JP2006053953A - Optical head and recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust easily a position of a light spot formed on a disk and to perform simultaneously the compensation of the divergent light distribution of a semiconductor laser. <P>SOLUTION: This apparatus is provided with a semiconductor laser 31 in which a plurality of light sources emitting a plurality of laser beams are provided, an objective lens 48 converging each laser beam emitted from the semiconductor laser 31 and irradiating it to an optical disk 2, a light receiving element 51 receiving return light from the optical disk 2 irradiated with each laser beam by the objective lens 48, a beam splitter guiding each laser beam emitted from the semiconductor laser 31 to the objective lens 48, while guiding the return light from the optical disk 2 to the light receiving element 51, an anamorphic prism 46 arranged at an optical path from the beam splitter to the objective lens 48 and forming a beam shape of each laser beam, and a rotation actuator 66 rotating the anamorphic prism 46 in accordance with the light quantity of the return light received by the light receiving element 51. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical head and a recording apparatus for recording an information signal by irradiating an optical recording medium with a plurality of laser beams.

  Conventionally, as an optical recording medium, a reproduction-only optical disk called CD (Compact Disc), a write-once optical disk called CD-R (Compact Disc-Recordable), and the like have been put into practical use. These optical discs are widely used because they are excellent in mass productivity, can be manufactured at low cost, and can reproduce information or record information relatively stably.

  By the way, in such an optical disk, the recording capacity has been increased in recent years. Under such circumstances, the DVD (Digital Versatile Disc / DVD) that can dramatically increase the recording capacity while maintaining the same outer diameter as a CD and can store data for one movie with the same image quality as the current television broadcast. Digital Video Disc) has been developed and put to practical use. In this DVD, in order to increase the recording density and increase the recording capacity, information is recorded and reproduced using a laser having a shorter wavelength than that of a laser used for a CD or the like.

  An optical recording / reproducing apparatus that uses an optical disc as a recording medium can record and reproduce information on the DVD, and can record and reproduce information on a CD and CD-R. An optical head having a so-called interchangeable optical head has been developed. In an optical head compatible with both CDs, CD-Rs, and DVDs, an optical system for CDs and CD-Rs and an optical for DVDs are used in order to reduce the size of the entire head and reduce manufacturing costs. It is desirable to make the system as common as possible.

  In addition, in such an optical head, a configuration that is compatible with a blue laser compatible optical disc has been proposed in recent years. In this blue laser compatible optical disk, by using blue laser light having a wavelength of 405 nm, a minute spot can be formed on the information recording surface, and as a result, the recording density can be improved.

  In such an optical recording / reproducing apparatus for recording / reproducing an optical disc corresponding to a CD, a DVD, and a blue laser, the reflectance change generated on the optical disc by the irradiated laser light is read by the objective lens in a non-contact manner. Assuming that the wavelength of the laser light applied to the optical disk is λ and the numerical aperture of the objective lens is NA, the size of the light spot formed on the optical disk is given by λ / NA, and the resolution is also proportional to this value. It will be.

  Incidentally, the recording / reproducing speed (transfer rate) of the information signal on the optical disc is proportional to the number of rotations of the disc. However, when the number of light spots irradiated on the optical disc is increased, the transfer rate is increased. It is also possible. For example, in Non-Patent Document 1, as shown in FIG. 11, eight light beams emitted from a multi-beam LD (Laser Diode) 81 are converted into parallel light by a lens 82, and then an image rotation prism (Dove prism) 83. Is shown, the propagation direction of which is changed by 90 ° by the reflection mirror 84, and the light is condensed on the optical disc 87 by the objective lens 85. In this disk device 8, it is possible to simultaneously reproduce information of a plurality of tracks by detecting the return light from the optical disk 87 in each light beam by an independent photodetector.

  In Non-Patent Document 2, as shown in FIG. 12, the light beam emitted from the semiconductor laser 91 is divided into a plurality of beams by a diffraction grating 92, which is passed through a beam splitter 93 and is collimated by a collimator lens 94. A disk device 9 for condensing light onto the optical disk 98 by the objective lens 95 has been proposed. In this disk device 9, it is possible to simultaneously reproduce information of a plurality of tracks by detecting the return light of the light beam irradiated on the disk 98 by the detector 96 having the independent detection unit 96a corresponding to each. Become.

