JP2003272190A - Optical pickup and optical information recording/ reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical pickup which has a new tracking error signal detection means which excellently detects a tracking error signal for all optical disks which have a plurality of different kinds in which guiding groove pitches are remarkably different while keeping the offset decreasing effect of a tracking error signal as much as a conventional DPP system, and to provide an optical information recording/reproducing device. <P>SOLUTION: The optical pickup is provided with a laser light source 1, a light branching element 2 which branches laser light emitted from the laser light source 1 into at least three light beams, a focusing optical system 5 which focuses the three light beams with which mutually independent three focused spots are irradiated on the recording face of an optical information recording medium 10 on which the guiding grooves are provided at a prescribed period, and a light detector 20 which independently receives the reflected light beams from the three light spots on the optical information recording medium 10. The distance between two adjacent focused spots among three focused spots in the direction which substantially diagonally crosses the guiding grooves is 0.25 to 0.75 times (except 0.5 times) the period of the guiding grooves. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information signal recorded on an optical information recording medium (hereinafter referred to as "optical disc" for simplicity) recorded on the optical disc by a light spot irradiated on the recording surface. The present invention relates to an optical pickup having a function of reproducing or recording information and an optical information recording or reproducing apparatus equipped with the optical pickup, and is an invention particularly effective for improving the reliability and versatility of the tracking error signal detecting means. .

[0002]

2. Description of the Related Art In general, an optical pickup detects a focus error signal and a tracking error signal in order to correctly irradiate a focused spot on a predetermined recording track in an optical disk, and uses these control signals to detect the objective lens. It is configured to perform position control. Of these, as a tracking error signal detection method, a three-beam method, a push-pull method, a differential push-pull method (hereinafter, referred to as “DPP method” for simplicity), etc. are often used as typical detection methods. There is.

In particular, the DPP method can detect a highly sensitive tracking error signal with a relatively simple detection optical system, and can satisfactorily reduce the offset of the tracking error signal due to the displacement of the objective lens or the tilt of the optical disk. This method is advantageous and has been widely adopted in recent years in optical pickups for write-once or rewritable optical disks.

Here, the signal detection principle of the DPP method will be briefly described. In the DPP method, a light beam emitted from a laser light source is divided into three light beams by a light splitting element such as a diffraction grating, and each of the light beams is condensed by an objective lens, so that each of them is formed on an optical disk 10 as shown in FIG. Irradiate three independent focused spots 100, 101, and 102. At this time, these three focused spots 100, 101,
Reference numeral 102 denotes the irradiation position interval δ of the focused spots in the radial direction of the optical disc 10, that is, the direction in which the guide grooves 11 periodically provided on the optical disc 10 are vertically crossed.
The irradiation position is strictly adjusted so as to coincide with one half of the pitch Tp of the guide groove 11. Then, the optical disk reflected light of each condensing spot is, for example, as shown in the drawing, a multi-segment photodetector 20 provided in an optical pickup.
The light is incident on the three two-divided or four-divided light-receiving surfaces 20a, 20b, 20c arranged inside to form detection light spots 200, 201, 202, respectively. Then, the photoelectric conversion signals from the respective light receiving surfaces are subtracted from the subtracters 50a, 50
By subtraction processing by b and 50c respectively,
A tracking error signal (hereinafter referred to as "push-pull signal" for simplicity) by the push-pull method is detected for each detected light spot.

At this time, the detection light spot corresponding to the focused spot 100 on the optical disk 10 is set to 200, and the detected light spots corresponding to the focused spots 101 and 102 are set to 201 and 202, respectively. As shown in the figure, the signals Sa, Sb,
Let Sc be the focused spots 100, 1 on the optical disc.
From the positional relationship between 01 and 102, it is clear that Sa, Sb, and Sc
, The push-pull signals are out of phase with each other by about 180 °. That is, push-pull signals Sa, Sb and Sa
And Sc are output with their signal waveforms in opposite phases. (Sb and Sc have the same phase.) Therefore, this signal S
Even if Sb and Sc are subtracted from a, the signal component is not canceled and can be increased. On the other hand, with respect to the offset component of the push-pull signal generated due to the displacement of the objective lens or the inclination of the optical disc, all of Sa, Sb, and Sc have the same polarity.

