JP2002175640A - Optical head, light receiving/emitting element and device for recording/reproducing optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical head that enables accurate discrimination of the track region, mirror region, address pit region, etc., formed on the information recording surface of an optical recording medium with simple structure, and also to provide light receiving/emitting elements and a device for recording/ reproducing an optical recording medium. SOLUTION: The optical head is equipped with a semiconductor laser, optical diffraction elements, an objective lens, a photodetecting element, etc. By the operation of the optical diffraction element there are formed the main spot B1 and two sub spots B2, B3, as detecting spots, on the light receiving parts 74A, 74B, 74C of the photodetecting element. Assuming that the spot diameters in the radial direction are W10, W20, W30 for each spot B1, B2, B3, the relation is W20<W10<W30. Assuming the sizes in the radial direction are W11, W21, W31 for the divided regions s, r, t of each light receiving part, W11/W10, W21/W20, and W31/W30 are designed to be nearly the same value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting / receiving element and an optical head for writing and reading an information signal to / from an optical recording medium such as an optical disk, and to such a light receiving / emitting element or an optical head. The present invention relates to an optical recording medium recording / reproducing apparatus configured to record and reproduce information signals on and from an optical recording medium.

[0002]

2. Description of the Related Art Conventionally, there is an optical recording medium recording / reproducing apparatus for recording / reproducing information signals on / from an optical recording medium such as an optical disk. In such an optical recording medium recording and reproducing apparatus, an information signal is written to and read from the optical recording medium by an optical head (optical pickup device). The optical head converges and irradiates a light beam output from a light source onto an information recording surface of the optical disk by an objective lens, and writes an information signal on the information recording surface.
The information recording surface is configured to detect reflected light of a light beam applied to the information recording surface and read an information signal recorded on the information recording surface. The information recording surface of the optical disc is provided with lands for recording and reproducing information, track areas where grooves are formed, mirror areas, address pit areas where address pits are formed, and the like. When recording / reproducing information on / from the optical disk, it is necessary to accurately determine the track area, mirror area, address pit area, and the like.

[0003]

However, as far as the present applicant knows, there is no technique that can accurately determine the track area, the mirror area, the address pit area and the like with a simple configuration. The present invention has been made in view of such a situation, and aims at discriminating a track area, a mirror area, an address pit area formed on an information recording surface of an optical recording medium, and An object of the present invention is to provide an optical head, a light emitting / receiving element, and an optical recording medium recording / reproducing apparatus which can accurately determine whether the track area is a land or a groove with a simple configuration.

[0004]

According to the present invention, there is provided an optical head comprising: a light source for emitting a light beam toward an information recording surface of an optical recording medium; and a light detecting means for receiving a reflected light beam reflected from the optical recording medium. And at least one converging spot is formed on the information recording surface by the light beam emitted from the light source, and the light detecting means corresponds to the converging spot. A plurality of detection spots are formed, and the light detection unit has a light receiving unit that receives the plurality of detection spots corresponding to each of the plurality of detection spots, and the plurality of detection spots are provided for each spot. The light receiving portions are formed so as to have different dimensions in a predetermined direction, and each of the light receiving portions is composed of a plurality of divided regions divided in the predetermined direction, and the detection spots extend over the respective divided regions of the light receiving portion. In the state where the light spots are formed, the ratio of the size of the detection spot in the predetermined direction to the size of each portion where the detection spot is formed in each of the divided areas in the predetermined direction is the light receiving ratio. It is characterized in that the parts are configured to be substantially the same. The light emitting and receiving element of the present invention includes a light source that emits a light beam, and a light detection unit that receives a light beam that is reflected from the optical recording medium, and the information recording is performed by the light beam that is emitted from the light source. At least one converging spot is formed on a surface, a plurality of detecting spots are formed on the light detecting means corresponding to the converging spots, and the light detecting means Each of the plurality of detection spots has a light receiving unit that receives the plurality of detection spots corresponding to each of the detection spots, and the plurality of detection spots are formed so that dimensions in a predetermined direction are different for each spot. It is composed of a plurality of divided areas divided in a predetermined direction, and in a state where the detection spot is formed over each of the divided areas of the light receiving section, the detection spot in the predetermined direction is formed. And the ratio between the size in the predetermined direction of each portion where the detection spot is formed in each of the divided areas is substantially the same between the light receiving units. Features. An optical recording medium recording / reproducing apparatus according to the present invention includes: a driving unit that rotationally drives an optical recording medium; And a signal processing circuit that generates a reproduction signal based on a detection signal from the optical head, wherein the optical head includes a light source and light detection means. The light source is configured to emit the light beam, and the light detection means is configured to receive the reflected light beam and output the detection signal, and the light detection unit outputs the detection signal according to the light beam emitted from the light source. At least one on the information recording surface
And a plurality of detection spots are formed on the light detection means corresponding to the light collection spots, and the light detection means corresponds to each of the light collection spots. Each of the plurality of detection spots has a light receiving portion that receives the plurality of detection spots, and the plurality of detection spots are formed so that dimensions in a predetermined direction are different for each spot, and each of the light reception portions is divided in the predetermined direction. In a state where the detection spot is formed over each of the divided areas of the light receiving unit, the detection spot is formed in each of the divided areas and the dimension of the detection spot in the predetermined direction. The ratio of the respective portions to the dimensions in the predetermined direction is substantially the same between the respective light receiving portions. An optical recording medium recording / reproducing apparatus according to the present invention includes: a driving unit that rotationally drives an optical recording medium; An optical head for detecting a signal, and a signal processing circuit for generating a reproduction signal based on a detection signal from the optical head,
The optical head includes an objective lens, a light receiving and emitting element provided with a light source and light detecting means, the light source is configured to emit the light beam, and the light detecting means includes the reflected light beam. And the detection signal is output, and the light beam emitted from the light source forms at least one condensed spot on the information recording surface. A plurality of detection spots are formed on the top corresponding to the condensed spots, and the light detection unit has a light receiving unit that receives the plurality of detection spots corresponding to each of the condensed spots, The plurality of detection spots are formed so that dimensions in a predetermined direction are different for each spot, and each of the light receiving units is configured by a plurality of divided areas divided in the predetermined direction. In a state where the detection spot is formed over the split region, the size of the detection spot in the predetermined direction and the size of the portion in which the detection spot is formed in each of the divided regions in the predetermined direction are defined. It is characterized in that the ratio is substantially the same between the respective light receiving sections.

According to the optical head of the present invention, the plurality of detection heads
Detected in each divided area of each light receiving unit that received the outgoing spot
Output from each of the divided areas corresponding to the respective divided areas.
Information recording surface based on the calculation result of each detected signal
Track area, mirror area, address
Can be determined. Also before
The detection spot is formed over each divided area of the light receiving section.
In the formed state, the size of the detection spot in the predetermined direction
Method and the detection spot in each of the divided areas.
In the predetermined direction of each part where
The ratio with the dimensions is almost the same between the light receiving parts
Output from the light receiving unit corresponding to each of the divided areas.
The ratio of each detection signal is almost the same between the light receiving units.
Therefore, when the above detection signals are calculated, the results of the calculation are automatically added.
The occurrence of fset is prevented. Light emitting / receiving element of the present invention
According to the child, each of the plurality of detection spots received
Detected in each divided area of the light receiving section and
Calculation result of each detection signal output from each of the divided areas
A track area provided on the information recording surface based on
It is necessary to determine the mirror area, address pit area, etc.
It becomes possible. In addition, the light receiving portion extends over each divided region.
In the state where the detection spot is formed,
The size of the pot in the predetermined direction and the size of each of the divided areas
In each case, the detection spot is formed.
The ratio of this part to the dimension in the predetermined direction is the
Between the light receiving unit and the respective divisions
The ratio of each detection signal output corresponding to the
It became almost the same between the light sections, and the above-mentioned detection signals were calculated.
Sometimes prevents the result of the calculation from being offset.
It is. According to the optical medium recording / reproducing apparatus of the present invention,
In each of the divided areas of each of the light receiving units that received the detection spot of
Detected from each of the divided areas corresponding to each of the divided areas
The information storage is performed based on the calculation result of each detection signal output.
Track area, mirror area, and address provided on the recording surface
It is possible to determine the pit area and the like. Ma
In addition, the detection spot is located over each divided area of the light receiving section.
In the state where the spot is formed, the predetermined
In each of the divided areas.
The predetermined portion of each portion where the exit spot is formed
Direction and the ratio between the light receiving sections are almost the same.
Therefore, output from the light receiving section corresponding to each of the divided areas
The ratio of each detected signal is almost the same between the light receiving units.
When the above detection signals are calculated, the calculation results
Is prevented from being offset.

