JP3897014B2 - Optical disc apparatus and tilt angle measuring method - Google Patents

Description

  The present invention relates to an optical disk device, and more particularly to a turntable structure for rotatably supporting an optical disk.

  Conventionally, there has been proposed a rotation support mechanism for an optical disc apparatus that can suppress the vibration of the optical disc as much as possible and record or reproduce data with high quality.

  For example, in the prior art shown below, the turntable is arranged on the upper side so that the label surface of the optical disk is supported by the lower surface of the turntable, and the clamper is moved upward to crimp the center of the optical disk to rotate the optical disk. The structure which supports is disclosed.

  On the other hand, since an optical disk is usually resin-molded, warping occurs due to an external environment such as temperature and humidity. The allowable range of the amount of warpage is defined in the standard of the optical disc, but the amount of warpage varies even within the allowable range, and in addition, optical discs are being supplied to the market from various manufacturers. There are not a few optical discs whose warpage exceeds the allowable range. When such an optical disk is rotatably supported on a turntable by crimping a clamper, a deviation occurs between the optical axis of the laser light from the optical pickup and the normal axis of the optical disk surface due to the amount of warpage, and the recording / reproduction characteristics Adversely affect.

  Therefore, conventionally, a small taper is formed on the lower surface of the turntable, that is, the surface that supports the label surface of the optical disk, from the center to the outer edge, and the optical disk is pressed into the concave shape by making the cross-section into a substantially umbrella-shaped concave shape. To be done. By pressing the central portion of the optical disk into the concave shape of the turntable by the upward moving clamper, the optical disk is corrected to a certain shape along the concave shape, and the warpage of each optical disk is corrected. By adjusting the tilt of the optical axis of the laser beam, that is, the optical axis of the optical pickup that emits the laser beam, to match this correction shape, the laser beam is irradiated almost perpendicularly to the optical disk surface to record or reproduce information. It can be carried out.

Japanese Utility Model Publication No. 4-22437

  However, in the configuration in which a small taper is formed on the lower surface of the turntable to correct the shape of the optical disk, the lower surface of the turntable needs to be tapered, and the cutting machine is basically based on horizontal or vertical processing. The processing is difficult, it is difficult to ensure accuracy, and the cost increases.

  Also, the entire label surface of the optical disk is pressed against the bottom surface of the turntable. For example, when a label or the like is pasted on the label surface of the optical disk, the label adhesive paste protrudes and the optical disk sticks to the bottom surface of the turntable. May end up.

  In addition, a structure in which an air hole is provided in the turntable has been proposed in order to prevent the optical disk from sticking to the turntable due to the vacuum state between the turntable and the optical disk. This causes wind noise, and in particular, DVDs have a problem that wind noise is further increased because the turntable is rotated at high speed.

  Furthermore, in order to make the optical axis of the laser beam substantially perpendicular to the optical disc surface, it is necessary to adjust the optical axis of the laser beam, that is, the optical axis of the optical pickup, but the taper is formed on the lower surface of the turntable. In addition, the glass mirror disk for adjusting the optical axis cannot be mounted on the lower surface of the turntable, and there is a problem that the optical axis using the mirror disk cannot be finely adjusted.

  An object of the present invention is to provide an optical disc apparatus capable of correcting the shape of an optical disc (correcting warpage) without forming a minute taper on the lower surface of the turntable, and also enabling fine adjustment of the optical axis. It is an object of the present invention to provide an optical disk apparatus that performs the above-described process.

  In the present invention, the turntable is arranged on the upper side so as to support the label surface of the optical disk on the lower surface, and is arranged on the lower side so that the clamper is moved upward to crimp the central part on the recording surface side of the optical disk. An optical disc device comprising: a first annular protrusion formed at a position where an outer edge of the optical disc having a first radius contacts the lower surface of the turntable; and a first smaller than the first radius. And a second annular protrusion formed at a position where the outer edge of the optical disk having a radius of 2 abuts, wherein the first annular protrusion protrudes higher than the second annular protrusion. To do.

