JP2006236414A - Optical pickup and optical disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain compatibility among various kinds of optical disks by performing optimum aperture control for light beams different in wavelengths. <P>SOLUTION: This pickup has a 1st output section for emitting a light beam of a 1st wavelength, a 2nd output section for emitting a light beam of a 2nd wavelength, a 3rd output section for emitting a light beam of a 3rd wavelength, an objective lens 32 to focus the light beams emitted from the 1st-3rd output sections on the signal recording surface of an optical disk, a diffraction optical element 34 which has an annular 1st diffraction area 34a, and a 2nd diffraction area 34b formed in the 1st diffraction area, and a photo detector 35 to detect return light reflected on the optical disk. The 1st diffraction area 34a passes the light beam of the 1st wavelength and diffracts the light beams of the 2nd and 3rd wavelengths. The 2nd diffraction area 34b passes the light beams of the 1st and 2nd wavelengths and diffracts the light beam of the 3rd wavelength. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical pickup and an optical disc apparatus for recording and / or reproducing information on a plurality of types of information recording media such as optical discs using light beams having different wavelengths.

  Currently, a next-generation optical disc format that uses a blue-violet semiconductor laser light source having a wavelength of about 400 to 410 nm and an objective lens with NA (numerical aperture) = 0.85 is employed. As an optical disk irradiated with laser light having a wavelength of about 405 nm, a structure in which the cover layer for protecting the signal recording layer is thin, for example, 0.1 mm has been proposed.

  In providing an optical pickup compatible with these next-generation optical discs, those having compatibility with optical discs having different formats such as conventional CD (Compact Disc) and DVD (Digital Versatile Disc) are desired. Thus, there is a need for an optical pickup and an optical disk apparatus that have compatibility between optical disks of different formats that have different disk structures and accompanying laser specifications.

  An apparatus having compatibility between optical disks of different formats has a configuration in which light beams of different wavelengths emitted from a light source are condensed on a signal recording surface of each optical disk.

  Optical disks on which signals are recorded / reproduced by such an optical pickup have different numerical apertures (NA) depending on formats. Therefore, it is necessary to limit the opening of such an optical pickup, and this has been dealt with by providing an aperture or an interference filter whose opening amount can be switched.

  However, the aperture and the interference filter require precise alignment with the objective lens, and the assembly process is complicated. Furthermore, since this aperture and interference filter need to be mounted on the actuator integrally with the objective lens, the sensitivity of the actuator decreases with increasing weight, the assembly process increases, the number of parts increases, and the cost increases with these. There was a problem.

JP-A-9-306018

  An object of the present invention is to enable optimum aperture limitation according to the wavelength for light beams having a plurality of different wavelengths by a common diffractive optical element, which is favorable for optical disks having different formats. An object of the present invention is to provide an optical pickup capable of reading and writing signals and an optical disk apparatus using the optical pickup.

  In order to achieve this object, an optical pickup according to the present invention includes a first emitting unit that emits a light beam having a first wavelength, a second emitting unit that emits a light beam having a second wavelength, A third emission unit that emits a light beam having a wavelength of 3, an objective lens that focuses the light beams emitted from the first to third emission units on the signal recording surface of the optical disc, and first to third components A diffractive optical element that is disposed on the optical path of a light beam having a wavelength and has a ring-shaped first diffraction region and a second diffraction region provided inside the first diffraction region; The first diffraction region transmits the light beam of the first wavelength, diffracts the light beam of the second and third wavelengths, and the second diffraction region, The diffraction region transmits the light beams of the first and second wavelengths and the third wave. Diffracting the light beam.

  In order to achieve the above-described object, an optical disc apparatus according to the present invention includes an optical pickup that records and / or reproduces information on a plurality of different types of optical discs, and a disc rotation driving unit that rotates the optical disc. In the optical disc apparatus, the optical pickup includes a first emitting unit that emits a light beam having a first wavelength, a second emitting unit that emits a light beam having a second wavelength, and a light beam having a third wavelength. A third emission section that emits light, an objective lens that condenses the light beams emitted from the first to third emission sections on the signal recording surface of the optical disc, and the light beams of the first to third wavelengths A diffractive optical element that is disposed on the road and has a ring-shaped first diffractive region and a second diffractive region provided inside the first diffractive region, and returns light reflected by the optical disc is detected. Photodetector And the first diffraction region transmits the light beam having the first wavelength and diffracts the light beam having the second and third wavelengths, and the second diffraction region has the first and second wavelengths. And the light beam of the third wavelength is diffracted.

  The optical pickup according to the present invention can obtain the aperture amount according to the format by performing the optimum aperture limitation according to the wavelength with respect to the plurality of different light beams by the common diffractive optical element. As a result, it is possible to read and write a good signal with respect to the optical disc, and to eliminate complicated positioning and the like, and it is possible to prevent an increase in weight, an increase in the number of parts, and an increase in cost.

  In addition, the optical disc apparatus according to the present invention can obtain an aperture amount according to the format by performing the optimum aperture limitation according to the wavelength of the light beam by a common diffractive optical element, and can be applied to an optical disc having a different format. On the other hand, it is possible to read and write a good signal and realize compatibility with a plurality of types of optical discs, simplify the configuration, simplify the assembly process, and reduce the size of the apparatus.

  Hereinafter, an optical disk apparatus using an optical pickup to which the present invention is applied will be described with reference to the drawings.

  As shown in FIG. 1, an optical disc apparatus 1 to which the present invention is applied includes an optical pickup 3 for recording / reproducing information from / on an optical disc 2, a spindle motor 4 as a driving means for rotating the optical disc 2, and an optical pickup 3. And a feed motor 5 for moving the optical disk 2 in the radial direction. This optical disk apparatus 1 is an optical disk apparatus that realizes compatibility between three standards for recording and / or reproducing (hereinafter referred to as recording / reproducing) with respect to three types of optical disks 2 having different formats.

  The optical disk 2 used here is, for example, a CD (Compact Disc), a DVD (Digital Versatile Disc), a CD-R (Recordable) and a DVD-R (Recordable) that allow additional recording of information, and information can be rewritten. CD-RW (ReWritable), DVD-RW (ReWritable), DVD + RW (ReWritable), and other optical discs, and high-density recording using a semiconductor laser with a short emission wavelength of about 405 nm (blue-violet) It is a density recording optical disk, a magneto-optical disk, or the like.

  In particular, as the three types of optical discs in which information is reproduced or recorded by the optical disc apparatus 1 in the following, a high-density recording using a light beam having a protective substrate thickness of 0.1 mm and a wavelength of about 405 nm as recording / reproducing light is possible. Optical disk 11, a second optical disk 12 such as a DVD using a light beam having a protective substrate thickness of 0.6 mm and a wavelength of about 655 nm as recording / reproducing light, and a light beam having a protective substrate thickness of 1.2 mm and a wavelength of about 785 nm Will be described as being used with a third optical disk 13 such as a CD that uses the recording / reproducing light.

