JP3356492B2 - Optical head device, optical information reproducing method, and optical information device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device for recording / reproducing or erasing information stored on an optical medium or a magneto-optical medium such as an optical disk or an optical card, and an optical medium such as an optical disk or an optical card. Alternatively, the present invention relates to an optical information reproducing method for reproducing information stored on a magneto-optical medium, and an optical information device using the same.

[0002]

2. Description of the Related Art Optical memory technology using an optical disk having a pit pattern as a high-density and large-capacity storage medium includes digital audio disks, video disks,
It has been put to practical use while expanding the use of document file disks and data files. The mechanism by which the recording and reproduction of information on an optical disk through a minutely focused light beam is successfully performed with high reliability depends solely on the optical system. The basic functions of the optical head device, which is the main part of the optical system, are broadly classified into light-collecting properties for forming a diffraction-limited minute spot, focus control and tracking control of the optical system, and detection of a pit signal. . These are manifested by a combination of various optical systems and photoelectric conversion detection systems according to the purpose and application. Particularly, in recent years, in order to reduce the size and thickness of the optical pickup head device, light using a hologram has been used. A pickup head device is disclosed.

FIG. 14 shows, as a conventional example, a configuration diagram of an optical head device which we devised and filed a patent application (Japanese Patent Application No. 3-46630).

In FIG. 14, reference numeral 2 denotes a radiation light source such as a semiconductor laser. A light beam 3 (laser light) emitted from this light source is reflected by a reflection-type blazed hologram 105 (hereinafter simply referred to as a hologram) and is incident on an objective lens 4.
The light is focused on the information medium 5. The light beam reflected by the information medium 5 follows the original optical path (return path) and enters the hologram 105. The + 1st-order diffracted light 6 on the return path generated from the hologram 105 enters the photodetector 7. By calculating the output of the photodetector 7, a servo signal and an information signal can be obtained.

Here, the reason that the hologram 105 is blazed is that unnecessary diffracted light generated from the hologram 105 on the outward path from the radiation source 2 to the information medium 5 is reflected by the information medium 5 and is detected by the photodetector 7. This is to prevent the light from being incident on the.

[0006] In manufacturing a blazed hologram, a multi-level hologram having a stepped cross-sectional shape (FIG. 16) is formed by two etchings as shown in FIG. 15, thereby increasing the degree of freedom in controlling the diffraction efficiency. Can be higher. In other words, unnecessary diffracted by controlling the phase modulation amount phi ₁ of the light beam determined by the first-time etching depth h _1, of the light beam determined by the second time etch depth h ₂ and a phase modulation amount phi ₂ independently It is possible to reduce the diffraction efficiency of light, and at the same time, to increase the utilization efficiency of light transmitted and received.

Further, a reflection-type blazed hologram 10
Since 5 also functions as a mirror for folding the optical axis, there is an effect that a thin optical head device can be constituted by a small number of components.

[0008]

Here, paying attention to the influence of unnecessary diffracted light on the outward path with respect to the information signal, for example, the -1st-order diffracted light generated from the hologram 105 on the outward path is reflected by the information medium 5 and becomes a hologram. And the 0th-order diffracted light (on the return path) enters the photodetector. Similarly,
As shown in FIG. 17, the N-order diffracted light 62 on the outward path is reflected by the information medium 5 and the (N + 1) -order diffracted light 63 on the return path, which is generated when the hologram 103 is incident, also enters the photodetector. Among the light incident on these photodetectors, the light having the highest light intensity is light necessary for obtaining an information signal or a servo signal, and the 0th-order diffracted light 61 (FIG. 14) on the outward path is incident on the hologram 103. + 1st-order diffracted light (referred to as L1) on the return path. The next strongest light is the light including the 0th-order or + 1st-order diffraction on either the forward path or the return path. That is, the 0th-order diffracted light on the return path generated when the -1st-order diffracted light on the forward path enters the hologram (this is referred to as L2), and the + 2nd-order diffracted light on the return path generated by entering the + 1st-order diffracted light on the hologram (this is referred to as L2). Is L3). Therefore, if the light quantity of these two lights is designed to be sufficiently smaller than the light quantity of L1, the influence of unnecessary diffracted light on the information signal, that is, noise can be suppressed.

