JP2003203379A - Optical pickup device and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup device, by which the information regarding the position of an objective lens is accurately detected without spliting luminous flux coming from a light source and also without incurring the increase of scale and cost. <P>SOLUTION: The device is furnished with a driving device for driving a deflecting optical element 56 and an objective lens 60 to the tracking direction by making them to link each other while arranging the deflecting optical element and the objective lens on an optical path guiding the return luminous flux reflected on a recording surface to a 1st photodetector 59. A spliting optical element 57 is arranged on the optical path, in which an optical axis of the return luminous flux is shifted in accordance with the movement of the objective lens by the driving device, for optically spliting the return luminous flux, and a 2nd photodetector 61 is arranged for receiving the luminous flux split from the optical path advancing toward the light receiving position by the spliting optical element. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device and an optical disc device, and more particularly to an optical pickup device suitable for performing at least one of recording and / or reproducing information at a high speed, and the optical pickup device. Optical disk device.

[0002]

2. Description of the Related Art In an optical disk device, for example, a CD (comp
Information is recorded on an optical recording medium such as an act disc) or a DVD (digital versatile disc) by irradiating a minute spot of laser light on the recording surface on which the spiral or concentric tracks are formed. Information is reproduced based on the light reflected from the recording surface. The optical disc device is provided with an optical pickup device for irradiating the recording surface of the optical recording medium with laser light and receiving reflected light from the recording surface.

Generally, an optical pickup device includes a light source and an objective lens, guides a light beam emitted from the light source to a recording surface of an optical recording medium, and guides a return light beam reflected by the recording surface to a predetermined light receiving position. It is provided with an optical system and a light receiving element arranged at a light receiving position.

In recent years, information equipment typified by a personal computer (personal computer) has become smaller and less expensive,
In particular, mobile personal computers are rapidly becoming popular. Along with this, there is an increasing demand for thinning and cost reduction of an optical disk device, which is one of the peripheral devices for personal computers.

Therefore, miniaturization (thinning) and cost reduction of the optical pickup device, which is one of the components of the optical disk device, are also important issues.

In the optical pickup device, since a minute spot of laser light is accurately applied to the recording surface of the optical recording medium,
The objective lens can be finely driven in the tracking direction (direction orthogonal to the tangential direction of the track). The position of the objective lens in the tracking direction (relative position with respect to the reference position) is detected by a lens position sensor provided close to the objective lens. However, this lens position sensor includes a light emitting element and a light receiving element and is a relatively large component, so that there is a problem that a wide space is required. There is also a problem that cost reduction of the optical pickup device is hindered due to parts cost of the lens position sensor and assembly / adjustment cost for disposing the lens position sensor at a predetermined position.

In order to improve these problems, an optical information recording / reproducing apparatus capable of detecting the position of an objective lens without adding a lens position sensor is disclosed in Japanese Patent Laid-Open No. 2001-160225. There is.

In Japanese Patent Laid-Open No. 2001-160225,
A light beam emitted from a light source is divided into a plurality of light beams, a main spot and two sub-spots resulting from the division are applied to an optical recording medium, and a first tracking error signal is generated based on reflected light of the two sub-spots. At the same time, a second tracking error signal is generated based on the reflected light of the main spot. Then, an optical information recording / reproducing apparatus is disclosed which outputs the second tracking error signal as a position signal indicating the position of the objective lens in the tracking direction while performing tracking servo based on the first tracking error signal. This eliminates the need for a space for installing the lens position sensor and the need for an expensive lens position sensor.

[0009]

As the storage capacity of an optical recording medium increases, it is desired to realize higher recording and reproducing speeds. Especially when the recording speed becomes high,
Since it is necessary to form marks (pits) in a shorter time than before, it is necessary to increase the output of the laser light emitted from the light source and increase the amount of light applied to the recording surface of the optical recording medium. .

However, the above-mentioned JP 2001-1
In the optical information recording / reproducing apparatus disclosed in Japanese Patent No. 60225, since the light beam emitted from the light source is divided into a plurality of light beams, the amount of light available for recording and reproduction decreases,
There is an inconvenience that it cannot cope with the increase in recording speed.

The present invention has been made under such circumstances, and the first object thereof is to position the objective lens without splitting the light beam from the light source, and without increasing the size and cost. An object of the present invention is to provide an optical pickup device that can accurately obtain information.

A second object of the present invention is to provide an optical disk device which can perform high-speed access to an optical recording medium accurately and stably without inviting an increase in size and cost. is there.

[0013]

According to a first aspect of the present invention, at least one of recording and reproducing information is performed by irradiating a light spot on a recording surface of an optical recording medium on which spiral or concentric tracks are formed. An optical pickup device used for performing a light source unit; guiding a light beam emitted from the light source unit to a recording surface of the optical recording medium, and receiving a return light beam reflected by the recording surface in a predetermined manner. An optical system including a deflection optical element and an objective lens arranged on an optical path leading to a position; and a drive device for driving the deflection optical element and the objective lens in a tracking direction orthogonal to a tangential direction of the track. First arranged at the light receiving position and outputting a signal including first information
A photodetector; a branching optics arranged on the optical path at a position where the optical axis of the return light beam shifts in response to the movement of the objective lens by the driving device, and which optically branches the return light beam. An optical pickup device comprising: an element; and a second photodetector that receives a light beam branched from the optical path toward the light receiving position by the branch optical element and outputs a signal including second information.

In the present specification, "to be driven in conjunction" means, of course, that the deflection optical element and the objective lens are individually driven in the same direction. It also includes the case where the same drive amount is driven.

According to this, the return light beam reflected by the recording surface of the optical recording medium is received by the first photodetector via the objective lens and the deflection optical element. In order to accurately irradiate the recording surface of the optical recording medium with the light flux emitted from the light source unit, even if the objective lens is driven in the tracking direction by the driving device, the deflection optical element is driven in conjunction with this. , The optical axis of the return light beam with which the first photodetector is irradiated does not change. As a result, the signal output from the first photodetector does not include an offset due to the shift of the objective lens from the reference position in the tracking direction (hereinafter, abbreviated as “shift of objective lens”). . Therefore, for example, if the first information is information related to a track error (hereinafter referred to as “track error information”), the track error signal can be accurately detected based on the signal output from the first photodetector. As a result, the tracking of the objective lens can be performed with high accuracy.