  In the optical disc apparatus 1, the spindle motor 4 and the feed motor 5 are driven and controlled in accordance with the disc type by a servo control unit 9 that is controlled based on a command from a system controller 7 that also serves as a disc type discriminating unit. The first optical disk 11, the second optical disk 12, and the third optical disk 13 are driven at a predetermined number of rotations.

  The optical pickup 3 is an optical pickup having a three-wavelength compatible optical system. The optical pickup 3 irradiates a recording layer of an optical disc having a different standard with a light beam having a different wavelength and detects reflected light from the recording layer of the light beam. The optical pickup 3 supplies a signal corresponding to each light beam from the detected reflected light to the preamplifier unit 14.

  The output of the preamplifier unit 14 is sent to a signal modulator / demodulator and an error correction code block (hereinafter referred to as a signal modulation / demodulation & ECC block) 15. The signal modulation / demodulation and ECC block 15 performs signal modulation, demodulation, and addition of ECC (error correction code). The optical pickup 3 irradiates the recording layer of the optical disc 2 rotating according to the signal modulation / demodulation and the command of the ECC block 15, and records or reproduces the signal on the optical disc 2.

  The preamplifier unit 14 is configured to generate a focus error signal, a tracking error signal, an RF signal, and the like based on a signal corresponding to a light beam detected differently for each format. In accordance with the type of the optical disk 2 to be recorded or reproduced, predetermined processing such as demodulation and error correction processing based on the standard of the optical disk 2 is performed by the servo control circuit 9, the signal modulation / demodulation, the ECC block 15, and the like. .

  Here, for example, if the recording signal demodulated by the signal modulation / demodulation & ECC block 15 is for data storage of a computer, it is sent to the external computer 17 via the interface 16. Thereby, the external computer 17 etc. can receive the signal recorded on the optical disk 2 as a reproduction signal.

  If the recording signal demodulated by the signal modulation / demodulation & ECC block 15 is for audio visual, it is converted from digital to analog by the D / A converter of the D / A and A / D converter 18 and supplied to the audio visual processor 19. Is done. Audio visual processing is performed by the audio visual processing unit 19 and transmitted to an external imaging / projection device (not shown) or the like via the audio visual signal input / output unit 20.

  In the optical pickup 3, for example, control of the feed motor 5 for moving to a predetermined recording track on the optical disk 2, control of the spindle motor 4, and two axes for holding an objective lens serving as light condensing means in the optical pickup 3 The servo control circuit 9 controls driving of the actuator in the focusing direction and driving control in the tracking direction.

  The laser control unit 21 controls the laser light source of the optical pickup 3. In particular, in this specific example, the laser control unit 21 performs control to vary the output power of the laser light source between the recording mode and the reproduction mode. Also, control is performed to vary the output power of the laser light source depending on the type of the optical disc 2. The laser control unit 21 switches the laser light source of the optical pickup 3 in accordance with the type of the optical disc 2 detected by the disc type determination unit 22.

  The disc type discriminating unit 22 can detect different formats of the optical disc 2 from the surface reflectance, the shape and the external shape difference between the first to third optical discs 11, 12 and 13.

  Each block constituting the optical disc apparatus 1 is configured to be able to perform signal processing based on the specification of the optical disc 2 to be mounted, according to the detection result in the disc type discriminating unit 22.

  The system controller 7 determines the type of the optical disk 2 based on the detection result sent from the disk type determination unit 22. As a method for discriminating the type of the optical disc, if the optical disc is of a type that is housed in a cartridge, there is a method in which a detection hole is provided in the cartridge and detected using a contact detection sensor or a push switch. In addition, the recording layer in the same optical disc is discriminated with respect to which recording layer is recorded / reproduced based on information by table information (TOC) recorded in premastered pits and grooves in the innermost circumference of the optical disc. Can be used.

  The servo control circuit 9 performs recording and / or reproduction by, for example, detecting the relative position between the optical pickup 3 and the optical disk 2 (including the case of detecting the position based on the address signal recorded on the optical disk 2). The area can be determined.

  The optical disc apparatus 1 configured as described above rotates the optical disc 2 by the spindle motor 4, drives and controls the feed motor 5 in accordance with a control signal from the servo control unit 9, and controls the optical pickup 3 on the optical disc 2. By moving to a position corresponding to a desired recording track, information is recorded on and reproduced from a plurality of optical disks 2 having different recording densities and formats.

  Here, the recording / reproducing optical pickup 3 described above will be described in detail.

  As shown in FIG. 2, the optical pickup 3 to which the present invention is applied includes a first light source unit 31 having a first emitting unit that emits a light beam having a first wavelength, and a light beam having a second wavelength. A second light source part 32 having a second emission part for emitting and a third emission part for emitting a light beam of a third wavelength; and a light beam emitted from the first to third emission parts. An objective lens 33 that condenses on the signal recording surface of the optical disc 2, a first diffractive zone 34a that is disposed on the optical path of the light beam having the first to third wavelengths, and the first diffractive region. A diffractive optical element 34 having a second diffractive region 34b provided inside 34a, and a photodetector 35 for detecting return light reflected by the signal recording surface.

  The optical pickup 3 is disposed between the first to third emission units and the diffractive optical element 34, and is a coupling lens that converts the divergence angle of the light beam emitted from the first to third emission units. 36, an aberration correction unit 37 that is provided between the coupling lens 36 and the diffractive optical element 34 and corrects the aberration based on the signal detected by the photodetector 35, the aberration correction unit 37, and the diffractive optical element 34. Between the first beam splitter 38 and the first and second optical path branching means for branching the optical path of the return light reflected by the signal recording surface from the optical path of the forward path light and guiding it to the photodetector 35. The light path of the light beam emitted from the first light source section 31 and the optical path of the light beam emitted from the second light source section 32 are provided between the light source sections 31 and 32 and the coupling lens 36. Optical path synthesis hand As a second beam splitter 39.

  The first light source unit 31 includes a first emission unit that emits a light beam having a first wavelength of about 405 nm to the first optical disc 11. The second light source unit 32 includes a second emitting unit that emits a light beam having a second wavelength of about 655 nm to the second optical disc 12 and a wavelength of about 785 nm to the third optical disc 13. And a third emitting part for emitting a light beam of the third wavelength.

  The second beam splitter 39 has, for example, a mirror surface 39a having wavelength selectivity. The mirror surface 39a transmits the light beam emitted from the first emission part of the first light source part 31, and transmits the light beam emitted from the second and third emission parts of the second light source part 32. By reflecting, the optical paths of the respective light beams emitted from the first to third emission parts can be synthesized.