Considering not only the surface of the light amount but also the size of the spot on the information medium 5, the higher the order of the diffracted light, the larger the amount of aberration. There is no change in the amount of light, and no noise is generated even when the light enters the photodetector 7. Therefore, the amount of light on which the -1st-order diffracted light on the outward path and the + 1st-order diffracted light on the outward path enter the photodetector, that is,
What is necessary is just to make small the light quantity of L2 and L3. The ratio E ₂ of the light amount of these unnecessary lights (L2 and L3) to the light amount of L1.
FIG. 18 is a graph showing the relationship between the light beam phase modulation amount φ ₂ determined by the second etching depth (FIG. 15). As can be seen from this graph, when the amount of phase modulation φ ₂ is 0.2π to 0.45π, E ₂ becomes 0.3 or less. However E ₂ is the problem that at all to become the outward does not mean + 1st-order diffracted light and the forward path of the -1-order diffracted light 0 also information on an information medium is irradiated, somewhat incident on the photodetector as noise is there.

Accordingly, an object of the present invention is to solve the above problems and to provide a small, lightweight, and inexpensive optical system by applying a hologram.

[0011]

According to the present invention, in order to solve the above-mentioned problems, a radiation light source, a light-collecting optical system for receiving a light beam from the radiation light source and condensing the light beam into a minute spot on an information medium, A photodetector comprising a plurality of photodetectors for receiving a light beam reflected and diffracted by the information medium and outputting a photocurrent; and diffracting the light beam reflected by the information medium as diffracted light to the light detector. And a hologram for guiding the diffracted light generated from the hologram.
Light is received by the photodetector, photoelectrically converted, and focus error
-Optical head device that obtains the tracking signal and tracking error signal
The photodetector is divided into a plurality of photodetectors.
Multiple light detectors to detect tracking error signals
And a first tracking error signal detecting light detecting section.
And a second tracking error signal detection light detection unit.
The hologram is a light beam reflected by the information medium.
Circuit for tracking error signal detection when
Diffracts the folded light and detects the first tracking error signal.
First tracking for generating diffracted light incident on the detection unit
Diffraction light generation region for error signal detection and second tracking
Generates diffracted light incident on the error signal detection light detector
A second tracking error signal detection diffracted light generation region;
And a first tracking error signal detecting diffracted light.
The generation area is divided into multiple
The tolls are different from each other and each divided area
Diffracted light diffracted from
Into the tracking error signal detection photodetector,
The diffraction light generation area for tracking error signal detection 2
And the lattice vectors of each divided area are mutually
Differ from each split region, different from each other
The diffracted light is diffracted in different directions and the second tracking
Incident on the light detection unit for detecting the
Is reflected when the light beam reflected by the information medium is incident.
Oka Suera signal detecting diffracted light is also diffracted, the holography
A probe that generates diffracted light for detecting the focus error signal of the ram
The program area is divided into a plurality of sections,
The child vectors are different from each other and
The diffracted light diffracted from the split region diffracts in different directions,
Incident on the photodetector that detects the focus error signal,
The hologram pattern of the hologram covers the entire surface.
Optical head device characterized by having a lens function
Configuration.

Also, a drive mechanism for the information medium, the optical head device of the present invention, a focus servo mechanism and a tracking servo mechanism, an electric circuit for realizing the servo mechanism, and a connection part to a power supply or an external power supply An optical information device having at least: Configuration.

Furthermore, among the light beam condensed by the condensing means in the vicinity of the information medium, a light beam L used to obtain the information signal or servo signal light reflected on the information medium of the information medium focus condensed on the information recording surface is irradiated at a position apart each divided into a plurality before <br/> SL information medium on the information recording surface of an unnecessary light beam other than the beam L Optical information reproduction method
Receiving the light beam reflected and diffracted by the information medium
A photodetector comprising a plurality of photodetectors for outputting
The light beam reflected by the information medium is diffracted as diffracted light before
Use a hologram to guide the light beam to the light detector
The diffracted light generated from the hologram
The focus error signal is received by the
Signal and tracking error signal, the photodetector
Tracking error signal
There are a plurality of photodetectors for detecting
And a second tracking error signal.
And a light detection unit for detecting a color signal.
When a light beam reflected by the information medium enters,
Diffracts the diffracted light for detecting the locking error signal, and
The diffracted light that enters the light detector for detecting the
Generated diffracted light for detecting the first tracking error signal generated
Light detection unit for detecting the raw area and the second tracking error signal
Tracking error that generates diffracted light incident on the surface
A first track having a diffracted light generation region for signal detection;
The diffraction light generation area for detecting the
And the grid vectors of each divided area are different from each other.
Diffracted light diffracted from each divided area
And a first tracking error signal
The light is incident on the detection light detection unit, and the second tracking error signal
The diffraction light generation area for signal detection is divided into multiple
The grid vectors of the region are different from each other
Diffracted light diffracted from each divided area diffracts in different directions
And light detection for detecting a second tracking error signal
And the hologram is reflected by the information medium
For detecting focus error signal when light beam is incident
Diffracted light is also diffracted, and the focus error signal of the hologram is
The hologram area that generates the diffracted light for signal detection is divided into multiple
And the lattice vectors of each divided area are
Diffracted light diffracted from different divided areas
Diffracts in different directions to detect focus error signal
The hologram of the hologram.
The ram pattern has a lens effect over the entire surface.
The unnecessary light due to the information part other than the desired information part.
Reduces the amount of beam modulation, which reduces noise components
An optical information reproducing method characterized by reduction is used.

