JPH02278523A - Optical disk device - Google Patents

Abstract

PURPOSE:To eliminate a tracking error generated by turning by making a dividing line in the tracking direction of an optical system, especially, optical detector in a pickup part coincident with the tangential direction of each information track in any positions on an optical disk surface. CONSTITUTION:Deviation in the tangential direction, which is generated with the displacement of a pickup 3, between the optical system of the pickup 3 and each information track is corrected by changing an angle formed by an arm 2 and pickup 3 by a guide member 13. Then, the dividing line direction of the optical system, especially, of the optical detector in the pickup 3 is always made coincident with the tangential direction of each information track. Thus, stable tracking servo can be applied from the inner-most circumference to outer-most circumference track of an optical disk and further, the lengths of the arm 2 and guide member 13 can be shortened more than the conventional lengths. Then, the optical disk can be made compact and operation is profitable for high-speed access or improving the rotational speed of the optical disk.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a swing arm type optical disc device (optical information recording/reproducing device).

[Conventional technology]

FIG. 5(a) is a plan view showing an example of the configuration of an optical disc device using a conventional swing arm system. In this device, a pickup 3 is attached to one end of an arm 2 that can rotate around a rotation axis 1, and a linear motor 4 is configured at the other end of the arm 2, and the arm 2 is rotated by this linear motor 4. The pickup 3 is moved in the radial direction with respect to the optical disk rotating in a predetermined direction. The pickup 3 has a light source 6, a collimator lens 7, a beam splinter 8, an objective lens 9, an error detection optical system 10, and a photodetector 11, as shown in a partial cross section in FIG. The laser beam emitted from the laser beam passes through the collimator lens 7, the beam splitter 8, and the objective lens 9, and is irradiated onto the optical disk 5 in the form of a spot. The objective lens 9 is configured to be guided to the detector 11, and the objective lens 9 is attached to the main body of the pickup 3 so that it can be slightly displaced in the two-dimensional direction of the optical axis and the radial direction of the optical disc 5 by a focusing mechanism and a trunking mechanism. ing.

[Problem to be solved by the invention]

In the conventional device, when the swing arm 2 is used to displace the pickup 3 in the radial direction of the optical disc, the trajectory of the objective lens becomes an arc with respect to the radial direction of the optical disc, so information on the trajectory of the objective lens is The tangential directions of the tracks were different for each track. For example, as shown in FIG. 6(a), when an objective lens draws an arcuate trajectory centered on a point P on an optical disk rotating with a point O as its center of rotation, an information track on the trajectory of the objective lens The tangential directions of Tri to Tr3 are shifted to the right in the information track Tri and to the left in the information track Tr3 with respect to the direction of the arm 2. Also,
The tangential direction between each track also differs.

In this way, in conventional devices, the optical system, especially the dividing direction in the tracking direction of the photodetector, depending on the position on the optical disk,
Alternatively, in the case of irradiating a plurality of light beam spots, the tangential direction of the information track with respect to the direction of the spot row is inclined. Therefore, when obtaining a tracking error signal by detecting changes in the reflected light pattern of the information track using a photodetector, or when obtaining a tracking error signal by irradiating multiple light beam spots, ), the reflected light pattern differed from track to track, making it impossible to stably obtain the required tracking error signal.

In addition, recording information can be written, read, and erased at once by irradiating multiple light beam spots onto an optical disc, such as by irradiating a writing light beam spot and a reading light beam spot to monitor the recorded information. When the recording is performed on the disc, the writing light beam spot (Pw) and the reading light beam spot Pw are set at a certain position on the disk as shown in FIG. 7(a).
Even if r is located on the same track, at other positions, the reading light beam spot P
There was a problem that r was not located on the same track as the writing light beam spot Pw, and recorded information could not be monitored.

Conventionally, in order to solve this problem, Japanese Patent Application Laid-Open No. 5718935
Various techniques are disclosed in Japanese Patent Publication No. 4, Japanese Patent Application Laid-Open No. 1988-1.43452, and Japanese Patent Publication No. 7425-1988.