[0006]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferred limits are given, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description. Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an optical recording medium recording / reproducing apparatus incorporating an optical head according to a first embodiment of the present invention. In FIG. 1, a disk device 101 includes a spindle motor 103 as a driving unit for driving the optical disk 1 (optical recording medium) to rotate, an optical head 104, and a feed motor 105 as a driving unit for the optical head 104. . Here, the spindle motor 103 is driven and controlled by a system controller 107 and a servo control circuit 109, and is rotated at a predetermined rotation speed. As the optical disk 1, a read-only Pit disk may be used, but a recording / reproduction disk using optical modulation recording, such as "CD-R / RW" or "DVD-R"
"DVD-RAM""DVD-R / RW""DVD + R"
For example, it is more effective to use “DVR-BLUE” or the like, which is a high-density optical disk using a short wavelength light source near 405 nm. Signal modulator / demodulator and ECC block 1
08 performs modulation and demodulation of a signal and addition of an ECC (error correction code). The optical head 104 irradiates the information recording surface (signal recording surface) of the rotating optical disk 1 with light according to the signal modulation and the command of the ECC block 108. Recording is performed by such light irradiation. Further, the optical head 104 detects a light beam as described later based on the light beam reflected from the information recording surface of the optical disc 1, and supplies a signal corresponding to each light beam to the preamble section 20. The preamplifier unit 120 is configured to generate a focus error signal, a tracking error signal, an RF signal, and the like based on a signal corresponding to each light beam. Depending on the type of the recording medium to be reproduced, predetermined processing such as demodulation and error correction processing based on these signals is performed by the servo control circuit 109 and the signal modulation & ECC block 108 and the like. As a result, the demodulated recording signal is transmitted to the external computer 115 or the like via the interface 111 for data storage of a computer, for example. Thus, an external computer or the like can receive a signal recorded on the optical disc 1 as a reproduction signal. Also, if it is for audiovisual,
The digital / analog conversion is performed by the D / A conversion unit of the D / A and A / D converter 112, and the audio / visual processing unit 1
The audio / video signal processing is carried out there, and transmitted to an external imaging / projection device via an audio / visual signal input / output unit 114. These preamplifier unit 120, signal modulation & ECC block 108,
A signal processing circuit includes the D / A, A / D converter 112, the audio / visual processing unit 113, and the like. A feed motor 105 for moving the optical head 104 to a predetermined recording track on the optical disk 1, for example, is connected to the optical head 104. The control of the spindle motor 103, the control of the feed motor 105, and the control of the focusing direction and the tracking direction of the biaxial actuator for holding the objective lens of the optical head 104 are performed by the servo control circuit 109, respectively.

FIG. 2 is a configuration diagram of the optical head according to the first embodiment. FIG. 2A is a plan view, and FIG. 2B is a side view. This embodiment shows an example of an optical head of a type that performs “beam shaping” using an anamorphic prism. Optical recording medium recording / reproducing device, especially “C
DR-RW / DVD-R / DVD-RAM / D
VD-R / RW, DVD + RW, DVR-BLU
E "or other recording / reproducing type optical recording medium recording / reproducing device,
Recording characteristics change depending on the shape of the condensed spot condensed on the disk. Usually, a semiconductor laser is often used as a light source for this type of system. In the case of a semiconductor laser, the divergence angle of the emitted beam is structurally parallel to the bonding surface (θ // direction). The full width at half maximum is about 10 degrees, and the full width at half maximum is about 20 to 30 degrees in the direction perpendicular to the bonding surface (θ⊥ direction) (this difference in divergence angle θ⊥ / θ // is called the aspect ratio). Using a morphic prism or the like, the magnification of the outgoing light beam with respect to the incident light beam is changed (that is, compressed or expanded) in a specific direction of the light beam cross section and emitted (“beam shaping”), and the light intensity distribution is changed according to the direction. It is used so that non-uniformity is not so large.

The configuration of the optical head 2 according to the first embodiment will be described with reference to FIG. The optical head 2 includes a semiconductor laser 61 as a light source and a forward collimator lens 6.
2. Anamorphic prism 63, half-wave plate 64, light diffraction element 65 (corresponding to the spot forming means in the claims), polarization beam splitter prism 66, light detection element 67, quarter-wave plate 68, startup A mirror 69, an objective lens 70, a return collimator lens 71, a hologram element 72, a cylindrical lens 73, a light detection element 74, and the like are provided. The semiconductor laser 61
Constitutes a light source and is configured to emit a light beam. The forward collimator lens 62
Is for converting the light beam emitted from the semiconductor laser 61 into parallel light. The anamorphic prism 63 corrects the light beam from the outward collimator lens 62. That is, the configuration is such that the non-uniformity of the light intensity distribution in the light beam is corrected by enlarging the cross section of the light beam in the direction corresponding to the θ // direction of the light beam. As the anamorphic prism 63, the present applicant has filed Japanese Patent Application No. 2000-1237.
The straight-through anamorphic prism devised in 23 can be used. The half-wave plate 64 rotates the polarization direction of the light beam incident from the anamorphic prism 63.

The light diffraction element 65 converts the light beam incident from the half-wave plate 64 into three beams, that is, a main beam, in order to generate a tracking error signal and a land / groove discrimination signal (CTS signal) described later. And two sub-beams. A main spot and two sub-spots are formed by irradiating the main beam and two sub-beams on the photodetector 74,
The light diffraction element 65 has a function of making the focus positions of the main spot and the two sub spots in the radial direction of the optical disc 1 (direction orthogonal to the track) different from each other (defocusing) in the optical axis direction. Have. In this specification, the in-focus position refers to a position of a focal point (convergence point) at which the light beam is focused (converged) by the objective lens 70. That is, in the radial direction, when the main spot is focused on the recording surface of the optical disc 1, one of the two sub-spots is closer to the light source than the recording surface. It is configured to focus and the other focus at a position farther than the recording surface.

The polarizing beam splitter prism 66 has two
It has two polarizing beam splitter surfaces 66a and a total reflection surface 66b. The polarization beam splitter surface 66a is configured to transmit P-polarized light and reflect S-polarized light of the incident light beam. The total reflection surface 66b is configured to reflect the light beam regardless of the polarization direction. The 波長 wavelength plate 68 transmits the P beam transmitted through the polarizing beam splitter surface 66 a of the polarizing beam splitter prism 66.
The polarized light beam is configured to be circularly polarized.
The rising mirror 69 is provided between the quarter-wave plate 68 and the objective lens 70, and is configured to bend the optical path of the light beam by 90 degrees. The objective lens 70 is configured to converge the incident light beam on the information recording surface of the optical disc 1 and to convert the light beam reflected back from the optical disc 1 into parallel light. The return path collimator lens 71 is configured to enter the return path light beam reflected by the total reflection surface 66b and convert it into convergent light.

The hologram element 72 is configured to split an incident light beam into ± first-order light and zero-order light. This is for detecting the ± first-order optical har-focus error signal by the spot size method. The zero-order light is R
This is for detecting the F signal and the tracking error signal. The configuration of the hologram element 72 will be described later. The cylindrical lens 73 is configured such that each light beam emitted from the hologram element 72 is defocused only in the radial direction, and the shape of the light beam is elongated in the radial direction. The light detecting element 74 is provided with the cylindrical lens 73.
Is configured to receive each light beam emitted from the device and output a detection signal.

The schematic operation of the optical head 2 thus configured will be described. The light beam emitted from the semiconductor laser 61 passes through a forward collimator lens 62, an anamorphic prism 63, and a half-wave plate 64, and is incident on a diffraction grating 65. The light beam incident on the diffraction grating 65 is split into the main beam and two sub-beams, passes through the polarizing beam splitter surface 66a of the polarizing beam splitter prism 66 as P-polarized light, and is transmitted by a quarter-wave plate 68. , And enters the objective lens 70. The light beam is converged on the information recording surface of the optical disc 1 by the objective lens 70, and recording and reproduction of a signal are performed. The light beam reflected and returned from the optical disk 1 is again converted into parallel light by the objective lens 70, the optical path is changed by 90 degrees by the rising mirror 69, and the 波長 wavelength plate 68
Incident on. The light beam has its polarization direction changed by 90 degrees with respect to the outward path by a quarter-wave plate 68, and is reflected as S-polarized light by a deflection beam splitter surface 66 a of a polarization beam splitter prism 66, and then a total reflection surface 66 b , And is incident on the return path collimator lens 71. After being converted into convergent light by the return path collimator lens 71, it is incident on the hologram element 72. The light beam is separated into the ± first-order light and the zero-order light by the hologram element 72, and is received by the light detection element 74. Based on the received light signal, a servo signal such as a focus error signal, a tracking error signal, a land / groove discrimination signal, and an RF signal are generated, and the information is reproduced and a light spot (condensing spot) on the disk is controlled. Is performed.

FIG. 3 is a plan view showing the relationship between the detection spot on the photodetector and the light receiving section. The light diffraction element 65, the hologram element 72, and the light detection element 74 will be described in detail with reference to FIG. As shown in FIG. 3, the photodetector 74 includes three light receiving sections 74A, 74B, 74C for obtaining a tracking error signal TE, a land / groove discrimination signal CTS, and an RF signal, and a focus error signal. It is composed of two light receiving sections 74D and 74E. Three light receiving sections 74A, 74B, 74C
Are provided at equal intervals linearly in the tangential direction, and a light receiving portion 74B for receiving a main spot at the center is provided.
(Corresponding to the first light receiving unit in the claims)
A light receiving portion 74A (corresponding to a second light receiving portion in the claims) and a light receiving portion 74C (corresponding to a third light receiving portion in the claims) that receive two sub-spots sandwiching 4B in the tangential direction are positioned. It is configured to be. Each light receiving section 7
Each of 4A, 74B, and 74C has a divided region divided into three in the radial direction. That is, the light receiving unit 7
4A includes two divided areas h (corresponding to a fifth divided area in the claims) sandwiching a divided area r (corresponding to a fourth divided area in the claims) located at the center in the radial direction, and a divided area i. (Corresponding to the sixth divided area in the claims). The light receiving section 74B is a divided area s located at the center in the radial direction (corresponding to a first divided area in the claims).
And two divided regions j (corresponding to a second divided region in the claims) and a divided region k (corresponding to a third divided region in the claims). The light receiving unit 74C is provided with a divided region t
A divided region 1 (corresponding to the eighth divided region in the claims) and a divided region m (corresponding to the ninth divided region in the claims) are sandwiched by (corresponding to the seventh divided region in the claims). Have. As shown in FIG.
Of the divided regions A, 74B, and 74C, the first divided region s, the fourth divided region r, and the seventh divided region t have radial dimensions that are formed on the light receiving units 74A, 74B, and 74C. The spots and the sub-spots are configured to have different dimensions corresponding to the radial dimensions.
This will be described later. In the first embodiment,
The tracking error signal is transmitted to each of the light receiving sections 74A and 74A.
B and 74C are detected based on the radial light intensity distribution of the main spot and the two sub spots. That is, detection of the tracking error signal is performed by the differential push-pull method.