  In these disc devices, the light spot formed on the disc cannot be located at the center of the track due to subtle changes in the track interval due to the difference in the inserted optical disc, the radial position on the disc, the optical system misalignment, etc. There is. For this reason, in the disk device 8, by rotating the image rotating prism 83, the array angle is changed so that each of the plurality of spots formed on the disk is positioned at the track center. Also in the disk device 9, the same adjustment can be performed by rotating the diffraction grating 92.

R.Arai et al: Approved easeability Study on High Data Transfer Rate of 300Mbit / s with 8-Beam Laser Diode Array, Ning pn.J.Appl.Phys., Vol.32 (1993) pp.5411-5416 J. Dovic, et al: Fever ulti-track DVD-ROM, pregnancy igest of Optical Data Storage Topical Meeting 2001, Santa Fe, New Mexico, April 2001

  In the conventional disk device described above, the position of the light spot formed on the disk can be adjusted by rotating the image rotating prism 83 and the diffraction grating 92, but laser beam beam shaping cannot be performed. . In particular, since the divergent light distribution of the semiconductor laser that emits the laser light described above is elliptical, it is necessary to mount an optical component for forming this into a circular shape. There is a problem that the burden is imposed, and as a result, the cost cannot be reduced.

  Accordingly, the present invention has been devised in view of the above-described problems, and the object of the present invention is to easily adjust the position of the light spot formed on the disk and to adjust the divergent light distribution of the semiconductor laser. It is an object of the present invention to provide a disk device and method capable of performing correction simultaneously.

  In order to solve the above-described problems, an optical head according to the present invention collects a light emitting unit provided with a plurality of light sources that respectively emit a plurality of laser beams and a laser beam emitted by the light emitting unit. An objective lens that emits light to irradiate the optical recording medium, a light receiving unit that receives return light from the optical recording medium irradiated with each laser beam by the objective lens, and an objective lens that receives each laser beam emitted from the light emitting unit Anamorphic which is arranged on the optical path from the light separating means to the objective lens, and shapes the beam shape of each laser light. A prism and rotation control means for rotating the anamorphic prism in accordance with the amount of return light received by the light receiving means are provided.

  In order to solve the above-described problems, a recording apparatus according to the present invention is a recording apparatus that records an information signal on an optical recording medium, and a driving unit that rotates the optical recording medium, and an optical recording that is rotationally driven by the driving unit. An optical head that irradiates the medium with laser light as an information signal and detects return light from the optical recording medium, and the optical head includes a plurality of light sources that respectively emit a plurality of laser lights. A light emitting means, an objective lens for condensing each laser light emitted by the light emitting means and irradiating the optical recording medium, and a return light from the optical recording medium irradiated with each laser light by the objective lens. A light receiving means for guiding the laser light emitted from the light emitting means to the objective lens, a light separating means for guiding the return light from the optical recording medium to the light receiving means, and an object from the light separating means to the objective lens. An anamorphic prism which is arranged on the optical path leading to the laser beam and shapes the beam shape of each laser beam, and a rotation control means which rotates the anamorphic prism according to the amount of return light received by the light receiving means Have

  In the present invention, an anamorphic prism is disposed on the optical path from the light separating means to the objective lens, and the anamorphic prism is rotated in accordance with the amount of return light from the signal recording surface of the optical recording medium. Thereby, the position of the spot of the laser beam formed on the optical recording medium can be adjusted, and at the same time, the divergent light distribution of the laser beam can be shaped into a circle. In other words, it is possible to realize spot position adjustment and beam shaping with one anamorphic prism, so that it is not necessary to mount extra optical components, but the manufacturing process can be simplified. It becomes possible to reduce the burden of labor. It is also possible to reduce the manufacturing cost.