The return light beam is branched by the branch optical element, and the light beam branched from the optical path toward the light receiving position is received by the second photodetector. Here, when the objective lens is moved in the tracking direction by the driving device, the optical axis of the return light beam with which the second photodetector is irradiated is shifted corresponding to the movement of the objective lens. As a result, the signal output from the second photodetector includes an offset due to the shift of the objective lens in the tracking direction. Therefore, for example, information on the position of the objective lens (hereinafter, referred to as “positional information of the objective lens”) can be obtained from the first information and the second information. Further, since the mass production of general-purpose components can be used for the branch optical element and the second photodetector, it is possible to suppress the cost increase to a low level. Furthermore, since the branch optical element and the second photodetector are small in shape, they do not affect the arrangement of other optical elements or the like that form the optical system. Therefore, it is possible to accurately obtain the position information of the objective lens without splitting the light flux from the light source, and without increasing the size and cost.

In this case, various types of branch optical elements are conceivable. For example, as in the optical pickup device described in claim 2, the branch optical element is
The reflectance or the transmittance differs depending on the polarization direction of the incident light, and the light flux emitted from the light source unit may not be branched, but only the return light flux may be branched.
In such a case, the luminous flux emitted from the light source unit is
Since the light amount is irradiated onto the recording surface of the optical recording medium with almost no decrease, the irradiation light amount required for high-speed recording can be secured.

Further, for example, as in the optical pickup device described in claim 3, the branch optical element can be a hologram. In such a case, since the branch optical element can be made small, it is possible to promote miniaturization of the optical pickup device.

In this case, as in the optical pickup device according to the fourth aspect, the optical spot of the return light on the light receiving surface of the hologram has two track patterns caused by the grooves of the tracks formed on the recording surface. And the light receiving surface of the hologram is divided into at least two in the direction of the straight line connecting the centers of the two track patterns. In such a case, since diffracted light is formed in different directions for each divided region, for example, by using two individual light receiving elements as the second light receiving element, the degree of freedom of their arrangement positions increases, and Workability at the time of assembling them is improved. That is, the working cost can be reduced.

In the optical pickup device according to the third and fourth aspects, as in the optical pickup device according to the fifth aspect, the hologram can be a transmission hologram. In such a case, compared with the case of using a reflection type hologram, parts such as a rising mirror are further required, but since strict positioning is not required, workability at the time of assembly is improved, and work is improved. The cost can be reduced.

In the optical pickup device according to any one of claims 3 to 5, like the optical pickup device according to claim 6, the hologram is a polarization hologram having a different diffraction efficiency depending on the polarization direction of incident light. be able to. In such a case, for example, the polarization direction of the light beam emitted from the light source unit is made different from the polarization direction of the return light beam reflected on the recording surface, and the polarization direction of the light beam emitted from the light source unit is Is almost 100
The light flux emitted from the light source unit is designed by designing the hologram so that it has a reflectance or a transmittance of 10% and has an optimum diffraction efficiency for the polarization direction of the return light flux.
It is possible to irradiate the recording surface of the optical recording medium with almost no decrease in the amount of light. That is, the irradiation light amount required for high-speed recording can be secured.

In the optical pickup device according to any one of claims 1 to 6, as in the optical pickup device according to claim 7, the first photodetector and the second photodetector are provided in the light source unit. It may be housed and packaged. In such a case, since the first photodetector and the second photodetector can be arranged in the optimum positions in advance, workability during assembly is improved,
The work cost can be reduced. In addition, further miniaturization can be promoted.

The invention described in claim 8 is an optical disk device for irradiating a light spot on a recording surface of an optical recording medium to record and reproduce information, and the optical pickup device according to claims 1 to 7. An optical disk device including: a processing device that records and reproduces the information by using output signals of the first photodetector and the second photodetector that configure the optical pickup device.

According to this, the processing device can accurately obtain the track error signal and the position information of the objective lens based on the output signal from the optical pickup device according to the first to seventh aspects, and therefore the optical pickup device of the optical pickup device can be obtained. It becomes possible to perform tracking control with high accuracy. Therefore,
As a result, high-speed access to the optical recording medium can be performed accurately and stably. Further, the timing for driving the seek motor can be accurately obtained based on the position information of the objective lens. Further, the miniaturization of the optical pickup device can promote miniaturization of the optical disc device itself and reduction of power consumption.
When used as a portable device, it is easy to carry and can be used for a long time.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION << First Embodiment >> A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a schematic structure of an optical disk device 20 according to the first embodiment, which is equipped with an optical pickup device according to the present invention.

The optical disk device 20 shown in FIG.
Is a spindle motor 22 for rotating the optical disk 15, an optical pickup device 23, a laser control circuit 24, an encoder 25, a motor driver 27, a reproduction signal processing circuit 28, a servo controller 33, a buffer RAM 34, a buffer manager 37, an interface 38. , ROM 39, CPU 40, RAM 41 and the like. It should be noted that the arrows in FIG. 1 show typical flows of signals and information, and do not show all the connection relations of each block.

The optical pickup device 23 irradiates the recording surface of the optical recording medium such as the optical disk 15 on which the spiral or concentric tracks are formed with laser light and receives the reflected light from the recording surface. It is a device.
The configuration of the optical pickup device 23 will be described later in detail.

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 containing reproduction information and a servo signal (focus error). signal,
Track error signal). Then, the reproduction signal processing circuit 28 extracts the address information, the 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 sent to the encoder 25.
Is output to. Further, in the reproduction signal processing circuit 28, R
After performing error correction processing and the like on the F signal, it is stored in the buffer RAM 34 via the buffer manager 37. Further, the focus error signal and the track error signal are transferred from the reproduction signal processing circuit 28 to the servo controller 3
3 is output.

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 motor driver 27.

The buffer manager 37 manages the accumulation of data in the buffer RAM 34 and notifies the CPU 40 when the accumulated data amount reaches a predetermined value.

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.