  The coupling lens 36 converts the divergence angle of the light beam emitted from each emission part of the first light source part 31 or the second light source part 32 and emits it as the substantially parallel light to the aberration correction unit 37 side.

  The aberration correction unit 37 is composed of, for example, a liquid crystal optical element that can change the refractive index by changing the voltage to be applied, and changes the refractive index based on the signal detected by the photodetector 35. Correct aberrations. In this embodiment, the liquid crystal optical element is provided as the aberration correction means. However, the present invention is not limited to this, and an actuator that moves the coupling lens 36 in the optical axis direction is provided as the aberration correction means. It may be configured. When the coupling lens actuator is provided, the generated aberration can be corrected by the actuator and the coupling lens.

  As shown in FIGS. 2 and 3, the diffractive optical element 34 is disposed between the first beam splitter 38 and the objective lens 33, and a ring-shaped first element is formed on one surface of the diffractive optical element 34 on the emission side. Diffractive region 34a and an annular second diffractive region 34b provided inside the first diffractive region 34a.

  The first diffraction region 34a transmits the light beam having the first wavelength and diffracts the light beams having the second and third wavelengths. Here, the first diffraction region 34a diffracts the light beams of the second and third wavelengths, so that the light beam passing through the first diffraction region 34a is emitted toward the objective lens 33. To prevent. In other words, the first diffraction region 34a is the same as the light beam having the second and third wavelengths that blocks the light beam that passes through this region and is emitted to the objective lens 33 and the optical disc side. To play a role.

  The second diffraction region 34b transmits the light beams having the first and second wavelengths and diffracts the light beam having the third wavelength. Here, the second diffraction region 34 b diffracts the light beam having the third wavelength, thereby preventing the light beam passing through the second diffraction region 34 b from being emitted toward the objective lens 33. In other words, the second diffraction region 34b plays the same role as the light beam having the third wavelength that blocks the light beam that passes through this region and is emitted toward the objective lens 33 and the optical disc. .

  That is, the first diffractive region 34 a limits the aperture of the light beam incident on the objective lens 33. Due to the first diffraction region 34 a, the light beam having the second wavelength passing through the inside of the first diffraction region 34 a is limited to an aperture of about 0.60 when entering the objective lens 33.

  The second diffractive region 34 b limits the opening of the light beam incident on the objective lens 33. Due to the second diffraction region 34b and the first diffraction region 34a described above, the light beam having the third wavelength passing through the region 34c inside the second diffraction region 34b becomes 0. The opening is limited to about 45.

  Further, a light shielding portion 34d for shielding the emitted light beam is formed outside the first diffraction region 34a of the diffractive optical element 34. When the light beam having the first wavelength that passes through the first diffraction region 34 a, the second diffraction region 34 b, and the region 34 c inside the second diffraction region is incident on the objective lens 33 by the light shielding portion 34 d. The aperture is limited to about 0.85.

  In the diffractive optical element 34, the first and second diffraction regions 34a and 34b are configured to be provided on one surface. However, the present invention is not limited to this. The diffraction region may be provided, and the second diffraction region may be provided on the other surface.

Next, the configuration of the first and second diffraction regions 34a and 34b will be described. A hologram is formed in the first and second diffraction regions 34a and 34b, and the shape of the hologram is a stepped shape having a predetermined number of steps. That is, as shown in FIG. 4A, the first and second diffraction regions 34a and 34b are stepped with a predetermined number of steps n (n is an integer of 2 or more). Stepped holograms having _first to (n-1) th step portions S ₁ , S ₂ ,... S _n-2 , S _n-1 are formed. A stepped hologram having diffraction surfaces f ₁ , f ₂ ,... F _n−1 , f _n is formed. For example, if there are 5 steps, as shown in FIG. 4B, n = 5, and this hologram includes the first to fourth step portions S ₁ , S ₂ , S ₃ , S ₄ . And have a first to fifth diffractive surfaces f ₁ , f ₂ , f ₃ , f ₄ , and f ₅ . The first and second diffractive regions 34a and 34b adjust the number of steps and the depth of each step, that is, the interval between the diffractive surfaces, to thereby adjust the first to third wavelengths that are used wavelengths. On the other hand, it can be selectively transmitted or diffracted. In the first and second diffraction regions, the number of steps may be the same or a different number of steps may be used.

The first and second diffraction area, for example, as shown in FIG. 4 (c), was formed by bonding member H ₂ of the frequency characteristic of the refractive index is different to the base material H ₁ is joined May be. When such a bonding member is bonded, the number of steps formed on the diffractive surface and the refractive index characteristics of the base material and the bonding member are changed to further transmit light corresponding to the wavelength. And the degree of freedom of diffraction can be increased.

  The first diffraction region 34a transmits almost all of the light beam having the first wavelength, and diffracts so that the 0th-order diffracted light (transmitted light) of the light beams having the second and third wavelengths becomes substantially zero. The number of steps and the depth of each step are selected. On the other hand, the second diffraction region 34b transmits almost all of the light beams having the first and second wavelengths, and diffracts so that the 0th-order diffracted light (transmitted light) of the third wavelength light beam becomes substantially zero. The number of steps and the depth of each step are selected.

FIG. 5 shows the diffraction of each wavelength used when the total groove depth, that is, the total depth of the exceptional portion is changed in a hologram having a predetermined number of steps with a member having a predetermined refractive index. Changes in efficiency (transmittance) are shown. In FIG. 5, each curve represents the ratio of the amount of each diffracted light emitted to the total amount of incident laser light, that is, the diffraction efficiency, and the curves L ₁₀ and L ₁₁ each have a wavelength of 405 nm. The first order diffracted light (transmission) and ± 1st order diffracted light of the (first wavelength) light beam are shown, and the curves L ₂₀ and L ₂₁ represent the 0th order of the light beam of wavelength 655 nm (second wavelength), respectively. Folded light (transmitted) and ± 1st order diffracted light are shown, and curves L ₃₀ and L ₃₁ indicate 0th order diffracted light (transmitted) and ± 1st order diffracted light of a light beam having a wavelength of 785 nm (third wavelength), respectively. It is. Here, from FIG. 5, the first diffraction region 34a is determined to have a total groove depth of about 0.8 μm (800 nm), and the second diffraction region 34b has a total groove depth of 3.9 μm (3900 nm). Determined to the extent.

  As shown in FIG. 5, the first diffraction region 34a formed with a total groove depth of about 0.8 μm transmits substantially 100% of the light beam with the first wavelength, and the light with the second and third wavelengths. The first-order diffracted light of the beam can be about 40%, and the 0th-order diffracted light can be about 0%. Further, as shown in FIG. 5, the second diffraction region 34b formed with a total groove depth of about 3.9 μm transmits substantially 100% of the light beams of the first and second wavelengths, and the third wavelength. The first order diffracted light of the light beam can be about 40%, and the 0th order diffracted light can be about 0%.