  In particular, in the present invention, the spot position on the light receiving element changes even when the anamorphic prism is rotated by disposing the anamorphic prism on the optical path from the light separating means to the objective lens. There is also an advantage that nothing is lost.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  The present invention is applied to an optical head as shown in FIG. The optical head 1 includes a holder 43 that supports a plurality of semiconductor lasers 31, a collimator lens 44 that collimates laser light emitted from the semiconductor laser 31, and an optical path of the laser light emitted from the collimator lens 44. , A anamorphic prism 46 disposed in the optical path of the laser light transmitted through the beam splitter 45, and the laser recording light passing through the anamorphic prism 46 as the signal recording surface of the optical disc 2. The objective lens 48 that condenses on the light 2a, the condensing lens 49 that collects the return light reflected from the signal recording surface 2a of the optical disc 2, the cylinder lens 50, and the return light that has passed through the cylinder lens 50. And a light receiving element 51 for receiving light.

  In addition, the optical head 1 includes a calculator 61 that performs a predetermined calculation based on the amount of return light received by the light receiving element 51, and a first driver 62, a second driver 63, and the like connected to the calculator 61, respectively. A biaxial actuator 65 connected to the third driver 64, the first driver 62, and the second driver 63, to which the objective lens 48 is mounted, and a rotary actuator 66 to which the anamorphic prism is mounted It has.

  The optical head 1 irradiates a light beam onto a signal recording surface 2a of an optical disc 2 that is rotated by driving a spindle motor (not shown), and detects the amount of return light reflected by the signal recording surface 2a of the optical disc 2. To the calculator 61. At this time, the optical head 1 emits a light beam having an optimum wavelength for the optical disc 2 depending on the type of the optical disc 2 to be rotated.

  For example, if the optical disk 2 to be rotationally driven is a CD-R, the optical head 1 emits a light beam having a wavelength of about 780 nm. If the optical disk 2 to be rotationally driven is a DVD, the light having a wavelength of about 650 nm is emitted. When the optical disk 2 that emits a beam and is driven to rotate is compatible with a blue laser, a light beam having a wavelength of about 405 nm is emitted.

  The computing unit 61 generates a focus error signal FE based on the detected amount of return light and transmits it to the first driver 62, and also generates a tracking error signal TE, which is output to the second driver. 63.

  The first driver 62 controls the biaxial actuator based on the focus error signal FE transmitted from the computing unit 61 to move the objective lens 48 in the direction of approaching and separating from the optical disc 2.

  The second driver 63 controls the biaxial actuator based on the tracking error signal TE transmitted from the computing unit 61 to move the objective lens 48 in the biaxial direction of the optical disk 2 in the radial direction. As a result, the optical head 1 is operated so as to be positioned on a predetermined recording track of the optical disc 2.

  A semiconductor laser 31 that emits a plurality of laser beams is attached to the holder 43. The semiconductor laser 31 is a light emitting element that utilizes semiconductor recombination emission. When the optical disc 2 is a CD-R, a plurality of CDs that emit a plurality of laser beams having a wavelength of about 780 nm corresponding to the optical disc 2 are used. When an optical chip is attached and the optical disk 2 is a DVD, a DVD chip that simultaneously emits a plurality of laser beams having a wavelength of about 650 nm corresponding to the optical disk 2 is attached. Furthermore, when the optical disc 2 is compatible with a blue laser, a Blu-ray chip that simultaneously emits a plurality of laser beams having a wavelength of about 405 nm corresponding to the optical disc 2 is attached.

  Incidentally, the holder 43 is not limited to the case where the same type of semiconductor laser 31 that emits laser beams of the same wavelength is attached, but the semiconductor lasers are attached so that the emitted wavelengths are different from each other. May be. In such a case, for example, a CD chip is attached on one side and a DVD chip is attached on the other side, so that the configuration corresponds to a plurality of different types of optical disks 2.

  These semiconductor lasers 31 are arranged in a row on the holder 43 at positions close to each other, and the interval between the chips is on the order of microns. For this reason, each laser beam emitted from each semiconductor laser 31 is irradiated onto the optical disc 2 through substantially the same optical path. These semiconductor lasers 31 may be housed in the same package. As a result, in the present invention in which laser beams having different wavelengths are emitted corresponding to a plurality of different types of optical discs 2, it is possible to further reduce the size and reduce the manufacturing cost.