The land / groove discrimination signal is detected based on a radial light intensity distribution of two sub-spots on the light receiving sections 74A and 74C. This will be described later. The RF signal is detected based on the light amount of the main spot on the light receiving section 74B.

The two light receiving portions 74D and 74E are provided linearly in the radial direction with the light receiving portion 74B interposed therebetween, and are arranged at regular intervals with the light receiving portion 74B. Each light receiving section 7
4D and 74E each have a divided region divided into five in the tangential direction. That is, the light receiving unit 7
4D includes a divided region b located at the center in the tangential direction, two divided regions a and c sandwiching the divided region b, and two divided regions n and o located outside the divided region a and c. Similarly, the light receiving unit 74E includes a divided region e located at the center in the tangential direction and two divided regions f and d sandwiching the divided region e.
And two divided areas q and p located outside the divided areas q and p. In the first embodiment, the focus error signal is a dimension in the tangential direction of a detection spot composed of ± primary light formed by separating the main spot on each of the light receiving sections 74D and 74E by the hologram element 72. Is detected based on That is, detection of the focus error signal is performed by the spot size method.

A detection signal detected by each of the light receiving sections 74A to 74E is subjected to current-voltage conversion by an amplifier (not shown) formed on a semiconductor substrate of the photodetector 74 of the optical head 2, for example. A focus error signal FE,
The tracking error signal TE, the land / groove determination signal CTS, and the RF signal are calculated. Each of the divided areas a, b, c, d, e, f, h, i, j, k, l, m,
The signal values output from r, s, t are a, b,
c, d, e, f, h, i, j, k, l, m, r, s, t
Then, the arithmetic expression of the focus error signal FE by the spot size method, the arithmetic expression of the tracking error signal TE by the differential push-pull method, the arithmetic expression of the RF signal, and the land / groove determination signal CTS are as shown below, for example. Expressions (1), (2), and (3) below are based on the well-known spot size method, the differential push-pull method, and the well-known principle, and thus description thereof will be omitted, and expression (4) will be described later. I do. FE = (a + c−b−no) − (d + fe−p−q) (1) TE = (j−k) −K * {(hi) + (lm)} (2) (Where K is a coefficient and * is a multiplication symbol) RF = j + k + s (3) CTS = {(h + i) -r}-{(l + m) -t} (4)

Next, the light diffraction element 65 will be described.
The main beam and the two sub-beams are separated by the action of the light diffraction element 65, and the main spot and the two sub-spots are formed by irradiating the photodetector 74 with the main beam. The light diffraction element 65 has a function of making the focus positions of the main spot and the two sub spots in the radial direction of the optical disc 1 (direction orthogonal to the track) different from each other (defocusing) in the optical axis direction. Have. In the radial direction, when the main spot is focused on the recording surface of the optical disc 1, one of the two sub-spots is focused at a position closer to the light source than the recording surface. The other is configured to focus at a position farther than the recording surface.

Next, the hologram element 72 will be described. FIG. 4 is an explanatory diagram of the operation of the hologram element 72. FIG. 4A shows the hologram element 7 from the tangential direction.
FIG. 4B shows a state in which the cylindrical lens 72 and the light detecting element 74 are viewed from the radial direction, and FIG. 4B shows a state in which the cylindrical lens 72 and the light detecting element 74 are viewed from the radial direction.
FIG. 5 is a plan view of the light detection element 74. FIG.
2A and 2B are diagrams showing a configuration in which a hologram element 72 is provided between a cylindrical lens 73 and a photodetection element 74 unlike FIG.
Since the operation is the same even if the positions of the hologram element 72 and the hologram element 72 are interchanged, the operation will be described with reference to FIG. 4 and 5
As shown in FIG. 2, the hologram element 72 separates the light beam (main beam and two sub-beams) reflected from the recording surface of the optical disc 1 into zero-order light and ± first-order light. It is configured. Only in the direction in which the spot size is detected (tangential direction), ±
The design is such that defocusing is performed so that the focusing positions of the primary light in the optical axis direction are different from each other. Therefore, the zero-order light,
In the radial direction of the three spots of ± primary light, the focusing position in the optical axis direction is kept substantially equal. On the other hand, the cylindrical lens 73 extends the focus position in the optical axis direction of the light beam (main beam and two sub beams) reflected from the recording surface of the optical disc 1 in the radial direction (to change the beam shape in the radial direction). Stretch) design. Therefore, in the tangential direction, the focus position in the optical axis direction is kept substantially equal. By extending the shape of the light beam in the radial direction by the cylindrical lens 73, the spot diameter in the direction in which the push-pull detection is performed (radial direction) can be made larger. Deterioration of characteristics due to a positional shift or the like due to an environmental change or the like of the detection spot with respect to the portion is also reduced. The hologram element 72 shifts the focus position of the light beam in the optical axis direction only in the tangential direction to form a detection spot of ± primary light. Even if it is extended in the radial direction by the action, the dimension of the detection spot of ± primary light in the radial direction is maintained, and no asymmetry of the shape occurs between the detection spots of ± primary light in the radial direction.

Next, the land / groove discrimination signal CTS
Will be described. The signal detection principle in the land / groove discrimination signal detection method according to the present invention will be described. The optical diffraction element 65 forms two sub-beams whose focal positions in the optical axis direction are different from each other in the radial direction with respect to the main beam, and the main beam is focused on the recording surface of the optical disc 1 to obtain a signal. When the recording and reproduction are performed, the two sub-beams are configured such that the focus position in the optical axis direction is shifted (defocused) in the radial direction. In this state, when the main spot and the two sub-spots by the main beam and the two sub-beams cross the track on the recording surface of the optical disk in the radial direction, the main spots have the same land / groove intensity distribution. In the sub-spot, track discrimination is performed using a fact that a large difference occurs in the intensity distribution in the detection spot between the land and the groove due to a change in the interference state of the wavefront due to a shift of the focusing position in the optical axis direction in the radial direction.

FIGS. 6 to 11 show characteristic diagrams showing an example of the result of calculating the intensity distribution and the phase distribution of the disk diffraction light on the objective lens pupil during reproduction. The calculation conditions were as follows: optical head: wavelength λ = 405 nm, objective lens NA = 0.
85 disc: track cycle = 0.60 μm (0.30 *
2) Reciprocating phase depth = λ / 6 For simplicity, the land and groove are both rectangular with equal width. 6 to 11 show the radial direction on the X axis, the tangential direction on the Y axis, and the intensity of the returning light on the Z axis. FIG. 6 shows a state where the converging spot is located on the land and the focus position in the radial direction is shifted by -0.35 μm in the optical axis direction. FIG. 7 shows a state in which the converging spot is located on the land and the focus position in the radial direction matches the position of the groove in the optical axis direction. FIG.
Shows a state in which the converging spot is located on the land and the focus position in the radial direction is shifted by +0.35 μm in the optical axis direction. FIG. 9 shows a state in which the focused spot is located on the groove, and the focus position in the radial direction is shifted by -0.35 μm in the optical axis direction. FIG. 10 shows a state in which the converging spot is located on the groove and the focus position in the radial direction matches the position of the land in the optical axis direction. FIG. 11 shows a state in which the focused spot is located on the groove and the focus position in the radial direction is shifted by +0.35 μm in the optical axis direction.

In land / groove recording, recording is performed on both the land and the groove. Therefore, considering a normal track period between a land and a land or between a groove and a groove, the track period with respect to the spot diameter is large. As shown in FIG. 12, the manner in which the diffracted light on the disc overlaps the objective lens pupil greatly differs. As shown in FIGS. 12A and 12B, in the conventional disk reproduction using land recording, the 0th-order light and the ± 1st-order light do not usually overlap. On the other hand, as shown in FIGS. 12C and 12D, when land-groove recording is used, the zero-order light and the ± first-order light overlap. 6 to 11, a portion where the intensity protrudes in the detection spot is a region where all of the zero-order light and the ± first-order light overlap. As is clear from FIGS. 6 to 11 and 12, the focus position in the optical axis direction in the radial direction of the detected spot is not shifted (FIGS. 7 and 10).
In the above, the intensity distribution in the detection spot does not change depending on whether the condensed spot is on the land or on the groove, whereas the focus position in the optical axis direction in the radial direction of the detection spot is shifted ( 6, 8, 9, and 11), there is a difference in the intensity distribution in the detection spot. In addition, the tendency of the intensity distribution in the detection spot is reversed depending on whether the focused spot is on the land or on the groove. That is, FIGS. 6 and 11 are the same, and FIGS.
Have the same tendency.