[0014]

By providing a lens function in at least a part of the hologram, unnecessary diffracted light such as ± 1st-order diffracted light on the outward path is defocused and greatly spread on the information medium. And does not include noise for the information signal.

Therefore, an optical head device capable of obtaining an information signal having a very good S / N ratio can be constructed.

Alternatively, the hologram is divided into regions, and the diffraction directions of the diffracted light from the respective regions are made different. By doing so, unnecessary diffracted light on the outward path is also divided into many parts, and when the sum of these is taken, the change in the amount of light (noise component) obtained on the information medium is averaged and the amplitude becomes small, so that S / N An optical head device capable of obtaining an information signal having a very good ratio can be configured.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, unnecessary diffracted light on the outward path is transmitted to the information medium 5.
When irradiated on the top, unnecessary diffracted light on the outward path has a sufficiently large spread on the information medium or is separated into a plurality of pieces and has a small numerical aperture, so that it has almost no information component. .

An embodiment of the present invention will be described below with reference to the drawings. In the embodiment of the present invention, for example, a spot size detection method (SSD method) is used as a focus servo signal detection method. The SSD method is disclosed in Japanese Patent Laid-Open No. 2-185.
As disclosed in Japanese Unexamined Patent Publication No. 722, this is a detection method capable of remarkably reducing the assembly tolerance of the optical head device and stably obtaining a servo signal with respect to wavelength fluctuation.

In order to realize the SSD method, the hologram is designed so that the + 1st-order diffracted light on the return path of the hologram becomes two types of spherical waves having different curvatures. Each spherical wave is designed to have a focal point on the front side e or the rear side f of the plane of the photodetector 7 in FIG. 1, and as shown in FIG.
And 142 are received by the six-segment photodetector 71. Here, (b) shows the just focus state, and (a),
(C) shows a defocused state. Therefore, the focus error signal FE is: FE = (S10 + S30-S20)-(S40 + S60-S50). . . (1) is obtained.

FIG. 3 shows an example of realizing a blazed hologram for the SSD method. In FIG. 3, for example, A region 15
1 is a spherical wave 141 having a focal point in front of the photodetector (FIG. 1)
And the B region 152 generates a spherical wave 142 (FIG. 1) having a focal point behind the photodetector. Although the far field pattern of the wavefront diffracted from the hologram pattern as shown in FIG. 3 partially lacks as shown in FIG.
There is no effect on the focus servo signal.

When the diffracted light generating regions 151 and 152 for detecting the focus servo signal of the hologram 102 have a lens function as described above, unnecessary diffracted light on the outward path can be removed from the information medium 5.
Since the light beam is defocused and spreads wide, the large area of the information medium 5 is illuminated, so that the information is averaged and there is an effect that the information signal hardly contains noise.

Since the depth of focus is within about ± 1 μm, it is desirable that unnecessary diffracted light due to the lens action of the hologram is set to a sufficiently large value as compared with the depth of focus to defocus unnecessary diffracted light by 5 μm or more. . By defocusing unnecessary diffracted light by 5 μm or more,
The effect that the modulation amount of the light beam irradiated to the information part other than the desired information part, that is, the unnecessary diffracted light, can be set to 1/10 or less of the modulation amount of the light beam irradiated to the desired information part. Obtainable. At this time, for example, if the hologram is blazed and the ratio E ₂ of unnecessary diffraction light (FIG. 18) is suppressed to 30% or less, the noise amplitude due to the unnecessary diffraction light becomes 3% or less of the information signal amplitude, and the jitter of the information signal is reduced. The effect that the amount of increase can be neglected can be obtained. In another embodiment described below, when unnecessary light diffracted on the outward path is defocused and widely spread on the information medium 5 to average the information and reduce noise for the information signal, the unnecessary diffracted light is similarly 5 μm. It is desirable to make the above defocus.

The light reflected on the information medium 5 has a diffraction pattern caused by being diffracted by the track grooves on the information medium 5. Therefore, a change in the light amount distribution on the hologram occurs due to a change in the relative position between the converging spot on the information medium 5 and the track groove. For example, assuming that the X direction in FIG. 3 is a direction parallel to the track grooves of the information medium, the + Y direction becomes brighter, the −Y direction becomes darker, or the opposite light amount change occurs.

