JP2004071134A - Compound objective lens, optical head device, optical information device, computer, optical disk player, car navigation system, optical disk recorder, optical disk server - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable stable and highly accurate interchangeable recording and reproducing between a BD of base material approximately 0.1mm thick corresponding to a blue light beam and a DVD of base material 0.6mm thick corresponding to a red light beam by using a compound objective lens consisting of hologram and an objective lens. <P>SOLUTION: Lattices having a cross-sectional shape in which steps of height of 0 times, two times, one times, three times of a unit step giving difference of the optical path of approximately one wavelength for a blue light beam facing an optical axis from the outer peripheral side is one period p1 are formed only at an inner peripheral part of a hologram 131. This hologram does not diffracts a blue light beam, but transmits as 0 order diffraction light as it is, also, radiates a read light beam passing through the inner peripheral part as +1 order diffraction light. Thereby, a focal length of a red light beam is made longer than that of a blue light beam, and operation distance is made longer. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a compound objective lens in which an objective lens and a hologram that is a diffractive element are combined, and records, reproduces, or erases information by condensing light beams of a plurality of wavelengths on an optical disk via the compound objective lens. The present invention relates to an optical head device, an optical information device having the optical head device mounted thereon, and a computer, an optical disk player, a car navigation system, an optical disk recorder, and an optical disk server to which the optical information device is applied.
[0002]
[Prior art]
Optical memory technology using an optical disk having a pit-shaped pattern as a high-density, large-capacity storage medium has been put to practical use while expanding its applications with digital audio disks, video disks, document file disks, and even data files. . The function of successfully performing information recording / reproduction on an optical disk with high reliability through a minutely focused light beam is a condensing function that forms a diffraction-limited minute spot, and a focus control of an optical system ( Focus servo), tracking control, and pit signal (information signal) detection.
[0003]
In recent years, with the development of optical system design technology and the shortening of the wavelength of a semiconductor laser as a light source, the development of a high-density optical disk having a storage capacity larger than that of a conventional one has been progressing. As an approach for increasing the density, it has been considered to increase the numerical aperture (NA) on the optical disc side of a condensing optical system that narrows a light beam onto an optical disc. At this time, a problem is an increase in the amount of aberration generated due to the tilt (so-called tilt) of the optical axis. When the NA is increased, the amount of aberration generated with respect to the tilt increases. To prevent this, the thickness (base material thickness) of the substrate of the optical disk may be reduced.
[0004]
A compact disk (CD), which can be said to be the first generation of optical disks, uses infrared light (wavelength λ3 of 780 nm to 820 nm) and an objective lens with NA of 0.45, and the substrate thickness of the disk is 1.2 mm. The second generation DVD uses red light (wavelength λ2 is 630 nm to 680 nm, standard wavelength 660 nm) and an objective lens with NA of 0.6, and the base material thickness of the disc is 0.6 mm. Further, a third-generation optical disk (hereinafter also referred to as a BD (Blue-ray Disk)) uses blue light (wavelength λ1 is 390 nm to 415 nm, standard wavelength 405 nm) and an objective lens with an NA of 0.85, and The substrate thickness is 0.1 mm. In this specification, the substrate thickness refers to a thickness from a surface on which an optical beam is incident on an optical disk (or information medium) to an information recording surface.
[0005]
As described above, the thickness of the base material of the optical disk decreases as the density increases. From the viewpoints of economy and space occupied by the device, an optical information device capable of recording and reproducing optical disks having different substrate thicknesses and different recording densities is desired. For that purpose, an optical head device having a condensing optical system capable of condensing a light beam to a diffraction limit on optical disks having different substrate thicknesses is required.
[0006]
Further, when recording / reproducing an optical disk having a thick base material, it is necessary to condense a light beam on a recording surface deeper from the surface of the disk, so that a longer focal length is required.
[0007]
Japanese Patent Application Laid-Open No. 7-98431 discloses a configuration for realizing an optical head device for performing recording and reproduction on optical disks having different substrate thicknesses. This will be described as a first conventional example with reference to FIGS. 25A and 25B.
[0008]
25A and 25B, reference numeral 40 denotes an objective lens, and reference numeral 41 denotes a hologram. The hologram 41 has a concentric lattice pattern formed on a substrate transparent to the incident light beam 44.
[0009]
As shown in FIG. 25A, the objective lens 40 transmits the 0th-order diffracted light 42 transmitted through the hologram 41 without being diffracted, for example, with a substrate thickness (t2) of 0.6 mm. It is designed to be able to form a diffraction-limited condensed spot on the optical disk 10 having the optical disk. FIG. 25B shows that a condensing spot of a diffraction limit can be formed on the optical disc 11 having a larger base material thickness (t1) of 1.2 mm. In FIG. 25B, the + 1st-order diffracted light 43 diffracted by the hologram 41 is condensed on the optical disc 11 by the objective lens 40. Here, aberration correction is performed so that the + 1st-order diffracted light 43 can be narrowed down to the diffraction limit through a substrate having a thickness of t1.
[0010]
As described above, by combining the hologram 41 diffracting the incident light and the objective lens 40, the diffraction limits of different orders are utilized on the optical discs 10 and 11 having different substrate thicknesses (t1 and t2), respectively, using the diffracted lights of different orders. Thus, a bifocal lens capable of forming a condensed spot condensed up to is realized. Contrary to the above, the hologram 40 is designed to have a convex lens function, the 0th-order diffracted light is used for the optical disc 11 having the base material thickness t1, and the + 1st order is used for the optical disc 10 having the base material thickness t2. It is also disclosed that the use of folded light reduces focal position fluctuations with respect to wavelength fluctuations during recording and reproduction of the optical disk 10 having the base material thickness t2.
[0011]
In addition, there is disclosed a configuration for performing compatible reproduction on optical disks of different types using light beams having a plurality of wavelengths. As a second conventional example, a configuration in which a wavelength selection phase plate is combined with an objective lens is disclosed in Japanese Patent Application Laid-Open No. Hei 10-334504 and Session We-C-05 of ISOM2001 (page 30 of the proceedings). The configuration disclosed in the session We-C-05 of the ISOM2001 (page 30 of the proceedings) will be described with reference to FIGS. 26, 27A and 27B.
[0012]
FIG. 26 is a sectional view showing a schematic configuration of an optical head device as a second conventional example. In FIG. 26, parallel light emitted from a blue light optical system 51 having a blue light source (not shown) having a wavelength λ1 = 405 nm is transmitted through a beam splitter 161 and a wavelength selection phase plate 205, The light is focused on the information recording surface of an optical disk 9 (third generation optical disk: BD) having a thickness of 0.1 mm. The light reflected by the optical disk 9 follows a reverse path and is detected by a detector (not shown) of the blue light optical system 51. On the other hand, divergent light emitted from a red light optical system 52 having a red light source (not shown) having a wavelength λ2 = 660 nm is reflected by a beam splitter 161, passes through a wavelength selection phase plate 205, and is The light is focused on the information recording surface of an optical disk 10 (second generation optical disk: DVD) having a material thickness of 0.6 mm. The light reflected by the optical disk 10 is detected by a detector (not shown) of the red light optical system 52 following the reverse path.
