JP2005149543A - Optical pickup and disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup and a disk drive which are inexpensive, miniaturized and low-profile without lowering performance. <P>SOLUTION: The optical pickup is provided with: a rise mirror 17 reflecting each emitted laser beam toward two kinds of disk type recording media 100a, 100b; an objective lens 19 condensing each laser beam reflected by the rise mirror on a recording plane of each disk type recording medium; and an aperture limit element 18 having a limit hole 18a limiting a diameter of luminous flux of the laser beam made incident on the objective lens, a laser light source is arranged so that a polarization direction of the laser beam is made almost parallel to a radial direction of the disk type recording medium, limit of the diameter of the luminous flux by the aperture limit element is made different in the radial direction or the tangential direction of the disk type recording medium, the number of apertures in the tangential direction of the objective lens is made less than the number of aperture in the radial direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to the technical field of optical pickups and disk drive devices. More specifically, the present invention relates to a technical field for reducing the thickness of a disk-shaped recording medium by limiting the diameter of a light beam by an aperture limiting element in a radial direction and a tangential direction.

  2. Description of the Related Art There is a disk drive device that records and reproduces information signals on a disk-shaped recording medium. Such a disk drive device moves in the radial direction of the disk-shaped recording medium mounted on a disk table and moves to the disk-shaped recording medium. And an optical pickup that records or reproduces an information signal by irradiating a laser beam through an objective lens.

  Some optical pickups are capable of recording or reproducing information signals on two types of disc-shaped recording media having different operating wavelengths, for example, both DVD (Digital Versatile Disc) and CD (Compact Disc). (See, for example, Patent Document 1) In such an optical pickup, laser light having a first wavelength (660 nm) corresponding to DVD or laser light having a second wavelength (785 nm) corresponding to CD. Is emitted according to the disk-shaped recording medium mounted on the disk table.

  The invention described in Patent Document 1 is for the purpose of ensuring good characteristics of tracking control and focusing control by reducing the mass of the movable part of the objective lens driving device (biaxial actuator) provided in the optical pickup. The present invention has been made, and the object of the invention is achieved by providing an aperture limiting element for limiting the diameter of a laser beam in a fixed portion of an objective lens driving device. In addition, when the aperture limiting element is provided in the fixed part of the objective lens driving device, the tracking control may be hindered so that the aperture of the objective lens exists in the fluctuation range (movement range) of the laser beam during tracking control. In order to avoid this, the restriction by the aperture limiting element in the radial direction of the disc-shaped recording medium, which is the direction of fluctuation of the laser light, is relaxed to ensure good characteristics of the laser light during tracking control.

  By the way, in the optical pickup, a working distance (WD) is required between the objective lens and the disk-shaped recording medium to allow surface vibration of the disk-shaped recording medium. The WD is determined on the basis of the standard runout amount of a disc-shaped recording medium having a low recording density, that is, a disc-shaped recording medium having a large surface runout allowance. When the focal position of the objective lens is determined, the focal position of the objective lens for the other disk-shaped recording medium is determined by the difference in substrate thickness between the two disk-shaped recording media.

For example, in the case of DVD and CD, the surface runout amount of CD having a low recording density is ± 0.5 mm on the standard, the thickness of CD is 1.2 mm, and the thickness of DVD is 0.6 mm. The difference in distance (WD) from the upper surface of the objective lens to the lower surface of the disk-shaped recording medium is a value obtained by dividing the difference in thickness of the disk-shaped recording medium by the refractive index of the disk-shaped recording medium. Because there is a difference of WD,
0.6 / 1.5 = 0.4 (mm)
It becomes.

Therefore, as shown in FIG. 7, when the working distance in DVDx is WD1,
WD1 = 0.5 + 0.4 = 0.9 (mm),
Assuming that the working distance in CD is WD2,
WD2 = 0.5 (mm)
It becomes. At this time, if the focal length of the objective lens a is 1.9 mm and the numerical aperture (NA) is 0.65, the diameter D of the light beam b of the laser light incident on the objective lens a is
D = 2 × 0.65 × 1.9 = 2.47 (mm)
It becomes. The numerical aperture NA of the objective lens a depends on the size of the limiting hole e of the aperture limiting element d disposed between the objective lens a and the rising mirror c. The aperture limiting element d has a circular limiting hole e that limits the diameter of the laser beam.