Therefore, it is desirable to divide the area shown in FIG. 3 into several to several tens as shown here. This is because the hologram area is divided into many parts in this manner, so that the asymmetry in the + Y direction and the −Y direction is reduced, and the light amount on the hologram due to a change in the relative position between the converging spot on the information medium 5 and the track groove. This is because it is possible to prevent an offset from occurring in the focus servo signal due to the influence of the distribution change. Therefore, if the hologram area is divided into multiple parts, stable focus servo characteristics can be obtained. Also, by increasing the number of divisions, unnecessary diffracted light on the outward path is also divided into a large number on the information medium 5, and each divided area has a smaller NA (numerical aperture) and the diffracted light spreads greatly. Therefore, the signal component obtained when the information medium 5 is irradiated is more averaged, and the noise component can be reduced.

Here, in order to divide unnecessary diffracted light on the forward path into a large number on the information medium, the grating vector k of the divided region of the hologram may be different for each divided region. Then, the half value diameter (full width half maximu
Considering that m) is 1 μm or less, it is desirable that the distance for splitting unnecessary diffracted light on the information medium be set to a sufficiently large value of 5 μm or more. Therefore, when the focal length of the objective lens, which is a component of the condensing optical system, is f, the wavelength of the light beam emitted from the radiation light source is λ, and the pi is π, each divided area of the hologram pattern is Are different from each other, and the magnitude | dk | of the different vector quantity dk is 5 μm × 2π /
Desirably, it is larger than (fλ).

In another embodiment described below, the unnecessary diffracted light on the outward path is divided into a large number on the information medium 5 by being divided into a large number on the information medium 5 and the NA (numerical aperture) of each divided area is further increased. ) Is reduced, the diffracted light is greatly expanded, and the signal component obtained when the information medium 5 is irradiated is averaged to reduce the noise component. Similarly, the lattice vector k of each divided region of the hologram pattern is similarly reduced. Are different from each other, and the different vector quantities dk
Is preferably larger than 5 μm × 2π / (fλ).

Next, a tracking signal detecting diffracted light generating area will be considered. In order to extract a change in the light amount distribution on the hologram due to a change in the relative position between the converging spot on the information medium 5 and the track groove as the tracking error signal TE, another diffraction area 153 or 154 is required as shown in FIG. Provided on the hologram 104. This diffraction area 1
The tracking error signal detection diffracted light 163 from the reference numeral 53 or 154 is converted to the tracking error signal detection light detector 72.
The tracking error signal TE can be obtained by the calculation shown in Equation 2 after receiving the light by (FIG. 5).

TE = S70-S80. . . (2) Here, an embodiment aiming at preventing unnecessary diffracted light on the outward path generated from the tracking error signal detection diffracted light generation area from having a noise component will be described below.

FIG. 5 shows a first embodiment. In FIG. 5, reference numerals 153 and 154 denote tracking error signal detection diffracted light generating regions. In the present embodiment, the hologram patterns of these two regions also have different coordinates (points e and f) in the direction parallel to the optical axis from the focal point O of the reference wavefront 64 as shown in FIG.
A wavefront having a converging point at (point) is created as object light by two-beam interference or computer hologram (CGH). Then, since the hologram pattern has a lens function, FIG.
The diffracted light is defocused on the photodetector 72 like the diffracted light 163 for tracking error signal detection shown in FIG. Naturally, unnecessary diffracted light on the outward path is also defocused on the information medium 5, so that there is an effect that the information on the information medium 5 is largely spread and noise on the information signal is not included.
That is, in this embodiment, since both the diffracted light generation area for focus servo signal detection and the diffracted light generation area for tracking error signal detection have a lens function, all unnecessary diffracted light on the outward path is greatly defocused on the information medium 5 and thus spreads widely. In order to irradiate a large area, the information of the information medium 5 is averaged, and there is an effect that the information signal does not include noise.

FIG. 6 shows a second embodiment. In the present embodiment, the tracking error signal detection diffracted light generation region is further divided into four regions, and the diffraction directions of the diffracted light from the respective regions are set to different directions. By splitting in this way, unnecessary diffracted light on the outward path is also split into many parts and one by one.
Since the NA (numerical aperture) of the two divided areas is reduced and the diffracted light is greatly spread, the information signal (noise) obtained on the information medium 5 when the sum of them is obtained is averaged to reduce the amplitude. This has the effect.