  The beam splitter 45 transmits the laser light emitted from the semiconductor laser 31 and converted into parallel light by the collimator lens 44 and guides it to the optical disc 2, and reflects the return light reflected and returned from the optical disc 2 to receive the light. Lead to 51. The laser light that has passed through the beam splitter 45 passes through the anamorphic prism 46.

  Incidentally, when the laser beam emitted from the semiconductor laser 31 has polarization, the beam splitter 45 is configured as a polarization beam splitter, and the laser beam transmitted therethrough is passed through a quarter wavelength plate (not shown). It is possible to prevent the return light reflected from the optical disk 2 from returning to the semiconductor laser 31 and generating noise.

  The anamorphic prism 46 is configured to convert the beam shape of the laser light transmitted through the beam splitter 45 from, for example, an elliptical shape to a perfect circular shape.

  The spot shape converted by the anamorphic prism 46 is not limited to a perfect circle shape and may be any shape.

  As shown in FIG. 2, the laser light emitted from the semiconductor laser 31 has a beam emission angle that expands in a direction perpendicular to the line B on the bonding surface of the semiconductor laser 31, and in a direction parallel to the line B. The beam radiation angle is small. The anamorphic prism 46 can be formed into a perfect circle by shaping the laser light emitted from the semiconductor laser so that the respective beam radiation angles are equal. The laser beam formed by the anamorphic prism 46 is emitted to the objective lens 48.

  Further, incident light as parallel light incident on the anamorphic prism 46 is emitted from the anamorphic prism 46 as the parallel light, and a signal obtained by providing the anamorphic prism 46 is a signal. It becomes possible to suppress the change of the spot shape on the recording surface 2a.

  Incidentally, the anamorphic prism 46 may be configured by combining triangular prisms so that the incident light from the beam splitter 45 and the outgoing light to the optical disc 2 are parallel to each other. As a result of combining the triangular prisms as shown in FIGS. 3A and 3B, for example, the width l of the component parallel to the line B of the laser light can be expanded to reach the width β. . In such a case, the width of the component perpendicular to the line B of the laser beam is maintained as it is without being enlarged, and as a result, the beam shape can be controlled to a perfect circle shape.

  Further, in this anamorphic prism 46, as shown in FIG. 3C, a cylindrical lens may be combined to expand the beam shape.

  The objective lens 48 is disposed in the optical path of the laser light that has passed through the anamorphic prism 46, and has a function of condensing the laser light and irradiating it on the signal recording surface 2a of the optical disc 2. The objective lens 48 is supported by a biaxial actuator 65 so as to be movable in two axial directions, ie, a direction approaching and separating from the optical disc 2 and a radial direction of the optical disc 2. The objective lens 48 is moved and operated by the biaxial actuator 65 based on the focus error signal FE and the tracking error signal TE generated by the return light from the optical disc 2 to realize focusing control and tracking control. become.

  Each laser beam condensed on the signal recording surface 2a of the optical disc 2 is reflected by the signal recording surface 2a to become return light, and this return light passes again through the objective lens 48 and the anamorphic prism 46, and further The beam splitter 45 is reflected.

  The light receiving element 51 reflects the beam splitter 45, receives the return light collected by the condensing lens 49 and the cylinder lens 50, and performs photoelectric conversion. This photoelectrically converted signal is sent to the calculator 61 and contributes to the generation of the focus error signal FE and the tracking error signal TE.

  As described above, in the optical head 1 to which the present invention is applied, a plurality of laser beams are emitted and irradiated on the respective tracks of the optical disc 2, whereby recording processing can be simultaneously performed on the plurality of tracks. Each return light obtained as a result of reflecting the plurality of laser beams to the optical disc 2 is independently detected by the light receiving element 51 to simultaneously detect signals from a plurality of tracks and generate the signals FE and TE. Is possible.