Among them, Japanese Patent Application Laid-Open No. 57-189354 describes the distance between the center of rotation of the swing arm and the objective lens! ,
Let the distances between the rotation center of the optical disc and the innermost and outermost information tracks be r min and r, respectively.
When aX, the rotation center of the swing arm is set at a position just -π; By configuring the optical disc so that the intersection with the outermost information track and the rotation center of the optical disc are located on a straight line, the amount of tangential tilt in each of the information tracks described above is minimized. For example, FIG. 8(a),
As shown in (b), if we take the y-axis and the y-axis and set the coordinates of the rotation center of the arm as C(rmin'rmπ, ri), the maximum tilt angle θ□ax in the tangential direction of the information track becomes the minimum, At that time, θ□ is.

However, the technique disclosed in the above-mentioned Japanese Patent Application Laid-open No. 57-189354 does not take into account the angular change φ in the tangential direction between the arm 2 and the trunk direction due to the rotation of the arm 2.
In particular, in order to maintain the aforementioned plurality of light beam spots on the same track or at a predetermined position, l must be made sufficiently large.

Furthermore, in Japanese Patent Application Laid-open No. 60-143452, FIG.
As shown in a) to (C), the objective lens 9 is mounted on the rotating member 2.
A first reflecting member 23 and a second reflecting member 24 set parallel to the first reflecting member 23 are sequentially arranged in a row along the optical axis, and the second reflecting member 24 is arranged in a row along the optical axis. 24 is provided on the rotating wheel center of the rotating member 2. Further, the optical system main body 17 having the light emitting means 6 and the light receiving means 11 provided on the rotary member 2 is optically coupled to the second reflecting member 24, and the first and second reflecting members 24 are arranged parallel to each other. By projecting the image of the track into the optical system main body with the reflecting members 23 and 24 regardless of the rotation angle of the rotation member 2, the influence of the angular change between the rotation member and the track direction due to the rotation of the rotation member 2 is reduced. is canceling out.

However, in the technique disclosed in JP-A-60-143452, as shown in FIGS. 9(b) and 9(c), the tangential direction of each information track on the trajectory of the objective lens changes There was a problem that θ2 remained as it was.

Further, Japanese Patent Publication No. 64-7425 discloses a device comprising a main arm 2, a rotating body 21, and a sub-arm 19, the structure and principle of which are shown in FIGS. 10 and 11. The main arm 2 is disposed adjacent to the mounting member for the disc-shaped recording medium 5, and is rotatably connected around the rotation shaft 1, and is connected to the inner and outer peripheries of the disc-shaped recording medium 5 at the other end. Move in an arc between. Further, the rotating body 21 is rotatably provided at the other end of the main arm 2, and has a pickup 3 that faces the disc-shaped recording medium 5 and reads information from the disc-shaped recording medium 5. It has a connecting arm 22 extending toward the outside of the mounting part. Furthermore, the sub-arm 19 is disposed at a position apart from the mounting portion of the disc-shaped recording medium 5, and the rotation shaft 2
0, one end is rotatably connected to the connecting arm 22, and the other end is rotatably connected to the tip of the connecting arm 22, and
The length is shorter than that of the second main arm 2. When the rotating body 21 moves with the rotation of the main arm 2, the rotating body 21 is rotated by the sub arm 19 via the connecting arm 22, so that the extension line of the connecting arm 22 is always aligned with the disc-shaped medium 5. Set it so that it points toward the center of rotation.

However, in the technique disclosed in the above-mentioned Japanese Patent Publication No. 64-7425, as shown in FIG.
Length from point P on the extension line of P! Letting point Q be a point at a distance of , when point P moves on the trajectory drawn by the pickup 3, the moving trajectory of point Q does not make a circular motion as shown in FIG. Therefore, it is impossible to set the above-mentioned components so that the extension line of the connecting arm 22 always points toward the center of rotation of the disc-shaped medium 5, and there is a problem in that an error always occurs.