Therefore, the offset components can be canceled out by the subtraction process.

Therefore, for example, the push-pull signals Sb and S
c is added by the adder 51, and the added signal is appropriately amplified by the amplifier 52 in order to compensate for the difference in signal amplitude caused by the difference in the light amount of the focused spots 100 and 101 and 102. By performing the subtraction process from the push-pull signal Sa by the subtractor 53, it is possible to obtain the tracking error signal in which the offset component included in the push-pull signal Sa is satisfactorily removed.

The above is a schematic description of the detection principle of the DPP method. The DPP method is disclosed in, for example, Japanese Patent Laid-Open No. 7-2
Since this is a known technique disclosed in Japanese Patent Publication No. 72303, etc., detailed description thereof will be omitted.

[0009]

As described above, the DPP method is capable of detecting a highly sensitive tracking error signal with a relatively simple detection optical system, and also causes displacement of the objective lens or tilt of the optical disk. This is a very effective tracking error signal detection method especially for discs with periodic guide grooves such as write-once and rewritable optical discs. .

On the other hand, however, this DPP system also has the following practical problems. That is, in the DPP method, as described above, the three focused spots irradiated on the optical disc are strictly separated from each other in the radial direction of the optical disc by an interval δ corresponding to one half of the recording guide groove pitch Tp. Need to be irradiated. Therefore, when reproducing or recording a plurality of types of optical discs having different guide groove pitches, a good tracking error signal is detected for an optical disc whose guide groove pitch deviates greatly from twice the focused spot interval. You will not be able to do it.

For example, as a write-once or rewritable DVD-based optical disc, which is currently in rapid demand, D
There are VD-RAM, DVD-R, DVD-RW, etc. Among them, DVD-RAM has a guide groove pitch of about 1.48 μm (RAM1) and 1.23 mm.
There are two types of μm type (RAM2). on the other hand,
DVD-R and DVD-RW guide groove pitch is 0.7
At 4 μm, it is about half the pitch of the guide groove of DVD-RAM.

Therefore, in the conventional DPP system, the DV
If the arrangement interval of the three converging spots is adjusted so that the optimum tracking error signal can be detected on the D-RAM disk, it will be 3 when reproducing or recording on a DVD-R or a DVD-RW disk. The arrangement interval of the individual focused spots becomes almost equal to the guide groove pitch of the disc itself, which makes it difficult to detect the tracking error signal by the DPP method. As described above, when the same optical pickup is used for a plurality of types of optical discs having different guide groove pitches, it may be difficult to detect a good tracking error signal by using the conventional DPP method depending on the combination of the discs. It may become

In view of such a situation, in the present invention, while maintaining the same offset reduction effect of the tracking error signal as the conventional DPP method, it is good for all of a plurality of types of optical discs having greatly different guide groove pitches. Another object of the present invention is to provide an optical pickup and an optical information recording / reproducing apparatus equipped with a new tracking error signal detecting means capable of detecting various tracking error signals.

[0014]

In order to solve the above-mentioned problems, the present invention provides a laser light source, an optical branching element for branching laser light emitted from the laser light source into at least three light beams, and the above-mentioned three light beams. Optical system for converging the optical beam of 3 and irradiating three independent converging spots on the recording surface of the optical information recording medium provided with guide grooves at a predetermined cycle, An optical pickup that independently receives reflected light from the optical information recording medium of each of the three light spots, between two adjacent light spots among the three light spots. In the optical pickup, the distance between the irradiation positions in the direction substantially crossing the guide groove is 0.25 to 0.75 times (excluding 0.5 times) the cycle of the guide groove.

Further, according to the present invention, an irradiation position interval in a direction substantially perpendicular to the guide groove between two adjacent condensed spots among the three condensed spots is 0 when the guide groove period is 0. 25 times to 0.45 times or 0.55 times
The optical pickup has a distance of 0.75 times.

