JP3831321B2 - Optical pickup device and optical disk device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup device and an optical disc device, and more specifically, an optical pickup device that irradiates light onto a recording surface of a plurality of types of information recording media and receives reflected light from the recording surface, and the optical pickup device. The present invention relates to an optical disc device provided.
[0002]
[Prior art]
In an optical disc apparatus, an information recording medium such as an optical disc is used. Information is recorded and erased by irradiating a recording surface on which a spiral or concentric track is formed, and reflected light from the recording surface. Information is reproduced based on this. The optical disc apparatus is provided with an optical pickup device as an apparatus for irradiating a recording surface of an information recording medium with a laser beam to form a light spot and receiving reflected light from the recording surface.
[0003]
Usually, the optical pickup device includes an objective lens, guides the light beam emitted from the light source to the recording surface of the information recording medium, and guides the return light beam reflected by the recording surface to a predetermined light receiving position, and the light receiving position. And the like. From this light receiving element, not only the reproduction information of the data recorded on the recording surface but also a signal including information (servo control information) necessary for controlling the position of the optical pickup device itself and the objective lens is output.
[0004]
In recent years, a DVD (Digital Versatile Disc) whose recording capacity is dramatically larger than a CD (Compact Disc) has been generalized as an information recording medium. A laser beam having a wavelength of 785 nm is used to perform recording and reproduction on a CD, and a laser beam having a wavelength of 660 nm is used to perform recording and reproduction on a DVD. The optical disc apparatus of DVD and the optical disc apparatus for DVD are used independently as peripheral devices of information equipment such as personal computers.
[0005]
Thereafter, with the reduction in size and weight of the information equipment, the need for an optical disc apparatus capable of accessing both CDs and DVDs has increased. In this case, in order to support both DVD and CD, the optical pickup device uses a semiconductor laser (hereinafter also referred to as “DVD light source”) that emits a laser beam having a wavelength of 660 nm and a laser beam that has a wavelength of 785 nm as a light source. And a laser system (hereinafter also referred to as “CD light source”), and an optical system for detecting each laser beam is required. However, if the optical system for 660 nm and the optical system for 785 nm are individually arranged, there is a disadvantage that the optical pickup device becomes large. Hereinafter, an optical pickup device including light sources having two different wavelengths is also referred to as a “two-wavelength optical pickup device”.
[0006]
Therefore, for example, in Japanese Patent No. 3026279, an LD module in which two laser elements that output laser beams having different wavelengths are integrated is provided, and a light receiving element is shared for the return light flux of each wavelength. A laser module for a recording / reproducing apparatus is disclosed. In the optical pickup device using this laser module, it is possible to share an optical system and reduce the number of optical parts, and the simplification of parts assembly, cost reduction, and miniaturization are promoted.
[0007]
In general, a light beam emitted from a semiconductor laser used as a light source (hereinafter also referred to as “emitted light beam”) is applied to an active layer (heterojunction surface) AL of a semiconductor laser LD as shown in FIG. It is a divergent light having an elliptical intensity distribution with the direction perpendicular to the major axis direction. The ratio of the luminous flux that is taken into the objective lens and collected on the recording surface of the information recording medium (hereinafter also referred to as “captured luminous flux”) out of the outgoing luminous flux is relative to the maximum intensity in the entrance pupil of the objective lens. It is indicated by the ratio of the intensity at the pupil edge and is called the rim intensity. For example, FIG. 15 shows an example of the captured light flux when the rim intensity is 50%. The ratio of the light amount on the recording surface to the light amount of the emitted light beam, that is, the light utilization efficiency is substantially inversely proportional to the rim intensity, as shown in FIG. 16 as an example. That is, if the rim strength is designed to be high, the light use efficiency is lowered, and if the design is made to increase the light use efficiency, the rim strength is low.
[0008]
[Problems to be solved by the invention]
Usually, the rim intensity with respect to the light beam emitted from the CD light source is designed to be lower than the rim intensity with respect to the light beam emitted from the DVD light source. This is because the recording density of a DVD is high, so that the spot diameter of the light spot needs to be accurately controlled, while on the other hand, it is important to improve the light utilization efficiency of a CD.
[0009]
However, in the optical pickup device using the laser module disclosed in Japanese Patent No. 3026279, the rim intensity with respect to the light beam emitted from the CD light source is equal to the rim intensity with respect to the light beam emitted from the DVD light source. However, there is an inconvenience that it is difficult to cope with an increase in the access speed because the light use efficiency in the CD is lowered. On the other hand, when the optical system is optimized for a CD, there is a disadvantage that it is difficult to accurately control the spot diameter of a light spot on a DVD.
[0010]
The present invention has been made under such circumstances. The first object of the present invention is to support a plurality of types of information recording media without causing an increase in size and cost, and is optimal for each information recording medium. An object of the present invention is to provide an optical pickup device capable of forming a light spot.
[0011]
A second object of the present invention is to provide an optical disc apparatus that can handle a plurality of types of information recording media and can stably perform access at a high speed.
