JP2006294075A - Optical pickup, optical recording device, optical reproducing device, and optical recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup capable of completely eliminating a stray light generated when a multilayer information recording medium is subjected to recording/reproducing, an optical recording device, an optical reproducing device, and an optical recording/reproducing device. <P>SOLUTION: In a section obtained by viewing a detection optical system from a track direction, when a reading light is converged in the m-th recording layer of a recording medium, a front light shielding means 11 is arranged between the convergence spot fm of its reflected light Lm by a detection convergent lens 6 and the convergent spot fm+1 of a stray luminous flux from an m+1-th layer, a rear light shielding means 12 is arranged between the convergence spot fm and the convergent spot fm-1 of a stray luminous flux from an m-1-th layer, and only a signal luminous flux Lm reaches a light receiving element 8 through both light shielding means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical pickup mounted on a recording / reproducing apparatus for recording / reproducing a multilayer information recording medium (double-layer information recording medium or the like), and is a technology applicable to a multilayer disk inspection apparatus / evaluation apparatus.

FIG. 13 is a diagram for explaining a general optical pickup.
In the figure, reference numeral 1 is a light source, 2 is a coupling lens, 3 is a detection / separating means, 4 is an objective lens, 5 is an information recording medium, 6 is a detection lens, 7 is a diffraction grating, and 8 is a light receiving element.
The optical pickup includes a light source 1 that emits light for reproducing information recorded on the information recording medium 5, a coupling lens 2 that converts a divergent light beam of the light source 1 into a substantially parallel light beam, a light beam that travels from the light source 1 to the information recording medium 5, and information. Detection / separation means 3 for separating the light beam reflected from the recording medium 5, an objective lens 4 for condensing the light beam on the information recording medium 5, and a light beam reflected by the signal layer of the information recording medium 5 on the light receiving element 8. Detection lens 6 for illuminating, diffraction grating 7 for generating a focus error signal and a track error signal necessary for keeping the focus direction and track direction position of the information recording medium 5 and objective lens 4 constant, information recording A light receiving element 8 for obtaining signal information of the medium 5 is provided. The objective lens is mounted on an actuator that can be driven in the optical axis direction in order to focus the spot on the signal information surface of the information recording medium.
The light beam emitted from the light source 1 becomes substantially parallel light by the coupling lens 2, passes through the detection / separation means 3, and forms a minute spot on the information recording surface of the information recording medium 5 by the objective lens 4. The light beam reflected by the information recording medium 5 becomes substantially parallel light again by the objective lens 4, is reflected by the detection / separation means 3, becomes convergent light by the condenser lens 6, branches the light beam by the diffraction grating 7, and divides each light beam. It is detected on the light receiving surface of the light receiving element 8.
In general, an optical system that travels from a light source to an information recording medium is called an illumination optical system (outward path), and an optical system in which a light beam reflected by the information recording medium travels to a light receiving element is called a detection optical system (return path). Call it.

FIG. 14 is a diagram for explaining the optical unit.
FIG. 15 is a diagram for explaining a diffraction grating.
In recent years, an optical unit called a light unit, a light receiving element, and an optical unit in which a region-divided diffraction grating is integrated to generate various signals has appeared as a technology for downsizing an optical pickup.
The optical unit includes a light source 1, a divided light receiving element 8, and a diffraction grating 7 divided into regions.
The divergent light emitted from the light source 1 passes through the diffraction grating 7 and travels to a coupling lens (not shown) provided in the optical pickup. The light beam reflected by the information recording medium passes through the coupling lens again and enters the diffraction grating 7 as convergent light. The diffraction grating 7 is divided into regions with respect to an incident light beam, and the divided light receiving element 8 receives the light beam divided in each region. As shown in FIG. 15, a general diffraction grating is divided into three, and a focus error signal is obtained (by the knife edge method) by detecting light diffracted in the region AB with a two-divided light receiving element. A track error signal is obtained by individually receiving the lights diffracted by C and D, respectively.

FIG. 16 is a block diagram for explaining a recording or reproducing or recording / reproducing apparatus.
In the figure, reference numeral 20 denotes an optical disk device, 22 denotes a spindle motor, 23 denotes an optical pickup device, 24 denotes a laser control circuit, 25 denotes an encoder, 27 denotes a motor driver, 28 denotes a reproduction signal processing circuit, 33 denotes a servo controller, and 34 denotes a buffer. RAM, 37 is a buffer manager, 38 is an interface, 39 is a ROM, 40 is a CPU, and 41 is a RAM.
The arrows in the figure indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block.
The optical pickup device 23 is a device for irradiating a recording surface on which a spiral or concentric track of an optical disk (information recording medium) 5 is formed with laser light and receiving reflected light from the recording surface. . The reproduction signal processing circuit 28 converts a current signal that is an output signal of the optical pickup device 23 into a voltage signal, and based on the voltage signal, a wobble signal, a reproduction signal, a servo signal (focus error signal, track error signal), etc. Is detected. Then, the reproduction signal processing circuit 28 extracts address information, a synchronization signal, and the like from the wobble signal. The address information extracted here is output to the CPU 40, and the synchronization signal is output to the encoder 25. Further, the reproduction signal processing circuit 28 performs error correction processing or the like on the reproduction signal and then stores it in the buffer RAM 34 via the buffer manager 37.

The servo signal is output from the reproduction signal processing circuit 28 to the servo controller 33. 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 input / output of data to / from 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.
The encoder 25 takes out the data stored in the buffer RAM 34 through the buffer manager 37 based on an instruction from the CPU 40, adds an error correction code, and creates write data to the optical disc 5. The encoder 25 outputs write data to the laser control circuit 24 in synchronization with the synchronization signal from the reproduction signal processing circuit 28 based on an instruction from the CPU 40. 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. Note that, in the laser control circuit 24, one of two light sources of the optical pickup device 23, which will be described later, is controlled based on an instruction from the CPU 40. The interface 38 is a bidirectional communication interface with a host (for example, a personal computer), and conforms to standard interfaces such as ATAPI (AT Attachment Packet Interface) and USB (Universal Serial Bus). The ROM 39 stores a program written in a code that can be decoded by the CPU 40. The CPU 40 controls the operation of each unit in accordance with a program stored in the ROM 39 and temporarily stores data necessary for control in the RAM 41.

FIG. 17 is a diagram for explaining the structure of the double-layer information recording medium.
In the figure, reference numeral 51 denotes an L0 substrate, 52 denotes a semi-transmissive film, 53 denotes an intermediate layer, 54 denotes a metal reflection film, and 55 denotes an L1 substrate.
As means for realizing an increase in capacity of an information recording medium, there is a multilayer information recording medium. A typical multi-layer information recording medium is a double-layer information recording medium.
The double-layer information recording medium 5 is formed by sequentially laminating an L0 substrate 51, a semi-transmissive film (L0 layer) 52, an intermediate layer 53, a metal reflective film (L1 layer) 54, and an L1 substrate 55 from the light incident side. is there. The signal information is recorded as a pattern shape on the surface of the L0 layer 52 or the surface of the L1 layer 54. The L0 substrate 51 and the L1 substrate 55 are generally made of polycarbonate. The intermediate layer 53 is made of ultraviolet or thermosetting resin. The semi-transmissive film 52 is made of silicon, silver, aluminum, or the like. For the metal reflective film 54, silver or aluminum is mainly used.
The double-layer information recording medium is now mainstream in the DVD video format, and many double-layer information recording media that record various movies and the like are on the market.