Further, according to the present invention, a laser light source, an optical branching element for branching a laser beam emitted from the laser light source into at least three light beams, and a predetermined different light beam condensing the three light beams. A condensing optical system that irradiates three independent condensing spots on each recording surface of an n-type optical information recording medium in which guide grooves are provided at regular intervals, and each of the three optical spots described above. In an optical pickup including a photodetector that independently receives reflected light from a physical information recording medium, each of the guide grooves between two adjacent condensed spots among the three condensed spots is formed. (M _i +0.25) × Tp _i for all i satisfying 1 ≦ i ≦ n between the irradiation position interval δ in the substantially vertical direction and the period Tp _i of the guide groove of the optical information recording medium. ≤ δ ≤ (m _i
+0.45) × Tp _i or (m _i +0.55) × Tp _i ≦
δ ≦ (m _i +0.75) × Tp _i where m _i is an optical pickup for which the relational expression of 0 or a positive integer holds.

Further, according to the present invention, the irradiation position interval δ and the optical information recording medium in the direction of substantially perpendicularly crossing each of the guide grooves between two adjacent focused spots among the three focused spots. During the period Tp _i of the guide groove of
The optical pickup has a relational expression of 0.38 μm ≦ δ ≦ 0.55 μm.

Further, according to the present invention, a laser light source, an optical branching element for branching a laser beam emitted from the laser light source into at least three light beams, and a predetermined optical system for condensing the three light beams. A condensing optical system that irradiates three independent condensing spots on the recording surface of the information recording medium, and individually receives the reflected lights of the three optical spots from each optical information recording medium. In an optical pickup equipped with a photodetector, an irradiation position interval in the direction of substantially perpendicularly crossing the guide grooves between two adjacent focused spots of the three focused spots is 0.45 μm or more. The optical pickup is in the range of 0.55 μm or less.

The present invention includes the optical pickup described above, and tracking for detecting at least a tracking error signal by the differential push-pull method from the photoelectric conversion signal output from the photodetector in the optical pickup. The optical information recording / reproducing apparatus includes an error signal detection circuit.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described.
Embodiments of the optical pickup and the optical information recording / reproducing apparatus of the present invention will be described below with reference to FIGS.
FIG. 1 is a schematic front view of an example of an optical system in the optical pickup of the embodiment. FIG. 2 is a layout diagram of a focused spot on an optical disk and a schematic connection diagram of a detection system for explaining a tracking error signal detection method in the embodiment. Figure 3
FIG. 4 is a diagram showing a relationship between a focus spot interval and a detected tracking error signal amplitude in the example. Figure 4
FIG. 6 is a diagram showing an example of a relationship between a focused spot interval and tracking error signal amplitudes detected for a plurality of types of optical discs in the example. FIG. 5 is a schematic enlarged view of the disk recording surface showing a specific example of the relationship between the guide groove and the focused spot irradiation position of a plurality of types of optical disks in the embodiment.

An example will be described. The optical system of the optical pickup of this embodiment has, for example, a wavelength of 650 as shown in FIG.
A semiconductor laser light source 1 that emits a laser beam in the nm band, a diffraction grating 2, a beam splitter 3, a collimator lens 4, an objective lens 5, a detection lens 6, and a multi-segment photodetector 20 are provided.

When passing through the diffraction grating 2, the laser light flux emitted from the semiconductor laser 1 is separated into at least three light fluxes of 0th-order light and ± 1st-order diffracted light. Then, these three light beams are reflected by the beam splitter 3, pass through the collimator lens 4 and the objective lens 5, and are focused on the recording surface of a predetermined optical disc 10 to form three independent focused spots. Form. Then, the disk reflected light of each focused spot reverses the almost same optical path as the forward path, reaches the beam splitter 3 via the objective lens 5 and the collimator lens 4, and then a part of the light amount thereof passes through the beam splitter 3. The light is incident on each light receiving surface of the multi-segment photodetector 20 through the detection lens 6. Then, various servo signals such as a focus error signal and a tracking error signal and information signals recorded on the optical disk 10 are reproduced from the signals detected on the respective light receiving surfaces of the multi-division photo detector.

