JP2004039181A - Optical pickup device and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device capable of accurately outputting a signal containing the information about the inclination of an information recording medium relative to an objective lens without increasing the size and costs. <P>SOLUTION: A 1st beam and a 2nd beam are individually emitted from a plurality of light sources. The 2nd beam is diffracted by a diffraction part 90 of an objective lens 60 to irradiate the recording surface of the information recording medium 15. The 2nd beam radiated onto the recording surface is reflected on the recording surface, diffracted by the diffraction part 90 again and received by a 2nd optical detector 70. A signal including information concerned with the inclination of the information recording medium 15 is outputted from the 2nd optical detector 70. Since the beam of comparatively high intensity is made incident on the diffraction part 90, the signal level and S/N ratio of an output signal from the 2nd optical detector 70 can be increased. Since the output level of the 2nd beam can be made almost constant, variation in the light receiving quantity of the 2nd optical detector can be suppressed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical pickup device and an optical disk device, and more particularly, to an optical pickup device that irradiates a recording surface of an information recording medium with light and receives light reflected from the recording surface, and an optical disk including the optical pickup device. Equipment related.
[0002]
[Prior art]
2. Description of the Related Art In an optical disk device, an information recording medium such as an optical disk is used, and information is recorded by irradiating a recording surface with a laser beam, and information is reproduced based on light reflected from the recording surface. The optical disc device includes an optical pickup device as a device for irradiating a recording surface of the information recording medium with a laser beam to form a light spot and receiving reflected light from the recording surface.
[0003]
Usually, an optical pickup device includes an objective lens, an optical system that guides a light beam emitted from a light source to a recording surface of an information recording medium, and guides a return light beam reflected by the recording surface to a predetermined light receiving position, and a light receiving position. And a light-receiving element arranged in the first position. The light receiving element outputs a signal including not only reproduction information of data recorded on the recording surface but also information (servo information) necessary for controlling the position of the optical pickup device itself and the objective lens.
[0004]
In order to accurately form a predetermined light spot at a predetermined position on the recording surface, and to accurately detect reproduction information, servo information, and the like, it is desirable that the recording surface and the optical axis of the objective lens be substantially orthogonal to each other. . However, for example, the recording surface may be inclined with respect to a plane perpendicular to the optical axis of the objective lens due to, for example, warpage or eccentricity of the information recording medium. There is an inconvenience that a signal including servo information may be deteriorated.
[0005]
Therefore, various methods and apparatuses for detecting the inclination of the information recording medium with respect to a plane perpendicular to the optical axis of the objective lens (hereinafter, abbreviated as “the inclination of the information recording medium” for convenience) have been proposed.
[0006]
For example, Japanese Patent Application Laid-Open No. H10-320804 (hereinafter, referred to as “first known example”) discloses a tilt for detecting an inclination of an information recording medium (described as “optical disk” in the first known example). An optical head device including a sensor is disclosed. The tilt sensor is disposed near the objective lens and emits a light beam for detecting the tilt of the information recording medium, and a plurality of light receiving units that receive reflected light emitted from the light emitting unit and reflected by the information recording medium. And a light receiving unit. Then, the inclination of the information recording medium is detected based on the output signal from each light receiving unit.
[0007]
Japanese Patent Application Laid-Open No. 2000-20992 (hereinafter referred to as "second known example") discloses that a tilt of an information recording medium is detected by using a part of a light beam emitted from a light source used for recording and reproduction. An optical head device is disclosed. This optical head device uses, among the light beams emitted from the light source, a light beam which has not been incident on the objective lens and has been lost in light amount, for detecting the inclination of the information recording medium.
[0008]
[Problems to be solved by the invention]
However, in the above-described first known example, since the detection systems for detecting the inclination are separately arranged, there is a problem that the optical head device is complicated and the size is increased. In addition, the number of parts increases, the cost of parts increases, and the work costs of the assembling work and the adjusting work also increase.
[0009]
Further, in the above-described second known example, since the light source for detecting the inclination is the same as the light source used for recording and reproduction, the fluctuation in the light amount of the return light beam for detecting the inclination becomes large. In such a case, there has been a disadvantage in that in order to detect the inclination with high accuracy, a device such as adjusting the gain according to the situation is required.
[0010]
The present invention has been made under such circumstances, and a first object of the present invention is to be able to output a signal including information relating to the tilt of an information recording medium with high accuracy without increasing the size and cost. An object of the present invention is to provide an optical pickup device.
[0011]
It is a second object of the present invention to provide an optical disk device capable of accurately and stably accessing an information recording medium at a high speed.
[0012]
[Means for Solving the Problems]
The invention according to claim 1 is an optical pickup device that irradiates a recording surface of an information recording medium with light and receives reflected light from the recording surface, wherein the first light beam and the second light beam are individually separated. A plurality of light sources including a light source that emits light to the light source; an objective lens disposed on an optical path of each of the light beams, and having at least one diffraction portion that diffracts the second light beam; A first photodetector for receiving the first return light beam from the recording surface of the collected first light beam, the first return light beam having passed through the objective lens; Receiving a second return light beam of the second light beam irradiated on the recording surface from the recording surface, the second return light beam being diffracted again by the diffraction unit, and including tilt information of the information recording medium. A second photodetector for outputting a signal; It is a flop arrangement.
[0013]
According to this, the first light beam emitted from the light source is condensed by the objective lens and is irradiated on the recording surface of the information recording medium. The first light beam applied to the recording surface is reflected by the recording surface, passes through the objective lens, and is received by the first photodetector as a first return light beam. The first photodetector outputs a signal including reproduction information and servo information, as in the case of the conventional optical pickup device. On the other hand, the second light beam emitted from the light source is diffracted by at least one diffractive portion of the objective lens, and irradiates the recording surface of the information recording medium. The second light beam applied to the recording surface is reflected by the recording surface, diffracted again by the diffraction unit, and received as a second return light beam by the second photodetector. Then, a signal including tilt information of the information recording medium is output from the second photodetector. Here, since a light beam having a relatively high intensity is incident on the diffraction unit, the signal level and the S / N ratio of the output signal from the second photodetector can be increased. Further, since the output level of the second light beam can be made substantially constant, the fluctuation of the amount of light received by the second photodetector can be suppressed. Therefore, it is possible to output a signal including information relating to the inclination of the information recording medium with high accuracy without increasing the size and cost.
[0014]
In this case, as in the optical pickup device according to the second aspect, the diffractive portion may be provided outside an effective area of the objective lens. In such a case, a relatively high-intensity light beam can be used for tilt detection without affecting the recording / reproducing light spot formed on the recording surface of the information recording medium.
[0015]
In each of the optical pickup devices according to the first and second aspects, as in the optical pickup device according to the third aspect, the second light flux becomes substantially parallel light at the diffraction portion and is applied to the recording surface. It can be.
[0016]
In each of the optical pickup devices according to the first to third aspects, as in the optical pickup device according to the fourth aspect, the objective lens may include a plurality of the diffraction portions. In such a case, the inclination of the information recording medium can be detected with higher accuracy.
[0017]
In each of the optical pickup devices according to claims 1 to 4, as in the optical pickup device according to claim 5, the second return light beam is a return light beam diffracted in the same direction as an outward path by the diffraction unit. It can be. In such a case, the first photodetector and the second photodetector can be integrated, and the assembling work and the adjusting work can be simplified. That is, the operation cost can be reduced.
[0018]
In each of the optical pickup devices according to the first to fifth aspects, as in the optical pickup device according to the sixth aspect, it is possible to suppress the second light flux from entering the area other than the diffractive portion of the objective lens. May be further provided.
[0019]
In each of the optical pickup devices according to the first to sixth aspects, as in the optical pickup device according to the seventh aspect, a tilt for detecting a tilt of the information recording medium based on an output signal from the second photodetector. Detection means may be further provided.
[0020]
In each of the optical pickup devices according to claims 1 to 7, as in the optical pickup device according to claim 8, a diffractive element that splits the second return light beam to a light receiving position of the second photodetector is provided. Further provisions may be made. In such a case, it is possible to promote downsizing of the optical pickup device.
[0021]
In this case, as in the optical pickup device according to the ninth aspect, the diffraction element can be divided into at least two. In such a case, the position adjustment of the second photodetector becomes easy, and the assembling work and the adjusting work can be simplified.
