JPH0714194A - Optical disk device - Google Patents

Abstract

PURPOSE:To provide an optical disk device capable of precisely converging and radiating a beam on an optical disk. CONSTITUTION:In a division band 219 where two light receiving surfaces 216, 217 of a bisected photodetector 218 are set opposite to each other, the shapes of the end parts of the light receiving surfaces 216, 217 are roughly triangular wave-shaped, and they mesh with each other. Thus, a division line length forming the boundary between the light receiving surfaces 216, 217 is prolonged without expanding the width (d) of the division band 219, and a linear zone in a focus error detection signal is enlarged similarly to the case where the width (d) of the division band 219 is expanded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device for recording / reproducing information by converging a light spot on an optical disk which is an optical information recording medium.

[0002]

2. Description of the Related Art In an optical disc device, when a light spot is irradiated onto an optical disc which is an optical information recording medium, the converging points of the light spot should be aligned on the optical disc and the optical axis should be perpendicular to the optical disc. It is especially important to do so. In order to match the focal points of the light spots on the optical disc, the reflected light of the emitted light is received, the focal point position is detected, and the position of the lens is adjusted based on the result.

FIG. 70 is a schematic view showing a part of a conventional optical disk device, and FIG. 71 is an enlarged conceptual view of an information track for showing a relationship between an optical disk information track and a defocus signal of each light spot in the conventional optical disk device. is there. In FIG. 70, 101 is an optical disk, 102 is a semiconductor laser as a light source, 103 is a light beam emitted from the semiconductor laser 102,
104 is a collimator lens for converting the light beam 103 into a parallel light beam, 105 is a beam splitter, 106 is an objective lens, 10
7 is a light spot condensed on the optical disc 101, 108a,
108b is a focusing coil for driving the objective lens 106 in the optical axis direction, 109 is a converging lens, and 110 is a defocus detection optical element such as a cylindrical lens for detecting the defocus amount of the light spot 107 with respect to the optical disc 101. , 111 are photodetectors and differential amplifiers for obtaining defocus signals and information signals. 112 is a semiconductor laser
102, objective lens 106, photodetector and differential amplifier 111
The optical head device section is configured by the above. 113 is the output of the photodetector and differential amplifier 111,
The defocus signal of the light spot 107 is output with respect to. Reference numeral 114 is a defocus control circuit.

In FIG. 71, 115 is a land portion where information is recorded, 116 is a groove portion, 117 is a groove interference signal observed as a defocus signal when the light spot 107 is scanned in a direction crossing the information track. Yes This signal is superimposed on the defocus signal 113. One cycle of the groove interference signal corresponds to the information track interval (which is equal to the land interval or the groove interval).

Next, the operation will be described. In FIG. 70, the light beam 103 emitted from the semiconductor laser 102 is converted into a parallel light flux by the collimator lens 104. The light beam 103 transmitted through the beam splitter 105 is condensed by the objective lens 106 on the optical disc 101 as a light spot 107. Light beam 10 reflected from optical disc 101
3 is reflected by the beam splitter 105, transmitted through the defocusing detection optical element 110, and is detected by the photodetector and the differential amplifier.
The light is received by 111 and converted into an electric signal.

Defocus correction of the light spot 107 on the optical disc 101 is performed by the light spot 10 on the optical disc 101.
The defocus amount of 7 is detected using the defocus detection optical element 110, the photodetector and the differential amplifier 111, and the output thereof is passed through the defocus control circuit 114 to the focusing coil 10.
This is performed by driving and controlling the objective lens 106 in the optical axis direction by applying it to 8a and 108b.

FIG. 72 shows, for example, Japanese Patent Publication No. Sho 62-18973 and G. Bouwhuis et al., “Principl
es of Optical Disk System
m, "Adam Hilger, pp. 77-79.
It is a block diagram which shows the conventional apparatus used for the general focus error detection called the pupil shielding method or the half-beam method described in (1985), and shows the case where a shielding plate is used. Figures 73-78
FIG. 4 shows the relationship between the defocused state of the light spot on the optical disc and the shape of the light spot on the photodetector of the conventional device.

In FIG. 72, 201 is a light emitting source such as a semiconductor laser that emits a light beam for recording and reproduction. In the figure, the light flux emitted from the semiconductor laser is referred to as E. Reference numeral 202 denotes a beam splitter which transmits the emitted light beam E and reflects a reflected light beam R from an optical disc 206 described later, and 203 makes the emitted light beam E a parallel light beam and collects the reflected light beam R on a two-split photodetector described later. A collimator lens 205 is an objective lens for converging the emitted light beam E on an optical disk 206 such as an optical disk and for converting a reflected light beam R from the optical disk into a parallel light beam. Reference numeral 207 is a shield plate that shields almost half of the reflected light flux R from the optical disc 206.

Reference numeral 209 denotes a two-divided photodetector for receiving the reflected light flux R1 of which a part is removed by the shield plate 207, and two light receiving surfaces 210, 21 arranged in a plane perpendicular to the optical axis A.
Consists of 1. Further, the direction of the dividing line of the light receiving surfaces 210 and 211 substantially coincides with the tangential direction of the upper edge 208 of the shield plate 207. Usually, this two-divided photodetector is composed of a PIN photodiode. S1 and S2 are light receiving surfaces
The electric signals obtained from 210 and 211 are represented, and the difference between S1 and S2 output from the comparator 214 is the focus error signal F.
It becomes ES.

Next, the operation of the conventional apparatus shown in FIG. 72 will be described with reference to FIGS. 73 to 78. Emitting light flux E emitted from the light emitting source 201 when recording / reproducing information
Passes through beam splitter 202 and collimator lens 20
The light flux becomes a parallel light flux at 3 and is condensed by the objective lens 205 to be irradiated onto the optical disc 206. Then, the reflected light flux R reflected by the optical disc 206 reaches the beam splitter 202 via the objective lens 205 and the collimator lens 203,
It is reflected by this beam splitter 202. Then, after almost half of the reflected light flux R is shielded by the shield plate 207, the remaining R1 is incident on the two-divided photodetector 209.

By the way, as shown in FIGS. 73 and 74, when the converging point of the outgoing light beam E is located on the optical disk 206, the converging point of the reflected light beam R1 is located on the two-division photodetector 209. In addition, the condensing point of the reflected light flux R1 is
The gap between 0 and 211, that is, the position of the two-part photodetector 209 is adjusted so as to be located on the parting line 209a. Therefore, when the condensing point of the outgoing light flux E is located on the optical disc 206, the amounts of light incident on the light receiving surfaces 210 and 211 become equal,
The outputs S1 and S2 from the light receiving surfaces 210 and 211 are also equal.
In FIG. 74, P1 is a focused spot of the reflected light flux R1 on the light receiving surface.

Next, when the optical disk 206 approaches the objective lens 205, the reflected light beam R1 is incident on the two-divided photodetector 209 before being condensed, as shown in FIG. Therefore, the figure
As shown by 76, most of the reflected light flux R1 is incident on the light receiving surface 210 and is hardly incident on the light receiving surface 211. P in Figure 76
3 shows the shape of the reflected light flux R1 on the light receiving surface 210.

On the contrary, when the distance between the optical disc 206 and the objective lens 205 becomes longer, the reflected light beam R1 is condensed before the two-divided photodetector 209 as shown in FIG. Therefore, as shown in FIG. 78, most of the reflected light flux R1 is incident on the light receiving surface 211 and is hardly incident on the light receiving surface 210. P5 in FIG. 78 indicates the shape of the reflected light flux R1 on the light receiving surface 211.

Light receiving surfaces 210, 21 on which the respective reflected light beams R1 enter
Since 1 generates currents S1 and S2 that are proportional to the respective amounts of received light, the focus error signal FES can be obtained by taking the difference between S1 and S2. Because Fig. 73 and Fig. 74
As shown in, the distance between the optical disc 206 and the objective lens 205 is proper, and the converging point of the outgoing light flux E is just the optical disc 20.
This is because the difference between S1 and S2 is zero when it is located above 6. Further, as shown in FIGS. 75 and 76, when the distance between the optical disc 206 and the objective lens 205 is too short, it is negative (or positive), and as shown in FIGS. This is because if the distance is too long, it will be positive (or negative). The focus error signal FES obtained in this way is supplied to the objective lens actuator (not shown) through the phase corrector and the amplifier, so that the focal point of the emitted light beam E is always kept on the optical disc 206.

Here, the focus error signal FES is defocused Δ
The range that changes in proportion to x (the distance between the focal point of the emitted light beam E and the optical disk 206) is called a linear zone, and when the numerical aperture of the objective lens is 0.5 to 0.6, it is shown in the conventional example. The width of the linear zone of the pupil occlusion method is 2 to 3 μm. Figure
79 is an enlarged view of the vicinity of the converging spot P1 in order to show the relationship between the converging spot P1 on the two-division photodetector 209 and the dividing line 209a. Further, FIG. 80 shows the relationship between the focus error signal FES and the focus shift Δx. Here, as shown in FIG. 79, it is assumed that the width d ₂ of the dividing line 209a of the two-part photodetector 209 is sufficiently smaller than the spread of the focused spot P1. For details, see G. Bouwhuis et al., "Princ
iples of Optical Disc Sys
tem, "Adam Hiller, pp. 77-.
79 (1985) Or Irie et al. “Focu
s Sensing Characteristics
of the Pupil Observation
Method for Continuously
Grooved Disks, "Jpn. J. Ap.
pl. Phys. 26, p. p. 183-186
(1987).

FIG. 81 is a perspective view showing the structure in the case where a roof prism is used to implement the above-mentioned pupil blocking method or half-beam method. 82 to 84 show the relationship between the defocused state of the light spot on the information recording surface and the position and shape of the light spot on the photodetector of the conventional apparatus. In FIG. 81, 301 is a light source such as a semiconductor laser that emits a recording / reproducing light beam, and a light beam emitted from this light source 301 is referred to as E. Reference numeral 302 denotes a collimator lens that converts the light flux E emitted from the light source 301 into a parallel light flux. Reference numeral 303 denotes a beam splitter which reflects a parallel light flux from the collimator lens 302 and transmits a reflected light flux R from an optical disc 305, which will be described later, and 304 condenses an outgoing light flux E on an information recording surface 323 of the optical disc 305, which will be described later, and also an optical disc. It is an objective lens that makes the reflected light flux R from 305 a parallel light flux.

Reference numeral 305 is an optical disk such as an optical disk, and 306 is a converging spot formed on the information recording surface 323 of the optical disk 305. 307 is called a guide groove and is engraved in the x direction as shown in the figure. here,
The y direction is in a plane parallel to the optical disc 305, and
The direction is perpendicular to the guide groove 307. The z direction is a direction perpendicular to the information recording surface 323. Reference numeral 308 is a focusing lens that focuses a reflected light flux R on two-divided photodetectors 311 and 315, which will be described later, and 309 is a roof prism that splits the reflected light flux R from the optical disk 305 into two light fluxes R1 and R2. . 310 is the roof of the roof prism 309, which faces the y direction.
Reference numeral 311 is a two-divided photodetector that receives the light flux R1, and is composed of two light-receiving surfaces 312 and 313 arranged in a plane perpendicular to the optical axis A. Reference numeral 314 is a light spot on the two-divided photodetector 311. Further, 315 is a two-divided photodetector that receives the light flux R2, and is arranged in a plane perpendicular to the optical axis A.
It is composed of two light receiving surfaces 316 and 317. Reference numeral 318 denotes a light spot on the two-divided photodetector 315.

The direction of the dividing line that is the boundary between the light receiving surfaces 312 and 313 and the direction of the dividing line that is the boundary between the light receiving surfaces 316 and 317 are substantially the same as the direction of the roof 310 (y direction) of the roof prism 309. ing. Normally, these two-split photodetectors are PI
It is composed of an N-type photodiode. Also, S
Reference numeral 1 represents the sum of output signals obtained from the light receiving surfaces 312 and 317, and S2 represents the sum of output signals obtained from the light receiving surfaces 313 and 316. Then, the difference between S1 and S2 is taken out by the differential amplifier 319 and becomes the focus error signal FES. This focus error signal FES is a phase compensation circuit / amplifier.
It is supplied to the objective lens drive mechanisms 321 and 322 via 320.

Next, the operation of the conventional apparatus shown in FIG. 81 will be described with reference to FIGS. 82 to 84. When recording / reproducing information, the outgoing light flux E emitted from the light source 301 is emitted.
Is collimated by the collimator lens 302, is reflected by the beam splitter 303, and travels toward the objective lens 304. Next, the emitted light flux E is condensed by the objective lens 304 and is irradiated as a condensed spot 306 on the information recording surface 323. Then, the reflected light flux R reflected by the information recording surface 323 passes through the objective lens 304 and the beam splitter 303, and the focusing lens 30
8 produces a focused light beam. Next, the roof prism 30
It is divided into two luminous fluxes R1 and R2 by 9 and R1 is 2
The R2 is incident on the split photodetector 311 and the split photodetector 315.

By the way, a condensing spot 306 of the outgoing light beam E
82 is positioned on the information recording surface 323 of the optical disc 305, the focused spot 314 of the light beam R1 is positioned on the two-division photodetector 311 and the light beam R is positioned as shown in FIG.
The position of the two-division photodetector 311 is adjusted so that the one focused spot 314 is located on the dividing line between the light receiving surfaces 312 and 313. At the same time, the focused spot 318 of the light flux R2 is 2
The light beam R2 should be located on the split photodetector 315.
The position of the two-divided photodetector 315 is also adjusted so that the focused spot 318 of is located on the dividing line between the light receiving surfaces 316 and 317. Therefore, when the condensing spot 306 of the outgoing light flux E is located on the information recording surface 323, the light amounts incident on the light receiving surfaces 312 and 313 are equal, and the outputs from the light receiving surfaces 316 and 317 are also equal. Therefore, the sum S1 of the output signals obtained from the light receiving surfaces 313 and 316 and the sum S2 of the output signals obtained from the light receiving surfaces 312 and 317 are equal.

Next, consider a case where the optical disk 305 approaches the objective lens 304 by Δz. As shown in FIG. 83, the luminous flux R
Before being condensed, 1 and R2 are incident on the two-divided photodetectors 311 and 315, respectively. Therefore, most of the light flux R1 is incident on the light-receiving surface 313 and hardly enters the light-receiving surface 312, and at the same time, most of the light flux R2 is incident on the light-receiving surface 316 and the light-receiving surface 317.
Will almost not be incident on. Therefore, the light receiving surfaces 313 and 31
S1 which is the sum of the output signals obtained from 6 is
It becomes larger than S2 which is the sum of the output signals obtained from 317.

On the contrary, if the distance between the optical disk 305 and the objective lens 304 is increased by Δz, as shown in FIG.
1 and R2 collect light in front of the two-divided photodetectors 311 and 315, respectively. Therefore, most of the light flux R1 is incident on the light receiving surface 312 and hardly enters the light receiving surface 313.
Most of the light flux R2 is incident on the light receiving surface 317, and is hardly incident on the light receiving surface 316. Therefore, S1, which is the sum of the output signals obtained from the light receiving surfaces 313 and 316, is
Is smaller than S2 which is the sum of the output signals obtained from

As described above, the focus error signal FE
S can be obtained by taking the difference between S1 and S2. This is because, as shown in FIG. 82, the distance between the optical disc 305 and the objective lens 304 is proper and the focused spot 30 of the outgoing light flux E is 30.
If 6 is located exactly on the information recording surface 323, S
This is because the difference between 1 and S2 is zero. When the distance between the optical disc 305 and the objective lens 304 is too short as shown in FIG. 83, it is positive (or negative), and when the distance between the optical disc 305 and the objective lens 304 is too far as shown in FIG. This is because is negative (or positive).

FIG. 85 shows defocusing Δf (Δf is a focused spot)
6 is a graph showing the relationship between the focus error signal FES and the distance between 306 and the information recording surface 323). The focus error signal FES thus obtained is used as the phase compensator / amplifier 320.
The light beam is supplied to the objective lens driving mechanisms 321 and 322 through, and the condensed spot 306 of the emitted light beam E is always kept on the information recording surface 323. Further, as described in the configuration of the embodiment, the roof 310 of the roof prism 309 is set in a direction substantially orthogonal to the tangential direction (x direction) of the guide groove 307 of the optical disk 305. This is to keep the disturbance appearing in the focus error signal FES as small as possible when the focused spot 306 crosses the guide groove 307 of the optical disk 305. Regarding this, “Irie et al., Focus
Sensing Characteristics of the Pupil Obscuration M
ethod for Continuously Grooved Disks, Japan Journa
l of Applied Phisics, vol.26, pp.183-186 (1987) ”.

Next, the parameters of the optical components when this method is applied to a typical optical disk device will be described with reference to FIG. When the distance between the guide grooves 307 is 1.6 μm and the optical disc 305 has a diameter of 90 mm or 130 mm, the numerical aperture NAobj of the objective lens 304 is usually 0.5.
To 0.55. Now, this NAobj is 0.5
5 and the diameter φobj of the entrance pupil of the objective lens is 3 mm, the focal length fobj of the objective lens 304 is fobj = (φobj / 2) / NAobj = (3/2) /0.55=3.3 ( mm) (1) At this time, the focused spot 30 on the information recording surface 323
The diameter of 6 is about 1 to 2 μm. On the other hand, focusing lens 30
The focal length fs of 8 is often set to 10 times to 20 times fobj so that the diameter of the focused spots 314 and 318 on the photodetectors 311 and 315 can be increased to several tens to 50 μm. In the following, fs is 33 times 10 times as large as fobj
Consider the case when set to.

By the way, it is desirable that the optical distance d ₃ from the focusing lens 308 to the roof prism 309 is small. This is because when the roof prism 309 moves away from the focusing lens 308 (d ₃ increases), the light beam diameter at the position of the roof 310 becomes smaller, so that the reflected light beam R becomes two semi-circular light beams R.
This is because the positional accuracy of the roof 310 for dividing into 1 and R2 becomes strict. Furthermore, the shape of the roof 310 is not a perfect acute angle, so if the beam diameter at this position is small, the roof 310
This is because the amount of light reaching the two-divided photodetectors 311 and 315 is reduced. Here, d ₃ is 1 / of fs
Consider the case of 3, that is, 11 mm. Then the diameter .phi.p of the light beam at the position of the roof prism, φp = φobj * (fs -d 3) / fs = 3 3 *.. (33 - 11) / 33 = 2 2 (mm) ... (2) becomes The positional accuracy of the roof 310 in the x direction is several 100 μm, which is a practical value.