Furthermore, the first embodiment and the second embodiment can be used in combination. That is, as in the second embodiment, the diffracted light generation region for tracking error signal detection is further divided into multiple regions, the diffraction directions of the diffracted light from each region are made different, and the hologram pattern of each region is A lens function is provided as in the first embodiment. In this way, noise due to unnecessary diffracted light on the outward path can be further reduced.

A hologram for noise cancellation and
FIG. 7 shows Reference Example 1 of the photodetector . In FIG. 7, 18
Reference numeral 2 denotes a noise canceling diffracted light generation area, and reference numeral 75 denotes a noise canceling signal detection photodetector. In this reference example, JP-A-60-138748 and JP-A-61-13124 are used.
5, the noise on the signal can be reduced.

In this embodiment, the noise canceling diffracted light 164 generated from the noise canceling diffracted light generating area 182 is received by the noise canceling signal detecting light detector 75, and the noise canceling signal detecting light detector 75 is detected. Is obtained. Then, the information signal RF is detected by the following calculation to reduce noise.

RF = (S10 + S20 + S30 + S40 + S50 + S60 + S70 + S80) + R × S90 (3) where R is a coefficient for weighting the noise canceling signal S90. . In this reference example, JP-A-60-1
38748 and JP-A-61-131245,
Since the light amount of the light beam is divided on the hologram, there is an effect that the permissible setting accuracy of the photodetector can be increased about 100 times. Further, by using a hologram pattern having a lens function as the noise canceling signal detecting photodetector 75, unnecessary diffracted light on the outward path can be reduced.
Due to the above-mentioned defocusing, there is an effect that the information on the information medium 5 is largely spread and the noise on the information signal is not included.

FIG. 8 shows a second embodiment in which noise cancellation is performed in the same manner as the first embodiment. 8, the noise canceling diffracted light generation region 183 is divided into a plurality (four in the figure). Then, the noise canceling diffracted light 164 diffracted from each of the divided areas is received by the noise canceling signal detecting photodetector 75, and the output signal S90 of the noise canceling signal detecting photodetector 75 is obtained. Then, the information signal RF is detected by the calculation of the expression (3) to reduce the noise. In the present reference example, by dividing the noise canceling diffracted light generation region 183 into a plurality as shown in FIG. 8, unnecessary diffracted light on the outward path is also multi-divided, and each divided region has an NA (numerical aperture). Is reduced and the diffracted light is greatly spread, so that the information signal (noise) obtained on the information medium 5 when the sum of them is obtained is averaged and the amplitude is reduced.

Further, Reference Examples 1 and 2 can be used in combination. That is, as in Reference Example 2, the noise canceling diffracted light generation region is further divided into multiple regions.
In addition to making the diffraction directions of the diffracted light from each area different, the hologram pattern of each area is
A lens function is provided as in Reference Example 1 . In this way, noise due to unnecessary diffracted light on the outward path can be further reduced.

Further, in addition to the above-mentioned reference example , the cross-sectional shape of the hologram is blazed as shown in FIG. There is an effect that an optical head device capable of sufficiently suppressing noise due to unnecessary diffracted light and obtaining an information signal having a very good S / N ratio can be configured.

In a third embodiment, the hologram described above is integrated with an objective lens. By doing so, even if the objective lens moves due to tracking following, external vibration, or the like, the effect that the light beam does not move on the hologram and the servo signal and the information signal do not deteriorate can be obtained.

FIG. 9 shows a fourth embodiment. In FIG. 9, reference numeral 80 denotes a package unit such as the radiation light source 2 and 82 denotes an electrical connection terminal. In this embodiment, the photodetector 7 is also arranged in the package means 80 of the radiation light source 2. With this configuration, the relative distance between the radiation light source 2 and the photodetector 7 can be reduced, so that the optical head device can be reduced in size and weight. Further, the package means of the radiation light source 2 and the photodetector 7 is combined with one package means 80.
Since the number of packages required is small, the cost and size and weight of the optical head device can be reduced.

A fifth embodiment will be described with reference to FIG. In FIG. 9, reference numeral 104 denotes a hologram. In this embodiment, the hologram 104 is attached to the package means 80 and used as an exit window for the light beam 3 emitted from the radiation light source 2 and also as a sealing means for the radiation light source 2 and the like.
Also in the present embodiment, the number of parts can be reduced, so that there is an effect that a low-cost optical head device can be obtained. Also,
Since there is no need to provide a mechanism for holding the hologram 104, the optical head can be reduced in size and weight.