On the other hand, in the case of DVDx, the distance A required from the lower end of the objective lens a to the upper end of the light beam b detects the light reflected on the surface of the disc-shaped recording medium when determining the type of the disc-shaped recording medium. Therefore, it is determined by the thickness of DVDx. Therefore, the distance A requires an amount obtained by dividing the thickness of the DVDx by the refractive index, and the distance A is
A = 0.6 / 1.5 + α
It becomes. α is a margin considering the error of each value, and when α = 0.05 (mm),
A = 0.4 + 0.05 = 0.45 (mm)
It becomes.

The height H of the optical pickup is defined by the distance from the lower surface to the lower surface of the disc-shaped recording medium. Therefore, the height H is
H = WD1 + t + A + D + β
It becomes. t is the thickness of the objective lens a, and β is a margin in consideration of an error of each value. If t = 1 (mm) and β = 0.5 (mm),
H = 0.9 + 1 + 0.45 + 2.47 + 0.5 = 5.32 (mm)
It becomes.

JP 2001-76370 A

  As described above, the height H of the optical pickup capable of recording or reproducing the information signal on two types of disc-shaped recording media having different operating wavelengths is based on the standard of the disc-shaped recording media having a low recording density. It is determined by the surface shake amount, the numerical aperture NA of the objective lens a, the thickness of the disc-shaped recording medium, and the like.

  However, in the situation where disk reproducing devices and disk recording / reproducing devices equipped with optical pickups have become widespread, it is desired to reduce the size and thickness without increasing the cost, especially in portable devices. There is a high demand for further downsizing and thinning.

  On the other hand, with the widespread use of disk playback devices and the like, there is a high demand for maintaining or improving the good performance of further optical pickups, and it is particularly necessary to maintain and improve the quality of information signals.

  Accordingly, it is an object of the present invention to overcome the above-described problems and to reduce the size and thickness of the optical pickup and the disk drive device at low cost without deteriorating the performance.

  In order to solve the above-described problems, the optical pickup of the present invention includes a rising mirror that reflects each emitted laser beam toward two types of disk-shaped recording media, and each laser beam that is reflected by the rising mirror. Is provided on the recording surface of each disk-shaped recording medium, and an aperture limiting element having a limiting hole for limiting the diameter of the laser beam incident on the objective lens is provided, and the polarization direction of the laser light is determined by the disc. The laser light source is arranged so as to be substantially parallel to the radial direction of the disk-shaped recording medium, and the restriction of the diameter of the light beam by the aperture limiting element is made different between the radial direction and the tangential direction of the disk-shaped recording medium. The numerical aperture in the tangential direction is smaller than the numerical aperture in the radial direction.

  In order to solve the above-described problems, the disk drive device of the present invention includes a rising mirror that reflects each emitted laser beam toward two types of disk-shaped recording media as a component of the optical pickup, An objective lens for condensing each laser beam reflected by the mirror on the recording surface of each disk-shaped recording medium, and an aperture limiting element having a limiting hole for limiting the diameter of the laser beam incident on the objective lens are provided. The polarization direction of the laser beam is made substantially parallel to the radial direction of the disk-shaped recording medium, and the diameter limit of the light beam by the aperture limiting element is made different between the radial direction and the tangential direction of the disk-shaped recording medium, and the objective lens The numerical aperture in the tangential direction is smaller than the numerical aperture in the radial direction.

  Therefore, in the optical pickup and the disk drive device of the present invention, the size of the laser beam in the tangential direction of the disk-shaped recording medium is smaller than the size of the disk-shaped recording medium in the radial direction.