As described above, each of the sub-beams is defocused in the radial direction by the action of the optical diffraction element 65. FIG. 13 shows the light receiving section 7 of the light detecting element 74.
4A, 74B, and 74C are explanatory diagrams schematically showing a state of a change in intensity distribution, and FIG. 13A is an explanatory diagram showing a state where a main spot is located on a groove;
FIG. 3 (B) is an explanatory view showing a state where the main spot is located on the land, FIG. 13 (C) is an explanatory view showing a state where the main spot is located on the groove, and FIG. 13 (D) is a view with respect to the position in the radial direction. FIG. 4 is an explanatory diagram showing a tracking error signal TE and a land / groove discrimination signal CTS. FIG.
As shown in (A), (B), and (C), a central portion (the central divided region r,
Since the intensity of t) increases and the intensity of the peripheral portion (peripheral divided regions h, i, l, m) increases, the intensity distribution on the land / groove changes. The land / groove discrimination signal CTS can be obtained by the arithmetic expression (Equation (4)) using the change in the output from each of the light receiving units 74A and 74C. The tracking error signal TE is obtained by an arithmetic expression (Expression (2)). The positional relationship between the main spot and the two sub-spots on the recording surface of the optical disk is such that when the main spot is on the groove, the sub-spot is located on the land (in the case of FIG. It is desirable to set the sub-spot to be located on the groove when it is on the groove, and depending on which is set, the polarity of the land / groove discrimination signal CTS is inverted. The tracking error signal TE and the land / groove discrimination signal CTS have a phase difference of 90 degrees, and have substantially the same amplitude. Further, as described above, by setting the positional relationship between the main spot and the two sub-spots on the recording surface of the optical disc as described above, based on the positive / negative of the land / groove discrimination signal CTS, Whether the spot corresponding to the main spot is on the land or on the groove can be easily determined.

As for the shift of the focus position in the optical axis direction in the radial direction of the light beam by the light diffraction element 65, for example, the same curve pattern is repeatedly arranged in the tangential direction as shown in FIG. Optical diffraction element 65
This can be realized by using Since the optical diffraction element 65 in which the same curve pattern is repeatedly arranged in the tangential direction has no power in the tangential direction, it can diffract the light beam transmitted through any position in the tangential direction. The amount of aberration added to light becomes equal, and stable characteristics are obtained. Since the diffraction directions are different between the two sub-spots, FIG.
As shown in (B), the transmission position is shifted,
Since the same pattern is repeated, no characteristic change occurs depending on the position. By generating the land / groove discrimination signal CTS in this manner, the tracking control method conventionally used can be used also in the land / groove recording method in which the land width and the groove width are substantially equal. Of course, a method of recording on either one of the land and the groove is applicable.

Next, the principle of determining a track area, a mirror area, and an address pit area using the tracking error signal TE and the land / groove determination signal CTS will be described. FIG. 16 is an explanatory diagram of the principle of a method for determining a track area, a mirror area, and an address pit area. Horizontal axis (X
On the axis, the tracking error signal TE is taken, and on the vertical axis (Y
Considering a waveform (hereinafter referred to as a discrimination waveform) of the land / groove discrimination signal CTS on the axis), the phase of the tracking error signal TE and the land / groove discrimination signal CTS are shifted by 90 degrees as described with reference to FIG. And the amplitudes are the same, the waveform is almost circular. Here, the amplitudes of the tracking error signal TE and the land / groove discrimination signal CTS are larger in the track area than in the address pit area. Since the information recording surface of the mirror area is a mirror surface, no signal amplitude is generated.
In FIG. 16, the range of the discrimination waveform in the case of the track area is the area between the circles R1 and R2, and the range of the discrimination waveform in the case of the address pit area is the area between the circles R2 and R3. Assuming that the range of the discrimination waveform in the case of the region is a region within the circle R3, which of the track region, the address pit region, and the mirror region is determined based on which of the regions the discrimination waveform corresponds to. Can be easily determined. In other words, based on the calculation result of each detection signal output from each of the divided areas detected in each of the divided areas of each of the light receiving units that have received the main spot and the two sub-spots and corresponding to each of the divided areas. Thus, it is possible to determine a track area, a mirror area, an address pit area and the like provided on the information recording surface.

By the way, when the above-mentioned discrimination method is used,
When a positive or negative offset occurs between the tracking error signal TE and the land / groove discrimination signal CTS, the center point of the generated discrimination waveform becomes the origin (the tracking error signal T
(E and the zero point of the land / groove discrimination signal CTS), which makes accurate discrimination impossible. The occurrence of such an offset is caused by a difference in the radial spot diameter between the main spot and the sub spot formed on the photodetector 74 as described below.

FIG. 15 shows the tracking error signal TE and the land / groove discrimination signal CTS of the photodetector 74.
Light receiving sections 74A, 74B, 74C for detecting
FIG. (Note that FIG. 15 exaggerates the difference in the radial direction between the divided regions for the sake of explanation.) As described above, the main diffraction spot in the radial direction is actuated by the action of the optical diffraction element 65. Is optical disk 1
When focusing on the recording surface of
One sub-spot is configured to focus at a position closer to the light source than the recording surface, and the other sub-spot is configured to focus at a position farther than the recording surface. Therefore, the light detecting element 74
On each of the light receiving sections 74A, 74B, and 74C, the sub spot B2 focuses on the main spot B1 at a position near the light source, and the sub spot B3 focuses on a position far from the light source.
Therefore, when the radial spot diameters of the spots B1, B2, and B3 are W10, W20, and W30,
W20 <W10 <W30. Where W
12, W13 are radial dimensions of a region of the main spot B1 irradiated to the divided regions j and k, and are configured such that W12 = W13.
Similarly, W22 and W23 are radial dimensions of an area of the sub spot B2 irradiated to the divided areas h and i, and are configured such that W22 = W23. Similarly, W32 and W33 are radial dimensions of an area of the sub spot B3 irradiated to the divided areas 1 and m, and are configured such that W32 = W33.

Here, if the divided areas s, r, and t are configured to have the same radial dimension, the signal value s by the main spot B1 detected by the light receiving section 74B,
The ratio s: j: k of j and k and the ratio r: h of signal values r, h, and i by the sub spot B2 detected by the light receiving unit 74A:
i is different from the ratio t: l: m of the signal values t, l, and m by the sub spot B3 detected by the light receiving unit 74C. In this state, each signal s, j, k, r, h,
The land / groove discrimination signal C is calculated using i, t, l, and m.
When the TS is generated, the land / groove signal discrimination signal C
There is a problem that an offset occurs in the TS. Further, when the tracking error signal TE is generated from each of the signals, there is a problem that the amplitudes of the two push-pull signals (hi) and (lm) formed by the sub spots are asymmetric. As a result, there occurs a problem that the position of the discrimination waveform is shifted. In order to solve such a problem, the ratio of each of the signal values, that is, the ratio s: j: k, the ratio r: h: i, and the ratio t: l: m substantially coincide with each other. What is necessary is just to set the radial dimension of s, r, and t. Therefore, when the radial dimension of the divided area s is W11, the radial dimension of the divided area r is W21, and the radial dimension of the divided area t is W31, W11 / W
What is necessary is just to comprise so that 10 and W21 / W20 and W31 / W30 become substantially the same. In other words, the light receiving unit 7
4A to 74C, s, j, k, r, h, i,
With the main spot and the two sub spots formed over t, l, and m, the size of the spot in the radial direction (predetermined direction) and each of the divided areas s, j, k,
In each of r, h, i, t, l, and m, the ratio of the respective portions where the spots are formed to the radial dimension is substantially the same between the light receiving units 74A to 74C. The ratio of the detection signals output from the light receiving units 74A to 74C corresponding to the respective divided areas s, j, k, r, h, i, t, l, m is determined by the light receiving units 74A to 74C.
4C, the detection signals s, j,
When k, r, h, i, t, l, and m are calculated to obtain the tracking error signal TE and the land / groove discrimination signal CTS, the calculation results (both signals TE and CTS) are prevented from being offset. Is done. By setting the radial dimension of each divided area in this way, the offset between the tracking error signal TE and the land / groove discrimination signal CTS is prevented, so that the position of the discrimination waveform does not deviate, and region,
It is possible to obtain an effect that it is possible to accurately and easily determine which of the mirror areas corresponds to with a simple configuration. The signals s, j, k, h, r, h,
i, t, l, and m correspond to the first signal S1 to the ninth signal S9 in the claims, respectively.

Next, the light emitting / receiving element of the present invention will be described. FIG. 17 is a configuration diagram of an example (a second embodiment) of a preferred embodiment of an optical head using the light receiving / emitting element of the present invention. In FIG. 17, an optical head 5 is a light emitting / receiving element 130 in which a light source, a light detecting element, and an optical component are combined and integrated.
And other components for condensing the light beam emitted from the light emitting / receiving element 130 on the optical disc 1 in an optimal state. The other components include a quarter-wave plate 68, an objective lens 70, a liquid crystal element 77, a collimator 81, an anamorphic mirror 82, and a chromatic aberration correction lens 83. The 波長 wavelength plate 68 and the objective lens 70 are the same as those described with reference to FIG. The collimator 81 converts a light beam into parallel light or convergent light. The anamorphic mirror 82 is for shaping a light beam.
It has the same function as the anamorphic prism 63. The liquid crystal element 77 corrects spherical aberration caused by an error in the substrate thickness of the optical disc 1 in an optical system having a high NA. The chromatic aberration correcting lens 83 corrects chromatic aberration that occurs when, for example, a short wavelength light source is used.