  In the optical head 1, for example, as shown in FIG. 4A, when two laser beams follow each track of the optical disc 2, a first spot is formed on each track based on the laser beams. A second spot is formed, and the return lights R1 and R2 from the first spot and the second spot are received in a beam shape as shown in FIG. 4B in each detector block of the light receiving element 51. Will be.

  Here, when the track error signal TE is obtained based on the push-pull method, TE = A + B− (C + D) is obtained from outputs A, B, C, and D obtained as a result of photoelectric conversion by the detector block. Here, the tracking error signal TE1 related to the return light R1 can be obtained by calculating TE1 = A1 + B1- (C1 + D1), and the tracking error signal TE2 related to the return light R2 is calculated from TE2 = A2 + B2- (C2 + D2). Can be obtained. The tracking error signals TE1 and TE2 obtained at the end are added to generate a tracking error signal TE (= TE1 + TE2) for actually performing the tracking servo control via the biaxial actuator 65.

  Similarly, when the focus error signal FE is obtained, FE = A + C− (B + D) is obtained from outputs A, B, C, and D obtained as a result of photoelectric conversion by the detector block. Here, the focus error signal FE1 related to the return light R1 can be obtained by calculating FE1 = A1 + C1- (B1 + D1), and the focus error signal FE2 related to the return light R2 is calculated as FE2 = A2 + C2- (B2 + D2). Can be obtained. The focus error signals FE1 and FE2 obtained at the end are added to generate a focus error signal FE (= FE1 + FE2) for actually performing tracking servo control via the biaxial actuator 65.

  It should be noted that it is possible to identify a deviation from each track position in the first spot and the second spot from the obtained tracking error signals TE1 and TE2. For example, when the interval between the first spot and the second spot is deviated from an integral multiple of the track, one of the spots is at the track center, and the other one spot is deviated from the track center. Therefore, the tracking error signals TE1 and TE2 are not equal.

  Therefore, by obtaining the difference between the tracking error signals TE 1 and TE 2, it is possible to identify the relative positional deviation of the spot with respect to the track position of the optical disc 2. Hereinafter, the difference value between the tracking error signals TE1 and TE2 is defined as RE (= TE1−TE2), which is defined as a prism rotation control signal.

  In the optical head 1 to which the present invention is applied, this prism rotation control signal RE is generated and transmitted to the third driver 64. The third driver 64 receives the analog rotation based on the received prism rotation control signal RE. By rotating the morphic prism 46, the positions of the first spot and the second spot with respect to the track position on the optical disc 2 are adjusted.

  At this time, the rotation of the anamorphic prism 46 is not limited to the case based on the prism rotation control signal RE composed of the difference value between the tracking error signals TE1 and TE2 described above, and is returned to the light receiving element 51. Any rotation amount may be defined as long as it is based on the amount of light.

  Incidentally, in order to rotate the anamorphic prism 46, for example, a rotary actuator 66 as shown in FIG. 5 is used.

  The rotary actuator 66 includes a leaf spring 71 to which the anamorphic prism 46 is fixed, a coil 72 provided on the leaf spring 71, and a magnet 73 disposed to face the coil 72. .

  The leaf spring 71 is disposed so as to be rotatable about an axis Q provided on one end side. The third driver 64 applies a voltage to the coil 72 based on the prism rotation control signal RE received from the computing unit 61, thereby applying an attractive force between the coil 72 and the magnet 73, thereby causing the leaf spring 71. Is freely rotated in the W direction in the figure. As a result, the anamorphic prism 46 disposed on the leaf spring 71 can be rotated in the rotation direction K centering on the emission direction of the laser light to the objective lens 48.

  Incidentally, this rotary actuator 66 may be replaced with other electromagnetic means. In such a case, for example, the above-described operation may be realized by switching the position of the coil 72 provided on the leaf spring 71 and the mounting position of the magnet 73.

  FIG. 6 shows the relationship between the incident angle of the laser light incident on the anamorphic prism 46 from the semiconductor laser 31 and the emission angle of the laser light emitted from the anamorphic prism 46. In the example shown in FIG. 6, the magnification of the laser beam by the anamorphic prism 46 is shown as β (> 1) in the y-axis direction and 1 in the x-axis direction.