FIG. 2 is a diagram showing an outline of the irradiation position relationship between the focused spot on the optical disk and the guide groove periodically provided on the disk and the tracking error signal detection processing circuit in this embodiment. In this embodiment, the conventional D
Unlike the PP method, the focused spot 1 on the optical disk 10
00, 101, and 102 are radial directions of the optical disc 10.
That is, the irradiation position interval (hereinafter, this interval is simply referred to as "focus spot interval") δ between the focus spots in the direction perpendicular to the guide groove 11 provided on the optical disk. , The period Tp of the guide groove 11 is 4
The irradiation position is adjusted so as to substantially match 3/3.
Of the three focused spots, it is the central focused spot 100 that actually reproduces or records the information signal. (Hereinafter, for the sake of simplicity, the focused spot 100 will be referred to as a "main spot", and the focused spots 101 and 102 arranged on both sides thereof will be referred to as "side spots.")

Similar to the conventional DPP method described with reference to FIG. 2, the optical disk reflected light of each converging spot arranged in this way is divided into three 2 pieces arranged in the multi-segment photodetector 20.
The push-pull signals Sa, Sb, Sc are detected for each light spot by receiving light by the split or quadrant light receiving surfaces 20a, 20b, 20c and performing subtraction processing by the subtractors 50a, 50b, 50c, respectively. The push-pull signals Sa, Sb, and Sc are usually offsets caused by displacement of the objective lens, tilt of the optical disc, and the like in the tracking error component that fluctuates in proportion to the amount of displacement of the focused spot relative to the disc guide groove. It is output with the components added.

By the way, in this embodiment, the interval δ of the focused spots on the disc is the period Tp of the disc guide groove 11.
Of the detected push-pull signals Sa, Sb, Sc among the detected push-pull signals Sa, Sb, Sc with respect to the tracking error component included in the push-pull signal Sa detected from the main spot 100. Spot 10
The tracking error component included in the push-up signal Sb detected from 1 is output with the phase shifted by + 270 °, and the phase of the tracking error component included in the push-up signal Sc detected from the side spot 102 is shifted by −270 °. Is output in the closed state. That is, the tracking error components included in each of the push-pull signals Sb and Sc have a phase of 540 °, that is, 18
The signal waveform is completely out of phase with 0 °. On the other hand, the offset components included in the signals Sa, Sb, and Sc are always in phase regardless of the position of each focused spot.

Therefore, in such a state, the conventional DP
Similar to the P method, when the signals Sb and Sc are added by the adder 51, the tracking error components included in the signals cancel each other and are canceled, and only the offset component remains and is added and output as the signal Sd. It will be. Then, after the signal Sd is amplified by the amplifier 52 at a predetermined amplification factor, the push-pull signal S detected from the main spot 100 by the subtractor 53.
By subtracting from a, it is possible to detect a good tracking error signal in which only the offset component is removed from the signal Sa.

As described above, when the tracking error signal is detected by the same calculation processing as in the conventional DPP method, the spot interval δ of the three focused spots irradiated on the optical disk is the guide groove of the disk as in the conventional case. Period Tp
It is not limited to 1/2.

That is, now, when an arbitrary optical disk provided with a guide groove at a predetermined period Tp is irradiated with three converging spots having a converging spot interval of δ, the embodiment of FIG. 2 has been described. The amplitude P of the tracking error signal detected by the same calculation as the calculation method (the relative value when the amplitude of the tracking error signal detected by the conventional DPP method is 1) is expressed as follows.

[0029]     P = 0.5 × {1-cos [2π × (S / Tp)]} (1)

FIG. 3 is a graph showing the focus spot interval δ (expressed as a relative value to the optical disc guide groove period Tp) and the tracking error signal obtained by the same calculation process as described above using the equation (1). It is the diagram which showed the relationship of the amplitude P (it shows with the relative value when the amplitude of the tracking error signal detected by the conventional DPP method is set to 1). For example, the shaded area in the figure is an area where the amplitude of the detected tracking error signal can be secured to be 0.5 times or more of the tracking error signal amplitude obtained by the conventional DPP method, and this is an acceptable optical disc system. Assuming that the range is possible, the condensing spot interval δ is in the range of 1/4 (0.25 times) to 3/4 (0.75 times) of the guide groove period Tp of the disk (excluding 1/2 or 0.5 times)
It will be good if you are inside. On the other hand, the offset components included in the push-pull signal obtained from each focused spot are always in phase with each other regardless of the positional relationship between the focused spot and the disc guide groove. It can be removed well. Therefore, it is not necessary that the spot distances δ of the three focused spots irradiated on the optical disc be exactly 1/2 of the guide groove period Tp, as long as δ is within the above allowable range. For example, it is possible to detect a good tracking error signal from which the offset component has been removed, regardless of the spacing.

