JPH01151025A - Skew correcting device for disk player - Google Patents

Abstract

PURPOSE:To always correctly read the information recorded at a disk by gearing a moving rack through a pinion to a fixed rack, and on the otherhand, linking a skew correcting means to sway the moving rack in an optical pick-up focus direction with the supporting shaft of the pinion as a center to the moving rack. CONSTITUTION:An optical pick-up 5 is fixed to a moving rack 8 to move in the radial direction of a disk and the moving rack 8 is geared through pinions 10, 11 and 13 to a fixed rack 18. On the other hand, a skew correcting means 19 to sway the moving rack 8 in the focus direction of the pick-up 5 with the supporting shaft of the pinions 10, 11 and 13 as a center is linked to the moving rack 8. Consequently, the distance change of the focus direction of the optical pick-up 5 due to the warp, etc., of the disk D is cancelled, the distance between the optical pick-up 5 and the disk D can be always kept constant, and the light flux from the optical pick-up 5 can be always vertically abutted to the signal surface of the disk D. Thus, the signal recorded to the disk can be correctly read.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a disc that corrects the skew in the focus direction of an optical pickup in a disc player that plays discs such as laser vision discs (LD) and compact discs (CD). The present invention relates to a skew correction device for a player.

[Summary of the Invention] The present invention provides a skew correction device for a disc player, in which an optical pickup is fixed to a movable rack that moves in the radial direction of the disc, and this movable rack is engaged with a fixed rack via a pinion, while the pinion By linking to the movable rack a skew correction means that swings (rotates) the movable rack in the focus direction of the optical pickup around the spindle of the disk, the distance in the focus direction of the optical pickup caused by warping of the disk, etc. By canceling the change, keeping the distance between the optical pickup and the disk constant, and always shining the light beam from the optical pickup perpendicularly to the disk,
This allows the signals recorded on the disc to be read accurately.

[Prior Art] For example, when playing a laser vision disc (LD) with a laser vision disc player, in order to accurately read the signals recorded on the disc, a laser beam from an optical pickup is directed against the disc. It must always be applied vertically. If the disc is warped and the laser beam hits the signal surface of the disc obliquely, the focal point of the laser beam will spread into an ellipse, and the image quality will deteriorate due to crosstalk. This is called skew, and a skew correction device that detects the inclination of the disk surface with respect to the optical axis using a sensor and adjusts the angle of the optical axis of the optical pickup accordingly is disclosed in, for example, Japanese Utility Model Application Publication No. 155017/1983. ing.

This will be explained with reference to a schematic side view showing the operating principle of the skew correction device in FIG.
is a moving base 32 that moves in the radial direction of the disk D along the guide rail 31 by a moving mechanism (not shown).
exists. An optical pickup 33 is supported on this base 32 so as to be rotatable in the focusing direction of the optical pickup 33 about a rotating shaft 35 . When the disk D is warped upward, for example, the optical pickup 33 rotates in the direction of the arrow in the figure around the rotating shaft 35 that is variable (displaced) in the radial direction of the disk D, and The light beam (laser beam) C from the objective lens 34 of the optical pickup 33 is always directed perpendicularly and condensed.

In the skew correction device 30 of the disk player, the optical pickup 33 is rotated to follow the warpage of the disk D, so that the light beam C is directed toward the disk D.
can be applied vertically, but the distance A between the disk D and the objective lens 3/1 of the optical pickup 33 (distance in the focus direction of the optical pickup 33) is kept constant from the inner circumference to the outer circumference of the disk D. I can't do it,
The distance change in the focus direction becomes larger toward the outer circumference of the disk D.

To cope with this problem, a skew correction device 40 for a disc player shown in FIG. 5 has been devised.

This skew correction device 40 supports a guide rail 41 so as to be able to swing (rotate) in the vertical (focus) direction on the disk D side around a rotation shaft 45.
The optical pickup 43 is moved along the radial direction of the disk D by a moving mechanism (not shown). Then, the guide rail 41 is rotated around the rotating shaft 45 in the direction of the arrow in the figure along the warp of the disk D,
To read the signal recorded on the disk D by applying the light beam C from the objective lens 44 of the optical pickup 43 perpendicularly to the disk D and keeping the distance B between the optical pickup 43 and the disk D close to a constant value. is now possible.

[Problems to be Solved by the Invention] However, in the skew correction device 40, the rotating shaft 45 that swings the guide rail 41 is connected to the spindle motor 4.
Distance B between the disk D and the optical pickup 43
1. In particular, there was a drawback that the distance in the focus direction between the outer circumferential side of the disk D and the optical pickup 43 could not be maintained at a constant value (constant distance) in accordance with the warpage of the disk D.