In the encoder 25, based on an instruction from the CPU 40, the data stored in the buffer RAM 34 is taken out via the buffer manager 37, an error correction code is added, etc., and write data to the optical disk 15 is created. . Then, the encoder 25 outputs the write data to the laser control circuit 24 in synchronization with the synchronization signal from the reproduction signal processing circuit 28 based on the instruction from the CPU 40.

The laser control circuit 24 controls the laser light output from the optical pickup device 23 based on the write data from the encoder 25.

The interface 38 is a bidirectional communication interface with a host (for example, a personal computer), and is an ATAPI (AT Attachment Pack).
et Interface) and SCSI (Small Computer System)
Interface) and other standard interfaces.

The ROM 39 stores a program written in a code readable by the CPU 40.

The CPU 40 controls the operation of each of the above parts according to the program stored in the ROM 39, and temporarily stores the data and the like necessary for the control in the RAM 41.

Next, the configuration of the optical pickup device 23 will be described with reference to FIG.

As shown in FIG. 2A, the optical pickup device 23 includes a semiconductor laser unit 51, a collimator lens 52, a polarization beam splitter 54, and a λ / 4 plate 5.
5, a first reflecting mirror 56 as a deflecting optical element, a light splitter 57 as a branching optical element, an objective lens 60, a condenser lens 58, a prism 85, a second reflecting mirror 86, and a first photodetector. The first photodetector 59, the second photodetector 61 as a second photodetector, and a drive system (focusing actuator, tracking actuator, and seek motor) (all not shown) are provided.
Although illustration is omitted in FIG. 2 (A) for convenience, the objective lens 60 is, as shown in FIG. 2 (B),
It is attached to a predetermined position of the lens holder 70. The lens holder 70 can be finely driven in the tracking direction (X-axis direction) by a tracking actuator (driving device) and in the focus direction (Y-axis direction) by a focusing actuator. further,
The first reflection mirror 56 is fixed to the lens holder 70. That is, since the objective lens 60 and the first reflection mirror 56 are driven in conjunction with each other, the objective lens 60
Is moving in the tracking and focus directions,
The positional relationship between the objective lens 60 and the first reflecting mirror 56 is always constant. Such a configuration is also called a "mirror-integrated actuator".

As shown in FIG. 3, the semiconductor laser unit 51 includes a semiconductor laser chip 51a that emits laser light, a stem 51b that holds the semiconductor laser chip 51a, and laser light emitted from the semiconductor laser chip 51a to the outside. Opening part (hereinafter referred to as "exit window")
Cover 51 for protecting the semiconductor laser chip 51a
It is configured to include c and the like.

The polarization beam splitter 54 has a transmittance of about 100% for an S-polarized light beam and a reflectance of about 100% for a P-polarized light beam.

The λ / 4 plate 55 is used for the semiconductor laser unit 5
The linearly polarized light (S-polarized light) emitted from No. 1 is converted into circularly polarized light, and the reflected light from the optical recording medium is changed from circularly polarized light to linearly polarized light (P
Polarization). The λ / 4 plate 55 may be a film having a phase difference such as crystal, an organic stretched film, an obliquely deposited film of an inorganic substance, and a liquid crystal.

The light splitter 57 has a reflectance of about 100% for an S-polarized light beam and about 70% for a P-polarized light beam.
It has a reflectance of%. The reflectance is not limited to these.

The first light receiver 59 is, for example, as shown in FIG.
As shown in (A), the light receiving surface is divided into four light receiving elements (first four-divided light receiving element 59a, second four-divided light receiving element 59b, third four-divided light receiving element 59c and fourth light receiving element 59c). It is configured to include a 4-division light receiving element 59d). First
4 split light receiving element 59a and second 4 split light receiving element 59b
Have the same rectangular shape with the long side in the Y-axis direction. The third 4-divided light receiving element 59c and the fourth 4-divided light receiving element 59d each have the same rectangular shape with the long side in the X-axis direction. Then, the second four-division light receiving element 59b is arranged on the + X side of the first four-division light receiving element 59a, and the first and second four-division light receiving elements 59a, 59 are provided.
A third 4-division light receiving element 59c and a fourth 4-division light receiving element 59d are arranged on the + Y side of b. 4-division light receiving element 5
Each of 9a to 59d performs photoelectric conversion when receiving light, and outputs a current (current signal) corresponding to the amount of received light to the reproduction signal processing circuit 28 as a photoelectric conversion signal. The first four-divided light receiving element 59a and the second four-divided light receiving element 59b are used for detecting a track error. , 59b) ”. Also, the third
4 split light receiving element 59c and 4th split light receiving element 59d
Is used to detect a focus error, and hereinafter, the light receiving element including the four-divided light receiving elements 59c and 59d is referred to as a "focus error detecting light receiving element (59c, 59d)".

The second light receiver 61 is arranged at a position for receiving the return light beam transmitted through the light splitter 57 in order to detect the shift amount of the objective lens 60 in the tracking direction. The second light receiver 61 is, for example, as shown in FIG.
As shown in (B), a light receiving element whose first light receiving surface is divided into two by a dividing line in the Z-axis direction (first two-divided light receiving element 61
a, a second two-divided light receiving element 61b) is included. Each of the two-divided light receiving elements 61a and 61b performs photoelectric conversion when receiving light, and outputs a current (current signal) corresponding to the amount of received light to the reproduction signal processing circuit 28 as a photoelectric conversion signal.

Returning to FIG. 2, the operation of the optical pickup device 23 configured as described above will be described.

The linearly polarized (S-polarized) light beam emitted from the semiconductor laser unit 51 is made into substantially parallel light by the collimator lens 52 and is incident on the polarization beam splitter 54. Since the polarization beam splitter 54 has a transmittance of about 100% with respect to the S-polarized light flux, most of the incident light flux is transmitted. Then, the optical axis of the light flux is bent in the −Z direction by the first reflecting mirror 56, and the light flux enters the light splitter 57.

In the light splitter 57, since the incident light beam is S-polarized light, most of the incident light beam is reflected and its optical axis is bent in the + Y direction. The light beam deflected by the light splitter 57 is further circularly polarized by the λ / 4 plate 55, and then is condensed as a minute spot on the recording surface of the optical disk 15 via the objective lens 60.