Next, the deflection angle θ by the roof prism 309
₃ is the distance s from the optical axis A of the dividing line between the light receiving surfaces 312 and 313 of the two-divided photodetector 311 (the dividing line between the light receiving surfaces 316 and 317 of the two-divided photodetector 315). The above d ₃ and fs can be expressed as θ ₃ = s / (fs−d ₃ ) ... (3). s cannot be increased because the two-divided detectors 311 and 315 are usually contained in one package, and a general value is 0.2 mm to 0.5 mm. Here, assuming the case where s is 0.3 mm, θ ₃ becomes θ ₃ = 0.3 / (33−11) = 13.6 (mrad) (4) from the above equation.

Finally, the apex angle of the roof 310 is 2φ, and θ ₃
Is sufficiently small, θ ₃ = Arcsin {n * sin (π / 2-φ)}-(π / 2-φ) = n * (π / 2-φ)-between θ ₃ and φ Since (π / 2-φ) = (n-1) * (π / 2-φ) (5) holds, the refractive index n of the glass that constitutes the roof prism is set to a general value of 1.5. For example, φ is φ = π / 2- {θ ₃ / (n-1)} = π / 2- {0.0136 / 0.5} = 1.54359 (rad) = 88.44 (degrees) ... (6) Therefore, the apex angle 2φ is 176.88 degrees.

Next, a mechanism for making the optical axis of the light applied to the optical disk perpendicular to the optical disk will be described.
FIG. 87 is an exploded perspective view showing a conventional optical disk device described in JP-A-59-223953, and FIG. 88 is a schematic sectional view thereof. In FIGS. 87 and 88, 401 is an objective lens, 402 is an objective lens driving device, 410 is a convex spherical surface formed on the bottom of the base of the objective lens driving device 402, 403 is an optical block, and 411 is an optical block 403. 404a, 404b, 412a, 412b are coil springs, 405a, 405b, 405c, 405d are screw holes, 406a, 406
b, 406c, 406d are screws, 408 is the optical axis of the objective lens 401, 4
09 is the focus.

The convex spherical surface 410 is fitted into the concave spherical surface 411, and the objective lens driving device 402 is rotatable around the convex spherical surface 410 and the concave spherical surface 411.
It is attached to 3. The coil springs 412a and 412b are compressed by the screws 406c and 406d screwed into the screw holes 405c and 405d, and pull the objective lens driving device 402 toward the optical block 403 side with a constant force.

Next, the operation will be described. Coil spring 40
4a and 404b push up the objective lens driving device 402, and the spherical surface 410
And the spherical surface 411 moves smoothly. Screw 406
a and 406b are screws for adjusting the inclination of the objective lens.
By turning the screw of the book, the tilt of the objective lens 401 integrated with the objective lens driving device 402 is adjusted.

FIG. 89 is a perspective view of a main part of a conventional optical disk device shown as a conventional example in Japanese Patent Publication No. 63-53618, and FIG. 90 is a sectional view taken along the line III--III of FIG. In the figure, 531 is a base made of a magnetic material, and a shaft 532 is fixed to the central portion of the upper surface. 533 is a bearing tube that is fitted and held by the shaft 532 and constitutes a sliding bearing mechanism together with the shaft 532, and is fixed to the holding tube 534. 534a is the objective lens 535
A bottom wall 534b that supports the focusing coil 536 and a tracking coil 537 are fixed to the outer circumference of the cylindrical portion 534b. Then, the outer yokes 539a and 539b are provided outside the cylindrical portion 534b,
An inner yoke (not shown) is provided inside the cylindrical portion 534b, and the permanent magnet 540 is connected to the outer yokes 539a and 539b and the base.
Bonded between 531.

Reference numeral 541 is a small shaft that is erected on the upper surface of the base 531. A neutral position setting damper member 542 made of rubber or the like is provided between the small shaft and the bearing tube 533. Reference numeral 543 is a light passage hole for guiding the light incident on the objective lens 535.

Next, the operation will be described. By controlling energization of the focusing coil 536, the position of the holding cylinder 534 is driven in the Z-axis direction in FIG. 89, and focusing control is performed. Also, by energizing the tracking coil 537, the position of the holding cylinder 534 is driven in the Y-axis direction in FIG. 89 to perform tracking control.

FIG. 91 is a sectional view showing the principal part of a conventional optical disk device disclosed in Japanese Patent Laid-Open No. 4-243021, FIG.
91 is a model diagram showing a state in which the adhesive, which is the fixing means after the angle adjustment, serves as a spring element and a damping element in FIG. 91. FIG.

In the figure, an optical head 651 comprises an objective lens assembly 652 and a carriage 653. The objective lens assembly 652 includes an objective lens 654, an objective lens actuator 655, and a laser starting mirror 656, and the objective lens 65 is provided at the center of the bottom surface of the bottom plate 657.
A spherical convex portion 65 formed of a part of a sphere having a radius R ₆ centered at 4
Have eight.

On the top surface of the bottom plate 661 of the box portion 660 of the carriage 653, a mounting base 662 having a spherical concave portion is formed.

The objective lens assembly 652 is housed in the box portion 660 of the carriage 653, and with the spherical convex portion 658 placed on the mounting base 662, the spherical convex portion 658 is attached from the bottom plate 657 side by a plurality of screws 663. The area around is fixed.

The angle adjustment for making the optical axis 664 of the objective lens 654 perpendicular to the surface of the mounted optical disc 665 is performed by the chassis base 667 of the optical disc device main body 666.
Chassis base 667 through an opening 668 formed in the
This is done by tightening and loosening the screws 663 as appropriate from the underside of the screwdriver using a screwdriver. By operating the screw 663, the objective lens assembly 652 slides a small amount with the spherical convex portion 658 and the mounting base 662 in contact with each other, and the angle of the optical axis 664 can be adjusted.

670 is the spherical convex portion 658 of the bottom plate 657 and the mounting base 66.
After adjusting the angle of the optical axis 664 with the adhesive applied between 2,
Secure the bottom plate 657 to the mounting base 662. Reference numerals 670a and 670b are a spring element and a damping element, respectively, which represent the mechanical properties of the adhesive 670.

[0041]

The defocus signal in the conventional device shown in FIG. 70 is obtained by the optical disc 10 as shown in FIG.
The interference signal 117 from the groove portion 116 shown in FIG. 71 is superimposed on the mechanical surface deflection of 1. Therefore, the objective lens
Originally, 106 was only required to follow the mechanical surface wobbling component of the optical disk, but it will also be able to follow the groove interference signal 117 from the groove part,
There is a problem that it causes voltage saturation on the control circuit. In particular, at the time of accessing the information track, the total amplitude of the interference signal 117 from the groove portion is superimposed on the defocus signal 113 at a frequency determined by the access speed, which has the greatest adverse effect on the focus control system. Become. FIG. 94 is a schematic diagram showing a defocus signal during track access. As shown in FIG. 94, the groove interference signal 117 in the defocus signal 113 increases and the frequency of the groove interference signal 117 is higher in the T2 area when the information track is accessed than in the T1 and T3 areas when the tracking is performed. There is a problem that saturation and oscillation of the focus control system occur.

Further, since the conventional apparatus shown in FIG. 72 is configured as described above, the range in which the focus error signal FES changes linearly with respect to defocus, that is, the width of the linear zone is 2.
There was a problem that it was as narrow as ~ 3 μm. If the linear zone is too narrow, the servo for focus control is lost due to vibration or shock from the outside of the device, and the phenomenon that the focal point of the emitted light beam cannot be maintained on the optical disc 206 is likely to occur. Further, even a slight displacement of the two-divided photodetector 209 gives a large offset to the focus error signal FES.

As a method of expanding the width of the focus detection linear zone in the pupil blocking method, the width d _{2 of the} dividing line 209a is used.
The method for expanding the size is disclosed in Japanese Patent Laid-Open No. 63-133333 or Irie et al., "Focus Sensing Ch."
artifactistics of the Pupil
Obscuration Method forCo
intuitively Grooved Disk
s, "Jpn. J. Appl. Phys. 26.
Vol., P. p. 183-186 (1987). For example, in one of the above documents (Irie), the dividing line 20
Width d _{2 of} 9a, wavelength λ of light source 201 (= 0.78 μm), 2
D ₂ ≧ λ / NA ₁ = 0.78 μm / 0.053 = 14.7 μm while the numerical aperture NA ₁ (= 0.053) in front of the shield plate 207 for the reflected light flux incident on the split photodetector 209. It is shown that the linear zone can be expanded if the relationship of (7) is established. In fact, when d ₂ is set to 50 μm and the numerical aperture of the objective lens 205 is 0.5, d ₂ is 10 μm.
The width of the linear zone is more than double the width of the two-segment photodetector. In FIG. 95, the dividing line widths d ₂ are 10 μm and 50 μm.
The relationship between the focus error signal FES and the defocus Δx is shown for each case of m.

FIG. 96 shows what kind of sensitivity (output current per unit amount of received light) distribution the light receiving surfaces 210 and 211 of the two-divided photodetector 209 used for this analysis have in the vicinity of the dividing line 209a. K1 indicates the sensitivity distribution of the light receiving surface 210, and K2 indicates the sensitivity distribution of the light receiving surface 211. In this figure, the coordinate origin (z = 0) is the z-coordinate of the center of the dividing line 209a, and the light beam incident on this produces an equal amount of current on both the light-receiving surfaces 210 and 211 (that is, at z = 0 The sensitivities K1 and K2 of the surfaces 210 and 211 are equal). Further, in the dividing line 209a, the sensitivities of the respective light receiving surfaces change linearly, and become zero at the ends of the light receiving surfaces facing each other.

However, such a two-division photodetector 209
In the case of using, the majority of the reflected light flux R1 from the optical disc 206 is incident on the dividing line 209a. Usually two-segment photodetector 20
Since 9 is composed of a PIN photodiode, when the width of the dividing line 209a is wide, it is difficult to form a depletion layer in the region of the dividing line 209a, and the moving speed of electrons and holes generated by the incident light flux becomes slow. The phenomenon occurs. Due to this phenomenon, if the two-division photodetector 209 is also used for reproducing the information signal, the frequency characteristic is deteriorated in the two-division photodetector having a wide dividing line 209a, and the reproduction output in the high frequency band is generated. There was a problem of decrease.

Further, since the conventional apparatus shown in FIG. 81 is configured as described above, the roof prism 309 is used even though the apex angle 2φ of the roof 310 is slightly smaller than 180 degrees (176 degrees to 178 degrees). There was a problem that the roof 310 of No. 1 had to be polished so that it was not rounded and the positional accuracy of the roof was less than several 100 μm. Usually, such polishing requires time and precise work, so that the roof position accuracy is high and the roof prism whose apex angle is close to 180 degrees is expensive.

On the other hand, in the conventional apparatus shown in FIGS. 87 and 88 for making the optical axis perpendicular to the optical disk, the tilt angle of the entire objective lens driving device is adjusted although it is desired to adjust only the tilt of the objective lens. Therefore, there is a problem that the device is complicated and the number of parts is large, which hinders reduction in size and thickness. In addition, there is a problem in that the degree of freedom in design is significantly limited due to the provision of the spherical surface. In addition, adhesive is often used as the fixing method after adjusting the tilt angle, but the weight of the part held by the adhesive is large, and the entire objective lens drive device vibrates when the optical disc is accessed, causing tracking pull-in after access. There is also a problem that the access time cannot be shortened because it takes time.

Further, in the conventional device shown in FIGS. 89 and 90,
There were the following problems. That is, shaft 532 and bearing tube
Since the slide bearing mechanism is composed of 533, a frictional force is generated between the shaft 532 and the bearing tube 533 during focusing drive and tracking drive, and the frictional force acts as a nonlinear element to make the control system unstable. There were times when it ended up.

Further, due to the relative contact movement between the shaft 532 and the bearing tube 533, abrasion is generated, and the scattering of the abrasion has an optical adverse effect on the objective lens and the optical disk, and the life of the sliding bearing mechanism portion is increased. There is also a problem that it lowers.

Further, the conventional device shown in FIG.
The adjusted angle of 4 corresponds to the adjusted angle of the screw 663, but the rotation angle of the screw 663 is not accurately determined. Therefore, empirically determine how much the screw 663 should be rotated. Therefore, considerable skill is required to improve the adjustment accuracy, and it is difficult to accurately adjust the angle of the optical axis 664.

Further, since the screw is used for the angle adjustment, if another screw is used as the fixing means for the adjusted portion after the adjustment, the adjustment is misaligned, and therefore the adhesive is used as the fixing means. Therefore, there is also a problem that readjustment cannot be performed even if readjustment is necessary after fixing.

Further, since the reliability and fixing force of the adhesive are lower than in the case of screw fixing, there is also a problem that unnecessary resonance occurs in the focusing and tracking control system of the objective lens 654 with respect to the optical disk 665. there were. FIG. 97 is a frequency characteristic diagram in the focus direction of the optical disc device of FIG. In the focus control system that drives the lens 654 in the direction of arrow F in FIG. 92, since the adhesive 670 acts as the spring element 670a, the frequency f _{1 in} FIG.
Unnecessary resonance was generated.

The present invention has been made to solve the above problems, and an object thereof is to obtain an optical disk device capable of removing a groove interference signal from a defocus signal.

Further, by enlarging the linear zone without expanding the width of the dividing line of the two-division photodetector used for the pupil blocking method, the focus control operation is stabilized and the two-division photodetector of An object is to obtain an optical disk device capable of preventing deterioration of high frequency characteristics.

Also, instead of the expensive roof prism,
(EN) An optical disk device which uses an inexpensive diffraction grating, has stable operation, and is efficient.

Further, another object of the present invention is to obtain an optical disk device in which the inclination of only the objective lens can be adjusted, the structure is simple, the number of parts is small, and unnecessary vibration during access is unlikely to occur.

Further, when performing focusing control or tracking control, a stable control system can be obtained without generating frictional force, and at the same time, there is no abrasion and no optical adverse effect or shortening of life of the peripheral portion. The purpose is to obtain the device.

It is another object of the present invention to provide an optical disk device which can adjust the optical axis of the objective lens easily and with high accuracy and has a good frequency characteristic and high reliability.

[0059]

According to a first aspect of the present invention, an optical disk apparatus has two optical spots arranged in a land portion and a groove portion of an information track, and a defocus signal from each optical spot is used as a groove interference signal. After the arithmetic processing is performed so as to cancel each other, the focus control is performed by the signal subjected to the arithmetic processing.

In the optical disk device according to the second aspect of the present invention, a plurality of light spots are arranged in the land portion and at least one light spot is arranged in the groove portion, and parallel recording / parallel reproduction is performed with the plurality of light spots arranged in the land portion. After the focus shift signals from the respective light spots arranged in the land portion and the groove portion are arithmetically processed, focus control is performed by the arithmetically processed signals.

In the optical disk device according to the third invention, the light beam is divided by using the diffraction grating to form a plurality of light spots, and the plurality of light spots are formed on the land portion and the groove portion by rotationally adjusting the diffraction grating. Place it on top,
The focus control is performed by the signal obtained by adding the defocus signals from the respective light spots arranged in the land portion and the groove portion.

In the optical disk device according to the fourth invention, one light spot is arranged in the land portion and two light spots are arranged in the groove portion, and the so-called differential push-pull method described in JP-A-61-94246 is used. The tracking control is performed, and the focus control is performed by a signal obtained by arithmetically processing the defocus signal from each light spot.

The optical disk device according to the fifth invention is a recording / reproducing device.
While the light spot is placed on the land portion during reproduction, the light spot is placed on the land portion and the groove portion by rotating the diffraction grating in the plane perpendicular to the light beam when accessing the information track. The focus control is performed by a signal obtained by arithmetically processing the defocus signal from the light spot.

The optical disk device according to the sixth invention is a recording / reproducing device.
While the light spot is arranged on the land portion during reproduction, the light spot is arranged on the land portion and the groove portion by rotating and driving the dove prism in a plane perpendicular to the light beam when accessing the information track. The focus control is performed by a signal obtained by processing the defocus signal from the light spot.

In the optical disk device according to the seventh aspect of the present invention, the end portions of the light-receiving surface in the divided bands where the two light-receiving surfaces of the two-division photodetector face each other are substantially sawtooth-shaped or substantially triangular-wave-shaped, and the respective light-receiving surface ends are formed. The parts are configured so as to mesh with each other.

In the optical disc device according to the eighth aspect of the present invention, the dividing line dividing the two light receiving surfaces is y = (p / d) z + 2np y =-(p / d) z + (2n-1) p , -D / 2 ≤ z ≤ d / 2, n: an integer.

In the optical disc device according to the ninth aspect of the invention, the pitch p of the substantially saw-toothed or substantially triangular wave portion at the end of the light receiving surface of the two-divided photodetector, the wavelength λ of the light source, and the two-divided photodetector. NA ₁ ≦ 5λ / 8p holds between the numerical aperture NA ₁ of the reflected light flux from the incident optical disk.

In the optical disc device according to the tenth aspect of the invention, the width d in the direction crossing the division band of the substantially sawtooth or substantially triangular wave portion at the end of the light receiving surface of the two-division photodetector, and the wavelength λ of the light source.
And the numerical aperture NA ₁ of the reflected light flux from the optical disc that enters the two-division photodetector, the two-division photodetector is configured so that d ≧ λ / NA ₁ is satisfied. .

In the optical disk device according to the eleventh aspect of the invention, a large number of minute light receiving surfaces are formed in the divided band of the two-division photodetector, and these minute light receiving surfaces are electrically connected to either one of the two light receiving surfaces. The connecting lines are arranged at substantially equal intervals, the direction of the connecting lines is set so as to cross the division band, and the connecting lines extending from the respective light-receiving surfaces are alternately arranged, and further connected by one connecting line. The area of the minute light receiving surface is configured to decrease substantially in proportion to the distance from the electrically connected light receiving surface.

In the optical disk device according to the twelfth invention, a large number of rectangular light-receiving surfaces are arranged in the divided bands of the two-division photodetector, and adjacent rectangular light-receiving surfaces are alternately connected to the left and right light-receiving surfaces. The rectangular light-receiving surface connected to each light-receiving surface is configured such that the length of its short side decreases substantially in proportion to the distance from the light-receiving surface.