  When the optical disk having the first radius (for example, 12 cm) is pressed against the lower surface of the turntable by the clamper, the outer edge portion of the optical disk comes into contact with the first annular protrusion. On the other hand, since the central portion of the optical disk is in contact with the lower surface of the turntable on which no taper is formed, the optical disk is straightened and deformed so that the cross-sectional shape becomes an umbrella shape. Thereby, the curvature which each optical disk has is corrected. In addition, when the optical disk having the second radius (for example, 8 cm) is pressed against the lower surface of the turntable by the clamper, the outer edge abuts on the second annular protrusion, and the cross-sectional shape becomes an umbrella shape similarly. It is deformed and corrected.

  In the present invention, it is preferable that a groove having a predetermined width is formed in the first annular protrusion and the second annular protrusion for each predetermined central angle of the turntable. By this groove, a gap is formed between the optical disk and the annular protrusion, allowing air to flow in and facilitating separation of the optical disk from the turntable after pressure bonding (after recording / reproducing). In addition, since it is not formed on the lower surface of the turntable but is formed as a groove of an annular protrusion, the generation of wind noise when the optical disk is rotationally driven is suppressed.

  In the present invention, it is preferable that an inclination angle adjusting hole penetrating the turntable is provided in the groove. It is possible to irradiate laser light from the upper surface to the lower surface of the turntable through this hole, and it is possible to irradiate the mirror disk provided to pass the groove and receive the reflected light It becomes. The reflected laser light reflects the tilt angle of the turntable. For example, the tilt angle of the turntable with respect to the reference surface can be measured by comparing with the reflected laser light with respect to the reference surface.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of an optical disc apparatus 10 in the present embodiment. The optical disk 14 as an information recording medium is, for example, a CD or DVD capable of recording or reproducing information, and is placed in a storage position 16a of a disk tray 16 that goes in and out of a housing (not shown) of the optical disk device 10. In this state, the optical pickup 12 is transported to the operation area. The optical pickup 12 is supported by a pickup base 20 mounted on a base 18 fixed to a housing, and records or reproduces information while moving in the radial direction of the optical disk 14 that has been transported to the operation area. . Information is reproduced by driving a laser diode (LD) in the optical pickup 12 to irradiate the optical disk 14 with a laser beam having a reproduction power, and receiving the reflected light by a photodetector in the optical pickup 12 to generate an electric signal. It is done by converting. Information recording is performed by irradiating the optical disc 14 with a laser beam having a recording power modulated by data to be recorded, forming pits in the recording film of the optical disc 14, or changing the crystal state.

  The optical disc 14 records / reproduces information by rotating at high speed in the operation area of the optical pickup 12. For this reason, it is necessary to fix on the turntable which rotates at high speed. In a general optical disc apparatus, a turntable is provided on a pickup base on which an optical pickup or the like is disposed. However, in this embodiment, as shown in FIG. A turntable 24 is pivotally supported downward. When viewed from the optical disc 14, the turntable 24 is disposed on the upper side. A motor (not shown) is fixed on the bracket 22 to stably rotate the turntable 24 at a high speed.

  On the other hand, an elevating mechanism 28 for elevating a clamper 26 that presses and fixes the optical disk 14 to the bottom surface side of the turntable 24 is disposed on the base 18. The clamper 26 is supported by a shaft 26 a penetrating the pickup base 20, and moves up and down in a state completely separated from the behavior of the pickup base 20, and fixes the optical disk 14 conveyed by the disk tray 16 to the turntable 24. .

  For example, magnets are disposed on the upper surface of the clamper 26 and the center of the back surface of the turntable 24, respectively, and the optical disk 14 is firmly sandwiched between a pair of magnets so that stable high-speed rotation is possible. In the present embodiment, the turntable 24 that rotates at a high speed is substantially separated from the pickup base 20 on which the optical pickup 12 is supported. Therefore, the rotation of the turntable 24 can be prevented from becoming a detection noise of the optical pickup 12.