The reflected light reflected by the recording surface of the optical disk 15 (hereinafter referred to as "reflected light RL") becomes circularly polarized light in the opposite direction to the forward path, and is converted into substantially parallel light again by the objective lens 60, and λ / 4. After being converted from circularly polarized light into linearly polarized light (P polarized light) by the plate 55, it is incident on the light splitter 57. Since the reflected light RL here is P-polarized light, about 30% of the reflected light RL passes through the light splitter 57 and is applied to the second light receiver 61 as reflected light RA.

On the other hand, about 70% of the reflected light RL is reflected by the light splitter 57 and is deflected in the + Z direction as the reflected light RB. Then, the reflected light RB has its optical axis bent in the + X direction by the first reflecting mirror 56 and is incident on the polarization beam splitter 54. Since the reflected light RB is a P-polarized light beam, most of it is -Z at the polarization beam splitter 54.
The light is deflected in the direction and enters the condenser lens 58. The reflected light RB transmitted through the condenser lens 58 is branched into two directions by the prism 85, and one reflected light R transmitted through the prism 85.
B1 is a light receiving element (59c, 59c) for focus error detection.
d) is irradiated (see FIG. 3 (B)). Then, the traveling direction of the other reflected light RB2 branched in the −Y direction by the prism 85 is further bent by the second reflecting mirror 86 in the −Z direction, and the light receiving element for track error detection (59a, 59a,
59b) is irradiated (see FIG. 3B).

A light receiving element for detecting a track error (59a,
59b) is arranged at a position where the reflected light RB2 is applied to the central portion of the light receiving surface thereof. Since the positional relationship between the objective lens 60 and the first reflecting mirror 56 is always constant as described above, regardless of the position of the objective lens 60,
The reflected light RB2 is always applied to the central portion of the track error detection light receiving element (59a, 59b).

Focus error detection light receiving element (59
c, 59d) is arranged at a position where the reflected light RB1 is applied to the central portion of the light receiving surface when the recording surface of the optical disk 15 is at the focal position of the objective lens 60 (hereinafter referred to as “focus position”). Has been done. Therefore, for example, in the knife edge method, the recording surface of the optical disk 15 is displaced from the in-focus position,
When so-called focus shift occurs, the light receiving position on the light receiving surface of the focus error detection light receiving element (59c, 59d) shifts according to the magnitude and direction of the focus shift.

The second light receiver 61 is arranged so that the reflected light RA is applied to the central portion of its light receiving surface when the objective lens 60 is at the reference position in the tracking direction. Since the second light receiver 61 is fixed to the housing (not shown) of the optical pickup device 23, when the objective lens 60 is moved in the tracking direction by the tracking actuator, the reflected light RA to the second light receiver 61 is reflected. The optical axis of shifts according to the amount and direction of movement of the objective lens 60. Therefore, when the objective lens 60 moves in the tracking direction from the reference position, the reflected light RA
Is shifted to the first two-divided light receiving element 61a side or the second two-divided light receiving element 61b side and is applied to the second light receiver 61.

The first light receiver 59 is not limited to the four-divided light receiving element, and includes, for example, a first four-divided light receiving element 59a and a second four-divided light receiving element 59b.
It may be composed of a divided light receiving element and a two-divided light receiving element including a third four-divided light receiving element 59c and a fourth four-divided light receiving element 59d. Further, four light receiving elements may be arranged in parallel. Furthermore, the shape and arrangement of each four-division light receiving element
The present invention is not limited to this embodiment. In short, it suffices to obtain the information about the track error and the information about the focus error.

The second light receiver 61 is not limited to the two-divided light receiving element, and for example, two light receiving elements may be arranged in parallel. Furthermore, the shape of the two-divided light receiving element
The present invention is not limited to this embodiment.

Next, the processing operation for detecting the position of the objective lens 60 using the optical disk device 20 provided with the optical pickup device 23 according to the first embodiment will be described. Here, as an example, as shown in FIG. 5A, the objective lens 60 is assumed to be shifted in the + X direction with respect to the reference position indicated by the dotted line.

In this case, the reflected light RB2 is as shown in FIG.
As shown in FIG.
The light is received at the central part of 9a, 59b). On the other hand, the reflected light RA is, as shown in FIG.
Shifts in the + X direction more than when it is in the reference position
It is irradiated to the light receiver 61 of.

The reproduction signal processing circuit 28 detects the track error signal TE based on the following equation (1). Here, S1a is an output signal from the first four-division light receiving element 59a, and S1b is an output signal from the second four-division light receiving element 59b.

TE = S1a-S1b (1)

The reproduction signal processing circuit 28 detects the offset detection signal OS based on the following equation (2). Here, S2a is an output signal from the first two-divided light receiving element 61a, and S2b is an output signal from the second two-divided light receiving element 61b.

OS = S2a-S2b (2)

In the reproduction signal processing circuit 28, the amount of light applied to the light receiving element for track error detection and the second light receiver 61.
Since the amount of light radiated on the track is not necessarily the same, as shown in FIG. 6A as an example, the amplitude of the track error signal TE and the amplitude of the offset detection signal OS have the same amplitude. Adjust at least one of the signal levels.

The reproduced signal processing circuit 28 obtains the offset amount SX due to the shift of the objective lens 60 based on the following equation (3).

SX = OS-TE (3)

Then, in the reproduced signal processing circuit 28, the offset amount SX (FIG. 6A) obtained by the above equation (3) is obtained.
6), the shift amount of the objective lens 60 is obtained based on the correlation between the offset amount and the shift amount of the objective lens 60 which is obtained in advance. The shift amount of the objective lens 60 obtained here is output from the reproduction signal processing circuit 28 to the CPU 40.

Next, the processing operation for recording data on the optical disc 15 using the above-mentioned optical disc device 20 will be briefly described.

Upon receiving the recording request 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 recording speed, and reproduces the fact that the recording request is received from the host. Notify the signal processing circuit 28. When the rotation of the optical disk 15 reaches a predetermined linear velocity, the output signal from the optical pickup device 23 is output to the reproduction signal processing circuit 28. The reproduction signal processing circuit 28 acquires address information based on the output signal from the optical pickup device 23, and the CPU 40
To notify. Further, the reproduction signal processing circuit 28 detects the focus error signal and the track error signal TE based on the output signal from the optical pickup device 23 and outputs them to the servo controller 33. Servo controller 3
Reference numeral 3 drives the focusing actuator and the tracking actuator of the optical pickup device 23 via the motor driver 27 based on the focus error signal and the track error signal TE from the reproduction signal processing circuit 28 to correct the focus deviation and the track deviation. To do.

