JP2541942B2 - Optical head moving device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a voice coil type optical head moving device in which a movement guide axis of an optical head and a center of gravity of the optical head are aligned on the same horizontal line.

[Prior Art] In recent years, instead of using a magnetic head, by converging a light beam and irradiating it onto an optical recording medium (disk),
There is a situation where an optical information recording / reproducing apparatus that records information at a high density or quickly reproduces information recorded at a high density is drawing attention.

In the above optical device, track access means is generally provided so that information can be recorded on or reproduced from an arbitrary target track. Further, a focus servo means is provided for holding the light beam applied to the disc in a spot shape, and a tracking servo means is provided for holding the light beam on a predetermined track. . By the way, the track access means uses a coarse access (coarse movement) means including an objective lens for converging and irradiating a disk with a light beam, and a fine access (fine movement) means for moving the objective lens of the optical head by a lens actuator. The coarse access means or the fine access means is operated depending on the size from the current track position to the target track position. Then, an access process in which the optical head is moved to the vicinity of the target track by the rough access means in a short time and then the objective lens is finely moved to be placed on the target track is generally used.

By the way, as a conventional example of a linear motor for forming the coarse movement means of the optical head, there is, for example, the one shown in FIG. 10 disclosed in JP-A-61-106059.

In this conventional example, bearings are provided on both sides of the carriage (movable table) 2 on which the optical head 1 is mounted on the upper side.
3a, 4a; 3b, 4b are attached, and these bearings 3a, 4a; 3b, 4b roll the guide rails 5a, 5b to thereby rotate the optical head 1
To be able to move. A coil 7 that is loosely fitted in the iron core 6 is housed in the hollow portion on the upper side of the carriage 2. A permanent magnet 8 and an iron core 9 are arranged in the lower hollow portion.

By adopting the structure of this conventional example, the optical head 1
The distance between the action line L _A and the center of gravity Gb of the force acting to move the can to short, there is a possible to suppress the vibration occurring in such case of moving the optical head 1.

[INVENTION try to Problem solving] The above conventional examples, although that is smaller the distance between the center of gravity Gb of the action line L _A and the optical head 1 of the force, as can be seen from FIG. 10, the optical head 1 Guide rail 5 and the tracking actuator part that is
The distance (height difference) between the a, 5b and the bearings 3a, 4a; 3b, 4b is large. Therefore, when the objective lens is moved, the vibration generated by the operation of the tracking actuator, which acts like a vibration exciter, acts on the bearings 3a, 4a; 3b, 4b as a moment of force and causes the carriage 2 to move. Hinder smooth movement,
There are drawbacks that it takes a long time to seek to the target track, and the guide rails 5a and 5b are made uneven so that the life is shortened.

The present invention has been made in view of the above points, and an object of the present invention is to provide a voice coil type optical head moving device which does not hinder the smooth movement of the carriage even when the tracking actuator operates.

[Means and Actions for Solving Problems] In the present invention, a center of gravity of a movable portion on which an optical head is mounted,
The line of action of the force acting on the movable part and the movement guide axis of the movable holding member of the movable part are aligned on the same horizontal line, and the light for detecting the position of the movable part is parallel to the moving direction including the center of gravity of the movable part. Since it is made to pass from the line in the plane orthogonal to the moving direction of the movable part, it is possible to reduce the influence of the vibration generated in the movable part when the access control is executed toward the target track, and it is possible to accurately move the movable part. The position of the part can be detected.

EXAMPLES The present invention will be specifically described below with reference to the drawings.

1 to 4 relate to a first embodiment of the present invention, FIG. 1 is a sectional view of an optical head moving device of the first embodiment, and FIG. 2 includes a position detecting mechanism of the optical head. FIG. 3 shows an optical system, FIG. 3 shows an optical scale, and FIG. 4 shows a magnetic material to which the optical scale is attached.

In the optical information recording / reproducing apparatus 11 having the first embodiment, an optical head 13 is arranged so as to face a disc-shaped recording medium (disk) 12 as shown in FIG. Movable part main bodies 15 and 15 constituting the (voice coil type) optical head moving device 14 of the first embodiment are attached to the respective parts. The optical head 13 and the movable part bodies 15 and 15 constitute a movable part. This optical head 13 has a flange 16 fixed on its upper surface with a screw and further movable with a movable part main body 15, 1 respectively.
By fixing it to 5, the optical head 13 is fixed to the movable part bodies 15 and 15 on both sides.