[0022]
In each of the optical pickup devices according to the eighth and ninth aspects, as in the optical pickup device according to the tenth aspect, the diffraction element is a polarization diffraction element whose diffraction efficiency varies depending on the polarization direction of the incident light beam. It can be. In such a case, almost all of the light flux emitted from the light source can be applied to the information recording medium, and it is possible to cope with high-speed access. Further, the amount of light received by each photodetector increases, and the signal level and the S / N ratio of the output signal from each photodetector can be improved.
[0023]
In each of the optical pickup devices according to claims 8 to 10, as in the optical pickup device according to claim 11, the diffraction element can be driven in conjunction with the objective lens. In such a case, even if the objective lens shifts from its reference position due to, for example, tracking control, no optical axis shift occurs, so that a stable signal can be output from each photodetector.
[0024]
In this case, the diffractive element and the objective lens may be integrated as in the optical pickup device according to the twelfth aspect.
[0025]
In each of the optical pickup devices according to claims 8 to 12, as in the optical pickup device according to claim 13, the first light flux and the second light flux have different wavelengths from each other. it can.
[0026]
In this case, as in the optical pickup device according to the fourteenth aspect, the diffraction element can have different wavelength selectivity whose diffraction efficiency varies depending on the wavelength of the incident light beam.
[0027]
In each of the optical pickup devices according to claims 13 and 14, as in the optical pickup device according to claim 15, when the second light beam is irradiated on a recording surface of a specific type of information recording medium, Part of the second light beam is received by the first photodetector without being diffracted by the diffraction section, and the first photodetector is a signal including at least reproduction information of the specific type of information recording medium. Can be output. In such a case, for a specific type of information recording medium, the light source for detecting the inclination and at least the light source for reproducing the information can be the same.
[0028]
An invention according to claim 16 is an optical disc apparatus that performs at least reproduction of information recording, reproduction, and erasure on an information recording medium, and wherein the optical disc device according to any one of claims 1 to 15 is provided. An optical disc device comprising: a pickup device; and a processing device that performs at least reproduction among recording, reproduction, and erasure of the information by using an output signal from the optical pickup device.
[0029]
According to this, the inclination of the information recording medium can be accurately corrected by using the optical pickup device according to any one of the first to fifteenth aspects. Therefore, as a result, it is possible to accurately and stably access the information recording medium at a high speed.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
<< 1st Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an optical disk device 20 according to the first embodiment of the present invention.
[0031]
The optical disk device 20 shown in FIG. 1 includes a spindle motor 22, an optical pickup device 23, a laser control circuit 24, an encoder 25, a motor driver 27, a reproduction signal processing circuit 28 for rotating and 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. Note that the arrows in FIG. 1 indicate typical flows of signals and information, and do not indicate all of the connection relationships of the respective blocks.
[0032]
The optical pickup device 23 irradiates a laser beam onto a recording surface (hereinafter, simply referred to as a “recording surface”) on which a spiral or concentric track of the optical disk 15 is formed, and receives reflected light from the recording surface. It is a device for performing. The configuration and the like of the optical pickup device 23 will be described later in detail.
[0033]
The reproduction signal processing circuit 28 detects a wobble signal, an RF signal, a servo signal (a focus error signal, a track error signal) and the like based on an output signal from the optical pickup device 23. 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 an error correction process or the like on the RF signal, and stores the RF signal 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.
[0034]
The servo controller 33 generates various control signals for controlling the optical pickup device 23 based on the servo signals, and outputs the control signals to the motor driver 27.
[0035]
The buffer manager 37 manages the input and output of data to and from the buffer RAM 34, and notifies the CPU 40 when the accumulated data amount reaches a predetermined value.
[0036]
The motor 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.
[0037]
The encoder 25 fetches the data stored in the buffer RAM 34 via the buffer manager 37 based on an instruction from the CPU 40, adds an error correction code, etc., creates data to be written on the optical disk 15, and reproduces the data. The write data is output to the laser control circuit 24 in synchronization with the synchronization signal from the signal processing circuit 28.
[0038]
The laser control circuit 24 controls the output of the laser light emitted from the optical pickup device 23 based on the write data from the encoder 25 and the instruction from the CPU 40.
[0039]
The interface 38 is a bidirectional communication interface with a host (for example, a personal computer), and conforms to a standard interface such as an ATAPI (AT Attachment Packet Interface) and a SCSI (Small Computer System Interface).
[0040]
The ROM 39 stores a program described in a code decodable by the CPU 40. Then, the CPU 40 controls the operation of each unit according to the program stored in the ROM 39, and temporarily stores data and the like necessary for the control in the RAM 41.
[0041]
Next, the configuration and the like of the optical pickup device 23 will be described with reference to FIG.
[0042]
As shown in FIG. 2, the optical pickup device 23 includes a first light source unit 51, a first collimating lens 52, a second light source unit 83, a second collimating lens 84, a first beam splitter 81, The second beam splitter 82, the third beam splitter 54, the objective lens 60, the first detection lens 58, the information detection light receiver 59 as a first photodetector, the second detection lens 85, and the second light A tilt detection light receiver 70 as a detector, a tilt detection circuit 75, a drive system (a focusing actuator, a tracking actuator, and a seek motor (all not shown)) and the like are provided.
[0043]
The first light source unit 51 is configured to include a semiconductor laser (not shown) as a light source (hereinafter, also referred to as a “CD light source”) that emits a light beam having a wavelength of 780 nm corresponding to a CD. In the first embodiment, the maximum intensity emission direction of the light beam emitted from the first light source unit 51 is the + X direction. The CD light source is also used as a light source for detecting the inclination of the optical disk 15.
[0044]
The second light source unit 83 is configured to include a semiconductor laser (not shown) as a light source (hereinafter, also referred to as a “DVD light source”) that emits a light beam having a wavelength of 650 nm corresponding to a DVD. In the first embodiment, the maximum intensity emission direction of the light beam emitted from the second light source unit 83 is the + Z direction.
[0045]
The first collimator lens 52 is disposed on the + X side of the first light source unit 51, and converts the light beam emitted from the first light source unit 51 into substantially parallel light. The second collimating lens 84 is arranged on the + Z side of the second light source unit 83, and converts the light beam emitted from the second light source unit 83 into substantially parallel light.
[0046]
As shown in FIGS. 3A and 3B as an example, the objective lens 60 has an area EL called an effective area at the center thereof and an area called a non-effective area outside the effective area EL. It is composed of On the surface of the objective lens 60 on the optical disk 15 side (+ X side), for example, a rectangular diffraction section (diffraction area) 90 is formed in a non-effective area. Here, the diffraction section 90 is formed on the + Z side of the effective area EL. In the first embodiment, a part of the light beam emitted from the first light source unit 51 is set so as to enter the diffraction unit 90. Then, the diffracting unit 90 converts the light beam (second light beam, hereinafter also referred to as “tilt detection light beam”) incident through the outside of the effective area EL of the objective lens 60 substantially parallel to the optical axis of the objective lens 60. It is set to be. Most of the light beam (first light beam, hereinafter also referred to as “information light beam”) incident on the effective area EL of the objective lens 60 is focused on the recording surface.
[0047]
Returning to FIG. 1, the second beam splitter 82 is disposed on the + X side of the first collimating lens 52, and the return light flux from the recording surface of the tilt detection light flux (second return light flux, hereinafter referred to as “tilt detection Return light beam). The second detection lens 85 is disposed on the −Z side of the second beam splitter 82, and the return light beam for tilt detection branched by the second beam splitter 82 is converted into substantially parallel light. The tilt detection light receiver 70 receives the return light beam for tilt detection that has been made substantially parallel by the second detection lens 85.
[0048]
The third beam splitter 54 is disposed between the second beam splitter 82 and the objective lens 60, and divides the light beam emitted from the second light source unit 83 in the + X direction, and outputs the light beam from the recording surface. The return light flux of the information light flux (first return light flux, hereinafter also referred to as “information return light flux”) is branched in the −Z direction.
[0049]
The first beam splitter 81 is disposed on the −Z side of the third beam splitter 54, and branches the return light beam for information in the + X direction.