FIG. 18 is a diagram for explaining the reproduction status of the double-layer information recording medium. FIG. 4A is an optical path diagram when reading record information written on the L0 substrate, and FIG. 4B is an optical path diagram when reading record information written on the L1 substrate.
In FIG. 6A, a minute spot is formed on the L0 layer 52 by separating the distance between the surface of the L0 substrate 51 and the objective lens 4 as indicated by a solid line. When the signal information of the L1 layer 54 is reproduced, a minute spot is formed on the L1 layer 54 by reducing the distance between the surface of the L0 substrate 51 and the objective lens 4 as shown by the solid line in FIG. Both signal beams (solid lines) reflected by the L0 layer 52 and the L1 layer 54 become parallel beams when transmitted through the objective lens 4. If the position of the detection lens 6 is fixed, it is collected and detected by the same light receiving surface 8. can do.

FIG. 19 is a diagram showing a result of observing how the jitter, which is the reproduction signal of the L0 layer, deteriorates when the intermediate layer thickness is narrowed under the condition of the dual-layer DVD.
When the L0 layer is being reproduced, stray light is generated from the L1 layer 54 as indicated by the dotted line in FIG. Further, when the L1 layer 54 is being reproduced, stray light is generated from the L0 layer 52 as indicated by the dotted line in FIG. A part of this stray light overlaps the light beam reflected by the signal layer of the information recording medium 5 and is detected by the light receiving element 8.
This stray light is generally detected as an offset to various signals. The generation principle is discussed in detail in Non-Patent Document 1.
Further, when the thickness of the intermediate layer 53 is reduced, the signal light beam and the stray light light beam interfere with each other in front of the light receiving element 8 and become a noise component with respect to the focus error signal, the track error signal, and the disk reproduction signal (jitter). For example, as shown in FIG. 19, when the jitter which is the reproduction signal of the L0 layer is observed, it can be seen that when the thickness of the intermediate layer 53 is made thinner than 30 μm, the jitter is remarkably deteriorated.
In general, such a phenomenon is called crosstalk in a two-layer information recording medium. For this reason, when the intermediate layer 53 of the double-layer information recording medium is thinned, it is necessary to remove and reduce stray light in the optical pickup.
In a multilayer information recording medium, stray light from all layers other than the layer reproducing the signal is generated, and a large crosstalk is generated.

By separating the signal beam and stray light beam into 0th order and ± 1st order light with a diffraction grating arranged in the detection optical system, detecting stray light from multiple layers with different light receiving elements, and differentially calculating the signal light beam and the stray light beam, A technique for removing an offset due to a stray light beam is known (for example, see Patent Document 1).
However, in such a configuration, the light beam separated by the diffraction grating is diffracted not only by stray light but also by signal light, so that the signal component decreases. Furthermore, the fluctuation of the light quantity due to the interference between the signal light beam and the stray light light beam in front of the light receiving surface cannot be removed, and the intensity of the signal light fluctuates.
A technique for reducing the influence of stray light by a condensing lens and a pinhole arranged in a detection optical system is known (for example, see Patent Document 2). However, in this optical system, since the central component of the stray light with the highest intensity distribution passes through the pinhole and is detected by the light receiving element, it is not a complete countermeasure against stray light. In general, since the objective lens is driven in the track direction, an optical axis shift occurs. At this time, the signal light is kicked at the position of the pinhole, and the signal light intensity itself fluctuates.

JP 2001-273640 A JP 2003-323736 A JP 2001-273640 A ODS2003 “Analyses for Design of Drives and Disks for Dual-layer Phase Change Optical Disks”

  In view of the above problems, the present invention proposes an optical pickup capable of completely removing stray light generated when recording / reproducing a multilayer information recording medium. Further, the present invention proposes an optical pickup capable of completely removing stray light with a simple configuration even in recording / reproducing of a double-layer information recording medium.

According to the first aspect of the present invention, a multi-layer information recording has a light source, a collimating lens, a detection / separating means, an objective lens, a detection optical system, and a light receiving element, and information is recorded on layers having different substrate thicknesses. In an optical pickup for recording, reproducing, or recording / reproducing a medium (hereinafter simply referred to as a recording medium), the detection optical system for detecting a light beam reflected by the recording medium causes the light beam to be condensed on the light receiving element. And the condensing point of the stray light beam Lm + 1 reflected by the (m + 1) th layer is fm, and the condensing point of the signal beam Lm reflected by the mth layer on which the light beam is condensed on the recording medium Fm + 1, where m-1 is the condensing point of the stray light beam Lm-1 reflected by the (m-1) th layer, the track of the recording medium between the condensing point fm and the condensing point fm + 1. Front in cross section viewed from the direction A front light shielding means for shielding one side from the optical axis of the light collecting means, a rear light shielding means for shielding the other side from the optical axis between the light focusing point fm and the light focusing point fm-1, It is provided with.
According to the second aspect of the present invention, a multi-layer information recording has a light source, a collimating lens, a detection / separating means, an objective lens, a detection optical system, and a light receiving element, and information is recorded on layers having different substrate thicknesses. In an optical pickup for recording, reproducing, or recording / reproducing a medium (hereinafter simply referred to as a recording medium), the detection optical system for detecting a light beam reflected by the recording medium causes the light beam to be condensed on the light receiving element. And the condensing point of the stray light beam Lm + 1 reflected by the (m + 1) th layer is fm, and the condensing point of the signal beam Lm reflected by the mth layer on which the light beam is condensed on the recording medium Fm + 1, where the condensing point of the stray light beam Lm-1 reflected by the (m-1) th layer is fm-1, the track of the recording medium is closer to the condensing means than the condensing point fm + 1. In the cross section seen from the direction The stray light beam between the condensing point fm and the condensing point fm + 1 for each of the branched light beams. A front light shielding means disposed on one side of the optical axis for shielding Lm + 1 and the optical axis for shielding the stray light beam Lm-1 between the condensing point fm and the condensing point fm-1. And a rear shading means arranged on the other side.

According to a third aspect of the present invention, a multi-layer information recording has a light source, a collimating lens, a detection / separating means, an objective lens, a detection optical system, and a light receiving element, and information is recorded on layers having different substrate thicknesses. In an optical pickup for recording, reproducing, or recording / reproducing a medium (hereinafter simply referred to as a recording medium), the detection optical system for detecting a light beam reflected by the recording medium causes the light beam to be condensed on the light receiving element. And the condensing point of the stray light beam Lm + 1 reflected by the (m + 1) th layer is fm, and the condensing point of the signal beam Lm reflected by the mth layer on which the light beam is condensed on the recording medium Fm + 1, where m-1 is the condensing point of the stray light beam Lm-1 reflected by the (m-1) th layer, the light beam is recorded between the condensing point fm and the condensing point fm. In the cross section of the medium viewed from the track direction The stray light beam Lm + 1 between the light condensing point fm and the light condensing point fm-1 for each branched light beam And a light shielding means arranged on one side from the optical axis for shielding the stray light beam Lm-1.
According to a fourth aspect of the present invention, in the optical pickup according to the third aspect, the light beam branching unit is configured such that two optical wedges are integrated so as to be vertically symmetrical by abutting the thinner one. It is characterized by being.

According to a fifth aspect of the present invention, in the optical pickup according to the third aspect, the light beam branching unit is configured such that two optical wedges are integrated so as to be vertically symmetrical by abutting the thicker one. It is characterized by being.
According to a sixth aspect of the present invention, in the optical pickup according to the fifth aspect, the light shielding means provided for each of the branched light beams is integrated.