Furthermore, in order to reduce this error, the length of the main arm must be made sufficiently long, and problems such as the installation position of the sub-arm result in an increase in the size of the device.

That is, as shown in FIG. 12, the rotation center of the optical disc is set at the origin O, and the rotation center of the main arm 2 is set at A(ax,
ay), and the radius of rotation is r. Let C be the circumference drawn by the tip of the main arm 2, draw a tangent to the circumference C through the origin and make it the y-axis, take the y-axis perpendicular to the y-axis and take the angle θ as shown in the figure.

Let the coordinates of point P (px+py) on C be ax, ay,
When expressed using r and θ, px=ax+r cosθ
(1) py=ay+r sinθ
(2) becomes. Let a point Q (qx, qy) be a point on the extension line of OP from point P at a distance of length l. Point Q (qx.

If the coordinates of q are expressed using pX+ py+ 1-, then
qy-py (1+E/V'i surface-py")
(4) becomes. (3), (4), (1), (
By substituting 2), the locus of the point Q due to the rotation of the arm 2 is obtained and illustrated as shown in FIG. 13, and it can be seen that the locus of the point Q does not draw a circle.

The purpose of the present invention is to solve the above-mentioned problems of the conventional swing arm system, to be able to constantly and stably detect tracking errors, and to position a plurality of light beam spots at predetermined positions for each information track. The object of the present invention is to provide an excellent optical disk device that can extremely easily realize high-speed rotation, high-speed access, and high transfer rate.

[Means and effects for solving the problems] The optical disc device of the present invention is a swing arm type optical disc device, in which the optical system unit including the objective lens moves in an arc on the optical disc surface. a first guide member that defines the trajectory of the optical system section; a connecting member that rotatably connects the optical system section; and a connecting member that connects the optical system section to the first guide member of the optical system section. a second guide member for changing an angle with respect to the guide member; fixed point holding means for causing the second guide member to pass through a fixed point; and distance adjustment for changes in the distance between the fixed point and the optical system section. It is characterized by having means.

The structure and operation of the present invention will be explained with reference to a conceptual diagram shown in FIG. In FIG. 1, the rotation center A and rotation radius r of the first guide member 2 are set so that the trajectory circumference C of the optical system section 3 passes through the rotation center point O of the optical disk, Take the fixed point B above. When the beam spot is on the i-th track, that point is defined as a point Pi, and each point between PiO and PiB is defined as αi.

Since all the vertical angles on the arc OB are equal, the angle αi is always constant at all points with respect to the track from the innermost circumference to the outermost circumference of the optical disc. That is, at point Pi, the angle between the guide member and the optical disc in the radial direction is always constant. Therefore, by fixing the optical system section to the second guide member at an appropriate angle β and holding it rotatably relative to the first guide member, the optical system section can be fixed at a radius of the optical disc. Regardless of the position of the optical system, the optical system, especially the splitting direction of the tracking direction of the photodetector, or the spot array of multiple beams can be held in the tangential direction of each information track. can always be kept consistent. This makes it possible to eliminate the conventional drawbacks of fluctuations in the tracking error signal due to the rotation of the optical system section and positional deviations of the spots with respect to each information track when a plurality of light beam spots are irradiated. Note that the same effect can be obtained no matter where point B is on the circumference C.

〔Example〕

FIGS. 2(a) to 2(C) are diagrams each showing a configuration of an example of an optical disc device of the present invention. Figure 2 (a) to (c)
A pickup 3 is rotatably connected to one end of an arm 2 that is rotatable around a rotation axis 1 by a connecting member 12, and a linear motor 4 is configured at the other end of the arm 2. The arm 2 is rotated to displace the pickup 3 in the radial direction with respect to the optical disk rotating in a predetermined direction. The rotation shaft 1 is provided at a position such that the circumference C of the locus of the objective lens of the pickup 3 passes through the rotation center 0 of the optical disk. Guide member 13
is connected to the pickup 3 as shown in FIG. 2(b), and is rotatable by a holding member 14 at a point B on the circumference C as shown in FIG. 2(C). The arm is slidably held in the axial direction of the arm according to a change in the distance between the pickup 3 and the pickup 3.