When the CPU 40 receives the data from the host, the CPU 40 passes the buffer RAM through the buffer manager 37.
34. When the amount of data accumulated in the buffer RAM 34 exceeds a predetermined value, the buffer manager 37
Notifies the CPU 40.

Upon receiving the notification from the buffer manager 37, the CPU 40 instructs the encoder 25 to create write data. Then, the CPU 40 outputs to the motor driver 27, based on the address information from the reproduction signal processing circuit 28, a signal instructing the seek operation of the optical pickup 23 so that the optical pickup 23 is located at a predetermined writing start point. In the servo controller 33, in order to prevent the objective lens 60 from shifting from the reference position in the tracking direction during the seek operation, the tracking actuator is controlled via the motor driver 27 so that the above-described offset amount SX is maintained at 0. To do.

When the CPU 40 determines that the position of the optical pickup device 23 is the writing start point based on the address information from the reproduction signal processing circuit 28, it 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.
The reproduction signal processing circuit 28 is used until the recording process is completed.
As described above, detects the focus error signal and the track error signal TE based on the output signal from the optical pickup device 23, and corrects the focus deviation and the track deviation through the servo controller 33 and the motor driver 27 as needed. Further, the CPU 40 uses the objective lens 6
When the shift amount of 0 becomes larger than a predetermined value, the seek motor is driven and the servo controller 33 is instructed to return the objective lens 60 to the reference position.

Next, the processing operation when the data recorded on the optical disk 15 is reproduced by using the above-mentioned optical disk device 20 will be briefly described.

Upon receiving the reproduction request 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 reproduces the fact that the reproduction request is received from the host. Notify the signal processing circuit 28. When the rotation of the optical disk 15 reaches a predetermined linear velocity, the output signal from the optical pickup device 23 is output to the reproduction signal processing circuit 28. The reproduction signal processing circuit 28 acquires address information based on the output signal from the optical pickup device 23, and the CPU 40
To notify. Further, the reproduction signal processing circuit 28 detects the focus error signal and the track error signal TE based on the output signal from the optical pickup device 23 and outputs them to the servo controller 33. Servo controller 3
Reference numeral 3 drives the focusing actuator and the tracking actuator of the optical pickup device 23 via the motor driver 27 based on the focus error signal and the track error signal TE from the reproduction signal processing circuit 28 to correct the focus deviation and the track deviation. .

Based on the address information from the reproduction signal processing circuit 28, the CPU 40 outputs to the motor driver 27 a signal instructing the seek operation so that the optical pickup device 23 is located at a predetermined reading start point. In the servo controller 33, the objective lens 60 is moved during the seek operation.
In order to prevent the shift from the reference position in the tracking direction, the tracking actuator is controlled via the motor driver 27 so that the above-described offset amount SX maintains 0.

The CPU 40 checks, based on the address information from the reproduction signal processing circuit 28, whether or not it is the reading start point, and when it judges that the position of the optical pickup device 23 is the reading start point, the reproduction signal processing is performed. Notify the circuit 28. Then, in the reproduction signal processing circuit 28,
After detecting the RF signal based on the output signal of the optical pickup device 23 and performing error correction processing and the like, the buffer RAM
34. Until the reproduction process is completed, the reproduction signal processing circuit 28 detects the focus error signal and the track error signal TE based on the output signal from the optical pickup device 23 as described above, and the servo controller 33 and the motor driver 27. The focus deviation and the track deviation are corrected through the. Also, the CPU 40
When the shift amount of the objective lens 60 becomes larger than a predetermined value, drives the seek motor and instructs the servo controller 33 to return the objective lens 60 to the reference position.

The buffer manager 37 uses the buffer RA
When the data accumulated in M34 is prepared as sector data, it is transferred to the host via the interface 38.

As is clear from the above description, in the optical disc device according to this embodiment, the reproduction signal processing circuit 28 and the CPU 40 constitute a processing device.

As described above, according to the optical pickup device of the first embodiment, the return light flux reflected by the recording surface of the optical disc 15 is the objective lens 60 and the first light flux.
It is detected by the first light receiver 59 through the reflection mirror 56. Here, even if the objective lens 60 is driven by the tracking actuator in the tracking direction, since the first reflecting mirror 56 is driven in conjunction with the objective lens 60, the return light flux emitted to the first light receiver 59 is The optical axis does not change. As a result, the signal output from the first light receiver 59 does not include an offset due to the shift of the objective lens 60 in the tracking direction. Therefore, the reproduction signal processing circuit 28 can accurately detect the track error signal based on the signal output from the first light receiver 59.

The return light beam is branched by the optical splitter 57, and the light beam branched from the optical path toward the first light receiver 59 is detected by the second light receiver 61. Here, when the objective lens 60 is moved in the tracking direction by the tracking actuator, the optical axis of the return light beam with which the second light receiver 61 is irradiated shifts corresponding to the movement of the objective lens 60. As a result, the signal output from the second light receiver 61 includes an offset due to the shift of the objective lens 60 in the tracking direction.

Therefore, in the reproduction signal processing circuit 28, the first
The shift amount of the objective lens 60 with respect to the tracking direction can be obtained based on the output signal from the photodetector 59 and the output signal from the second photodetector 61. That is, even in the case of a so-called 1-beam system in which a mirror-integrated actuator is provided and the light beam from the semiconductor laser unit 51 is irradiated onto the recording surface of the optical disk 15 without being split, the conventional lens position sensor is not used. Moreover, it is possible to obtain the position information of the objective lens 60 in the tracking direction. As a result, the size and weight of the optical pickup device 23 can be promoted. Further, since the light splitter 57 and the second light receiver 61 are general-purpose components that are mass-produced, the cost increase can be suppressed to a low level. Furthermore, since the light splitter 57 and the second light receiver 61 are small in shape, they do not affect the arrangement of other optical elements or the like that form the optical system. Accordingly, the light flux from the semiconductor laser unit 51 is applied to the recording surface of the optical disc 15 without being split, and the track error and the position information of the objective lens 60 can be accurately obtained without increasing the size and cost. It will be possible.