  The optical pickup 12 performs recording / reproduction of information while seeking in the radial direction of the optical disc 14, and therefore, for example, a guide bar (or guide rail) 30 (only one is shown on the pickup base 20 is shown. A pair of parallel guide bars are preferred) and are moved by a drive mechanism such as a rack and pinion mechanism. At this time, the optical axis of the optical pickup 12 must be arranged so as to coincide with the surface normal of the optical disk 14 supported by the turntable 24 and rotating. If the optical axis and the surface normal do not coincide with each other, it causes a fluctuation component (jitter) in the time axis direction during recording / reproduction and causes a decrease in performance of the optical disc apparatus 10.

  However, the optical pickup 12 is mechanically engaged with the guide bar 30 and the pickup base 20. Therefore, the optical axis and the normal line are inclined depending on the processing accuracy and assembly accuracy of each component. In addition, the optical disk 14 itself is warped or the optical axis of the optical pickup 12 itself is inclined. Due to these various factors, the optical axis and the normal line often do not coincide with each other in the individual optical disk apparatus 10, so that the optical disk apparatus 10 adjusts the optical axis and the normal line for each individual after or during the assembly. Is required. In this case, the inclination between the optical axis and the normal is the inclination in the optical disk radial direction, the inclination in the optical disk tangential direction, and the inclination in the synthesis direction thereof. In the present embodiment, a flexible plate member and a pair of adjustment members are provided in order to correct these inclinations and easily match the optical axis with the normal line. At this time, the inclination correction is realized only by adjusting the pair of adjusting members 34.

  In this embodiment, specifically, as a flexible plate-like member, one end of the pickup base 20 is supported by a plate-like spring member 32 and the other end is a pair of adjustment members, and a base 18 is attached by a screw member 34. It is fixed so that it can move vertically. By rotating either one of the pair of screw members 34 or by rotating them in opposite directions, the pickup base 20 is twisted by the leaf spring member 32 to be directed in the direction of arrow A (directly moving in the direction of movement of the optical pickup 12). The optical axis is adjusted by tilting in the optical disk tangential direction or tangential direction. If the pair of screw members 34 are rotated by the same amount in the same direction, the pickup base 20 is tilted in the direction of arrow B (the optical disk radial direction or radial direction parallel to the moving direction of the optical pickup 12) due to the bending of the leaf spring member 32. The optical axis is adjusted.

  In the present embodiment, the lower surface of the turntable 24, that is, the surface that supports the label surface of the optical disc 14, is not formed with a taper as in the prior art, but is a flat surface. However, an annular protrusion is formed at a predetermined position on the flat surface. The annular protrusion is formed at a position where the outer edge of the annular protrusion abuts when the optical disk 14 is pressed against the lower surface of the turntable 24 by the clamper 26 that moves upward. Since there are a plurality of types of optical discs 14 having different sizes (for example, a 12 cm optical disc and an 8 cm optical disc), an annular protrusion is preferably formed for each type of optical disc 14. In other words, it is desirable to form at a position where the outer edge of the 12 cm optical disk contacts and a position where the outer edge of the 8 cm optical disk contacts.

  Taking a 12 cm optical disk as an example, the optical disk 14 is pressed against the lower surface of the turntable 24 by a clamper 26 that moves upward. The central portion and the inner peripheral portion of the optical disc 14 are in contact with the lower surface of the turntable 24, and the outer edge portion of the optical disc 14 is in contact with the annular protrusion. Therefore, the optical disk 14 is pressed by the turntable 24 with the cross-sectional shape being an umbrella-shaped concave surface, and rotates while the shape is maintained by the rotation of the turntable 24.