According to a seventh aspect of the present invention, in the optical pickup according to any one of the fourth to sixth aspects, the optical wedge and the light shielding means are integrated.
According to an eighth aspect of the present invention, in the optical pickup according to the third aspect, the beam splitting means is a blazed diffraction grating in which each region has a different diffraction direction in the cross section.
According to a ninth aspect of the present invention, in the optical pickup according to the eighth aspect, the blazed diffraction grating is characterized in that a grating angle is set so that light beams diffracted in each region intersect each other.

According to a tenth aspect of the present invention, in the optical pickup according to the ninth aspect, the light shielding means provided for each branched light beam is integrated.
In the invention according to claim 11, in the optical pickup according to any one of claims 8 to 10, a light source is disposed at a position of a condensing point fm to be generated when the diffraction grating is not provided. The light source emits linearly polarized light in a direction not diffracted by the blazed diffraction grating.
According to a twelfth aspect of the present invention, in the optical pickup according to any one of the eighth to eleventh aspects, the diffraction grating and the light shielding means are integrated.
According to a thirteenth aspect of the present invention, in the optical pickup according to any one of the eighth to eleventh aspects, the diffraction grating, the light shielding unit, the light source, and the light receiving element are integrated as an optical unit. It is characterized by.
According to a fourteenth aspect of the present invention, in the optical pickup according to the first aspect, a second condenser lens is provided in front of the light receiving element, and at least a part of the light receiving element is divided by a line parallel to the track direction. A two-divided light receiving element is used.
According to a fifteenth aspect of the present invention, in the optical pickup according to the first aspect, at least a part of the light receiving element is a two-divided light receiving element divided by a line perpendicular to the track direction.
According to a sixteenth aspect of the present invention, in the optical pickup according to any one of the second to thirteenth aspects, the second condensing lens is arranged before the light receiving element for one of the light beams branched by the light beam branching unit. And a two-part light receiving element obtained by dividing the collected signal light beam by a line parallel to the track direction.
According to a seventeenth aspect of the present invention, in the optical pickup according to any one of the second to thirteenth aspects, a light beam in which a second condenser lens is not provided in front of the light receiving element branched by the light beam branching unit is detected. The light receiving element is divided into at least two by a line parallel to the track direction.
According to an eighteenth aspect of the present invention, in the optical pickup according to any one of the second to thirteenth aspects, the second condensing lens is arranged before the light receiving element with respect to one light beam branched by the light beam branching unit. The light-receiving element for detecting the other light beam is divided into at least two parts by a line parallel to the track direction. Features.
According to a nineteenth aspect of the present invention, there is provided an optical recording apparatus including the optical pickup according to any one of the first to eighteenth aspects.
According to a twentieth aspect of the present invention, there is provided an optical reproducing apparatus including the optical pickup according to any one of the first to eighteenth aspects.
According to a twenty-first aspect of the present invention, there is provided an optical recording / reproducing apparatus including the optical pickup according to any one of the first to eighteenth aspects.

According to the present invention, the signal light beam reflected by the layer on which the spot is condensed on the multilayer information recording medium and the stray light beam reflected by the layer on which the spot is not condensed are converted into the condensing point of the detection optical system. Since complete separation can be detected using the difference, a good signal without crosstalk can be acquired.
By using the beam splitting means, it becomes possible to separate the stray light beam without wasting the signal beam.
By using the beam splitting means, the number of light shielding means can be reduced and the optical system can be simplified.
By using a diffraction grating for the beam splitting means, the optical system can be further miniaturized.
By integrating the light shielding means, the configuration of the further optical system can be simplified.
By integrating the diffraction grating and the light shielding means, the number of parts can be reduced and the assembly can be simplified.

By installing the light source between the light shielding means, the condensing lens of the optical pickup can be shared and further miniaturized.
The optical pickup can be miniaturized by integrating the light source, the diffraction grating, the light shielding means, and the light receiving element.
It is possible to completely separate the signal light beam and the stray light light beam and at the same time integrate the focus error detection optical system.
The signal light beam and the stray light beam can be completely separated, and at the same time, the track error detection optical system can be integrated.
Even if the objective lens shifts in the track direction and an optical axis shift occurs, it is possible to detect without changing the signal beam.
By using the optical pickup of the present invention, a good reproduction signal is obtained, so that reproduction information with a low error rate can be obtained.

FIG. 1 is a diagram showing a basic configuration of the present invention.
In the figure, reference numeral 11 denotes a front light shielding means, and 12 denotes a rear light shielding means.
FIG. 2 is a cross-sectional view of the recording medium viewed from the track direction in a detection optical system for separating and detecting a signal beam reflected from a multilayer information recording medium (hereinafter simply referred to as a recording medium) and a stray light beam.
If m is a layer number counted from the layer to be recorded or reproduced on the recording medium 5, m is an integer having the maximum number of layers of the recording medium 5, and n is an arbitrary integer (where n ≧ 1). M> n), the signal light beam Lm reflected by the layer where the spot on the recording medium is condensed and the stray light beam Lm ± n reflected by the layer where the spot is not collected are at the position of the reflecting surface. The magnification of the light beam incident on the condenser lens 6 varies depending on the difference. For this reason, each light beam that has passed through the condenser lens 6 has a difference between the condensing point fm and the condensing point fm ± n. In order to avoid complication, only the case of n = 1 is shown in FIG. When m = 1, there is no negative stray light. Conversely, when m is the maximum value, there is no plus side stray light.

As apparent from the description of FIG. 18, the signal light beam Lm always enters the condenser lens as a parallel light beam parallel to the optical axis, so that the position of fm is specific to the detection optical system regardless of the value of m. Become position. Further, since the positions of fm + 1 and fm-1 are determined by the thickness of the intermediate layer of the recording medium 5, unless there is a significant difference in the thickness of the intermediate layer of the target recording medium, the condensing points fm + 1, fm, fm- The mutual interval of 1 falls within a predictable range. In other words, it can be said that these condensing points are almost fixed points regardless of the m-field value.
The stray light beam Lm + n reflected by the layer on the back side (opposite side of the objective lens 4) where the spot is focused as viewed from the objective lens 4 is closer to the condenser lens 6 side than the condensing point fm of the signal beam. A condensing point fm + n is formed. Fm + 1 is closest to the condensing point fm. On the other hand, the stray light beam Lm-n reflected by the layer on the near side (objective lens 4 side) from the layer where the spot is focused when viewed from the objective lens 4 is received by the light receiving element 8 from the condensing point fm of the signal beam. A condensing point fm-n is formed on the side. Fm-1 is closest to the condensing point fm.
The upper half area from the center line C (optical axis of the condenser lens) in the light beam traveling direction is defined as area A (indicated by a white arrow), and the lower half area is defined as area B (indicated by a black arrow). In the present invention, the front light shielding means 11 that shields the region A is installed between the condensing point fm + 1 and the condensing point fm. Further, a rear light shielding unit 12 that shields the region B is installed between the condensing point fm and the condensing point fm-1.

The light beam transmitted through the region A of the condenser lens 6 is blocked by the front light blocking unit 11 while the signal beam Lm and the stray light beam Lm-n are blocked. Since the stray light beam Lm + n is collected before the front light shielding unit 11, the position thereof is reversed to the region B and is blocked by the rear light shielding unit 12.
The stray light beam Lm-n of the light beam that has passed through the region B of the condenser lens 6 is shielded by the rear light shielding means 12. Since the stray light beam Lm + n is collected before the front light shielding unit 11, the position thereof is reversed to the region A and is blocked by the front light shielding unit 11. The signal light beam Lm is focused between the front light shielding unit 11 and the rear light shielding unit 12, and the beam position is reversed to the region A. For this reason, only the signal beam Lm passes through the front light shielding unit 11 and the rear light shielding unit 12 and is detected by the light receiving element 8.
In the above description, the front light shielding unit 11 is placed on the region A side. Conversely, if the rear light shielding unit 12 is placed on the region A and the rear light shielding unit 12 is placed on the region A, the signal light beam Lm transmitted through the region A of the condenser lens 6. Is detected by the light receiving element 8.