[0012]
[Means for Solving the Problems]
The invention according to claim 1 is an optical pickup device that irradiates light onto recording surfaces of a plurality of types of information recording media and receives reflected light from the recording surfaces, and is provided for each of the plurality of information recording media. A plurality of light sources that selectively emit light beams having different wavelengths; an objective lens that focuses each light beam on a recording surface of a corresponding information recording medium; and An optical system that guides the return light beam reflected by the recording surface to a predetermined light receiving position; and an optical system that includes the optical element that makes each light beam directed to the objective lens substantially parallel light; A photodetector for receiving light; and The plurality of light sources emit a first light source that emits a light beam having a first wavelength as a first light beam, and a second light source that emits a light beam having a second wavelength longer than the first wavelength. The first light flux and the second light flux are divergent light having an elliptical light intensity distribution in a cross section in the maximum intensity emission direction, and the optical system is configured to emit light of the first light flux. The first adjustment optical element that expands the divergence angle on the plane including the minor axis of the ellipse so that the intensity distribution is substantially circular, and the light intensity distribution of the second light flux is substantially circular. A second adjusting optical element that reduces a divergence angle on a plane including the major axis of the ellipse. This is an optical pickup device.
[0013]
According to this, each light beam alternatively emitted from a plurality of light sources is made into substantially parallel light by the optical element, and then condensed on the recording surface of the corresponding information recording medium via the objective lens. Usually, the shorter the wavelength of the light beam, the higher the recording density of the corresponding information recording medium, and it is necessary to narrow down the light spot in the objective lens. For this purpose, it is desirable that the light intensity be as uniform as possible. On the other hand, when the recording density of the information recording medium is not so high, it is important to increase the access speed. For this reason, it is desirable that most of the light beam emitted from the light source is condensed by the objective lens. Here, since each light beam incident on the optical element has a larger divergence angle as the wavelength is shorter, the light intensity of the light beam collected by the objective lens is almost uniform and the wavelength is longer when the light beam has a short wavelength. Most of the light flux is collected by the objective lens. That is, the rim intensity of the light beam taken into the objective lens can be brought close to the ideal value at that wavelength. Moreover, since the objective lens is made common to each light beam emitted from a plurality of light sources, it is possible to promote downsizing and cost reduction of the optical pickup device, and simplify the assembly process and the adjustment process. It becomes possible. Accordingly, it is possible to deal with a plurality of types of information recording media without causing an increase in size and cost, and it is possible to form an optimum light spot on each information recording medium.
[0014]
In this case, like the optical pickup device according to claim 2, The first adjustment optical element and the second adjustment optical element have wavelength selectivity. Can be.
[0015]
3. Each optical pickup device according to claim 1 and 2. In the optical pickup device according to claim 3, The first adjustment optical element and the second adjustment optical element are laminated and integrated with each other. Can be.
[0016]
In each of the optical pickup devices according to claims 1 to 3, like the optical pickup device according to claim 4, The optical system includes a branching optical element that is arranged between the plurality of light sources and the optical element and branches the return light beam from a common optical path of an outward path and a return path, and includes the first adjusting optical element and the second adjusting optical element. These adjustment optical elements are all disposed between the branch optical element and the optical element. Can be.
[0024]
Claim 5 The invention according to claim 1 is an optical disc apparatus that performs at least reproduction of information recording, reproduction, and erasure with respect to a plurality of types of information recording media. 4 An optical disc device comprising: the optical pickup device according to claim 1; and a processing device that performs at least reproduction of recording, reproduction, and erasing of the information using an output signal from the optical pickup device. .
[0025]
According to this, claims 1 to 4 Since the optical pickup device according to any one of the above items is provided, an optimal light spot can be formed on each information recording medium with respect to a plurality of types of information recording media. It is possible to deal with an information recording medium, and stable access at high speed can be achieved.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0027]
FIG. 1 shows a schematic configuration of an optical disc device according to an embodiment including an optical pickup device according to the present invention.
[0028]
The optical disk apparatus 20 shown in FIG. 1 includes a spindle motor 22, an optical pickup apparatus 23, a laser control circuit 24, an encoder 25, a driver 27, a reproduction signal processing circuit 28, and the like for rotationally driving an optical disk 15 as an information recording medium. A servo controller 33, a buffer RAM 34, a buffer manager 37, an interface 38, a ROM 39, a CPU 40, a RAM 41, and the like are provided. Note that the arrows in FIG. 1 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block. In the present embodiment, it is assumed that the optical disk device 20 is compatible with two types of information recording media, CD and DVD.
[0029]
The optical pickup device 23 is a device for irradiating the recording surface on which the spiral or concentric tracks of the optical disk 15 are formed with laser light and receiving reflected light from the recording surface. The configuration of the optical pickup device 23 will be described in detail later.
[0030]
Returning to FIG. 1, the reproduction signal processing circuit 28 converts a current signal, which is an output signal of the optical pickup device 23, into a voltage signal, and based on the voltage signal, a wobble signal, an RF signal, and a servo signal (focus error signal, Track error signal). Then, the reproduction signal processing circuit 28 extracts address information, a synchronization signal, and the like from the wobble signal. The address information extracted here is output to the CPU 40, and the synchronization signal is output to the encoder 25. Further, the reproduction signal processing circuit 28 performs error correction processing or the like on the RF signal and then stores it in the buffer RAM 34 via the buffer manager 37. The servo signal is output from the reproduction signal processing circuit 28 to the servo controller 33.
