JPH0533315U - Moving device for optical pickup - Google Patents

Abstract

(57) [Abstract] [Purpose] To enable tracking error detection by a three-beam method in a player that moves a pickup by a swing arm method. [Structure] Pickup moving device 11 of CD player
Is a pickup 12 for reading a signal and detecting a tracking error by the 3-beam method, and a free end portion 13.
a swing arm 13 to which the pickup 12 is rotatably attached and a support end portion 13a is rotatably supported; It is composed of a sliding arm 14 provided with 15 and a guide surface 16a on which the roller 15 rolls. When the swing arm 13 rotates to move the pickup 12, the guide surface 16a
The angular posture of the pickup 12 is changed depending on the shape, so that the three beam spots are properly oriented to the tracks T1, T2, etc.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a pickup moving device for reading a signal and detecting a tracking error by a three-beam method, and more particularly to a pickup moving device for rotating a swing arm around a fulcrum to move the pickup along a recording medium. Regarding

[0002]

[Prior Art]

 The three-beam method is used as a tracking servo method in an optical disk device such as a CD player. In this three-beam method, light from a light-emitting element provided in the pickup is diffracted by a diffraction grating, and as shown in FIG. 9, a main beam spot L0 and two tracking error detection tracks are formed on the recording surface of the disc. The sub beam spots L1 and L2 are formed. 9A shows a state in which the main beam spot L0 is displaced in the upward direction in the figure with respect to the track T (tracking error state), and FIG. 9B shows a state in which the main beam spot L0 is located on the track T. FIG. 9C shows a state in which the main beam spot L0 is deviated from the track T in the downward direction in the drawing.

The reflected return light from each of the spots L0 and L1 and L2 is received by the light receiving element of the pickup. At this time, the difference in the received light amount of the return light from the sub beam spots L1 and L2 should be obtained. By this, the tracking error amount and its error direction are detected, and tracking servo is performed based on this error detection output. Since the three-beam method is less affected by the deviation of the optical axis of the optical system and has good servo stability, many pickups using this method are adopted. Further, the moving device for moving the pickup along the recording surface of the disc has two typical structures depending on the moving method.

FIG. 7 is a schematic plan view showing an example of a moving device of a system for moving a pickup in parallel, and FIG. 8 is a schematic plan view showing a moving device of a system for turning a pickup. The moving device of the pickup shown in FIG. 7 has slide shafts 1 and 2 arranged in parallel to slidably support the pickup 3 on the slide shafts 1 and 2, and has a rack mechanism or a feed screw mechanism (not shown). The pickup 3 is moved in parallel by the moving mechanism to move the pickup 3 along the recording surface of the disc D to reproduce the recorded information.

The pickup moving device shown in FIG. 8 has a swing arm 4 to which a pickup 3 is attached on the free end side and the other end is supported rotatably around a fulcrum P. Is rotated by a moving mechanism such as a magnetic drive mechanism to move the pickup 3 along the recording surface of the disk D to reproduce recorded information.

[0006]

[Problems to be solved by the device]

 However, in the parallel movement type pickup moving device shown in FIG. 7, since the pickup 3 is moved along the slide shafts 1 and 2 by a rack mechanism, a feed screw mechanism, etc. It has the drawback that it cannot operate quickly. In order to move the pickup 3 straight in the radial direction of the disc D, the parallelism between the slide shafts 1 and 2 and the horizontalness between the slide shafts 1 and 2 must be ensured with high accuracy. The mechanism becomes complicated. Further, there is a drawback that sliding friction resistance occurs between the support portions 3a and 3b of the pickup 3 and the slide shafts 1 and 2, and the load of the feed motor of the pickup increases.

On the other hand, in the swing arm type pickup moving device shown in FIG. 8, the pickup 3 can be accessed at high speed and there is no problem such as sliding friction with the slide shaft, as compared with the parallel moving type. , Is excellent in that respect.

However, this swing arm method has a drawback that the tracking servo by the above-described three-beam method cannot function. That is, in the three-beam tracking servo method shown in FIG. 9, the center reference line O, which passes through the main beam spot L0 and has the sub-beam spots L1 and L2 evenly located on both sides, is tangential to the recording track of the disk D. You must always turn. However, in the swing arm method shown in FIG. 8, since the objective lens draws an arc locus when the pickup 3 turns, the direction of the center reference line O shown in FIG. May not face tangentially to the track T. In this case, although the main beam spot L0 is in the on-track state, one of the sub-beam spots L1 or L2 may hit the track T, resulting in an offset in the detection of the tracking error signal. Therefore, until now, when the swing arm type pickup moving mechanism shown in FIG. 8 is adopted, the three-beam type tracking servo method cannot be used.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a pick-up moving device that adopts a swing arm method and is capable of detecting a tracking error of a three-beam method. It is a thing.

[0010]

[Means for Solving the Problems]

 The pickup moving device according to the present invention includes a pickup for reading signals and detecting tracking errors by a three-beam method, and a pickup end rotatably attached to a free end and a rotatably supported end portion. A swing arm, a sliding member whose one end is fixed to the pickup, and a guide unit that guides the sliding member, wherein the guide unit is provided when the swing arm rotates. It is characterized in that it has a shape that guides the posture of the pickup so that the facing posture between the pickup and the recording track of the recording medium is always constant.