FIG. 18 is an explanatory view showing the structure of the light receiving / emitting element and the light receiving element. FIG. 18 (A) is a structural view of the light receiving / emitting element viewed from the side, and FIG. FIG. 18C is a plan view showing another portion of the photodetector. The structure of the light emitting / receiving element 130 will be described with reference to FIG. The light receiving / emitting element 130 includes a light source 131, a mirror prism 132, a substrate 133, a half-wave plate 134, a compound lens 135, a compound prism 136, a light detecting element 137, and the like. The light receiving / emitting element 130 is provided with the mirror prism 132, the half-wave plate 134, the compound lens 135, the compound prism 136, the light detecting element 137, and the like integrally provided on the substrate 133. The compound lens 135 includes the optical diffraction element 13
5a, coupling lens 135b, cylindrical lens 135c, hologram element 135d, concave lens 13
5e, having a split-type hologram element 135g. The composite prism 136 includes a polarizing beam splitter film 136a and a half mirror 136b. As shown in FIGS. 18B and 18C, the light detecting element 137 includes three light receiving sections 137 for obtaining a tracking error signal and a land / groove discrimination signal.
A, 137B and 137C, two light receiving sections 137D and 137E for obtaining a focus error signal, a light receiving section 137F for obtaining an RF signal, and four light receiving sections 137G, 137H, 137I and 137J for obtaining a DPP signal. Have been. Four light receiving sections 137G, 137H, 1
37I and 137J are provided at four corners of a rectangle, and the light receiving units 137G and 137J are located on diagonal lines.
37H and 137I are configured to be located diagonally.

Next, the optical path of the light emitting / receiving element 130 will be described with reference to FIGS. The light beam emitted from the light source 131 has its optical path bent by the mirror prism 132, passes through an aperture on the substrate 133, and has its polarization direction rotated by the half-wave plate 134.
The light enters the compound lens 135. The light beam is separated into three beams used for tracking error detection and land / groove discrimination by the optical diffraction element 135a on the composite lens 135, and
The NA incident on the composite prism 136 and the collimator 81 is converted to a small value by the coupling lens 135b on the fifth lens 5, and the polarization beam splitter film 136a of the composite prism 136 (P-polarized light is transmitted and S-polarized light is reflected). The light is transmitted as P-polarized light and travels to the collimator 81. The light beam reflected from the optical disk 1 and returned is converted again into convergent light by the collimator 81, and then reflected by the polarization beam splitter film 136a of the composite prism 136 as S-polarized light, and the half mirror 1
By 36b, part is separated into reflected light and part is separated into transmitted light. The light reflected by the hub mirror 136b is shifted by the cylindrical lens 135c on the compound lens 135 in the optical axis direction only in the direction (radial direction) transverse to the track direction on the optical disk 1. . That is, the beam shape is elongated in the radial direction. Then, in order to detect the focus error signal FE by the spot size method by the hologram element 135d on the compound lens 135, the focus position of the light beam in the optical axis direction is shifted by ± 1 only in the tangential direction. The next-order light is separated into zero-order light for performing RF signal detection, tracking error signal TE detection, and land / groove discrimination signal CTS detection, and is received by the light receiving units 137A to 137E of the photodetector 137. The configuration of each of the light receiving units 137A to 137E is the same as that in FIG. 3 described in the first embodiment. Each light receiving unit 13
Each of the divided areas 7A to 137C includes the light receiving section 74A.
The same reference numerals are assigned to the respective divided areas of ~ 74C and their detailed description is omitted. On the other hand, the light beam transmitted through the half mirror 136b is totally reflected by the total reflection surface 136e, the focusing position in the optical axis direction is adjusted by the concave lens 135e on the compound lens 135, and the divided hologram element 135g is used. , 0 for detecting the RF signal
And light receiving portions 137F to 137 of the photodetecting element 137.
It is focused on J.

FIG. 19 shows a split type hologram element 135g.
FIG. 3 is a configuration diagram illustrating the configuration of the light receiving units 137F to 137J. The divided hologram element 135g is divided into four rectangular divided regions A, B, C, and D which are formed in a rectangular shape as a whole and are equally divided vertically and horizontally. The divided regions A and C are provided on diagonal lines, and the divided regions B and D are provided on diagonal lines. Each of the light receiving portions 137G to 137J of the light detection element 137 and the split type hologram element 13
The five divided areas A to D are provided so as to have a corresponding positional relationship. Then, the split type hologram element 135g applies the light beam incident thereon to the zero-order light emitted to the light receiving portion 137F by each of the divided regions A to D, and to the light receiving portions 137G to 137J. It is configured to separate the light into one −1st order light and four + 1st order lights. The light beam incident on the divided area A is separated so that the light receiving unit 137G is irradiated with −1st order light and the light receiving unit 137J is irradiated with + 1st order light. The light beam incident on the divided area B is irradiated with the primary light onto the light receiving section 137H, and
37I is separated so that + 1st-order light is irradiated. The light beam incident on the divided area C is transmitted to the light receiving unit 1.
The light is separated so that -1st-order light is applied to 37G and + 1st-order light is applied to the light receiving section 137J. The light beam incident on the divided region D is separated so that the light receiving portion 137H is irradiated with −1st order light and the light receiving portion 137I is irradiated with + 1st order light. Therefore, the light receiving units 137G, 13
An output signal AC corresponding to the divided areas A and C is obtained from 7J. Output signals BD corresponding to the divided areas B and D are obtained from the light receiving sections 137H and 137I. Therefore, a well-known DPD signal can be generated from each output signal. Note that an RF signal corresponding to the zero-order light of the light beam is obtained from the light receiving unit 137F. In this way, based on each output signal generated by the light received by the photodetector 137, the focus error signal FE, the tracking error signal TE, and the land / groove discrimination signal CTS
And the like, and an RF signal are generated, and reproduction of information and control of a light spot (condensed spot) on the disk are performed. FIGS. 18B and 18C show the relationship between the detection spot on the light detection element and the light receiving section. Various signals are detected by the following equations, for example. FE = (a + c−b−no) − (d + fe−p−q) (7) TE = (j−k) −K * {(hi) + (lm)} (8) (Where K is a coefficient and * is a symbol indicating multiplication) CTS = {(h + i) -r}-{(l + m) -t} (9) RF signal = output signal RF DPD signal = output signal AC and output signal BD Phase difference signal By this, the RF signal can be generated from the single light receiving unit 137F, the RF signal can be reduced in noise and the band can be widened, and the DPD signal can be detected by the four light receiving units 137G to 137J. it can.

Then, as described with reference to FIG. 15 of the first embodiment, each light receiving portion 137 of the light detecting element 137 is provided.
A, 137B, and 137C divided areas s, j, k, r,
By setting the dimensions in the radial direction of h, i, t, l, and m, the same operation and effect as in the first embodiment can be obtained.

In each of the above embodiments, the case where a semiconductor laser having a single light emitting point is used as the light source has been described as an example, but the present invention is not limited to this. That is, the light source has two or more light-emitting points, and one light-emitting point forms the main spot and another light-emitting point forms the two sub-spots. You can also. In this case, one of two sub-spots formed by the two sub-beams emitted from the other light-emitting points is closer to the objective lens with respect to the focus position of the main beam in the optical axis direction. And the other is shifted away from the objective lens. In each of the above embodiments,
Although the case where the main spot and the two sub spots are formed on the information recording surface has been described, the present invention is not limited to this, and when two or more condensed spots are formed, for example, One main spot and at least one
This is applicable when one or more sub-spots are formed. Further, in each of the above embodiments, the light receiving portion for receiving each detection spot is constituted by three divided regions. However, the present invention is not limited to this, and the light receiving portion has two or more divided regions. What is necessary is just to be provided. That is,
In a state where the detection spot is formed over each of the divided areas of the light receiving unit, a spot diameter of the detection spot in the predetermined direction and a part of the divided area in which the detection spot is formed in the predetermined direction are formed. What is necessary is just to be comprised so that the ratio with a dimension may become substantially the same in each said light-receiving part.

In each of the above embodiments, the discrimination waveform as shown in FIG. 16 is generated based on the tracking error signal TE and the land / groove signal CTS. Although the area and the mirror area are determined, the determination of each area is not limited to the method performed based on the determination waveform.
In each of the above embodiments, the tracking error signal TE is generated by the above equation (2), and the land / groove discrimination signal CTS is generated by the above equation (4). The groove determination signal CTS may be generated. Further, the discrimination of the track area, the mirror area, the address pit area, etc. provided on the information recording surface is detected in each of the divided areas of each of the light receiving sections that have received the plurality of detection spots, and corresponds to each of the divided areas. What is necessary is just to perform based on the calculation result of appropriately calculating each detection signal output from each of the divided regions,
The present invention is not limited to the above embodiments. Further, in each of the above embodiments, the optical head and the light receiving / emitting element have been described as being formed separately from the preamplifier and the servo control circuit. Of course, some of the components of the circuit may be incorporated and configured. Further, in each of the above embodiments, a case has been described in which a plurality of detection spots are formed by a plurality of condensed spots, and the tracking error signal TE and the land / groove discrimination signal CTS are generated by the plurality of detection spots. However, the present invention is not limited to this, and can be widely applied to a case where detection spots having different spot diameters are received by an arbitrary division pattern, that is, each division area of the light receiving unit and signal calculation is performed.