[0031]
The servo controller 33 generates a control signal for controlling the optical pickup device 23 based on the servo signal and outputs it to the driver 27.
[0032]
The buffer manager 37 manages input / output of data to / from the buffer RAM 34, and notifies the CPU 40 when the accumulated data amount reaches a predetermined value.
[0033]
The driver 27 controls the optical pickup device 23 and the spindle motor 22 based on a control signal from the servo controller 33 and an instruction from the CPU 40.
[0034]
Based on an instruction from the CPU 40, the encoder 25 takes out data stored in the buffer RAM 34 via a buffer manager 37, adds an error correction code, and creates a write signal to the optical disc 15. Then, the encoder 25 outputs a write signal to the laser control circuit 24 in synchronization with the synchronization signal from the reproduction signal processing circuit 28 based on an instruction from the CPU 40.
[0035]
The laser control circuit 24 controls the laser light output from the optical pickup device 23 based on the write signal from the encoder 25. The laser control circuit 24 controls one of two light sources of an optical pickup device 23 described later based on an instruction from the CPU 40.
[0036]
The interface 38 is a bidirectional communication interface with a host (for example, a personal computer) and conforms to standard interfaces such as ATAPI (AT Attachment Packet Interface) and SCSI (Small Computer System Interface).
[0037]
The ROM 39 stores a program written in a code readable by the CPU 40. The CPU 40 controls the operation of each unit according to a program stored in the ROM 39 and temporarily stores data necessary for the control in the RAM 41.
[0038]
Next, the configuration and the like of the optical pickup device 23 will be described with reference to FIGS. 2 (A) and 2 (B).
[0039]
As shown in FIG. 2A, the optical pickup device 23 alternatively emits a laser beam having a wavelength of 660 nm and a laser beam having a wavelength of 785 nm, and also returns a return beam from the recording surface of the optical disk 15. Light receiving / emitting module LM, first divergence angle adjusting element M1, second divergence angle adjusting element M2, coupling lens 52, objective lens 60 and drive system (focusing actuator, tracking actuator and seek motor) (all shown) (Omitted).
[0040]
As shown in FIG. 2B as an example, the light receiving / emitting module LM includes a first semiconductor laser 53 that emits laser light having a wavelength of 660 nm, and a second semiconductor laser that emits laser light having a wavelength of 785 nm. 54, etc., a hologram 61 as a branching optical element for branching the return light beam from the recording surface of the optical disc 15, a light receiving element 59 as a photodetector for receiving the return light beam branched by the hologram 61, etc. The light-receiving part RL provided with this. The first semiconductor laser 53 is selected when the optical disk 15 is a DVD, and the second semiconductor laser 54 is selected when the optical disk 15 is a CD. In the present embodiment, the maximum intensity emission direction of the light beam emitted from each semiconductor laser is defined as the −Z direction.
[0041]
In the present embodiment, the first semiconductor laser 53 and the second semiconductor laser 54 are arranged so that their active layers AL1 and AL2 are parallel to the XZ plane, as shown in FIG. 3 as an example. And Therefore, the light beam emitted from each semiconductor laser is divergent light having an elliptical light intensity distribution with the Y-axis direction as the major axis direction. That is, the light beam emitted from the first semiconductor laser 53 (hereinafter also referred to as “first emitted light beam” for convenience) is shown in FIG. 4A and FIG. Angle of divergence θ _1Y And angle of divergence θ in the XZ plane _1Z Is not the same as _1Y > Θ _1Z Are in a relationship. Similarly, a light beam emitted from the second semiconductor laser 54 (hereinafter, also referred to as “second emitted light beam” for convenience) is represented by YZ as shown in FIGS. 5A and 5B as an example. In-plane divergence angle (θ _2Y And the divergence angle in the XZ plane (θ _2Z Is not the same as _2Y > Θ _2Z Are in a relationship.
[0042]
Returning to FIG. 2B, the hologram 61 fixed to the exit window is arranged on the −Z side of each semiconductor laser. As in the prior art, the light receiver 59 includes a plurality of light receiving elements that output signals optimal for detecting a wobble signal, a reproduction signal, a servo signal, and the like.
[0043]
Returning to FIG. 2A, the first divergence angle adjusting element M <b> 1 is disposed on the −Z side of the light emitting / receiving module LM. The first divergence angle adjusting element M1 has wavelength selectivity and selectively adjusts the divergence angle of the first outgoing light beam.
[0044]
The second divergence angle adjusting element M2 is disposed on the −Z side of the first divergence angle adjusting element M1. The second divergence angle adjusting element M2 has wavelength selectivity and selectively adjusts the divergence angle of the second outgoing light beam. As the first divergence angle adjusting element M1 and the second divergence angle adjusting element M2, for example, an optical element using a glass material made of a material having a different refractive index depending on the wavelength, such as a polymer liquid crystal, is used.
[0045]
Here, assuming that the focal length of the coupling lens 52 is fcl, the beam diameter φdvd of the first outgoing light beam transmitted through the coupling lens 52 is obtained by the following equation (1) as shown in FIG. Can do. Here, θ1 is a divergence angle of the first outgoing light beam incident on the coupling lens 52.