In the optical disk device according to the thirteenth aspect of the present invention, the means for splitting the reflected light flux into a plurality of light fluxes is constituted by a light beam splitting element having a diffraction grating portion substantially half of the incident surface, and is generated by the diffraction grating portion. A focus error signal is obtained by using one or more diffracted light beams of the reflected light beam and a light beam that does not pass through the diffraction grating portion.

The optical disc device according to the fourteenth invention is
A means for splitting a reflected light beam into a plurality of light beams is a diffraction grating portion in which a substantially half surface of the incident surface is a transmission type or reflection type planar diffraction grating, and the other substantially half surface is a transmissive or reflective non-diffraction element. It is composed of a beam splitting element that is a grating part, and
One or more diffracted light beams of the reflected light flux generated by the diffraction grating portion are arranged such that a boundary line between the diffraction grating portion and the non-diffraction grating portion geometrically divides the reflected light flux into two equal parts. And a light flux from the non-diffraction grating portion are used to obtain a focus error signal.

The optical disk device according to the fifteenth invention is
In the light beam splitting element, the grating line of the diffraction grating section is a straight line, the grating period is constant, and the direction of the grating line is substantially in the direction of the boundary line between the diffraction grating section and the non-diffraction grating section. They are orthogonal.

The optical disk device according to the sixteenth invention is
In the light beam splitting element, the boundary line between the diffraction grating portion and the non-diffraction grating portion is a straight line, and the direction of this straight line is projected in a direction substantially orthogonal to the tangential direction of the guide groove on the optical disc. is there.

The optical disk device according to the seventeenth invention is
In the planar diffraction grating of the light beam splitting element, the planar diffraction grating has a binary phase depth, the duty of the phase modulation is approximately 50%, and the depth of the phase modulation is approximately 180 degrees. is there.

The optical disc device according to the eighteenth invention is
In the plane type diffraction grating of the light beam splitting element, the phase modulation is realized by the unevenness of the surface or the modulation of the refractive index.

The optical disk device according to the nineteenth invention is
In the plurality of two-split photodetectors, one or more two-split photodetectors for receiving one or more light beams obtained by the diffraction action of the diffraction grating section of the light beam splitting element and a non-diffraction grating section of the light beam splitting element The two-split photodetector for receiving the light flux from is contained in one package.

The optical disc apparatus according to the 20th aspect of the invention is
In the plurality of two-division photodetectors, the division lines of each two-division photodetector are substantially linear, and all the division lines are on one substantially straight line.

In the optical disc device according to the twenty-first aspect of the invention, the light beam splitting means is composed of elements whose half surfaces are diffraction grating portions, and the split line of the two-split photodetector has a sawtooth shape, a substantially triangular wave shape, or a substantially sawtooth shape. It has a substantially sinusoidal shape.

In the optical disk device according to the twenty-second aspect of the invention, a ring-shaped flat plate is arranged between optical means such as an objective lens and a holder for holding the same, and the flat plate is arranged between the optical means which is in contact with one surface of the flat plate and the flat plate. Between the holder and the holder in contact with the other surface, two protrusions are provided on each of the first and second straight lines that pass through the optical axis and intersect each other with the optical axis interposed therebetween, that is, four protrusions in total.

In the optical disk device according to the twenty-third aspect of the present invention, the holder is provided with a cutout portion, and the ring-shaped flat plate is provided with a tongue piece fitted into the cutout portion.

In the optical disk device according to the twenty-fourth aspect of the present invention, the holder is provided with a cutout portion, and the ring-shaped flat plate and the optical means are provided with tongue pieces fitted into the cutout portion, respectively.

An optical disc apparatus according to the twenty-fifth aspect of the invention is an objective lens for converging a light beam on an optical disc, a lens holder having the objective lens fixed at one end, and an axis parallel to the optical axis of the objective lens. And a support shaft having an inner periphery fixed to the support shaft and an outer periphery fixed to the lens holder. A set of leaf springs having a substantially concentric shape with respect to the axis is arranged.

An optical disk device according to the twenty-sixth aspect of the present invention is one in which a balance weight is provided at the other end of the lens holder so that the center of gravity of the movable portion composed of the objective lens, the lens holder and the like is arranged on the support shaft. Is.

An optical disk device according to a twenty-seventh aspect of the present invention is such that a leaf spring is provided with a bent portion which constitutes a plane portion including the axis of the support shaft.

The optical disc apparatus according to the 28th aspect of the present invention is the optical disc apparatus described in 2 above.
The leaf springs are connected to each other.

The optical disk device according to the twenty-ninth aspect of the invention is such that an elastic member is provided between the inner peripheral portion of the leaf spring and the support shaft.

In the optical disk device according to the thirtieth invention, one end of the support shaft is fixed to the base, and the holding plate holding the other end is position-adjusted in a plane perpendicular to the axis of the support shaft. It is possible to adjust the angle of the objective lens.

In the optical disk device according to the thirty-first aspect of the invention, one end of the support shaft is slidably held on the semi-concave spherical surface of the fixed portion and the other end is slidably supported on the semi-concave spherical surface of the holding plate. By moving the holding plate in a vertical plane, the supporting shaft is tilted to adjust the angle of the optical system.

In the optical disk device according to the thirty-second aspect of the present invention, one end of the support shaft is fixed to the fixed portion and the holder is slidably and rotatably supported, and the other end of the support shaft is held by the holding plate. The supporting plate is curved by moving the holding plate in a plane substantially perpendicular to the supporting shaft, and the angle of the optical system is adjusted.

[0091]

According to the first aspect of the present invention, the groove interference signal in the defocus signal obtained from the light spot arranged in the land portion is the groove interference signal in the defocus signal obtained from the light spot arranged in the groove portion. Utilizing the fact that the signals are out of phase with each other, the two defocus signals are added to remove the groove interference signal in the defocus signals.

In the second aspect of the invention, parallel recording / reproduction is performed by a plurality of light spots arranged on the land.

In the third invention, the positions of the plurality of light spots are adjusted by rotating and adjusting the diffraction grating.

In the fourth aspect of the present invention, by combining with the differential push-pull method, tracking control and defocus control that efficiently utilize the photodetector pattern are performed.

According to the fifth aspect of the invention, by rotating the diffraction grating during information track access, a plurality of light spots, which are arranged on the land portion during tracking and are used for parallel recording / reproduction, are arranged on the groove. Then, defocus signals obtained by removing the groove interference signals from these light spots are obtained.

According to the sixth aspect of the invention, by rotating the dove prism at the time of access, a plurality of light spots, which are arranged on the land portion at the time of tracking for parallel recording / reproduction, are moved to the land portion and the groove. , And the defocus signal is obtained by removing the groove interference signal.

In the seventh to twelfth aspects of the invention, the range of the focus error detection signal linearly changing with respect to the amount of defocus, that is, the linear zone is expanded, and the two-division photodetector is not deteriorated in high frequency characteristics. Is obtained.

In the thirteenth to twentieth inventions, the boundary line between the diffraction grating portion and the non-diffraction grating portion of the light beam splitting element functions as the roof of the conventional roof prism, and splits the light beam reflected from the optical disk. Further, since the light beam that has entered the diffraction grating portion is deflected by the diffraction grating and is condensed at a position different from the light beam that has passed through the non-diffraction grating portion, each light beam that has passed through the light beam splitting element corresponds to the corresponding two-split photodetector. Is received by.

The planar diffraction grating spatially modulates the phase of the wavefront of the incident light beam to generate diffracted light.

In the twenty-first aspect of the invention, the light beam splitting means is constituted by an element whose half surface is a diffraction grating portion, and the split line of the two-split photodetector has a substantially sawtooth shape, a substantially triangular wave shape, or a substantially sine wave shape. Therefore, the range in which the focus error detection signal linearly changes with respect to the amount of defocus, that is, the linear zone is expanded, and the deterioration of high frequency characteristics is small, and the fluctuation of the focus error signal due to the lateral deviation of the two-division photodetector Can be made smaller.

In the twenty-second aspect of the present invention, the pair of projections provided between the ring-shaped flat plate and the optical means have a tip as a fulcrum, and the first means connecting the projections to the optical means is the center of rotation of the projections. It can be tilted in one direction by an angle according to the height, and the pair of projections provided between the ring-shaped flat plate and the holder are rotated in one direction with the second straight line intersecting the first straight line as the center of rotation. Since it can be tilted, the tilt angle can be adjusted in each of two directions intersecting the optical means.

In the twenty-third aspect, since the tongue piece of the ring-shaped flat plate fits into the notch portion of the holder, the ring-shaped flat plate does not rotate with respect to the holder, so that one tilt direction of the optical means is changed. It does not change.

In the twenty-fourth aspect of the invention, since the tongue piece of the ring-shaped flat plate and the tongue piece of the optical means are fitted into the notch part of the holder and do not rotate together, there is no change in the two inclination directions of the optical means. .

In the twenty-fifth aspect of the invention, the pair of leaf springs having a concentric shape with respect to the support shaft deforms like an umbrella when the objective lens is driven in the focusing direction and is deformed when driven in the tracking direction. The lens holder is supported so that the objective lens can be driven and controlled in the focusing direction and the tracking direction by deforming in a spiral shape around the support shaft.

In the twenty-sixth aspect of the invention, since the center of gravity of the movable portion is on the support shaft, no rotational moment about the support shaft is generated with respect to the movable portion when seeking the optical disk.

In the twenty-seventh aspect of the invention, the bent portion of the leaf spring suppresses an unnecessary torsional resonance mode of the leaf spring particularly during drive control in the tracking direction.

In the twenty-eighth invention, the mutually coupled leaf springs reduce variation in spring constant of the leaf springs.

In the twenty-ninth aspect of the invention, the elastic member arranged between the inner peripheral portion of the leaf spring and the support shaft reduces the resonance peak of the leaf spring, and in particular increases the spring constant of the leaf spring. It is easy to set the spring constant in the tracking direction, which tends to occur, to a desired value.

In the thirtieth to thirty-second inventions, the position of the holding plate is adjusted within a plane, whereby the angle of the objective lens in the biaxial directions can be adjusted.

[0110]

1 is a schematic view showing a part of an optical disk device according to the first invention, FIG. 2 is a detailed view of a photodetector section 124 in FIG. 1, and FIG. 3 is a light spot on an information track according to the first invention. FIG. 4 is a schematic diagram showing a positional relationship, FIG. 4 is an enlarged conceptual view of an information track for showing a relationship between an information track of the optical disk device according to the first invention and a defocus signal of each light spot, and FIG. FIG. 6 is a diagram showing the subsequent defocus signal, and FIG. 6 is a schematic diagram showing the defocus signal at the time of track access of the optical disc device in the first invention. In the figure, the same or corresponding parts as those of the conventional device are designated by the same reference numerals and the description thereof will be omitted.

In the figure, 120 is two light beams 121a,
The semiconductor lasers 121a and 122b for emitting 121b are light spots obtained by condensing the light beams 121a and 121b by the objective lens 106, respectively, and as shown in FIG.
Are arranged at a distance of Pd / 2 which is half the track pitch Pd of the information tracks on the optical disc 101. 123 is a light spot 122a, 12 for the optical disc 101
A defocus detection optical element including a cylindrical lens or the like for detecting the defocus amount of 2b, and 124 is a photodetector that receives the reflected light from the optical spots 122a and 122b on the optical disc 101 and generates a defocus signal. Patterns 124a, 124b
And a photodetector unit composed of differential amplifiers 124c and 124d. Reference numeral 125 denotes an optical head device section including a semiconductor laser 120, an objective lens 106, a photodetector section 124 and the like.
Reference numeral 126 is an adder for adding the focus shift signals obtained from the photodetector section 124, and 127 is a focus control circuit.

Next, the operation will be described. First, it is assumed that the light spots 122a and 122b have the same intensity. As shown in FIG. 4, when the light spots 122a and 122b cross the information track, the groove interference signals 128a and 128b observed in the defocus signals obtained from the respective light spots 122a and 122b are
On the time axis, the phases appear as waveforms whose phases are shifted by 180 ° and which have the same amplitude. This is because one period of the groove interference signal corresponds to the interval of the information tracks, and the light spots 122a and 122b are
This is because the relative positional deviation (tracking deviation) in the direction perpendicular to the information track is half the information track interval. Therefore, by adding the defocus signals obtained from the photodetector section 124 by the adder 126, the defocus signal from which the groove interference signal has been removed is obtained at the output of the adder 126 as shown in FIG. Will be done. Therefore, as shown in FIG. 6, the groove interference signal is not superposed on the defocus signal at the time of track access, and noise does not appear in the defocus signal even at the T2 region at the time of information track access.

FIG. 7 is a schematic view showing a part of the optical disk device according to the second invention, and FIG. 8 is a schematic view showing the arrangement relationship of the light spot rows on the information track according to the second invention. The same or corresponding parts as those of the conventional device or the embodiment of the first invention are designated by the same reference numerals and the description thereof will be omitted. In the figure, 14
0 is a semiconductor laser that emits three or more light beams, 141
a, 141b, 141c, 141d, and 141e are light beams emitted from the semiconductor laser 140, and 142a, 142b, 142c, 142d, and 142e are light beams 141a, 141b, 141c, 141d, and 141e, respectively, which are condensed by the objective lens 106. Optical spot 10
They are arranged at a distance of Pd / 2, which is half the track pitch Pd of the information track above 1. 143 separates the light beams 141a, 141b, 141c, 141d, 141e, and also light spots 142a, 142b, 142 on the optical disc 101.
An optical element for detecting defocus, which includes a cylindrical lens or the like for detecting the amount of defocus of c, 142d, and 142e, 144
Is a light detector unit, and the light beams 141a, 141b, 141c, 141
144, which is a photodetector pattern for receiving d and 141e
It is composed of a, 144b, 144c, 144d, 144e and a differential amplifier (not shown).

In the embodiment shown in FIGS. 7 and 8, the light spots 141a, 14 condensed on the land portion of the information track.
1c and 141e enable parallel recording / reproduction of information. Further, in the light spots 141a, 141c, 141e focused on the land portion of the information track and the light spots 141b, 141d focused on the groove portion, the observed groove interference signals have a phase difference of 180 °. Therefore, the defocus signal output obtained from the light spot focused on the land and the defocus signal output obtained from the light spot focused on the groove are selectively calculated by the arithmetic processing circuit 145. The groove interference signal can be removed from the defocus signal.

FIG. 9 is a schematic view showing a part of the optical disk device in the third invention, and FIG. 10 is a schematic view showing the arrangement relationship of the light spot rows on the information track in the third invention. In the figure, parts that are the same as or correspond to those of the conventional device and the above-described embodiment are assigned the same reference numerals and description thereof is omitted. In FIG. 9, 150 is a diffraction grating for dividing the light beam 103 emitted from the semiconductor laser 102 into a plurality of light beams 151a, 151b, 151c, and 152a, 152b, 152c are light beams 151a, 151b, 151c.
10 are light spots condensed by the objective lens 106, respectively, and are arranged at a distance of Pd / 2, which is half the track pitch Pd of the information tracks on the optical disc 101, as shown in FIG. 153 is a light beam 151a, 151b,
An optical element for defocus detection including a cylindrical lens or the like for separating the 151c and detecting the defocus amount of the light spots 152a, 152b, 152c with respect to the optical disc 101, 154 is a photodetector unit, and the light beams 151a, 151b , 15
154a, 154 which are the photodetector patterns for receiving 1c
It is composed of b, 154c and a differential amplifier.

In the embodiment shown in FIGS. 9 and 10, the observed groove interference occurs between the light spot 152b focused on the land portion of the information track and the light spots 152a and 152c focused on the groove portions. The signals are 180 ° out of phase. Therefore, the output of the photodetector unit 154 is calculated by the arithmetic processing circuit 145 according to the light quantity ratio of each light spot 152a, 152b, 152c determined by the shape of the diffraction grating and the groove interference signal is removed from the defocus signal. can do. The distance between the light spots 152a, 152b, 152c is set according to the shape of the diffraction grating. Also, the light spot 15 for the information track
The relative arrangement of 2a, 152b, and 152c is finely adjusted by rotating and adjusting the diffraction grating.

FIG. 11 is a schematic view showing a part of the optical disk device according to the fourth invention, and FIG. 12 is a detailed view showing the photodetector section in FIG. 11 according to the fourth invention. In the figure, parts that are the same as or correspond to those of the conventional device and the above-described embodiment are assigned the same reference numerals and explanations thereof are omitted. In FIG. 11, reference numeral 160 denotes a photodetector unit, which is composed of photodetectors 161, 162, 163 for receiving the light beams 151a, 151b, 151c, and a differential amplifier (not shown). . 161a ~ 161d, 162a ~
Reference numerals 162d, 163a to 163d denote photodetector division patterns of the photodetectors 161, 162, 163, respectively.

As shown in FIG. 12, the photodetectors 161, 162,
Each of the 163 photodetector division patterns is divided into four, and 161a to 16
1d, 162a to 162d, 163a to 163d, an appropriate coefficient G is selected, and according to formula (8), the method disclosed in JP-A-61-94
According to the so-called differential push-pull method described in Japanese Patent No. 246, the track deviation of the light spots 152a, 152b, 152c with respect to the information tracks on the optical disc 101 can be detected, and an appropriate coefficient K is selected, and the equation (9) is used. , Optical spots 152a, 15 for information tracks on the optical disc 101
The defocus signals of 2b and 152c can be detected. Track shift signal = (162a + 162b-162c-162d) -G (161a + 161b-161c-161d + 163a + 163b-163c-163d) ... (8) Focus shift signal = (162a-162b-162c + 162d) -K (161a-161b-161c + 161d + 163a-163b- 163c + 163d)… (9)

FIG. 13 is a schematic view showing a part of an optical disk device according to the fifth aspect of the invention, and FIG. 14 is a schematic view showing the positional relationship of light spot rows on an information track in the fifth aspect of the invention. In the figure, parts that are the same as or correspond to those of the conventional device and the above-described embodiment are assigned the same reference numerals and explanations thereof are omitted. In FIG. 13, reference numeral 150 denotes a diffraction grating that divides the light beam 103 emitted from the semiconductor laser 102 into a plurality of light beams 151a, 151b, 151c, which are rotatably supported in a plane perpendicular to the light beam 103. ing. 170a and 170b are diffraction gratings 15
0 is a drive coil for rotationally driving 0 in a plane perpendicular to the light beam 103, and at the time of tracking, the light spots 152a, 152b, 152c are the optical discs as shown in FIG.
The information tracks 101 are arranged at a distance of each track pitch Pd.