The present invention can also be used in an optical system for recording / reproducing a two-layer information recording medium having two information recording layers. This will be described below.
The layer close to the objective lens of the two-layer information recording medium is L0 layer, and the layer far from the objective lens is L1 layer. When the spot is focused on the L0 layer, the light beam reflected by the information recording medium includes the signal light beam Lm of the L0 layer and the stray light beam Lm + 1 of the L1 layer. Since the signal light beam Lm is condensed between the front light shielding means and the rear light shielding means, it can escape to the light receiving element. However, the stray light beam Lm + 1 is shielded by the rear light shielding means and the front light shielding means, and cannot escape to the light receiving element. Thereby, a good signal can be obtained.
When the spot is focused on the L1 layer, the light beam reflected by the information recording medium includes the L1 layer signal light beam Lm and the L0 layer stray light beam Lm-1. Since the signal light beam Lm is condensed between the front light shielding means and the rear light shielding means, it can escape to the light receiving element. However, the stray light beam Lm-1 is shielded by the front light shielding means and the rear light shielding means, and cannot escape to the light receiving element. Thereby, a good signal can be obtained.
As described above, stray light can be removed even in a two-layer information recording medium by the configuration of the present invention. In the description of the following claims, the description will be made by expressing as a multilayer information recording medium, but as described above, all the claims exhibit their effects even in the double-layer information recording medium.
In all the drawings of the present invention, the rear light shielding means is displayed in a state independent of the light receiving element, but both can be integrated. Alternatively, the same effect can be obtained by making the light receiving element itself insensitive to the region to be shielded, for example, by arranging the light receiving region only in the region opposite to the region where the rear light shielding means is to be disposed.

FIG. 2 is a diagram showing an embodiment for preventing light loss in the present invention.
In the figure, reference numeral 13 denotes a beam splitting means.
This figure shows a detection optical system for efficiently separating and detecting a signal beam reflected from a multilayer information recording medium and a stray light beam.
In the present embodiment, a light beam branching unit 13 that divides the light beam into two regions A and B is provided between the condenser lens 6 and the front light shielding unit 12. Since the light beam splitting means 13 is a reflection system, a region A is formed on the right side of the bent center line C in the figure for the light beam reflected upward, and the light beam reflected downward is on the left side of the center line C in the drawing. Region A occurs in Both are indicated by white arrows. The same display is performed in subsequent figures. Note that the optical system below the light beam splitting means 13 is distinguished by attaching a symbol to it.
With such a configuration, the region A above the center line C is substantially the same as the state in which the regions where the front light shielding unit 11 and the rear light shielding unit 12 are arranged are exchanged as described above with reference to FIG. Is obtained.
The light beam transmitted through the region A by the condenser lens 6 is reflected by the light beam branching means 13 and travels toward the light receiving element 8. Between the condensing point fm + 1 and the condensing point fm, a front light shielding unit 11 that shields the region B is installed. Further, a rear light shielding unit 12 that shields the region A is installed between the condensing point fm and the condensing point fm-1. Since the stray light beam Lm + n is collected before the front light shielding unit 11, the position thereof is reversed to the region B and is blocked by the front light shielding unit 11. The stray light beam Lm-n is shielded by the rear light shielding means 12. The signal light beam Lm is focused between the front light shielding unit 11 and the rear light shielding unit 12, and the beam position is inverted to the region B. For this reason, only the signal beam Lm passes through the front light shielding unit 11 and the rear light shielding unit 12 and is detected by the light receiving element 8.

The light beam transmitted through the region B by the condenser lens 6 is reflected by the light beam branching means 13 and travels toward the light receiving element 8 ′. Between the condensing point fm + 1 and the condensing point fm, a front light shielding unit 11 ′ that shields the region A is installed. Further, a rear light shielding unit 12 ′ that shields the region B is installed between the condensing points fm and fm−1. Since the stray light beam Lm + n is collected before the front light shielding unit 11 ′, the position thereof is reversed to the region A and is blocked by the front light shielding unit 11 ′. The stray light beam Lm-n is shielded by the rear shading means 12 '. The signal light beam Lm is focused between the front light shielding unit 11 ′ and the rear light shielding unit 12 ′, and the position of the beam is reversed to the region A. Therefore, only the signal light beam Lm passes through the front light shielding unit 11 ′ and the rear light shielding unit 12 ′ and is detected by the light receiving element 8 ′.
As described above, the signal light beam transmitted through the region A by the condensing lens 6 is detected by the light receiving element 8, and the signal light beam transmitted through the region B by the condensing lens 6 is detected by the light receiving element 8 ′. It becomes possible to detect the light flux without wasting it.
Although the light beam splitting means 13 of the present embodiment is illustrated using the two outer surfaces of a right-angle prism, it may be a combination of two simple plane reflecting mirrors, and the crossing angle of the two reflecting mirrors is also a right angle. Need not be. In short, it is only necessary that the crossing positions of the two reflecting mirrors coincide with each other on the center line C so that the mechanical parts such as the light shielding plate do not come into contact with other parts.

FIG. 3 is a diagram for explaining another embodiment of the present invention.
In the figure, reference numeral 14 denotes a light shielding means.
This embodiment is a detection optical system for separating and detecting a signal light beam and a stray light beam reflected by a multilayer information recording medium efficiently and with a simpler configuration.
In the present embodiment, the position of the light beam branching unit 13 is further away from the condensing lens 6 and is positioned between the condensing point fm + 1 and the condensing point fm.
In this way, in the same figure, the light beam reflected upward from the light beam splitting means 13 has both the stray light light beams Lm + 1 and Lm−1 in the region A, and the light beam Lm passes through the region B after passing the condensing point fm. To come to exist. Therefore, if the light shielding means 14 that shields the area A is placed on the side far from the condensing point fm when viewed from the condensing lens 6, only the signal light beam Lm reaches the light receiving element 8.
The light receiving element 8 'can receive only the signal light beam Lm if the light blocking means 14' is placed in the region B in the same way even below the light beam branching means 13.
The light shielding means 14 in this embodiment has a function similar to that of the rear light shielding means shown in FIGS. Therefore, it is possible to integrate the light shielding means 14 with the light receiving element 8. The relationship between the light shielding means 14 ′ and the light receiving element 8 ′ is the same.

FIG. 4 is a view for explaining still another embodiment of the present invention.
In the figure, reference numeral 15 denotes a beam splitting means.
This embodiment is a detection optical system for separating and detecting a signal light beam and a stray light beam reflected by a multilayer information recording medium efficiently and with a simpler configuration.
In the present invention, the light beam branching means 15 for dividing the light beam into two parts in the region A and the region B is provided between the condensing point fm + 1 and the condensing point fm. The beam splitting means 15 has a configuration in which two optical wedges are integrated so as to be vertically symmetrical by abutting the thinner one. Note that the optical system below the center line C after the beam splitting means is distinguished by attaching a symbol to the symbol.
When the light beam transmitted through the region A by the condenser lens 6 is not condensed before the light beam branching unit 15, the light beam is refracted by the light beam branching unit 15 and travels toward the light receiving element 8. A light shielding unit 14 that shields the region A is installed between the condensing point fm and the condensing point fm-1.
When the light beam transmitted through the region B by the condenser lens 6 is not condensed before the light beam branching unit 15, the light beam is refracted by the light beam branching unit 15 and travels toward the light receiving element 8 ′. Between the condensing point fm and the condensing point fm−1, a light shielding unit 14 ′ that shields the region B is installed.
The stray light beam Lm + n transmitted through the region A by the condensing lens 6 is collected before the beam splitting means, so that the position thereof is reversed to the region B and is shielded by the light shielding unit 14 ′. The stray light beam Lm-n is shielded by the light shielding means 14. The signal light beam Lm is focused between the light beam branching unit 15 and the light shielding unit 14, and the beam position is inverted to the region B. For this reason, only the signal beam Lm passes through the light shielding means 14 and is detected by the light receiving element 8.