  The optical pickup according to the present invention has a first laser beam having a first wavelength and a second wavelength corresponding to the type of the disc-shaped recording medium, for two types of disc-shaped recording media having different substrate thicknesses and recording densities. An optical pickup that is irradiated with a second laser beam having a rising mirror that reflects each emitted laser beam toward each disk-shaped recording medium, and each laser beam that is reflected by the rising mirror An objective lens for condensing on the recording surface of a disk-shaped recording medium, and an aperture limiting element having a limiting hole for limiting the diameter of the laser beam incident on the objective lens, and the polarization direction of the laser light is a disk-shaped recording The laser light source is arranged so as to be substantially parallel to the radial direction of the medium, and the limitation of the light beam diameter by the aperture limiting element is different between the radial direction and the tangential direction of the disk-shaped recording medium. And the numerical aperture in the tangential direction of the objective lens is characterized in that smaller than the numerical aperture in the radial direction.

  Therefore, while maintaining a good spot diameter on the recording surface of the disk-shaped recording medium without deteriorating jitter and maintaining good performance of the optical pickup, the optical pickup can be made thinner and thinner without increasing cost. Miniaturization can be achieved.

  In the invention described in claim 2, since the numerical aperture in the radial direction of the objective lens is 1.1 times or less than the numerical aperture in the tangential direction, the laser beam on the recording surface of the disc-shaped recording medium is reduced. The spot diameter does not become extremely large in the radial direction, and good recording / reproducing performance of the information signal of the optical pickup can be maintained.

  In the invention described in claim 3, since the restriction hole of the opening restriction element is formed in the shape of a long hole in the radial direction, the restriction hole can be easily formed, resulting in an increase in manufacturing cost. There is no.

  The disk drive device according to the present invention includes a disk table on which two types of disk-shaped recording media having different substrate thicknesses and recording densities are respectively mounted, and the disk-shaped recording medium with respect to the disk-shaped recording medium mounted on the disk table. A disk drive device comprising: an optical pickup that is irradiated with a first laser beam having a first wavelength corresponding to the type of the second laser beam and a second laser beam having a second wavelength; A rising mirror that reflects each laser beam emitted toward each disk-shaped recording medium; an objective lens that focuses each laser beam reflected by the rising mirror on the recording surface of each disk-shaped recording medium; An aperture limiting element having a limiting hole that limits the diameter of the laser beam incident on the lens, and the polarization direction of the laser beam is a disk-shaped recording The laser light source is arranged so as to be substantially parallel to the radial direction of the body, and the restriction of the diameter of the light beam by the aperture limiting element is made different between the radial direction and the tangential direction of the disk-shaped recording medium, and the objective lens in the tangential direction The numerical aperture is smaller than the numerical aperture in the radial direction.

  Accordingly, a good spot diameter on the recording surface of the disk-shaped recording medium is ensured without deteriorating jitter to maintain the good performance of the disk drive apparatus, and the disk drive apparatus is thin without increasing the cost. And miniaturization can be achieved.

  In the invention described in claim 5, since the numerical aperture in the radial direction of the objective lens is 1.1 times or less than the numerical aperture in the tangential direction, the laser beam on the recording surface of the disc-shaped recording medium is reduced. The spot diameter does not become extremely large in the radial direction, and good recording / reproducing performance of the information signal of the disk drive device can be maintained.

  In the invention described in claim 6, since the restriction hole of the opening restriction element is formed in the shape of a long hole in the radial direction, the restriction hole can be easily formed, resulting in an increase in manufacturing cost. There is no.

  The best mode of an optical pickup and a disk drive apparatus according to the present invention will be described below with reference to the accompanying drawings.

  The disk drive device 1 is configured by arranging required members and mechanisms in an outer casing 2 (see FIG. 1), and the outer casing 2 has a disk insertion slot (not shown).

  A chassis (not shown) is disposed in the outer casing 2, and the disk table 3 is fixed to the motor shaft of a spindle motor attached to the chassis.

  Parallel guide shafts 4 and 4 are attached to the chassis, and a lead screw 5 that is rotated by a feed motor (not shown) is supported.

  The optical pickup 6 includes a moving base 7, required optical components provided on the moving base 7, and an objective lens driving device 8 disposed on the moving base 7, and is provided at both ends of the moving base 7. The bearing portions 7a and 7b are slidably supported by the guide shafts 4 and 4, respectively. When a nut member (not shown) provided on the moving base 7 is screwed into the lead screw 5 and the lead screw 5 is rotated by the feed motor, the nut member is sent in a direction corresponding to the rotation direction of the lead screw 5, The pickup 6 is moved in the radial direction of the disc-shaped recording medium 100 mounted on the disc table 3.