The configuration of the pickup 3 is similar to the conventional example shown in FIG. 5(b).

In this embodiment, the guide member 13 eliminates the deviation between the optical system of the pickup 3 and the tangential direction of each information track, which conventionally occurs due to the displacement of the pickup 3. The correction is made by changing the angle so that the dividing line direction of the optical system of the pickup 3, particularly the photodetector, always matches the tangential direction of each information track. As a result, in the optical disc device of this embodiment, stable tracking servo is applied from the innermost track to the outermost track of the optical disc, and in addition, the arm 2 and the guide member 1
3 can be made shorter than before, which is very advantageous for miniaturizing the device, increasing access speed, and increasing the rotation speed of the optical disk.

Furthermore, even when a multi-beam laser is mounted on the light source to achieve a high transfer rate in this embodiment, multiple beam spots can be stably held on predetermined tracks from the innermost track to the outermost track of the optical disc. , it is not necessary to add a complicated optical system or servo mechanism to maintain a plurality of beam spots on a predetermined track, and a high transfer rate can be easily achieved.

FIG. 3 is a diagram showing the configuration of another example of the optical disc device of the present invention. In FIG. 3, a pickup 3 is rotatably connected to one end of an arm 2 that is rotatable around a rotation shaft 1, and a linear motor 4 is configured at the other end of the arm 2. The arm 2 is rotated to displace the pickup 3 in the radial direction with respect to the optical disk rotating in a predetermined direction. The configuration of the pickup 3 is similar to the conventional example shown in FIG. 5(b). The guide member 13 is connected to the pickup 3 at one end, and is rotatable by a holding member 14 at a point B' on the rotation axis 0 of the optical disc, and is rotatable between the point B' and the pickup 3.
The optical disc is held slidably in the radial direction of the optical disc so as to accommodate changes in distance between the disc and the disc.

In this embodiment, the pickup 3 is connected to the rotating shaft of the optical disk by the guide member 13.
By always holding it in a constant direction with respect to the radial direction of the optical disc, the optical system of the pickup 3, especially the direction of the dividing line of the photodetector and the direction of each information track, can be adjusted at all positions from the innermost track to the outermost track of the optical disc. The tangential directions are the same. As a result, the optical disc device of this embodiment has the advantage that the position of the rotation axis 1 of the arm 2 can be set freely in addition to the effects of the first embodiment shown in FIGS. 2(a) to 2(C). There is.

FIGS. 4(a) to 4(d) are diagrams showing the configuration of still another example of the optical disc device of the present invention. Figure 4(a)-(d)
In FIG. 4, the optical system holding member 15 includes an objective lens 9, a forcing mechanism and a tracking mechanism that can minutely displace the objective lens 9 in two-dimensional directions of the optical axis direction and the radial direction of the optical disk, and a reflecting mirror 16. It has as shown in (C). Furthermore, the objective lens 9 is connected to a guide rail 18 (first guide member) which is set to move on a circumference C passing through the optical disk rotation center O by means of the connecting member 12, and which is rotatable around the optical axis. 18
are connected so that they can move freely along the The guide member 13 (second guide member) is held rotatably around point B on the circumference C by a holding member 14 as shown in FIG. 4(a), and one end is attached to the optical system holding member. 15
The optical system holding member 15 is configured to be slidable as shown in FIG. 4(b) depending on the distance between the point B and the objective lens 9. Also, near the point B of the guide member 13, a light source 6 and a collimator lens 7 are provided as shown in FIG. 4(d).
, a beam splitter 8, an error detection optical system 10, and a light emission detection optical system 17 having a photodetector 11.
A linear motor 4 is provided at the other end to rotate the guide member 13, thereby moving the optical system holding member 15 on the circumference C along the guide rail 18.

The linear motor 4 has a function of balancing the weight of the movable part at point B.