  2 is a plan view of the lower surface side of the turntable 24, and FIG. 3 is a cross-sectional view taken along line AA in FIG. A first annular protrusion 24 a and a second annular protrusion 24 b are formed on the lower surface of the turntable 24. The first annular protrusion 24a is formed on the outer edge of the turntable, and the outer edge of the 12 cm optical disk comes into contact therewith. The second annular protrusion 24b is formed on the inner peripheral side with respect to the first annular protrusion 24a, and the outer edge of the 8 cm optical disk contacts. The first annular protrusion 24a is formed higher than the second annular protrusion 24b. For example, the height of the first annular protrusion 24a is set to 1.5 mm, and the height of the second annular protrusion 24b is set to 0.7 mm. The The height of the second annular protrusion 24 b may be set to a height at which the label surface of the 12 cm optical disk comes into contact when the 12 cm optical disk is pressed against the lower surface of the turntable 24 by the clamper 26.

  In the first annular protrusion 24a, four first grooves 24d are formed at predetermined positions, for example, four-fold symmetrical positions having a central angle of 90 ° as shown in the drawing. The first groove 24d forms a gap between the optical disk 14 and the first annular protrusion 24a when the 12cm optical disk 14 comes into contact with the first annular protrusion 24a, thereby allowing air to enter and exit. As an air hole for preventing the optical disk 14 from adhering to the lower surface of the turntable 24. In the conventional turntable, the air hole was formed, but since the conventional air hole was formed by the opening penetrating the turntable, a certain amount of opening area is necessary to prevent a vacuum state. Therefore, when the optical disk 14 is rotated at a high speed, a large wind noise is generated. However, in this embodiment, the groove 24d formed in the annular protrusion 24a is used as an air hole, so an opening is formed directly on the lower surface. Wind noise can be suppressed as compared with the case of doing so. Although the number of the first grooves 24d is arbitrary, it is preferable to form a plurality of first grooves 24d at symmetrical positions around the rotation center of the turntable 24 from the viewpoint of suppressing rotational unbalance due to the eccentric center of gravity of the turntable 24. .

  Similarly, four second grooves 24c are formed in the second annular protrusion 24b at a four-fold symmetrical position with a central angle of 90 °. The second groove 24c functions as an air hole when the 8 cm optical disk 14 is brought into contact with the second annular protrusion 24b. In the figure, the second groove 24 c is arranged so as to be located on the same radiation as the first groove 24 d when viewed from the rotation center of the turntable 24. This is such that when a 12 cm optical disk is mounted, the air passage is on a straight line. The groove widths of the first groove 24d and the second groove 24c are arbitrary, but may be about 2 mm, for example.

  In addition, a plurality of openings 24 e are provided inside the second annular protrusion 24 b of the turntable 24. The opening 24 e is a hole (screw hole) for mounting a weight for adjusting the rotational balance of the turntable 24.

  FIG. 4 shows a state where the 12 cm optical disk 14 is stored in the storage position 16 a of the disk tray 16 and the optical disk 14 is pressed against the lower surface of the turntable 24 by the upper moving clamper 26. FIG. 5 shows the case of the 8 cm optical disk 14. The outer edge of the label surface of the 12 cm optical disk 14 is in contact with the first annular protrusion 24 a, and the central part of the optical disk 14 is in contact with the center of the lower surface of the turntable 24. As a result, the optical disk 14 is corrected to an umbrella shape in cross section, and different warpage is corrected in each optical disk 14. In FIG. 4, the second annular protrusion 24 b is also shown as contacting the label surface of the optical disk 14.

  In the figure, the optical disk 14 has an umbrella-like cross-sectional shape, but the height of the first annular protrusion 24a is only (1.5 mm), and is emphasized for convenience of explanation. Please note that. A gap is formed by the first groove 24d between the 12 cm optical disk 14 and the first annular protrusion 24a, and the optical disk 14 is easily detached from the turntable 24 after recording / reproduction.