[0046]
φdvd = 2 × fcl × sin (θ1 / 2) (1)
[0047]
Further, the beam diameter φcd of the second outgoing light beam transmitted through the coupling lens 52 can be obtained by the following equation (2). Here, θ2 is a divergence angle of the second outgoing light beam incident on the coupling lens 52.
[0048]
φcd = 2 × fcl × sin (θ2 / 2) (2)
[0049]
As an example, as shown in FIG. 7, there is a correlation between the divergence angle of the light beam incident on the coupling lens 52 and the rim intensity, and the rim intensity increases as the divergence angle increases. Therefore, in order to design the rim strength in the case of DVD higher than the rim strength in the case of CD, in other words, in order to design the light utilization efficiency in the case of CD higher than that in the case of DVD, the following equation (3) is satisfied. There is a need.
[0050]
φdvd> φcd (3)
[0051]
That is, it is necessary to satisfy the following expression (4).
[0052]
θ1> θ2 (4)
[0053]
Here, for example, in order to set the rim strength in the case of DVD to 30% (light utilization efficiency = about 45%) and the rim strength in the case of CD to 15% (light utilization efficiency = about 50%) If the focal length fcl of the lens 52 is 11 mm, θ1 is 11 degrees and θ2 is 7.7 degrees.
[0054]
In the present embodiment, as an example, as shown in FIG. 8A, in the case where the first divergence angle adjusting element M1 is not provided, the light flux Bdvd taken into the objective lens 60 among the first emitted light flux is It is assumed that the rim strength is approximately 30% in the Y-axis direction, but the rim strength is <30% in the X-axis direction. Further, as shown in FIG. 8B, in the case where the second divergence angle adjusting element M2 is not provided, the light beam Bcd taken into the objective lens 60 among the second emitted light beam is substantially rim in the X-axis direction. The strength = 15%, but the rim strength> 15% in the Y-axis direction.
[0055]
Therefore, the first divergence angle adjusting element M1 has a divergence angle θ in the XZ plane of the first outgoing light beam. _1Z (Θ _1Y / Θ _1Z ) Times (> 1). As a result, as shown in FIG. 9A, the divergence angle in the XZ plane of the first outgoing light beam transmitted through the first divergence angle adjusting element M1 is the divergence angle θ. _1Z The divergence angle θ in the YZ plane _1Y Is almost equal to The light flux taken into the objective lens 60 has a rim intensity of approximately 30% in the X-axis direction.
[0056]
Further, the second divergence angle adjusting element M2 is configured such that the divergence angle θ in the YZ plane of the second emitted light beam is _2Y (Θ _2Z / Θ _2Y ) Times (<1). Accordingly, as shown in FIG. 9B, the divergence angle in the YZ plane of the second emitted light beam transmitted through the second divergence angle adjusting element M2 is the divergence angle θ. _2Y And the divergence angle θ in the XZ plane _2Z Is almost equal to The light flux taken into the objective lens 60 has a rim intensity of approximately 15% in the Y-axis direction.
[0057]
The coupling lens 52 is disposed on the −Z side of the second divergence angle adjusting element M2, and each of the first outgoing light beam and the second outgoing light beam is substantially parallel light. The objective lens 60 is disposed on the −Z side of the coupling lens 52. The objective lens 60 condenses the light beam that has passed through the coupling lens 52 and forms a light spot on the recording surface of the optical disk 15.
[0058]
The operation of the optical pickup device 23 configured as described above will be described. First, the case where the optical disk 15 is a DVD will be described.
[0059]
The light beam emitted from the first semiconductor laser 53 enters the hologram 61. The luminous flux transmitted through the hologram 61 is expanded in divergence angle in the XZ plane by the first divergence angle adjusting element M1. This light beam passes through the second divergence angle adjusting element M2 as it is, becomes substantially parallel light by the coupling lens 52, and then is condensed as a minute spot on the recording surface of the optical disk 15 via the objective lens 60.
[0060]
The reflected light reflected by the recording surface of the optical disk 15 is converted into substantially parallel light again by the objective lens 60 as a return light beam. The return light beam passes through the collimating lens 52 and then enters the hologram 61 via the second divergence angle adjusting element M2 and the first divergence angle adjusting element M1. The returned light beam diffracted by the hologram 61 is received by the light receiver 59. Each light receiving element constituting the light receiver 59 outputs a current signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0061]
Next, the case where the optical disk 15 is a CD will be described. The light beam emitted from the second semiconductor laser 54 enters the hologram 61. The light beam that has passed through the hologram 61 passes through the first divergence angle adjusting element M1 as it is and enters the second divergence angle adjusting element M2. The light beam is reduced in divergence angle on the YZ plane by the second divergence angle adjusting element M2, and becomes substantially parallel light by the coupling lens 52, and then becomes a minute spot on the recording surface of the optical disk 15 via the objective lens 60. Focused.
[0062]
The reflected light reflected by the recording surface of the optical disk 15 is converted into substantially parallel light again by the objective lens 60 as a return light beam. The return light beam passes through the collimating lens 52 and then enters the hologram 61 via the second divergence angle adjusting element M2 and the first divergence angle adjusting element M1. The returned light beam diffracted by the hologram 61 is received by the light receiver 59. Each light receiving element constituting the light receiver 59 outputs a current signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0063]
Whether the optical disk 15 is a CD or a DVD can be determined from the intensity of reflected light from the recording surface. Usually, this determination is performed when the optical disk 15 is inserted into a predetermined position of the optical disk apparatus 20, that is, at the time of loading. It is also possible to determine the type of the optical disk 15 based on TOC (Table Of Contents) information, PMA (Program Memory Area) information, a wobble signal, and the like recorded in advance on the optical disk 15. Then, the determination result is notified to the laser control circuit 24, and the laser control circuit 24 selects either the first semiconductor laser 53 or the second semiconductor laser 54.