As shown in FIG. 14, in the tracking such as recording / reproducing, the light spots 152a, 152b, 152c are arranged so that the light spots 152a, 152b, 152c are arranged at a distance of the track pitch Pd and the light spot 152a, When the angle formed by the light spot array consisting of 152b and 152c is θ1, parallel recording / reproduction is possible. When accessing the information track, the diffraction grating 150 is rotated by the drive coils 170a and 170b to rotate the light spot array on the information track, and the angle formed by the extension direction of the information track and the light spot array is changed from θ1 to θ2. Change. By doing so, as shown in FIG. 10, the light spots 152a, 152b, 152c are arranged at a distance of Pd / 2, which is half the track pitch Pd. At the time of access, the output of the photodetector unit 154 can be calculated by the calculation processing circuit 145 to remove the groove interference signal from the defocus signal.

FIG. 15 is a schematic view showing a part of the optical disk device in the sixth invention, and FIG. 16 is an optical path diagram showing details of the optical path of the dove prism portion in FIG. 15 in the sixth invention. In the figure, parts that are the same as or correspond to those of the conventional device and the above-described embodiment are assigned the same reference numerals and explanations thereof are omitted. In FIG. 15, 180 denotes the light beam 15 split by the diffraction grating 150.
Dove prism that converts the optical path relationship of 1a, 151b, 151c,
Reference numerals 181a and 181b are drive coils for rotationally driving the dove prism 180 in a plane perpendicular to the light beam 103.

In this embodiment, as shown in FIG.
Light spot 152a during tracking such as recording / playback
The extension direction of the information track and the light spot so that 152b and 152c are arranged at a distance of each track pitch Pd.
The angle formed by the light spot array consisting of 152a, 152b, and 152c is θ
It is set to 1, and parallel recording / reproduction is possible. Then, as shown in FIG. 10, when accessing the information track, the dove prism 180 is rotated by the drive coils 181a and 181b to rotate the optical spot train on the information track,
The angle between the extension direction of the information track and the light spot row is θ
Change from 1 to θ2. By doing so, as shown in FIG. 10, the light spots 152a, 152b, 152c are arranged at a distance of Pd / 2 which is half the track pitch Pd in the direction perpendicular to the tracks. Light detector 6 during access
The output of 0 can be calculated by the calculation processing circuit 145 to remove the groove interference signal from the defocus signal.

FIG. 17 shows an optical disk device 2 according to the seventh invention.
FIG. 18 is a plan view showing the split photodetector, and FIG. 18 is a partially enlarged view of the split band. In FIG. 17, 218 is a two-division photodetector, 21
Reference numerals 6 and 217 are light receiving surfaces of the two-divided photodetector 218. Here, the constituent elements of the optical disk device other than the two-divided photodetector 218 are the same as those of the conventional example shown in FIG. 70, and if the two-divided photodetector 209 in the conventional example is replaced with the above-mentioned two-divided photodetector 218. The optical disk device of this embodiment can be constructed. Reference numeral 219 denotes a divided band in which the light receiving surfaces 216 and 217 face each other, and the longitudinal direction of the divided band (y direction in FIG. 17) is substantially coincident with the tangential direction of the upper edge 208 of the shielding plate. As shown in FIG. 18, the end portions of the light receiving surface in the divided band 219 have a substantially triangular wave shape, and the end portions of the two light receiving surfaces 216 and 217 mesh with each other. Reference numeral 231 shown in FIG. 18 is a dividing line that forms a boundary between the two light receiving surfaces 216 and 217, and changes in a substantially triangular wave shape in the y direction. here,
d ₂ is the width of the divided band 219, and P is the pitch of the triangular wave portions in the divided band 219.

FIG. 19 shows a parting line 231 according to the seventh invention. It is assumed that the width of the parting line 231 is narrow enough to be ignored, and the origin of the yz coordinate system is set at the center of the parting band 219. Is shown. As you can see from Figure 19, the dividing line
_{231, y = (P / d 2} ) z + 2nP y = - (P / d 2) z + (2n-1) P _{where, -d 2/2 ≦ z ≦} d 2/2, n: represent an integer To be done.

The operation of the embodiment shown in FIG. 17 will now be described with reference to FIGS. 70 to 76 used for explaining the conventional example.
explain. However, in these figures, the two-segment photodetector 20
Consider the case where 9 is replaced by the two-segment photodetector 218. Further, the assumption here is that the pitch P of the triangular wave portion is negligibly smaller than the size of the focused spot on the two-divided photodetector 218. The operation of the optical disk device using the two-divided photodetector 218 is almost the same as the conventional example, but a brief description will be given below.

As shown in FIGS. 71 and 72, when the focal point of the outgoing light beam E is located on the optical disc 206, the reflected light beam R1 is located on the two-division photodetector 218, and
The condensing point of the reflected light beam R1 is located on the divided band 219 and the light receiving surface 21
The position of the two-divided photodetector 218 is adjusted so that the output currents S1 and S2 from 6, 217 become equal.

Next, when the optical disk 206 approaches the objective lens 205, as shown in FIG. 73, the reflected light beam R1 is incident on the two-split photodetector 218 before being condensed. Therefore, the figure
As shown by 74, most of the reflected light flux R1 is incident on the light receiving surface 216, and is hardly incident on the light receiving surface 217. On the contrary, if the distance between the optical disc 206 and the objective lens 205 increases,
As shown by 75, the reflected light beam R1 is condensed before the two-divided photodetector 209. Therefore, as shown in FIG.
Most of 1 is incident on the light receiving surface 217, and is hardly incident on the light receiving surface 216.

Since the light receiving surfaces 216 and 217 on which the reflected light beam R1 is incident generate output currents S1 and S2 which are proportional to the respective light receiving amounts, the focus error signal FES can be obtained by taking the difference between S1 and S2. . This is because, as shown in FIGS. 71 and 72, the distance between the optical disc 206 and the objective lens 205 is proper, and the converging point of the outgoing light flux E is just the optical disc 206.
This is because the difference between S1 and S2 is zero when it is located above. In addition, as shown in FIG. 73 and FIG.
Negative (or positive) when the distance between 206 and the objective lens 205 is too short, and positive (or negative) when the distance between the optical disc 206 and the objective lens 205 is too long as shown in FIGS. 75 and 76. It is because The focus error signal FES thus obtained is supplied to the objective lens actuator (not shown) through the phase corrector and the amplifier, so that the focal point of the emitted light beam E is always kept on the optical disc 206. Is the same as the conventional example.

Next, referring to FIG. 19, this two-division photodetector 21
Consider the linear zone of an optical disk device using 8. Now, of the luminous fluxes incident on the two-split photodetector 218, y
= Y ₂ (y ₁ is an arbitrary _{value), z = z 1 (-d} 2/2 ≦ z
₁ ≦ d _2/2) radius w (w around the think portions sufficiently small) compared to d _2. Assuming that P is sufficiently smaller than w, (2 / d ₂ + z
₁ ) / d ₂ hits the light receiving surface 216, and (2 / d ₂ −z ₁ ) /
Since d ₂ hits the light-receiving surface 217, the output currents S1 and S2 of the light-receiving surfaces 216 and 217 are divided into zones of the partial light flux coordinate z ₁ .
It changes linearly within 219. That is, the sensitivity distributions of the light receiving surfaces 216 and 217 are the same as in FIG. Therefore, the two-part photodetector 21
It has been shown that increasing the width of the eight division bands 219 can be equivalent to increasing the width of the division line 209a of the two-division photodetector 209 shown in the conventional example. Therefore, the linear zone can be expanded by increasing the width of the divided band 219. Further, since it is not necessary to widen the width of the dividing line 231 of the two-divided photodetector 218, the frequency characteristic of the two-divided photodetector 218 is not deteriorated.

Next, the ninth and tenth inventions will be described. In an actual two-divided photodetector, the width d ₂ of the divided band 219 cannot be less than a certain width due to the limitation of the manufacturing process.
The pitch P of the sawtooth or triangular wave portion cannot be set below a certain value. Therefore, the convergence angle α (FIG. 73) of the reflected light flux R incident on the two-divided photodetector 218 is set so that the diameter of the focused spot on the two-divided photodetector 218 becomes sufficiently larger than the pitch P.
, That is, the numerical aperture NA ₁ (NA ₁ = sin α) must be set. When exactly half of the reflected light flux R is shielded by the shield plate 207 and the other half is incident on the two-divided photodetector 218 as R1, and the converging point of the outgoing light flux E is located exactly on the optical disc 206. The spot diameter 2w _y in the direction parallel to the divided band 219 (the y direction) (the diameter at which the light intensity is initially zero) 2w _y is given by 2w _y = 1.22 λ / NA ₁ (FIG. 20).

Here, assuming that the value of the pitch P is constant, the focus error signal is calculated for some values of NA ₁ of the reflected light flux (that is, some values of 2w _y ). As shown in FIG. 21, when NA ₁ is large, the displacement of the focused spot in the y direction affects the focus error signal. However, when NA ₁ is smaller than NAa = 5λ / 8P, the focused spot in the y direction. The influence of the position deviation on the focus error signal is very small. Further, when NA ₁ is smaller than NAa = λ / 2P, the focus error signal does not change even if the focused spot is displaced in the y direction. Pitch P is 15μ
m, and the wavelength λ of the light source is 0.78 μm, this NAa is 0.026, and the spot diameter 2w _{y in the} y direction is 36.
It becomes 6 μm. Figure 22 is given to the NA ₁ to 0.026, the pitch P of the divided band set 15 [mu] m, the width d ₂ of the divided band 88 .mu.m, NA of the objective lens showed focus error signal in the case of 0.53 Is. As can be seen from FIG. 22, a linear zone of 5 to 6 μm is obtained.

FIG. 23 shows an optical disk device 2 according to the eleventh invention.
It is a top view which shows a split photodetector. In the above-mentioned embodiment, the shape of the divided band 219 is a triangular wave as shown in FIG.
A configuration as shown in FIG. 23 may be used. In FIG. 23, 220 is a two-divided photodetector, and 221 and 222 are light receiving surfaces, which correspond to the light receiving surfaces 216 and 217 of the embodiment shown in FIG. 223 is a minute light receiving surface arranged in the divided band 219, and its area is 2
It is sufficiently smaller than the focused spot diameter on the split photodetector.
There are a plurality of minute light receiving surfaces in the divided band 219, and they are connected by a connecting line 224. Connection line 224 is also divided into 21
There are a plurality of light receiving surfaces 221 and 222 with an interval of approximately P.
To extend in a direction (z direction in the drawing) that crosses the division band. Then, the connecting line extending from the light receiving surface 221 and the light receiving surface 222
The connecting lines extending from the light receiving surface 222 extend in front of the light receiving surface 222.
The connection line extending from the light receiving surface 222, on the contrary, extends to the front side of the light receiving surface 221 and does not reach the light receiving surface 221. Further, the minute light receiving surface 223 connected by the single connecting line 224 is the light receiving surface 221 or the electrically connected light receiving surface 221.
The area is reduced in proportion to the distance from 222, and in the vicinity of the center of the divided band 219, the minute light receiving surfaces 223 having substantially the same area are arranged in the y direction. Light receiving surface
In the vicinity of 221 or 222, the area of the minute light receiving surface 223 naturally becomes maximum or minimum.

The two-division photodetector 220 shown in FIG. 23 is different from the two-division photodetector 218 shown in FIG. 17 in that the minute light receiving surface 223 in the division band 219 is connected by the connection line 224. The basic operation is the same. For example, two-segment photodetector 220
Considering the partial luminous flux incident on the center line (coordinate z = 0) of the divided band 219 among the luminous flux incident on the light receiving surface 221, almost half of this is a minute light receiving surface connected to the light receiving surface 221. The light is incident on the group, and the other half is incident on the minute light receiving surface group connected to the light receiving surface 222. In this case, the output currents from the light receiving surfaces 221 and 222 are substantially equal. In addition, considering the portion of incidence on the line (z = z ₁ ) between the center line and the light-receiving surface 221, a small amount connected to the light-receiving surface 221 in proportion to the distance from the center line (here, z ₁ ). The amount of light incident on the light receiving surface group increases, and the amount of light incident on the minute light receiving surface group connected to the light receiving surface 222 decreases. Therefore, the light receiving surface 22
The output current (sensitivity) for each unit light amount of 1, 222 has the same change as the sensitivity distribution shown in FIG. 96 with respect to the incident point z ₁ of the partial light flux. The area of the region where the light receiving surface does not exist in the divided band 219 is smaller than that of the conventional two-divided photodetector, and the width of the division line of the two-divided photodetector shown in the conventional example is increased. Obtained sensitivity distribution (Fig. 96)
Therefore, it is possible to obtain an optical disk device having a wide linear zone and no deterioration in frequency characteristics.

By the way, in FIG. 23, the minute light-receiving surface 223 in the divided band 219 is circular, but if the area changes substantially in proportion to the distance from the light-receiving surfaces 221 and 222, its shape is It can be set arbitrarily.

In the embodiment shown in FIGS. 17 and 23, the division band 21
Although the light receiving surface in 9 extends in a direction (z direction) perpendicular to the divided band 219, the structure shown in FIG. 24 may be used. In this embodiment, a plurality of rectangular light-receiving surfaces 225 and 226 are arranged in the divided band 219, and the light-receiving surface 221 or
Connected to either 222. The long sides of the rectangular light receiving surfaces 225 and 226 are the y direction, and the light receiving surface 221
The rectangular light receiving surfaces 225 and the rectangular light receiving surfaces 226 connected to and are arranged alternately in a comb shape. In addition, the rectangular light receiving surface 225 or 226 is the light receiving surface 22
The length of the short side is reduced in proportion to the distance from 1,222. Of course, the width of the dividing line separating the light receiving surface and the light receiving surface is set to be sufficiently narrow. Also in this embodiment, a large number of rectangular light receiving surfaces are arranged in the divided band 219,
The length of each short side (width in the z direction) is divided into two photodetectors
If it is sufficiently smaller than the spot diameter above 220, Fig. 17, Fig.
Obviously, it operates similarly to the embodiment shown in FIG. Therefore, by using the two-divided photodetector 220, it is possible to obtain an optical disk device having a wide linear zone and no deterioration in frequency characteristics. In FIG. 24, although the total number of the rectangular light receiving surfaces 225, 226 in the divided band 219 is 8, the rectangular light receiving surfaces 225, 226
The number of the short sides of 226 is arbitrary as long as it is sufficiently smaller than the spot diameter on the two-divided photodetector 220.

In the above description, the present invention is applied to the optical disk device of the optical recording / reproducing apparatus, but it goes without saying that the present invention can also be applied to the optical disk device such as an autofocus camera.

Next, the thirteenth to twenty-first inventions will be described. Figure
Reference numeral 25 is a block diagram showing the optical disk device in this embodiment. 26 to 31 show the relationship between the defocused state of the light spot on the information recording surface and the position and shape of the light spot on the photodetector of the present optical disk device. In FIG. 25, reference numerals 301 to 308 and 320 to 323 are the same as those in the conventional example shown in FIG. Reference numeral 324 is a light beam splitting element for splitting the light beam R reflected from the optical disk 305 into two or more light beams, and a diffraction grating is formed on a substantially half surface thereof. In the light beam splitting element 324, 341 is a diffraction grating section in which a diffraction grating is formed, and 342 is a non-diffraction grating section without a diffraction grating. Furthermore, the boundary line between the diffraction grating portion 341 and the non-diffraction grating portion 342 is arranged so as to geometrically divide the reflected light flux R into two substantially equal parts. In the figure, two beams, a light beam Ra from the non-diffraction grating unit 342 and a light beam Rb from the diffraction grating unit 341, are shown. However, when two or more light beams are generated by the diffraction action of the diffraction grating unit 341, The splitting element 324 splits the reflected light flux R into three or more light fluxes.

Reference numeral 325 denotes a two-divided photodetector that receives the light beam Ra, and is composed of two light-receiving surfaces 326 and 327 arranged in a plane perpendicular to the optical axis A. Reference numeral 328 is a focused spot on the two-divided photodetector 325. Reference numeral 329 is a two-divided photodetector that receives the light flux Rb, and is composed of two light-receiving surfaces 330 and 331 arranged in a plane perpendicular to the optical axis A. 332 is a focused spot on the two-divided photodetector 329. The direction of the dividing line between the light-receiving surface 326 and the light-receiving surface 327 and the direction of the dividing line between the light-receiving surface 330 and the light-receiving surface 331 are the diffraction grating portion 341 and the non-diffraction grating portion of the light beam splitting element 324.
It almost coincides with the direction of the boundary line between 342 and 342 (y direction).

Next, FESa is a focus error signal obtained from the two-division photodetector 325, and represents the difference between the output signal from the light receiving surface 326 and the output signal from the light receiving surface 327. Similarly,
FESb is a focus error signal obtained from the two-division photodetector 329, and represents the difference between the output signal from the light receiving surface 330 and the output signal from the light receiving surface 331. 337 and 338 are differential amplifiers for obtaining these focus error signals FESa and FESb.
The focus error signals FESa and FESb are added by the adder 340 to form the focus error signal FES.

Next, the operation of the embodiment shown in FIG. 25 will be described with reference to FIGS. When recording / reproducing information, the emitted light beam E emitted from the light source 301 becomes a parallel light beam by the collimator lens 302, is reflected by the beam splitter 303, and travels toward the objective lens 304. next,
The emitted light flux E is condensed by the objective lens 304 and the information recording surface
It is irradiated as a focused spot 306 on 323. And
The reflected light flux R reflected by the information recording surface 323 is the objective lens 30.
4. It passes through the beam splitter 303 and becomes a focused light beam by the focusing lens 308. Next, this light flux R enters the light beam splitting element 324, and the light flux Ra having a semicircular cross section which has entered the non-diffraction grating portion 342 advances straight as it is to the two-divided photodetector 325. Further, the light beam Rb having a semicircular cross section which is incident on the diffraction grating portion 341 is deflected by the diffraction action of the diffraction grating portion and is directed to the two-part photodetector 329.