  As the disc-shaped recording medium 100, for example, a DVD 100a and a CD 100b are used.

  In the disk drive device 1 configured as described above, when the disk table 3 is rotated in accordance with the rotation of the spindle motor, the disk-shaped recording medium 100 mounted on the disk table 3, that is, the DVD 100a or the CD 100ba is loaded. At the same time, the optical pickup 6 is moved in the radial direction (R direction shown in FIG. 2) of the disc-shaped recording medium 100 to perform a recording operation or a reproducing operation on the disc-shaped recording medium 100.

  As shown in FIG. 3, the optical pickup 6 includes a first laser light source (semiconductor laser) 9, a second laser light source (semiconductor laser) 10, a first grating 11, a second grating 12, and a coupling lens 13. , A first beam splitter 14, a second beam splitter 15, a collimator lens 16, a rising mirror 17, an aperture limiting element 18, an objective lens 19, an adjustment lens 20 and a light receiving element 21.

  The first laser light source 9 emits first laser light having a wavelength of 660 nm (first wavelength), for example, and the second laser light source 10 has a wavelength of 785 nm (second wavelength, for example). ) Is emitted. When an information signal is recorded or reproduced on one disk-shaped recording medium 100, that is, the DVD 100a, a laser beam having a wavelength of 660 nm is emitted from the first laser light source 9, and the other disk-shaped recording medium 100, When the information signal is recorded on or reproduced from the CD 100b, the second laser light source 10 emits laser light having a wavelength of 785 nm.

  The first grating 11 is disposed on the optical path of the first laser light emitted toward the DVD 100a, and the second grating 12 is disposed on the optical path of the second laser light emitted toward the CD 100b, Both are for generating three beams (0th order light and ± 1st order light) for tracking servo.

  The coupling lens 13 is disposed in the optical path between the second grating 12 and the second beam splitter 15, and has a function of changing the optical magnification of the emitted second laser light. .

  The first beam splitter 14 reflects the first laser light emitted from the first laser light source 9 by the separation surface 14 a and guides it to the collimator lens 16, and reflects the laser light reflected by the disk-shaped recording medium 100. It has a function of transmitting the return light and guiding it to the light receiving element 21.

  The second beam splitter 15 reflects the second laser light emitted from the second laser light source 10 by the separation surface 15a and guides it to the collimator lens 16, and reflects the laser light reflected by the disc-shaped recording medium 100. It has a function of transmitting the return light and guiding it to the light receiving element 21.

  The collimator lens 16 has a function of converting the incident laser beam into a parallel beam, and the rising mirror 17 has a function of reflecting the laser beam and guiding it to the objective lens 19 or the collimator lens 16.

  The aperture limiting element 18 is disposed in the optical path between the rising mirror 17 and the objective lens 19, and has a limiting hole 18 a that limits the diameter of the laser beam incident on the objective lens 19.

  The objective lens 19 has a function of condensing incident laser light on a recording track of the disk-shaped recording medium 100.

  The adjustment lens 20 is a lens for adjusting the magnification of the laser beam.

  As shown in FIG. 4, the restriction hole 18a of the opening restriction element 18 is formed in an elongated hole shape that is long in the radial direction (RAD direction) with respect to the tangential direction (TAN direction) of the disc-shaped recording medium 100. The edge is composed of two parallel straight portions 18b and 18b and arc portions 18c and 18c located between the straight portions 18b and 18b.

  For example, when the length Lt in the TAN direction of the limiting hole 18a is 1, the opening limiting element 18 has a length Lr in the RAD direction that is greater than 1 and 1.1 or less. Therefore, the objective lens 19 has a numerical aperture NAt in the TAN direction that is smaller than the numerical aperture NAr in the RAD direction. For example, the numerical aperture NAt in the TAN direction is 0.6 and the numerical aperture NAr in the RAD direction is 0.65. ing.