  When the 8 cm optical disk 14 is stored in the disk tray 16, the outer edge of the label surface of the 8 cm optical disk 14 is in contact with the second annular protrusion 24 b, and the center portion of the optical disk 14 is in contact with the lower surface center of the turntable 24. As a result, the optical disk 14 is corrected to have an umbrella shape in cross section, and the warp is corrected.

  As described above, in this embodiment, the taper is not formed on the lower surface of the turntable 24, but the 12cm annular protrusion and the 8cm annular protrusion are formed, thereby correcting the shape of the optical disk 14 and varying the amount of warpage. It is possible to prevent the optical axis shift and the recording / reproduction characteristics from deteriorating. Further, by forming the groove in the annular protrusion, the optical disk 14 can be easily detached from the turntable 24.

  In the present embodiment, the optical disk 14 is corrected by the annular protrusions 24a and 24b, but it goes without saying that the optical axis of the optical pickup 12 is adjusted according to the correction. That is, since the correction shape of the optical disk 14 is uniquely calculated from the formation positions and heights of the annular protrusions 24a and 24b, the pair of adjustment members 34 are provided so as to coincide with the surface normal of the corrected optical disk 14. Turn to adjust the optical axis of the optical pickup 12 so that the laser beam from the LD is irradiated onto the surface of the optical disk 14 substantially perpendicularly.

  When adjusting the optical axis, it is desirable to measure the inclination of the turntable 24 and the optical pickup 12 itself. Conventionally, since the lower surface of the turntable 24 is tapered, it is not possible to use a method such as mounting a mirror disk on the turntable 24 and measuring the tilt. Even in the present embodiment, although the annular protrusion is formed on the lower surface of the turntable 24, the portion where the annular protrusion is not formed and the apex portion of the annular protrusion are flat surfaces. Therefore, these flat portions are used. By doing so, it is possible to measure the inclination.

  Hereinafter, a method for measuring an inclination angle (an inclination between the turntable 24 and the optical pickup 12) using the turntable 24 of the present embodiment will be described.

  FIG. 6 shows a plan view of the lower surface side of the turntable 24. The first annular protrusion 24a, the second annular protrusion 24b, the first groove 24d, and the second groove 24c are provided, and an opening 24f that penetrates the turntable 24 is formed in the first groove 24d. . This opening is an opening through which the condensed laser beam is transmitted, and functions as a tilt adjusting hole. The opening 24f may be formed in all of the four first grooves 24d as illustrated, or may be formed only in any one of the grooves 24d. An annular mirror disk substantially equal to the width of the first annular protrusion 24a is prepared, and the annular mirror disk is mounted in contact with the first annular protrusion 24a. The annular mirror disk is mounted so as to cross at least the first groove 24d in which the opening 24f is formed. Although various mounting methods are conceivable, a mounting screw may be provided on the mirror disk, and a screw hole may be provided on the turntable.

  FIG. 7 shows a method of measuring the tilt angle. As described above, the annular mirror disk 100 is mounted on the first annular protrusion 24a. Tilt measuring transmitters / receivers 40 and 42 whose relative positions are known are arranged above the arch bracket 22, and the laser light from the transmitter / receiver 40 is covered by the arch bracket 22 in the turntable 24. The incident light enters the part that does not exist and enters the opening 24 f that penetrates the turntable 24. In the first groove 24d in which the opening 24f is formed, an annular mirror disk 100 (a part of the annular shape is shown in the figure) is placed horizontally, so that the laser light incident on the opening 24f is The light is reflected by the mirror disk and enters the light transmitter / receiver 40.