In addition, if a predetermined allowable width can be set in the irradiation position interval of the three converging spots irradiated on the optical disk in this way, the same optical pickup, that is, a plurality of different converging spots having different guide groove periods. It can be applied to various types of optical disks.

Now, arbitrary guide groove periods Tp1 different from each other
For two types of optical discs each having Tp2 and Tp2, the irradiation positions of the three converging spots irradiated on each optical disc by the same optical pickup are defined by the following formula (m + 0.25) × Tp1. ≦ δ ≦ (m + 0.75) × Tp1 (2) and (n + 0.25) × Tp2 ≦ δ ≦ (n + 0.75) × Tp2 (3) where m and n satisfy predetermined integer values (excluding m + 0.
5, n + 0.5), the same optical pickup is used, and more than half of the tracking error signal amplitude obtained by the conventional DPP method is secured for both optical disks, and the conventional DPP method is used. Similar to the method, it is possible to obtain a good tracking error signal in which the offset component caused by the displacement of the objective lens or the tilt of the optical disc is sufficiently removed. As a matter of course, the above relational expression is not applied only to two types of optical discs having different guide groove periods, and the same applies to three or more types of optical discs having different guide groove periods. By setting the condensing spot interval δ so as to satisfy the relational expression, a good tracking error signal can be detected for each optical disc by the same optical pipac.

For example, a recording type DV currently commercialized
D-type optical discs include DVD-R, DVD-RW,
There are at least three types of discs such as DVD-RAM. Among them, the guide groove period Tp of the DVD-R and the DVD-RW is 0.74 μm, and the recording capacity of the DVD-RAM disc is 2.6 GB. DVD-RAM1
The disc has Tp = 1.48 μm and a recording capacity of 4.7 GB D.
The VD-RAM2 disk has Tp = 1.23 μm and at least three kinds of guide groove periods.

FIG. 4 shows a focus spot interval δ when the DVD disc is reproduced, and an amplitude P of the tracking error signal detected at that time by the same calculation as the calculation method described in FIG. 3 (conventional DPP). FIG. 3 is a diagram showing a relationship (displayed as a relative value when the amplitude of the tracking error signal detected by the method is 1). (A) in the figure is a DVD
-R / RW, (b) DVD-RAM1, (c) DV
The case where each D-RAM2 disc is reproduced is shown.

As can be seen from the figure, when the condensing spot interval δ is set in the range of about 0.4 μm to about 0.55 μm (hatched portion in the figure), the same condensing spot is used for any of the above disks. However, a tracking error signal detected by the conventional DPP method (condensing spot interval for each disc is ½ of the guide groove period Tp of the disc).
(A tracking error signal obtained by strictly setting the amplitude to more than half of the amplitude), and a good tracking signal in which the offset component caused by the displacement of the objective lens or the tilt of the optical disc is removed is secured. Obtainable.

By the way, in the optical pickup having the structure shown in the embodiment of FIG. 1, the astigmatism method is most commonly used as the method of detecting the focus error signal. However, DVD-RAM1 and DVD-R
In a RAM type optical disc such as AM2, a relatively large push-pull signal component is output due to the diffraction phenomenon of the guide groove, so that the push-pull signal component also leaks into the focus error signal detected by the astigmatism method. There is a problem that this becomes a disturbance of the focus error signal and deteriorates the signal quality.