[0064]
Next, a processing operation when data is recorded on the optical disk 15 using the optical disk device 20 described above will be briefly described. It is assumed that the selection of the semiconductor laser has already been performed as described above.
[0065]
When the CPU 40 receives a recording request command from the host, it outputs a control signal for controlling the rotation of the spindle motor 22 to the driver 27 based on the recording speed, and a reproduction signal indicating that the recording request command has been received from the host. The processing circuit 28 is notified. In addition, the CPU 40 stores data received from the host in the buffer RAM 34 via the buffer manager 37.
[0066]
When the rotation of the optical disk 15 reaches a predetermined linear velocity, the reproduction signal processing circuit 28 detects a track error signal and a focus error signal based on the output signal of the light receiver 59 and outputs it to the servo controller 33. The servo controller 33 drives the tracking actuator and the focusing actuator of the optical pickup device 23 via the driver 27 based on the track error signal and the focus error signal from the reproduction signal processing circuit 28. That is, track deviation and focus deviation are corrected.
[0067]
The reproduction signal processing circuit 28 acquires address information based on the output signal of the light receiver 59 and notifies the CPU 40 of the address information. Based on the address information, the CPU 40 outputs a control signal for controlling the seek motor of the optical pickup device 23 to the driver 27 so that the optical pickup device 23 is positioned at the designated write start point.
[0068]
When the CPU 40 receives a notification from the buffer manager 37 that the amount of data accumulated in the buffer RAM 34 has exceeded a predetermined value, it instructs the encoder 25 to create a write signal. If the CPU 40 determines that the position of the optical pickup device 23 is the writing start point based on the address information, the CPU 40 notifies the encoder 25. Then, the encoder 25 records the write signal on the optical disc 15 via the laser control circuit 24 and the optical pickup device 23.
[0069]
Next, a processing operation when reproducing data recorded on the optical disc 15 using the optical disc apparatus 20 described above will be briefly described. It is assumed that the selection of the semiconductor laser has already been performed as described above.
[0070]
When the CPU 40 receives a reproduction request command from the host, it outputs a control signal for controlling the rotation of the spindle motor 22 to the driver 27 based on the reproduction speed, and also indicates that the reproduction request command has been received from the host. The processing circuit 28 is notified. When the rotation of the optical disk 15 reaches a predetermined linear velocity, tracking control and focus control of the objective lens 60 are performed as in the case of the recording process. Further, the reproduction signal processing circuit 28 detects the address information and notifies it to the CPU 40 as in the case of the recording process.
[0071]
Based on the address information, the CPU 40 outputs to the driver 27 a control signal for controlling the seek motor so that the optical pickup device 23 is positioned at the designated reading start point. When the CPU 40 determines that the position of the optical pickup device 23 is the reading start point based on the address information, the CPU 40 notifies the reproduction signal processing circuit 28.
[0072]
The reproduction signal processing circuit 28 detects the RF signal based on the output signal of the optical pickup device 23, performs error correction processing, etc., and then stores it in the buffer RAM 34. The buffer manager 37 transfers the reproduction data stored in the buffer RAM 34 to the host via the interface 38 when the reproduction data is prepared as sector data.
[0073]
Until the recording process and the reproduction process are completed, the reproduction signal processing circuit 28 detects the focus error signal and the track error signal based on the output signal from the optical pickup device 23 as described above, and the servo controller 33 and the driver. 27, the focus shift and the track shift are corrected at any time.
[0074]
As is clear from the above description, in the optical disc apparatus according to the present embodiment, the processing apparatus is realized by the reproduction signal processing circuit 28, the CPU 40, and the program executed by the CPU 40. However, it goes without saying that the present invention is not limited to this. That is, the above embodiment is merely an example, and at least a part of each component realized by processing according to the program by the CPU 40 may be configured by hardware, or all the components are configured by hardware. It's also good.
[0075]
As described above, according to the optical pickup device of this embodiment, the divergence angle θ in the XZ plane of the light beam emitted from the first semiconductor laser 53 using the first divergence angle adjusting element M1. _1Z (Θ _1Y / Θ _1Z ) Since the magnification is increased (> 1), the luminous flux taken into the objective lens 60 out of the luminous flux emitted from the first semiconductor laser 53 has a rim intensity of approximately 30% in the X-axis direction. Therefore, it is possible to form a light spot optimal for DVD on the recording surface.
[0076]
Further, according to the present embodiment, the divergence angle θ in the YZ plane of the light beam emitted from the second semiconductor laser 54 using the second divergence angle adjusting element M2. _2Y (Θ _2Z / Θ _2Y ) Since the magnification is reduced (<1), the luminous flux taken into the objective lens 60 out of the luminous flux emitted from the second semiconductor laser 54 is approximately rim intensity = 15% in the Y-axis direction. Therefore, most of the light beam emitted from the second semiconductor laser 54 is taken into the objective lens 60, and the light utilization efficiency can be improved. This makes it possible to form a light spot optimal for a CD on the recording surface, and to cope with an increase in access speed.