  When laser light is incident on the anamorphic prism 46 controlled to have the magnification β, the incident angle to the anamorphic prism 46 is θ in the x and y directions. , 7, the optical path is changed so that the output angle is θ in the x direction and θ / β in the y direction.

  FIG. 8 shows the relationship of the emission angle with respect to the incident angle of the laser beam to the anamorphic prism 46 on the xy plane. As shown in FIG. 8, when a laser beam tilted in the y-axis direction is incident, the magnification factor in the y-axis direction is β, and this is compressed in the y-axis direction to be tilted in the x-axis direction. Light can be emitted.

  Incidentally, this θ can also be defined as the rotation angle of the anamorphic prism 46 with respect to the incident laser light. As shown in FIG. 9, when the rotation angle θ (= incident angle) of the anamorphic prism 46 is small with respect to the laser light, the emission angle of the emitted laser light is as shown in FIG. A rotation of about (1-β) θ occurs. That is, when the anamorphic prism 46 rotates (−θ) with respect to the incident laser light, the emitted light rotates (β−1) θ. For this reason, when controlling the emission angle of the laser light emitted using the anamorphic prism 46, the anamorphic prism 46 is rotated in the direction opposite to the incident direction of the laser light to the anamorphic prism. This can be realized.

  Actually, the third driver 64 identifies the amount of spot deviation with respect to the track from the prism rotation control signal RE described above, and determines the amount of rotation of the anamorphic prism 46 according to the identified amount of deviation. Further, when adjusting the emission angle of the laser beam emitted from the anamorphic prism 46 so that the spot is at a desired position, the laser beam is incident in a direction that is reversed with respect to the incident direction of the laser beam incident on the anamorphic prism 46. Control is performed to rotate the anamorphic prism 46.

  The third driver 64 is not limited to the case where the anamorphic prism 46 is rotated in a direction reverse to the incident direction of the laser light incident on the anamorphic prism 46, and the incident laser is not limited. What is necessary is just to rotate this to a predetermined direction with respect to the incident direction of light.

  Incidentally, since the incident angle of the laser beam to the anamorphic prism 46 can be identified in advance at the time of manufacture, it is previously identified at the time of manufacture which direction is reversed according to the identified incident angle. It is also possible to include this in the command signal from the third driver 64 to the rotary actuator 66.

  As described above, in the optical head 1 to which the present invention is applied, the anamorphic prism 46 is disposed on the optical path from the beam splitter 45 to the objective lens 48, and the return light from the signal recording surface 2 a of the optical disc 2. The anamorphic prism 46 is rotated according to the amount of light. Thereby, the position of the spot of the laser beam formed on the disk 2 can be adjusted, and the divergent light distribution of the laser beam can be formed into a circle together with this. That is, the adjustment of the spot position and the beam shaping can be realized by one anamorphic prism 46, so that it is not necessary to mount extra optical components, and the manufacturing process can be simplified. It becomes possible to reduce the burden of labor. It is also possible to reduce the manufacturing cost.

  In particular, in the optical head 1 to which the present invention is applied, even when the anamorphic prism 46 is rotated by disposing the anamorphic prism 46 on the optical path from the beam splitter 45 to the objective lens 48, There is also an advantage that the spot position on the light receiving element 51 is not changed.

  In the optical head 1 to which the present invention is applied, information may be recorded on and reproduced from the signal recording surface 2a of the optical disc 2 by near-field light.

  In such a case, evanescent light is exuded from the reflection boundary surface of the laser light incident on the end surface of the objective lens 48 at an angle greater than the critical angle. At this time, when the end surface of the objective lens 48 is in the near field (near field) with respect to the signal recording surface 2a of the optical disc 2, the evanescent light exuded from the objective lens 48 is irradiated onto the signal recording surface 2a. It becomes possible to make it.