[0013]
The objective lens 50 is designed to transmit and converge the base material having a thickness of 0.1 mm when parallel light is incident. Therefore, when recording / reproducing a DVD having a base material thickness of 0.6 mm, the objective lens 50 has a thickness of the base material. The difference causes spherical aberration. In order to correct the spherical aberration, the light beam emitted from the red light optical system 52 is converted into divergent light, and the wavelength selection phase plate 205 is used. When divergent light is incident on the objective lens 50, a new spherical aberration occurs. Therefore, the spherical aberration caused by the difference in the base material thickness is canceled by the new spherical aberration, and the wavefront is also corrected by the wavelength selection phase plate 205. ing.
[0014]
27A and 27B are a plan view and a cross-sectional view of the wavelength selection phase plate 205 in FIG. 26, respectively. When the refractive index at the wavelength λ1 is n1 and h = λ1 / (n1-1), the wavelength selection phase plate 205 is configured by steps 205a having heights h and 3h. For the light having the wavelength λ1, the optical path difference caused by the step having the height h is the working wavelength λ1, which is equivalent to the phase difference 2π, and thus is the same as the phase difference 0. Therefore, the step having the height h does not affect the phase distribution of the light beam having the wavelength λ1, and does not affect the recording / reproducing of the optical disk 9 (FIG. 26). On the other hand, for light of wavelength λ2, if the refractive index of wavelength-selective phase plate 205 at wavelength λ2 is n2, h × (n2-1) /λ2≒0.6, that is, an optical path that is not an integral multiple of the wavelength. Make a difference. The above-described aberration correction is performed using the phase difference due to the optical path difference.
[0015]
As a third conventional example, a configuration in which a plurality of objective lenses are mechanically switched and used is disclosed in Japanese Patent Application Laid-Open No. H11-296890.
[0016]
Further, as a fourth conventional example, Japanese Patent Application Laid-Open No. H11-339307 discloses a configuration in which a mirror having a reflecting surface having a different radius of curvature also functions as a rising mirror for bending an optical axis.
[0017]
As a fifth conventional example, as in the first conventional example, a refraction type objective lens and a hologram are combined, and the chromatic aberration generated in the diffracted light of the same order of light of different wavelengths is used to reduce the thickness of the base material. A configuration for correcting the difference is disclosed in Japanese Patent Application Laid-Open No. 2000-81566.
[0018]
As a sixth conventional example, as shown in FIG. 28, a configuration in which a refraction type objective lens 281 and a hologram 282 having a diffraction surface and a refraction surface are combined is described in "BD / DVD / CD compatible light" by Sumitomo Nishioka et al. Pickup technology ”(Preprint of the 50th Spring Alliance Lecture Meeting on Applied Physics, 27p-ZW-10 (2003.3 Kanagawa University)) (disclosed after filing the priority application of the present application). In this sixth conventional example, the hologram 282 generates + 2nd-order diffracted light for a blue light beam and + 1st-order diffracted light for a red light beam to perform chromatic aberration correction. On the other hand, spherical aberration caused by different base material thicknesses is corrected by making divergent light and red light beam convergent light incident on the hologram 282 and the objective lens 281.
[0019]
[Problems to be solved by the invention]
The technical idea of the first conventional example proposes at least the following three technical ideas. First, the compatibility of optical disks with different substrate thicknesses is realized by utilizing the diffraction of the hologram. Second, by changing the design of the inner and outer peripheries, condensed spots with different NAs are formed. By using the diffraction of the hologram, the focal position of the focused spot is changed for optical disks having different substrate thicknesses. These technical ideas do not limit the wavelength of light emitted from the light source.
[0020]
Here, DVD, which is a second generation optical disk, includes a double-layer disk having two recording surfaces. Since the recording surface on the side closer to the objective lens (first recording surface) needs to transmit light to a surface farther from the objective lens, the reflectance is set to about 30%. However, this reflectivity is guaranteed only for red light, and not for other wavelengths. Therefore, in order to reliably reproduce the DVD, it is necessary to use red (wavelength λ2 = 630 nm to 680 nm) light. In addition, in recording and reproduction of a BD which is a third generation optical disk, it is necessary to use blue (wavelength λ1 = 390 nm to 415 nm) light in order to sufficiently reduce the diameter of a focused spot. In this way, the first conventional example does not disclose a configuration for increasing the light use efficiency particularly when different types of optical disks are interchangeable using red and blue light.
[0021]
Further, the first conventional example discloses an embodiment in which a hologram is formed into a convex lens type and + 1st-order diffracted light is used to reduce a focal position shift due to a wavelength change for one type of optical disc. No measures have been disclosed for simultaneously reducing the focal position movement due to wavelength changes for more than one kind of optical disc.
[0022]
In the second conventional example, a wavelength selection phase plate is used as a compatible element. When recording / reproducing a disk with a thick base material, the focal length needs to be extended since the recording surface is farther from the objective lens by the thickness of the base material. The focal length can also be extended by the compatible element having lens power, but the wavelength selective phase plate has no lens power. Further, when the red light is divergent and the lens power is to be realized as in the second conventional example, a large aberration occurs when the objective lens moves due to track following or the like, and the recording / reproducing characteristics deteriorate. .
[0023]
In the third conventional example, since the objective lenses are switched, a plurality of objective lenses are required, the number of components is increased, and it is difficult to reduce the size of the optical head device. Further, the point that a switching mechanism is required also makes it difficult to miniaturize the apparatus.
[0024]
In the fourth conventional example, the objective lens is driven independently of the mirror (see FIGS. 4 to 6 of Japanese Patent Application Laid-Open No. H11-339307). However, since the light beam is converted from the parallel light by the mirror having the radius of curvature as described above, when the objective lens moves by track control or the like, the relative position of the objective lens with respect to the incident light wavefront changes, and aberration occurs. Light collection characteristics deteriorate. Further, the reflecting surface of the mirror is formed of a surface having a radius of curvature, that is, a spherical surface. However, a spherical surface is not enough to correct the difference between the thickness of the base material and the difference between the wavelengths. The secondary aberration cannot be sufficiently reduced.
[0025]
In the fifth conventional example, if this is applied to the red light beam and the blue light beam as they are, the wavelength difference is too large, so that the diffraction efficiency of the same order cannot be increased at the same time, and the light utilization efficiency decreases. There is a problem.