Since the stray light beam Lm + n transmitted through the region B by the condenser lens 6 is collected before the beam splitter 15, its position is reversed to the region A and is shielded by the light shield 14. The stray light beam Lm-n is shielded by the light shielding means 14 '. The signal light beam Lm is focused between the light beam branching means 15 and the light shielding means 14 ′, and the position of the beam is reversed to the region A. For this reason, only the signal beam Lm passes through the light shielding means 14 'and is detected by the light receiving element 8'.
As described above, the signal light beam Lm transmitted through the region A by the condenser lens 6 is detected by the light receiving element 8, and the signal light beam Lm transmitted through the region B by the condenser lens 6 is detected by the light receiving device 8 ′. The signal light beam Lm can be detected without wasting it. Further, since the stray light beam Lm ± n is all removed by the two light shielding means 14, 14 ', the configuration of the optical system is simplified.
The arrangement position of the beam splitter 15 used in the present embodiment can be closer to the condensing lens 6 than the condensing point fm + 1. This configuration is the same as that of the embodiment shown in FIG. 2 in principle, and a front light shielding unit and a rear light shielding unit are required for each branched light beam. In that case, the rear light shielding means corresponding to the two light fluxes can be integrated because they are in close proximity to each other.

FIG. 5 is a view for explaining still another embodiment of the present invention.
In the figure, reference numeral 16 denotes a diffraction grating as a beam splitting means.
The present embodiment is a detection optical system for separating and detecting a signal beam reflected from a multilayer information recording medium and a stray light beam efficiently and with a simpler configuration, and the beam splitter 15 of the optical pickup shown in FIG. Instead, the light beam branching means 16 comprising a blazed diffraction grating is used.
As is well known, a blazed diffraction grating is a diffraction grating in which the diffraction efficiency of an arbitrary order is enhanced by using a Bragg condition of diffraction. In this description, the blazed diffraction grating with the highest + 1st order light or −1st order light will be described. However, the diffraction order at this time can take an arbitrary value. It is not limited. Furthermore, the grating shape of the blazed diffraction grating used here is not a simple oblique fixed period, but preferably has an arbitrary period satisfying all the Bragg conditions for incident convergent light.
The blazed diffraction grating used in the present invention produces a diffracted light with a strong + 1st order light for the region A light beam and a diffracted light with a strong -1st order light for the region B light beam. The blazed diffraction grating has a different diffraction direction in each region.
In the present embodiment, a blazed diffraction grating that divides a light beam into two is provided between a condensing point fm + 1 and a condensing point fm. Further, the optical system below the center line C after the beam splitting means is distinguished by attaching a symbol to the symbol.

When the light beam transmitted through the region A by the condenser lens 6 is not condensed before the light beam branching means 16, it is diffracted by the blazed diffraction grating and travels toward the light receiving element 8. A light shielding unit 14 that shields the region A is installed between the condensing point fm and the condensing point fm-1.
When the light beam transmitted through the region B by the condenser lens 6 is not condensed before the light beam branching means 16, it is diffracted by the blazed diffraction grating and travels toward the light receiving element 8 '. Between the condensing point fm and the condensing point fm−1, a light shielding unit 14 ′ that shields the region B is installed.
The stray light beam Lm + n transmitted through the region A by the condensing lens 6 is collected before the light beam splitting means 16, so that its position is reversed to the region B and is shielded by the light shielding means 14 ′. The stray light beam Lm-n is shielded by the light shielding means 14. The signal light beam Lm is focused between the light beam branching means 16 and the light shielding means 14, and the position of the beam is reversed to the region B. Therefore, only the signal light beam Lm passes through the light shielding means 14 and is detected by the light receiving element 8a.
The stray light beam Lm + n transmitted through the region B by the condensing lens 6 is collected before the light beam splitting unit 16, so that the position thereof is reversed to the region A and is shielded by the light shielding unit 14. The stray light beam Lm-n is shielded by the light shielding means 14 '. The signal light beam Lm is focused between the light beam branching means 16 and the light shielding means 14 ′, and the position of the beam is reversed to the region A. For this reason, only the signal beam Lm passes through the light shielding means 14 'and is detected by the light receiving element 8'.
As described above, the signal light beam Lm transmitted through the region A by the condenser lens 6 is detected by the light receiving element 8, and the signal light beam Lm transmitted through the region B by the condenser lens 6 is detected by the light receiving device 8 ′. The signal light beam Lm can be detected without wasting it. Further, since the stray light beam Lm ± n is all removed by the two light shielding means 14, 14 ', the configuration of the optical system is simplified. In addition, since the blazed diffraction grating can be formed in a flat plate shape, the optical system can be miniaturized.
If the beam splitting means 16 is arranged closer to the condenser lens 6 side than the condensing point fm + 1, the front light shielding means and the rear light shielding means are required as described in FIG.

FIG. 6 is a diagram showing a modification of the embodiment shown in FIG.
In the figure, reference numeral 17 denotes a diffraction grating as a beam splitting means, and 18 denotes a light shielding means.
This embodiment is a detection optical system for separating and detecting a signal light beam and a stray light beam reflected by a multilayer information recording medium efficiently and with a simpler configuration.
The light beam splitting means 17 used in the present embodiment is similar to FIG. 5 and uses a combination of blazed diffraction gratings. That is, the light beam splitting means 17 generates diffracted light with strong -1st order light for the light flux in region A, and diffracted light with strong + 1st order light for the light flux in region B. A blazed diffraction grating having different diffraction directions in each region. For this reason, each signal beam diffracted in each region of the blazed diffraction grating once intersects before the light shielding means.
In the present embodiment, a light beam splitting unit 17 that splits a light beam into two is provided between the condensing point fm + 1 and the condensing point fm.
When the light beam transmitted through the region A by the condenser lens 6 is not condensed before the light beam branching means 17, it is diffracted by the blazed diffraction grating and travels toward the light receiving element 8 '. A light shielding means 18 is installed between the condensing point fm and the condensing point fm-1, and the lower end portion 18b shields the region A from light.
When the light beam transmitted through the region B by the condensing lens 6 is not condensed before the light beam branching means 17, it is diffracted by the blazed diffraction grating and travels toward the light receiving element 8. Between the condensing point fm and the condensing point fm-1, the upper end portion 18a of the light shielding unit 18 installed shields the region B from light.