Further, in the first embodiment, the optical splitter 5
7 has different reflectance or transmittance depending on the polarization direction of the incident light, and the luminous flux emitted from the semiconductor laser unit 51 is not branched, but only the returning luminous flux is branched. Therefore, the luminous flux emitted from the semiconductor laser unit 51 is
The recording surface of the optical disc 15 is irradiated with the light amount hardly decreasing, and the irradiation light amount required for high-speed recording can be secured.

Further, according to the optical disk device of the present embodiment, the tracking error signal TE and the objective lens 6 are
Since the position information of 0 can be obtained with high accuracy, accurate information recording and reproduction can be stably performed. Further, since the light flux emitted from the light source can be applied to the recording surface of the optical disc 15 without being split,
High-speed access to the optical disk 15 can be stably performed. Further, the miniaturization of the optical pickup device 23 can promote miniaturization of the optical disc device itself and reduction of power consumption. For example, when the optical pickup device 23 is used as a portable device, it is easy to carry and can be used for a long time. Is possible.

In the first embodiment, the case where the arithmetic processing of the expressions (1) to (3) is performed by the reproduction signal processing circuit 28 has been described, but the present invention is not limited to this, and the optical pickup is not limited to this. An arithmetic circuit for performing at least one of the arithmetic operations of the above equations (1) to (3) may be added to the device 23. As a result, the reproduction signal processing circuit 28 can be simplified, and wiring work at the time of assembly can be facilitated, and workability can be improved and work cost can be reduced.

In the first embodiment, the light splitter 57 has a reflectance of about 100% for the S-polarized light beam and a reflectance of about 70% for the P-polarized light beam. Although the case where it has is explained, each reflectance is not limited to these.

Further, in the first embodiment described above, the case where the light splitter 57 splits only the return light flux by utilizing the difference in the polarization direction has been described, but the present invention is not limited to this. Alternatively, for example, a half mirror may be used to split the light.

<< Second Embodiment >> Next, a second embodiment of the present invention will be described with reference to FIGS.

In the second embodiment, as shown in FIG. 7, instead of the above-mentioned optical splitter 57, the hologram 6 is used.
The feature is that 2 is used. In addition, the configurations of the optical pickup device and the optical disc device are the same as those of the first embodiment described above. Therefore, in the following description, differences from the first embodiment will be mainly described, and the same reference numerals will be used for the same or equivalent components as those in the above-described first embodiment to simplify the description. It shall be omitted.

The hologram 62 is shown in FIG. 8A as an example.
As shown in FIG. 2, the first divisional hologram 62a and the second divisional hologram 62a are divided into two in the tracking direction.
b) has been done. The hologram 62 is a reflection type polarization hologram in which a grating is formed by etching or the like on a thin retardation film made of an organic stretched film. Hologram 6
No. 2 is designed so that the reflectance with respect to the S-polarized light flux is about 100% and the diffraction efficiency with respect to the P-polarized light flux is about 20%. Note that this diffraction efficiency is an example, and the diffraction efficiency can be arbitrarily changed by changing the depth and shape of the grating of the polarization hologram. Therefore, when a P-polarized light beam is incident on the hologram 62, the incident light beam is reflected light (so-called zero-order light, hereinafter referred to as “hologram”) at the central portion of the light receiving surface, as shown in FIG. 8B as an example. Also referred to as "reflected light RC") and diffracted light at the first partial hologram 62a (hereinafter referred to as "first diffracted light RD").
1 ”) and the diffracted light at the second partial hologram 62b (hereinafter, also referred to as“ second diffracted light RD2 ”). In the following, the hologram reflected light RC, the first diffracted light RD1 and the second diffracted light RD2 are also referred to as “hologram branched light”.

The second embodiment of the first embodiment described above.
In place of the light receiving element 61, the third light receiver 63 for receiving the first diffracted light RD1 is arranged adjacent to the −X side of the first light receiver 59, and the third light receiver 63 of the first light receiver 59 is provided. A fourth light receiver 64 for receiving the second diffracted light RD2 is arranged adjacent to the + X side. Then, the third light receiver 63 and the fourth light receiver 64 perform photoelectric conversion, and output a current (current signal) corresponding to the amount of received light to the reproduction signal processing circuit 28 as a photoelectric conversion signal. The hologram reflected light RC is applied to the first light receiver 59. In addition,
In the second embodiment, the first light receiver 59, the third light receiver 63, and the fourth light receiver 64 are provided on the same substrate, but the present invention is not limited to this, and each is on a separate substrate. May be provided in.

Returning to FIG. 7, the operation of the optical pickup device 23 of the second embodiment will be described.

The linearly polarized (S-polarized) light flux emitted from the semiconductor laser unit 51 is made into substantially parallel light by the collimator lens 52, and the light flux transmitted through the polarization beam splitter 54 is reflected by the first reflection mirror 56. The optical axis is bent in the Z direction and is incident on the hologram 62. Since this light flux is S-polarized light, its optical axis is bent in the + Y direction by the hologram 62 and is circularly polarized by the λ / 4 plate 55, and then it is minutely recorded on the recording surface of the optical disk 15 via the objective lens 60. It is collected as a spot.

The reflected light RL reflected by the recording surface of the optical disk 15 becomes circularly polarized light in the opposite direction to the outward path, is made to be substantially parallel light again by the objective lens 60, and is circularly polarized from linearly polarized light by the λ / 4 plate 55. After being converted into (P polarized light), the hologram 6
It is incident on 2. Since the reflected light RL is P-polarized light, it is split into the hologram reflected light RC, the first diffracted light RD1 and the second diffracted light RD2 in the hologram 62. These hologram branched lights are + X at the first reflecting mirror 56.
Then, the polarized light is deflected in the −Z direction by the polarization beam splitter 54 and is incident on the condenser lens 58. The hologram branched light transmitted through the condenser lens 58 is branched in two directions by the prism 85, and one hologram branched light branched in the −Y direction by the prism 85 is further moved by the second reflection mirror 86 in the −Z direction. The traveling direction is bent, and the hologram reflection light RC is received by the track error detection light receiving elements (59a, 59b), and the first diffracted light R is received by the third light receiver 63.
D1 irradiates the fourth light receiver 64 with the second diffracted light RD2. Then, the hologram reflected light RC of the other hologram branched light transmitted through the prism 85 is applied to the focus error detection light receiving elements (59c, 59d).