[0050]
The first detection lens 58 is disposed on the + X side of the first beam splitter 81, and condenses the information return light beam split by the first beam splitter 81. The information detection light receiver 59 receives the information return light beam collected by the first detection lens 58.
[0051]
The information detecting light receiver 59 includes a plurality of light receiving elements for outputting signals optimal for detecting the RF signal, the wobble signal, the servo signal, and the like in the reproduction signal processing circuit 28.
[0052]
As shown in FIG. 4A as an example, the tilt detecting light receiver 70 is divided into two by a dividing line in the direction (here, the Y-axis direction) corresponding to the tangential direction (tangential direction) of the track. It is configured to include a two-divided light receiving element. The two-divided light receiving element is divided into a partial light receiving element 70a and a partial light receiving element 70b, and outputs a signal corresponding to the amount of received light for each partial light receiving element. The tilt detecting light receiver 70 is arranged such that when the tilt (radial tilt) of the optical disc 15 in the radial direction (radial direction) is small, the output signals from the respective partial light receiving elements are substantially equal to each other. Therefore, as the radial tilt of the optical disk 15 increases, the difference between the output signal from the partial light receiving element 70a and the output signal from the partial light receiving element 70b increases. Therefore, information on the radial tilt of the optical disc 15 (information on the amount of tilt and the direction of tilt) can be detected from the difference between the output signal from the partial light receiving element 70a and the output signal from the partial light receiving element 70b.
[0053]
As an example, as shown in FIG. 4B, the tilt detection circuit 75 converts an output signal (current signal) from the partial light receiving element 70a and an output signal (current signal) from the partial light receiving element 70b into a voltage signal S70a. And an S / V conversion circuit 75a, and a subtractor 75b that receives the output signal S70a and the output signal S70b from the IV conversion circuit 75a as input signals and obtains a difference signal therebetween. The output signal ST1 from the subtractor 75b is output to the reproduction signal processing circuit 28 as a tilt detection signal.
[0054]
The operation of the optical pickup device 23 configured as described above will be described.
[0055]
<< When the optical disk 15 is a DVD >>
The case where the optical disk 15 is a DVD will be described. In this case, the first light source unit 51 emits a tilt detection light beam, and the second light source unit 83 emits an information light beam.
[0056]
The light beam emitted from the second light source unit 83 in the + Z direction is converted into substantially parallel light by the second collimating lens 84 and then enters the first beam splitter 81. The light beam transmitted through the first beam splitter 81 and split in the + X direction by the third beam splitter 54 enters the objective lens 60. The light beam (information light beam) incident on the effective area EL of the objective lens 60 is collected as a minute spot on the recording surface.
[0057]
The luminous flux emitted in the + X direction from the first light source unit 51 is converted into substantially parallel light by the first collimating lens 52, and then enters the second beam splitter 82. The light beam transmitted through the second beam splitter 82 and the third beam splitter 54 enters the objective lens 60. The light beam incident on the outside of the effective area EL of the objective lens 60 is condensed, and a part of the light beam (light beam for tilt detection) is incident on the diffraction unit 90. The light beam for tilt detection diffracted by the diffraction unit 90 becomes a light beam substantially parallel to the optical axis of the objective lens 60 and is irradiated on the recording surface. Note that the output power of the light beam emitted from the first light source unit 51 is substantially constant.
[0058]
The information light beam reflected on the recording surface becomes a return light beam (information return light beam), is converted into substantially parallel light again by the objective lens 60, and is incident on the third beam splitter 54. The return light beam for information branched in the −Z direction by the third beam splitter 54 is further branched in the + X direction by the first beam splitter 81, and transmitted by the information detection light receiver 59 via the first detection lens 58. Received. Each light receiving element constituting the information detecting light receiver 59 outputs a signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0059]
On the other hand, the light beam for tilt detection reflected on the recording surface becomes a return light beam (return light beam for tilt detection), and enters the diffraction unit 90 again. The return light flux for tilt detection diffracted by the diffracting unit 90 in a direction different from the outward path becomes divergent light by the objective lens 60 and enters the third beam splitter 54. The return light beam for tilt detection transmitted through the third beam splitter 54 and split by the second beam splitter 82 becomes substantially parallel light by the second detection lens 85 and is received by the tilt detection light receiver 70. Each of the partial light receiving elements constituting the tilt detection light receiver 70 outputs a signal corresponding to the amount of received light to the tilt detection circuit 75.
[0060]
The tilt detection circuit 75 obtains a tilt detection signal based on the output signals from the respective partial light receiving elements constituting the tilt detection light receiver 70 as described above, and outputs the tilt detection signal to the reproduction signal processing circuit 28.
[0061]
Note that the light beam emitted from the first light source unit 51 and incident on the effective area EL of the objective lens 60 is applied to the recording surface in a defocused state, and is output from the information detecting light receiver 59. It does not adversely affect the signal.
[0062]
<< When the optical disk 15 is a CD >>
The case where the optical disk 15 is a CD will be described with reference to FIG. In this case, the first light source unit 51 emits a light beam for tilt detection and a light beam for information.
[0063]
The light beam emitted from the first light source unit 51 in the + X direction enters the objective lens 60 in the same manner as when the optical disk 15 is a DVD. The light beam (information light beam) incident on the effective area EL of the objective lens 60 is collected as a minute spot on the recording surface. On the other hand, the light beam incident on the outside of the effective area EL of the objective lens 60 is collected, and a part of the light beam (tilt detection light beam) is incident on the diffraction unit 90. The light beam for tilt detection diffracted by the diffraction unit 90 becomes a light beam substantially parallel to the optical axis of the objective lens 60 and is irradiated on the recording surface.
[0064]
The information return light beam is received by the information detection light receiver 59 in the same manner as in the case of the DVD described above. Each light receiving element constituting the information detecting light receiver 59 outputs a signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0065]
On the other hand, the return light beam for tilt detection is received by the tilt detection light receiver 70 in the same manner as in the case of the DVD described above. Each of the partial light receiving elements constituting the tilt detection light receiver 70 outputs a signal corresponding to the amount of received light to the tilt detection circuit 75.
[0066]
The tilt detection circuit 75 obtains a tilt detection signal and outputs it to the reproduction signal processing circuit 28 in the same manner as in the case of the DVD described above.
[0067]
Whether the optical disk 15 is a CD or a DVD can be determined from the intensity of light reflected from the recording surface. Usually, this determination is performed when the optical disk 15 is inserted into a predetermined position of the optical disk device 20, that is, at the time of loading. In addition, the type of the optical disc 15 can be determined based on TOC (Table Of Contents) information, PMA (Program Memory Area) information, a wobble signal, and the like, which are recorded in the optical disc 15 in advance. Then, the determination result is notified to the laser control circuit 24, and the laser control circuit 24 selects a light source unit that emits the information light beam.
[0068]
《Recording process》
Next, a processing operation for recording data on the optical disk 15 using the above-described optical disk device 20 will be briefly described.
[0069]
Upon receiving the recording request command from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 to the motor driver 27 based on the specified recording speed, and receives the recording request command from the host. The reproduction signal processing circuit 28 is notified of the fact. Further, the CPU 40 stores the data received from the host in the buffer RAM 34 via the buffer manager 37.
[0070]
When the reproduction signal processing circuit 28 determines that the inclination of the optical disc 15 is larger than a predetermined value based on the tilt detection signal from the tilt detection circuit 75, it adjusts, for example, a seek rail (not shown) of the optical pickup device. Thus, the attitude of the optical pickup device with respect to the optical disk 15 is controlled, and the inclination of the optical disk 15 with respect to the objective lens 60 is corrected. 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 an output signal from the information detecting light receiver 59 and outputs the signals to the servo controller 33. I do.
[0071]
The servo controller 33 drives the tracking actuator of the optical pickup device 23 via the motor driver 27 based on the track error signal, and corrects a track shift. Further, the servo controller 33 drives the focusing actuator of the optical pickup device 23 via the motor driver 27 based on the focus error signal, and corrects a focus shift. In this way, tracking control and focus control are performed.
[0072]
Further, the reproduction signal processing circuit 28 acquires address information based on the output signal from the information detecting light receiver 59 and notifies the CPU 40 of the address information. Then, the CPU 40 outputs a signal for controlling the seek motor of the optical pickup device 23 to the motor driver 27 so that the optical pickup device 23 is located at the write start point designated based on the address information.