As shown in FIGS. 26 and 27, when the focused spot 306 of the outgoing luminous flux E is located on the information recording medium surface 323 of the optical disc 305, the focused spot 328 of the luminous flux Ra is 2.
The position of the two-divided photodetector 325 is adjusted so that it is located on the divided photodetector 325 and that the focused spot 328 is located on the dividing line between the light receiving surfaces 326 and 327. At the same time, the focused spot 332 of the luminous flux Rb is divided into two photodetectors 32.
The position of the two-divided photodetector 329 is also adjusted so that it is located on the above-mentioned position 9 and the focused spot 332 is located on the dividing line between the light receiving surfaces 330 and 331. The converging spot referred to here is a state in which the focused light flux is narrowed down to a minimum. Therefore, when the condensing spot 306 of the outgoing luminous flux E is located on the information recording surface 323, the light amounts incident on the light receiving surfaces 326 and 327 become equal, and the outputs from the light receiving surfaces 326 and 327 also become equal. At the same time, the amounts of light incident on the light receiving surfaces 330 and 331 also become equal, so the outputs from the light receiving surfaces 330 and 331 also become equal. Therefore, the focus error signals FESa and FESb are both zero, and the focus error signal FES, which is the sum of these FESa and FESb, is also zero.

Next, consider a case where the optical disc 305 approaches the objective lens 304 by ΔZ. As shown in FIGS. 28 and 29,
Before the light beams Ra and Rb are condensed, they are divided into two photodetectors 325 and 329.
Incident on each of. Therefore, most of the light flux Ra enters the light receiving surface 327 and hardly enters the light receiving surface 326, and at the same time, most of the light flux Rb enters the light receiving surface 330 and hardly enters the light receiving surface 331. Since each light receiving surface produces an output proportional to the amount of light received,
The output of 327 becomes larger than the output of the light receiving surface 326, and the focus error signal FESa, which is the difference between them, becomes positive. Similarly, the focus error signal F which is the difference between the output of the light receiving surface 330 and the light receiving surface 331.
ESb also becomes positive. Therefore, these FESa and FESb
The focus error signal FES, which is the sum of the two, becomes positive.

On the contrary, if the distance between the optical disk 305 and the objective lens 304 is increased by ΔZ, the light beams Ra and Rb are condensed before the two-divided photodetectors 325 and 329, respectively, as shown in FIGS. To do. Therefore, most of the light flux Ra is incident on the light receiving surface 326 and hardly enters the light receiving surface 327, and at the same time, most of the reflected light flux Rb is incident on the light receiving surface 331.
Almost no incident on 330. Since each light receiving surface produces an output proportional to the amount of light received, the light receiving surface 327
Is smaller than the output of the light-receiving surface 326, and the difference between them is the focus error signal FESa, which is negative. Similarly, the focus error signal FE, which is the difference between the output of the light receiving surface 330 and the light receiving surface 331,
Sb also becomes negative. Therefore, the focus error signal FES, which is the sum of these FESa and FESb, also becomes negative.

In summary, the distance between the optical disk 305 and the objective lens 304 is proper, and the converging spot 30 of the outgoing light beam E is 30.
When 6 is located exactly on the information recording surface 323, the focus error signal FES becomes zero. Further, it is positive when the distance between the optical disk 305 and the objective lens 304 is too short, and is negative when the distance between the optical disk 305 and the objective lens 304 is too long. FIG. 32 shows the defocus Δf (Δf is the focused spot 30
6 and the information recording surface 323) and the focus error signal F
It is a figure which shows the relationship with ESa and FESb. Finally, the focus error signal FES is supplied to the objective lens driving mechanisms 321 and 322 through the phase corrector / amplifier 320, and the emitted light beam E
It is the same as the conventional example that the focused spot 306 is always kept on the information recording surface 323.

As described above, the boundary line between the diffraction grating portion 341 and the non-diffraction grating portion 342 of the light beam splitting element 324 has the same function as that of the roof 310 of the roof prism 309 in the conventional example. In the embodiment, the direction of the boundary line between the diffraction grating portion 341 and the non-diffraction grating portion 342 is the optical disc 305.
The guide groove 307 is set in a direction (y direction) substantially orthogonal to the tangential direction (x direction). This is similar to the conventional example in that the light spot 306 is the guide groove 30 of the optical disk 305.
This is to keep the disturbance appearing in the focus error signal FES as small as possible when crossing 7.

In addition, in this embodiment, the diffraction grating portion 342
If the structure of the diffraction grating is determined so as to diffract most of the light beams that are incident on it, and if multiple two-split photodetectors are prepared to receive all the diffracted light beams, the light beams that enter the light beam splitting element 324 Almost 100% of that can be used for focus error signal generation, and an efficient optical disk device can be configured. Further, if the diffraction grating portion 341 is configured so that the grating period of the diffraction grating is constant and the grating line is substantially orthogonal to the boundary line, the two-divided photodetector 329 on the two-division photodetector 329 with respect to the wavelength fluctuation of the light source 301. Since the light spot only moves on the division line, no offset is generated in the focus error signal FESb and thus in FES. At this time, the two-split photo detector 325
The dividing line of 2 and the dividing line of the two-divided photodetector 329 are substantially aligned.

By the way, two two-divided photodetectors 325 and 329 are provided to obtain the focus error signal FES.
This is because when two two-divided photodetectors are housed in one package, the offset in the focus error signal that occurs when they are displaced in the direction perpendicular to the division line (x direction in FIG. 25) can be reduced. . Here, it is clear from FIG. 25 that the shift in the y direction does not affect the offset. The reason why the offset can be suppressed with respect to the shift of the two-divided photodetector in the x direction is as follows. As shown in FIGS. 26 and 27, when the focused spot 306 of the outgoing light beam E is located on the information recording medium surface 323 of the optical disc 305, the light receiving surface 32
The positions of the two-divided photodetectors 325 and 329 are adjusted so that the outputs from the 6 and 327 are equal and the outputs from the light receiving surfaces 330 and 331 are also equal. Considering the case where the two-divided photodetectors 325 and 329 move in the x direction by the same distance, the light receiving surface 326
And the output of the light receiving surface 330 increases, and the light receiving surface 327 and the light receiving surface 330
Since the output of 331 decreases, FESa decreases and FESb decreases.
To increase. Therefore, if the characteristics of FESa and FESb are the same, FES, which is the sum of FESa and FESb, does not change. Even if the characteristics of FESa and FESb are not exactly the same, the two focus error signals FESa and FE
Since the signs of the offsets appearing in Sb are opposite to each other, the appearance of the offset of the focus error signal FES, which is the sum of them, can be made smaller than the focus error signals FESa and FESb.

The following three points can be cited as advantages of using the light beam splitting element 324 described in this embodiment in place of the roof prism 309 in the conventional example. One is the diffraction grating section 34
Since the width of the boundary region between 1 and the non-diffraction grating portion 342 can be made extremely small (for example, 10 μm or less), there is an advantage that the scattering loss in this portion can be suppressed low (hence, this boundary The area is called the borderline). Other advantages are that the positional accuracy of the boundary line of the light beam splitting element 324 can be easily kept to several tens of μm or less and the manufacturing cost of the light beam splitting element can be made lower than that of the roof prism. All of these are alternatives to optical polishing,
This is because optical lithography or etching technology in the semiconductor process or holographic creation technology can be used for manufacturing this light beam splitting element.

The beam splitting element 324 shown in the above embodiment
As shown in FIG. 33, a light beam splitting element 343 whose diffraction grating portion 341 is a plane type diffraction grating can be used. FIG. 33 shows a diffraction grating having a rectangular groove in which the refractive index of the substrate is n, the groove depth is h, the period is p _G , and the groove width is a.
The groove of this diffraction grating is a straight line with a constant period p _G, and the boundary line between the diffraction grating portion 341 and the non-diffraction grating portion 342 is a substantially straight line. Moreover, the direction of the groove and the direction of the boundary line are substantially orthogonal to each other.

The groove depth h and groove width a of this diffraction grating are: h = λ / {2 (n-1)} (10) a = p _G /, where λ is the wavelength of the light source used. 2 (11) The above conditions are selected so that they are almost satisfied. This corresponds to that the diffraction grating applies a phase modulation with a duty of 50% and a depth of 180 degrees to the incident light beam. Assuming that there is no Fresnel loss on each of the front surface and the back surface of the light beam splitting element 343, the light flux of 40.
5% is diffracted as the 1st-order diffracted light and 40.5% is diffracted as the minus 1st-order diffracted light, and the 0th-order diffracted light is not generated. The remaining 20% is odd-order diffracted light of the third order or higher.

FIG. 34 is a block diagram showing an optical disk device according to another embodiment of the thirteenth to twenty-first inventions. 35 to 37 show the relationship between the defocused state of the light spot on the information recording surface and the position and shape of the light spot on the photodetector of the present optical disc apparatus. In FIG. 34, 301-308, 320-32
3, 325 to 338, 341 and 342 are the same as those in the embodiment shown in FIG. Reference numeral 343 denotes a light beam splitting element that splits the reflected light beam R from the optical disc 305 into three light beams Ra, Rb, and Rc. The boundary line between the diffraction grating portion 341 and the non-diffraction grating portion 342 divides the reflected light beam R into approximately two equal parts. It is arranged to.
Here, Ra is a light beam that has passed through the non-diffraction grating portion 341 as it is, Rb is a light beam diffracted by the diffraction grating portion 342 as plus first-order diffracted light, and Rc is a diffraction grating portion 34.
It is a light beam diffracted by 2 as a minus first-order diffracted light in the direction opposite to Rb. The reflected light beam R to the light beam splitting element 343 is a circular beam having a uniform intensity distribution, and the boundary line between the diffraction grating portion 341 and the non-diffraction grating portion 342 of the light beam splitting element 343 divides this circular beam into two equal parts. Considering the case, 50% of the beam becomes the light beam Ra, 20.25% becomes the light beam Rb, and 20.25% becomes the light beam Rc.

The remaining 9.5% of the beam is deflected at a larger angle as higher order diffracted light, so it cannot be incident on the photodetector in FIG. However, it is easy to prepare a photodetector for receiving these high-order diffracted lights. Therefore, when using three light fluxes of Ra, Rb, and Rc, about 90% of the light flux entering the light beam splitting element 343 can be used for generating the focus error signal.
If the diffracted light of the order or more is also used, about 100% of the light beam incident on the light beam splitting element 343 can be used for generating the focus error signal. 34, in addition to the two-split photodetector 325 that receives the light flux Ra and the two-split photodetector 329 that receives the light flux Rb, the two-split photodetector 333 that receives the light flux Rc is shown in FIG. Has been done. 2-split photodetector 33
3 is two light-receiving surfaces 33 arranged in a plane perpendicular to the optical axis A
It is composed of 4, 335, and 336 is a two-part photodetector 333.
It is the upper light spot.

The direction of the dividing line between the light receiving surfaces 334 and 335 is also
Diffraction grating portion 341 and non-diffraction grating portion 342 of beam splitting element 343
It is almost coincident with the direction of the boundary line between the and (the y direction), and the respective dividing lines of these three two-divided photodetectors 325, 329, 333 are almost lined up on one straight line 347. There is. FESa and FESb are two-segment photodetectors 325,
The focus error signal obtained from 329 is the same as in the embodiment shown in FIG. FESc is a focus error signal obtained from the two-division photodetector 333, and represents the difference between the output signal from the light receiving surface 334 and the output signal from the light receiving surface 335. 339
Is a differential amplifier for obtaining these focus error signals FESc. The focus error signals FESa, FESb, FESc are added by the adder 344, and the focus error signals FE
It becomes S.

Next, the operation of the embodiment shown in FIG. 34 will be described with reference to FIGS. When recording / reproducing information, the emitted light flux E emitted from the light emitting source 301
Is collimated by the collimator lens 302, is reflected by the beam splitter 303, and travels toward the objective lens 304. The emitted light beam E is condensed by the objective lens 304 and the information recording surface 32
It is irradiated as a converging spot 306 on the upper side. Then, the reflected light flux R reflected by the information recording surface 323 is the objective lens 304.
, Passes through the beam splitter 303, and becomes a focused light beam by the focusing lens 308. Up to this point, the process is the same as in the embodiment shown in FIG. Next, the reflected light flux R is converted into a light flux splitting element 343.
Is divided into three light beams Ra, Rb, Rc by
Is a two-segment photodetector 325, and Rb is a two-segment photodetector 329.
Further, Rc is incident on the two-divided photodetector 333. Figure 34
As shown in, the cross-sectional shape of Ra, Rb, and Rc is a substantially semicircle.

The focus error detecting operation of this embodiment is almost the same as that of the embodiment shown in FIG. 25, except that the light beam Rc is used in the same manner as the light beam Rb. FIG. 35 shows the focused spots 328, 332, 334 on the two-divided photodetectors 325, 329, 333 when the focused spot 306 of the outgoing luminous flux E is located on the information recording surface 323 of the optical disc 305. It shows the state. Since the diffraction grating on the light beam splitting element 343 has a constant grating period and the grating line is linear, the focused light beam incident on the diffraction grating portion is only deflected in the direction perpendicular to the direction of the grating line. Therefore, the converging spots 328, 332, 334 are arranged on one straight line 347. In this case, the light receiving surface 334,
Since the amount of light incident on 335 is also equal, the light receiving surface 334, 335
The output from is also equal. Therefore, the focus error signal FES
c becomes zero like FESa and FESb.
Focus error signal FE, which is the sum of Sa, FESb, and FESc
S also becomes zero.

In FIG. 36, the optical disk 305 is the objective lens 304.
3 shows the respective states of the focused spots 328, 332, 334 on the two-divided photodetectors 325, 329, 333 when ΔZ is approached. At this time, most of the light flux Rc is on the light receiving surface 334.
Since it is incident on the light receiving surface 335 and is almost not incident on the light receiving surface 335, the focus error signal FESc, which is the difference between the output of the light receiving surface 334 and the light receiving surface 335, becomes positive like FESa and FESb, and the sum of FESa, FESb and FESc The focus error signal FES is also positive.

FIG. 37 shows a two-division photodetector 325, 32 when the distance between the optical disk 305 and the objective lens 304 is ΔZ.
The respective states of the focused spots 328, 332, 334 on 9, 333 are shown. At this time, most of the light flux Rc is incident on the light receiving surface 335 and is hardly incident on the light receiving surface 334. Therefore, the focus error signal FESc, which is the difference between the output of the light receiving surface 334 and the light receiving surface 335, is FESa and FESb. Similarly, the focus error signal FES, which is the sum of FESa, FESb, and FESc, also becomes negative.

FIG. 38 shows defocus Δf (Δf is a focused spot)
6 is a graph showing the relationship between the focus error signals FESa, FESb, FESc, and FES, which is the distance between 306 and the information recording surface 323). Also, in order to keep the disturbance in the focus error signal FES generated when the light spot 306 crosses the guide groove 307 of the optical disc 305 as small as possible, the direction of the boundary line between the diffraction grating portion 341 and the non-diffraction grating portion 342 is the optical disc 305. The guide groove 307 is set in a direction substantially orthogonal to the tangential direction (x direction).

Three two-divided photodetectors 325, 329, 333 are prepared to obtain the focus error signal FES because the three two-divided photodetectors are housed in one package and are perpendicular to the dividing line. This is because it is possible to reduce the offset in the focus error signal FES that occurs when the focus error signal FES is deviated in the different directions (the x direction in FIG. 25). Here, it is clear from FIG. 34 that the offset in the y direction does not affect the offset. The reason why the offset can be suppressed with respect to the shift of the two-divided photodetector in the x direction is the same as in the embodiment shown in FIG. As shown in FIG. 35, when the focused spot 306 of the outgoing luminous flux E is located on the information recording surface 323 of the optical disc 305, the light receiving surface 326,
The positions of the two-divided photodetectors 325, 329, 333 are adjusted so that the outputs of 327 are the same, the outputs of the light receiving surfaces 330, 331 are also the same, and the outputs of the light receiving surfaces 334, 335 are also the same. .

Considering the case where the two-divided photodetectors 325, 329, 333 move in the x direction by the same distance, the light receiving surfaces 326, 33
Since the output of 0, 334 increases and the output of the light receiving surfaces 327, 331, 335 decreases, FESa decreases and FESb, FESc decrease.
Will increase. Therefore, the sign of the offset of the focus error signal FESa is opposite to the sign of the offset of FESb and FESc, and the sum of them is the focus error signal F.
How the ES offset appears is the focus error signal FESa,
It can be smaller than each of FESb and FESc.

Next, the parameters of the optical components when the embodiment shown in FIG. 34 is applied to a typical optical disk device will be described with reference to FIG. Numerical aperture NA of objective lens 304
obj is 0.55 and the diameter φobj of the entrance pupil of the objective lens is 3
mm, the focal length fobj of the objective lens is 3.3 mm, the focal length fs of the focusing lens is 33 mm, the optical distance d ₃ from the focusing lens 308 to the light beam splitting element 343 is 11 mm, 2
The distance s from the center of the split photodetector 329 (or 333) to the center of the split photodetector 325 is set to 0.3 mm (in this case, the three split photodetectors 325, 329, 333 are Easy to put in the package). These values are the values in the conventional typical optical disk device described above.

The deflection angle θ by the diffraction grating is set so that θ = Arctan {s / (fs-d ₃ )} (12) is satisfied, and the period p _{G of the} diffraction grating is the wavelength λ of the light source. And θ _{3 given} above, p _G = λ / sin θ ₃ (13) If λ is 0.78 μm, θ ₃ and p are θ ₃ = Arctan {0.3 / (33-11) = 13.6 (mrad ₃ ) ... (14) p _G = 0.78 / sin (0) .0136) = 57.2 (μm) (15) Therefore, the groove depth h and the groove width a of the diffraction grating are calculated from the equations (10) and (11) so that h = 0.78 / {2 (1.5-1)} = 0.78 (μm) (16) ) A = 57.2 / 2 = 28.6 (μm) (17) Groove depth 0.78 μm, Groove width 28.6 μm
It is generally extremely easy to manufacture the diffraction grating having the rectangular groove of (3) by a technique such as optical lithography.