[0035]

As described above, according to the optical head of the present invention, the information is calculated based on the calculation results of the respective detection signals output from the respective divided areas of the respective light receiving sections that have received the plurality of detection spots. It is possible to determine a track area, a mirror area, an address pit area, and the like provided on the recording surface. Then, by configuring the ratio of each detection signal output corresponding to each divided region from each of the divided regions so as to be substantially the same between the respective light receiving units, when the respective detection signals are calculated Since an offset is prevented from occurring in the calculation result, each of the regions can be accurately determined with a simple configuration. Further, according to the light receiving and emitting element of the present invention, the track provided on the information recording surface based on the calculation result of each detection signal output from each divided area of each of the light receiving sections that has received the plurality of detection spots It is possible to determine an area, a mirror area, an address pit area, and the like. Then, by configuring the ratio of each detection signal output corresponding to each divided region from each of the divided regions so as to be substantially the same between the respective light receiving units, when the respective detection signals are calculated Since the occurrence of an offset in the calculation result is prevented, each area can be accurately determined with a simple configuration. Further, according to the optical recording medium recording / reproducing apparatus of the present invention, the information recording surface is provided on the information recording surface based on a calculation result of each detection signal output from each divided region of each of the light receiving units that has received the plurality of detection spots. It is possible to determine the track area, the mirror area, the address pit area, and the like.
Then, by configuring the ratio of each detection signal output corresponding to each divided region from each of the divided regions so as to be substantially the same between the respective light receiving units, when the respective detection signals are calculated Since an offset is prevented from occurring in the calculation result, each of the regions can be accurately determined with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an optical recording medium recording / reproducing apparatus incorporating an optical head according to a first embodiment.

FIGS. 2A and 2B are configuration diagrams of the optical head according to the first embodiment. FIG. 2A is a plan view and FIG. 2B is a side view.

FIG. 3 is a plan view illustrating a relationship between a detection spot on a light detection element and a light receiving unit.

FIG. 4 is an explanatory diagram of the operation of the hologram element 72;
(A) shows the hologram element 72 from the tangential direction.
FIG. 4B is an explanatory diagram showing a state in which the cylindrical lens 72 and the photodetector 74 are viewed from the outside, and FIG. 4B is an explanatory diagram showing a state in which the cylindrical lens 72 and the photodetector 74 are viewed from the radial direction.

FIG. 5 is a plan view of a photodetector.

FIG. 6 is a characteristic diagram showing a calculation result of an intensity distribution and a phase distribution of a disk diffraction light on an objective lens pupil during reproduction of a DVR disk.

FIG. 7 is a characteristic diagram showing a result of calculating an intensity distribution and a phase distribution of the disk diffraction light on the objective lens pupil during reproduction of the DVR disk.

FIG. 8 is a characteristic diagram showing a result of calculating an intensity distribution and a phase distribution of a disk diffraction light on an objective lens pupil during reproduction of a DVR disk.

FIG. 9 is a characteristic diagram showing a calculation result of an intensity distribution and a phase distribution of a disk diffracted light on the objective lens pupil during reproduction of a DVR disk.

FIG. 10 is a characteristic diagram showing a calculation result of an intensity distribution and a phase distribution of a disk diffracted light on the objective lens pupil during reproduction of a DVR disk.

FIG. 11 is a characteristic diagram showing a result of calculating an intensity distribution and a phase distribution of a disk diffraction light on an objective lens pupil during reproduction of a DVR disk.

FIG. 12A is an explanatory diagram of 0th-order light and ± 1st-order light at the time of disk reproduction using conventional land recording;
FIG. 2 (B) is an explanatory diagram showing the relationship between the zero-order light and the ± first-order light on the pupil of the objective lens, and FIG. 12 (C) shows the relationship between the zero-order light and the ± first-order light at the time of reproducing the disk using land / groove recording. FIG. 12D is a diagram illustrating the relationship between the 0th-order light on the objective lens pupil and the ±
It is explanatory drawing which shows the relationship of primary light.

FIG. 13 is an explanatory diagram schematically showing a state of a change in intensity distribution on each light receiving portion of the photodetector.
13A is an explanatory diagram showing a state where the main spot is located on the groove, FIG. 13B is an explanatory diagram showing a state where the main spot is located on the land, and FIG. 13C is a diagram showing the main spot located on the groove. FIG. 13D is an explanatory diagram showing the state of the tracking error signal TE with respect to the position in the radial direction.
FIG. 5 is an explanatory diagram showing a land and groove determination signal CTS.

FIG. 14A is an explanatory diagram of an optical diffraction element in which the same curve pattern is repeatedly arranged in a tangential direction,
FIG. 14B is an explanatory diagram of the positional relationship between spots.

FIG. 15 is a plan view of three light receiving units for detecting a tracking error signal TE and a land / groove discrimination signal CTS among the photodetectors.

FIG. 16 is an explanatory diagram of the principle of a method of determining a track area, a mirror area, and an address pit area.

FIG. 17 is a configuration diagram of an example (a second embodiment) of a preferred embodiment of an optical head using the light receiving / emitting element of the present invention.

18A and 18B are explanatory diagrams illustrating the configuration of a light receiving and emitting element and a light receiving element. FIG. 18A is a configuration diagram of the light receiving and emitting element as viewed from a side, and FIG. FIG. 18C is a plan view showing another portion of the photodetector.

FIG. 19 is a configuration diagram showing the configuration of a split-type hologram element and each light receiving unit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical head, 61 ... Semiconductor laser, 65 ... Optical diffraction element, 70 ... Objective lens, 74
..., Photodetectors, 74A to 74C,.
k, r, h, i, t, l, m ... divided area, 130 ...
Light receiving and emitting elements, 137A to 137C...
k, r, h, i, t, l, m ... divided areas.

Continued on the front page F term (reference) 2H049 AA03 AA50 AA57 CA20 2H051 AA14 BA42 BB10 CB19 CC03 CC07 CC13 5D118 AA13 AA18 BA01 BC09 BC12 BC17 CA23 CD02 CD03 CD07 CD08 CF04 CF08 CF17 CG04 CG24 CG26 DA20 DA40 501119 DA05 FA09 JA07 JA08 JA12 JA24 JA31 JA32 JA43 KA02 KA18

Claims (52)