[0011]

[Action]

 According to the above means, the swing arm swings so that the pickup provided at the free end of the swing arm moves along the recording medium. At this time, the sliding member fixed to the pickup is guided by the guide portion. Due to the shape of the guide portion, the pickup is always rotated with respect to the free end portion of the swing arm so that the facing attitude between the pickup and the track of the recording medium is always constant. As a result, when the pickup moves along the recording medium, the spot of the three beams emitted from the pickup is always directed to the proper direction with respect to the track, and the tracking error can be reliably detected by the three beam spot. Like

[0012]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a pickup moving device for a CD player according to an embodiment of the present invention, FIG. 2 is a view in the direction of arrow A in FIG. 1 (bottom view), and FIG. 3 is a partial sectional view of FIG. 4 to 6 are views for explaining the operation of the pickup moving device of the CD player according to the embodiment of the present invention. In the pickup moving device 11 of the CD player shown in FIG. 1, reference numeral 12 is an optical pickup, and an objective lens 12b provided on the upper surface thereof faces the recording surface of the disk D. Inside the optical pickup 12, a semiconductor laser as a light emitting element, a pin photodiode as a light receiving element, and various optical parts such as a collimating lens are incorporated. A light separating element such as a diffraction grating is provided in the light emission path from the semiconductor laser, and the laser beam is focused on the recording surface of the disc D from the objective lens 12b, so that the recording surface of the disc D is shown in FIG. Similarly, three beams of the main beam spot L0 and the sub beam spots L1 and L2 are formed. A focus actuator is provided in the pickup 12, and the focus actuator performs a correction operation so that the focus position of the beam spot focused by the objective lens 12b always coincides with the recording surface of the disc D. ..

The pickup 12 is rotatably supported on the free end portion 13b of the swing arm 13 by a rotation shaft 12a arranged concentrically with the center of gravity of the pickup 12 and the center of the objective lens 12b on the lower side thereof. (See FIGS. 2 and 3). The support end 13a of the swing arm 13 is rotatably supported by a support shaft 13c provided on a pickup chassis (not shown). In addition, a spring-hanging protruding piece 13e is integrally formed on a side portion of the swing arm 13. Then, the swing arm 13 is rotatably driven by the moving means 17 about the support shaft 13c. As shown by the chain double-dashed line in FIG. 4, the swing arm 13 is extended on the side of the support end 13a, and a weight 13d for balancing the weight of the pickup 12 is attached to the tip of the support end 13a. However, the pickup 12 may be prevented from swinging. The moving means 17 is, for example, a linear motor, and in the case of this linear motor, a coil is mounted on the swing arm 13 and a magnet facing the coil is provided on the pickup chassis side. By swinging the swing arm 13 by the linear motor, the pickup 12 follows the track of the disc D and is normally fed from the inner diameter side of the disc D to the outer diameter side thereof, and is further moved at a high speed to bend. Access operations such as detection are performed. The linear motor drives the pickup 12 for tracking correction based on a tracking error detection signal due to the three beam spots. Note that the tracking correction operation does not necessarily have to be performed by the moving means 17, and, for example, an actuator for tracking correction is provided in the pickup 12, and the moving means 17 moves from the disk inner diameter side of the pickup 12 to the outer diameter direction. It is also possible to perform only the sending operation to and the high speed access operation. Further, the moving means 17 may be not only a linear motor but also a feed drive device using an ordinary motor and a reduction gear.

One end 14 b of a sliding arm (sliding member) 14 is integrally fixed to the pickup 12. The other end 14 a of the sliding arm 14 is provided with a rotatable roller 15. Further, a spring 18 is stretched between the sliding arm 14 and the projecting piece 13e of the swing arm 13, and the other end 14a of the sliding arm 14 including the roller 15 is extended by the spring 18. It is biased in the arrow X direction in 1.

Reference numeral 16 is a cam member fixed to the pickup chassis or formed on the pickup chassis itself. A guide surface 16a on which the roller 15 rolls is formed on the cam member 16. The guide surface 16a is composed of a flat portion 16c, a curved surface portion 16b, etc., and the roller 15 provided on the sliding arm 14 which is biased by the spring 18 in accordance with the swing arm 13 pivoting. By rolling on the surface 16a and the guiding operation of the guide surface 16a, the angular posture of the pickup rotatably supported by the swing arm 13 can be changed at any time. The guide surface 16a has a shape in which the pickup 12 that moves along the recording surface of the disc D and the recording tracks (illustrated by T1, T2, etc.) on the recording surface of the disc D always face each other at a constant posture as described later. Is formed.

Next, the operation of the pickup moving device 11 of the CD player having the above configuration will be described with reference to FIGS. 4 to 6. To explain this operation, FIGS. 4 and 5 show three beams focused on the recording surface of the disk D by the objective lens 12b, and the main beam spot is L 0 and each sub beam spot is L1 and L2. Further, as in the case described with reference to FIG. 9, a central reference line that passes through the main beam spot L0 and on which the sub-beam spots L1 and L2 are equally positioned on both sides thereof is indicated by O.