[0073]
Upon receiving from the buffer manager 37 that the amount of data stored in the buffer RAM 34 has exceeded a predetermined value, the CPU 40 instructs the encoder 25 to create write data. When 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 data on the optical disc 15 via the laser control circuit 24 and the optical pickup device 23.
[0074]
《Reproduction processing》
Next, a processing operation for reproducing data recorded on the optical disk 15 using the above-described optical disk device 20 will be briefly described.
[0075]
When receiving the reproduction request command from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 to the motor driver 27 based on the reproduction speed, and notifies that the reproduction request command has been received from the host. The reproduction signal processing circuit 28 is notified. Then, in the same manner as in the case of the recording processing, the inclination correction of the optical disk 15 and the tracking control and the focus control of the objective lens 60 are performed. Also, the reproduction signal processing circuit 28 detects the address information and notifies the CPU 40, as in the case of the recording processing.
[0076]
The CPU 40 outputs a signal for controlling the seek motor to the motor driver 27 so that the optical pickup device 23 is located at the reading start point designated based on the address information. When the CPU 40 determines that the position of the optical pickup device 23 is the reading start point based on the address information, it notifies the reproduction signal processing circuit 28.
[0077]
Then, the reproduction signal processing circuit 28 detects the RF signal based on the output signal from the information detection light receiver 59, performs error correction processing and the like, and then stores the signal in the buffer RAM 34. The buffer manager 37 transfers the reproduced data stored in the buffer RAM 34 to the host via the interface 38 when the data is prepared as sector data.
[0078]
Until the recording processing and the reproduction processing are completed, the inclination correction of the optical disc 15 and the tracking control and the focus control of the objective lens 60 are performed as needed.
[0079]
As is apparent from the above description, in the optical disc device 20 according to the first embodiment, a processing device is realized by the reproduction signal processing circuit 28, the CPU 40, and the program executed by the CPU 40. The tilt detection circuit 75 implements a tilt detection unit.
[0080]
As described above, the optical pickup device according to the first embodiment includes the first light source unit 51 corresponding to the CD, the second light source unit 83 corresponding to the DVD, and the objective lens 60. Are formed in the non-effective area. Then, a part of the light beam emitted from the first light source unit 51 via the diffraction unit 90 is irradiated on the recording surface of the optical disk 15, and the tilt of the optical disk 15 with respect to the objective lens 60 is detected using the returned light beam. are doing. Accordingly, among the light beams emitted from the first light source unit 51, a light beam having a relatively high intensity applied to the vicinity of the effective area of the objective lens 60 can be used, so that the tilt detection light receiver 70 is configured. The signal level and the S / N ratio of the output signal from each partial light receiving element can be increased. Further, a new light source for detecting the tilt of the optical disk is not required, and it is possible to prevent an increase in size and cost. Therefore, it is possible to accurately output a signal including information on the inclination of the information recording medium without increasing the size and the cost.
[0081]
Further, according to the optical pickup device according to the first embodiment, when the optical disk 15 is a DVD, the first light source unit 51 corresponding to the CD emits a light beam for tilt detection. The output power of the light beam can be kept constant. Thus, the inclination of the optical disk 15 can be detected with high accuracy.
[0082]
Further, according to the optical disk device according to the first embodiment, the tilt of the optical disk with respect to the objective lens can be accurately corrected based on the tilt detection signal from the optical pickup device. Can be. Similarly, it becomes possible to accurately detect an RF signal, a wobble signal, and the like. That is, it is possible to perform high-speed access with high accuracy and stability. Furthermore, the miniaturization of the optical pickup device can promote the miniaturization of the optical disc device itself and reduction of power consumption. For example, when the optical pickup device is used for portable use, it is easy to carry and can be used for a long time. It becomes.
[0083]
In the first embodiment, the case where the diffraction section 90 is formed on the + Z side of the effective area EL has been described, but the present invention is not limited to this.
[0084]
In the first embodiment, the tilt detecting light receiver 70 includes the two-divided light receiving element divided into two by the dividing line in the Y-axis direction, and the output from each partial light receiving element constituting the two divided light receiving element. The case where the radial tilt of the optical disc 15 is detected based on the signal difference has been described. However, the present invention is not limited to this. For example, a tilt detecting photodetector including a two-division light receiving element divided into two by a dividing line in the X-axis direction may be used. The inclination (tangential tilt) of the optical disk 15 in the tangential direction may be detected based on the difference between the output signals from the respective partial light receiving elements constituting the two-divided light receiving element.
[0085]
Further, for example, by using a tilt detecting light receiver including a four-divided light receiving element divided into four by the dividing lines in the X-axis direction and the Y-axis direction, an output signal from each partial light receiving element constituting the four-divided light receiving element Based on this, the radial tilt and the tangential tilt of the optical disc 15 may be detected.
[0086]
<< 2nd Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIGS.
[0087]
In the second embodiment, as shown in FIG. 6 as an example, an objective lens 61 having two diffraction portions is used instead of the objective lens 60 of the optical pickup device in the first embodiment. It is characterized by points.
[0088]
As shown in FIGS. 7A and 7B as an example, the objective lens 61 has two diffraction sections (diffraction sections) having the same diffraction action as the diffraction section 90 in the first embodiment. 90a and the diffraction portion 90b) are formed in the non-effective area. Here, the diffraction section 90a is formed on the + Z side of the effective area EL, and the diffraction section 90b is formed on the -Z side of the effective area EL.
[0089]
Returning to FIG. 6, a tilt detection light receiver 71 for receiving the return light beam for tilt detection via the diffraction unit 90b is further disposed on the −Z side of the second detection lens 85. As shown in FIG. 8A as an example, the tilt detecting light receiver 71 includes a two-divided light receiving element that is divided into two by a dividing line in the Y-axis direction, similarly to the tilt detecting light receiver 70. It is configured. The two-divided light receiving element is divided into a partial light receiving element 71a and a partial light receiving element 71b, and outputs a signal corresponding to the amount of received light for each partial light receiving element. The tilt detecting light receiver 71 is arranged such that when the radial tilt of the optical disk 15 is small, the output signals from the respective partial light receiving elements are substantially equal to each other.
[0090]
Therefore, in the second embodiment, instead of the tilt detection circuit 75 in the first embodiment, the radial tilt of the optical disc 15 is detected based on the output signals from the two photodetectors 70 and 71 for tilt detection. A tilt detection circuit 76 is used. As an example, as shown in FIG. 8B, the tilt detection circuit 76 converts an output signal (current signal) from the partial light receiving element 70a into a voltage signal S70a and an output signal (current signal) from the partial light receiving element 70b. Into an voltage signal S70b, an output signal (current signal) from the partial light receiving element 71a into a voltage signal S71a, and an output signal (current signal) from the partial light receiving element 71b into an voltage-converting signal S71b. , An output signal S70a and an output signal S70b from the IV conversion circuit 76a as input signals, and a subtractor 76b for obtaining a difference signal DS1 between them, and an output signal S71a and an output signal S71b from the IV conversion circuit 76a. A subtractor 76c for obtaining a difference signal DS2 between them as input signals, an output signal DS1 from the subtractor 76b and an output signal D from the subtractor 76c And a like adder 76d for adding the 2. The output signal ST2 from the adder 76d is output to the reproduction signal processing circuit 28 as a tilt detection signal.
[0091]
The other configurations of the optical pickup device and the optical disk device are the same as those of the first embodiment. Therefore, in the following, description will be made focusing on differences from the first embodiment, and the same reference numerals will be used for the same or equivalent components as those in the first embodiment, and the description thereof will be simplified or It shall be omitted.
[0092]
The operation of the optical pickup device 23 configured as described above will be described.
[0093]
<< When the optical disk 15 is a DVD >>
The case where the optical disk 15 is a DVD will be described. In this case, as in the first embodiment, the first light source unit 51 emits a light beam for tilt detection, and the second light source unit 83 emits a light beam for information.
[0094]
The light beam emitted in the + Z direction from the second light source unit 83 enters the objective lens 60 in the same manner as in the first embodiment. The light beam (information light beam) incident on the effective area EL of the objective lens 60 is collected as a minute spot on the recording surface.