  When a light beam having a different wavelength is incident, the diffractive optical element 34 having the first and second diffractive regions 34a and 34b has a wavelength of one of the different wavelengths depending on the hologram shape formed in each diffractive region. A light beam having a certain first wavelength is transmitted through the first and second diffraction regions 34a and 34b, and a light beam having a second wavelength, which is the other one wavelength, is diffracted by the first diffraction region 34a. The light is shielded and transmitted through the second region 34b and the inner region 34c, which are the regions inside the first diffraction region 34a, and the light beam having the third wavelength, which is another one wavelength, is transmitted through the first and first regions. The second diffractive regions 34a and 34b can be diffracted and shielded so that only the region 34c inside the second diffractive region 34b can be transmitted. That is, the diffractive optical element 34 transmits light beams of different wavelengths. To that wavelength Flip and performs aperture restriction of the light beam to be incident on the objective lens 33 can be a predetermined number of openings to be described later.

  The objective lens 33 is a three-wavelength compatible objective lens. The numerical aperture of the objective lens 33 is 0.85 for the first wavelength, 0.60 for the second wavelength, and 0.45 for the third wavelength. The objective lens 33 can focus the light beam having the first wavelength whose divergence angle has been converted by the coupling lens 36 on the first optical disk 11 having the first protective substrate thickness. Further, the second wavelength light beam having the divergence angle converted by the coupling lens 36 is applied to the second disk 12 having the second protective substrate thickness, and the third protective substrate thickness is applied to the third disk. A light beam having a third wavelength whose divergence angle is converted by the coupling lens 36 can be focused on the optical disk 13. The objective lens 33 achieves compatibility with three different wavelengths by, for example, a so-called zone division type lens.

  The objective lens 33 and the above-described diffractive optical element 34 are arranged on a unit (not shown). By arranging the objective lens 33 and the diffractive optical element 34 on the unit, alignment and the like can be simplified and assembly can be facilitated.

  The first beam splitter 38 is provided on the optical path between the aberration correcting unit 37 and the diffractive optical element 34, and the mirror surface 38 a transmits the forward light to the objective lens 33 side and returns from the optical disk 2. The light is branched and emitted to the photodetector 35 side. Between the first beam splitter 38 and the light detector 35, an optical element 41 such as a cylindrical lens for focusing the light beam branched in the optical path on the light receiving surface of the light detector 35 is provided.

  Next, the optical path of the light beam emitted from the first and second light source units 31 and 32 in the optical pickup 3 will be described. First, an optical path when information is read or written on the first optical disc 11 will be described.

  The disc type discriminating unit 22 that discriminates that the type of the optical disc 2 is the first optical disc 11 emits a light beam having the first wavelength from the first emitting unit of the first light source unit 31.

  As shown in FIGS. 2 and 3, the light beam having the first wavelength emitted from the first emission part of the first light source part 31 is transmitted through the mirror surface 39a of the second beam splitter 39, and The coupling lens 36 makes the light substantially parallel, and the aberration correction means 37 corrects the aberration generated on the signal recording surface of the optical disk and enters the first beam splitter 38.

  The light beam having the first wavelength incident on the first beam splitter 38 passes through the mirror surface 38 a and enters the diffractive optical element 34.

  The light beam having the first wavelength incident on the diffractive optical element 34 is transmitted through a first diffractive region 34a, a second diffractive region 34b, and a region 34c inside the second diffractive region 34b provided on the output side. Then, the numerical aperture is set to 0.85, and the light is emitted to the objective lens 33 side. At this time, the light beam having the first wavelength transmitted through the first and second diffraction regions 34a and 34b and the region 34c inside the second diffraction region is shielded by the light shielding portion 34d, thereby reducing the numerical aperture. The opening is limited to 0.85.

  The light beam of the first wavelength having a numerical aperture of 0.85 on the diffractive optical element 34 is appropriately focused on the signal recording surface 11 a of the first optical disk 11 by the objective lens 33.

  The light beam collected on the first optical disk 11 is reflected by the signal recording surface 11a, passes through the objective lens 33 and the diffractive optical element 34, is reflected by the first beam splitter 38, and is on the photodetector 35 side. Is emitted. The light beam having the first wavelength branched by the first beam splitter 38 is focused on the light receiving surface of the photodetector 35 by the optical element 41 and detected.

  Next, an optical path when information is read from or written to the second optical disk 12 will be described.

  The disc type discriminating unit 22 that discriminates that the type of the optical disc 2 is the second optical disc 12 emits a light beam having the second wavelength from the second emitting unit of the second light source unit 32.

  The light beam having the second wavelength emitted from the second emission part of the second light source part 32 is reflected by the mirror surface 39a of the second beam splitter 39 as shown in FIGS. The coupling lens 36 makes the light substantially parallel, and the aberration correction means 37 corrects the aberration generated on the signal recording surface of the optical disk and enters the first beam splitter 38.

  The light beam having the second wavelength incident on the first beam splitter 38 passes through the mirror surface 38 a and enters the diffractive optical element 34.

  The light beam having the second wavelength incident on the diffractive optical element 34 is diffracted by the first diffractive region 34a provided on the exit side, and the second diffractive region 34b and the second diffractive region 34b. The light passes through the inner region 34c, has a numerical aperture of 0.6, and is emitted toward the objective lens 33. At this time, the light beam of the second wavelength diffracted by the first diffraction region 34a does not enter the objective lens 33 or may interfere with the light beam transmitted through the diffractive optical element 34 even if it enters. Instead, the first diffraction region 34a can provide the same effect as shielding the diffracted light beam having the second wavelength.

  The second wavelength light beam having a numerical aperture of 0.6 on the diffractive optical element 34 is appropriately focused on the signal recording surface 12 a of the second optical disk 12 by the objective lens 33.

  Since the optical path on the return path side of the light beam reflected by the signal recording surface 12a of the second optical disc 12 is the same optical path as the light beam having the first wavelength described above, description thereof will be omitted.

  Next, an optical path when information is read from or written to the third optical disc 13 will be described.

  The disc type discriminating unit 22 that discriminates that the type of the optical disc 3 is the third optical disc 13 emits a light beam having the third wavelength from the third emitting unit of the second light source unit 32.

  As shown in FIGS. 2 and 3, the light beam of the third wavelength emitted from the third emission part of the second light source part 32 is reflected by the mirror surface 39a of the second beam splitter 39, and The divergence angle is converted by the coupling lens 36, the aberration generated on the signal recording surface of the optical disk is corrected by the aberration correction means 37, and is incident on the first beam splitter 38.

  The light beam having the third wavelength incident on the first beam splitter 38 passes through the mirror surface 38 a and enters the diffractive optical element 34.