[0026]
In the sixth conventional example, divergent light for the blue light beam and convergent light for the red light beam are made incident on the hologram and the objective lens. Similarly, the light beam reflected from the optical disk and returned is also different in parallelism between the blue light beam and the red light beam, and a servo signal is generated. A photodetector for detection cannot be shared by the blue light beam and the red light beam. That is, there is a problem that two or more photodetectors are required, which leads to an increase in the number of parts and an accompanying increase in cost.
[0027]
The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide an optical disk which is compatible with a red light beam having a substrate thickness of 0.6 mm and a wavelength λ2 (typically about 660 nm). It is an object of the present invention to provide a composite objective lens having a high light use efficiency, which realizes compatible reproduction and compatible recording with an optical disk corresponding to a blue light beam having a wavelength of λ1 (typically about 405 nm) with a material thickness of 0.1 mm. .
[0028]
Another object of the present invention is to provide an optical information device capable of coping with a plurality of optical disks having different recording densities by using a single optical head device by mounting an optical head device using such a compound objective lens. It is in.
[0029]
Further, an object of the present invention is to provide a computer, an optical disk player, a car navigation system, and an optical disk recorder that can stably record or reproduce information by selecting such different types of optical disks according to the purpose by incorporating such an optical information device. To provide an optical disk server.
[0030]
[Means for Solving the Problems]
In order to achieve the above object, a first compound objective lens according to the present invention is a compound object lens including a hologram and a refractive lens, wherein the hologram has a stepped cross-sectional shape formed in at least a partial area. Wherein the step having a stepped cross-sectional shape is an integral multiple of the unit step d1, and the unit step d1 has a wavelength of about 1 wavelength with respect to the first light beam having the wavelength λ1 in the range of 390 nm to 415 nm. This is a step that gives an optical path difference, and one period of the grating consists of steps having a height of 0, 2, 1 and 3 times the unit step d1 from the outer peripheral side of the hologram to the optical axis side. It is characterized by.
[0031]
In the first compound objective lens, the ratio of the widths of the steps of the stepped cross-sectional shape of the lattice is 2: 0, 2, 1 and 3, respectively, corresponding to the unit steps d1 in the order of 2: 3: 3: 2.
[0032]
In the first compound objective lens, the grating is formed only on the inner peripheral portion of the hologram.
[0033]
Further, the first compound objective lens focuses the 0th-order diffracted light of the first light beam through the base material having the thickness t1, and generates the first-order diffracted light of the second light beam having the wavelength λ2 in the range of 630 nm to 680 nm. The folded light is focused through a substrate having a thickness t2 larger than the thickness t1.
[0034]
In order to achieve the above object, a second compound objective lens according to the present invention is a compound objective lens including a hologram and a refraction lens, and the hologram has a step-shaped cross-sectional shape formed at least on an inner peripheral portion. The step having a stepped cross-sectional shape is an integral multiple of the unit step d2, and the unit step d2 is about 1.25 wavelengths for the first light beam having the wavelength λ1 in the range of 390 nm to 415 nm. One period of the grating is composed of steps having a height of 0, 1, 2, 3 times the unit step d2 from the outer peripheral side of the hologram toward the optical axis side. It is characterized by the following.
[0035]
In the second compound objective lens, the ratio of the width of the steps of the stepped cross-sectional shape of the grating is 1 corresponding to the order of 0 times, 1 time, 2 times, and 3 times the unit steps d2, respectively. : 1: 1: 1.
[0036]
In the second compound objective lens, the hologram includes a grating having a step-shaped cross-sectional shape formed on the outer peripheral portion, and a step of the step-shaped cross-sectional shape of the lattice formed on the outer peripheral portion is an integer of a unit step d3. The unit step d3 is a step that gives an optical path difference of about 0.25 wavelength to the first light beam, and one period of the grating formed on the outer peripheral portion is from the outer peripheral side of the hologram to the optical axis side. , The stairs have heights in the order of 0, 1, 2, 3 times the unit step d3.
[0037]
The second compound objective lens condenses the + 1st-order diffracted light of the first light beam through the base material having a thickness of t1, and has a wavelength λ2 in the range of 630 nm to 680 nm and has an inner peripheral portion of the hologram. The -1st-order diffracted light of the second light beam passing through the formed grating is focused through a substrate having a thickness t2 greater than the thickness t1.
[0038]
In order to achieve the above object, a third compound objective lens according to the present invention is a compound object lens composed of a hologram and a refractive lens, wherein the hologram has a sawtooth cross-sectional shape formed at least on an inner peripheral portion. Having a grating having a sawtooth cross-sectional shape, the depth h1 of which gives an optical path difference of about two wavelengths to the first light beam having the wavelength λ1 in the range of 390 nm to 415 nm, and generates the + 2nd-order diffracted light most strongly. And a depth at which + 1st-order diffracted light is generated most strongly for the second light beam having the wavelength λ2 within the range of 630 nm to 680 nm.
[0039]
In order to achieve the above object, a fourth compound objective lens according to the present invention is a compound object lens composed of a hologram and a refraction type lens, and the hologram has a sawtooth cross-sectional shape formed at least on an inner peripheral portion. And a depth h2 of the sawtooth-shaped cross-section provides an optical path difference of about one wavelength with respect to the second light beam having a wavelength λ2 in the range of 630 nm to 680 nm to generate + 1st-order diffracted light most strongly. And a depth at which the + 2nd-order diffracted light is generated most strongly for the first light beam having the wavelength λ1 in the range of 390 nm to 415 nm.
[0040]
To achieve the above object, a fifth compound objective lens according to the present invention is a compound object lens including a hologram and a refraction lens, and the hologram has a sawtooth cross-sectional shape formed at least on an inner peripheral portion. And a depth h4 of the sawtooth cross-sectional shape having an optical path difference of more than 1.7 wavelengths and less than 2 wavelengths for the first light beam having the wavelength λ1 in the range of 390 nm to 415 nm is +2. This is the depth at which the first-order diffracted light is generated most strongly, and the depth at which the + 1st-order diffracted light is generated most strongly for the second light beam having the wavelength λ2 within the range of 630 nm to 680 nm.
[0041]
In the fifth compound objective lens, the depth h4 of the sawtooth cross-sectional shape is preferably a depth that gives an optical path difference of 1.9 wavelength to the first light beam.