As Reference Example 3, as shown in FIG.
All optical components such as the radiation light source 2, the photodetector 7, the reflection-type blazed hologram 105, and the objective lens 4 are integrated by the all-optical-system holding means 14 such as an aluminum housing.
However, a configuration in which the all-optical-system holding means 14 is driven integrally is considered.
available. According to this configuration, even if the objective lens 4 moves by following the track, the relative position with respect to the radiation light source 2 does not change, and there is an effect that off-axis aberration does not occur. Furthermore, since off-axis aberration does not occur, the objective lens 4 can be reduced in size and thickness, so that there is an effect that an even smaller and thinner optical head device can be configured.

Further, even when an optical head device is formed by using a transmission type hologram as shown in FIG.
It is obvious that the present invention is effective and the same effect can be obtained even when the optical head device is configured using the reflection type hologram as shown in FIG. Although the hologram patterns of the transmission holograms arranged perpendicular to the optical axis have been illustrated in the above embodiments, the hologram patterns are arranged obliquely with respect to the optical axis in the finite optical system, and FIGS.
In the case where a reflection hologram is used as shown in FIG. 1, the hologram pattern may be as shown in the schematic diagrams shown in FIGS. FIG. 11 corresponds to the first embodiment, and FIG.
Reference numeral 2 denotes an example of a hologram pattern corresponding to Reference Example 1 .

Further, as a sixth embodiment, an embodiment of an optical information device constituted by using the optical head device of the present invention is shown in FIG.
Shown in In FIG. 13, the information medium 5 is rotated by the information medium driving mechanism 405. The optical head device 401 is roughly moved by the optical head device driving device 402 up to a track on the information medium 5 where desired information exists.
The optical head device 401 also sends a focus error signal and a tracking error signal to the electric circuit 403 according to the positional relationship with the information medium 5. The electric circuit 403
Sends a signal for finely moving the objective lens to the optical head device 401 in response to this signal. With this signal, the optical head performs focus servo and tracking servo on the optical disk, and reads, writes, or erases information on the information medium 5. The optical information device according to the present embodiment includes an optical head device 401.
Since an optical head device capable of obtaining an information signal having a very good S / N ratio is used in the present invention, there is an effect that information can be reproduced accurately and stably. Further, since the optical head device of the present invention is small and lightweight, the optical information device of the present embodiment using the optical head device is also small and lightweight, and has an effect that the access time is short.

[0044]

As is apparent from the above description,
According to the present invention, the following effects can be obtained.

(1) By providing a lens function to the hologram focus servo signal detection diffracted light generation region of the hologram, unnecessary diffracted light such as the ± 1st-order diffracted light on the outward path is defocused on the information medium and greatly spreads. The change (noise component) is averaged and does not include noise for the information signal.

Further, in the first embodiment, since the hologram pattern in the tracking error signal detecting diffracted light generating region has a lens function, unnecessary diffracted light on the outward path is defocused on the information medium, and thus the spread light amount is greatly increased. The change (noise component) is averaged, and there is an effect that the information signal does not include noise. That is, in this embodiment, since both the focus servo signal detection diffracted light generation area and the tracking error signal detection diffraction light generation area have a lens function, all unnecessary diffracted light on the outward path is also defocused on the information medium, so that it spreads greatly. Since the information of the information medium is averaged and does not include noise for the information signal, there is an effect that an optical head device capable of obtaining an information signal having a very good S / N ratio can be configured.

[0047]

(2) The hologram pattern is divided into many parts,
The directions of diffraction of the diffracted light from the respective regions are made different. By doing so, unnecessary diffracted light on the outward path is also divided into many parts, and when the sum of these is taken, the change in the amount of light (noise component) obtained on the information medium is averaged and the amplitude becomes small, so that S / N There is an effect that an optical head device capable of obtaining an information signal having a very good ratio can be configured.

As described above, according to the present invention, when the unnecessary diffraction light on the outward path is irradiated on the information medium, the unnecessary diffraction light on the outward path has a sufficiently large spread on the information medium or is separated into a plurality of pieces. The characteristic is that it has almost no noise component.

(3) Further, the optical information device of the present invention uses the optical head device of the present invention, which can obtain an information signal having a very good S / N ratio, as the optical head device. In addition, there is an effect that it can be executed stably. Further, since the optical head device of the present invention is small and lightweight, the optical information device of the present embodiment using the optical head device is also small and lightweight, and has an effect that the access time is short.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a main part of an optical head device according to an embodiment of the present invention.

FIG. 2 is a plan view illustrating a state of diffracted light on a photodetector according to the embodiment of the present invention.

FIG. 3 is a schematic plan view showing a hologram pattern according to the embodiment of the present invention.

FIG. 4 is a schematic plan view showing a hologram pattern according to the embodiment of the present invention.