Further, consider the case where the wavelength λ of the light source 301 changes. At this time, since the deflection angle θ ₃ changes according to the equation (13), the positions of the focused spots 332 and 336 of the light beams Rb and Rc diffracted on the two-divided photodetectors 329 and 333 change. However, since the three focused spots 328, 332, 336 are originally on one straight line 347, and the dividing lines of the two-divided photodetectors 325, 329, 333 are also on one straight line 347, The focused spots 332 and 336 only move on the dividing line. Further, since the diffraction grating having a constant grating period has no lens effect, the size and shape of the focused spot hardly change. Therefore, it can be said that the fluctuation of the wavelength of the light source 301 has almost no effect on the focus error signal FES.

The case where the diffraction grating portion 341 and the non-diffraction grating portion 342 of the light beam splitting element 343 are transparent has been described.
Of course, these may be reflective.

Although the light beam splitting element 343 is placed in the focused light beam in FIG. 33, it may be placed in the parallel light beam. In this case, the focusing lens 308 is the beam splitting element 343.
And the two-split photodetectors 325, 329, 333.

Further, in FIG. 33, the diffraction grating portion 341 of the light beam splitting element 343 is composed of a plane type diffraction grating having an uneven surface, but it is a refractive index modulation type diffraction grating as shown in FIG. It can also be configured. In the figure, 345 is a region in which the refractive index changes by Δn as compared with the refractive index n of the substrate, the depth of the region is h, the width is a, and the period is p _G. It is desirable that h and a are respectively selected so that h = λ / (2Δn) (18) a = p _G / 2 (19) can be substantially satisfied. This condition is the same as the expressions (10) and (11), and corresponds to the fact that the diffraction grating applies a phase modulation with a duty of 50% and a depth of 180 degrees to the incident light beam.

FIG. 41 is a block diagram showing an optical disk according to the twenty-first aspect of the invention, showing the two-division detectors 325 and 329 shown in FIG.
The two-divided detectors 351 and 352 having the same configuration as the two-divided detector 218 shown in FIG. 17 are replaced. Other configurations are the same as those shown in FIG. 25, and are assigned the same reference numerals and explanations thereof are omitted. In the present embodiment, in addition to the effect in FIG. 25, the range in which the focus error signal changes linearly with respect to defocus can be made wider than that of the conventional Foucault method. There are effects such as less deterioration, less disturbance when traversing the guide groove of the focused spot image optical disk, and less fluctuation of the focus error signal due to lateral displacement of the photodetector.

FIG. 42 is a block diagram showing an optical disk according to the twenty-first aspect of the invention, which is a two-divided detector 325, 329, 333 shown in FIG.
2 has the same configuration as the two-divided detector 218 shown in FIG.
Instead of the split detectors 353, 354, 355. Other configurations are figures
It is similar to that shown in 34, and the same reference numerals are given and the description thereof is omitted. In addition to the effect shown in FIG. 34, the present embodiment has the same effect as the above-mentioned embodiment. The shape of the dividing line is
In addition to the substantially triangular wave shape (or substantially sawtooth shape) shown in FIGS. 41 and 42,
It may be substantially sinusoidal.

Next, the twenty-second to twenty-fourth inventions will be described. Figure 43
Is a first tilt angle adjusting unit of the optical disk device according to the twenty-second invention.
44 is an exploded perspective view showing an embodiment, FIG. 44 is a perspective view of a main part of an optical disk device equipped with the tilt angle adjusting portion of FIG. 43, FIG. 45 is a plan view thereof, and FIG. 46 is a sectional view taken along the line I--I of FIG. , Fig. 47 is II of Fig. 45
It is a sectional view taken along the line II.

In FIG. 43, 420 is an objective lens, 421 is a ring-shaped flat plate (hereinafter referred to as "flat plate"), 422a, 422b.
Is a pair of upper projections provided on the flat plate 421, and the optical axis 408
It is provided on the first straight line L1 passing through. 423a, 423b
Is a pair of lower projections provided on the flat plate 421, and the optical axis 408
It is provided on a second straight line L2 that passes through the first straight line L1 and is orthogonal to the first straight line L1. 424 is an objective lens holder, 425 is a bearing, and 426 is a focusing coil.

In FIGS. 44 to 47, reference numeral 430 denotes a base, which has a light beam passing hole 430a on its side surface so that a light beam 431 emitted from a light source (not shown) can enter from the side surface. A focus base 432 holds the lower end of the support shaft 433 coated with a fluororesin having a small friction coefficient. 434a and 434b are focusing magnets that are vertically magnetized, and are bonded and fixed to the focus base 432 together with the focusing yokes 435a and 435b.
It is fixed to the base 430 by 436b.

Reference numerals 437a and 437b are tracking magnets polarized in the left and right directions, and reference numeral 438 is a launching mirror for vertically reflecting the light beam 431 incident from the side surface. ing. 439
Is a drive current application FPC, 440 is a photo interrupter,
Reference numeral 442 is a photo interrupter fixing plate, and the driving current applying FPC 439 and the photo interrupter 440 are fixed to the base 430 by screws 443 and 444, respectively.

Reference numeral 424 denotes an objective lens holder formed of a lightweight and highly rigid plastic material or the like so that the fin portion 424aa protruding parallel to the support shaft 433 is arranged in the gap portion of the photo interrupter 440. It is provided integrally with the objective lens holder 424. Reference numeral 420 is an objective lens fixed to one end of the objective lens holder 424 in the longitudinal direction, 421 is a flat plate arranged between the objective lens holder 424 and the objective lens 420, and 447 is an objective lens holder 424.
Is a balance weight fixed to one end where the objective lens 420 in the longitudinal direction is not arranged.

Reference numeral 425 is a bearing fixed to the objective lens holder 424 so as to have an axis parallel to the optical axis of the objective lens 420, and is fitted to the support shaft 433. 42
6 is a focusing coil fixed to the objective lens holder 424 so as to be coaxial with the bearing 425,
Focus base 432 and focusing yoke 43 above
It is configured to be placed in the magnetic gap formed by 5a and 435b. Reference numeral 450 denotes a movable part FPC fixed to the objective lens holder 424, and tracking coils 451a and 451b fixed to both side surfaces of the objective lens holder 424 by adhesion.
It has a function of a relay board that connects the two and also supplies a driving current to the focusing coil 426 and the tracking coils 451a and 451b through a lead wire (not shown). The movable portion 453 is constituted by the above 424 to 452d. Reference numerals 454a to 454d denote dampers, which are fixed to the protrusions 455a and 455b provided on the objective lens holder 424 and the pin portions 456a to 456d provided on the base 430, respectively, and the movable portion 45.
3 is slidably and rotatably supported on the support shaft 433. A cover 457 is fixed to the base 430.

Next, the operation will be described. When the tilt adjustment of the objective lens 420 shown in FIG. 43 in the arrow A ₄ direction is performed, the objective lens 420 is tilted in the arrow A ₄ direction about the tips of the upper protrusions 422a and 422b provided on the flat plate 421. Then, a desired force is applied to the objective lens 420 at an appropriate point. When adjusting the tilt of the objective lens 420 in the direction of the arrow B ₄ , similarly, the objective lens 420 is tilted in the direction of the arrow B _{4 about} the tips of the lower protrusions 423a and 423b. On the other hand, a desired force is applied to an appropriate point.

The actual amount of tilt adjustment is 10 mrad (about 0.57 de) in a general optical disk device.
In many cases, adjustment of g) is performed. When the outer diameter of the objective lens 420 is about 5 mm, the protrusion amount of the pair of upper protrusions 422a and 422b and the pair of lower protrusions 423a and 423b necessary for adjusting 10 mrad is about 25 μm. The value has no problem in manufacturing.

After the tilt adjustment of the objective lens 420 is completed,
The flat plate 421 and the objective lens 420 are fixed to the objective lens holder 424 with an adhesive or the like.

The operation for driving the objective lens 420 is as follows.
When correcting the focus shift of the light spot (not shown), a desired current is applied to the focusing coil 426, and the movable portion 45 is moved by the electromagnetic force obtained by the interaction with the magnetic force generated by the focusing magnets 434a and 434b.
3 As a result, the objective lens 420 is driven and controlled in the arrow C ₄ direction shown in FIG. 46, and the focusing direction is controlled.
When correcting the track deviation of the light spot (not shown), a desired current is applied to the tracking coils 451a and 451b, and an electromagnetic force obtained by the interaction with the magnetic force generated by the tracking magnets 437a and 437b is obtained. Thus, the movable portion 453 is rotated about the support shaft 433 in the direction of arrow D ₄ shown in FIG. 45, and the tracking direction of the objective lens 420 is controlled.

FIG. 48 is an exploded perspective view showing an essential part of the second embodiment of the 22nd invention, wherein two of the four projections for giving an inclination angle to the objective lens 420 are objective lens holders 424.
The projections 424b and 424c are provided on the
The same operation as that of the embodiment shown in 43 can be expected.

FIG. 49 is an exploded perspective view showing an essential part of the third embodiment of the 22nd invention. Of four projections for giving an inclination angle to the objective lens 420, two projections are provided on the objective lens 420.
These are provided as 420a and 420b, and this embodiment can be expected to operate in the same manner as the embodiment shown in FIG.

FIG. 50 is an exploded perspective view showing the essential parts of the fourth embodiment of the 22nd invention. Of the four projections for giving an inclination angle to the objective lens 420, two projections are provided on the objective lens 420.
The projections 424b and 424c are provided as the projections 424b and 424c on the objective lens holder 424.
The same operation as the embodiment shown in can be expected.

FIG. 51 is an exploded perspective view showing an essential part of the optical disk device according to the 23rd aspect of the present invention. A flat plate 421 is provided with a tongue piece 421a for restricting rotation in the in-plane direction, and an objective lens holder 424 is provided.
This shows another embodiment in which the notch 424d into which the tongue piece 421a is fitted is provided, and it becomes possible to limit the direction in which the tilt angle of the objective lens 420 is adjusted.

FIG. 52 is an exploded perspective view showing an essential part of the optical disc apparatus according to the 24th aspect of the present invention. The flat plate 421 is provided with a tongue piece 421a for restricting rotation in the in-plane direction, and the objective lens is
The tongue piece 420c for restricting rotation in the in-plane direction is also provided on the 420, and the tongue piece 420c is fitted into the cutout portion 424d provided on the objective lens holder 424, so that the tilt angle adjustment direction of the objective lens 420 is limited. It becomes possible to do.

In each of the above embodiments, the case where the present invention is used for adjusting the inclination of the objective lens has been described, but it is also used for other lenses such as a collimating lens or for an optical system such as a reflecting mirror. It goes without saying that you can do it.

In each of the above-described embodiments, the case where the present invention is used for adjusting the tilt of the objective lens alone has been described. However, the whole objective lens driving device, or the objective lens driving device and the light source unit and the light detecting unit are included. It goes without saying that it can also be used for adjusting the inclination of the entire optical head device.

FIG. 53 is an exploded perspective view of an essential part of an optical disk device according to the twenty-fifth invention, FIG. 54 is a plan view of an essential part of FIG. 53, and FIG.
56 is a cross-sectional view of the main part of FIG. 53, FIG. 56 and FIG. 57 are cross-sectional views of the main part showing the driving state of the optical disk device of FIG. 53 in the focusing direction, and FIG. 58 is a detailed view showing the shape of the leaf spring part of FIG. is there.

In FIGS. 53 to 58, 501 is a base having a light flux passing hole 501a on the bottom surface so that a light beam 502 emitted from a light source (not shown) can enter from the bottom surface. The fixing hole 501b holds the lower end of the support shaft 503. Reference numerals 504a and 504b denote focusing magnets that are vertically magnetized, and are fixed to the base 501 together with the focusing yokes 505a and 505b.

Reference numerals 506a and 506b are tracking magnets which are magnetized in two poles in the left-right direction, and tracking yokes 507a and 507b are provided on the back surface thereof.

Reference numeral 510 denotes a lens holder made of a plastic material, 511 denotes an objective lens fixed to one end of the lens holder 510 in the longitudinal direction, and the light beam 502 is an optical disc.
The light is focused as a focused spot 514 on 512 information recording surfaces 513.

Reference numerals 516a and 516b are a pair of leaf springs having an inner peripheral portion fixed to the support shaft 503 and an outer peripheral portion fixed to the lens holder 510 and having a substantially concentric shape with respect to the support shaft 503. Support shaft
The axial positioning of the leaf springs 516a and 516b with respect to 503 is
The step provided on the support shaft 503 enables easy operation. Reference numeral 517 denotes a focusing coil fixed to the lens holder 510 so as to be coaxial with the leaf springs 516a and 516b, and is arranged at a position facing the focusing yokes 505a and 505b. Reference numerals 518a and 518b denote tracking coils that are adhesively fixed to both side surfaces of the lens holder 510.

Next, the operation will be described. Focused spot
When correcting the focus shift of 514, a desired current is applied to the focusing coil 517, and the lens holder 510 is moved along the support shaft 503 by the electromagnetic force obtained by the interaction with the magnetic force generated by the focusing magnets 504a and 504b. By moving the objective lens 511, the objective lens 511 is driven and controlled in the arrow C ₄ direction in the figure to control the focusing direction.

To correct the track shift of the focused spot 514, a desired current is applied to the tracking coils 518a and 518b and the tracking magnets 506a and 506b.
By electromagnetic force but obtained by interaction with the magnetic force generated, leaf springs 516a about the support shaft 503, 516b and rotate the lens holder 510 is deformed in a spiral shape in an arrow D ₄ direction in FIG. 54, the objective Controls the tracking direction of the lens 511.

FIG. 59 is a sectional view of an essential part of an optical disk device according to the 26th aspect of the present invention, in which the same reference numerals as those in FIG. 55 denote the same parts, and 515 designates the objective lens 511 in the longitudinal direction of the lens holder 510. The balance weight is fixed to one end on the other side, and is arranged so that the center of gravity of the movable portion constituted by the lens holder 510 and the like is arranged on the support shaft 503.

In this embodiment, the dynamic balance in the rotational direction about the support shaft 503 is ensured, and a rotational moment is generated in the movable portion even when the objective lens driving device makes a seek operation with respect to the optical disk 512. Without doing so, there is an advantage that unnecessary residual resonance does not occur after the seek.

FIG. 60 is an enlarged perspective view of a leaf spring used in the optical disk device according to the 27th invention. In the present embodiment, an example is shown in which the leaf springs 519a, 519b have bent portions 519c, 519d not only in the plane perpendicular to the support axis but also in the plane. With this shape of leaf spring, it is possible to suppress an unnecessary torsional resonance mode of the leaf spring particularly during drive control in the tracking direction.

FIG. 61 is an enlarged perspective view of a leaf spring used in the optical disk device according to the twenty-eighth invention. In this embodiment, an example in which two leaf springs are connected to each other is shown. Since the leaf spring 520 having this shape can independently manage the spring constants in the focusing direction and the tracking direction, it is possible to suppress variations in frequency characteristics of the optical disk device and improve mass productivity.

FIG. 62 is a plan view of the essential parts of an optical disk device according to the twenty-ninth invention, where the same reference numerals as in FIG. 54 denote the same parts. In this embodiment, the leaf springs 521a, 521b (521b
Shows an example in which an elastic member 522 is arranged between an inner peripheral portion (not shown) and the support shaft 503. In the present embodiment, the resonance peak of the leaf spring can be reduced, and in particular, the spring constant in the tracking direction, which tends to increase the spring constant of the leaf spring, can be easily set to a desired value.

The thirtieth to thirty-second inventions will be described. Fig. 63
FIG. 64 is an exploded perspective view showing an essential part of an optical disc device according to a thirtieth invention, FIG. 64 is a plan view of an essential part of FIG. 63, FIG. 65 is a sectional view of an essential part of FIG. 63, and FIG. 66 is shown in FIG. In the optical disc device,
FIG. 6 is a cross-sectional view of a main part showing a state after the adjustment of the objective lens angle when the optical axis of the objective lens is tilted by an angle θ _{6 with} respect to the mounting surface.

In FIGS. 63 to 66, reference numeral 601 denotes a base which is a fixed portion, and has a light flux passing hole 601a on the bottom surface so that a light beam 602 emitted from a light source (not shown) can enter from the bottom surface. In addition, the fixing hole 601b holds the lower end of the support shaft 603 coated with a fluororesin having a small friction coefficient. Focusing magnets 604a and 604b are vertically magnetized, and are fixed to the base 601 together with the focusing yokes 605a and 605b.

Reference numerals 606a and 606b denote tracking magnets which are magnetized in two poles in the left-right direction, and tracking yokes 607a and 607b are provided on the back surfaces thereof, respectively. 608a to 608d are screw holes provided in the base 601.

Reference numeral 610 is a lens holder made of a plastic material, 611 is an objective lens fixed to one end of the lens holder 610 in the longitudinal direction, and the light beam 602 is an optical disc.
It is condensed as a condensed spot 614 on the information recording surface 613 in 612. Reference numeral 615 is a balance weight fixed to one end of the lens holder 610 where the objective lens 611 in the longitudinal direction is not arranged.

Reference numeral 616 is a bearing fixed to the lens holder 610 so as to have an axis parallel to the optical axis of the objective lens 611, and is fitted to the support shaft 603. A focusing coil 617 is fixed to the lens holder 610 so as to be coaxial with the bearing 616, and is arranged at a position facing the focusing yokes 605a and 605b. Reference numerals 618a and 618b denote tracking coils that are adhesively fixed to both side surfaces of the lens holder 610.

Reference numeral 620 denotes a cover, which is a holding plate, and has a holding hole 62 for holding the light beam passage hole 621 and the upper end of the support shaft 603.
2, cover 620 Pin holes 624a, 624b and cover 62 that fit with adjustment pins (not shown) for adjusting the position of the body
Fixing screw 625a for fixing 0 to base 601 ~
It has screw holes 626a to 626d in which 625d is inserted.

Next, the operation will be described. Objective lens 61
When adjusting the angle in the arrow A ₄ direction (jitter direction) of 1, the cover 620 is moved in parallel along the upper surface of the base 601 in the arrow AA direction in the figure to tilt the support shaft 603 in the arrow A ₄ direction. , As a result, the arrow A ₄ of the objective lens 611.
Adjust the direction angle. When adjusting the angle of the objective lens 611 in the direction of arrow B ₄ (tracking direction), the cover 620 is moved in parallel along the upper surface of the base 601 in the direction of arrow BB in the figure to move the support shaft 603 to the direction of arrow B _4.
The objective lens 611 is tilted in the direction of arrow B _{4 and} the angle of the objective lens 611 is adjusted in the direction of arrow B ₄ .