In the reproducing operation of the CD player, as shown in FIG. 4, FIG. 5, and FIG. 6 in order, the swing arm 13 is driven by the moving means 17 in the counterclockwise direction in the drawing with the support shaft 13c as a fulcrum, and the pickup 12 is moved. Are gradually fed from the inner diameter side of the disc D to the outer diameter side. Therefore, when the swing arm 13 is driven and the pickup 12 moves, the movement locus of the object lens 12b becomes an arc locus around the support shaft 13c of the swing arm 13. Further, while the pickup 12 moves along the arc locus, the roller 15 rolls on the curved surface portion 16b of the guide surface 16a of the cam member 16, and the angular posture of the pickup 12 changes according to the movement position of the pick-up 12. be changed.

As a result, for example, when the pickup 12 is located on the inner diameter side of the disc D as shown in FIG. 4, that is, when the main beam spot L0 scans an arbitrary track T1 on the recording surface of the disc D, The center reference line O is oriented at right angles to the radial line R1 from the disk center Od. Further, as shown in FIG. 5, when the pick-up 12 is located substantially in the center of the recording area of the disk D, that is, when the main beam spot L0 scans an arbitrary track T2 on the recording surface of the disk D. Now, the center reference line O is oriented at right angles to the radial line R2 from the disc center Od. This is the same for each track on the recording surface.

Therefore, the center reference line O, which serves as a reference for the main beam spot L0 and the sub-beam spots L1 and L2, always faces in the tangential direction with respect to each track, so that the sub-beam spots L1 and L2 are tangential to the tracks. The tracking error signal of the main beam spot L0 can be accurately obtained by obtaining the difference in the detected light amount of the return light from each of the sub-beam spots L1 and L2 which are equally distributed.

Based on the above tracking error signal, the swing arm 13 is finely driven by the linear motor that is the moving means 17, or the objective lens 12b is finely driven by the tracking actuator provided in the pickup 12. Then, the tracking correction operation is performed so that the main beam spot L0 is always on track.

As shown in FIG. 6, when the pickup 12 is separated from the recording area of the disk D toward the outer peripheral side, the roller 15 moves to the flat portion 16c of the guide surface 16a. The series of operations described above is similarly performed in all tracks on the disk D, and also in the high speed access mode.

As described above in detail, according to the above-described embodiment, since the pickup moving mechanism by the swing arm is used and the tracking error detection operation of the three-beam method can be performed, the high-speed access which is an advantage of using the swing arm method. It has excellent performance, can reduce the load of pickup feed driving force, and can accurately detect tracking errors using the 3-beam method. The present invention is not limited to the above-described embodiment. For example, a pin protruding from the lower surface or the upper surface of the pickup 12 is provided, and the pin is slid in a guide groove formed in the pickup chassis to move the pickup. The moving posture may be changed at any time. Further, the present invention is not limited to the CD player, but can be implemented in various optical disk devices such as a laser disk player and a magneto-optical disk player.

[0023]

[Effect of the device]

 As described above, according to the present invention, a swing arm type pickup feed mechanism is adopted to enable high-speed access, the load of the pickup feed mechanism can be reduced, and tracking error is detected by the tracking error detection of the three-beam method. The detection can be performed easily and with high accuracy.

[Brief description of drawings]

FIG. 1 is a perspective view showing a pickup moving device of a CD player according to an embodiment of the present invention.

FIG. 2 is a view (bottom view) viewed in the direction of arrow A in FIG.

3 is a view in the direction of arrow B having a partial cross section in FIG. 1. FIG.

FIG. 4 is an operation explanatory diagram of a pickup moving device of a CD player according to an embodiment of the present invention.

FIG. 5 is an operation explanatory view of the pickup moving device of the CD player according to the embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of a pickup moving device of a CD player according to an embodiment of the present invention.

FIG. 7 is a schematic plan view showing an example of a moving device that moves a pickup in parallel.

FIG. 8 is a schematic plan view showing a moving device of a type in which a pickup is rotated.

9A and 9B are explanatory views showing a three-beam method among tracking error detection methods, in which FIGS. 9A and 9C show a state in which a tracking error occurs, and FIG. 9B shows an on-track state.

[Explanation of symbols]

 11 Pickup Moving Device of CD Player 12 Pickup 12a Rotating Shaft 12b Objective Lens 13 Swing Arm 14 Sliding Arm 15 Roller 16 Cam Member 16a Guide Surface D Disc T Track L0 Main Beam Spot L1, L2 Sub Beam Spot

Claims (1)

[Scope of utility model registration request] 1. A pickup for reading a signal and detecting a tracking error by a three-beam method; a swing arm having the free end rotatably attached to the pickup and the other end rotatably supported. A slide member having one end fixed to the pickup, and a guide portion for guiding the slide member, wherein the guide portion is
An optical pickup moving device having a shape that guides the posture of the pickup such that the facing posture of the pickup and a recording track of a recording medium is always constant when the swing arm rotates.