Since the upper end portion 18a and the lower end portion 18b of the light shielding means 18 have different roles, they may be configured separately. However, since they are arranged close to each other, they are shared by one sheet.
The stray light beam Lm + n transmitted through the area A by the condenser lens 6 is condensed before the light beam splitting means 17, so that its position is reversed to the area B and is shielded by the light shielding means 18. The stray light beam Lm-n is shielded by the light shielding means 18. The signal light beam Lm is focused between the light beam branching unit 17 and the light shielding unit A, and the position of the beam is reversed to the region B. Therefore, only the signal light beam Lm passes through the light shielding means 18 and is detected by the light receiving element 8 ′.
The stray light beam Lm + n transmitted through the region B by the condensing lens 6 is collected before the light beam splitting unit 17, so that its position is reversed to the region A and is shielded by the light shielding unit 18. The stray light beam Lm-n is also shielded by the light shielding means 18. The signal light beam Lm is focused between the light beam branching unit 17 and the light shielding unit 18, and the beam position is inverted to the region A. For this reason, only the signal beam Lm passes through the light shielding means 18 and is detected by the light receiving element 8.
As described above, the signal light beam Lm transmitted through the region A by the condenser lens 6 is detected by the light receiving element 8 ′, and the signal light beam Lm transmitted through the region B by the condenser lens 6 is detected by the light receiving device 8. The signal light beam Lm can be detected without wasting it. Further, since all the stray light beam Lm ± n is removed by the light shielding means 18, the configuration of the optical system is simplified. In addition, since the blazed diffraction grating can be formed in a flat plate shape, the optical system can be miniaturized.
In addition, since it is self-evident, illustration is omitted, but in the case where the two optical wedges are integrated as a vertically symmetrical structure by abutting the thicker one as the light beam branching means 14 in FIG. Since the direction in which the light beam is bent is opposite to that in the figure, as a result, an optical path similar to that of the present embodiment is formed. Therefore, similarly to the light shielding means 18 of the present embodiment, the light shielding means can be constituted by one sheet.

FIG. 7 is a view showing an embodiment in which the beam splitting means and the light shielding means shown in FIGS. FIG. 6A is a diagram corresponding to FIG. 5, and FIG. 6B is a diagram corresponding to FIG.
In FIG. 7, reference numerals 19 and 20 denote light beam branching light shielding means, respectively.
In this embodiment, the optical system is further simplified in a detection optical system for separating and detecting the signal light beam and the stray light beam reflected by the multilayer information recording medium efficiently and with a simple configuration.
In the present embodiment, a diffraction grating is used as the light beam branching means, so that the diffraction grating and the light shielding means can be laminated together to form the light beam branching light shielding means 19 and 20 as one component.

FIG. 8 is a view for explaining still another embodiment of the present invention.
In this embodiment, in the detection optical system for separating and detecting the signal beam and the stray light beam reflected by the multilayer information recording medium with a simpler configuration, the pickup is further miniaturized by arranging the light source at an appropriate position. Is.
This embodiment shows a configuration applied to the embodiment shown in FIG. In FIG. 8, the light source 1 is disposed between the light shielding means 14 and 14 '. Further, the light beam splitting means 16 transmits a light beam in the polarization direction emitted from the light source 1 without being diffracted, and a blazed polarization diffraction grating that diffracts the light beam in the polarization direction orthogonal to the polarization direction emitted from the light source 1. Used.
The light beam emitted from the light source 1 is directed to the condenser lens 6 without receiving an action from the diffraction grating (the illustration is omitted from here). The light beam converted into a parallel light beam by the condenser lens 6 is converted into circularly polarized light by the λ / 4 wavelength plate, condensed by the objective lens 4, and condensed on the information recording medium 5. The signal light beam reflected by the information recording medium 5 becomes a parallel light beam again by the objective lens 4 and becomes linearly polarized light having a polarization direction orthogonal to the polarization direction emitted from the light source by passing through the λ / 4 wavelength plate again, The light passes through the condenser lens 6, is branched and diffracted by the diffraction grating of the light beam branching means 16, and is detected by the light receiving elements 8 and 8 ′.
As already described, the stray light beam in the multilayer information recording medium 5 is blocked by the light blocking means, and only a good signal beam is detected by the light receiving elements 8 and 8 '.
The light source 1, the diffraction grating 16, the light shielding means 14, and the light receiving elements 8 and 8 ′ can be integrated into an optical unit. With such a configuration, the optical system of the optical pickup of the present invention can be further downsized.

FIG. 9 is a view for explaining still another embodiment of the present invention.
In the figure, reference numeral 21 denotes a second condenser lens, 22 denotes a divided light receiving element, and S denotes an output signal from the light receiving element.
This embodiment shows a configuration for obtaining a focus error signal at the same time in a detection optical system for separating and detecting a signal beam reflected from a multilayer information recording medium and a stray light beam.
In the present embodiment, the second light collecting lens 21 is provided between the rear light shielding unit 12 and the divided light receiving element 22, and the signal light beam Lm is detected by the divided light receiving element 22 in a place where the signal light beam Lm is condensed.
The principle of acquiring the focus error signal in this configuration will be described.
When the light beam emitted from the objective lens 4 is collected on the information recording medium 5, the signal light beam Lm reflected from the information recording medium 5 is collected between the single elements 22 a and 22 b of the divided light receiving element 22, and each of the single elements. The difference Sa-Sb between the outputs Sa and Sb is zero. On the other hand, when the objective lens 4 moves away from the information recording medium 5, the light beam collected by the second condenser lens 21 is once condensed before the divided light receiving element 22, and the beam spread in a semicircular shape is 22b. (Indicated by a dotted line after the second lens). That is, Sa−Sb <0. On the contrary, when the objective lens approaches the information recording medium, the light beam condensed by the second condenser lens 21 is condensed behind the divided light receiving element 22, so that it is a semicircle before being condensed. Is incident on 22a (indicated by a broken line after the second lens). That is, Sa−Sb> 0. Therefore, by calculating Sa-Sb, a signal (= focus error signal) indicating where the objective lens is focused on the information recording medium can be obtained.
At this time, the signal beam is obtained by Sa + Sb.
In this description, the configuration for detecting the focus error signal for the optical system of FIG. 1 is shown, but this configuration can be applied to any of the optical systems of FIGS.
In this embodiment, since the 2nd condensing lens 21 is arrange | positioned between the back light-shielding means 12 and the light receiving element 22, the back light-shielding means 12 and a light receiving element cannot be integrated. Instead, the rear light shielding unit 12 and the second condenser lens 21 can be integrated. The second condenser lens only needs to have a lens function on one side from the optical axis on the incident side of at least a light beam. Any shape can be used on the opposite side from the optical axis as long as the light flux is fortune-telling.

FIG. 10 is a view for explaining still another embodiment of the present invention. 4A is a diagram showing the positional relationship between the front light shielding means and the rear light shielding means and the light beam, FIG. 4B is a diagram showing the positional relationship between the light beam branching means and the light beam, and FIG. FIG. 5B is a diagram illustrating an example of the position and state of a light beam when the optical axis is shifted in the track direction in FIG. It is.
In the figure, reference numeral 24 denotes a beam spot, 25 denotes a divided gland, and 26 denotes a branch line.
This embodiment shows a configuration in which the absolute amount of a signal beam does not change even when the objective lens is shifted in the track direction in a detection optical system for separating and detecting a signal beam reflected from a multilayer information recording medium and a stray light beam. The light beam reflected by the information recording medium 5 is diffracted by the grooves of the information recording medium 5 to form a baseball ball pattern (track pattern) shown in FIG. Of the patterns divided by the curve, the central pattern is the reflected light from the track part, and the patterns on both sides are the diffracted light generated in relation to the step parts on both sides of the track. Is big. In the following description, it is assumed that the patterns on both sides have a larger amount of light than the central pattern.
In the present invention, the dividing line 25 that blocks the light flux of the front light shielding means 11 and the rear light shielding means 12 or the branch line 26 that branches the light flux of the light flux branching means is directed in the track direction of the signal light flux. . As shown in FIG. 6C, when the optical axis shift in the track direction occurs, the light beam moves in the direction of the dividing line 25 or the branch line 26 with respect to the optical system. For this reason, even if the objective lens 4 is shifted in the track direction and the optical axis shift occurs in the signal light beam, the distribution of the light beams above and below the dividing line 25 and the branch line 26 does not change. The signal can be detected without changing the amount of light.