  Next, the near field will be described. Generally, in the near field, when the distance (gap) from the end face of the objective lens 48 to the signal recording surface 2a of the optical disc 2 is d, d ≦ λ / 2 depending on the wavelength λ of the laser light incident on the objective lens 48. The area defined as is the near field. That is, the gap d defined by the distance between the signal recording surface 2 a of the optical disc 2 and the end surface of the objective lens 48 satisfies d ≦ λ / 2, and evanescent light is transmitted from the end surface of the objective lens 48 to the signal recording surface of the optical disc 2. The state that oozes out to 2a is called the near field state, and the state where the gap d satisfies d> λ / 2 and no evanescent light oozes out on the signal recording surface 2a is called the far field state.

  In the near-field state, part of the laser light incident on the end surface of the objective lens 48 at an angle greater than the critical angle is, as described above, as evanescent light on the end surface of the objective lens 48, that is, the reflection boundary surface. To the signal recording surface 2a. The amount of return light in the near-field state decreases depending on the distance between the end surface of the objective lens 48 and the disk 2.

  Even in the near-field state, the return light quantity is received by the light receiving element 51 and photoelectrically converted to generate a gap error signal GE. Based on this, feedback servo control is performed via the biaxial actuator 65. The gap can be controlled to be constant. At the same time, the spot position on the optical disk 2 by the near-field light can be adjusted by rotating the anamorphic prism 46 based on the prism rotation control signal RE generated by photoelectric conversion by the light receiving element 51. Become.

  Thus, in the optical head 1 to which the present invention is applied, focus control is performed by moving the biaxial actuator 65 in the direction of approaching and separating based on the amount of return light received by one light receiving element 51. In addition, since the spot position of the near-field light can be adjusted by rotating the anamorphic prism 46, the near-field where the position of the objective lens with respect to the light spot and the spot position on the signal recording surface 2a are particularly strictly required. This is advantageous when performing a recording process using light.

  In the optical head 1 to which the present invention is applied, an example in which a signal can be recorded based on two modes of the near field and the far field has been described. However, the present invention is not limited to such a case. A signal may be recorded by near-field light based on a field-only mode.

  The present invention is not limited to the optical head 1 described above, and may be applied to a recording apparatus 3 as shown in FIG. In the recording apparatus 3, the same components and members as those of the optical head 1 shown in FIG. 1 described above are denoted by the same reference numerals and description thereof is omitted here.

  The recording device 3 irradiates a rotation driving unit 9 that rotates the optical disc 2 and a laser beam as an information signal to the optical disc 2 that is rotationally driven by the rotation driving unit 9 and returns light from the optical disc 2. And an optical head 1 for detecting.

  Also in this recording apparatus 3, when an information signal is recorded on the optical disk 2, an anamorphic prism 46 is disposed on the optical path from the beam splitter 45 to the objective lens 48, and the signal recording surface of the optical disk 2 is recorded. An optical head 1 capable of rotating the anamorphic prism 46 in accordance with the amount of return light from 2a is provided. Thereby, at the time of recording an information signal, the position of the spot of the laser beam formed on the disk 2 can be adjusted, and the divergent light distribution of the laser beam can be formed into a circle together with this. That is, the adjustment of the spot position and the beam shaping can be realized by one anamorphic prism 46, so that it is not necessary to mount extra optical components, and the manufacturing process can be simplified. It becomes possible to reduce the burden of labor. It is also possible to reduce the manufacturing cost.

  Of course, the recording apparatus 3 to which the present invention is applied may adopt a configuration in which the information signal recorded on the optical disc 2 can be reproduced.