  The light beam having the third wavelength incident on the diffractive optical element 34 is diffracted by the first diffractive region 34a and the second diffractive region 34b provided on the emission side, and inside the second diffractive region 34b. The numerical aperture is set to 0.45 and is emitted toward the objective lens 33 side. At this time, the light beam of the third wavelength diffracted by the first diffraction region 34a and the second diffraction region 34b does not enter the objective lens 33 or transmits through the diffractive optical element 34 even if it enters. Without interfering with the light beam, the first and second diffraction regions 34a and 34b can provide the same effect as shielding the light beam having the third wavelength to be diffracted.

  The third wavelength light beam having a numerical aperture of 0.45 on the diffractive optical element 34 is appropriately focused on the signal recording surface 13 a of the third optical disk 13 by the objective lens 33.

  Since the optical path on the return path side of the light beam reflected by the signal recording surface 13a of the third optical disc 13 is the same optical path as the light beam having the first wavelength described above, description thereof will be omitted.

  In the optical pickup 3 to which the present invention is applied, when light beams having first to third wavelengths having different wavelengths are incident on the common diffractive optical element 34 by the common diffractive optical element 34, The light beam is transmitted through the inside of the shielding part 34d, the light beam of the second wavelength is diffracted and shielded by the first diffraction region 34a, and the region inside the first diffraction region 34a is transmitted, and the third A light beam having a wavelength can be diffracted and shielded by the first and second diffraction regions 34a and 34b, and transmitted through the region inside the second diffraction region 34b. Aperture restriction can be performed with an aperture amount corresponding to the wavelength of the light beam. Therefore, the optical pickup 3 can obtain different opening amounts depending on the format, and can read and write a good signal with respect to an optical disc having a different format, and can eliminate complicated alignment and the like. Thus, an increase in weight, an increase in the number of parts, and an increase in cost can be prevented.

  In the optical pickup 3, the regions other than the first and second diffraction regions 34a and 34b of the diffractive optical element 34a are not particularly regions having a diffraction function, but are not limited thereto. You may comprise so that it may have a diffraction function. For example, a first diffraction region is disposed on one surface, and a third diffraction region serving as a first divergence angle conversion unit that diffracts only the light beam of the second wavelength and converts the divergence angle is disposed inside the first diffraction region. A second diffraction region is disposed on the other surface, and a fourth diffraction region serving as a second divergence angle conversion unit that diffracts only the light beam of the third wavelength and converts the divergence angle is provided on the inner side. You may comprise so that it may provide. The optical pickup having the first to fourth diffraction regions realizes further reduction in the number of parts, cost reduction, and further miniaturization.

  In the optical pickup 3, the first to third emission units are configured to be disposed in the first light source unit 31 or the second light source unit 32, but the present invention is not limited thereto. The first to third light emitting units are arranged in the light source unit, and an optimum aperture amount is obtained by a common diffractive optical element for light beams of three different wavelengths emitted from the light source unit. You may comprise so that opening restriction may be carried out.

  Next, an optical pickup 50 shown in FIG. 6 including a light source unit having first to third emission units will be described. In the following description, portions common to the optical pickup 3 described above are denoted by common reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 6, an optical pickup 50 to which the present invention is applied includes a first emission part that emits a light beam having a first wavelength, and a second emission part that emits a light beam having a second wavelength. , A light source unit 51 having a third emission unit that emits a light beam of a third wavelength, and the light recording beam emitted from the first to third emission units of the light source unit 51 to the signal recording surface of the optical disc 2 The objective lens 33 that condenses on the light source is disposed on the optical path of the light beams having the first to third wavelengths, and is provided inside the first diffractive region 34a having a ring shape and the inside of the first diffractive region 34a. A diffractive optical element 34 having a second diffractive region 34b and a photodetector 35 for detecting return light reflected by the signal recording surface are provided.

  The optical pickup 50 is disposed between the light source unit 51 and the diffractive optical element 34, and couples with a coupling lens 36 that converts the divergence angle of the light beam emitted from the first to third emission units, and the coupling. An aberration correction unit 37 that is provided between the lens 36 and the diffractive optical element 34 and corrects an aberration based on a signal detected by the photodetector 35, and is provided between the aberration correction unit 37 and the diffractive optical element 34. The first beam splitter 38, the first beam splitter 38, and the photodetector as optical path branching means for branching the optical path of the return light reflected by the signal recording surface from the optical path of the forward light and leading it to the photodetector 35. 35, and an optical element 41 that focuses the light beam on the light receiving surface of the photodetector 35.

  The light source unit 51 includes a first emission unit that emits a light beam having a first wavelength of about 405 nm to the first optical disc 11, and a second wavelength of about 655 nm to the second optical disc 12. And a third emission part for emitting a light beam with a third wavelength of about 785 nm to the third optical disc 13.

  Next, the optical path of the light beam emitted from the light source unit 51 in the optical pickup 50 will be described. First, an optical path when information is read or written on the first optical disc 11 will be described.

  The disc type discriminating unit 22 that discriminates that the type of the optical disc 2 is the first optical disc 11 emits a light beam having the first wavelength from the first emitting unit of the light source unit 51.

  As shown in FIG. 6, the light beam of the first wavelength emitted from the first emission part of the light source part 51 is made into substantially parallel light by the coupling lens 36, and the signal recording surface of the optical disc by the aberration correction means 37. The aberration generated in step 1 is corrected and made incident on the first beam splitter 38.

  Since the optical path of the light beam having the first wavelength after entering the first beam splitter 38 is the same as that of the optical pickup 3 described above, the description thereof will be omitted.

  Next, an optical path when information is read from or written to the second optical disk 12 will be described.

  The disc type discriminating unit 22 that discriminates that the type of the optical disc 2 is the second optical disc 12 emits a light beam having the second wavelength from the second emitting unit of the light source unit 51.

  As shown in FIG. 6, the light beam of the second wavelength emitted from the second emission part of the light source part 51 is made into substantially parallel light by the coupling lens 36, and the signal recording surface of the optical disk by the aberration correction means 37. The aberration generated in step 1 is corrected and made incident on the first beam splitter 38.

  Since the optical path of the light beam having the second wavelength after entering the first beam splitter 38 is the same as that of the optical pickup 3 described above, the description thereof will be omitted.

  Next, an optical path when information is read from or written to the third optical disc 13 will be described.

  The disc type discriminating unit 22 that discriminates that the type of the optical disc 3 is the third optical disc 13 emits the light beam having the third wavelength from the third emitting unit of the light source unit 51.

  As shown in FIG. 6, the divergence angle of the light beam of the third wavelength emitted from the third emission part of the light source part 51 is converted by the coupling lens 36, and the signal recording surface of the optical disk by the aberration correction unit 37. The aberration generated in step 1 is corrected and made incident on the first beam splitter 38.