[Claims] A light source that emits a light beam toward an information recording surface of an optical recording medium; and a light detection unit that receives a light beam reflected from the optical recording medium, wherein the light is emitted from the light source. At least one converging spot is formed on the information recording surface by the light beam, and a plurality of detection spots are formed on the light detecting means corresponding to the converging spot. The detection unit has a light receiving unit that receives the plurality of detection spots corresponding to each of the plurality of detection spots, and the plurality of detection spots are formed so that dimensions in a predetermined direction are different for each spot, Each of the light receiving sections is constituted by a plurality of divided areas divided in the predetermined direction, and the detection is performed in a state where the detection spot is formed over each of the divided areas of the light receiving section. The ratio between the size of the spot in the predetermined direction and the size of the portion in which the detection spot is formed in each of the divided areas in the predetermined direction is substantially the same between the light receiving units. An optical head, comprising: 2. A plurality of converging spots formed on the information recording surface by the light beam emitted from the light source, and the detection spots are formed corresponding to each of the plurality of converging spots. The optical head according to claim 1, wherein: 3. The plurality of condensed spots include one main spot and two sub-spots, and the main spot and the two sub-spots are arranged in a radial direction crossing a track of the optical recording medium. The focus position of the light beam forming the spot and the two sub-spots in the optical axis direction is different from each other, and the focus position of one of the two sub-spots is more than the focus position of the main spot. A position close to the lens, and the other in-focus position of the two sub-spots is configured to be farther from the objective lens than the in-focus position of the main spot,
The device according to claim 2, wherein the main spot and the two sub spots formed on the information recording surface are formed so as to have different dimensions in the radial direction, and the predetermined direction is the radial direction. Light head. 4. A light receiving element comprising: a first light receiving section for receiving a detection spot corresponding to the main spot; and a second and third light receiving section for receiving detection spots corresponding to the two sub spots, respectively. Wherein the first light receiving portion has first, second, and third divided regions divided into three in the radial direction, and the first divided region is disposed between the second and third regions. Wherein the second light receiving unit has fourth, fifth, and sixth divided regions each divided into three in the radial direction, and the fourth divided region is disposed between the fifth and sixth regions; The third light receiving unit has seventh, eighth, and ninth divided regions each divided into three in the radial direction, and the seventh divided region is disposed between the eighth and ninth regions. 4. The optical head according to claim 3, wherein: 5. The size of the main spot received by the first light receiving portion in the radial direction is W10, the size of the first divided region of the first light receiving portion in the radial direction is W11,
The radial dimension of the main spot received by the second light receiving section is W20, the radial dimension of the fourth divided region of the second light receiving section is W21, and the main spot is received by the third light receiving section. When the dimension of the main spot in the radial direction is W30 and the dimension of the seventh divided region of the third light receiving unit in the radial direction is W31, W11 / W10, W21 / W20, and W31 / W30 are substantially the same. The optical head according to claim 4, wherein the optical head is configured to: 6. A detection signal detected in each of the first to ninth divided areas is a first signal S1, a second signal S2, and a third signal S3.
Signal S3, fourth signal S4, fifth signal S5, sixth signal S
6, the seventh signal S7, the eighth signal S8, and the ninth signal S9, the tracking error signal TE becomes TE = (S2-
5. The optical head according to claim 4, wherein the calculation is performed as (S3) -K ((S4-S5) + (S7-S8)) (where K is a coefficient). 7. A land and a groove are formed on the information recording surface, and the optical recording medium is configured to record or reproduce information on at least one of the land and the groove. The optical head according to claim 4. 8. A detection signal detected in each of the first to ninth divided areas is a first signal S1, a second signal S2, and a third signal S2, respectively.
Signal S3, fourth signal S4, fifth signal S5, sixth signal S
6, the seventh signal S7, the eighth signal S8, and the ninth signal S9, when the land / groove determination signal CTS is CTS =
((S5 + S6) -S4)-((S8 + S9) -S7)
The optical head according to claim 7, wherein the land and groove are determined by the land / groove determination signal. 9. A detection signal detected in each of the divided areas of each of the light receiving units that has received the plurality of detection spots and output from each of the divided areas corresponding to each of the divided areas, 2. The optical head according to claim 1, wherein the optical head is configured to be able to determine a track area, a mirror area, an address pit area, and the like provided on the information recording surface based on a calculation result. 10. The plurality of converging spots include one main spot and at least one sub spot,
The main spot and the sub-spot are configured such that focusing positions in a direction of an optical axis of a light beam forming the main spot and the sub-spot are different from each other in a radial direction crossing a track of the optical recording medium; The main spot and the sub spot formed above are formed so as to have different dimensions in the radial direction, and the predetermined direction is the radial direction.
Optical head as described. 11. The light source has two or more light emitting points,
The optical head according to claim 10, wherein one light emitting point forms the main spot and another light emitting point forms the sub spot. 12. The light source has only one light emitting point,
11. The optical head according to claim 10, further comprising spot forming means for forming the main spot and the sub spot from one light beam emitted from the light emitting point. 13. An optical head according to claim 12, wherein said spot forming means is constituted by an optical diffraction element provided between said light source and said objective lens. 14. A light source for emitting a light beam, and light detecting means for receiving a reflected light beam reflected from the optical recording medium, wherein the light beam emitted from the light source causes the light beam on the information recording surface. At least one converging spot is formed, and a plurality of detecting spots are formed on the light detecting unit corresponding to the converging spot, and the light detecting unit is configured to detect the plurality of detecting spots. Each of the plurality of detection spots has a light receiving unit for receiving the plurality of detection spots corresponding thereto, and the plurality of detection spots are formed so that dimensions in a predetermined direction are different for each spot. In the state where the detection spot is formed over each of the divided areas of the light receiving unit, the size of the detection spot in the predetermined direction is configured. And a configuration in which the ratio of the dimension in the predetermined direction of each portion where the detection spot is formed in each of the divided regions is substantially the same between the light receiving units. Characteristic light receiving and emitting element. 15. A plurality of converging spots formed on the information recording surface by the light beam emitted from the light source, and the detection spot is formed corresponding to each of the plurality of converging spots. The light emitting / receiving element according to claim 14, wherein: 16. The plurality of light-condensing spots are composed of one main spot and two sub-spots, and the main spot and the two sub-spots are arranged in a radial direction crossing a track of the optical recording medium. Spot and 2
The focus positions of the light beams forming the two sub-spots in the optical axis direction are different from each other, and one of the two sub-spots is closer to the objective lens than the focus position of the main spot. And the in-focus position of the other of the two sub-spots is located farther from the objective lens than the in-focus position of the main spot, and the main focus formed on the information recording surface is Spot and 2
The light emitting / receiving element according to claim 15, wherein the two sub spots are formed so as to have different dimensions in the radial direction, and the predetermined direction is the radial direction. 17. A light receiving element, comprising: a first light receiving unit that receives a detection spot corresponding to the main spot;
And second and third light receiving units for receiving detection spots corresponding to the two sub-spots, respectively, wherein the first light receiving unit is divided into three in the radial direction, and the first, second, and third light receiving units are respectively divided into three.
A first divided region disposed between the second and third regions, wherein the second light receiving unit is divided into three in a radial direction, and the first divided region is divided into three in a radial direction. And the fourth divided region is disposed between the fifth and sixth regions, and the third light receiving unit is configured to divide the seventh, eighth, and ninth divided regions into three in the radial direction. The light emitting and receiving element according to claim 16, wherein the seventh divided region is disposed between the eighth and ninth regions. 18. The radial dimension of the main spot received by the first light receiving unit in the radial direction is W10, and the radial size of the first divided region of the first light receiving unit in the radial direction is W1.
1. The radial dimension of the main spot received by the second light receiving section is W20, the radial dimension of the fourth divided region of the second light receiving section is W21, and the main spot is received by the third light receiving section. When the dimension of the main spot in the radial direction is W30, and the dimension of the seventh divided region of the third light receiving unit in the radial direction is W31, W11 / W1
18. The light emitting and receiving device according to claim 17, wherein 0, W21 / W20, and W31 / W30 are configured to be substantially the same. 19. A detection signal detected in each of the first to ninth divided areas is a first signal S1, a second signal S2, a third signal S3, a fourth signal S4, a fifth signal S5, and a sixth signal S.
6, the seventh signal S7, the eighth signal S8, and the ninth signal S9, the tracking error signal TE becomes TE = (S2-
18. The light emitting and receiving element according to claim 17, wherein the calculation is performed as (S3) -K ((S4-S5) + (S7-S8)) (where K is a coefficient). 20. A land and a groove are formed on the information recording surface, and the optical recording medium is configured to record or reproduce information on at least one of the land and the groove. A light emitting / receiving element according to claim 17. 21. Detection signals detected in the first to ninth divided areas are respectively a first signal S1, a second signal S2, a third signal S3, a fourth signal S4, a fifth signal S5, a sixth signal S6,
When the seventh signal S7, the eighth signal S8, and the ninth signal S9 are set, the land / groove discrimination signal CTS becomes CTS = ((S5
21. The light emitting / receiving element according to claim 20, wherein the calculation is performed as (+ S6) -S4)-((S8 + S9) -S7). 22. Each of the detection signals detected in each of the divided regions of each of the light receiving units that have received the plurality of detection spots and output from each of the divided regions in correspondence with each of the divided regions is the detection signal of each of the detected signals. 15. The light emitting / receiving element according to claim 14, wherein the light emitting / receiving element is configured to be able to determine a track area, a mirror area, an address pit area, and the like provided on the information recording surface based on a calculation result. 23. The plurality of converging spots include one main spot and at least one sub spot.
The main spot and the sub-spot are configured such that focusing positions in a direction of an optical axis of a light beam forming the main spot and the sub-spot are different from each other in a radial direction crossing a track of the optical recording medium; 2. The main spot and the sub spot formed above are formed so as to have different dimensions in the radial direction, and the predetermined direction is the radial direction.
5. The light emitting and receiving element according to 5. 24. The light source has two or more light emitting points,
24. The light emitting and receiving device according to claim 23, wherein one light emitting point forms the main spot and another light emitting point forms the sub spot. 25. The light source has only one light emitting point,
24. The light emitting / receiving element according to claim 23, further comprising a spot forming means for forming the main spot and the sub spot from one light beam emitted from the light emitting point. 26. The light emitting / receiving element according to claim 25, wherein said spot forming means is constituted by an optical diffraction element provided between said light source and said objective lens. 27. A drive means for rotatingly driving an optical recording medium, an optical head for irradiating the rotating optical recording medium with a light beam and detecting a reflected light beam from an information recording surface of the optical recording medium. An optical recording medium recording / reproducing apparatus having a signal processing circuit for generating a reproduction signal based on a detection signal from the optical head, wherein the optical head includes a light source and light detection means, and the light source includes the light source. The light detecting means is configured to receive the reflected light beam and to output the detection signal, and the light beam emitted from the light source on the information recording surface. At least one converging spot is formed, and a plurality of detecting spots are formed on the light detecting unit corresponding to the converging spot, Each of the plurality of detection spots has a light receiving unit that receives the plurality of detection spots corresponding to each of the light spots, and the plurality of detection spots are formed so that dimensions in a predetermined direction are different for each spot. In the state where the detection spot is formed over each of the divided regions of the light receiving unit, the detection spot is formed in a plurality of divided regions in the predetermined direction, and the size of the detection spot in the predetermined direction and each of the divided regions is An optical recording medium recording / reproducing apparatus, wherein a ratio of a size of each portion where the detection spot is formed to the dimension in the predetermined direction is substantially the same between the light receiving units. . 28. A plurality of converging spots formed on the information recording surface by the light beam emitted from the light source, and the detection spots are formed corresponding to each of the plurality of converging spots. 28. The optical recording medium recording / reproducing apparatus according to claim 27, wherein: 29. The plurality of light-condensing spots are composed of one main spot and two sub-spots, and the main spot and the two sub-spots are arranged in a radial direction crossing a track of the optical recording medium. Spot and 2