[0095]
The light beam emitted in the + X direction from the first light source unit 51 enters the objective lens 61 in the same manner as in the first embodiment. The light beam incident on the outside of the effective area EL of the objective lens 61 is condensed, and a part of the light beam (tilt detection light beam) is incident on the diffraction units 90a and 90b. The light beam for tilt detection diffracted by each diffracting unit is irradiated on the recording surface as a light beam substantially parallel to the optical axis of the objective lens 61. Note that the output power of the light beam emitted from the first light source unit 51 is substantially constant.
[0096]
The information return light beam is received by the information detection light receiver 59 in the same manner as in the first embodiment. Each of the light receiving elements constituting the information detecting light receiver 59 outputs a signal corresponding to the amount of received light to the reproduction signal processing circuit 28.
[0097]
On the other hand, the return light beam of the tilt detection light beam (the tilt detection return light beam) applied to the recording surface via the diffraction unit 90a enters the diffraction unit 90a again. Then, the return light for tilt detection diffracted by the diffracting unit 90 a in a direction different from the forward path becomes divergent light by the objective lens 60 and enters the third beam splitter 54. The return light beam for tilt detection transmitted through the third beam splitter 54 and split by the second beam splitter 82 becomes substantially parallel light by the second detection lens 85 and is received by the tilt detection light receiver 70. Each of the partial light receiving elements constituting the tilt detecting light receiver 70 outputs a signal corresponding to the amount of received light to the tilt detecting circuit 76.
[0098]
Also, the return light flux of the tilt detection light flux (the tilt detection return light flux) applied to the recording surface via the diffraction unit 90b enters the diffraction unit 90b again. Then, the return light for tilt detection diffracted in a direction different from the outward path by the diffraction unit 90b becomes divergent light by the objective lens 60 and enters the third beam splitter 54. The return light flux for tilt detection transmitted through the third beam splitter 54 and split by the second beam splitter 82 becomes substantially parallel light by the second detection lens 85, and is received by the tilt detection light receiver 71. Each of the partial light receiving elements constituting the tilt detecting light receiver 71 outputs a signal corresponding to the amount of received light to the tilt detecting circuit 76.
[0099]
In the tilt detection circuit 76, as described above, a tilt detection signal is obtained based on output signals from the respective partial light receiving elements constituting the tilt detecting light receiver 70 and the respective partial light receiving elements constituting the tilt detecting light receiver 71, and reproduced. The signal is output to the signal processing circuit 28.
[0100]
<< When the optical disk 15 is a CD >>
The case where the optical disk 15 is a CD will be described with reference to FIG. In this case, similarly to the first embodiment, the first light source unit 51 emits the light beam for tilt detection and the light beam for information.
[0101]
The light beam emitted in the + X direction from the first light source unit 51 enters the objective lens 60 in the same manner as in the case of the DVD. The light beam (information light beam) incident on the effective area EL of the objective lens 61 is collected as a minute spot on the recording surface. On the other hand, the light beam incident on the outside of the effective area EL of the objective lens 61 is condensed, and a part of the light beam (tilt detection light beam) is incident on the diffraction units 90a and 90b. The light beam for tilt detection diffracted by each diffracting unit is irradiated on the recording surface as a light beam substantially parallel to the optical axis of the objective lens 61.
[0102]
The information return light beam is received by the information detection light receiver 59 in the same manner as in the first embodiment. Each of the light receiving elements constituting the information detecting light receiver 59 outputs a signal corresponding to the amount of received light to the reproduction signal processing circuit 28. On the other hand, the return light beam of the tilt detection light beam (the return light beam for tilt detection) applied to the recording surface of the optical disc 15 via the diffraction unit 90a and the diffraction unit 90b is similar to the above-described DVD. The light is received by the light receiver 70 and the tilt detection light receiver 71, respectively.
[0103]
The tilt detection circuit 76 obtains a tilt detection signal and outputs it to the reproduction signal processing circuit 28 in the same manner as in the case of the DVD described above.
[0104]
As is apparent from the above description, in the optical disc device 20 according to the second embodiment, the tilt detection circuit 76 implements a tilt detection unit. Further, as in the first embodiment, the processing device is realized by the reproduction signal processing circuit 28, the CPU 40, and the program executed by the CPU 40, and the recording device is realized in the same manner as in the first embodiment. Processing and reproduction processing are performed.
[0105]
As described above, the optical pickup device according to the second embodiment includes the first light source unit 51 corresponding to the CD, the second light source unit 83 corresponding to the DVD, and the objective lens 61. Are formed in the non-effective area. Then, a part of the light beam emitted from the first light source unit 51 is irradiated on the recording surface via each diffraction unit, and the tilt of the optical disk 15 with respect to the objective lens 61 is detected using the returned light beam. . Thereby, the same effect as that of the optical pickup device according to the first embodiment can be obtained, and the signal level and the S / N ratio of the output signal from the tilt detection circuit 76 can be reduced as compared with the first embodiment. It can be even higher.
[0106]
Further, according to the optical disk device according to the second embodiment, the inclination of the optical disk with respect to the objective lens can be accurately corrected based on the tilt detection signal from the optical pickup device. The same effect as that of the optical disk device can be obtained.
[0107]
In the above-described second embodiment, the case where each diffraction portion is formed on the + Z side and the −Z side of the effective area EL has been described, but the present invention is not limited to this.
[0108]
Further, in the second embodiment, each tilt detecting light receiver includes a two-divided light receiving element divided into two by a dividing line in the Y-axis direction, and an output from each partial light receiving element constituting the two divided light receiving element. The case where the radial tilt of the optical disc is detected based on the signal difference has been described. However, the present invention is not limited to this. Each tilt detection light receiver includes, for example, a two-divided light receiving element divided into two by a dividing line in the X-axis direction. Alternatively, the tangential tilt of the optical disc may be detected based on the difference between the output signals from the respective partial light receiving elements constituting the two-divided light receiving element.
[0109]
Further, at least one of the tilt detection light receivers includes, for example, a four-divided light receiving element divided into four by a dividing line in the X-axis direction and the Y-axis direction. , The radial tilt and the tangential tilt of the optical disc 15 may be detected.
[0110]
In the second embodiment, the case where the number of the diffraction portions is two has been described, but the present invention is not limited to this. For example, as shown in FIG. 10, an objective lens 62 in which two diffraction portions 90c and 90d are further formed at positions separated in the Y-axis direction may be used. In this case, for example, the radial tilt of the optical disk is detected based on the return light beam for tilt detection via the diffraction units 90a and 90b, and the tangential of the optical disk is detected based on the return light beam for tilt detection via the diffraction units 90c and 90d. The initial tilt may be detected.
[0111]
<< 3rd Embodiment >>
Next, a third embodiment of the present invention will be described with reference to FIGS.
[0112]
As shown in FIG. 11 as an example, the third embodiment is characterized in that a diffraction element 65 is used instead of the first beam splitter 81 and the second beam splitter 82 in the first embodiment. Having. The diffraction element 65 is disposed between the first light source unit 51 and the first collimating lens 52. Accordingly, the information detection light receiver 59 and the tilt detection light receiver 70 receive the information return light beam and the tilt detection return light beam diffracted by the diffraction element 65, respectively, and are the same as in the first embodiment. It is arranged at a position where it is possible to output various signals. As an example, as shown in FIG. 13A, the return beam for information SL and the return beam TL for tilt detection are assumed to be subjected to the same diffraction action by the diffraction element 65, respectively. In this case, the detection lenses (the first detection lens 58 and the second detection lens 85) in the first embodiment are unnecessary.
[0113]
The other configurations of the optical pickup device and the optical disk device are the same as those of the first embodiment. Therefore, in the following, description will be made focusing on differences from the first embodiment, and the same reference numerals will be used for the same or equivalent components as those in the first embodiment, and the description thereof will be simplified or It shall be omitted.
[0114]
The operation of the optical pickup device 23 configured as described above will be described.
[0115]
<< When the optical disk 15 is a DVD >>
The case where the optical disk 15 is a DVD will be described. In this case, as in the first embodiment, the first light source unit 51 emits a light beam for tilt detection, and the second light source unit 83 emits a light beam for information.