Next, the processing operation for detecting the position of the objective lens 60 using the optical disk device equipped with the optical pickup device according to the second embodiment will be described. Note that, here, as an example, it is assumed that the objective lens 60 is shifted in the + X direction with respect to the reference position, as in the first embodiment.

In this case, the reflected light RL is shifted in the + X direction more than when the objective lens 60 is at the reference position, as shown in FIG.
Is irradiated. Therefore, as shown in FIG. 8D as an example, the first diffracted light RD1 is changed to the second diffracted light RD2.
Will be smaller than.

The hologram error reflected light RC is received at the central portion of the track error detecting light receiving element (59a, 59b).

The reproduction signal processing circuit 28 detects the track error signal TE based on the above equation (1), as in the first embodiment.

The reproduction signal processing circuit 28 detects the offset detection signal OS based on the following equation (4). Here, S3 is an output signal from the third light receiving element 63,
S4 is an output signal from the fourth light receiving element 64.

OS = S3-S4 (4)

The reproduction signal processing circuit 28 adjusts at least one of the signal levels so that the amplitude of the track error signal TE and the amplitude of the offset detection signal OS have the same amplitude.

In the reproduction signal processing circuit 28, as in the first embodiment, the objective lens 60 is calculated based on the equation (3).
The offset amount SX due to the shift is calculated.

Then, in the reproduction signal processing circuit 28, the first
Similar to the embodiment described above, the shift of the objective lens 60 is performed based on the offset amount SX obtained by the above equation (3) and the previously obtained correlation between the offset amount and the shift amount of the objective lens 60. Find the amount. The shift amount of the objective lens 60 obtained here is output from the reproduction signal processing circuit 28 to the CPU 40.

Further, in the optical disk device 20, recording of data on the optical disk 15 and reproduction of data recorded on the optical disk 15 are performed in the same manner as in the first embodiment.

As described above, according to the optical pickup device of the second embodiment, since the hologram is used as the branching optical element, the branching optical element can be downsized, and the optical pickup device It becomes possible to promote miniaturization and thinning. Further, when the reflection type hologram is used, it is not necessary to dispose the light receiving element for detecting the shift amount of the objective lens 60 in the tracking direction below the hologram (−Y side).
It is possible to promote the thinning of the optical pickup device.

Further, in the second embodiment, since the light receiving surface of the hologram 62 is divided into two in the tracking direction, diffracted light is formed in different directions for each divided area. Therefore, the degree of freedom in the arrangement positions of the third light receiving element 63 and the fourth light receiving element 64 is increased, and the workability at the time of assembling them is improved. That is, the working cost can be reduced.

Furthermore, in the second embodiment, as the hologram 62, a polarization hologram whose diffraction efficiency differs depending on the polarization direction of the incident light is used. The hologram 62 is designed to have a reflectance of about 100% with respect to the polarization direction of the light flux emitted from the light source and a diffraction efficiency of about 20% with respect to the polarization direction of the return light flux. Therefore, the light flux emitted from the light source irradiates the recording surface of the optical disc 15 with almost no decrease in the amount of light. That is, the irradiation light amount required for high-speed recording can be secured. This hologram can be manufactured by processing a material having birefringence into a lattice shape, or by processing a lattice having a pitch smaller than the wavelength. As a material having birefringence, there are LiNbO ₃ crystal and liquid crystal, but in the second embodiment, as an example, a stretched film of a transparent organic material such as thin film birefringent polyimide or PET is used. There is. For polyimide and PET, Δn
Since it has a birefringence of about 0.06 to 0.1 and a refractive index of about 1.6, it is possible to use an inexpensive overcoat material after the lattice processing, and it is easy to reduce the cost. Is.

Further, according to the optical disk device of the second embodiment, the tracking error signal TE and the position information of the objective lens can be obtained with high accuracy, and therefore the same effect as that of the first embodiment can be obtained. You can

In the second embodiment, the hologram 62 obtains the diffracted light from all of the incident light, but not limited to this, the diffracted light may be obtained from a part of the incident light. In this case, as shown in FIGS. 9 (A) and 9 (B) as an example, the branch elements 62 ′ and 62 ″ in which the hologram is formed only in a part of the light receiving region are provided as holograms 6.
It may be used instead of 2. That is, the objective lens 60
The S / N ratio can be improved by forming the hologram at the position where the signal change due to the shift of 1 is significant.

In the second embodiment, the case where the reflection type hologram 62 is used has been described, but the present invention is not limited to this, and a transmission type hologram may be used. In this case, as shown in FIG. 10, a rising mirror 65 for guiding the light flux from the light source reflected by the first reflecting mirror 56 to the objective lens 60 is further required. Then, the transmissive hologram 66 is placed on the rising mirror 65 and the λ / 4 plate 55.
Or the rising mirror 65 and the first reflecting mirror 56
If the reflective hologram 62 is used, it is possible to obtain the same effect as when the reflective hologram 62 is used. When the transmission type hologram 66 is used, the function of the rising mirror and the function of branching the returning light beam are separated, so that the rising mirror 65 is moved so that the light from the light source can be vertically incident on the objective lens 60. Then, the hologram 66 can be aligned so that the return light beam is optimally branched. That is, while the number of parts is increased, adjustment is facilitated and a good signal with a small offset can be obtained.