Recently, in order to avoid the problem of leakage in the astigmatism focus detection system, the focus error signal of each of the three focused spots is used and the leakage error is calculated by processing it. A differential astigmatism method for eliminating has been proposed and put into practical use. This differential astigmatism method has already been disclosed in detail in Japanese Patent Laid-Open No. 4-168631 and Japanese Patent Laid-Open No. 2000-82226, so a detailed description thereof will be omitted, but this method is effective. To achieve this, the tracking error signal component obtained from the sub-spot needs to be detected with a sufficiently large amplitude. For example, in the example of FIG. 5, in order to obtain a focus error signal in which a leak component is satisfactorily removed by using the differential astigmatism method when reproducing a DVD-RAM system disc, tracking of each of the DVD-RAM 1 and the DVD-RAM 2 is performed. Error signal amplitude P is at least DP
7 of the optimum tracking error signal amplitude obtained by the P method
It is desirable to be able to secure 0% or more. For that purpose, as is clear from FIG. 4, the condensing spot interval δ is about 0.4.
It is necessary to set in the range of 5 μm to 0.55 μm.

Now, for example, the condensing spot interval δ is set to 0.55.
If it is set to μm, the relationship between the focused spots 100, 101, 102 on the optical disk and the disk guide groove 11 at this time is as shown in FIG. That is, when the optical disc is a DVD-R or a DVD-RW disc, as shown in FIG.
= 0.55 μm corresponds to almost 0.75 times (= 3/4) the guide groove period Tp1 = 0.74 μm. Therefore,
By the same calculation process as the calculation method described in the embodiment of FIG. 2, a good tracking error signal from which the offset component is removed can be obtained. On the other hand, the optical disc is a DVD-RAM
1 (guide groove period Tp2 = 1.48 μm) or DVD-
In the case of a RAM2 (guide groove period Tp3 = 1.23 μm) disk, even if the same focused spot arrangement is used, the interval δ
= 0.55 μm is 0.37 times and 0.45 times the respective guide groove pitches as shown in FIGS. 5 (b) and 5 (c), which are close to half the guide groove pitch.
By the same detection method as the conventional DPP method, the conventional D
It is possible to obtain a good tracking error signal that is almost the same as the tracking error signal obtained by the PP method.

Naturally, the present invention is not limited to the optical pickup having the structure shown in FIG. 1, and at least two or more condensed spots of the main spot and the sub-spots are irradiated onto the optical disc. The optical pickup can be applied to any optical pickup as long as it can detect a tracking error signal. Therefore, for example, two laser light sources with different wavelengths are mounted in the same optical pickup case, and the same optical pickup is used as a multi-disc compatible optical pickup capable of recording or reproducing both a DVD disc and a CD disc. Of course, the present invention can also be applied to a Blu-ray disc (track pitch 0.32 μm) using a blue-violet laser. .

As described above, according to the present invention, the same optical pickup is used, and the offset component caused by the displacement of the objective lens or the inclination of the disc can be favorably applied to a plurality of types of optical discs having different guide groove periods. The removed tracking error signal with good signal quality can be detected, and the performance and reliability of the optical pickup compatible with the multi-disc can be improved.

The irradiation position interval δ in the present invention is 0.25 to 0.45 times, 0.55 times to 0.75 times, or 0.25 times to the period Tp of the guide groove.
It is preferably 0.4 times or 0.6 times to 0.75 times.

[0042]

According to the present invention, while maintaining the same tracking error signal offset reduction effect as the conventional DPP method, a good tracking error signal can be obtained for all of a plurality of types of optical discs having greatly different guide groove pitches. It is possible to obtain an optical pickup and an optical information recording / reproducing apparatus equipped with a new tracking error signal detecting means capable of detecting

[Brief description of drawings]

FIG. 1 is a schematic front view of an example of an optical system in an optical pickup according to an embodiment.

FIG. 2 is a layout diagram of condensed spots on an optical disk and a schematic connection diagram of a detection system for explaining a tracking error signal detection method in an embodiment.

FIG. 3 is a diagram showing a relationship between a focus spot interval and a detected tracking error signal amplitude in the example.

FIG. 4 is a diagram showing an example of a relationship between a focus spot interval and tracking error signal amplitudes detected for a plurality of types of optical discs in the embodiment.