Therefore, the present invention makes it possible to always keep the distance in the focus direction between the disk and the optical pickup at a constant value regardless of the deformation state of the disk, and to always apply the light beam from the optical pickup perpendicularly to the signal surface of the disk. The present invention provides a skew correction device for a disc player that can perform the following steps.

[Means for solving the problem] An optical pickup for reading information on a disc is fixed to a movable rack that moves in the radial direction of the disc, and this movable rack is engaged with the fixed rack via a pinion, while the pinion A skew correction means for swinging the movable rack in the focus direction of the optical pickup about the support shaft is linked to the movable rack.

"Operation" The skew correction means causes the optical pickup to swing around the spindle of the pinion so as to keep the distance from the disk constant. As a result, the distance in the focus direction of the optical pickup is always corrected to a constant value, and the light beam from the optical pickup always hits the disk perpendicularly. Therefore, the information recorded on the disc can always be accurately read by the optical pickup.

[Example] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, I is a skew correction device for, for example, a laser vision disc player, and has a rectangular box frame-shaped transport body 2 with an open top side. A guide shaft 3 is installed above the left and right sides of the transfer body 2 in the figure. Also, the front of the transport body 2 in the figure.

A rotary shaft 4 as a supporting shaft is rotatably supported at the lower part of the rear side so as to be orthogonal to the guide shaft 3.

The guide shaft 3 supports an optical pickup 5 so as to be movable back and forth. On the top surface of this optical pickup 5, a laser beam is connected to a laser vision disk (LD).
An objective lens 6, etc. that irradiates and focuses light on the bit of the disk D and detects the reflected light from the bit surface to read information, and a detection light that detects the inclination due to warpage of the disk D with respect to the optical axis. It has a skew lens 7 as a skew sensor that illuminates the disk surface.

On one side of the optical pickup 5, the guide shaft 3
The movable rack 8 is fixed with screws 9 or the like so as to be parallel to the movable rack 8. This movable rack 8 meshes with a small-diameter pin-on 10 fixed to the middle of the rotating shaft 4. Both ends of the rotating shaft 4 protrude through both front and rear pieces of the movable body 2, and a large diameter pin-on 11 is attached to the protrusion on one side of the front side in the figure.
A large-diameter driven pulley 12 and a large-diameter pin-on 13 are respectively fixed to the protrusion on one side of the rear side in the figure.

Also, inside the rear piece of the movable body 2, a forward/reverse motor 14 is provided.
is arranged on the rotating shaft of this motor 14,
A belt 16 is stretched between the drive pulley 15 protruding to the outside of the rear piece of the movable body 2 and the driven pulley 12. Further, a horizontal piece 17 serving as a cam follower is bent and formed on the upper outer side of the rear piece of the movable body 2.

The pair of large-diameter pulleys 11 and 13 mesh with a fixed rack I8 fixed to the bottom (neither is shown) of the player body of the laser vision disc player. Thereby, the rotation of the motor 4 rotates the rotary shaft 4, and the optical pickup 5 moves back and forth. Further, the horizontal piece I7 of the movable body 2 is slidably placed on the cam surface 19a of the cam 19 as a skew correction means. The contour of this cam surface 19a is formed into a spiral line shape centered on the rotating shaft 20 of the forward/reverse motor that rotatably supports the cam I9. The spiral cam surface 19a allows the movable body 2 to swing about the rotating shaft 4 in the focus direction of the optical pickup 5. Incidentally, the forward/reverse motor of the rotating shaft 20 is fixed to the bottom surface of the player main body.

According to the skew correction device l for a laser vision disc player of the above embodiment, the motor! 4 rotates the drive pulley 15 in the direction of the arrow in FIG. 1, the rotating shaft 4 rotates in the direction of the arrow in the figure via the driven pulley 12,
The pair of large-diameter pinions 11, 13 and the fixed rack 18 move the transport body 2 in the radial direction of the disk D indicated by the arrow in the figure.

For example, when the moving body 2, that is, the rotating shaft 4, moves by a distance (L) in the radial direction of the disk D, the moving rack 5, that is, the optical pickup 5 moves through the small diameter pinion 10 fixed to the rotating shaft 4. Twice the distance of 4! (2L) Move in the radial direction of the disk D in the same direction as the moving body 2.