  The optical pickup 6 includes the first laser light source 9 and the second laser in such a direction that the polarization directions of the first laser light and the second laser light are substantially parallel to the radial direction of the disc-shaped recording medium 100. A light source 10 is arranged. Therefore, the intensity of the laser beam is stronger in the TAN direction than in the RAD direction in the emission state, but is rotated by 90 ° by a wavelength plate (not shown), for example, before reaching the disc-shaped recording medium 100. In the state of passing through the aperture limiting element 18, the intensity distribution is stronger in the RAD direction than in the TAN direction. In other words, the direction in which the intensity of the laser light is strong coincides with the longitudinal direction of the restriction hole 18a of the aperture limiting element 18, and the direction in which the intensity of the laser light is weak coincides with the short direction of the restriction hole 18a.

  In general, since the TAN direction has a large tolerance for jitter, as described above, the jitter is hardly deteriorated by matching the direction in which the intensity of the laser light is weak with the short direction of the limiting hole 18a of the aperture limiting element 18. A good spot diameter on the recording surface of the disk-shaped recording medium 100 can be secured without causing deterioration of jitter.

  In the optical pickup 6 configured as described above, the first laser light source 9 emits the first laser light having the first wavelength, that is, the first laser light having the wavelength of 660 nm corresponding to the DVD 100a. Then, the first laser light is diffracted by the first grating 11 and divided into a main light beam and a pair of sub light beams, reflected by the separation surface 14 a of the first beam splitter 14, and guided to the collimator lens 16. It is burned.

  The first laser light is converted into a parallel light beam by the collimator lens 16, reflected by the rising mirror 17, the diameter of the light beam is limited by the aperture limiting element 18, and the DVD 100 a mounted on the disc table 3 through the objective lens 19. Irradiates the recording surface. The first laser light irradiated on the recording surface of the DVD 100a is reflected by the recording surface and returned as first light again through the objective lens 19, the aperture limiting element 18, the rising mirror 17, and the collimator lens 16. The light enters the beam splitter 14. The return light incident on the first beam splitter 14 is transmitted through the separation surface 14 a of the first beam splitter 14, and further transmitted through the separation surface 15 a of the second beam splitter 15 to be received through the adjustment lens 20. For example, the information signal is reproduced from the DVD 100a by being incident on the element 21.

  On the other hand, when the second laser light having the second wavelength, that is, the second laser light having a wavelength of 785 nm corresponding to the CD 100b is emitted from the second laser light source 10, the second laser light is The light beam is diffracted by the second grating 12 and divided into a main light beam and a pair of sub light beams, is incident on the second beam splitter 15 through the coupling lens 13, and is reflected by the separation surface 15a of the second beam splitter 15. Is incident on the first beam splitter 14. The second laser light incident on the first beam splitter 14 is transmitted through the separation surface 14 a and guided to the collimator lens 16.

  The second laser light is converted into a parallel light beam by the collimator lens 16, reflected by the rising mirror 17, the diameter of the light beam is limited by the aperture limiting element 18, and the CD 100 b mounted on the disk table 3 through the objective lens 19. Irradiates the recording surface. The second laser light irradiated onto the recording surface of the CD 100b is reflected by the recording surface and returned as first light again through the objective lens 19, the aperture limiting element 18, the rising mirror 17, and the collimator lens 16. The light enters the beam splitter 14. The return light incident on the first beam splitter 14 is transmitted through the separation surface 14 a of the first beam splitter 14, and further transmitted through the separation surface 15 a of the second beam splitter 15 to be received through the adjustment lens 20. For example, the information signal is reproduced from the CD 100b by being incident on the element 21.

  Next, the height of the optical pickup 6 will be described (see FIG. 5).

  In the optical pickup 6, a working distance (WD) is required between the objective lens 19 and the disk-shaped recording medium 100 to allow surface vibration of the disk-shaped recording medium. The WD is determined based on the standard surface deflection amount of the CD 100b which is a disk-shaped recording medium having a low recording density, and the focal position of the objective lens 19 is determined in consideration of the WD.