[0077]
That is, according to the present embodiment, since the light beam incident on the coupling lens 52 has a light intensity distribution optimal for the wavelength, the light beam taken into the objective lens 60 is the rim optimal for the wavelength. Strength can be secured. Accordingly, as a result, it is possible to cope with a plurality of types of information recording media without causing an increase in size and cost, and an optimal light spot can be formed on the recording surface for each information recording medium.
[0078]
In addition, according to the present embodiment, since the light intensity distribution of the light beam transmitted through the coupling lens 52 has a substantially circular shape, the light beam can be narrowed to an ideal beam diameter, and the light use efficiency can be reduced. Further improvement can be achieved.
[0079]
According to the present embodiment, since the first divergence angle adjusting element and the second divergence angle adjusting element are arranged between the hologram and the coupling lens, the return light beam diffracted by the hologram is the first. It is possible to prevent interference by the divergence angle adjusting element and the second divergence angle adjusting element. Therefore, the signal output from the light receiver can be stabilized.
[0080]
In addition, according to the optical disk apparatus according to the present embodiment, an optimum light spot can be formed on the recording surface for both DVD and CD, so that both DVD and CD can be handled and accurate. It is possible to stably record and reproduce information. Furthermore, the downsizing of the optical pickup device 23 can also promote the downsizing of the optical disc device itself and the reduction of power consumption. For example, when used for portable use, it can be easily carried and used for a long time. Is possible.
[0081]
In the above-described embodiment, the case where the first divergence angle adjusting element M1 and the second divergence angle adjusting element M2 are individually arranged has been described. However, the present invention is not limited to this, and the first divergence angle adjusting element M1. And the second divergence angle adjusting element M2 may be integrated. Thereby, the number of parts at the time of an assembly | attachment reduces, an assembly operation and an adjustment operation can be simplified, and it becomes possible to reduce work cost.
[0082]
Moreover, although the said embodiment demonstrated the case where the 1st divergence angle adjustment element M1 was arrange | positioned at the light source side, it is not restricted to this, The 2nd divergence angle adjustment element M2 may be arrange | positioned at the light source side. .
[0083]
Moreover, although the said embodiment demonstrated the case where the optical element (1st divergence angle adjustment element M1 and 2nd divergence angle adjustment element M2) which has wavelength selectivity was used as an optical element for changing a divergence angle. However, the present invention is not limited to this. For example, as shown in FIG. 10A, the divergence angle θ in the XZ plane _1Z (Θ _1Y / Θ _1Z ) The first lens L1 to be changed to double (> 1) is arranged on the −Z side of the first semiconductor laser 53, and for example, as shown in FIG. 10B, the divergence angle θ in the YZ plane _2Y (Θ _2Z / Θ _2Y ) The second lens L2 that is changed to double (<1) may be arranged on the −Z side of the second semiconductor laser 54. In this case, as shown in FIG. 11 as an example, each of the first lens L1 and the second lens L2 may be mounted in the light emitting / receiving module LM1.
[0084]
Further, instead of the first divergence angle adjustment element M1 and the second divergence angle adjustment element M2, as shown in FIG. 12 as an example, a third adjustment amount of the divergence angle can be controlled by an applied voltage. Alternatively, the divergence angle adjusting element M3 may be used. Here, when the optical disk is a DVD, as shown in FIG. 13A as an example, the voltage V1 is applied to the third divergence angle adjusting element M3 via the driver 27 in accordance with an instruction from the CPU 40, and XZ In-plane divergence angle θ _1Z Is (θ _1Y / Θ _1Z ) Times (> 1). On the other hand, when the optical disk is a CD, as shown in FIG. 13B as an example, the voltage V2 is applied to the third divergence angle adjusting element M3 through the driver 27 in accordance with an instruction from the CPU 40, and the YZ plane. Angle of divergence θ _2Y Is (θ _2Z / Θ _2Y ) Times (<1). As the third divergence angle adjusting element M3, a so-called liquid crystal lens (for example, see Japanese Patent Laid-Open No. 5-54414) can be used.
[0085]
Further, in the above embodiment, when the first divergence angle adjusting element M1 is not provided, the rim intensity in the Y-axis direction of the light beam taken into the objective lens 60 among the light beams emitted from the first semiconductor laser 53 is about Although the case of 30% has been described, the present invention is not limited to this. For example, the rim strength in the Y-axis direction may be smaller than 30%. However, in that case, instead of the first divergence angle adjusting element M1, the luminous flux emitted from the first semiconductor laser 53 is set so that the rim intensity is approximately 30% in the Y-axis direction and the X-axis direction. Divergence angle θ in YZ plane _1Y And the divergence angle θ in the XZ plane _1Z Thus, an optical element having an effect of increasing both of these will be used.