Each movable part main body 15 is formed with a substantially U-shaped concave portion that is open to the outside, and a guide rail 17 that serves as a guide when the movable part main body 15 is moved is laid facing the concave portion. Then, a pair of bearings 18, 18 are attached to the tapered surface formed on the recessed end face side of each movable part main body 15, and these bearings 18, 18 hold the guide rail 17 in a pinched state, respectively, and the shafts 19, 19 respectively. The movable part main body 15 is held rotatably around the guide rail 17 so as to be movable in the axial direction of the guide rail 17. still,
As shown in FIG. 1, the bearings 18, 18; 18, 18 provided in pairs on the left and right sides, with respect to the center of gravity G _O of the optical head 13,
Another set is provided at symmetrical positions in the direction perpendicular to the paper surface.

The optical head 13, the movable part bodies 15 and 15 on both sides of the optical head 13, and the guide rails on both sides of the movable part bodies 15 and 15
17, 17 are arranged in parallel in the horizontal direction.

By the way, the electric moving mechanism in the (voice coil type) optical head moving device 14 of the first embodiment is as follows.

A voice coil 21 is fixed to the inner wall of the concave portion of the movable portion main body 15 by adhesion or the like. Each (voice) coil 21 has a bobbinless structure without using a bobbin. A permanent magnet 22 is disposed below the coil 21, and the magnetic flux of the permanent magnet 22 penetrates the upper coil 21. Each permanent magnet 22 is fixed to the upper surface of the base 23. When a current is passed through the coil 21, a force acts on the coil 21 in the direction perpendicular to the paper surface of FIG. 1, and it is possible to control which of the vertical directions the coil 21 is moved in, depending on the direction of the current.

A magnetic material 24 having a high magnetic permeability is loosely penetrated into the hollow portion of the coil 21, and the magnetic material 24 facing the magnetic flux emitted from the permanent magnet 22.
Coil 21 to reduce the magnetic flux leaking to the surroundings.
It prevents the magnetic flux penetrating through.

By the way, each coil 21 is divided and formed as shown in the plan view of FIG. 2 (in FIG. 2, two divided coils are indicated by reference numerals 21a and 21b), and both coils 21 are formed.
A light beam for detecting the moving position of the movable part main body 15 to which the optical head 13 is attached, by arranging a and 21b apart (fixed to the concave part of the movable part main body 15) It is used for the passage.

In other words, the light beam split by the optical head 13
After passing through the slit 25 arranged in the space between 21a and 21b, it is divided into two light beams of ± 1st order by the diffraction grating 26, and after that the two beams are made into parallel light beams by the collimator lens 27. The optical scale 28 fixed to the magnetic material 24 is irradiated.

As shown in FIG. 3, the optical scale 28 has strip-shaped light-shielding portions 28a and strip-shaped (slit-shaped) transmission windows 28b that are alternately and periodically formed at pitches. on the other hand,
The two light beams passing through the collimator lens 27 are separated by a distance d.
The separated light beam is projected onto the optical scale 28 in a spot shape. The interval d is set to be a half-integer multiple of the pitch (that is, d = (2n + 1) / 2 when n is an integer). The scale pitch 2 of the optical scale 28 is set to, for example, about 100 times the track pitch of the disk 12, and can be formed by vapor-depositing chromium on a glass plate having a movable effective length of about 90 mm, for example. The optical scale 28 is fixed in the hollow portion of the magnetic material 24 shown in FIG. The spot light emitted to the optical scale 28 may have a size of about several tens of μ, which is larger than the case where the optical beam is focused on the disc 12 to be emitted.
(Unlike the case of irradiating to 12) High-precision focus control is not necessarily required.

The light beam passing through the transmission window 28b in the optical scale 28 passes through the hollow portion of the magnetic material 24 as shown in FIGS. 1 and 4, and has the slit 25, the diffraction grating 26, and the collimator lens.
Photodetector 29 fixed to the concave portion of the movable part main body 15 facing 27
Is received at.

The signal received by this photodetector 29 and photoelectrically converted is
When the optical head 13 is moved by the digital signal processing system disclosed in JP-A-60-182568, it is moved by counting the optical pulses transmitted through the transmission window 28b of the optical scale 28. The quantity is detected. Also, depending on the phase of these two light spots,
It is possible to determine in which direction the disk 3 has been moved in the radial direction (which is the direction traversing the concentric or spiral track) (the direction perpendicular to the paper surface in FIG. 1).

