the need for a delay unit which is used in the prior art. Also, only a single phase difference detector (85) is used. Consequently, the volume of the differential phase detection device (70) is small. In addition, the tracking error signal detection apparatus using the differential phase detection device (70) can detect a tracking error signal which is relatively less influenced by a radial tilt, a tangential tilt, a defocus, a change in the thickness of an optical disc, a change in the depth of a pit recorded on an optical disc and/or the shift of an objective lens, compared to a conventional one.