[0116]
The luminous flux emitted in the + Z direction from the second light source unit 83 is converted into substantially parallel light by the second collimating lens 84 and then enters the third beam splitter 54. The light beam split in the + X direction by the third beam splitter 54 enters the objective lens 60. The light beam (information light beam) incident on the effective area EL of the objective lens 60 is collected as a minute spot on the recording surface.
[0117]
The light beam emitted from the light source unit 51 in the + X direction enters the diffraction element 65. The light beam transmitted through the diffraction element 65 is converted into substantially parallel light by the first collimator lens 52, and then enters the third beam splitter 54. The light beam transmitted through the third beam splitter 54 enters the objective lens 61. The light beam incident on the outside of the effective area EL of the objective lens 60 is condensed, and a part of the light beam (light beam for tilt detection) is incident on the diffraction unit 90. The light beam for tilt detection diffracted by the diffraction unit 90 becomes a light beam substantially parallel to the optical axis of the objective lens 60 and is irradiated on the recording surface.
[0118]
The return light beam for information is converted into substantially parallel light again by the objective lens 60, and enters the third beam splitter 54. The return light beam for information transmitted through the third beam splitter 54 enters the diffraction element 65 via the first collimator lens 52. The return light beam for information diffracted by the diffraction element 65 is received by the light detector 59 for information detection.
[0119]
On the other hand, the return light flux for tilt detection enters the diffraction unit 90 again. The return light flux for tilt detection diffracted by the diffracting unit 90 in a direction different from the outward path becomes divergent light by the objective lens 60 and enters the third beam splitter 54. The return light flux for tilt detection transmitted through the third beam splitter 54 is incident on the diffraction element 65 via the first collimator lens 52. The return light flux for tilt detection diffracted by the diffraction element 65 is received by the tilt detection light receiver 70. The tilt detection circuit 75 obtains a tilt detection signal in the same manner as in the first embodiment, and outputs the tilt detection signal to the reproduction signal processing circuit 28.
[0120]
<< When the optical disk 15 is a CD >>
The case where the optical disk 15 is a CD will be described with reference to FIG. In this case, a light beam for tilt detection and a light beam for information are emitted from the first light source unit 51 as in the first embodiment.
[0121]
The light beam emitted in the + X direction from the first light source unit 51 enters the objective lens 60 in the same manner as in the case of the DVD described above. The light beam (information light beam) incident on the effective area EL of the objective lens 60 is collected as a minute spot on the recording surface. On the other hand, a part of the light beam incident on the outside of the effective area EL of the objective lens 60 (light beam for tilt detection) is applied to the recording surface in the same manner as in the first embodiment.
[0122]
The information return light beam is received by the information detection light receiver 59, and the tilt detection return light beam is received by the tilt detection light receiver 70, as in the case of the DVD described above. The tilt detection circuit 75 obtains a tilt detection signal in the same manner as in the first embodiment, and outputs the tilt detection signal to the reproduction signal processing circuit 28.
[0123]
As is apparent from the above description, in the optical disc device 20 according to the third embodiment, the tilt detection circuit 75 implements a tilt detection unit. Further, as in the first embodiment, the processing device is realized by the reproduction signal processing circuit 28, the CPU 40, and the program executed by the CPU 40, and the recording device is realized in the same manner as in the first embodiment. Processing and reproduction processing are performed.
[0124]
As described above, the optical pickup device according to the third embodiment includes the first light source unit 51 corresponding to the CD, the second light source unit 83 corresponding to the DVD, and the objective lens 60. Are formed in the non-effective area. Then, a part of the light beam emitted from the first light source unit 51 is irradiated to the recording surface via the diffraction unit 90, and the inclination of the optical disk 15 with respect to the objective lens 60 is detected by using the returned light beam. I have. Therefore, the same effects as those of the optical pickup device according to the first embodiment can be obtained. Further, a diffraction element 65 for splitting return light beams (information return light beam and tilt detection return light beam) is arranged on a common optical path of the forward and return paths of the light beam emitted from the first light source unit 51. . This eliminates the need for the first beam splitter 81, the second beam splitter 82, and the detection lens in the first embodiment, and can promote downsizing and cost reduction of the optical pickup device.
[0125]
Further, according to the optical disk device according to the third embodiment, the inclination of the optical disk 15 with respect to the objective lens 60 can be accurately corrected based on the tilt detection signal from the optical pickup device. The same effect as that of the optical disk device according to the embodiment can be obtained.
[0126]
In the third embodiment, a case has been described in which the return beam for information and the return beam for tilt detection are each subjected to the same diffraction action by the diffraction element 65. However, the present invention is not limited to this, and FIG. As shown in (), a diffraction element 66 having different diffraction effects on the information return light beam SL and the tilt detection return light beam TL may be used in place of the diffraction element 65. The diffraction element 66 includes a partial area 66a for diffracting the return light flux SL for information, and a partial area for diffracting the return light flux TL for tilt detection. The partial region for diffracting the return light beam TL for tilt detection is further divided into two partial regions 66b and 66c by a dividing line in the Y-axis direction. In this case, since the tilt detection return light beam SL is split into two light beams by the diffraction element 66, a single light receiving element is used as a light receiver for receiving the tilt detection return light beam, instead of a two-part light receiving element. Two can be used, and the assembling work and the adjusting work of the light receiver become easy. That is, the operation cost can be reduced.
[0127]
Further, in the third embodiment, the case where the tilt of the optical disc 15 is detected by using the return light flux for tilt detection diffracted by the diffracting unit 90 in a direction different from the outward path has been described. As shown in FIG. 14, a return beam for tilt detection diffracted by the diffraction unit 90 in the same direction as the outward path may be used. In this case, the light receiving position of the return light beam for information in the X-axis direction is substantially equal to the light receiving position of the return light beam for tilt detection. 95 can be used. This facilitates the work of assembling and adjusting the light receiver.
[0128]
<< 4th Embodiment >>
Next, a fourth embodiment of the present invention will be described with reference to FIG.
[0129]
The fourth embodiment is characterized in that, as an example, as shown in FIG. 15, a diffraction element 65 is used instead of the first beam splitter 81 and the second beam splitter 82 in the second embodiment. Having. The diffraction element 65 is disposed between the first light source unit 51 and the first collimating lens 52. Accordingly, the information detection light receiver 59 and the tilt detection light receivers 70 and 71 receive the information return light beam and the tilt detection return light beam diffracted by the diffraction element 65, respectively, and the second embodiment described above. It is arranged at a position where it is possible to output a signal similar to the above. In this case, the detection lenses (the first detection lens 58 and the second detection lens 85) in the second embodiment are unnecessary.
[0130]
The other configurations of the optical pickup device and the optical disk device are the same as those of the second embodiment. Therefore, in the following, description will be made focusing on the differences from the second embodiment, and the same reference numerals will be used for the same or equivalent components as those in the second embodiment, and the description thereof will be simplified or It shall be omitted.
[0131]
The operation of the optical pickup device 23 configured as described above will be described. Here, only the case where the optical disk 15 is a DVD will be described. In this case, as in the first embodiment, the first light source unit 51 emits a light beam for tilt detection, and the second light source unit 83 emits a light beam for information.
[0132]
The luminous flux emitted in the + Z direction from the second light source unit 83 is converted into substantially parallel light by the second collimating lens 84 and then enters the third beam splitter 54. The light beam split in the + X direction by the third beam splitter 54 enters the objective lens 60. The light beam (information light beam) incident on the effective area EL of the objective lens 60 is collected as a minute spot on the recording surface.
[0133]
The light beam emitted in the + X direction from the first light source unit 51 enters the diffraction element 65. The light flux transmitted through the diffraction element 65 is converted into substantially parallel light by the first collimator lens 52, and then enters the objective lens 61 via the third beam splitter 54. The light beam incident on the outside of the effective area of the objective lens 61 is collected, and a part of the light beam (tilt detection light beam) is incident on the diffraction units 90a and 90b. The light beams for tilt detection diffracted by the respective diffracting portions are respectively irradiated on the recording surface as substantially parallel lights.
[0134]
The return light beam for information is converted into substantially parallel light again by the objective lens 61, and enters the diffraction element 65 via the third beam splitter 54 and the first collimator lens 52. The return light beam for information diffracted by the diffraction element 65 is received by the light detector 59 for information detection.