The slit 25, diffraction grating 26, collimator lens
27 and the photodetector 29 are attached to the main body of the optical head 13 or one of the movable part main bodies 15 or both members, and move together with the optical head 13 with respect to the magnetic material 24 and the optical scale 28 on the fixed member side.

By the way, the optical system of the optical head 13 for branching and generating the light beam used for the position detection is configured as shown in FIG.

The light beam of the laser diode 31 is collimator lens 32.
To form a parallel light beam, which is incident on the shaping prism portion 33 and refracted, and the elliptical light beam is shaped into a circular light beam. As can be seen from FIGS. 1 and 2, the light beam that is shaped by the shaping prism portion 33 and travels to the right-angled prism 36 to be described later is on a line parallel to the moving direction of the movable portion passing through the center of gravity G _O of the optical head 13. Is progressing. The light beam shaped by the shaping prism unit 33 is branched into a light beam transmitted by the half mirror unit 34 and a light beam for position detection after being reflected. The half mirror section 34 reflects, for example, 5 to 10%, and the remaining 95 to 90% is transmitted. The half mirror unit 34 can be formed by forming a thin film of λ / 4 on the prism bonding surface as a multilayer film in which a high refractive index material and a low refractive index material are multilayered. Almost 100% of the transmitted light beam passes through the polarization beam splitter section 35,
The right-angle prism 36 forms a light beam directed upward in the drawing.
Then, it is circularly polarized by the λ / 4 plate 37, and the objective lens 38
The light is focused on and is irradiated onto the disk 12. This disc 12
The return light reflected by is condensed by the objective lens 38 into a nearly parallel light beam. After that, with the λ / 4 plate 37
The light is converted into, for example, S-polarized light having a polarization direction different by 90 °, is reflected by the rectangular prism 36, and is incident on the polarization beam splitter 35. Almost 100% of the light is reflected by the polarization beam splitter 35, and is split into transmitted light and reflected light by the half mirror 39.
The transmitted light is condensed by the lens 41, received by the information reproducing photodetector 42, and the information recorded on the disk 12 can be reproduced by photoelectric conversion output.

Also, the light reflected by the half mirror 39 is a half-wave plate 43.
After being converted into P-polarized light by, the light incident on the critical angle prism 44 and reflected by the inclined surface is received by the four-division control photodetector 45. Focusing control signals and tracking control signals are generated by the photoelectric conversion output of the four-divided photodetector 45, and these control signals are applied to the lens actuator 46 to bring the objective lens 38 into a focus state and a tracking state. It can be held.

In the first embodiment, movable part main bodies 15, 15 to which the optical head 13 is attached are provided on both sides of the optical head 13, and guide rails 17, 17 are laid outside the movable part main bodies 15, 15. In other words, the optical head 13 and the movable part main body 15,1
5. The guide rails 17, 17 are arranged in parallel in the horizontal direction, and are caused by passing a current through the center of gravity Gg (or center line) of the guide rail 17 and the coil 21 mounted in the movable portion main body 15. The force acting line L _A and the center of gravity G _O of the optical head 13 including the lens actuator 46 are aligned on the same horizontal line LH. In addition, the movable part main body 15, 1 on both sides of the optical head 13
The shape of 5 is almost symmetrical. (However, the optical scale 28, the photodetector 29, etc. are not provided on the side of the movable portion main body 15 on the left side of FIG. 1, and the slit 25, the diffraction grating 26, and the collimator lens 27 are not provided. small, and center of gravity position becomes throat symmetrical N殆.) Note that the action line L _a of the force, the direction perpendicular to the page in Figure 1. In the first embodiment, the lens actuator 46
Also, when the tracking actuator is operated so as to be provided at a distance close to the same horizontal line LH, the moment of the force acting on the optical head 13 and the movable section main body 15, 15 side is reduced to the optical head moving mechanism side. The adverse effect on it is sufficiently small.