FIG. 5 is a schematic perspective view of a main part of the optical head device according to the first embodiment of the present invention.

FIG. 6 is a schematic perspective view of a main part of an optical head device according to a second embodiment of the present invention.

FIG. 7 is a schematic perspective view of a main part of an optical head device according to a first embodiment of the present invention;

FIG. 8 is a schematic perspective view of a main part of an optical head device according to a second embodiment of the present invention.

FIG. 9 is a schematic perspective view of an optical head device according to a fourth embodiment and a fifth embodiment of the present invention.

FIG. 10 is a schematic perspective view of an optical head device according to a third embodiment of the present invention.

FIG. 11 is a schematic plan view illustrating a hologram pattern according to an embodiment of the present invention.

FIG. 12 is a schematic plan view illustrating a hologram pattern according to the first embodiment of the present invention.

FIG. 13 is a schematic sectional view of an optical information device according to an embodiment of the present invention;

FIG. 14 is a schematic sectional view of an optical head device according to a conventional example and an embodiment of the present invention.

FIG. 15 is a schematic explanatory view of a conventional example and a preparation example of a blazed hologram which is a requirement of the embodiment of the present invention.

FIG. 16 is a cross-sectional view of a part of a blazed hologram in a conventional example.

FIG. 17 is a schematic cross-sectional view for explaining a state where unnecessary diffracted light on the outward path is incident on the photodetector.

FIG. 18 is an explanatory diagram showing a relationship between a phase modulation amount of light by a blazed hologram and a ratio of unnecessary diffracted light, which is a requirement of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 blazed hologram 2 radiation light source 3 light beam 4 objective lens 5 information medium 6 + 1st-order diffracted light on return path 7 photodetector 61 0th-order diffracted light on forward path 103 hologram 105 reflective blazed hologram 106 reflective blazed hologram 141 spherical surface Wave (+ 1st-order diffracted light) 142 Spherical wave (+ 1st-order diffracted light)

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Makoto Kato 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-94541 (JP, A) JP-A-4- 40634 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B 7/135

Claims (8)