[0135]
On the other hand, the return light beam of the tilt detection light beam (the tilt detection return light beam) applied to the recording surface of the optical disk 15 via the diffraction unit 90a is incident on the diffraction unit 90a again. The return light flux for tilt detection diffracted in a direction different from the outward path by the diffraction unit 90a becomes divergent light by the objective lens 61, and enters the diffraction element 65 via the third beam splitter 54 and the first collimating lens 52. . The return light flux for tilt detection diffracted by the diffraction element 65 is received by the tilt detection light receiver 70.
[0136]
In addition, the return light flux of the tilt detection light flux (the tilt detection return light flux) applied to the recording surface of the optical disc 15 via the diffraction unit 90b enters the diffraction unit 90b again. The return light flux for tilt detection diffracted in a direction different from the outward path by the diffraction unit 90b becomes divergent light by the objective lens 61, and enters the diffraction element 65 via the third beam splitter 54 and the first collimator lens 52. . The return light flux for tilt detection diffracted by the diffraction element 65 is received by the tilt detection light receiver 71.
[0137]
The tilt detection circuit 76 obtains a tilt detection signal in the same manner as in the second embodiment, and outputs the tilt detection signal to the reproduction signal processing circuit 28.
[0138]
As is apparent from the above description, in the optical disk device 20 according to the fourth embodiment, the tilt detection circuit 76 implements a tilt detection unit. Further, as in the first embodiment, the processing device is realized by the reproduction signal processing circuit 28, the CPU 40, and the program executed by the CPU 40, and the recording device is realized in the same manner as in the first embodiment. Processing and reproduction processing are performed.
[0139]
As described above, the optical pickup device according to the fourth embodiment includes the first light source unit 51 corresponding to the CD, the second light source unit 83 corresponding to the DVD, and the objective lens. Two diffraction portions are formed in the non-effective area. Then, a part of the light beam emitted from the first light source unit 51 is irradiated to the recording surface via each diffraction unit, and the tilt of the optical disk 15 with respect to the objective lens 61 is detected using the returned light beam. . Thereby, the same effect as that of the optical pickup device according to the first embodiment can be obtained, and the signal level and the S / N ratio of the output signal from the tilt detection circuit 76 can be reduced as compared with the first embodiment. It can be even higher. In addition, a diffractive element 65 for splitting a return light beam (information return light beam and tilt detection return light beam) is arranged on a common optical path of a forward light beam and a return light beam of the light beam emitted from the first light source unit 51. . This eliminates the need for the first beam splitter 81, the second beam splitter 82, and the detection lens in the first embodiment, and can promote downsizing and cost reduction of the optical pickup device.
[0140]
Further, according to the optical disc device of the fourth embodiment, the tilt of the optical disc with respect to the objective lens can be accurately corrected based on the tilt detection signal from the optical pickup device. The same effect as that of the optical disk device can be obtained.
[0141]
In the fourth embodiment, the case where the tilt of the optical disc 15 is detected by using the return light flux for tilt detection diffracted by the diffraction unit 90a and the diffraction unit 90b in a direction different from the outward path has been described. The present invention is not limited to this. For example, as shown in FIG. 16, a return light beam for tilt detection that is diffracted in the same direction as the outward path by the diffraction units 90a and 90b may be used. In this case, the light receiving position of the return light beam for information in the X-axis direction is equal to the light receiving position of the return light beam for tilt detection. Can be used. Thereby, the assembling work and the adjusting work of the light receiver become easy, and the working cost can be reduced.
[0142]
In this case, as shown in FIG. 17, for example, a polarization diffraction element 67 whose diffraction efficiency differs depending on the polarization direction of the incident light beam may be used instead of the diffraction element 65. In this case, the λ / 4 plate 55 is connected to the third beam splitter 54 and the objective so that the polarization direction of the return light beam and the polarization direction of the light beam emitted from each light source unit are shifted by about 90 degrees. It is located between the lens 61. For example, when a P-polarized light beam is emitted from each light source unit, the polarization diffraction element 67 has a low diffraction efficiency for a P-polarized light beam and a high diffraction efficiency for an S-polarized light beam. It is set to be.
[0143]
The operation of the optical pickup device 23 in this case will be briefly described. Here, only the case where the optical disk 15 is a DVD will be described.
[0144]
The light beam of linearly polarized light (here, P-polarized light) emitted from the second light source unit 83 in the + Z direction is converted into substantially parallel light by the second collimating lens 84, and then enters the third beam splitter 54. The beam split in the + X direction by the third beam splitter 54 is made into a circularly polarized light by the λ / 4 plate 55 and then enters the objective lens 60. Then, the information light beam is applied to the recording surface as described above.
[0145]
The light beam of linearly polarized light (here, P-polarized light) emitted from the first light source unit 51 in the + X direction enters the polarization diffraction element 67. The polarization diffraction element 67 transmits most of the incident light beam because the diffraction efficiency for the P-polarized light beam is low. The light beam transmitted through the polarization diffraction element 67 is converted into substantially parallel light by the first collimator lens 52, and then enters the third beam splitter 54. The light beam transmitted through the third beam splitter 54 is circularly polarized by the λ / 4 plate 55, and then enters the objective lens 61. Then, the recording surface is irradiated with the tilt detection light beam as described above.
[0146]
The return light beam for information becomes circularly polarized light in the opposite direction to the outward path, is converted into substantially parallel light again by the objective lens 61, and is converted from circularly polarized light into linearly polarized light (here, S-polarized light) by the λ / 4 plate 55. , And enters the polarization diffraction element 67 via the third beam splitter 54 and the first collimating lens 52. The return light beam for information incident on the polarization diffraction element 67 is diffracted with high diffraction efficiency and received by the light receiver 96.
[0147]
On the other hand, the return light beam of the tilt detection light beam (tilt detection return light beam) applied to the recording surface via the diffraction unit 90a becomes circularly polarized light in the opposite direction to the outward path, and enters the diffraction unit 90a again. The return light for tilt detection diffracted in the same direction as the outward path by the diffraction unit 90a becomes divergent light by the objective lens 61, and is converted from circularly polarized light to linearly polarized light (here, S-polarized light) by the λ / 4 plate 55. Thereafter, the light is incident on the polarization diffraction element 67 via the third beam splitter 54 and the first collimating lens 52. The return light flux for tilt detection that has entered the polarization diffraction element 67 is diffracted with high diffraction efficiency and received by the light receiver 96.
[0148]
Further, the return light flux of the tilt detection light flux (the tilt detection return light flux) applied to the recording surface via the diffraction section 90b becomes circularly polarized light in the opposite direction to the outward path, and enters the diffraction section 90b again. The return light beam for tilt detection diffracted in the same direction as the outward path by the diffraction unit 90b becomes divergent light by the objective lens 61, and is converted from circularly polarized light to linearly polarized light (here, S-polarized light) by the λ / 4 plate 55. Thereafter, the light is incident on the polarization diffraction element 67 via the third beam splitter 54 and the first collimating lens 52. The return light flux for tilt detection that has entered the polarization diffraction element 67 is diffracted with high diffraction efficiency and received by the light receiver 96.
[0149]
As a result, the decrease in the amount of the light beam irradiated on the recording surface is extremely reduced, and it is easy to cope with an increase in the recording speed. In addition, the signal level and the S / N ratio of the signal output from each light receiver can be improved by increasing the amount of light received by each light receiver.
[0150]
Further, as an example, as shown in FIG. 18, the polarization diffraction element 67, the λ / 4 plate 55, and the objective lens 61 may be arranged in the same housing 98, and may be driven integrally. Accordingly, even if the objective lens 61 shifts in the tracking direction due to the tracking control, the positional relationship among the polarization diffraction element 67, the λ / 4 plate 55, and the objective lens 61 does not change. Offset).
[0151]
In each of the above embodiments, the case where the diffractive portion is formed in the non-effective area of the objective lens is described. However, the present invention is not limited to this. For example, at least a part of the diffractive portion is formed in the effective area of the objective lens. Is also good.
[0152]
In each of the above embodiments, the case where the diffractive portion is formed on the objective lens is described. However, the present invention is not limited to this, and a thin film on which a diffraction grating is formed may be attached to the objective lens.
[0153]
Further, in each of the embodiments described above, the case where the tilt detection signal is obtained on the optical pickup device 23 side is described. However, the present invention is not limited to this. And a tilt detection signal may be obtained.