From a microscopic view of this angle adjustment, the support shaft 603
Since the rigidity of is higher than that of the base 601 and the cover 620, the fixing hole 601b and the holding hole 622 are slightly deformed.
Cover 620 for tilt adjustment of about 10 mrad
The amount of movement during adjustment is about 0.1 mm when the length of the support shaft 603 is about 10 mm, which is a value that poses no problem in the actual manufacturing process.

After the angle adjustment of the objective lens 611 is completed,
The cover 620 is fixed to the base 601 with fixing screws 625a to 625d.

The operation of driving the objective lens 611 will be described. When correcting the focus shift of the focused spot 614, a desired current is applied to the focusing coil 617, and the objective lens is generated by the electromagnetic force obtained by the interaction with the magnetic force generated by the focusing magnets 604a and 604b.
The 611 is driven and controlled in the direction of arrow C ₄ in FIG. 65 to control in the focusing direction. To correct the track shift of the focused spot 614, the tracking coil 618
The desired force is applied to a and 618b, and the electromagnetic force obtained by the interaction with the magnetic force generated by the tracking magnets 606a and 606b causes the lens holder to center around the support shaft 603.
Rotate 610 in the direction of arrow D _{4 in} FIG. 64 by electromagnetic force,
The tracking direction of the objective lens 611 is controlled.

FIG. 67 is a diagram showing the frequency characteristic in the focus direction of this embodiment, in which unnecessary resonance unlike the conventional example shown in FIG. 97 does not occur.

FIG. 68 is an enlarged cross-sectional view showing the main parts of the optical disc apparatus according to the thirty-first invention, and the same reference numerals as those in FIG. 63 denote the same or corresponding portions. In this embodiment, instead of the support shaft 603 shown in FIG. 63, a support shaft 631 having both ends formed in a substantially semi-convex spherical shape is used, and a fixing hole 633 formed in a substantially semi-concave spherical shape is provided in the base 601. At the same time, the cover 620 is provided with a holding hole 634 formed in a substantially semi-concave spherical shape, and the cover 62 is
This embodiment shows another embodiment in the case where the angle of the objective lens 611 is adjusted by adjusting the position of 0 in the direction of arrow AA in a plane substantially perpendicular to the axis of the support shaft 631.
The same operation as that of the embodiment shown in 63 can be expected.

FIG. 69 shows another embodiment in which a support shaft 641 having a rigidity smaller than that of the support shaft 603 shown in FIG. 63 is used and the angle of the objective lens 611 is adjusted by bending the support shaft 631. As shown, the operation of this embodiment can be expected to be similar to that of the embodiment shown in FIG.

[0211]

Since the present invention is constructed as described above, it has the following effects.

Since the optical disc apparatus according to the first invention removes the groove interference signal from the defocus signal after the calculation,
A stable focus control can be realized.

Further, the optical disk device according to the second invention is
By using a plurality of light spots of three or more, parallel recording / reproduction can be performed at the same time.

Further, the optical disk device according to the third invention is
If a diffraction grating is used as a means for generating a plurality of light spots, a semiconductor laser of a single light emission source can be used, the device can be made inexpensive, and the diffraction grating can be finely rotated in a plane perpendicular to the light beam. By doing so, the arrangement accuracy of each light spot can be improved.

The optical disk device according to the fourth invention is
A simple sensor optical system can be realized by using it in combination with a so-called known differential push-pull method tracking sensor method.

Further, the optical disk device according to the fifth invention is
A diffraction spot is used as a means for generating a plurality of light spots, and the diffraction spot is composed of a plurality of light spots when the diffraction grating is rotationally driven in a plane perpendicular to the light beam during tracking and access. Can be set at an arbitrary angle with respect to the information track, and parallel recording / reproduction can be efficiently performed.

Further, the optical disc device according to the sixth invention is
A diffraction grating is used as a means for generating a plurality of light spots, and a dove prism is used as a means for setting a light spot row composed of a plurality of light spots at an arbitrary angle with respect to an information track. Efficient parallel recording by rotating the dove prism in a plane perpendicular to the light beam
The parallel reproduction can be performed, and the focal spot position on the photodetector can be kept unchanged.

The optical disk device according to the seventh to tenth inventions is
Since the two light-receiving surface ends facing each other in the divided band of the two-divided photodetector are formed in a sawtooth shape or a substantially triangular wave shape, and the two light-receiving surface ends are intermeshed with each other, a focus error occurs. The range in which the signal changes linearly with respect to defocus can be expanded. Further, since it is not necessary to widen the width of the dividing line that separates the light receiving surface of the two-divided photodetector, the frequency characteristic of the two-divided photodetector is deteriorated even when the reflected light beam from the optical disc enters the divided band. Absent. Therefore, even if this two-division photodetector is used for the pupil blocking method, it is possible to stabilize the focus control operation and improve the high frequency characteristic.

The optical disc apparatus according to the eleventh invention is
A large number of minute light-receiving surfaces are arranged in the divided bands of the two-division photodetector, and the connecting lines electrically connecting these minute light-receiving surfaces to either one of the two light-receiving surfaces cross the divided bands at substantially equal intervals. Direction, the connecting lines extending from the respective light receiving surfaces are alternately arranged, and the minute light receiving surface connected by one connecting line is proportional to the distance from the electrically connected light receiving surface. Since the two-division photodetector is configured to reduce the area, the range in which the focus error signal changes linearly with respect to defocus can be expanded. Further, since the area of the region where the light receiving surface does not exist in the divided band can be reduced, the frequency characteristic of the two-divided photodetector does not deteriorate even when the light from the optical disc enters the divided band. Therefore, even if this two-division photodetector is used for the pupil blocking method, it is possible to stabilize the focus control operation and improve the high frequency characteristic.

The optical disc apparatus according to the twelfth invention is
A large number of rectangular light-receiving surfaces are arranged in the divided bands of the two-division photodetector, and adjacent rectangular light-receiving surfaces are alternately connected to the left and right light-receiving surfaces, and the rectangular light-receiving surfaces connected to the respective light-receiving surfaces are arranged. Has a configuration in which the length of its short side decreases in proportion to the distance from the light receiving surface, so that the range in which the focus error signal changes linearly with respect to defocus can be expanded. Further, since the area of the region where the light receiving surface does not exist in the divided band can be reduced, the frequency characteristic of the two-divided photodetector does not deteriorate even when the light from the optical disc enters the divided band. Therefore, even if this two-division photodetector is used for the pupil blocking method, it is possible to stabilize the focus control operation and improve the high frequency characteristic.

The optical disk device according to the thirteenth to twentieth inventions is
As a means for splitting the reflected light flux from the optical disk, a light flux splitting element having a diffraction grating formed on a substantially half surface is used.
It is possible to realize stable operation and high efficiency at low cost.

Further, when a light beam splitting element having a plane type diffraction grating is used, the plane type diffraction grating is manufactured by the technique of optical lithography or etching. The device can be realized.

In the optical disc device according to the twenty-first aspect of the invention, the reflected light beam is split by the light beam splitting element having the diffraction grating formed on the approximately half surface, and the split light beams are shaped such that the end portions of the two opposite light-receiving surfaces have the same shape. Since the light is received by the two-part photodetector having a substantially sawtooth shape, a substantially triangular wave shape, or a substantially sine wave shape, it is possible to efficiently stabilize the focus control operation and improve the high frequency characteristic at a low cost.

In the optical disc device according to the twenty-second aspect of the present invention, since the component for adjusting the tilt can be constituted by only one thin ring-shaped flat plate, it is possible to obtain an inexpensive, compact and thin optical disc device.

Since it is not necessary to provide a large spherical surface as in the conventional example, the degree of freedom in design can be greatly expanded.

Further, since the weight of the portion held by the adhesive is only the objective lens, it is light, so that unnecessary vibration is unlikely to occur when accessing the optical disc, and the access time can be shortened.

Further, the optical disk device according to the twenty-third and twenty-fourth inventions is provided with a notch and a tongue so that the positions of the above-mentioned two pairs of protrusions do not change, and a straight line connecting the pair of protrusions is provided. Are arranged so as to be substantially orthogonal to each other, and the directions of the respective straight lines correspond to the radial direction and the tangential direction of the optical disc, thereby defining the tilt direction of the optical means and facilitating the tilt adjustment. Is possible.

Since the optical disk device according to the twenty-fifth aspect of the invention eliminates the contact portion by supporting the movable portion with the leaf spring,
It has an effect that a frictional force is not generated during focusing control or tracking control and a stable control system is provided, and at the same time, abrasion is not generated and an optical adverse effect or life shortening does not occur in the peripheral portion.

The optical disc apparatus according to the 26th aspect of the invention is
When a seek is performed on the optical disc, a rotational moment about the support shaft as a rotation center is not generated with respect to the movable portion, so that unnecessary residual vibration after the completion of the seek can be suppressed.

[0230] Further, the optical disk device according to the twenty-seventh invention is
In particular, since unnecessary torsional resonance mode of the leaf spring can be suppressed during drive control in the tracking direction, there is an effect of having a stable control system.

The optical disc apparatus according to the 28th aspect of the invention is
Since it is possible to reduce the variation in the spring constant of the leaf spring, there is an effect that the mass productivity is high.

[0232] Further, the optical disc apparatus according to the twenty-ninth invention is
The resonance peak of the leaf spring is reduced, and it is easy to set the spring constant in the tracking direction, which tends to increase the spring constant of the leaf spring, to a desired value. Therefore, there is an effect of having a stable control system. .

In the optical disk device according to the thirtieth aspect of the invention, the amount of angle adjustment of the objective lens corresponds to the amount of movement of the cover which is the holding plate, and since there is a substantially proportional relationship within a minute angle, the translation amount is controlled. Thereby, there is an effect that the adjustment accuracy can be improved.

Further, the optical disc apparatus according to the thirty-first invention is
Even if the angle adjustment of the objective lens is once performed and then the angle adjustment is required again, the readjustment can be easily performed.

The optical disc apparatus according to the thirty-second invention is
Since a screw can be used as a fixing means after adjusting the angle of the objective lens, a strong fixing force that does not adversely affect the frequency characteristics of the objective lens actuator can be obtained, and the reliability can be improved. .

[Brief description of drawings]

FIG. 1 is a schematic view showing a part of an optical disc device according to a first invention.

FIG. 2 is a detailed view of a photodetector unit in FIG.

FIG. 3 is a schematic diagram showing a light spot arrangement relationship on an information track in the embodiment shown in FIG.

FIG. 4 is an enlarged conceptual view of an information track for showing the relationship between the information track of the optical disk device and the defocus signal of each light spot in the embodiment shown in FIG.

5 is a diagram showing a defocus signal after calculation of the optical disc device in the embodiment shown in FIG.

FIG. 6 is a schematic diagram showing a defocus signal at the time of track access of the optical disc device in the embodiment shown in FIG.

FIG. 7 is a schematic view showing a part of an optical disc device according to a second invention.

FIG. 8 is a schematic diagram showing a light spot arrangement relationship on an information track in the embodiment shown in FIG.

FIG. 9 is a schematic view showing a part of an optical disc device according to a third invention.

FIG. 10 is a schematic diagram showing an arrangement relationship of light spot rows on an information track in the embodiment shown in FIG.

FIG. 11 is a schematic view showing a part of an optical disc device according to a fourth invention.

12 is a detailed view showing the photodetector section in FIG. 10 in the embodiment shown in FIG.

FIG. 13 is a schematic view showing a part of an optical disc device according to a fifth invention.

FIG. 14 is a schematic diagram showing a positional relationship of light spots on an information track in the embodiment shown in FIG.

FIG. 15 is a schematic view showing a part of an optical disc device according to a sixth invention.

16 is an optical path diagram showing details of the optical path of the dove prism portion in FIG. 15 in the embodiment shown in FIG.

FIG. 17 is a plan view showing a two-divided photodetector in an optical disk device according to seventh to tenth inventions.

FIG. 18 is an enlarged view of a divided band portion of the two-divided photodetector shown in FIG.

FIG. 19 is a diagram showing division lines of the two-division photodetector shown in FIG. 17 on yz coordinates.

FIG. 20 is a diagram showing a shape of a focused spot irradiated on the two-divided photodetector when the focused point of the outgoing light flux is located on the optical disc.

FIG. 21 is a focus error signal characteristic diagram when a focused spot is displaced in a direction parallel to a split band in a two-split photodetector.

22 is a characteristic diagram of a focus error signal in the embodiment shown in FIG.

FIG. 23 is a plan view showing a two-part photodetector in an optical disc device according to an eleventh invention.

FIG. 24 is a plan view showing a two-divided photodetector in an optical disc device according to a twelfth invention.

FIG. 25 is a perspective view showing a configuration of an optical disk device according to thirteenth to twentieth inventions.

FIG. 26 is a schematic diagram of an optical path when a focused spot of a light flux emitted from an objective lens is on the information recording surface in the embodiment shown in FIG.

FIG. 27 is a diagram showing a state of a light beam at a light beam splitting element and a two-split photodetector when a focused spot of a light beam emitted from an objective lens is on an information recording surface in the embodiment shown in FIG. 25.

28 is a schematic diagram of an optical path when the information recording surface approaches the objective lens in the example shown in FIG. 25. FIG.

FIG. 29 is a diagram showing a state of light fluxes in the light flux splitting element and the two-split photodetector when the information recording surface approaches from the objective lens in the embodiment shown in FIG. 25.

FIG. 30 is a schematic diagram of an optical path when the information recording surface is separated from the objective lens in the example shown in FIG. 25.

FIG. 31 is a diagram showing a state of light fluxes in the light flux splitting element and the two-split photodetector when the information recording surface is separated from the objective lens in the embodiment shown in FIG. 25.

32 is a diagram showing a focus error signal obtained in the embodiment shown in FIG.

FIG. 33 is a perspective view of a light beam splitting element in which a planar diffraction grating having an uneven surface is formed.

FIG. 34 is a configuration diagram showing an optical disk device in another embodiment of the optical disk device according to the thirteenth to twentieth inventions.

FIG. 35 is a diagram showing a state of a light beam in a light beam splitting element and a two-split photodetector when a focused spot of a light beam emitted from an objective lens is on the information recording surface in the example shown in FIG. 34.

36 is a diagram showing a state of light fluxes in the light flux splitting element and the two-split photodetector when the information recording surface approaches the objective lens in the embodiment shown in FIG. 34.

37 is a diagram showing a state of light fluxes in the light flux splitting element and the two-split photodetector when the information recording surface is separated from the objective lens in the embodiment shown in FIG. 34.

38 is a diagram showing a focus error signal obtained in the embodiment shown in FIG. 34.

FIG. 39 is a diagram for explaining parameters of the optical component in the example shown in FIG. 34.

FIG. 40 is a perspective view of a light beam splitting element in which a refractive index modulation type planar diffraction grating is formed.

FIG. 41 is a perspective view showing a configuration of an optical disc device according to a twenty-first invention.

FIG. 42 is a perspective view showing another configuration of the optical disk device according to the twenty-first invention.

FIG. 43 is an exploded perspective view showing a first embodiment of the tilt adjusting section in the optical disc device according to the 22nd invention.

44 is a perspective view of a main part of an optical disk device equipped with the tilt adjusting part shown in FIG. 43.

45 is a main-portion plan view of an optical disc device in which the tilt angle adjusting unit shown in FIG. 43 is mounted.

46 is a cross-sectional view taken along the line I-I of FIG. 45.

47 is a cross-sectional view taken along the line II-II of FIG. 45.

FIG. 48 is an exploded perspective view showing a second embodiment of the tilt adjusting section in the optical disk device according to the 22nd invention.

FIG. 49 is an exploded perspective view showing a third embodiment of the tilt angle adjusting portion in the optical disc device according to the 22nd invention.

50 is an exploded perspective view showing a fourth embodiment of the tilt angle adjusting portion in the optical disk device according to the 22nd invention. FIG.

FIG. 51 is an exploded perspective view showing a tilt angle adjusting portion in the optical disk device according to the twenty-third invention.

FIG. 52 is an exploded perspective view showing a tilt angle adjusting portion in the optical disk device according to the twenty-fourth invention.

FIG. 53 is an exploded perspective view showing a main part of an optical disk device according to a 25th invention.

54 is a plan view of the main part shown in FIG. 53. FIG.

55 is a cross-sectional view of the main parts shown in FIG. 53.

FIG. 56 is a cross-sectional view of the main parts showing the driving state in the focusing direction of the embodiment shown in FIGS. 53 to 55.

57 is a cross-sectional view of the main parts showing the driving state in the focusing direction of the embodiment shown in FIGS. 53 to 55.

58 is a plan view showing the shape of the leaf spring of the embodiment shown in FIGS. 53 to 57. FIG.

FIG. 59 is a cross-sectional view showing the main parts of an optical disk device according to the 26th invention.

FIG. 60 is a perspective view of a leaf spring used in the optical disc device according to the twenty-seventh invention.

FIG. 61 is a perspective view of a leaf spring used in the optical disc device according to the twenty-eighth invention.

FIG. 62 is a plan view showing the main parts of an optical disk device according to the 29th invention.

FIG. 63 is an exploded perspective view showing a main part of an optical disc device according to a thirtieth invention.

64 is a plan view of an essential part shown in FIG. 63.

65 is a cross-sectional view of the main parts shown in FIG. 63.

66 is a cross-sectional view of the main parts showing the state after the angle adjustment in the example shown in FIGS. 63 to 65. FIG.

67 is a frequency characteristic diagram in the focus direction in the examples shown in FIGS. 63 to 65. FIG.

FIG. 68 is an enlarged cross-sectional view showing the main parts of the optical disk device according to the thirty-first invention.

FIG. 69 is a sectional view of an essential part showing a state after the angle adjustment of the optical disc device according to the thirty-second aspect of the present invention.

FIG. 70 is a schematic view showing a part of a conventional optical disc device.

71 is an enlarged information track conceptual diagram showing the relationship between the information track of the optical disc and the defocus signal of each light spot in the conventional apparatus shown in FIG. 70.

FIG. 72 is a diagram showing the configuration of another conventional device.

73 is a diagram showing a state in which the reflected light flux is focused in the conventional apparatus shown in FIG. 72.

FIG. 74 is a plan view showing a light receiving surface of the two-divided photodetector in the state shown in FIG. 73.