According to the first embodiment configured as described above, the center of gravity G _O of the optical head 13 (the position of the center of gravity G _O is on both sides of the movable portion main body 1).
5,15, that is, the same as the movable part), the action line L _{A of the} force acting on the movable member such as the movable part main body 15,15 to which the optical head 13 is attached, and the guide rails 17,17. Since the center of gravity Gg is aligned with the same horizontal line LH, both coils 21,21
Since a force acts on the center of gravity G _O of the optical head 13 when a movable member on the optical head 13 side is moved by applying a current to the optical head 13, no inconvenient rotational force acts on the optical head 13. In addition, when this force is applied, the bearing 1 that is rotatably supported by the movable part main body 15,15
8,8 will roll on the guide rail 17 to move, but due to processing accuracy and minute dust, the bearing
Guide rail 1 even if there is a slight swing when rolling 18,18
Since the centers of gravity Gg, Gg of 7,17 are on the same horizontal line LH as the position of the center of gravity G _O of the optical head 13, the guide rail 1
An unfavorable force moment acts on 7,17, and the optical head
It is possible to eliminate the hindrance to the smooth movement of 13. In addition, it is possible to prevent the surface of the guide rail 17 in the conventional example from easily becoming uneven due to the moment of this force.

In addition, the tracking actuator part is
Since it is formed at a distance position close to, even if the tracking actuator is operated, the influence on the optical head 13 can be sufficiently reduced.

Furthermore, since the light beam used for the position detecting means of the optical head 13 is made to pass from the line parallel to the moving direction of the movable part including the center of gravity of the optical head, in the plane orthogonal to the moving direction of the movable part, It is possible to suppress the influence of vibration that occurs when the access control is executed toward the target track, particularly the vibration that has the moving direction of the movable portion as the rotation axis, and thereby to accurately detect the position of the movable portion. Further, as compared with the conventional example, the weight of the movable portion main body can be reduced and the weight of the optical head moving mechanism can be reduced.

Further, even under an environment with external vibration or the like, it is hardly affected by the vibration (the moment of force can be reduced), and by using the first embodiment, a highly reliable recording / reproducing apparatus can be realized.

In this embodiment, the center of gravity G _{O of the} optical head (this center of gravity G _O
However, if the center of gravity of the optical head and the center of gravity of the movable part (which consists of the optical head and the movable part body) are different, the center of gravity of the movable part is _O
As a result, a light beam for position detection is emitted from a line parallel to the moving direction of the movable portion that passes through the center of gravity G _O of the movable portion and passes through a plane orthogonal to the moving direction of the movable portion.

 5 and 6 show a second embodiment of the present invention.

In the second embodiment, a semiconductor position detector is used as the position detecting means of the optical head in the first embodiment.

As shown in FIG. 6, the light beam reflected by the half mirror unit 34 is condensed by the condenser lens 51, and the optical head
The semiconductor position detector 54 fixed to the magnetic material 53 is irradiated with light through the hole of the side wall of the housing 13 and further through the hole of the movable body 52.

This semiconductor position detector (hereinafter referred to as PSD sensor) 54
Has a sectional structure as shown in FIG.

That is, the P layer 55 is on the front surface of the flat silicon and the N layer 5 is on the back surface.
6, and a high-resistance insulating layer 57 made of a silicon substrate in between. Then, electrodes for position detection are provided at both ends of the P layer 55 in the longitudinal direction of the sensor.
55a and 55b are provided, while a bias electrode 58 is provided at the center of the N layer 56 on the back surface. When the P layer 55 is irradiated with the incident light in a spot shape, a charge proportional to the light energy is generated at the incident position, and it becomes a photocurrent and passes through the resistance layer forming the P layer 55, and each electrode 55a, It is output from 55b. In this case, the resistance layer is formed so as to have a uniform resistance value over the entire surface, and the photocurrent is output in inverse proportion to the distance (resistance value) to the electrodes 55a and 55b. For example, both electrodes 55a, 55
The distance b is 2 L, and the current drawn from each electrode 55a, 55b is I
1, I2, and the photocurrent is I ₀ (= I1 + I2), the PSD sensor 54
In the case where the center position as the origin _{of, I1 = I 0 (L-} X) / (2L), I2 = I 0 (L + X) / (2L) or (I2-I1) / (I1 + I2) = X / L , I1 / I2 = (L−X) / (L + X). Here, X represents the distance (coordinate) from the origin to the spot irradiation position of the incident light.

Therefore, by measuring the currents flowing through the electrodes 55a and 55b, the position of the spot light with which the PSD sensor 54 is irradiated, and thus the position of the optical head 13 or the movable unit main body 52 can be detected.