[0042]
To achieve the above object, a sixth compound objective lens according to the present invention is a compound objective lens including a hologram and a refractive lens, wherein the hologram has a wavelength λ1 in a range of 390 nm to 415 nm. For the one light beam, the + 2nd-order diffracted light is generated most strongly, and for the second light beam having the wavelength λ2 in the range of 630 nm to 680 nm, the + 1st-order diffracted light is generated most strongly. The + 2nd-order diffracted light of the first light beam passing through the hologram is condensed through the base material having a thickness of t1, and the + 1st-order diffracted light of the second light beam passing through the inner peripheral portion of the hologram is converted to a thickness larger than the thickness t1. The light is condensed through the substrate having the length t2.
[0043]
In the third to sixth compound objective lenses, the hologram includes a grating formed on the outer peripheral portion and having a sawtooth cross-sectional shape, and the depth h3 of the sawtooth-shaped cross-sectional shape of the grating formed on the outer peripheral portion is equal to the first. This is the depth at which the + 1st-order diffracted light is generated most strongly by giving an optical path difference of about one wavelength to the light beam, and the depth at which the + 1st-order diffracted light is generated most strongly also for the second light beam.
[0044]
In the second to sixth compound objective lenses, when the first light beam is focused through the substrate having the thickness t1, the hologram acts as a convex lens to reduce the change in the focal length with respect to the change in the wavelength λ1. It is configured to
[0045]
In the first to sixth compound objective lenses, when the first light beam is condensed through the base material having a thickness of t1 so that the focal position on the optical disk side is separated from the compound objective lens, the hologram is formed on the inner periphery of the hologram. The second light beam passing through the inner portion of the hologram or the second light beam passing through the inner periphery of the hologram is formed such that the second light beam passing through the portion becomes more effective as a convex lens than when condensing through a substrate having a thickness of t2. When the light is condensed through the base material, the function as the convex lens is configured to be smaller than when the first light beam is condensed through the base material having the thickness t1. Thereby, the focal position on the optical disk side can be separated from the compound objective lens, that is, the working distance can be increased.
[0046]
In the third to sixth compound objective lenses, the cross-sectional shape of the grating forming the hologram is a sawtooth shape in which the base material forming the hologram has a slope on the outer peripheral side.
[0047]
In the first to sixth compound objective lenses, it is preferable that the hologram and the refraction lens are fixed integrally.
[0048]
Alternatively, in any of the first to sixth compound objective lenses, it is preferable that the refraction type lens has an aspherical refraction surface opposite to the converging spot. In this case, the hologram is preferably formed integrally with the aspheric surface of the refraction lens.
[0049]
Alternatively, in the first to sixth compound objective lenses, the hologram is preferably formed integrally with the surface of the refractive lens.
[0050]
In the first to sixth compound objective lenses, the numerical aperture at which the first light beam is focused through the base material having the thickness t1 is NAb, and the aperture at which the second light beam is focused through the base material having the thickness t2 is NAb. When the number is NAr, NAb> NAr.
[0051]
To achieve the above object, an optical head device according to the present invention has a first laser light source that emits a first light beam having a wavelength λ1 in a range of 390 nm to 415 nm, and a first laser light source in a range of 630 nm to 680 nm. A second laser light source that emits a second light beam having a wavelength of λ2, and a first light beam emitted from the first laser light source, which is focused on a recording surface of a first optical disc through a base material having a thickness of t1. The first to sixth composites receive the second light beam emitted from the second laser light source and condense it on the recording surface of the second optical disc through the base material having the thickness t2 larger than the thickness t1. Either one of the objective lenses and a photodetector that receives the first and second light beams respectively reflected on the recording surfaces of the first and second optical discs and outputs an electric signal corresponding to the light amount. Octopus And features.
[0052]
An optical head device according to the present invention includes a collimating lens that collimates first and second light beams respectively emitted from first and second laser light sources, and converts a second light beam to a recording surface of a second optical disc. When converging light on the upper side, the collimator lens is brought closer to the second laser light source side, the second light beam is made into diffused light and made incident on the composite objective lens, so that the focal position on the second optical disk side is changed to the composite objective lens. It is preferred to keep away from.
[0053]
In the optical head device according to the present invention, the first and second laser light sources are arranged so that both light emitting points are in an image-forming relationship with respect to the focal positions of the compound objective lens on the first and second optical disk sides. The photodetector is provided in common with the first and second light beams reflected on the recording surfaces of the first and second optical disks, respectively, and receives the first and second light beams to generate a servo signal. To detect.
[0054]
In order to achieve the above object, an optical information device according to the present invention includes an optical head device according to the present invention, a motor for rotating the first and second optical disks, and a signal obtained from the optical head device. A motor, a compound objective lens, and an electric circuit for driving and controlling the first and second laser light sources based on the signal are provided.
[0055]
In the optical information device according to the present invention, the optical head device includes a collimating lens that converts the first and second light beams respectively emitted from the first and second laser light sources into parallel light, and the optical information device according to the present invention. The apparatus controls the movement of the collimating lens toward the second laser light source when a second optical disc having a substrate thickness t2 of 0.6 mm is loaded.
[0056]
To achieve the above object, a computer according to the present invention includes an optical information device according to the present invention, input means for inputting information, information input from the input means, and information reproduced from the optical information device. An arithmetic unit for performing an arithmetic operation based on the information; and output means for displaying or outputting information input from the input unit, information reproduced from the optical information unit, and a result calculated by the arithmetic unit. It is characterized by.
[0057]
In order to achieve the above object, an optical disc player according to the present invention includes the optical information device according to the present invention, and a decoder for converting an information signal obtained from the optical information device into an image signal.
[0058]
In order to achieve the above object, a car navigation system according to the present invention includes the optical information device according to the present invention, and a decoder that converts an information signal obtained from the optical information device into an image signal. .
[0059]
In order to achieve the above object, an optical disc recorder according to the present invention includes the optical information device according to the present invention, and an encoder that converts an image signal into an information signal to be recorded on the optical information device.
[0060]
In order to achieve the above object, an optical disc server according to the present invention includes an optical information device according to the present invention, an information signal input from outside, recorded in the optical information device, and an information signal reproduced from the optical information device. And an input / output terminal for outputting to the outside.
[0061]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0062]
(Embodiment 1)
FIG. 1 is a cross-sectional view showing one configuration example of the optical head device according to the first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a first light beam that emits a first light beam having a wavelength λ1 (390 nm to 415 nm; a wavelength of 390 nm to 415 nm is generally referred to as about 405 nm because 405 nm is used in many cases). 1 is a blue laser light source as a laser light source, and 20 is a second light beam having a wavelength λ2 (630 nm to 680 nm: a wavelength of 630 nm to 680 nm is generally used, and thus a wavelength of 630 nm to 680 nm is generally referred to as about 660 nm). A red laser light source as a second laser light source that emits light, 8 is a collimating lens, 12 is a rising mirror that bends the optical axis, 13 is a hologram (diffractive optical element), and 14 is an objective lens as a refractive lens. . Here, the hologram 13 and the objective lens 14 constitute the composite objective lens in the present embodiment.