  Since the optical path of the light beam having the third wavelength after entering the first beam splitter 38 is the same as that of the optical pickup 3 described above, the description thereof will be omitted.

  In the optical pickup 50 to which the present invention is applied, when light beams having first to third wavelengths having different wavelengths are incident on the common diffractive optical element 34 by the common diffractive optical element 34, The light beam is transmitted through the inside of the shielding part 34d, the light beam of the second wavelength is diffracted and shielded by the first diffraction region 34a, and the region inside the first diffraction region 34a is transmitted, and the third A light beam having a wavelength can be diffracted and shielded by the first and second diffraction regions 34a and 34b, and transmitted through the region inside the second diffraction region 34b. Aperture restriction can be performed with an aperture amount corresponding to the wavelength of the light beam. Therefore, the optical pickup 3 can obtain different opening amounts depending on the format, and can read and write a good signal with respect to an optical disc having a different format, and can eliminate complicated alignment and the like. Thus, an increase in weight, an increase in the number of parts, and an increase in cost can be prevented.

  In the optical pickup 50, as in the case of the optical pickup 3 described above, the regions other than the first and second diffraction regions 34a and 34b of the diffractive optical element 34a are not particularly regions having a diffraction function. However, the present invention is not limited to this, and other diffraction functions may be provided.

  Since the optical disk apparatus 1 to which the present invention is applied includes the optical pickups 3 and 50 described above, the common diffractive optical element 34 can limit the aperture of light beams having different wavelengths passing therethrough according to the wavelength, Different apertures can be obtained depending on the format, and it is possible to read and write good signals on optical disks of different formats, realizing compatibility with multiple types of optical disks, simplifying the configuration, and simplifying the assembly process And miniaturization of equipment.

  Next, as a further modification of the present invention, an optical pickup capable of adjusting the light amount of a light beam having a specific wavelength will be described below. In the following description, portions common to the optical pickup 3 described above are denoted by common reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 7, an optical pickup 60 to which the present invention is applied includes a first light source unit 31 having a first emitting unit that emits a light beam having a first wavelength, and a light beam having a second wavelength. A second light source part 32 having a second emission part for emitting and a third emission part for emitting a light beam of a third wavelength; and a light beam emitted from the first to third emission parts. An objective lens 33 that condenses on the signal recording surface of the optical disc 2, a first diffractive region 64a that is arranged on the optical path of the light beam having the first to third wavelengths, and a first diffractive region that has a ring shape. A diffractive optical element 64 having a second diffractive region 64b provided inside 64a and a photodetector 35 for detecting return light reflected by the signal recording surface.

  Further, the optical pickup 60 is disposed between the first to third emission units and the diffractive optical element 64, and is a coupling lens that converts the divergence angle of the light beam emitted from the first to third emission units. 36, an aberration correction unit 37 that is provided between the coupling lens 36 and the diffractive optical element 64 and corrects the aberration based on the signal detected by the photodetector 35, the aberration correction unit 37, and the diffractive optical element 64. Between the first beam splitter 38 and the first and second optical path branching means for branching the optical path of the return light reflected by the signal recording surface from the optical path of the forward path light and guiding it to the photodetector 35. The light path of the light beam emitted from the first light source section 31 and the optical path of the light beam emitted from the second light source section 32 are provided between the light source sections 31 and 32 and the coupling lens 36. Optical path synthesis As a stage, a second beam splitter 39, an aperture filter 40 provided on the incident side of the objective lens 33 for limiting the aperture of the light beam incident on the objective lens 33, the first beam splitter 38 and the photodetector 35 are provided. And an optical element 41 for focusing the light beam on the light receiving surface of the photodetector 35.

  As shown in FIGS. 7 and 8, the diffractive optical element 64 is disposed between the first beam splitter 38 and the objective lens 33, and has an annular zone-shaped first surface on one surface thereof. Of the first diffraction region 64a and the second diffraction region 64b provided on the inner side of the first diffraction region 64a, the first and second diffraction regions 64a, And a third diffractive region 64c formed to be approximately the same size as the total size of 64b.

  The first diffraction region 64a transmits the light beams having the first and third wavelengths and diffracts the light beam having the second wavelength. Here, the first diffraction region 64a diffracts a part of the light beam having the second wavelength, so that the light beam passing through the first diffraction region 64a is incident on the objective lens 33. That is, the light quantity of the light beam that passes through the first diffraction region 64a and enters the signal recording surface of the optical disc is adjusted. That is, the first diffraction region 64a functions as a light amount adjusting unit that adjusts the light amount on the signal recording surface of the passing light beam.

  Further, the first diffraction region 64a diffracts a part of the light beam having the second wavelength and transmits the rest, thereby changing the light quantity at the outer peripheral edge of the spot collected on the optical disk to the light quantity at the center part. The outer diameter of the spot can be enlarged by reducing the diameter. That is, the first diffraction region 64a also functions as a spot diameter adjusting unit that adjusts the spot diameter on the signal recording surface of the passing light beam.

  The second diffraction region 64b transmits the light beams having the first and second wavelengths and diffracts the light beam having the third wavelength. Here, the second diffraction region 64b diffracts the light beam having the third wavelength, thereby appropriately condensing the light having the third wavelength via the objective lens 33 on the signal recording surface of the optical disc. Adjust the beam divergence angle. That is, the second diffraction region 64b functions as first divergence angle adjusting means for adjusting the divergence angle of a light beam having a predetermined wavelength that passes therethrough.

  The third diffraction region 64c transmits the light beams having the first and third wavelengths and diffracts the light beam having the second wavelength. Here, the third diffraction region 64c diffracts the light beam having the second wavelength, and thereby collects the light having the second wavelength so as to be appropriately condensed on the signal recording surface of the optical disc via the objective lens 33. Adjust the beam divergence angle. That is, the third diffraction region 64c functions as second divergence angle adjusting means for adjusting the divergence angle of a light beam having a predetermined wavelength that passes therethrough.

  The diffractive optical element 64 having the first diffractive region 64a diffracts a part of the light beam having the second wavelength, which is one of the different wavelengths, when a light beam having a different wavelength is incident thereon, The spot diameter on the signal recording surface of the optical disk can be increased by adjusting the intensity distribution, that is, the light quantity distribution, of the light beam that passes through the first diffraction region 64a and enters the objective lens 33.

  The diffractive optical element 64 having the second and third diffractive regions 64a receives a light beam having a third wavelength, which is one of the different wavelengths, when a light beam having a different wavelength is incident thereon. By diffracting in the diffraction region 64b, the divergence angle of the light beam of the third wavelength is converted so as to be appropriately condensed on the signal recording surface of the optical disc via the objective lens 33, and the other one wavelength is the first wavelength. By diffracting the light beam having the second wavelength by the third diffraction region 64c, the divergence angle of the light beam having the second wavelength is appropriately condensed on the signal recording surface of the optical disc via the objective lens 33. Can be converted.

