BRIEF DESCRIPTION OF THE DRAWINGS
These objects and other objects, features and advantages of the present intention will become more apparent from the following detailed description of an embodiment of the present invention when taken in conjunction with the accompanying drawings, of which:
FIG. 1 is a perspective view showing the construction of an optical pickup according to the present invention,
FIG. 2 is a zoomed view showing an eccentrically screw in engagement with a pin of the actuator plate,
FIG. 3 is a perspective view showing the spring which holds the actuator plate,
FIG. 4 is a perspective view showing the actuator plate without means supporting the objective lens,
FIG. 5 is a perspective view showing two eccentrically screws,
FIG. 6 is a perspective view showing a slide base, which in connection with FIG. 3 to FIG. 6 forms an exploded perspective view showing the construction of the optical pickup,
FIG. 7 is a perspective view showing the actuator plate with a pin in engagement with an eccentrically screw,
FIG. 8 is a side view showing the directions of movement for EF-phase and tangential tilt adjustment,
FIG. 9 illustrates a so-called R dependence of the EF-phase on tracks of an optical disc,
FIG. 10 is a top view showing the construction of an optical drive,
FIG. 11 is a perspective view showing disc motor mounted on a separate metal plate in a conventional optical drive and
FIG. 12 is a perspective view showing the base plate of a conventional optical drive.
DETAILED DESCRIPTION OF EMBODIMENTS
The invention is described exemplarily for an optical pickup in an optical recording or reproducing apparatus to compensate tolerances between traverse mechanism and disc motor. Reference signs are used with corresponding meanings through the Figures.
An optical recording or reproducing apparatus comprises an optical drive having an optical pickup PU for writing and/or reading information into or from a disc-like optical recording medium placed on a turntable TT as shown in FIG. 10 in a top view. The turntable TT is formed to have a generally disc-like shape, and has provided nearly in the center thereof a projection having a general shape of a truncated cone. When placed in position on the turntable TT, a not shown optical disc is fitted in the center thereof. Thus the optical disc is held at the center of a drive shaft of a disc motor on which the turntable TT spinning the optical disc is mounted. The drive shaft of the disc motor and the disc motor respectively forms in such way a centre of rotation CTROD of the disc.
The optical pickup PU comprises a slide base SB movably supported by a guide shaft GS and a support shaft SS disposed on the chassis or so called base plate BP of the optical drive. The guide shaft GS and the support shaft SS are disposed in parallel to each other, and also in parallel to the top of the turntable TT. The slide base SB has a guide hole GH in which the guide shaft GS is penetrated and a support recess SR in which the support shaft SS is introduced, as shown in FIG. 6. The slide base SB is moved by a sled motor SM shown in FIG. 12 disposed on the base plate BP in a direction away from or toward the turntable TT, radially to the not shown optical disc. The slide base SB moved along guide shaft GS and support shaft SS by the sled motor SM forms the so-called traverse mechanism of the optical drive on which the optical pickup PU with its objective lens OL is arranged. Dashed lines in parallel to the guide shaft GS and the support shaft SS illustrate in FIG. 10 that a distance DS between guide shaft GS and a centre line CL passing through the centre of rotation CTROD of the disc as well passing through the centre of the objective lens OL may vary due to several tolerances as tolerances of the disc or disc motor DM to the guiding shaft GS inside the traverse mechanism, tolerances between guiding shaft hole GH and an actuator fixation inside the optical pickup PU and tolerances between actuator fixation and objective lens OL inside the actuator. Such variations or deviations DV of the centre of rotation CTROD of the disc or of the objective lens OL from the centre line CL are illustrated by dashed lines at both sides of the centre line CL in FIG. 10.
Deviations DV from the centre line CL lead to so-called EF-phase problems, which have a negative impact on the track guidance in so-called three beam scanning systems as shown in FIG. 9. FIG. 9 illustrates a so-called R dependence of the EF-phase on tracks TR of an optical disc. Each track TR is illustrated by three lines, which represent the centre and at both sides a border of the track TR. Said tracks TR may be annular concentric tracks TR or may be formed by a spiral track TR related to a not shown centre of rotation CTROD of the disc. So-called auxiliary beams E and F at both sides of a not shown main beam representing +-first order light provided by the optical pickup PU and meet the border of a track TR independent from a radial distance R1, R2, R3 to the centre of rotation CTROD, if the centre line CL passed through the centre of rotation CTROD of the disc. The auxiliary beams E and F, which are provided to keep a not shown main beam between the auxiliary beams E and F on a track TR are connected by a line for illustration purposes in FIG. 9. However, the auxiliary beams E and F leave the border of tracks TR in case of deviations DV from the centre line CL due to tolerances between the centre of rotation CTROD and the centre of the objective lens OL focusing the beams on the track TR, which leads to a phase shift depended on the direction of the deviation DV and on the radial distance R1, R2, R3 to the centre of rotation CTROD of the disc. That means that a reliable track guidance of a main beam requires an alignment between the centre of rotation CTROD of the disc or disc motor DM and the centre of the objective lens OL focusing the beams on the track TR. Furthermore, it has to be ensured that the optical axis of the objective lens OL and the surface of the optical disc are perpendicular to each other, which requires an inclination adjustment for reliable reading and/or writing information from or on a disc-like optical recording medium. To adjust such a inclination, a spherical adjusting mechanism already has been proposed for a conventional pickup, which comprises a spherical convexity formed on the bottom of a support plate abutting on the slide base SB or so-called optical body, and a spherical concavity formed on the top of the slide base SB on which the support plate abuts and in which the spherical convexity is fitted. The center of curvature of the spherical convexity is located at a position on the optical axis of the objective lens OL where the focused spot of the light beam having passed through the objective lens OL skewed about the center of curvature will be least off a focused spot which would be when the light beam passes through the objective lens OL not skewed. That means in the conventional optical pickup PU, the mounting angle of the biaxial actuator in relation to the slide base SB incorporating the light source is adjusted to keep the objective lens OL from skewing in relation to the disc. In conventional optical drives, tolerances between traverse mechanism moving the pickup PU and disc motor DM are compensated by adjusting the position of the disc motor DM inside the traverse mechanism in respect to the guiding shaft GS as shown in FIG. 11 and FIG. 12. Therefore, the disc motor DM is mounted on a separate metal plate MP which can be adjusted in elongated holes EH in the base plate BP perpendicular to the guiding shaft GS as shown in FIG. 11 and FIG. 12. However,.that means that the centre of rotation CTROD of the disc is adjusted to a new centre line NCL, with offset to a reference centre RC of the set with the disadvantage that the reference centre RC of the complete unit will be misaligned as shown in FIG. 12. This has a negative impact on a reliable loading and clamping of the disc.