The surface run-out amount of the CD 100b is ± 0.5 mm on the standard, the thickness of the CD 100b is 1.2 mm, and the thickness of the DVD 100a is 0.6 mm. The difference in distance (WD) from the upper surface of the objective lens 19 to the lower surface of the disc-shaped recording medium 100 is a value obtained by dividing the difference in thickness between the DVD 100a and the CD 100b by the refractive index, and the refractive index is 1.5.
0.6 / 1.5 = 0.4 (mm)
It becomes.

Therefore, the working distance WD1 in the DVD 100a is
WD1 = 0.5 + 0.4 = 0.9 (mm),
Working distance WD2 in CD100b is more than the allowable amount of CD runout.
WD2 = 0.5 (mm)
It becomes. At this time, the focal length of the objective lens 19 is set to 1.9 mm.

  As described above, the numerical aperture NA of the objective lens 19 is set such that the numerical aperture NAt in the TAN direction is 0.6 and the numerical aperture NAr in the RAD direction is 0.65.

The diameter D of the laser beam F is determined by the numerical aperture NAt of the objective lens 19 in the TAN direction because the folding direction of the rising mirror 17 is the direction along the TAN direction.
D = 2 × 0.6 × 1.9 = 2.28 (mm)
It becomes.

In the case of the DVD 100a, the distance A required from the lower end of the objective lens 19 to the upper end of the light flux F is determined by the thickness of the DVD 100a. Therefore, an amount obtained by dividing the thickness of the DVD 100a by the refractive index is required, and the distance A is
A = 0.6 / 1.5 + α
It becomes. α is a margin considering the error of each value, and when α = 0.05 (mm),
A = 0.4 + 0.05 = 0.45 (mm)
It becomes.

The height H of the optical pickup 6 is defined by the distance from the lower surface to the lower surface of the disc-shaped recording medium 100, and the height H is
H = WD1 + t + A + D + β
It becomes. t is the thickness of the objective lens 19, and β is a margin in consideration of an error of each value. If t = 1 (mm) and β = 0.5 (mm),
H = 0.9 + 1 + 0.45 + 2.28 + 0.5 = 5.13 (mm)
It becomes.

  Accordingly, the height of the optical pickup 6 is reduced by 0.19 mm compared to the conventional optical pickup using the aperture limiting element d having the circular limiting hole e.

  As described above, in the optical pickup 6, the polarization direction of the laser light is made substantially parallel to the RAD direction of the disk-shaped recording medium 100, and the diameter of the light beam by the aperture limiting element 18 is limited. The numerical aperture NAt in the TAN direction of the objective lens 19 is made smaller than the numerical aperture NAr in the RAD direction so that the RAD direction and the TAN direction of the recording medium 100 are different.

  Therefore, a good spot diameter on the recording surface of the disc-shaped recording medium 100 is secured without causing deterioration of jitter to maintain the good performance of the optical pickup 6 and at the same time, the optical pickup 6 has no increase in cost. Thinning and miniaturization can be achieved.

  In general, if the numerical aperture NAr in the RAD direction is too large relative to the numerical aperture NAt in the TAN direction of the objective lens, the tilt margin in the RAD direction of the objective lens is reduced, and the information signal recording / reproducing performance of the optical pickup 6 is reduced. May deteriorate. If the numerical aperture NAt in the TAN direction becomes too small, the spot diameter of the laser beam on the recording surface of the disc-shaped recording medium 100 becomes extremely large, and the information signal recording / reproducing performance of the optical pickup 6 deteriorates. Therefore, as described above, in the optical pickup 6, the length Lr in the RAD direction of the limiting hole 18a of the aperture limiting element 18 is 1.1 or less with respect to the length Lt in the TAN direction.

  Therefore, the tilt margin in the RAD direction is not reduced, and the spot diameter of the laser beam on the recording surface of the disc-shaped recording medium 100 is not extremely increased in the TAN direction, and the information signal of the optical pickup 6 is It is possible to maintain good recording / reproducing performance.

  Further, since the restriction hole 18a of the opening restriction element 18 is formed in the shape of a long hole composed of straight portions 18b and 18b and arc portions 18c and 18c that are easy to process, the restriction hole 18a can be easily formed. The manufacturing cost will not increase.