  On the other hand, the laser light from the light transmitter / receiver 42 (adjusted so as to be parallel to the laser light from the light transmitter / receiver 40) is horizontally mounted on a pair of guide bars with a parallelism. Is reflected by the mirror 102 and enters the light transmitter / receiver 42. Since the two laser beams are parallel, the difference in the optical axis of the incident light in the light transmitter / receiver 40, 42 depends on the amount of tilt between the mirror disk 100 and the mirror 102. The optical pickup 12 is supported by a pair of guide bars 30, and a rack fixed to the package of the optical pickup 12 is driven by the rotation of a pinion gear provided on the pickup base 20 side and slides along the guide bars 30. Since the optical axis of the optical pickup 12 and the guide bar 30 are in a fixed relationship, the optical axis of the incident light from the light transmitters / receivers 40 and 42 is supplied to the tilt sensor 50, and the tilt sensor 50 By converting the difference of the incident optical axis into the tilt angle, the tilt between the turntable 24 and the optical pickup 12 can be measured.

  After the tilt angle between the turntable 24 and the optical pickup 12 is measured as described above, the pickup base 20 may be tilted so that the tilt is compensated by the pair of adjusting members 34.

  The mirror disk 100 may be only a part of the ring, not the ring.

In FIG. 7, the light transmitter / receivers 40 and 42 are provided separately. However, a single LD and two photodetectors are provided, and the laser light from the single LD is dispersed to mirror the disk 100 and the mirror 102. The reflected light may be received by a photodetector. The tilt angle adjustment method is summarized as follows.
(1) The mirror disk 100 is mounted on the first annular protrusion 24a. (2) The mirror 102 is installed on the pair of guide bars 30. (4) Compare the reflected light optical axis and detect the tilt between the normal axis of the turntable and the optical axis of the optical pickup. (5) Adjust the optical axis of the optical pickup according to the tilt of the turntable and the optical pickup.

  In (1) above, if the second groove 24c is also provided with an opening penetrating the turntable 24, the mirror disk can be mounted on the second annular protrusion 24b.

  In this way, by providing the opening 24f that is a hole for adjusting the tilt angle, tilt angle measurement using a mirror disk becomes possible, and tilt angle measurement by laser light irradiation from the upper surface side (bracket 22 side) of the turntable 24 is possible. Is possible.

It is a block diagram of an optical disk device. It is a top view of a turntable. It is AA sectional drawing of FIG. It is correction deformation explanatory drawing of a 12 cm optical disk. It is correction deformation explanatory drawing of an 8 cm optical disk. It is a top view of another turntable. It is explanatory drawing which shows a tilt angle measuring method.

Explanation of symbols

  10 optical disk device, 12 optical pickup, 14 optical disk, 16 disk tray, 18 base, 20 pickup base, 22 bracket, 24 turntable, 24a first annular protrusion, 24b second annular protrusion, 24c second groove, 24d 1st groove | channel, 24f opening, 26 clamper, 30 guide bar, 32 leaf | plate spring member, 34 screw member (adjustment member).

Claims (4)

An optical disc apparatus in which a turntable is arranged on the upper side so as to support the label surface of the optical disc on its lower surface, and is arranged on the lower side so that the clamper is moved upward and the central portion on the recording surface side of the optical disc is crimped Because
On the lower surface of the turntable,
A first annular protrusion formed at a position where the outer edge of the optical disc having a first radius contacts;
A second annular protrusion formed at a position where an outer edge of the optical disc having a second radius smaller than the first radius contacts;
The optical disk device is characterized in that the first annular protrusion protrudes higher than the second annular protrusion. The apparatus of claim 1.
A groove having a predetermined width is formed in each of the first annular protrusion and the second annular protrusion for each predetermined center angle of the turntable. The apparatus of claim 2.
An optical disc apparatus characterized in that a tilt angle adjusting hole penetrating the turntable is provided in the groove. A tilt angle measuring method using the optical disc device according to claim 3,
Irradiate the laser beam through the tilt adjustment hole from the irradiation device provided on the upper surface side of the turntable,
The laser beam is reflected by a mirror disk mounted on the annular protrusion,
The tilt angle of the turntable is detected with respect to the reference plane by comparing the optical axis of the laser beam reflected by the mirror disk with the optical axis of the laser beam reflected by the reference plane of the optical disc apparatus. Measurement method.

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