75 is a diagram showing a state where the light receiving surface is irradiated with the reflected light flux before focusing in the conventional apparatus shown in FIG. 72.

76 is a plan view showing the light receiving surface of the two-division photodetector in the state shown in FIG. 75. FIG.

77 is a diagram showing a state when the reflected light flux is focused before being irradiated on the light receiving surface in the conventional apparatus shown in FIG. 72.

78 is a plan view showing the light receiving surface of the two-division photodetector in the state shown in FIG. 77. FIG.

79 is a plan view showing a light receiving surface of the two-divided photodetector shown in FIG. 72. FIG.

FIG. 80 is a characteristic diagram of a focus error signal by the conventional device shown in FIG. 72.

FIG. 81 is a perspective view showing the configuration of still another conventional device.

82 is a schematic diagram of an optical path when a focused spot of a light flux emitted from an objective lens is on the information recording surface in the conventional apparatus shown in FIG. 81.

83 is a schematic diagram of an optical path when the information recording surface approaches the objective lens in the conventional apparatus shown in FIG. 81.

84 is a schematic diagram of an optical path when the information recording surface is separated from the objective lens in the conventional apparatus shown in FIG. 81.

85 is a diagram for explaining parameters of optical components in the conventional apparatus shown in FIG. 81. FIG.

86 is a diagram showing parameters of optical components in the conventional apparatus shown in FIG. 81.

FIG. 87 is an exploded perspective view showing still another conventional device.

88 is a schematic cross-sectional view of the conventional device shown in FIG. 87.

FIG. 89 is a perspective view showing a main part of still another conventional device.

90 is a cross-sectional view taken along the line III-III of FIG. 89.

FIG. 91 is a cross-sectional view of a main part of still another conventional device.

92 is a model diagram showing a state in which the adhesive, which is the fixing means after the angle adjustment, serves as a spring element and a damping element in the conventional apparatus shown in FIG. 91. FIG.

93 is a diagram showing a defocus signal in the conventional apparatus shown in FIG. 70.

94 is a schematic diagram showing a defocus signal at the time of track access in the conventional apparatus shown in FIG. 70.

95 is a characteristic diagram of a focus error signal based on a detection signal from the light receiving surface shown in FIG. 79.

96 is a characteristic diagram showing sensitivity distributions of the two light receiving surfaces shown in FIG. 79.

97 is a frequency characteristic diagram in the focus direction of the conventional apparatus shown in FIG. 91.

[Explanation of symbols]

 101, 206, 305 Optical disc 115 Land portion 116 Groove portion 122a, 122b, 142a to 142e, 152a to 152c Optical spot 124, 144 Photodetector portion 126 Adder 127 Control circuit 129 Defocus signal 145 Arithmetic processing circuit 150 Diffraction grating 160 Light detector 170a, 170b, 181a, 181b Drive coil 180 Dove prism 201 Light source 207 Shield plate 216, 217, 221, 222 Light receiving surface 218, 220, 325, 329, 333 Two-divided light detector 219 Divided band 223 Micro light reception Surface 224 Connection line 225 Short-shaped light receiving surface 226 Short-shaped light receiving surface 231 Dividing line 301 Light source 304, 420, 511, 611 Objective lens 324, 343 Beam splitting element 328, 332, 336 Condensing spot 341 Diffraction grating part 342 Non-diffraction grating 408 Optical axis 420a, 420b, 424b, 424c Protrusions 420c, 421a Tongue piece 421 Ring-shaped flat plate 422a, 422b Upper protrusion 423a, 423b Lower protrusion 424 Objective lens holder 424a Fin portion 424d Notch portion 425 Bearing 426 Focusing coil 503 Support shaft 510, 610 Lens holder 515 Balance weight 516a, 516b Leaf spring 601 Base 601b, 633 Fixed hole 603, 631, 641 Support shaft 620 Cover 622, 634 Holding hole FES, FESa, FESb, FESc Focus error signal E Emitted light flux R, R1, R2 Reflected light flux Ra, Rb, Rc Luminous flux L1 First straight line L2 Second straight line

Front page continued (72) Inventor Mitsuru Irie 1 Baba-Zou, Nagaokakyo-shi, Kyoto Inside Video Systems Development Laboratory, Mitsubishi Electric Corporation (72) Inventor Kazuhiko Nakane 8-1-1 Tsukaguchihonmachi, Amagasaki-shi, Hyogo Sanbishi Electric Industrial Co., Ltd. Industrial Systems Research Institute (72) Inventor Kenjiro Kime, No. 1 Baba Institute, Nagaokakyo-shi, Kyoto Mitsubishi Electric Co., Ltd. Video System Development Laboratory (72) Hideaki Kobachi, No. 1 Baba Institute, Nagaokakyo, Kyoto Mitsubishi Electric Systems Co., Ltd. Video System Development Laboratory

Claims (32)

[Claims] 1. An optical disk device for recording / reproducing information by irradiating a focused spot onto an optical disk having a land portion and a groove portion which form an information track, the focused spot being the land portion. An optical disk device characterized in that a single unit is disposed in each of the groove and the groove portion, and focus control is performed using a signal obtained by calculating a focus shift signal obtained from the reflected light of each focused spot. . 2. An optical disk device for irradiating a focused spot onto an optical disk having a land portion and a groove portion forming an information track to record / reproduce information, wherein the focused spot is the land portion. And a plurality of grooves are arranged in each of the groove portion, and focus control is performed using a signal obtained by calculating a defocus signal obtained from the reflected light of each condensed spot, and the condensed spot arranged in the land portion is used. An optical disk device characterized by being configured to perform parallel recording / reproduction in parallel. 3. An optical disk device for irradiating a focused spot onto an optical disk having a land portion and a groove portion forming an information track to record / reproduce information, a light beam is split by a diffraction grating. Then, a plurality of focused spots are formed, and the focal point deviation signal obtained from the reflected light of each focused spot is constructed by adjusting the position of each focused spot by rotating the diffraction grating. An optical disk device having a structure for performing focus control using a signal obtained by calculating 4. An optical disc device for recording / reproducing information by irradiating a focused spot on an optical disc having a land portion and a groove portion forming an information track, and at least the land portion and the groove portion. And 1 and 2 focused spots are formed respectively on and, and focus control is performed by using a signal obtained by calculating a defocus signal obtained from the reflected light of these 3 focused spots. An optical disk device characterized in that tracking control is performed using a signal obtained by calculating a tracking shift signal obtained from the reflected light of these three focused spots. 5. An optical disk device for recording / reproducing information by irradiating a condensed spot on an optical disk having a land portion and a groove portion forming an information track to divide a light beam by a diffraction grating. A plurality of converging spots are formed, and the diffraction grating is configured to be rotationally driven when the information track is accessed, and a signal obtained by calculating a defocus signal obtained from reflected light of each converging spot is used. An optical disk device characterized by being configured to perform focus control. 6. An optical disk device for irradiating a focused spot on an optical disk having a land portion and a groove portion forming an information track to record / reproduce information, a light beam is split by a dove prism. A plurality of converging spots are formed, and the dove prism is configured to be rotationally driven at the time of accessing the information track, and a signal obtained by calculating a defocus signal obtained from the reflected light of each converging spot is used. An optical disk device characterized by being configured to perform focus control. 7. A splitting device in which light emitted from a light source is focused on an optical disc through an optical system and a part of a reflected light flux from the optical disc is shielded so that two light receiving surfaces of a two-split photodetector face each other. In an optical disc device that obtains a focus error signal based on the output signals from the two light receiving surfaces of the two-divided photodetector by irradiating the vicinity of the band, the shape of the light-receiving surface end portion in the divided band of the two-divided photodetector An optical disk device, which has a substantially saw-tooth shape or a substantially triangular wave shape and is configured to mesh with each other. 8. A pitch of the substantially sawtooth or substantially triangular wave portions at the light receiving surface end portion of the two-division photodetector is p, and a width of the substantially sawtooth or substantially triangular wave portions in a direction crossing the division band is d. When the origin of the yz coordinate system is set to the center of the dividing band, the longitudinal direction of the dividing band is set to the y direction, and the lateral direction of the dividing band is set to the z direction, the dividing line that divides the two light receiving surfaces is , Y = (p / d) z + 2np y = − (p / d) z + (2n−1) p where −d / 2 ≦ z ≦ d / 2, n: an integer The optical disk device according to claim 7. 9. A pitch p of substantially saw-toothed or substantially triangular wave portions at the light receiving surface end of the two-split photodetector, a wavelength λ of the light source, and reflection from the optical disk incident on the two-split photodetector. 8. The NA ₁ ≦ 5λ / 8p is established between the numerical aperture NA ₁ of the luminous flux and the numerical aperture NA _1.
The optical disk device described. 10. A width d in a direction crossing a division band of a substantially saw-tooth shape or a substantially triangular wave shape at an end portion of a light receiving surface of a two-division photodetector, a wavelength λ of the light source, and incidence on the two-division photodetector. 8. The two-divided photodetector is configured such that d ≧ λ / NA ₁ is established between the reflected light flux from the optical disc and the numerical aperture NA ₁ . Optical disk device. 11. A splitting system in which light emitted from a light source is condensed and irradiated onto an optical disc through an optical system to partially shield a reflected light flux from the optical disc so that two light receiving surfaces of a two-split photodetector face each other. In an optical disc device that obtains a focus error signal based on the output signals from the two light receiving surfaces of the two-division photodetector by irradiating the vicinity of the two-division photodetector, a plurality of divided micro A light-receiving surface is formed, and connection lines for electrically connecting these minute light-receiving surfaces to one of the two light-receiving surfaces are provided at substantially equal intervals in the direction crossing the division band, and extend from each light-receiving surface. The connecting lines are arranged alternately, and further, the area of the minute light-receiving surface connected by one connecting line is configured to be reduced substantially in proportion to the distance from the electrically connected light-receiving surface. A light disc characterized by Disk device. 12. A splitting device in which two light-receiving surfaces of a two-split photodetector face each other by concentrating and irradiating light emitted from a light source onto an optical disc through an optical system and shielding a part of a reflected light flux from the optical disc. In an optical disc device for irradiating near a band and obtaining a focus error signal based on output signals from two light receiving surfaces of the two-divided photodetector, a large number of rectangular light-receiving surfaces are provided in the divided bands of the two-divided photodetector. The adjacent rectangular light receiving surfaces are alternately connected to the left and right light receiving surfaces, and the length of the short side of the rectangular light receiving surface connected to each light receiving surface is approximately equal to the distance from the light receiving surface. An optical disk device characterized by being configured to decrease in proportion. 13. Light emitted from a light source is focused onto an optical disc through an optical system to divide a reflected light beam from the optical disc into a plurality of light beams, and each of the divided reflected light beams is divided into a plurality of two light beams. When the light emitted from the light source is focused on the optical disc, a condensed spot of the reflected light flux is formed on the dividing line of the two-divided photodetector when the light emitted from the light source is focused on the optical disc. In the optical disc device that obtains the focus error signal based on the output signals of the plurality of two-division photodetectors, a means for dividing the reflected light flux into a plurality of light fluxes is provided by a light beam splitting device whose substantially half plane of the incident surface is a diffraction grating portion. A focus error signal using one or more diffracted light beams of the reflected light beam generated by the diffraction grating unit and a light beam that does not pass through the diffraction grating unit. To be Characteristic optical disk device. 14. Light emitted from a light source is condensed and irradiated onto an optical disc through an optical system, a reflected light beam from this optical disc is divided into a plurality of light beams, and each of the divided reflected light beams is divided into a plurality of two light beams. When the light emitted from the light source is focused on the optical disc, a condensed spot of the reflected light flux is formed on the dividing line of the two-divided photodetector when the light emitted from the light source is focused on the optical disc. In the optical disc device that obtains the focus error signal based on the output signals of the plurality of two-division photodetectors, the means for dividing the reflected light flux into a plurality of light fluxes is provided with a transmission type or a reflection type with a substantially half of the incident surface. A diffraction grating portion in which a plane type diffraction grating is formed, and the remaining substantially half surface is composed of a light beam splitting element that is a transmissive or reflective non-diffraction grating portion, and the diffraction grating portion and the non-diffraction element. The boundary of the lattice part is geometric Are arranged so as to substantially divide the reflected light flux into two substantially equal parts, and one or more diffracted light beams of the reflected light flux generated by the diffraction grating portion and a light flux from the non-diffraction grating portion are used for focusing. An optical disk device characterized by being configured to obtain an error signal. 15. The light beam splitting element, wherein the grating line of the diffraction grating section is a straight line, the grating period is constant, and the direction of the grating line is the direction of the boundary line between the diffraction grating section and the non-diffraction grating section. 15. The optical disk device according to claim 13 or 14, wherein the optical disk device and the optical disk device are substantially orthogonal to each other. 16. The beam splitting element has a boundary line between the diffraction grating portion and the non-diffraction grating portion which is a straight line, and a direction of the straight line is substantially orthogonal to a tangential direction of the guide groove on the optical disk. The optical disk device according to claim 13 or 14, wherein the optical disk device is adapted to be projected. 17. The plane type diffraction grating of the light beam splitting element comprises 2
Value has a phase depth, and the duty of the phase modulation is about 5
15. The optical disk device according to claim 14, wherein the depth of phase modulation is about 180 degrees at 0%. 18. The optical disk apparatus according to claim 14, wherein the plane type diffraction grating of the beam splitting element has phase modulation realized by surface irregularities or modulation of the refractive index. 19. A plurality of two-split photodetectors and one or more two-split photodetectors for receiving one or more luminous fluxes obtained by the diffracting action of the diffraction grating portion of the luminous flux splitting element and the luminous flux splitting element. 15. The optical disk device according to claim 13 or 14, wherein one two-divided photodetector for receiving the light beam from the non-diffraction grating portion is contained in one package. 20. A plurality of two-division photodetectors have division lines of each two-division photodetector substantially linear, and all the division lines are 1
15. The optical disk device according to claim 13 or 14, wherein the optical disk device exists on a substantially straight line of a book. 21. Light emitted from a light source is condensed and irradiated onto an optical disk through an optical system, a reflected light beam from the optical disk is divided into a plurality of light beams by a light beam dividing means, and each of the divided reflected light beams is divided. Is condensed and irradiated in the vicinity of the dividing lines of the plurality of two-division photodetectors, and when the condensed spot of the emitted light is focused on the optical disc, the condensed spot of the reflected light flux is substantially on the dividing line. An optical disk device in which the two-division photodetectors are arranged so as to be positioned and a focus error signal is obtained based on output signals of the plurality of two-division photodetectors,
The beam splitting means is composed of an element whose half surface is a diffraction grating portion, and the split line of the two-split photodetector has a substantially sawtooth shape, a substantially triangular wave shape, or a substantially sine wave shape. Optical disk device. 22. An optical disk device for adjusting an angle of an optical axis of an optical system held by a holder in a desired direction,
A ring-shaped flat plate is provided between the optical system and the holder in the vicinity of the peripheral edge of the optical system, and the optical axes are respectively provided between the flat plate and the optical system and between the flat plate and the holder. On the first and second straight lines that pass and intersect each other,
A total of four protrusions, two each sandwiching the optical axis, are provided, and the orientation of the optical axis of the optical system is adjusted to a desired direction by an angle according to the height of the protrusion. Characteristic optical disk device. 23. The holder is provided with a cutout portion, and the ring-shaped flat plate is provided with a tongue piece fitted in the cutout portion to prevent rotation in the circumferential direction. Optical disk device. 24. The holder is provided with a cutout portion, and the ring-shaped flat plate and the optical system are provided with tongue pieces fitted in the cutout portion to prevent rotation in the circumferential direction. The optical disk device according to claim 22. 25. An optical disk device comprising a mechanism for driving and controlling a focused spot position focused on an optical disk for optically recording / reproducing information, wherein a light beam is focused on the optical disk. Objective lens to
A lens holder having the objective lens fixed at one end, a support shaft having an axis parallel to the optical axis of the objective lens, and a support shaft perpendicular to the support shaft and separated by a certain amount in the axial direction. A pair of leaf springs, each of which is arranged on a pair of flat surfaces, has an inner circumference fixed to the support shaft and an outer circumference fixed to the lens holder, and has a set of substantially concentric shapes with respect to the axis, An optical disk device, characterized in that focusing control is performed by driving the lens holder along with tracking control by rotating the lens holder around the axis. 26. The center of gravity of a movable portion provided with a lens holder supported by a leaf spring is arranged on a support shaft,
26. The optical disk device according to claim 25, wherein a balance weight is provided on the lens holder. 27. The optical disk device according to claim 25 or 26, wherein the leaf spring also has an element perpendicular to the plane. 28. The leaf springs are coupled to each other, 25, 26, or 27.
The optical disk device described. 29. The optical disk device according to claim 25, wherein an elastic member is added to the inner peripheral portion of the leaf spring. 30. In an optical disc device for adjusting an angle of an optical axis of an optical system held by a holder in a desired direction, a fixing part for supporting and fixing a mechanism for adjusting the angle, and one end fixed to the fixing part. A support shaft that supports the holder slidably and rotatably, and a holding plate that holds the other end of the support shaft, and the holding plate is in a plane substantially perpendicular to the support shaft. An optical disk device, characterized in that the spindle is tilted by moving the optical axis to adjust the angle of the optical system. 31. In an optical disc device for adjusting an angle of an optical axis of an optical system held by a holder in a desired direction, a fixing part which supports and fixes a mechanism for adjusting the angle and has a semi-concave spherical shape part, A holding plate having a semi-concave spherical portion,
Both ends have a semi-convex spherical shape, and one end has a semi-concave spherical shape part of the fixed portion, and the other end has a spindle slidably held by the semi-concave spherical shape part of the holding plate. An optical disk device characterized in that the supporting shaft is tilted by moving the holding plate in a plane substantially perpendicular to the axis to adjust the angle of the optical system. 32. In an optical disc device for adjusting an angle of an optical axis of an optical system held by a holder in a desired direction, a fixing part for supporting and fixing a mechanism for adjusting the angle, and one end fixed to the fixing part. And a support shaft that supports the holder slidably and rotatably, and a holding plate that holds the other end of the support shaft, and moves the holding plate in a plane substantially perpendicular to the support shaft. The optical disk device is configured so that the support shaft is curved by doing so and the angle of the optical system is adjusted.