[0154]
In each of the above embodiments, at least a part of the processing device realized by processing according to the program by the CPU 40 may be configured by hardware, or all of the processing device may be configured by hardware.
[0155]
Further, in each of the above embodiments, the case where there are two light sources has been described, but the present invention is not limited to this. For example, a light source that emits a light beam with a wavelength of 405 nm, a light source that emits a light beam with a wavelength of 650 nm, and a light source that emits a light beam with a wavelength of 780 nm may be provided.
[0156]
In each of the above embodiments, the case where the CD light source also serves as the light source for detecting the tilt of the optical disk has been described, but the present invention is not limited to this. For example, a light source for detecting the tilt of the optical disk may be provided in addition to the CD light source and the DVD light source. The wavelength of the light beam emitted from the light source may be different from the wavelength of each light beam emitted from the CD light source and the DVD light source, or the wavelength of the light beam emitted from either the CD light source or the DVD light source. May be the same as
[0157]
In each of the above embodiments, when the optical disk 15 is a DVD, a light-shielding unit such as a diaphragm may be arranged so that a light beam emitted from the CD light source does not enter the effective area of the objective lens. Further, for example, when a dedicated light source for detecting the inclination of the optical disk is used, a fixed type light shielding unit may be provided.
[0158]
Further, in each of the above embodiments, a diffraction section having a wavelength selectivity having a different diffraction efficiency depending on the wavelength of the incident light beam may be formed in the objective lens.
[0159]
In each of the above embodiments, a diffraction element having a wavelength selectivity having a different diffraction efficiency according to the wavelength of the incident light beam may be used instead of the diffraction element 65. Thereby, in the diffraction element, only the light beam of the wavelength used for tilt detection is diffracted, and the light beams of other wavelengths are not diffracted, so that the light beams of other wavelengths can be prevented from becoming flare light, and the accuracy is high. A tilt detection signal can be obtained. In addition, since the light use efficiency is improved for light beams of other wavelengths, it is possible to cope with high speed.
[0160]
In each of the above embodiments, the optical disk device capable of recording and reproducing information has been described. However, the present invention is not limited to this, and any optical disk device capable of at least reproducing, among recording, reproducing, and erasing information, may be used.
[0161]
【The invention's effect】
As described above, according to the optical pickup device of the present invention, it is possible to accurately output a signal including information on the tilt of an information recording medium with respect to an objective lens without increasing the size and cost. effective.
[0162]
Further, according to the optical disc device of the present invention, there is an effect that high-speed access to the information recording medium can be performed accurately and stably.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a schematic configuration of an optical disc device according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining a configuration of the optical pickup device according to the first embodiment.
FIGS. 3A and 3B are views for explaining the objective lens in FIG. 2;
4A is a diagram for explaining a configuration of a tilt detection light receiver in FIG. 2; FIG. 4B is a diagram for explaining a configuration of a tilt detection circuit in FIG. 2; FIG.
FIG. 5 is a diagram for explaining the operation of the optical pickup device of FIG. 2 when the optical disc is a CD.
FIG. 6 is a diagram illustrating a configuration of an optical pickup device according to a second embodiment.
7 (A) and 7 (B) are diagrams for explaining the objective lens in FIG. 6, respectively.
8A is a diagram for explaining a configuration of a tilt detection light receiver in FIG. 6, and FIG. 8B is a diagram for explaining a configuration of a tilt detection circuit in FIG. 6; FIG.
FIG. 9 is a diagram for explaining the operation of the optical pickup device of FIG. 6 when the optical disc is a CD.
FIG. 10 is a diagram for explaining an example in which a diffraction unit for detecting a tangential tilt of an optical disc is added to the objective lens in FIG. 7;
FIG. 11 is a diagram illustrating a configuration of an optical pickup device according to a third embodiment.
FIG. 12 is a diagram for explaining the operation of the optical pickup device of FIG. 11 when the optical disc is a CD.
13A is a diagram for explaining a diffraction element in FIG. 11, and FIG. 13B is a diagram for explaining a modification example thereof.
14 is a diagram for explaining an example in which the tilt of the optical disc is detected by using the return light beam diffracted in the same direction as the outward path by the diffraction unit using the objective lens in FIG. 11;
FIG. 15 is a diagram illustrating a configuration of an optical pickup device according to a fourth embodiment.
16 is a diagram for explaining an example in which the tilt of the optical disc is detected by using the return light beam diffracted in the same direction as the outward path by the diffraction unit using the objective lens in FIG.
17 is a diagram for explaining an example in which a polarization diffraction element is used instead of the diffraction element in FIG.
18 is a diagram for explaining an example in which the polarization diffraction element, the λ / 4 plate, and the objective lens in FIG. 17 are integrated.
[Explanation of symbols]
15 optical disk (information recording medium), 20 optical disk device, 23 optical pickup device, 28 reproduction signal processing circuit (part of processing device), 40 CPU (part of processing device), 59 information detection Photodetectors (first photodetectors), 60, 61, 62 ... objective lenses, 65, 66 ... diffraction elements, 67 ... polarization diffraction elements, 70, 71 ... tilt detection photodetectors (second photodetectors) , 75, 76... Tilt detection circuit (tilt detecting means), 90, 90a, 90b, 90c, 90d... Diffraction part, EL... Effective area, SL... Information return light beam (first return light beam), TL. Return light beam (second return light beam).

Claims (16)

An optical pickup device that irradiates light to a recording surface of an information recording medium and receives reflected light from the recording surface,
A plurality of light sources including light sources that individually emit the first light beam and the second light beam;
An objective lens disposed on an optical path of each of the light beams and having at least one diffraction portion that diffracts the second light beam;
A first light detection for receiving a first return light flux from the recording surface of the first light flux condensed on the recording surface via the objective lens, the first return light flux having passed through the objective lens; Vessel and;
Receiving the second return light flux from the recording surface of the second light flux diffracted by the diffraction unit and applied to the recording surface, the second return light flux being diffracted again by the diffraction unit; A second photodetector that outputs a signal including tilt information of the recording medium. The optical pickup device according to claim 1, wherein the diffraction unit is provided outside an effective area of the objective lens. 3. The optical pickup device according to claim 1, wherein the second light flux is converted into substantially parallel light by the diffraction unit and is applied to the recording surface. The optical pickup device according to claim 1, wherein the objective lens includes a plurality of the diffraction units. 5. The optical pickup device according to claim 1, wherein the second return light beam is a return light beam diffracted in the same direction as the outward path by the diffraction unit. 6. The optical pickup according to claim 1, further comprising a light blocking unit configured to suppress the second light flux from entering a region other than the diffraction unit of the objective lens. apparatus. The optical pickup device according to any one of claims 1 to 6, further comprising a tilt detection unit configured to detect a tilt of the information recording medium based on an output signal from the second photodetector. The optical pickup device according to claim 1, further comprising a diffraction element that branches the second return light flux to a light receiving position of the second photodetector. 9. The optical pickup device according to claim 8, wherein the diffraction element is divided into at least two. 10. The optical pickup device according to claim 8, wherein the diffraction element is a polarization diffraction element whose diffraction efficiency varies depending on the polarization direction of the incident light beam. The optical pickup device according to claim 8, wherein the diffraction element is drivable in conjunction with the objective lens. The optical pickup device according to claim 11, wherein the diffraction element and the objective lens are integrated. The optical pickup device according to any one of claims 8 to 12, wherein the first light beam and the second light beam have different wavelengths from each other. 14. The optical pickup device according to claim 13, wherein the diffraction element has a wavelength selectivity whose diffraction efficiency varies depending on the wavelength of the incident light beam. When the second light beam is applied to a recording surface of a specific type of information recording medium, a part of the second light beam is received by the first photodetector without being diffracted by the diffraction unit. 15. The optical pickup device according to claim 13, wherein the first photodetector outputs a signal including at least reproduction information of the specific type of information recording medium. An optical disc device that performs at least reproduction of information recording, reproduction, and erasure on an information recording medium,
An optical pickup device according to any one of claims 1 to 15, and
An optical disk device comprising: a processing device that performs at least reproduction among recording, reproduction, and erasure of the information by using an output signal from the optical pickup device.

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