  Therefore, the diffractive optical element 64 can be incident on the objective lens 33 at an optimal divergence angle with respect to light beams of three different wavelengths, realizing compatibility of optical disks having different formats, and having a predetermined wavelength. By adjusting the light amount distribution in the spot on the signal recording surface of the light beam, it is possible to selectively enlarge the spot diameter.

  The diffractive optical element 64 is conventionally provided by, for example, near the middle of adjacent tracks, which has been difficult to realize unless the optical diameter is added and a complicated configuration is provided by selectively enlarging the spot diameter. This special signal can be read from an optical disc having a special signal such as an encryption signal, and the configuration of the optical pickup can be simplified and reduced in size.

  In the diffractive optical element 64, the first diffractive region 64a realizes the enlargement of the spot diameter by the hologram shape, but is configured to change the spot shape by appropriately changing the hologram shape. You may do it. When the first diffraction region is provided as a spot shape deforming means for deforming such a spot shape, the spot diameter of the light beam is deformed in the direction in which the special signal is formed, for example, in the radial direction of the optical disc. This special signal can be read out.

  Next, the configuration of the first to third diffraction regions 64a, 64b, and 64c will be described. A hologram is formed in the first to third diffraction regions 64a, 64b, and 64c, and the shape of the hologram is a stepped shape having a predetermined number of steps. That is, the first to third diffraction regions 64a, 64b, and 64c are similar to the first and second diffraction regions 34a and 34b described with reference to FIGS. 4 (a) and 4 (b). A stepped hologram having a predetermined number of steps n (n is an integer greater than or equal to 2) is formed, and a stepped hologram having first to (n-1) th steps is formed. A stepped hologram having first to nth diffraction surfaces is formed. In the first to third diffraction regions 64a, 64b, and 64c, the number of steps may be the same or different.

  The first to third diffraction regions 64a, 64b, and 64c are refracted with respect to the substrate in the same manner as the first and second diffraction regions 34a and 34b described with reference to FIG. You may form by joining the joining member from which the frequency characteristic of a rate differs. When such a bonding member is bonded, the number of steps formed on the diffractive surface and the refractive index characteristics of the base material and the bonding member are changed to further transmit light corresponding to the wavelength. And the degree of freedom of diffraction can be increased.

  In the first diffraction region 64a, for example, the refractive index of the substrate is 1.5 with respect to the light beam having the second wavelength (655 nm), and the total groove depth, which is the sum of the depths of the respective step portions, is set. When the thickness is about 1.55 μm, 99% or more of the light beams of the first and third wavelengths are transmitted, and the light beam of the second wavelength is partially diffracted and about 70% is transmitted. Can do.

  In the optical pickup 60, an aperture filter 40 is provided on the incident side of the objective lens 33 as aperture limiting means for limiting aperture of the light beam incident on the objective lens 33. The aperture filter 40 has a wavelength dependency in which the aperture diameter changes depending on the wavelength, and is 0.85 for the first wavelength, 0.60 for the second wavelength, 0.45 with respect to the wavelength of.

  Next, the optical path of the light beam emitted from the first and second light source units 31 and 32 in the optical pickup 60 will be described. First, an optical path when information is read or written on the first optical disc 11 will be described.

  The disc type discriminating unit 22 that discriminates that the type of the optical disc 2 is the first optical disc 11 emits a light beam having the first wavelength from the first emitting unit of the first light source unit 31.

  As shown in FIGS. 7 and 8, the light beam of the first wavelength emitted from the first emission part of the first light source part 31 is transmitted through the mirror surface 39a of the second beam splitter 39, and The coupling lens 36 makes the light substantially parallel, and the aberration correction means 37 corrects the aberration generated on the signal recording surface of the optical disk and enters the first beam splitter 38.

  The light beam having the first wavelength incident on the first beam splitter 38 passes through the mirror surface 38 a and enters the diffractive optical element 64.

  The light beam having the first wavelength incident on the diffractive optical element 64 includes a first diffraction region 64a and a second diffraction region 64b provided on the incident side, and a third diffraction region provided on the output side. 64c is transmitted, the numerical aperture is set to 0.85 by the aperture filter 40, and the light is appropriately condensed on the signal recording surface 11a of the first optical disc 11 by the objective lens 33.

  The light beam collected on the first optical disk 11 is reflected by the signal recording surface 11a, passes through the objective lens 33 and the diffractive optical element 64, is reflected by the first beam splitter 38, and is on the photodetector 35 side. Is emitted. The light beam having the first wavelength branched by the first beam splitter 38 is focused on the light receiving surface of the photodetector 35 by the optical element 41 and detected.

  Next, an optical path when information is read from or written to the second optical disk 12 will be described.

  The disc type discriminating unit 22 that discriminates that the type of the optical disc 2 is the second optical disc 12 emits a light beam having the second wavelength from the second emitting unit of the second light source unit 32.

  The light beam of the second wavelength emitted from the second emission part of the second light source part 32 is reflected by the mirror surface 39a of the second beam splitter 39, as shown in FIGS. The coupling lens 36 makes the light substantially parallel, and the aberration correction means 37 corrects the aberration generated on the signal recording surface of the optical disk and enters the first beam splitter 38.

  The light beam having the second wavelength incident on the first beam splitter 38 passes through the mirror surface 38 a and is incident on the diffractive optical element 64.

  The light beam of the second wavelength incident on the diffractive optical element 64 is adjusted in light amount to the first diffractive region 64a provided on the incident side, transmitted through the second diffractive region 64b, and provided on the output side. The angle of divergence is adjusted by the third diffraction region 64c, and the light is emitted to the objective lens 33 side. Here, the first diffraction region 64a diffracts a part of the light beam having the second wavelength that passes therethrough and transmits the remaining light beam of about 70% to adjust the light amount.

  The light beam of the second wavelength emitted from the diffractive optical element 64 has a numerical aperture of 0.6 by the aperture filter 40, and is appropriately condensed by the objective lens 33 on the signal recording surface 12a of the second optical disc 12. Is done. Here, the light beam of the second wavelength collected on the signal recording surface 12a is diffracted by a part of the portion that has passed through the first diffraction region 64a, so that the light amount is adjusted and the spot diameter is adjusted. Is enlarged.

  Since the optical path on the return path side of the light beam reflected by the signal recording surface 12a of the second optical disc 12 is the same optical path as the light beam having the first wavelength described above, description thereof will be omitted.

  Next, an optical path when information is read from or written to the third optical disc 13 will be described.

  The disc type discriminating unit 22 that discriminates that the type of the optical disc 3 is the third optical disc 13 emits a light beam having the third wavelength from the third emitting unit of the second light source unit 32.