It is a figure for demonstrating the structure of the optical head to which this invention is applied. It is a figure for demonstrating about conversion of the beam shape of the laser beam by an anamorphic prism. It is a figure for demonstrating about the expansion method of the beam shape by an anamorphic prism. It is a figure for demonstrating about the case where two laser beams are made to track each track | truck of an optical disk. It is a figure for demonstrating about the detail of a rotary actuator. It is a figure shown about the relationship between the incident angle of the laser beam to an anamorphic prism, and an output angle. It is another figure shown about the relationship between the incident angle of the laser beam to an anamorphic prism, and an output angle. It is the figure which represented on the xy plane the relationship of the outgoing angle with respect to the incident angle to the anamorphic prism of a laser beam. It is a figure for demonstrating the emission angle of a laser beam in case rotation angle (theta) (= incident angle) of an anamorphic prism is small. It is a figure for demonstrating about the structure of the recording device to which this invention is applied. It is a figure shown about the structure of the conventional disk apparatus. It is a figure shown about the other structure in the conventional disc apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Optical head, 2 Optical disk, 31 Semiconductor laser, 43 Holder, 44 Collimator lens, 45 Beam splitter, 46 Anamorphic prism, 48 Objective lens, 49 Condensing lens, 50 Cylinder lens, 51 Light receiving element, 61 Calculator, 62 First driver, 63 Second driver, 64 Third driver, 65 Biaxial actuator, 66 Rotary actuator

Claims (12)

A light emitting means provided with a plurality of light sources that respectively emit a plurality of laser beams;
An objective lens for condensing each laser beam emitted by the light emitting means and irradiating the optical recording medium;
A light receiving means for receiving return light from the optical recording medium irradiated with the laser beams by the objective lens;
A light separating unit that guides each laser beam emitted by the light emitting unit to the objective lens and guides return light from the optical recording medium to the light receiving unit;
An anamorphic prism which is disposed on an optical path from the light separating means to the objective lens, and shapes the beam shape of each laser beam;
An optical head comprising rotation control means for rotating the anamorphic prism in accordance with the amount of return light received by the light receiving means. The rotation control unit generates a tracking signal for tracking adjustment with respect to the optical recording medium based on the amount of return light received by the light receiving unit, and further generates each of the generated laser beams. The optical head according to claim 1, wherein the anamorphic prism is rotated in accordance with a difference between tracking signals. 2. The optical head according to claim 1, wherein the rotation control unit rotates the anamorphic prism in a direction reverse to a direction in which the laser beams are incident on the anamorphic prism. 3. 2. The optical head according to claim 1, wherein the anamorphic prism forms a beam shape of each of the laser beams and converts the laser beam into parallel light. The optical head according to claim 1, wherein at least one light source in the light emitting unit emits blue laser light. 2. The optical head according to claim 1, wherein the objective lens exudes the condensed laser light as near-field light when arranged in a near-field with respect to the information recording surface of the optical recording medium. In a recording apparatus for recording an information signal on an optical recording medium,
Driving means for rotationally driving the optical recording medium;
An optical head for irradiating the optical recording medium rotated by the driving means with the laser beam as the information signal and detecting return light from the optical recording medium;
The optical head is
A light emitting means provided with a plurality of light sources that respectively emit a plurality of laser beams;
An objective lens for condensing each laser beam emitted by the light emitting means and irradiating the optical recording medium;
A light receiving means for receiving return light from the optical recording medium irradiated with the laser beams by the objective lens;
A light separating unit that guides each laser beam emitted by the light emitting unit to the objective lens and guides return light from the optical recording medium to the light receiving unit;
An anamorphic prism which is disposed on an optical path from the light separating means to the objective lens, and shapes the beam shape of each laser beam;
A recording apparatus comprising rotation control means for rotating the anamorphic prism in accordance with the amount of return light received by the light receiving means. The rotation control unit generates a tracking signal for tracking adjustment with respect to the optical recording medium based on the amount of return light received by the light receiving unit, and further generates each of the generated laser beams. The recording apparatus according to claim 7, wherein the anamorphic prism is rotated in accordance with a difference between tracking signals. The recording apparatus according to claim 7, wherein the rotation control unit rotates the anamorphic prism in a direction reverse to a direction in which the laser beams are incident on the anamorphic prism. The recording apparatus according to claim 7, wherein the anamorphic prism forms a beam shape of each of the laser beams and converts the laser beam into parallel light. The recording apparatus according to claim 7, wherein at least one light source in the light emitting unit emits blue laser light. The recording apparatus according to claim 7, wherein the objective lens exudes the condensed laser light as near-field light when the objective lens is disposed in a near-field with respect to the information recording surface of the optical recording medium.

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