(57) [Claims] 1. A radiation light source, a condensing optical system for receiving a light beam from the radiation light source and condensing the light beam onto a small spot on an information medium, and a plurality of light receiving means for receiving a light beam reflected by the information medium and outputting a signal. A photodetector comprising a photodetector; and a hologram for diffracting the light beam reflected by the information medium as diffracted light to guide the light beam to the photodetector, wherein the diffracted light generated from the hologram is provided. An optical head device that receives a light by the photodetector and performs photoelectric conversion to obtain a focus error signal and a tracking error signal, wherein the photodetector is divided into a plurality of photodetectors and detects the tracking error signal. There are multiple light detectors.
, Comprises a first tracking error signal detection optical detecting unit, and a second tracking error signal detecting photodetecting section
The hologram receives the light beam reflected by the information medium.
When launched, the diffraction light for tracking error signal detection is rotated.
Folds and enters the first tracking error signal detection light detection unit.
Tracking error signal detection that generates diffracted light
Incident on the diffraction light generation region and the second tracking error signal detection light detection unit.
Of a second tracking error signal that generates diffracted light
And a first tracking error signal detecting diffracted light generating region.
The vector is divided into multiple parts, and the lattice vectors of each
Diffracted from each divided area
Diffracted light is diffracted in different directions and
The second tracking error signal detection diffracted light generation region is incident on the tracking error signal detection light detection unit.
The vector is divided into multiple parts, and the lattice vectors of each
Diffracted from each divided region
Diffracted light is diffracted in different directions and the second track
The hologram receives the light beam reflected by the information medium.
Diffracts diffraction light for focus error signal detection when projected
And a focus error signal detection diffraction of the hologram
The hologram area that generates light is divided into multiple
The grid vectors of each divided area are different from each other.
Diffracted light diffracted from each divided area
Photodetector that detects the focus error signal by diffracting
And a hologram pattern of the hologram has a lens function over the entire surface. 2. The optical head device according to claim 1, wherein the focal length of the objective lens, which is a component of the condensing optical system, is f, the wavelength of the light beam emitted from the radiation light source is λ, and the circular constant. Where π is π, the lattice vectors k of the respective divided regions of the hologram pattern are different from each other, and the magnitude | dk | of the different vector amount dk is 5 μm.
An optical head device characterized by being larger than × 2π / (fλ). 3. The optical head device according to claim 1, wherein, due to a lens function of the hologram, diffracted lights of different orders generated from the hologram have a focal position on the information medium separated by at least 5 μm in the optical axis direction. An optical head device comprising: 4. The optical head device according to claim 1, wherein the radiation light source is built in a package, and a light detector is also built in the package. Optical head device. 5. The optical head device according to claim 1, wherein the objective lens and the hologram are integrated. 6. The optical head device according to claim 4, wherein the radiation light source is built in the package, and the package and the hologram are integrated. 7. A light beam L which is used for obtaining an information signal or a servo signal by using the light reflected on the information medium among the light beams condensed by the light condensing means near the information medium. An optical information reproducing method for focusing on an information recording surface and condensing the same, and irradiating an unnecessary light beam other than the light beam L on the information recording surface of the information medium into a plurality of portions and irradiating the plurality of portions to distant positions. A photodetector comprising a plurality of photodetectors for receiving a light beam reflected and diffracted by the information medium and outputting a signal, and diffracting a light beam reflected by the information medium as diffracted light to detect the light Using a hologram for guiding a light beam to a detector, receiving the diffracted light generated from the hologram by the photodetector, photoelectrically converting the diffracted light into a focus error signal and a tracking error signal. Obtained, the photodetector includes a plurality of
There are multiple photodetectors that are divided into photodetectors and detect tracking error signals.
, Comprises a first tracking error signal detection optical detecting unit, and a second tracking error signal detecting photodetecting section
The hologram receives the light beam reflected by the information medium.
When launched, the diffraction light for tracking error signal detection is rotated.
Folds and enters the first tracking error signal detection light detection unit.
Tracking error signal detection that generates diffracted light
Incident on the diffraction light generation region and the second tracking error signal detection light detection unit.
Of a second tracking error signal that generates diffracted light
And a first tracking error signal detecting diffracted light generating region.
The vector is divided into multiple parts, and the lattice vectors of each
Diffracted from each divided area
Diffracted light is diffracted in different directions and
The second tracking error signal detection diffracted light generation region is incident on the tracking error signal detection light detection unit.
The vector is divided into multiple parts, and the lattice vectors of each
Diffracted from each divided area
Diffracted light is diffracted in different directions and the second track
The hologram receives the light beam reflected by the information medium.
Diffracts diffraction light for focus error signal detection when projected
And a diffraction for detecting a focus error signal of the hologram.
The hologram area that generates light is divided into multiple
The grid vectors of each divided area are different from each other.
Diffracted light diffracted from each divided area
Photodetector that detects the focus error signal by diffracting
And the hologram pattern of the hologram has a lens function over the entire surface, thereby reducing the amount of modulation of the unnecessary light beam by information parts other than the desired information part, thereby reducing noise components. An optical information reproducing method characterized by reducing the amount of light. 8. A driving mechanism for an information medium, a radiation light source, a condensing optical system for receiving a light beam from the radiation light source and condensing the light beam onto a small spot on the information medium, and a light beam reflected by the information medium. A photodetector comprising a plurality of photodetectors for outputting a reception signal, and a hologram for diffracting the light beam reflected by the information medium as diffracted light to guide the light beam to the photodetector, The diffracted light generated from the hologram is received by the photodetector, and is subjected to photoelectric conversion to detect a focus error signal and a tracking error signal. The photodetector is divided into a plurality of photodetectors and outputs a tracking error signal. There are multiple light detectors to detect.
, Comprises a first tracking error signal detection optical detecting unit, and a second tracking error signal detecting photodetecting section
The hologram receives the light beam reflected by the information medium.
When launched, the diffraction light for tracking error signal detection is rotated.
Folds and enters the first tracking error signal detection light detection unit.
Tracking error signal detection that generates diffracted light
Light generation area and second tracking error signal detection
Track for generating diffracted light incident on a light detection unit for use
And a first tracking error signal detection diffracted light generation region.
The vector is divided into multiple parts, and the lattice vectors of each
Diffracted from each divided area
Diffracted light diffracts in different directions and
The second tracking error signal detection diffracted light generation region is incident on the tracking error signal detection light detection unit.
The vector is divided into multiple parts, and the lattice vectors of each
Diffracted from each divided region
Diffracted light is diffracted in different directions and the second track
The hologram receives the light beam reflected by the information medium.
Diffracts diffraction light for focus error signal detection when projected
And a diffraction for detecting a focus error signal of the hologram.
The hologram area that generates light is divided into multiple
The grid vectors of each divided area are different from each other.
Diffracted light diffracted from each divided area
Photodetector that detects the focus error signal by diffracting
And a hologram pattern of the hologram has a lens action over the entire surface, a focus servo mechanism and a tracking servo mechanism, an electric circuit for realizing the servo mechanism, a power supply or an external power supply An optical information device having at least a connection portion with the optical information device.