Therefore, an optical pickup PU and optical recording or reproducing apparatus incorporating such an optical pickup PU as shown in FIG. 1 to FIG. 8 is recommended, which comprises an adjustment means AM to adjust the actuator plate AP of the optical pickup PU, which holds the objective lens OL, by moving the actuator plate AP on a straight reference surface RS arranged in the slide base SB of the optical pickup PU to a position as defined by an alignment equipment of the optical recording or reproducing apparatus to achieve an alignment between traverse mechanism and disc motor DM. That means that the disc motor DM has not to be adjustable mounted on a separate metal plate MP and will be assembled to the base plate BP of the optical drive at a predetermined fixed position in view of the above mentioned reference centre RC of the set.
FIG. 1 is a perspective view showing the construction of an optical pickup PU according to the present invention to achieve an easy and good adjustment between traverse mechanism and disc motor DM and to align auxiliary beams E, F scanning a disc-like optical recording medium for track guidance. According to the embodiment shown in FIG. 1 the adjustment means AM is at least one eccentrically screw ES moving the actuator plate AP inside the slide base SB against a counter spring CS mounted on the slide base SB.
The actuator plate AP has pins P at both sides sliding on a straight reference surface RS shown in FIG. 2. The reference surface RS is arranged in the slide base SB. At least one of said pins P is in engagement with said eccentrically screw ES as shown in FIG. 2 and slides the actuator plate AP elastically supporting a lens holder holding the objective lens OL. The pins P keep the actuator plate AP moveable and rotatable in the slide base SB of the optical pickup PU and form in such a way also a turning point for a tangential or so-called axial tilt T adjustment as illustrated in FIG. 8. The actuator plate AP, which slides on a straight reference surface RS against the counter spring CS for an EF-phase adjustment is therefore provided with a tilt screw TS. The tilt screw TS is arranged opposite to the side, where the actuator plate AP is held by counter spring CS and is slidable kept in a recess R in slide base SB. The recess R, which is formed by a depression in the body of the slide base SB is shown in FIG. 6 and keeps the actuator plate AP moveable on the straight reference surface RS of the slide base SB. As shown in FIG. 8, the actuator plate AP can be caused to undergo positioning respectively with respect to the centre line CL and axial tilt T as the result of the fact that a set of holding arms HA that the actuator plate AP has are engaged with the counter spring CS as shown in FIG. 7. The actuator plate AP is held by the set of holding arms HA so that relative position with respect to the slide base SB is caused to undergo positioning with high accuracy by eccentrically screws ES and tilt screw TS. FIG. 6 illustrates furthermore the arrangement of guide hole GH and support recess SR in slide base SB as generally known and forms in connection with FIG. 3 to FIG. 5 an exploded perspective view showing the construction and elements of an embodiment of an optical pickup PU according to the invention. The optical pickup PU requires a small number of single members as the counter spring CS shown in FIG. 3 and to be mounted with two screws S on the slide base SB shown in FIG. 6 as well as the actuator plate AP shown in FIG. 4 and two eccentrically screws ES shown in FIG. 5 to assemble an optical pickup PU for reading of information from and/or recording of information to a disc.
The proposed arrangement allows less tight tolerances of single members because the actuator plate PL which holds the objective lens OL is adjustable in respect to the guiding hole. GH of the optical pickup PU inside a specific alignment equipment or inside an optical recording or reproducing apparatus, wherein the alignment equipment is formed by the optical pickup PU, which irradiates a light beam to an optical disc inserted into the optical recording or reproducing apparatus and receives a return light from the disc and means for moving the optical pickup PU radially to a spinning optical disc. The optical pickup PU is used to check whether a change of a phase difference in +-first order light received from the disc in case of a movement from the innermost circumference to the outermost circumference of the disc occurs and adjustment with the adjustment means AM moving the actuator plate PL on a straight reference surface RS in the slide base SB is made such that the phase difference between the +-first order light becomes a predetermined value as e.g. 180 degree. That means that the optical pickup PU as a component may be pre-adjusted in a specific alignment equipment similar to an alignment equipment as formed by an optical recording or reproducing apparatus or by using the final optical recording or reproducing apparatus. Finally, the actuator plate AP being fixed after adjusted in position by an adhesive as e.g. an ultraviolet hardening type adhesive agent.
A radial tilt adjustment may be performed in a known manner by an adjustment of the guide shaft GS of the optical drive so that the feed mechanism and the disc rotation drive mechanism are assembled with respect to base unites respectively provided with high accuracy at ideal positions with respect to an adjustment optical disc serving as reference.
The proposed optical pickup PU can be used and configured in numerous different ways, with the result that the field of application and the implementation of the invention are not restricted to the exemplary embodiment specified here.
Patent Application
20080002536