Next, the relationship of the entire optical system will be explained. The light emitted from the light source 6 passes through a collimator lens 7 and a beam splitter 8.
, a reflection mirror 16, and an objective lens 9, and are irradiated onto the optical disc 5 in a spot shape.

The light reflected by the optical disk 5 passes through an objective lens 9, a reflection mirror 16, a beam splitter 8, and an error detection optical system 10.
The light is guided to the photodetector 11 through the. Further, each of the above-mentioned optical members is arranged so that the optical axis passes through point B.

In this embodiment, PO is used at all positions on the optical disc.
The angle α formed between
By appropriately rotating and arranging the optical axis,
The dividing line direction of the optical system, particularly the photodetector, and the tangential direction of each information track can always be made to coincide. Note that point B may be any point on the circumference C, but in this embodiment, the balance of the load applied to the near motor 4 and the optical system holding member 15 when rotating the guide member 13 is determined. Considering the loss of driving force at the sliding part with the guide member 13,
Circumference C so that the distance change between point B and the objective lens is minimized.
A point that is symmetrical to the midpoint Pn of the trajectory of the objective lens with respect to the center Q of is selected as point B.

Further, the tracking mechanism of the objective lens is configured to have an appropriate angle with respect to the guide member 13 so that its driving direction always coincides with the direction of the surface, and when the objective lens is minutely driven in the tracking direction, the track tangent is Displacement in the direction is prevented from occurring.

As explained above, in this embodiment, in addition to setting the position of point B in consideration of the balance and loss of the driving force when rotating the guide member 13, the guide member 13 is incorporated with a driving force transmission function, and the optical system is The rotational moment around the fulcrum is kept small by separating the light emission detecting optical system and placing the heavy light emission detection optical system near the fulcrum (point B). Therefore, the load on the linear motor 4 is small, which is very advantageous for shortening access time and increasing the speed of disk rotation.

〔Effect of the invention〕

As can be seen from the above explanation, according to the present invention, it is possible to make the dividing line in the tracking direction of the optical system of the pickup section, especially the photodetector, exactly coincide with the tangential direction of each information track at any position on the surface of the optical disc. I can,
This eliminates tracking errors caused by rotation. Further, when a plurality of beam spots are irradiated onto an optical disk, the positional deviation of each beam spot with respect to a predetermined track can be minimized, and the radius of rotation of the pickup section can be made considerably smaller than in the past. Furthermore, this effect has the advantage that high-speed access, high-speed disc rotation, high transfer rate, and miniaturization of the optical disc device can be easily achieved.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the concept of the optical disc device of the present invention, FIGS. 2(a) to (C) are diagrams showing a first embodiment of the optical disc device of the present invention, and FIG. 3 is a diagram for explaining the concept of the optical disc device of the present invention. FIGS. 4(a) to 4(d) are diagrams showing a third embodiment of the optical disc device of the present invention, and FIGS. 5(a), (b), Figure 6, Figure 7, Figure 8 (a
), (b), Figures 9 (a) to (C), Figure 10, Figure 1
1, FIG. 12, and FIG. 13 each show an example of a conventional optical disc device. 2...Arm 3...Pickup 12
...Connecting member 13...Guide member 14.
...Holding member Fig. 2 (a) Fig. 4 (a> Fig. 5 (a) (a) Fig. 7 (a) (b) Fig. 8 Procedure main document 1, specification page 11 In line 16, "with the above-mentioned guide member" is corrected to "with the above-mentioned second guide member 13." May 29, 1989

Claims (1)

[Claims] 1. In a swing arm type optical disc device, a first guide member that defines the trajectory of the optical system unit so that the optical system unit including the objective lens moves in an arc on the optical disc surface; a connecting member that rotatably connects the first guide member and the optical system section; a second guide member that is connected to the optical system section and changes the angle of the optical system section with respect to the first guide member; An optical disc device comprising fixed point holding means for causing the second guide member to pass through the fixed point, and distance adjusting means for changing the distance between the fixed point and the optical system section.