[0086]
Similarly, in the above embodiment, when the second divergence angle adjusting element M2 is not provided, the rim intensity in the X-axis direction of the light beam emitted from the second semiconductor laser 54 and taken into the objective lens 60 is reduced. Although the case of about 15% has been described, the present invention is not limited to this. For example, the rim strength in the X-axis direction may be greater than 15%. In this case, however, the light flux emitted from the second semiconductor laser 54 is used instead of the second divergence angle adjusting element M2 so that the rim intensity is approximately 15% in the Y-axis direction and the X-axis direction. Divergence angle θ in YZ plane _2Y And the divergence angle θ in the XZ plane _2Z Thus, an optical element having an effect of reducing both of these will be used.
[0087]
In the above embodiment, the first divergence angle adjusting element M1 that increases the divergence angle of the first outgoing light beam and the second divergence angle adjusting element M2 that decreases the divergence angle of the second outgoing light beam are used. Although the case has been described, the present invention is not limited to this. For example, when a coupling lens optimal for the first outgoing light beam is used, the first divergence angle adjusting element M1 is unnecessary. In this case, an optical element different from the second divergence angle adjusting element is used because the adjustment amount of the divergence angle becomes large for the second outgoing light beam. For example, when a coupling lens optimal for the second outgoing light beam is used, the second divergence angle adjusting element M2 is unnecessary. In this case, an optical element different from the first divergence angle adjusting element M1 is used for the first outgoing light beam because the adjustment amount of the divergence angle becomes large.
[0088]
In the above-described embodiment, the case where the divergence angle of the light beam emitted from each semiconductor laser is adjusted and enters the coupling lens has been described. However, the light beam emitted from each semiconductor laser is expressed by the above equation (4). If satisfied, the divergence angle may not be adjusted. That is, the first divergence angle adjusting element M1 and the second divergence angle adjusting element M2 may be omitted. Even in this case, the divergence angle may be adjusted when the rim strength is greatly deviated from the ideal value.
[0089]
Moreover, although the said embodiment demonstrated the case where the wavelength of the light beam radiate | emitted from a light source was two types, this invention is not limited to this.
[0090]
In addition, although the said embodiment demonstrated the case where the light source which radiate | emits a light beam with a wavelength of 660 nm and the light source which radiate | emits a light beam with a wavelength of 785 nm were provided, this invention is not limited to this. For example, instead of any one of the light sources, a light source that emits a light beam having a wavelength of 405 nm may be provided.
[0091]
Moreover, although the said embodiment demonstrated the case where a hologram was used as a branching optical element for branching a return light beam, it is not restricted to this, For example, you may use a polarization hologram. As a result, the light beam emitted from each semiconductor laser is incident on the coupling lens 52 with almost no decrease in the amount of light. Therefore, high speed access to the optical disc 15 is possible. Further, since the amount of light received by the light receiver 59 increases, the signal level and S / N ratio of the signal output from each light receiving element constituting the light receiver 59 can be improved. In this case, for example, a retardation plate for providing an optical phase difference such as a λ / 4 plate is disposed between the coupling lens 52 and the objective lens 60. A beam splitter may be used instead of the hologram.
[0092]
Moreover, although the case where the light emission part EL and the light reception part RL were integrated was demonstrated in the said embodiment, it is not restricted to this, The light emission part EL and the light reception part RL may be arrange | positioned separately, respectively.
[0093]
Moreover, although the said embodiment demonstrated the case where each semiconductor laser was arrange | positioned mutually close, this invention is not limited to this.
[0094]
In the above embodiment, the case where the shape of the light beam emitted from the light source is a divergent light having an elliptical light intensity distribution has been described. However, the shape is not limited to this, and the shape of the light beam emitted from the light source is substantially circular. A divergent light having a light intensity distribution of
[0095]
In the above embodiment, the case where the target rim strength is 30% when the optical disc is a DVD and the target rim strength is 15% when the optical disc is a CD has been described. It is not limited to this. The rim strength is desirably 10% or more and 70% or less. This is because if the rim strength exceeds 70%, it becomes difficult to secure a necessary light amount. Further, in order to obtain a rim strength of less than 10%, it is necessary to increase the numerical aperture of the coupling lens, resulting in an increase in cost.
[0096]
In the above-described embodiment, the case where the light beams emitted from the respective semiconductor lasers are incident on the coupling lens with the divergence angle adjusted so that the light intensity distribution has a substantially circular shape has been described. Is not to be done.
[0097]
Moreover, although the case where the hologram 61 was one of the components of a light receiving / emitting module was demonstrated in the said embodiment, not only this but the hologram 61 may be arrange | positioned separately from a light receiving / emitting module.
[0098]
【The invention's effect】
As described above, according to the optical pickup device of the present invention, it is possible to deal with a plurality of types of information recording media without incurring an increase in size and cost, and form an optimal light spot on each information recording medium. There is an effect that can be done.
[0099]
In addition, the optical disk apparatus according to the present invention can cope with a plurality of types of information recording media, and has an effect of being able to stably perform access at a high speed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical disc apparatus according to an embodiment of the present invention.
2A is a diagram illustrating a schematic configuration of an optical system in the optical pickup device of FIG. 1, and FIG. 2B illustrates a detailed configuration of the light receiving and emitting module of FIG. 2A. It is a figure for doing.
FIG. 3 is a diagram for explaining the shape of a light beam emitted from each semiconductor laser.
FIGS. 4A and 4B are diagrams for explaining a divergence angle of a light beam emitted from the first semiconductor laser, respectively.