Further, in the second embodiment, the case where the semiconductor laser chip 51a and the light receivers 59, 63 and 64 are separately arranged has been described, but the present invention is not limited to this. . For example, as shown in FIG. 11, the semiconductor laser chip 51a and the light receivers 59 and 6 are provided.
You may integrate 3 and 64. That is, by disposing the substrate 67 on which the first light receiver 59, the third light receiver 63, and the fourth light receiver 64 are mounted in the semiconductor laser unit 51, further size reduction and cost reduction can be achieved. It can be realized. Instead of the hologram 62, as shown in FIG. 11, a transmissive hologram 75 may be arranged in the vicinity of the exit window. In this case, naturally, the raising mirror for deflecting the light beam is arranged at the position where the hologram 62 is arranged. The branch elements corresponding to the prism 85 and the second reflecting mirror 86 are omitted in FIG. 11.

In the second embodiment, the case where the polarization hologram is used as the hologram has been described, but a non-polarization hologram may be used. In this case, if the beam splitter for splitting the return light is not a polarization beam splitter, the λ / 4 plate 55 is unnecessary.

In the second embodiment, the case where the reproduction signal processing circuit 28 performs the arithmetic processing of the expressions (1), (3) and (4) has been described, but the present invention is not limited to this. In the optical pickup device 23, the above (1),
An arithmetic circuit for performing at least one of the arithmetic processes of the expressions (3) and (4) may be added. As a result, the reproduction signal processing circuit 28 can be simplified, and wiring work at the time of assembly can be facilitated, and workability can be improved and work cost can be reduced.

In each of the above embodiments, the polarization beam splitter 54 is used to split the return light.
Not limited to this, for example, a beam splitter using a half mirror may be used.

In each of the above embodiments, the case where the light beam emitted from the light source is S-polarized light is described, but the present invention is not limited to this and may be P-polarized light. However, in this case, in the description of each of the above embodiments, S-polarized light is referred to as P-polarized light, and P-polarized light is referred to as P-polarized light.
It is necessary to read polarized light as S-polarized light.

[0113]

As described above, according to the optical pickup device of the present invention, the information regarding the position of the objective lens can be obtained without splitting the luminous flux from the light source, and without increasing the size and cost. Can be detected with high accuracy.

Further, according to the optical disk device of the present invention, there is an effect that high-speed access to the optical recording medium can be performed accurately and stably without causing an increase in size and cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical disc device according to a first embodiment of the present invention.

2A is a diagram showing a schematic configuration of an optical system in the optical pickup device of FIG. 1, and FIG. 2B is a diagram for explaining a lens holder.

FIG. 3 is a diagram for explaining the semiconductor laser unit in FIG. 2 (A).

FIG. 4 (A) and FIG. 4 (B) are diagrams for explaining an example of a configuration of a first light receiving element.

5A to 5C are diagrams for explaining shift detection of an objective lens, respectively.

FIG. 6A is a diagram for explaining a method of obtaining an offset amount based on output signals from the first photoreceiver and the second photoreceiver, and FIG. It is a figure for demonstrating the relationship between an offset amount and the shift amount of an objective lens.

FIG. 7 is a schematic configuration diagram for explaining a second embodiment of an optical pickup device according to the present invention.

8A to 8C are diagrams for explaining the configuration of the hologram, and FIG. 8D illustrates reflected light and diffracted light with which the light receiving element is irradiated. FIG.

9 (A) and 9 (B) are diagrams for explaining a branched optical element in which a hologram is formed only in a part thereof.

FIG. 10 is a diagram showing a schematic configuration of an optical system in an optical pickup device when a transmissive hologram is used.

FIG. 11 is a diagram for explaining an example of packaging of a light receiving element and a semiconductor laser.

[Explanation of symbols]

15 ... Optical disc (optical recording medium), 20 ... Optical disc device, 23 ... Optical pickup device, 40 ... CPU (processing device), 51 ... Semiconductor laser unit (light source unit),
55 ... Hologram (branching optical element), 57 ... Optical splitter (branching optical element), 59 ... First light receiving element (first photodetector), 60 ... Objective lens, 61 ... Second light receiving element (first) 2 photo detectors).

Continued front page    F-term (reference) 5D118 AA01 AA13 AA14 BA01 CD02                       CD03 DA20 DC03                 5D119 AA01 AA10 AA24 AA28 AA43                       BA01 EA02 EA03 JA25 KA04                 5D789 AA01 AA10 AA24 AA28 AA43                       BA01 EA02 EA03 JA25 KA04

Claims (8)

[Claims] 1. A light spot is irradiated onto a recording surface of an optical recording medium on which spiral or concentric tracks are formed,
An optical pickup device used for at least one of recording and reproducing information, comprising: a light source unit; a light beam emitted from the light source unit, guided to a recording surface of the optical recording medium, and reflected by the recording surface. An optical system including a deflection optical element and an objective lens arranged on an optical path for guiding the returned light flux to a predetermined light receiving position; and the deflection optical element and the objective lens in a tracking direction orthogonal to a tangential direction of the track. A driving device which is driven in conjunction; a first photodetector which is arranged at the light receiving position and which outputs a signal including first information; and a movement of the objective lens by the driving device on the optical path. And a branching optical element that is arranged at a position where the optical axis of the return light beam is shifted and optically branches the return light beam; A second photodetector that receives a light beam branched from an optical path toward the position and outputs a signal including second information; 2. The branching optical element has a reflectance or a transmittance that varies depending on a polarization direction of incident light, so that a light beam emitted from the light source unit is not branched and only a return light beam is branched. The optical pickup device according to claim 1. 3. The optical pickup device according to claim 1, wherein the branch optical element is a hologram. 4. The light spot of the return light on the light receiving surface of the hologram has two track patterns caused by the grooves of the tracks formed on the recording surface, and the light receiving surface of the hologram is at least the light receiving surface of the hologram. 4. The optical pickup device according to claim 3, wherein the optical pickup device is divided into two in a straight line direction connecting the centers of one track pattern. 5. The optical pickup device according to claim 3, wherein the hologram is a transmissive hologram. 6. The optical pickup device according to claim 3, wherein the hologram is a polarization hologram having a different diffraction efficiency depending on the polarization direction of incident light. 7. The first photodetector and the second photodetector are housed in the light source unit and packaged. The optical pickup device described. 8. An optical disc device for irradiating a light spot on a recording surface of an optical recording medium to record and reproduce information, the optical pickup device according to claim 1; and the optical pickup device. The first photodetector and the second
An optical disk device comprising: a processing device that records and reproduces the information by using the output signal of the photodetector.