The focus positions of the light beams forming the two sub-spots in the optical axis direction are different from each other, and one of the two sub-spots is closer to the objective lens than the focus position of the main spot. And the in-focus position of the other of the two sub-spots is located farther from the objective lens than the in-focus position of the main spot, and the main focus formed on the information recording surface is Spot and 2
29. The optical recording medium recording / reproducing apparatus according to claim 28, wherein the two sub spots are formed so as to have different dimensions in the radial direction, and the predetermined direction is the radial direction. 30. A light-receiving element, comprising: a first light-receiving unit for receiving a detection spot corresponding to the main spot;
And second and third light receiving units for receiving detection spots corresponding to the two sub-spots, respectively, wherein the first light receiving unit is divided into three in the radial direction, and the first, second, and third light receiving units are respectively divided into three.
A first divided region is disposed between the second and third regions, and the second light receiving unit is divided into three in a radial direction, and the first divided region is divided into three in a radial direction. And the fourth divided region is disposed between the fifth and sixth regions, and the third light receiving section is divided into seven, eighth, and ninth divided regions in the radial direction. 30. The optical recording medium recording / reproducing apparatus according to claim 29, wherein the seventh divided area is disposed between the eighth and ninth areas. 31. The radial dimension of the main spot received by the first light receiving portion in the radial direction is W10, and the radial size of the first divided region of the first light receiving portion in the radial direction is W1.
1. The radial dimension of the main spot received by the second light receiving section is W20, the radial dimension of the fourth divided region of the second light receiving section is W21, and the main spot is received by the third light receiving section. When the dimension of the main spot in the radial direction is W30, and the dimension of the seventh divided region of the third light receiving unit in the radial direction is W31, W11 / W1
31. The optical recording medium recording / reproducing apparatus according to claim 30, wherein 0, W21 / W20, and W31 / W30 are configured to be substantially the same. 32. A detection signal detected in each of the first to ninth divided areas is a first signal S1, a second signal S2, a third signal S3, a fourth signal S4, a fifth signal S5, and a sixth signal S.
6, the seventh signal S7, the eighth signal S8, and the ninth signal S9, the tracking error signal TE becomes TE = (S2-
31. The optical recording medium recording / reproducing apparatus according to claim 30, wherein the calculation is performed as (S3) -K ((S4-S5) + (S7-S8)) (where K is a coefficient). 33. A land and a groove are formed on the information recording surface, and the optical recording medium is configured to record or reproduce information on at least one of the land and the groove. The optical recording medium recording / reproducing apparatus according to claim 30. 34. A detection signal detected in each of the first to ninth divided areas is a first signal S1, a second signal S2, a third signal S3, a fourth signal S4, a fifth signal S5, a sixth signal S6, respectively.
When the seventh signal S7, the eighth signal S8, and the ninth signal S9 are set, the land / groove discrimination signal CTS becomes CTS = ((S5
34. The optical recording medium recording / reproducing apparatus according to claim 33, wherein the calculation is performed as (+ S6) -S4)-((S8 + S9) -S7), and the land and groove are determined by the land / groove determination signal. 35. Each detection signal detected in each of the divided areas of each of the light receiving units that has received the plurality of detection spots and output from each of the divided areas in correspondence with each of the divided areas, 28. The optical recording medium recording / reproducing apparatus according to claim 27, wherein it is possible to determine a track area, a mirror area, an address pit area, and the like provided on the information recording surface based on a calculation result. apparatus. 36. The plurality of converging spots include one main spot and at least one sub spot,
The main spot and the sub-spot are configured such that focusing positions in a direction of an optical axis of a light beam forming the main spot and the sub-spot are different from each other in a radial direction crossing a track of the optical recording medium; The main spot and the sub spot formed above are formed so as to have different dimensions in the radial direction, and the predetermined direction is the radial direction.
9. The optical recording medium recording and reproducing apparatus according to 8. 37. The light source has two or more light emitting points,
37. The optical recording medium recording / reproducing apparatus according to claim 36, wherein one light emitting point forms the main spot, and another light emitting point forms the sub spot. 38. The light source has only one light emitting point,
37. The optical recording medium recording / reproducing apparatus according to claim 36, further comprising spot forming means for forming the main spot and the sub spot from one light beam emitted from the light emitting point. 39. An optical recording medium recording / reproducing apparatus according to claim 38, wherein said spot forming means is constituted by an optical diffraction element provided between said light source and said objective lens. 40. A driving means for rotatingly driving an optical recording medium, an optical head for irradiating the rotating optical recording medium with a light beam and detecting a reflected light beam from an information recording surface of the optical recording medium. An optical recording medium recording / reproducing apparatus having a signal processing circuit for generating a reproduction signal based on a detection signal from the optical head, wherein the optical head comprises a receiving lens provided with an objective lens, a light source, and light detecting means. A light-emitting element, wherein the light source is configured to emit the light beam, and the light detection unit is configured to receive the reflected light beam and output the detection signal, and is emitted from the light source. At least one light spot formed on the information recording surface by the light beam, and a plurality of detection spots corresponding to the light spot on the light detection means. Is formed, and the light detecting means has a light receiving unit for receiving the plurality of detection spots corresponding to each of the condensed spots, and the plurality of detection spots have different dimensions in a predetermined direction for each spot. Each of the light receiving sections is formed of a plurality of divided areas divided in the predetermined direction, and in a state where the detection spot is formed over each of the divided areas of the light receiving section, The ratio between the dimension in the direction and the dimension in the predetermined direction of each portion where the detection spot is formed in each of the divided areas is configured to be substantially the same between the light receiving units. An optical recording medium recording / reproducing apparatus characterized by the above-mentioned. 41. A plurality of converging spots formed on the information recording surface by the light beam emitted from the light source, and the detection spots are formed corresponding to each of the plurality of converging spots. 41. The optical recording medium recording / reproducing apparatus according to claim 40, wherein: 42. The plurality of converging spots are composed of one main spot and two sub spots, and the main spot and the two sub spots are arranged in a radial direction crossing a track of the optical recording medium. Spot and 2
The focus positions of the light beams forming the two sub-spots in the optical axis direction are different from each other, and one of the two sub-spots is closer to the objective lens than the focus position of the main spot. And the in-focus position of the other of the two sub-spots is located farther from the objective lens than the in-focus position of the main spot, and the main focus formed on the information recording surface is Spot and 2
42. The optical recording medium recording / reproducing apparatus according to claim 41, wherein the two sub spots are formed so as to have different dimensions in the radial direction, and the predetermined direction is the radial direction. 43. A light-receiving element, comprising: a first light-receiving unit for receiving a detection spot corresponding to the main spot;
And second and third light receiving units for receiving detection spots corresponding to the two sub-spots, respectively, wherein the first light receiving unit is divided into three in the radial direction, and the first, second, and third light receiving units are respectively divided into three.
A first divided region is disposed between the second and third regions, and the second light receiving unit is divided into three in a radial direction, and the first divided region is divided into three in a radial direction. And the fourth divided region is disposed between the fifth and sixth regions, and the third light receiving unit is configured to divide each of the seventh, eighth, and ninth divided regions in the radial direction into three. 43. The optical recording medium recording / reproducing apparatus according to claim 42, wherein the seventh divided area is disposed between the eighth and ninth areas. 44. The radial dimension of the main spot received by the first light receiving portion in the radial direction is W10, and the radial size of the first divided region of the first light receiving portion in the radial direction is W1.
1. The radial dimension of the main spot received by the second light receiving section is W20, the radial dimension of the fourth divided region of the second light receiving section is W21, and the main spot is received by the third light receiving section. When the dimension of the main spot in the radial direction is W30, and the dimension of the seventh divided region of the third light receiving unit in the radial direction is W31, W11 / W1
The optical recording medium recording / reproducing apparatus according to claim 43, wherein 0, W21 / W20, and W31 / W30 are configured to be substantially the same. 45. A detection signal detected in each of the first to ninth divided areas is a first signal S1, a second signal S2, a third signal S3, a fourth signal S4, a fifth signal S5, a sixth signal S6, respectively.
When the seventh signal S7, the eighth signal S8, and the ninth signal S9 are set, the tracking error signal TE becomes TE = (S2-S
3) The calculation is performed as -K ((S4-S5) + (S7-S8)) (where K is a coefficient).
4. The optical recording medium recording / reproducing apparatus according to 3. 46. A land and a groove are formed on the information recording surface, and the optical recording medium is configured to record or reproduce information on at least one of the land and the groove. An optical recording medium recording / reproducing apparatus according to claim 43. 47. A detection signal detected in each of the first to ninth divided areas is a first signal S1, a second signal S2, a third signal S3, a fourth signal S4, a fifth signal S5, a sixth signal S6, respectively.
When the seventh signal S7, the eighth signal S8, and the ninth signal S9 are set, the land / groove discrimination signal CTS becomes CTS = ((S5
47. The optical recording medium recording / reproducing apparatus according to claim 46, wherein the calculation is performed as (+ S6) -S4)-((S8 + S9) -S7), and the land and groove are determined by the land / groove determination signal. 48. Each of the detection signals detected in each of the divided regions of each of the light receiving units that have received the plurality of detection spots and output from each of the divided regions in correspondence with each of the divided regions is the same as that of each of the detected signals. 41. The optical recording medium recording / reproducing apparatus according to claim 40, wherein it is configured to be able to determine a track area, a mirror area, an address pit area, and the like provided on the information recording surface based on a calculation result. apparatus. 49. The plurality of converging spots are composed of one main spot and at least one sub spot.
The main spot and the sub-spot are configured such that focusing positions in the optical axis direction of light beams forming the main spot and the sub-spot are different from each other in a radial direction crossing a track of the optical recording medium, and 5. The apparatus according to claim 4, wherein the main spot and the sub spot formed thereon are formed to have different dimensions in the radial direction, and the predetermined direction is the radial direction.
2. The optical recording medium recording and reproducing apparatus according to 1. 50. The light source has two or more light emitting points,
50. The optical recording medium recording / reproducing apparatus according to claim 49, wherein one light emitting point forms the main spot, and another light emitting point forms the sub spot. 51. The light source has only one light emitting point,
50. The optical recording medium recording / reproducing apparatus according to claim 49, further comprising spot forming means for forming the main spot and the sub spot from one light beam emitted from the light emitting point. 52. An optical recording medium recording / reproducing apparatus according to claim 51, wherein said spot forming means is constituted by an optical diffraction element provided between said light source and said objective lens.