If the disk D has a downward curvature, for example, the skew lens 7 detects the inclination of the disk surface with respect to the optical axis of the optical pickup 5, and the rotation axis 20 of the motor is moved in the direction of the arrow in FIG. The transfer body 2, that is, the optical pickup 5 is rotated (swinged) via the cam 19 about the rotation shaft 4 in the downward focus direction of the disk D (in the direction shown by the dashed-dotted arrow in FIG. 2). ). In this way, the rotating shaft 4 is freely movable (variable) in the radial direction of the disk D, and the movable rack 8, that is, the optical pickup 5 is swingable about the rotating shaft 4 in the focusing direction of the optical pickup 5. Therefore, the distance change in the focus direction of the optical pickup 5 due to the warping of the disk D is canceled, the distance between the optical pickup 5 and the disk D is always maintained at a constant value, and the distance between the optical pickup 5 and the disk D is always kept constant.
The information recorded on the disk D can be read accurately by always applying the light beam from the objective lens 6 of the optical pickup 5 perpendicularly to the signal surface of the disk D.

Next, as shown in FIG. 3, the skew correction values of the skew correction device 1 of the present invention and the conventional skew correction device 30° 40 when the disk D is warped by, for example, ±2 mm are determined by specific numerical values. Show and compare.

First, an expression expressing the shape of the disk D and an expression expressing the change in the distance between the disk D and the optical pickup in the focus direction are determined.

It has been found through measurements that the shape of the disk D can be approximated by the inclination being proportional to the radius (from the clamp section 21).

Therefore, if the distortion of the disk D is y, the radius of the clamp part 21 of the disk D is r0, and the radius of the disk D is r, then dy/dr is dy/dr= A (r - ro), and by integrating this, y=1 It is given by /2Ar'-Aror+B.

Here, as an example, if ro = 22.5 mm and the distortion at the outermost circumference (r = 150 mm) is 2 mm, then y = f (r) = -0,000123r2 + 0.00554r -
0,0623...■.

The distance change between the disk D and the optical pickup (the distance change in the focus direction of the optical pickup) is as follows: The deflection of the disk D is y=f(r) The inclination of the disk D is f' (r) The center of the bottom surface of the disk D is (0, 0) If the rotation axis of the skew correction device is (XO, YO) distance change in the focus direction δ, then δ=1/1+f” (r) ((f” (r) f(r)
-f'(r)Yo+["'(r)Xo-f"'(
r) r) 2+(f' (r)roYo-f” (r)X
o−f(r))' )...■ It is given by.

Here, if we express Xo and Yo at the rotation axis 35.45 of the conventional skew correction device 30° 40, in the skew correction device 30, Xo=r-23y, =-10 In the skew correction device 40, Xo=85 Y, = -12,9 (the best position for this device).

If the disc D is warped by ±2 mm using formulas ① and ②, the distance change in the focus direction of the optical pickup δ
It was found that with the conventional skew correction device 30, +0.41 mm -0.42 mm, a total change of 2.4 mm, with the conventional skew correction device 40, of +0.41 mm -0.42 mm, a total change of 0.83 mm.

Further, in the skew correction device l of the present invention, the set position of the rotation axis 4 of the optical pickup 5 is xo=r/2+13
When set so that Yo=I 2.9, the distance change δ in the focus direction of the optical pickup 5 when the warp of the disk D is ±2 mm is +0.01 mm -0.05 mm, totaling 0.06 mm. Therefore, it has been found that the distance change δ of the optical pickup 5 in the focus direction is practically zero.

Although the skew correction device for a laser vision disc player has been described in the above embodiment, it is of course applicable to a compact disc player.

[Effects of the Invention] As described above, according to the present invention, an optical pickup is fixed to a movable rack that moves in the radial direction of the disk,
The movable rack is engaged with the fixed rack via a pinion, and a skew correction means for swinging the movable rack in the focusing direction of the optical pickup about the spindle of the pinion is linked to the movable rack. It is possible to cancel distance changes in the focus direction of the optical pickup due to warpage, etc., and keep the distance between the optical pickup and the disk constant at all times, and the light beam from the optical pickup is always directed perpendicularly to the signal surface of the disk. This allows the signals recorded on the disc to be read accurately.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a skew correction device for a disc player showing an embodiment of the present invention, Fig. 2 is a schematic side view showing the operating principle of the skew correction device, and Fig. 3 is a schematic comparison of skew correction states. FIG. 4 is a schematic side view showing the operating principle of a conventional skew correction device, and FIG. 5 is a schematic side view showing the operating principle of another conventional skew correction device. l... Skew correction device for disk player, 4...
・Rotating shaft (support shaft), 5... Optical pickup, 8...
- Mobile rack, 10. If, +3...Fixed rack, 1
9...Cam (skew correction means), D...Disk. Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] An optical pickup for reading information on a disc is fixed to a movable rack that moves in the radial direction of the disc, and this movable rack is engaged with a fixed rack via a pinion, while the movable rack is optically moved around the spindle of the pinion. A skew correction device for a disk player, characterized in that a skew correction means for swinging a pickup in a focus direction is linked to the movable rack.