  The shape of the limiting hole of the aperture limiting element is not limited to the long hole shape as shown in FIG. 4. For example, as shown in FIG. 6, the length Lr in the RAD direction becomes the length Lt in the TAN direction. On the other hand, you may form in a long ellipse shape. Also in this case, it is desirable that the length Lr in the RAD direction of the limiting hole 18d of the aperture limiting element 18A is 1.1 or less with respect to the length Lt in the TAN direction.

  The specific shapes and structures of the respective parts shown in the above-described best mode are merely examples of the implementation of the present invention, and the technical scope of the present invention is limited by these. It should not be interpreted in a general way.

2 to 6 show the best mode for carrying out the present invention, and this figure is a schematic perspective view of a disk drive device. FIG. It is a perspective view which shows the relationship between the moving direction of an objective lens, and a disk-shaped recording medium. It is a conceptual diagram which shows the structure of an optical pick-up. It is an enlarged plan view showing the shape of the restriction hole of the opening restriction element. It is a side view for demonstrating the height of an optical pick-up. It is an enlarged plan view which shows the shape of the limiting hole of another opening limiting element. It is a side view for demonstrating the height of the conventional optical pick-up.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Disk-shaped recording medium, 1 ... Disk drive apparatus, 3 ... Disk table, 6 ... Optical pick-up, 9 ... 1st laser light source, 10 ... 2nd laser light source, 17 ... Rising mirror, 18 ... Opening restriction element , 18a ... limiting hole, 19 ... objective lens, 18A ... aperture limiting element, 18d ... limiting hole

Claims (6)

A first laser beam having a first wavelength and a second laser beam having a second wavelength corresponding to the type of the disc-shaped recording medium for two types of disc-shaped recording media having different substrate thicknesses and recording densities. Is an optical pickup that is irradiated,
A rising mirror that reflects each emitted laser beam toward each disk-shaped recording medium;
An objective lens for condensing each laser beam reflected by the rising mirror onto the recording surface of each disk-shaped recording medium;
An aperture limiting element having a limiting hole that limits the diameter of the laser beam incident on the objective lens,
The laser light source is arranged so that the polarization direction of the laser light is substantially parallel to the radial direction of the disk-shaped recording medium,
The restriction of the beam diameter by the aperture limiting element is made different between the radial direction and the tangential direction of the disc-shaped recording medium, and the numerical aperture in the tangential direction of the objective lens is made smaller than the numerical aperture in the radial direction. Optical pickup. The optical pickup according to claim 1, wherein the numerical aperture of the objective lens in the radial direction is 1.1 times or less the numerical aperture in the tangential direction. The optical pickup according to claim 1, wherein the limiting hole of the aperture limiting element is formed in a long hole shape that is long in the radial direction. A disc table on which two types of disc-shaped recording media having different substrate thicknesses and recording densities are separately mounted, and a first corresponding to the type of the disc-shaped recording medium with respect to the disc-shaped recording medium mounted on the disc table. A disk drive device comprising: an optical pickup that is irradiated with a first laser beam having a second wavelength and a second laser beam having a second wavelength;
The above optical pickup
A rising mirror that reflects each emitted laser beam toward each disk-shaped recording medium;
An objective lens for condensing each laser beam reflected by the rising mirror onto the recording surface of each disk-shaped recording medium;
An aperture limiting element having a limiting hole that limits the diameter of the laser beam incident on the objective lens,
The laser light source is arranged so that the polarization direction of the laser light is substantially parallel to the radial direction of the disk-shaped recording medium,
The restriction on the diameter of the light beam by the aperture limiting element is made different between the radial direction and the tangential direction of the disc-shaped recording medium, and the numerical aperture in the tangential direction of the objective lens is made smaller than the numerical aperture in the radial direction. Disk drive device. The disk drive device according to claim 4, wherein the numerical aperture of the objective lens in the radial direction is 1.1 times or less the numerical aperture in the tangential direction. The disk drive device according to claim 4, wherein the restriction hole of the opening restriction element is formed in a long hole shape that is long in the radial direction.

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