[0063]
Reference numeral 9 denotes a substrate thickness t1 of about 0.1 mm (a substrate thickness of 0.06 mm to 0.11 mm is referred to as about 0.1 mm) or a thinner substrate thickness, which is recorded / reproduced by a first light beam of wavelength λ1. BD (first optical disk) 10, which is a third generation optical disk, has a base material thickness t2 of about 0.6 mm (a base material thickness of 0.54 mm to 0.65 mm is called about 0.6 mm), This is a second-generation optical disc (second optical disc) such as a DVD that is recorded / reproduced by a second light beam having a wavelength λ2. Although the first optical disk 9 and the second optical disk 10 show only the base material from the light incident surface to the recording surface, actually, the mechanical strength is reinforced and the outer shape is 1.2 mm which is the same as the CD. In order to make, the protection plate is stuck. A protective material having a thickness of 0.6 mm is attached to the second optical disk 10. A protective material having a thickness of 1.1 mm is attached to the first optical disk 9. In the drawings referred to throughout the embodiments, protective materials are omitted for simplicity of illustration.
[0064]
Preferably, the blue laser light source 1 and the red laser light source 20 are semiconductor laser light sources, so that the optical head device and the optical information device using the same can be reduced in size, weight, and power consumption.
[0065]
When performing recording / reproduction on the first optical disc 9 having the highest recording density, the blue light beam 61 having the wavelength λ1 emitted from the blue laser light source 1 is reflected by the beam splitter 4 and converted into circularly polarized light by the 波長 wavelength plate 5. Become. The quarter-wave plate 5 is designed to act as a quarter-wave plate for both the blue light beam 61 having the wavelength λ1 and the red light beam 62 having the wavelength λ2. The blue light beam 61 that has passed through the 波長 wavelength plate 5 is made substantially collimated by the collimator lens 8, the optical axis is bent by the rising mirror 12, and the hologram 13 and the objective lens 14 form the first optical disk 9. The light is focused on the information recording surface 91 (see FIG. 2) through a base material having a thickness of about 0.1 mm.
[0066]
The blue light beam 61 reflected by the information recording surface 91 follows the original optical path in the reverse direction (return path), becomes linearly polarized light in a direction perpendicular to the initial direction by the quarter-wave plate 5, and almost completely forms the beam splitter 4. The light passes through, is totally reflected by the beam splitter 16, is diffracted by the detection hologram 31, is further extended in focal length by the detection lens 32, and is incident on the photodetector 33. By calculating an output signal from the photodetector 33, a servo signal and an information signal used for focus control and tracking control can be obtained.
[0067]
As described above, the beam splitter 4 is a polarization splitting film that totally reflects the linearly polarized light in one direction and completely transmits the linearly polarized light in the direction perpendicular to the blue light beam of the wavelength λ1. Further, as described later, the beam splitter 4 completely transmits the red light beam 62 emitted from the red laser light source 20 for the red light beam having the wavelength λ2. As described above, the beam splitter 4 is an optical path branching element having wavelength selectivity as well as polarization characteristics.
[0068]
Next, when performing recording or reproduction on the second optical disk 10, a red light beam 62 of substantially linearly polarized light emitted from the red laser light source 20 and having a wavelength λ2 passes through the beam splitter 16 and the beam splitter 4, 8, the optical axis is bent by the rising mirror 12, and the information recording surface 101 (see FIG. 2) is passed through the base material having a thickness of about 0.6 mm of the second optical disc 10 by the hologram 13 and the objective lens 14. ).
[0069]
The red light beam reflected by the information recording surface 101 reverses the original optical path (return path), passes through the beam splitter 4 almost completely, is totally reflected by the beam splitter 16, is diffracted by the detection hologram 31, and is further diffracted. The focal length is extended by the detection lens 32, and the light enters the photodetector 33. By calculating an output signal from the photodetector 33, a servo signal and an information signal used for focus control and tracking control can be obtained.
[0070]
As described above, in order to obtain the servo signals of the first optical disk 9 and the second optical disk 10 from the common photodetector 33, the blue laser light source 1 and the red laser They are arranged so as to form an image with respect to a common position on the side. Thus, the number of photodetectors and the number of wirings can be reduced.
[0071]
The beam splitter 16 is a polarization splitting film that totally transmits linearly polarized light in one direction and totally reflects linearly polarized light in a direction perpendicular to the red light beam 62 having the wavelength λ2. Further, the beam splitter 16 completely transmits the blue light beam 61 having the wavelength λ1. Thus, similarly to the beam splitter 4, the beam splitter 16 is an optical path branching element having wavelength characteristics as well as polarization characteristics.
[0072]
FIG. 2 is a cross-sectional view showing a specific example of the composite objective lens including the hologram 13 and the objective lens 14 in FIG. In FIG. 2, reference numeral 131 denotes a hologram as a diffraction-type optical element. The hologram 131 transmits a large amount of light without diffracting the blue light beam 61 having the wavelength λ1 and causes diffraction of the red light beam 62 having the wavelength λ2 as described later. It should be noted that light that has not been diffracted when transmitted through the diffraction element is also referred to as 0th-order diffracted light, and is hereinafter referred to as 0th-order diffracted light.
[0073]
Since the hologram 131 transmits the blue light beam 61 having the wavelength λ1 as the 0th-order diffracted light, the wavefront of the blue light beam 61 is not converted. Therefore, the objective lens 141 is designed to focus the substantially parallel blue light beam 61 having the wavelength λ1 onto the information recording surface 91 through the base material having the thickness t1 of the first optical disc 9. Since the hologram 131 does not perform wavefront conversion on the blue light beam 61, it is not necessary to make the relative position between the hologram 131 and the objective lens 141 highly accurate from the viewpoint of recording and reproduction of the first optical disc 9. The allowable position error between the objective lens 141 and the hologram 131 can be increased with respect to the blue light beam 61 having the wavelength λ1 for performing recording and reproduction on the first optical disc 9 having the shortest wavelength and the highest recording density. In addition, when recording / reproducing an optical disk having a lower recording density using a light beam having a longer wavelength, the relative position between the hologram 131 and the objective lens 141 may be considered. Therefore, the allowable error amount of the relative position can be further increased, and an optical head device having excellent productivity can be configured.