FIG. 11 is a diagram showing a configuration for acquiring a track error signal. 2A is an optical path diagram, and FIG. 2B is a plan view of a light receiving element.
In the detection optical system for separating and detecting the signal beam reflected from the multilayer information recording medium and the stray light beam, a track error signal can be simultaneously acquired.
In the present invention, the signal light beam Lm is detected by the divided light receiving element 22 (22c, 22d). The divided light receiving element 22 is divided into at least two along the data recording direction y by a dividing line in a direction perpendicular to the dividing line 25 and the branch line 26 described above.
The acquisition principle of the track error signal in this configuration will be described.
The signal light beam that has passed through the light shielding means of this configuration becomes a semicircular divergent beam and is detected by the divided light receiving element.
When the spot is at the center of the groove on the information recording medium, the track pattern is left-right symmetric, so the difference Sc-Sd between the outputs Sc and Sd from the divided light receiving elements is zero. When the information recording medium is decentered due to eccentricity or the like, the track pattern becomes asymmetrical as shown in FIG. 10C, so that Sc-Sd changes to> 0 or <0. To do. Therefore, by calculating Sc-Sd, a signal indicating where the spot is being tracked with respect to the information recording medium (= track error signal) can be obtained.
At this time, the signal beam is obtained by Sc + Sd.

FIG. 12 is a diagram showing a configuration for simultaneously acquiring a focus error signal and a track error signal.
In a detection optical system for separating and detecting a signal beam reflected from a multilayer information recording medium and a stray light beam, a focus error signal and a track error signal can be acquired simultaneously.
In the present invention, a light beam branching unit 13 that splits a light beam into two regions A and B is provided between the condenser lens 6 and the front light shielding unit. This part is the same as the configuration shown in FIG. For the signal light beam transmitted through the region A by the condensing lens 6, the second light collecting lens 21 is provided between the rear light shielding means 12 and the light receiving element, and the signal light beam Lm is collected at the place where the signal light beam Lm is condensed. Is detected by the divided light receiving element 23 (23a, 23b). For the signal light beam transmitted through the region B by the condenser lens 6, the signal light beam Lm is divided into at least two divided light receiving elements 23 ′ (23′c, 23′d) along the data recording direction y. Detect with.
With this configuration,
Focus error signal is Sa-Sb
The track error signal is Sc-Sd
Playback signal is Sa + Sb + Sc + Sd
By acquiring the signal, each signal can be acquired without the influence of the stray light beam.

A block diagram of a recording / reproducing apparatus equipped with the optical pickup of the present invention is the same as FIG.
A processing operation when data is recorded on the information recording medium 15 using the recording / reproducing apparatus 20 configured according to the present invention will be briefly described with reference to FIG. When the CPU 40 receives a recording request from the host, the CPU 40 outputs a control signal for controlling the rotation of the spindle motor 22 based on the recording speed to the motor driver 27 and also indicates that the recording request has been received from the host. 28 is notified. When the rotation of the information recording medium 15 reaches a predetermined linear velocity, the reproduction signal processing circuit 28 accurately acquires address information based on the output signal not affected by the stray light beam from the optical pickup device 23 and notifies the CPU 40 of the address information. To do. Further, the reproduction signal processing circuit 28 detects the track error signal and the focus error signal based on the output signal not affected by the stray light beam from the optical pickup device 23 of the present invention, and outputs it to the servo controller 33. The servo controller 33 accurately drives the tracking actuator and the focusing actuator of the optical pickup device 23 via the motor driver 27 based on the track error signal and the focus error signal from the reproduction signal processing circuit 28. That is, track deviation and focus deviation are corrected with high accuracy. The CPU 40 accumulates data from the host in the buffer RAM 34 via the buffer manager 37. When the amount of data stored 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, and the optical pickup 23 is located at a predetermined write start point based on the address information from the reproduction signal processing circuit 28. Thus, a signal for instructing the seek operation of the optical pickup 23 is output to the motor driver 27. 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, the CPU 40 notifies the encoder 25. The encoder 25 records the write data on the information recording medium 15 via the laser control circuit 24 and the optical pickup device 23.

Next, the processing operation when reproducing the data recorded on the information recording medium 15 using the recording / reproducing apparatus 20 described above will be briefly described. When receiving a 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 also indicates that the reproduction request has been received from the host. 28 is notified. When the rotation of the information recording medium 15 reaches a predetermined linear velocity, the reproduction signal processing circuit 28 acquires address information based on the output signal from the optical pickup device 23 and notifies the CPU 40 of the address information. Further, the track deviation and the focus deviation are accurately corrected in the same manner as in the case of the recording described above. Based on the address information from the reproduction signal processing circuit 28, the CPU 40 outputs a signal for instructing a seek operation so that the optical pickup device 23 is positioned at a predetermined reading start point to the motor driver 27. Based on the address information from the reproduction signal processing circuit 28, the CPU 40 checks whether or not it is a reading start point. If the CPU 40 determines that the position of the optical pickup device 23 is a reading start point, the CPU 40 notifies the reproduction signal processing circuit 28. Notice. Then, the reproduction signal processing circuit 28 detects a reproduction signal that is not affected by the stray light beam from the output signal of the optical pickup device 23 of the present invention, performs error correction processing, etc., and stores it in the buffer RAM 34. The buffer manager 37 transfers the data stored in the buffer RAM 34 to the host via the interface 38 when the data is prepared as sector data. Until the recording process and the reproduction process are completed, the reproduction signal processing circuit 28 detects the focus error signal and the track error signal based on the output signal from the optical pickup device 23 as described above, and the servo controller 33 and the motor. A focus shift and a track shift are corrected with accuracy through the driver 27 as needed.
As is clear from the above description, in the recording / reproducing apparatus according to the present embodiment, the reproducing signal processing circuit 28, the CPU 40, and the program executed by the CPU 40 perform recording and reproducing operations on the multilayer information recording medium. It has been realized. However, it goes without saying that the present invention is not limited to this. That is, the above embodiment is merely an example, and at least a part of each component realized by processing according to the program by the CPU 40 may be configured by hardware, or all the components are configured by hardware. It's also good.

FIG. 20 is a diagram showing an embodiment in which the light beam splitting means and the light shielding means of FIG. 4 and its modification are integrated. 4A is a diagram corresponding to FIG. 4, and FIG. 4B is a diagram showing an example using an optical wedge in which the thicker ones are abutted.
In the figure, reference numerals 24 and 25 denote light beam branching and shielding means, respectively.
Since this embodiment is substantially the same as the embodiment shown in FIG. 7 in principle, detailed description thereof is omitted. However, although the thickness of the prism 24a of the light beam separating / shading means 24 is increased in FIG. 4A, for example, as shown by a two-dot chain line, the portion outside the effective light beam may be cut off.
Although the light beam is refracted even after passing through the light beam branching and shielding means, it is shown in a simplified manner in the figure.