  The light beam of the third wavelength emitted from the third emission part of the second light source part 32 is reflected by the mirror surface 39a of the second beam splitter 39 as shown in FIGS. The coupling lens 36 makes the light substantially parallel, and the aberration correction means 37 corrects the aberration generated on the signal recording surface of the optical disk and enters the first beam splitter 38.

  The light beam having the third wavelength incident on the first beam splitter 38 passes through the mirror surface 38a and enters the diffractive optical element 64.

  The light beam of the third wavelength incident on the diffractive optical element 64 is transmitted through the first diffractive region 64a provided on the incident side, and the divergence angle is adjusted by the second diffractive region 64b, and on the output side. The light passes through the provided third diffraction region 64c and is emitted to the objective lens 33 side. Here, the light beam of the third wavelength that has passed through the first diffraction region 64a is shielded when the aperture is limited by the aperture filter 40 described later, and thus does not affect the subsequent steps.

  The light beam of the third wavelength emitted from the diffractive optical element 64 has a numerical aperture of 0.45 by the aperture filter 40, and is appropriately condensed by the objective lens 33 on the signal recording surface 13a of the third optical disc 13. Is done.

  Since the optical path on the return path side of the light beam reflected by the signal recording surface 13a of the third optical disc 13 is the same optical path as the light beam having the first wavelength described above, description thereof will be omitted.

  The optical pickup 60 to which the present invention is applied can be made incident on the objective lens 33 by the common diffractive optical element 64 at the optimum divergence angles with respect to the light beams having the first to third wavelengths having different wavelengths. Therefore, it is possible to realize compatibility between optical discs having different formats. In addition, the optical pickup 60 to which the present invention is applied makes it possible to adjust the amount of light by diffracting a part of the portion corresponding to the spot outer peripheral portion of the light beam of a predetermined wavelength, and to enlarge the spot diameter. .

  In the optical pickup 60, the first to third emission units are arranged in the first light source unit 31 or the second light source unit 32. However, the present invention is not limited to this. Similar to the light source unit 51 in the optical pickup 50, the first to third emission units are arranged in one light source unit, and common to three different wavelength light beams emitted from the light source unit. The diffractive optical element may be made incident on the objective lens at an optimum divergence angle to realize compatibility between different formats.

  The optical pickup 60 to which the present invention is applied selectively reads a special signal such as an encryption signal provided near the middle of adjacent tracks by selectively expanding the spot diameter of a light beam having a predetermined wavelength. It is possible to control the optimum spot diameter for the format without adding optical components.

  The optical disc apparatus 1 including the optical pickup 60 described above is provided, for example, near the middle of adjacent tracks by selectively enlarging the spot diameter of a light beam having a predetermined wavelength by a common diffractive optical element 64. It is possible to read special signals such as encrypted signals, and to control the optimal spot diameter for the format without adding optical components. In addition to realizing compatibility with a plurality of types of optical disks by enabling reading and writing, the configuration is simplified, the assembly process is simplified, and the apparatus is downsized.

It is a block circuit diagram which shows the structure of the recording / reproducing apparatus to which this invention is applied. It is a block diagram explaining the optical system of the optical pick-up to which this invention is applied. It is sectional drawing explaining the structure of the diffractive optical element which comprises the optical pick-up to which this invention is applied. FIG. 2 illustrates a configuration of a hologram of a diffractive optical element that constitutes an optical pickup to which the present invention is applied, in which (a) is a sectional view of a hologram with n steps, and (b) represents the number of steps. FIG. 5C is a cross-sectional view of a hologram in a state where a bonding member is bonded to a diffraction region. It is a figure which shows the intensity | strength of the diffracted light of each diffraction order of the light beam of each wavelength which passes along with the change of phase depth in the hologram part of the 1st and 2nd diffraction area of a diffractive optical element. It is a block diagram explaining the other example of the optical system of the optical pick-up to which this invention is applied. It is a block diagram explaining the further another example of the optical system of the optical pick-up to which this invention is applied. It is sectional drawing explaining the structure of the diffractive optical element which comprises the optical pick-up shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus, 2 Optical disk, 3 Optical pick-up, 4 Spindle motor, 5 Feed motor, 9 Servo control circuit, 22 Disk type discrimination | determination part, 31 1st light source part, 32 2nd light source part, 33 Objective lens, 34 Diffraction Optical element, 35 photodetector, 36 coupling lens, 37 aberration correcting means, 38 first beam splitter, 39 second beam splitter, 41 optical element

Claims (8)

A first emission part for emitting a light beam of a first wavelength;
A second emission part for emitting a light beam of a second wavelength;
A third emission part for emitting a light beam of a third wavelength;
An objective lens for condensing the light beam emitted from the first to third emission portions on the signal recording surface of the optical disc;
A diffractive optical element disposed on the optical path of the light beam having the first to third wavelengths and having a ring-shaped first diffractive region and a second diffractive region provided inside the first diffractive region. When,
A photodetector for detecting the return light reflected by the optical disc,
The first diffraction region transmits the light beam having the first wavelength and diffracts the light beams having the second and third wavelengths,
The second diffraction region is an optical pickup that transmits the light beams of the first and second wavelengths and diffracts the light beam of the third wavelength. The first wavelength is about 405 nm;
The second wavelength is about 655 nm;
2. The optical pickup according to claim 1, wherein the third wavelength is about 785 nm.   The optical pickup according to claim 1, wherein the second diffraction region is formed in a ring shape.   The optical pickup according to claim 1, wherein the objective lens and the diffractive optical element are arranged on a unit.   2. The optical pickup according to claim 1, wherein holograms are formed in the first and second diffraction regions of the diffractive optical element.   2. The optical pickup according to claim 1, wherein the first and second diffraction regions are provided on one surface of the diffractive optical element. The first diffraction region is provided on one surface of the diffractive optical element,
2. The optical pickup according to claim 1, wherein the second diffraction region is provided on the other surface of the diffractive optical element. In an optical disc apparatus comprising: an optical pickup that records and / or reproduces information with respect to a plurality of different types of optical discs; and a disc rotation driving unit that rotationally drives the optical disc.
The optical pickup includes a first emission unit that emits a light beam having a first wavelength;
A second emission part for emitting a light beam of a second wavelength;
A third emission part for emitting a light beam of a third wavelength;
An objective lens for condensing the light beam emitted from the first to third emission portions on the signal recording surface of the optical disc;
A diffractive optical element disposed on the optical path of the light beam having the first to third wavelengths and having a ring-shaped first diffractive region and a second diffractive region provided inside the first diffractive region. When,
A photodetector for detecting the return light reflected by the optical disc,
The first diffraction region transmits the light beam having the first wavelength and diffracts the light beams having the second and third wavelengths,
The second diffraction region is an optical disc apparatus that transmits a light beam having a first wavelength and a second wavelength and diffracts a light beam having a third wavelength.

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