[0074]
Next, the operation of the hologram 131 when recording and reproducing the optical disk 10 using the red light beam 62 will be described in detail. The hologram 131 transmits the blue light beam 61 having the wavelength λ1 as the zero-order light, and diffracts the red light beam 62 having the wavelength λ2. Then, the objective lens 141 condenses the red light beam 62 on the information recording surface 101 through the base material of the second optical disc 10 having a thickness of about 0.6 mm. Here, the second disc 10 has a base material thickness of 0.6 mm from the light incident surface to the information recording surface 101, and therefore, the recording and reproduction of the first optical disc 9 having the base material thickness of 0.1 mm is performed. It is necessary to make the focal position farther from the objective lens 141 than the focal position when performing the operation. As shown in FIG. 2, by converting the red light beam 62 into divergent light by wavefront conversion, correction of the focal position and correction of spherical aberration due to a difference in the thickness of the base material are realized.
[0075]
The red light beam 62 having the wavelength λ2 undergoes wavefront conversion by the hologram 131. Therefore, if there is an error in the relative position between the hologram 131 and the objective lens 141, the wavefront as designed does not enter the objective lens 141, and the wavefront incident on the second optical disc 10 has an aberration, which deteriorates the light-collecting characteristics. Therefore, desirably, the hologram 131 and the objective lens 141 are integrally fixed by the support 34, or the hologram 131 is formed directly on the surface of the objective lens 141, so that the common driving unit 15 ( Driving is performed integrally according to FIG. 1).
[0076]
FIG. 3A is a plan view showing the structure of the hologram 131, and FIG. 3B is a sectional view similar to FIG. The hologram 131 has a different structure between the inside (inner periphery 131C) of the inner / outer boundary 131A and the outside (the outer periphery 131B between the inner / outer boundary 131A and the effective range 131D). The inner peripheral portion 131C is an area including the intersection of the hologram 131 and the optical axis, that is, the center. This area is used both when recording and reproducing the second optical disk 10 using the red light beam 62 and when recording and reproducing the first optical disk 9 using the blue light beam 61.
[0077]
Therefore, a concentric diffraction grating is formed on the inner peripheral portion 131C. Regarding the outer peripheral portion 131B, the numerical aperture NAb when recording and reproducing the first optical disc 9 with the blue light beam 61 is larger than the numerical aperture NAr when recording and reproducing the second optical disc 10 with the red light beam 62 ( NAb> NAr), the blue light beam 61 and the red light beam 62 are focused on the corresponding first optical disc 9 and second optical disc 10, respectively. It is necessary to provide an outer peripheral portion 131B such that the red light beam 62 has an aberration with respect to the second optical disk 10.
[0078]
In the present embodiment, no hologram is formed on outer peripheral portion 131B. By designing the objective lens 141 such that the blue light beam 61 transmitted through the outer peripheral portion 131B is transmitted through the base material of about 0.1 mm with respect to the first optical disc 9, the outer peripheral portion 131B is focused. The passing red light beam 62 is not focused on the second optical disk 10, and the condition of NAb> NAr can be realized.
[0079]
4A and 4B are a cross-sectional view showing a physical step during one period (p1) of a grating formed on the inner peripheral portion 131C of the hologram 131 shown in FIG. 3A, and a red light corresponding to FIG. 4A. FIG. 6 is a diagram illustrating a phase modulation amount for a beam 62 (wavelength λ2). Here, hologram 131 according to the present embodiment has a lens function, and the grating pitch is locally changed. It should be noted that the lattice pitch merely takes a point at an arbitrary point on the hologram 131 as a representative. Hereinafter, the same applies to other embodiments. 4A and 4B, the lower side represents the hologram base material side (higher refractive index side), and the upper side represents the air side (low refractive index side). Hereinafter, the same definitions are used in similar drawings.
[0080]
In FIG. 4A, the vertical direction indicates a step. In this application, a shape obtained by combining rectangular shapes in this way is referred to as a step-like shape. nb is the refractive index of the hologram material with respect to the blue light beam 61 (wavelength λ1). If the hologram material is, for example, BK7, nb = 1.5302. Here, BK7 is illustrated as an example only. It is also possible to use another glass material, further, a polycarbonate or a polycycloolefin-based resin material. This is the same in the following embodiments.
[0081]
One unit of the step is an amount such that the optical path length difference with respect to the blue light beam 61 is about one wavelength, that is, the phase difference is about 2π. The unit step d1 is d1 = λ1 / (nb-1) = 0.664 μm.
[0082]
When the step of the grating is set to an integral multiple of the unit step d1 and is formed in a stepped cross-sectional shape, the phase modulation amount for the blue light beam 61 due to this step is an integral multiple of 2π, which is substantially due to the absence of phase modulation. Become.
[0083]
On the other hand, assuming that the refractive index of the hologram material with respect to the red light beam 62 is nr, when the hologram material is BK7, since nr = 1.5142, the optical path length difference generated in the red light beam 62 by the unit step d1 is d1 × (Nr-1) /λ2=0.595, that is, about 0.6 times the wavelength λ2.
[0084]
Therefore, as shown in FIG. 4A, when the step is formed in a step shape from the right in the order of 0 times, 2 times, 1 time, and 3 times d1, first, as described above, the blue light beam 61 In principle, no phase modulation occurs and no diffraction occurs, that is, the 0th-order diffracted light becomes the strongest. Then, for the red light beam 62, the optical path length difference changes in the order of 0 times, 1.2 times, 0.6 times, and 1.8 times the wavelength λ2. Since it is the same as the absence of phase modulation, the wavelength is substantially changed to a step shape of 0, 0.2, 0.6, and 0.8 times the wavelength λ2. As shown. With respect to such a change in the step shape, the diffraction efficiency was calculated by changing the width of each step in one cycle. As shown in FIG. 4A, the ratio of the step width was set to about 2: 3. : 3: 2, the diffraction efficiency of the + 1st-order diffracted light of the red light beam 62 was the highest, and according to scalar calculation, it was found that about 75% was obtained.
[0085]
Note that the ratio of the step width here is the physical length ratio as it is when the surrounding grid pitch is constant, but is changed in accordance with the change when the surrounding grid pitch is rapidly changing. It is desirable. This point is the same in the embodiments described later. The step-like structure in which phase modulation does not occur for the blue light beam 61 and diffracts for the red light beam 62 is disclosed in Japanese Patent Application Laid-Open No. 10-334504, which is cited as a second conventional example, and the session We of ISOM2001. Although it is also disclosed in −C-05 (page 30 of the proceedings), as in the present embodiment, the steps are formed in a staircase shape in which the unit steps d1 are 0 times, 2 times, 1 time, and 3 times in order. It is not shown that the ratio of the step width is about 2: 3: 3: 2.
[0086]
According to the configuration of the present embodiment, first, the step is up to three times the unit step d1, and is minimized in the form of a four-step staircase. This is due to manufacturing errors and wall surfaces of the stairs (surfaces that rise up and down in the figure). By minimizing the light amount loss and finding the optimum ratio of the step width, the light amount of the + 1st-order diffracted light of the red light beam 62 can be increased, which is particularly advantageous for securing the recording light amount. Such effects cannot be obtained.
