Light pickup

Abstract

According to the present invention, an optical pickup device forms one main spot, a first subspot, and a second subspot by irradiation of light on an optical disk having a groove part and a land part. The optical pickup device includes operation circuits which indicate a deviation between each of the optical spots and a track, and alpha detecting means for detecting such an alpha value that a difference in absolute value between SPP1 and alphaSPP2 falls in a preset range, where an AC amplitude of a push-pull signal of the first subspot is SPP1, and an AC amplitude of a push-pull signal of the second subspot is SPP2, wherein SPP1-alphaSPP2 (alpha is a constant) is a land / groove discriminating signal. With this, in the optical pickup device for recording and reproducing information on / from the optical disk having a land / groove part, it is possible to generate a land / groove discriminating signal and a tracking error signal without an offset, thereby performing excellent tracking control.

Description

technical field [0001] The present invention relates to an optical reproducing device for reproducing playback-only optical discs such as compact discs (CDs) and laser discs (LDs), or for recording and reproducing optical discs for record-once and rewritable optical discs. An optical pickup device used in a recording and reproducing device. Background technique [0002] In an optical pickup for a CD or the like, it is necessary to accurately track optical tracks with an interval of 1.6 µm. Therefore, in order to perform stable signal detection, control of less than one-tenth of the track width is required, and error control (tracking servo) of less than 0.1 μm is usually performed. [0003] In the optical pickup device, this control is carried out by parallel movement of the objective lens left and right, and it is necessary to detect a signal (tracking error signal) as long as there is a slight movement in either direction. [0004] Then, a method known as a tracking serv...

AI Technical Summary

Problems solved by technology

Therefore, in the case of performing tracking from a portion where information is not recorded on the optical disc 101 to a portion where information is recorded, as in Figure 8 As shown, in the main beam SP11, although no tracking deviation occurs, a difference in the amount of reflected light occurs.

Therefore, there is a problem that, in the differential signals D11-D12, a tracking offset occurs due to the influence of the difference in the amount of reflected light other than the tracking offset.

[0040] The problem is the result, as shown in Figure 13(b), when a residual bias is added to the TES, the signal phase is only staggered by φb compared with the ideal TES phase, making it difficult to perform correct tracking control

[0041] Furthermore, the L / G discrimination signal is obtained through the operation of (As-Bs) and (Cs-Ds), so the phases of (As-Bs) and (Cs-Ds) are staggered, as shown in Figure 13(c). Compared with the ideal discriminant signal, the phase is only staggered by φc, the correct ridge / groove discrimination is difficult, and it cannot be used for tracking servo input

[0042] In addition, there is a problem that the residual offset tends to increase as the sub-beam position adjustment error on the optical disc during assembly adjustment of the pickup increases.

Therefore, in the existing pick-up, it is necessary to assemble the position adjustment error of the auxiliary beam as small as possible. Therefore, while the assembly is difficult, the yield is low and the related cost is also high.

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