FIG. 5 is a schematic enlarged view of a disk recording surface showing a specific example of the relationship between the guide groove and the focused spot irradiation position of a plurality of types of optical disks in the embodiment.

FIG. 6 is a layout diagram of focused spots on an optical disk and a schematic connection diagram of a detection system in a conventional DPP method.

[Explanation of symbols]

1 Semiconductor laser light source 2 diffraction grating 5 Objective lens 10 optical disc 11 guide groove 20 photo detector 100 main spots 101, 102 sub-spot 200, 201, 202 Spot on the detection surface

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenichi Shimada             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Hitachi Digital Media Development Book             Department F-term (reference) 5D118 AA14 AA18 AA26 BA01 CC12                       CD03 CF16 CG04 CG24 CG44                       CG47                 5D119 AA29 AA41 BA01 EA02 EB03                       EB14 EC41 EC44 EC46 JA22                 5D789 AA29 AA41 BA01 EA02 EB03                       EB14 EC41 EC44 EC46 JA22

Claims (6)

[Claims] 1. A laser light source, an optical branching element for branching laser light emitted from the laser light source into at least three light beams, and a guide groove for converging the three light beams at a predetermined cycle. A condensing optical system that irradiates three independent condensing spots on the recording surface of the provided optical information recording medium, and a reflected light from the optical information recording medium of the three light spots are provided. In an optical pickup including a photodetector that receives light independently of each other, an irradiation position interval in a direction that substantially perpendicularly crosses the guide groove between two adjacent condensed spots among the three condensed spots is set. 0.25 to 0.7 times the period of the guide groove
An optical pickup having a distance of 5 times (excluding 0.5 times). 2. The optical pickup according to claim 1, wherein an irradiation position interval in a direction substantially perpendicular to the guide groove between two adjacent focused spots of the three focused spots is the guide position. 0.25 times the groove period to 0.4
An optical pickup having a distance of 5 times or 0.55 times to 0.75 times. 3. A laser light source and a laser emitting the laser light source.
Light splitting element for splitting laser light into at least three light beams
Child and the above-mentioned three light beams are converged and different from each other.
N kinds of optical information recording media provided with guide grooves at regular intervals
Irradiate three independent focused spots on each recording surface of
Focusing optical system and each of the three optical spots
Optical detection that receives the reflected light from the optical information recording medium independently.
In the optical pickup equipped with the output device, Two condensing spots adjacent to each other among the three condensing spots
Set the guide groove between the spots in the direction that crosses the guide groove substantially vertically.
Irradiation position interval δ and the guide groove of the optical information recording medium
Period Tp_iFor all i satisfying 1 ≦ i ≦ n
about, (M_i+0.25) × Tp_i≤ δ ≤ (m_i+0.45) ×
Tp_i Or (M_i+0.55) x Tp_i≤ δ ≤ (m_i+0.75) ×
Tp_i However, m_iIs a relational expression of 0 or a positive integer.
An optical pickup characterized by. 4. The optical pickup according to claim 3, wherein an irradiation position interval δ in a direction of substantially perpendicularly crossing each of the guide grooves between two adjacent focused spots of the three focused spots. An optical pickup characterized in that a relational expression of 0.38 μm ≦ δ ≦ 0.55 μm is satisfied during a period Tp _i of the guide groove included in the optical information recording medium. 5. A laser light source, an optical branching element for branching the laser light emitted from the laser light source into at least three light beams, and a predetermined optical information recording medium for condensing the three light beams. A condensing optical system that irradiates three independent condensing spots on the recording surface, and a photodetector that independently receives reflected light from each of the optical information recording media of the three light spots. In an optical pickup equipped with, the irradiation position interval in the direction of substantially perpendicularly crossing each of the guide grooves between two adjacent focused spots among the three focused spots is 0.45 μm or more and 0.55 μm or less. An optical pickup characterized by being in the range. 6. An optical pickup according to any one of claims 1 to 5, and a tracking error based on at least a differential push-pull method from a photoelectric conversion signal output from the photodetector in the optical pickup. An optical information recording / reproducing apparatus comprising a tracking error signal detection circuit for detecting a signal.