[0087]
Further, as an overall configuration of the optical head device, an additional effective configuration example will be described below. The following is valid in all embodiments. However, an important point of this embodiment is that a hologram 13 (131 in this embodiment) for realizing compatible reproduction / recording of the first optical disc 9 and the second optical disc 10 and an objective lens used in combination therewith 14 (141 in the present embodiment), and other configurations described below include the beam splitter 16, the detection lens 32, and the detection hologram 31, even in the configurations already described, including the following. However, other configurations can be used as appropriate.
[0088]
In FIG. 1, a tracking error signal of the first optical disc 9 can be obtained by disposing a three-beam grating (diffraction element) 3 between the blue laser light source 1 and the beam splitter 4 so as to obtain a well-known differential push-pull (DPP). ) Method.
[0089]
When two directions perpendicular to the optical axis are defined as the x direction and the y direction, for example, a beam shaping element 2 for enlarging only the x direction is further disposed between the blue laser light source 1 and the beam splitter 4. By doing so, the far-field image of the blue light beam 61 can be approximated to an intensity distribution close to a point symmetric system with the optical axis as the center, and the light use efficiency can be improved. The beam shaping element 2 can be configured by using a double-sided cylindrical lens or the like.
[0090]
By further arranging a three-beam grating (diffraction element) 22 between the red laser light source 20 and the beam splitter 16, a tracking error signal of the second optical disc 10 is detected by a well-known differential push-pull (DPP) method. It is also possible.
[0091]
It is also effective to change the parallelism of the light beam by moving the collimating lens 8 in the direction of the optical axis (the horizontal direction in FIG. 1). If there is a thickness error of the base material or a base material thickness caused by the interlayer thickness when the first optical disc 9 is a two-layer disc, spherical aberration occurs. The spherical aberration can be corrected. As described above, the spherical aberration can be corrected by moving the collimating lens 8 when the numerical aperture NA of the condensed light with respect to the first optical disc 9 is 0.85, which is about several 100 mλ, and the thickness of the substrate is ± 30 μm. Can also be corrected.
[0092]
However, when recording / reproducing a DVD using the objective lens 14 corresponding to the base material thickness of 0.1 mm, it is necessary to compensate for the base material thickness difference of 0.5 mm or more. The ability to correct spherical aberration is insufficient, and wavefront conversion by the hologram 13 (131 as an example) is required. However, when recording / reproducing the second optical disk 10 using the red light beam 62, the objective lens 14 is moved by moving the collimating lens 8 to the left side in FIG. The red light beam 62 directed to the hologram 13 is divergent light, the focused spot on the second optical disk 10 is further separated from the objective lens 14, and a part of the aberration due to the thickness of the base material is corrected. It is also possible to increase the hologram pitch by reducing the hologram pitch, thereby facilitating the creation of the hologram 13.
[0093]
Further, the beam splitter 4 is configured to partially transmit (eg, about 10%) linearly polarized light emitted from the blue laser light source 1, and the transmitted light beam is further condensed by a condenser lens 6 to a photodetector 7. By monitoring the change in the amount of light emitted from the blue laser light source 1 using a signal obtained from the photodetector 7 and feeding back the change in the amount of light, the amount of light emitted from the blue laser light source 1 is kept constant. Control can also be performed.
[0094]
Further, the beam splitter 4 is configured to partially (eg, about 10%) reflect linearly polarized light emitted from the red laser light source 20, and the reflected light beam is further reflected by the condenser lens 6 to a photodetector. 7, the change in the amount of light emitted from the red laser light source 20 is monitored using the signal obtained from the photodetector 7, and the change in the amount of light is fed back to keep the amount of light emitted from the red laser light source 20 constant. Control to keep can also be performed.
[0095]
Further, as shown in FIG. 2, in order to set a numerical aperture (NA) for converging the blue light beam 61 on the first optical disc 9 to a desired value (about 0.85), the aperture limiting means 341 is used. Is effective. In particular, when the objective lens 141 and the hologram 131 are integrally fixed by using the support 34 and are moved by the driving means 15 (FIG. 1), the shape of the support 34 is, for example, as shown in FIG. If the opening limiting means 341 is formed integrally and serves as the above, the number of parts can be reduced.
[0096]
In FIG. 2, a portion of the objective lens 14 (for example, 141) close to the second optical disc 10 and away from the optical axis and through which the blue light beam 61 does not pass is cut out (forming a cutout portion 1411). Alternatively, by forming the optical disk without any members from the beginning, it is possible to prevent the objective lens 14 from coming into contact with the cartridge when recording or reproducing an optical disk in the cartridge.
[0097]
(Embodiment 2)
Next, a second embodiment of the present invention will be described. The overall configuration of the optical head device according to the present embodiment is the same as the configuration shown in FIG. 1 referred to in the description of the first embodiment. In the present embodiment, the configurations of the hologram 13 and the objective lens 14 shown in FIG. 1 are different from those of the first embodiment.
[0098]
FIG. 5 is a cross-sectional view showing a specific example of the composite objective lens including the hologram 13 and the objective lens 14 shown in FIG. In FIG. 5, reference numeral 132 denotes a hologram. The hologram 132 diffracts the blue light beam 61 having the wavelength λ1 to exert a convex lens function, and diffracts the red light beam 62 having the wavelength λ2 to exert a concave lens function as described later. Here, the lowest order diffraction that exerts a convex lens effect is defined as + 1st order diffraction. Then, the red light beam 62 is subjected to a concave lens effect by -1st-order diffraction conjugate with the + 1st-order diffracted light, that is, the diffraction directions at the respective points on the hologram 132 are reversed.
[0099]
After the blue light beam 61 having the wavelength λ1 is diffracted by the hologram 132 and subjected to the convex lens action, the objective lens 142 further converges the blue light beam 61 to pass information through the base material of the first optical disc 9 having a thickness of about 0.1 mm. It is designed to converge on the recording surface 91.
[0100]
Next, the operation of the hologram 132 when recording / reproducing the second optical disk 10 using the red light beam 62 will be described in detail. The hologram 132 diffracts the red light beam 62 having the wavelength λ2 by −1st order, and exerts a concave lens function. Then, the objective lens 142 focuses the red light beam 62 on the information recording surface 101 through the base material of the second optical disc 10 having a thickness of about 0.6 mm. Here, the second disk 10 has a base material thickness from the light incident surface to the information recording surface 101 of 0.6 mm, which is a large thickness. The focal position needs to be farther from the objective lens 142 than the position. As shown in FIG. 5, by converting the blue light beam 61 into convergent light and the red light beam 62 into divergent light by wavefront conversion, this focal position correction and correction of spherical aberration due to a difference in substrate thickness are realized. I have.