It is a figure which shows the basic composition of this invention. It is a figure which shows embodiment for preventing the light quantity loss in this invention. It is a figure for demonstrating other embodiment of this invention. It is a figure for demonstrating other embodiment of this invention. It is a figure for demonstrating other embodiment of this invention. It is a figure which shows the modification of embodiment shown in FIG. It is a figure which shows embodiment which integrates the light beam branching means and light-shielding means of FIG. It is a figure for demonstrating other embodiment of this invention. It is a figure for demonstrating other embodiment of this invention of this invention. It is a figure for demonstrating other embodiment of this invention. It is a figure which shows the structure for acquiring a track error signal. It is a figure which shows the structure for acquiring a focus error signal and a track error signal simultaneously. It is a figure for demonstrating a general optical pick-up. It is a figure for demonstrating an optical unit. It is a figure for demonstrating a diffraction grating. It is a block diagram for demonstrating recording or reproduction | regeneration or a recording / reproducing apparatus. It is a figure for demonstrating the structure of a double layer information recording medium. It is a figure for demonstrating the reproduction | regeneration condition of a double layer information recording medium. It is a figure which shows the result of having observed the mode that the jitter which is a reproduced signal of a L0 layer deteriorates when the intermediate | middle layer thickness is narrowed on the conditions of 2 layer DVD. It is a figure which shows embodiment which integrates the light beam branching means and light-shielding means of FIG. 4 and its modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 3 Detection separation means 4 Objective lens 5 Multilayer information recording medium 6 Detection lens 8 Light receiving element 11 Front light shielding means 12 Back light shielding means 13, 15, 16, 17 Light beam branching means 14, 18 Light shielding means 19, 20 Light beam branch light shielding means 21 Second condensing lens 22, 23 Dividing element 24, 25 Light beam branching light blocking means

Claims (21)

  A multilayer information recording medium (hereinafter simply referred to as a recording medium) having a light source, a collimating lens, a detection / separating means, an objective lens, a detection optical system, and a light receiving element and recording information on layers having different substrate thicknesses. In the optical pickup for recording, reproducing, or recording / reproducing the light, the detection optical system for detecting the light beam reflected by the recording medium, the light collecting means for condensing the light beam on the light receiving element, and the recording medium The condensing point of the signal light beam Lm reflected by the mth layer on which the light beam is condensed is fm, the condensing point of the stray light beam Lm + 1 reflected by the m + 1th layer is fm + 1, and the (m−1) th layer. When the condensing point of the stray light beam Lm−1 reflected by fm is defined as fm−1, the condensing in the cross section viewed from the track direction of the recording medium between the condensing point fm and the condensing point fm + 1. One from the optical axis of the means An optical pickup comprising: a front light shielding means for shielding light; and a rear light shielding means for shielding the other side from the optical axis between the light condensing point fm and the light condensing point fm-1. .   A multilayer information recording medium (hereinafter simply referred to as a recording medium) having a light source, a collimating lens, a detection / separating means, an objective lens, a detection optical system, and a light receiving element and recording information on layers having different substrate thicknesses. In the optical pickup for recording, reproducing, or recording / reproducing the light, the detection optical system for detecting the light beam reflected by the recording medium, the light collecting means for condensing the light beam on the light receiving element, and the recording medium The condensing point of the signal light beam Lm reflected by the mth layer on which the light beam is condensed is fm, the condensing point of the stray light beam Lm + 1 reflected by the m + 1th layer is fm + 1, and the (m−1) th layer. When the condensing point of the stray light beam Lm−1 reflected by fm is defined as fm−1, the condensing in the cross section viewed from the track direction of the recording medium at a position closer to the condensing means than the condensing point fm + 1. Depending on the optical axis of the means A light beam branching means for branching the light beam into two regions, and the optical axis for shielding the stray light beam Lm + 1 between the condensing point fm and the condensing point fm + 1 for each branched light beam. And a rear light-shielding means disposed on one side from the rear, and a rear light-shielding means disposed on the other side from the optical axis in order to shield the stray light beam Lm-1 between the condensing point fm and the condensing point fm-1. An optical pickup comprising a light shielding means.   A multilayer information recording medium (hereinafter simply referred to as a recording medium) having a light source, a collimating lens, a detection / separating means, an objective lens, a detection optical system, and a light receiving element and recording information on layers having different substrate thicknesses. In the optical pickup for recording, reproducing, or recording / reproducing the light, the detection optical system for detecting the light beam reflected by the recording medium, the light collecting means for condensing the light beam on the light receiving element, and the recording medium The condensing point of the signal light beam Lm reflected by the mth layer on which the light beam is condensed is fm, the condensing point of the stray light beam Lm + 1 reflected by the m + 1th layer is fm + 1, and the (m−1) th layer. When the condensing point of the stray light beam Lm−1 reflected by fm is fm−1, the light beam is seen between the condensing point fm and the condensing point fm + 1 in a cross section when viewed from the track direction of the recording medium. Optical axis of the light collecting means Therefore, the stray light beam Lm + 1 and the stray light beam Lm-1 are divided between the light condensing point fm and the light condensing point fm-1 with respect to the light beam branching means that branches into two regions. An optical pickup comprising: a light shielding unit disposed on one side from the optical axis for shielding light.   4. The optical pickup according to claim 3, wherein the light beam branching unit has a structure in which two optical wedges are integrated so as to be vertically symmetrical by abutting the thinner one. .   4. The optical pickup according to claim 3, wherein the light beam branching unit has a structure in which two optical wedges are integrated so as to be vertically symmetrical by abutting the thicker one. .   6. The optical pickup according to claim 5, wherein a light shielding means provided for each branched light beam is integrated.   7. The optical pickup according to claim 4, wherein the optical wedge and the light shielding means are integrated.   4. The optical pickup according to claim 3, wherein the light beam branching means is a blazed diffraction grating in which each region has a different diffraction direction in the cross section.   9. The optical pickup according to claim 8, wherein the blazed diffraction grating has a grating angle set so that light beams diffracted in each region intersect each other.   10. The optical pickup according to claim 9, wherein a light shielding means provided for each branched light beam is integrated.   11. The optical pickup according to claim 8, wherein a light source is disposed at a position of a condensing point fm to be generated when the diffraction grating is not provided, and the light source is formed by the blazed diffraction grating. Emits linearly polarized light in a direction that is not diffracted.   12. The optical pickup according to claim 8, wherein the diffraction grating and the light shielding unit are integrated.   12. The optical pickup according to claim 8, wherein the diffraction grating, the light shielding unit, the light source, and the light receiving element are integrated as an optical unit. .   2. The optical pickup according to claim 1, wherein a second condensing lens is provided in front of the light receiving element, and at least a part of the light receiving element is divided into lines parallel to a track direction. And optical pickup.   2. The optical pickup according to claim 1, wherein at least part of the light receiving element is a two-divided light receiving element divided by a line orthogonal to the track direction.   14. The optical pickup according to claim 2, wherein a second light collecting lens is provided in front of the light receiving element for the one light beam branched by the light beam branching unit, and the collected signal light beam is received. An optical pickup characterized by detecting with a two-divided light receiving element divided by a line parallel to the track direction.   14. The optical pickup according to claim 2, wherein a light receiving element that detects a light beam not provided with a second condenser lens in front of the light receiving element branched by the light beam branching unit is parallel to the track direction. An optical pickup characterized by being divided into at least two by a line.   14. The optical pickup according to claim 2, wherein a second light collecting lens is provided in front of the light receiving element for the one light beam branched by the light beam branching unit, and the collected signal light beam is received. An optical pickup characterized in that the light receiving element that is detected by a two-divided light receiving element divided by a line parallel to the track direction and that the other light beam is detected is divided into at least two by a line parallel to the track direction.   An optical recording apparatus comprising the optical pickup according to claim 1.   An optical reproducing apparatus comprising the optical pickup according to any one of claims 1 to 18.   An optical recording / reproducing apparatus comprising the optical pickup according to claim 1.

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