FIGS. 5A and 5B are diagrams for explaining the divergence angle of the light beam emitted from the second semiconductor laser, respectively.
FIG. 6 is a diagram for explaining a relationship between a divergence angle of a light beam incident on a coupling lens and a beam diameter of the light beam transmitted through the coupling lens.
FIG. 7 is a diagram for explaining a relationship between a divergence angle of a light beam incident on a coupling lens and a rim intensity.
FIG. 8A is a diagram for explaining the rim intensity of the light beam taken into the objective lens among the light beams emitted from the first semiconductor laser when the divergence angle is not adjusted. FIG. 8B is a diagram for explaining the rim intensity of the light beam taken into the objective lens among the light beams emitted from the second semiconductor laser when the divergence angle is not adjusted.
9A is a diagram for explaining an example in which the divergence angle of the light beam emitted from the first semiconductor laser is enlarged by using the first divergence angle adjusting element; FIG. FIG. 7B is a diagram for explaining an example in which the divergence angle of the light beam emitted from the second semiconductor laser is reduced using the second divergence angle adjusting element.
FIG. 10A is a diagram for explaining an example in which the divergence angle of the light beam emitted from the first semiconductor laser is expanded using the first lens, and FIG. FIG. 6 is a diagram for explaining an example in which a divergence angle of a light beam emitted from a second semiconductor laser is reduced using a second lens.
FIG. 11 is a diagram for explaining an example in which a first lens and a second lens are mounted in a light emitting / receiving module.
FIG. 12 is a diagram for explaining an optical pickup device 23 ′ using a third divergence angle adjusting element capable of optimizing the divergence angle adjustment operation in accordance with a selected semiconductor laser.
13A is a diagram for explaining an example in which the divergence angle of the light beam emitted from the first semiconductor laser is enlarged using a third divergence angle adjusting element; FIG. FIG. 7B is a diagram for explaining an example in which the divergence angle of the light beam emitted from the second semiconductor laser is reduced using a third divergence angle adjusting element.
FIG. 14 is a diagram for explaining a positional relationship between an intensity distribution of a light beam emitted from a semiconductor laser and an active layer.
15 is a diagram for explaining rim intensity = 50% in a light beam emitted from a semiconductor laser. FIG.
FIG. 16 is a diagram for explaining a relationship between light use efficiency of a light beam emitted from a semiconductor laser and rim intensity.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 15 ... Optical disk (information recording medium), 20 ... Optical disk apparatus, 23 ... Optical pick-up apparatus, 28 ... Reproduction signal processing circuit (part of processing apparatus), 40 ... CPU (part of processing apparatus), 52 ... Coupling lens (Optical element), 53 ... first semiconductor laser (light source), 54 ... second semiconductor laser (light source), 59 ... light receiver (photodetector), 60 ... objective lens, L1 ... first lens (adjustment) Optical element, first adjusting optical element), L2 ... second lens (adjusting optical element, second adjusting optical element), M1 ... first divergence angle adjusting element (adjusting optical element, first adjusting optical element) ), M2... Second divergence angle adjustment element (adjustment optical element, second adjustment optical element), M3... Third divergence angle adjustment element (adjustment optical element).

Claims (5)

An optical pickup device that irradiates light onto a recording surface of a plurality of types of information recording media and receives reflected light from the recording surface,
A plurality of light sources provided individually corresponding to the plurality of information recording media and selectively emitting light beams having different wavelengths;
An objective lens that focuses each light beam on a recording surface of a corresponding information recording medium; and an optical element that emits each light beam emitted from the plurality of light sources and traveling toward the objective lens to substantially parallel light, An optical system for guiding the reflected return light beam to a predetermined light receiving position;
A light detector disposed at the light receiving position and receiving the return light flux;
The plurality of light sources include a first light source that emits a light beam having a first wavelength as a first light beam, and a second light beam that emits a light beam having a second wavelength longer than the first wavelength as a second light beam. Including a light source of
The first light flux and the second light flux are divergent light whose light intensity distribution in the cross section in the maximum intensity emission direction is elliptical,
The optical system includes: a first adjustment optical element that expands a divergence angle on a plane including the minor axis of the ellipse so that a light intensity distribution of the first light flux is substantially circular; and the second light flux And a second adjusting optical element for reducing a divergence angle on a plane including the major axis of the ellipse so that the light intensity distribution of the optical axis is substantially circular . The optical pickup device according to claim 1 , wherein the first adjustment optical element and the second adjustment optical element have wavelength selectivity. Wherein the first adjustment optical element and the second adjusting optical element, the optical pickup apparatus according to claim 1 or 2, characterized in that it is integrated are stacked together. The optical system includes a branching optical element that is arranged between the plurality of light sources and the optical element and branches the return light beam from a common optical path of an outward path and a return path,
Said first adjusting optical element and the second adjusting optical element is any one of claims 1 to 3, characterized in that it is arranged between both and the splitting optical element and the optical element The optical pickup device described in 1. An optical disc apparatus that performs at least reproduction of information recording, reproduction, and erasure on a plurality of types of information recording media,
An optical pickup device according to any one of claims 1 to 4 , and
An optical disc apparatus comprising: a processing device that performs at least reproduction among recording, reproduction, and erasure of the information using an output signal from the optical pickup device.

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