In addition, in the second embodiment, each movable part main body 52 has a shape in which a rectangular hollow part capable of accommodating the coil 21 is provided. Further, as the magnetic material 53, a prism-shaped material having no hollow portion is used. Others are the same as those in the first embodiment, and the same members are designated by the same reference numerals.

The function and effect of this second embodiment are the same as those of the first embodiment.

 FIG. 8 shows a third embodiment of the present invention.

In the third embodiment, both sides of the optical head 13 are fixed to the movable part main bodies 61, 61 via the flanges 16, and members for movably holding the movable part main body 15 in the first and second embodiments, That is, instead of the means for rolling and moving the bearings 18, 18 on the guide rail 17, the through hole 62 is formed in each movable part main body 61.
A bush 63 that is slidably movable is fitted in the through hole 62.

An optical scale 64 is attached to the one bush 63 by providing a hollow portion like the magnetic material 24 of the first embodiment. Then, the light beam passing through the through hole on the side surface of the optical head 13 is diffracted by the diffraction grating 65 attached to the through hole of the movable part main body 61
Optical scale divided into two primary light beams, collimated by a collimator lens 66 into a parallel light beam, and fixed to the bush 63.
Irradiating 64. As the optical scale 64, the same one as shown in FIG. 3 can be used.
The light beam passes through the 64 transmission windows and is reflected by the diffraction grating 65 and the lens.
The light is received by a photodetector 67 arranged so as to face 66.

A coil 68 is fixed to the outer side of each movable part body 61, and a prismatic magnetic material 69 is loosely fitted inside each coil 68. In addition, permanent magnets 7 are provided on the bottom and side surfaces of each coil 68.
0 and 71 are arranged, and these permanent magnets 70 and 71 are fixed to the base 72.

Also in this embodiment, the center of gravity G _O of the optical head 13 including the lens actuator 46, the line of action L _{A of the} force generated when a current is passed through the coil 68, and the center of gravity G _{B of the} optical head 13 and each bush 63 ( (Or the center) are on the same horizontal line LH.

Therefore, the function and effect of the third embodiment are similar to those of the first embodiment.

 FIG. 9 shows a fourth embodiment of the present invention.

In the fourth embodiment, the light beam from the optical head 13 side, which has passed through the through hole of one movable member 61 in the third embodiment, is condensed by the condenser lens 73 without passing through the diffraction grating 65. The semiconductor position detector 74 fixed to, for example, the recess of the bush 63 is irradiated.

The other structure is the same as that of the third embodiment, and the same members are designated by the same reference numerals.

The fourth embodiment also has substantially the same operational effects as the first embodiment.

[Effects of the Invention] As described above, according to the present invention, it is possible to reduce the influence of vibration that occurs in the movable portion when access control is performed on the target track, and to accurately detect the position of the movable portion. You can

[Brief description of drawings]

1 to 4 relate to a first embodiment of the present invention.
1 is a sectional view of the first embodiment, FIG. 2 is a plan view showing the optical system of FIG. 1, FIG. 3 is an explanatory view showing an optical scale, and FIG. 4 is a perspective view showing a magnetic material to which the optical scale is attached. FIG. 5 and FIG. 5 are sectional views showing the main part of the second embodiment of the present invention, and FIG.
5 is a plan view showing the optical system portion of FIG. 5, FIG. 7 is a sectional view showing the structure of the semiconductor position detecting device used in the second embodiment, and FIG. 8 is a sectional view showing the third embodiment of the present invention. FIG. 9 is a sectional view showing a fourth embodiment of the present invention, and FIG. 10 is a sectional view showing a conventional example. 11 …… Optical information recording / reproducing device 12 …… Disk, 13 …… Optical head 14 …… Optical head moving device 15 …… Movable part body, 17 …… Guide rail 18 …… Bearing, 21 …… Voice coil 22… … Permanent magnet, 24 …… Magnetic material 28 …… Optical scale

Claims (1)

(57) [Claims] 1. An optical head mover having an optical head, a movable part on which the optical head is mounted, and position detection means for optically detecting the position of the optical head, the movable part being movable. In the device, the center of gravity of the movable part, and the line of action of the force acting on the movable part,
The light for detecting the position of the movable portion is aligned with the movement guide axis of the movable holding member of the movable portion on the same horizontal line, and is orthogonal to the moving direction of the movable portion from a line parallel to the moving direction including the center of gravity. An optical head moving device, characterized in that the optical head moving device passes through a plane.