[0101]
Both the blue light beam 61 having the wavelength λ1 and the red light beam 62 having the wavelength λ2 undergo wavefront conversion by the hologram 132. Therefore, if there is an error in the relative position between the hologram 132 and the objective lens 142, the wavefront as designed does not enter the objective lens 142, and the wavefront incident on the first optical disk 9 or the second optical disk 10 has an aberration and condenses. The characteristics deteriorate. Therefore, the hologram 132 and the objective lens 142 are desirably fixed integrally, and the drive is performed integrally by the common drive unit 15 (FIG. 1) during the focus control and the tracking control.
[0102]
FIG. 6A is a plan view showing the structure of the hologram 132, and FIG. 6B is a sectional view similar to FIG. The hologram 132 has a different structure between the inside (inner periphery 132C) of the inner / outer boundary 132A and the outer (outer periphery 132B between the inner / outer boundary 132A and the effective range 132D). The inner peripheral portion 132C is an intersection point between the hologram 132 and the optical axis, that is, a region including the center. This area is used both when recording / reproducing the second optical disc 10 using the red light beam 62 and when recording / reproducing the first optical disc 9 using the blue light beam 61. Therefore, the diffraction grating of the inner peripheral portion 132C and the portion of the objective lens 142 through which the red light beam 62 diffracted therethrough passes, the + 1st-order diffracted light of the blue light beam 61 to the first optical disc 9 and the red light beam 62 The first-order diffracted light is designed to be focused on the second optical disc 10.
[0103]
Regarding the outer peripheral portion 132B, the numerical aperture NAb when recording / reproducing the first optical disc 9 with the blue light beam 61 is larger than the numerical aperture NAr when recording / reproducing the second optical disc 10 with the red light beam 62 ( NAb> NAr), so that the blue light beam 61 and the red light beam 62 respectively correspond to the first optical disk 9 and the second optical disk 10.
Only the + 1st-order diffracted light of the blue light beam 61 is condensed on the first optical disc 9 around the inner peripheral portion condensed with respect to the It is necessary to provide the outer peripheral portion 132B and the corresponding outer peripheral portion of the objective lens 142 so as to have aberration. That is, although not shown, it is desirable that the objective lens 142 be designed differently depending on the inner and outer circumferences, similarly to the hologram 132. Thereby, the optimum NA, that is, the condition of NAb> NAr can be realized.
[0104]
7A, 7B, and 7C are cross-sectional views each showing a physical step during one period (p2) of the grating formed on the hologram 132, and the blue light beam 61 (wavelength λ1) corresponding to FIG. 7A. 7A and 7B are diagrams showing a phase modulation amount for the red light beam 62 (wavelength λ2) corresponding to FIG. 7A.
[0105]
In FIG. 7A, the vertical direction indicates a step. nb is the refractive index of the hologram material with respect to the blue light beam 61. If the hologram material is, for example, BK7, nb = 1.5302. Assuming that one unit of the step is an amount such that the optical path length difference is about 1.25 wavelengths with respect to the blue light beam, that is, the phase difference is about 2π + π / 2, the unit step d2 is d2 = 1.25 × λ1 / (nb -1) = 0.955 μm.
[0106]
When the step of the grating is an integral multiple of the unit step d2 and the cross section has a step-like shape with a step width ratio of 1: 1: 1: 1 in four steps, the phase modulation amount for the blue light beam 61 due to this shape is 2π + π /. This is an integer multiple of 2, which means that the phase modulation amount is substantially π / 2 per stage.
[0107]
On the other hand, assuming that the refractive index of the hologram material with respect to the red light beam 62 is nr, when the hologram material is BK7, nr = 1.5142, so the optical path length difference generated in the red light beam 62 by the unit step d2 is: d2 × (nr-1) /λ2=0.744, that is, about ／ of the wavelength λ2, and the phase modulation amount is about −π / 2 per stage.
[0108]
Therefore, as shown in FIG. 7A, when the step of the grating is an integral multiple of the unit step d2 and has a four-step stair-like cross-sectional shape, the step is superimposed on the blue light beam 61. As shown, the amount of phase modulation changes by π / 2 per stage, that is, the optical path length difference changes by +0.25 times λ1. When the physical shape of the step is made as shown in FIG. 7A, the diffraction efficiency of the + 1st-order diffracted light, which is affected by the convex lens, is calculated to be about 80% (scalar calculation), and the blue light beam 61 is the strongest among the diffraction orders. Become.
[0109]
Then, when the steps are superimposed on the red light beam 62, as shown in FIG. 7C, the phase modulation amount changes by -π / 2 per step, that is, the optical path length difference is -0.25 of λ2. It changes by a factor of two. When the physical shape of the step is made as shown in FIG. 7A, the red light beam 62 is calculated to have a diffraction efficiency of about 80% of the -1st-order diffracted light subjected to the concave lens action (scalar calculation). Become stronger.
[0110]
The hologram configuration having a step-like cross-sectional shape such that an optical path length difference of 1.25 times the wavelength per step described in the present embodiment is obtained, and the + 1st-order diffracted light and the -1st-order diffracted light each having a diffraction efficiency of 50% or more are obtained Neither of the above-mentioned prior arts discloses a compatible recording / reproducing of a heterogeneous disc using the next-order diffracted light.
[0111]
In the present embodiment, the blue light beam 61 and the red light beam 62 have diffraction orders of + 1st-order diffraction light and -1st-order diffraction light, respectively, and have a difference of 2 due to the novel configuration described above. Therefore, the minimum pitch of the hologram required to exhibit the same aberration correction effect and the effect of moving the focal position can be made wider than that of the first embodiment, and the hologram can be easily manufactured. Can be easily obtained.
[0112]
The hologram 132 has a convex lens function for the blue light beam 61. The diffractive effect cancels out the chromatic aberration with respect to a wavelength change within several nm, particularly the wavelength dependence of the focal length, when combined with the objective lens 142, which is a refraction type convex lens, because the chromatic dispersion is in the opposite direction to the refraction effect. There is an advantage that it can be reduced.
[0113]
Further, as the overall configuration of the optical head device, it is possible to combine the configurations additionally described in the first embodiment.
[0114]
(Embodiment 3)
Next, a third embodiment of the present invention will be described. The overall configuration of the optical head device according to the present embodiment is the same as the configuration shown in FIG. 1 referred to in the description of the first embodiment. In the present embodiment, the configuration of the hologram 13 shown in FIG. 1 is different from the first and second embodiments.
[0115]
8A and 8B are a plan view and a cross-sectional view, respectively, showing a specific example of the hologram 13 shown in FIG. 8A and 8B, reference numeral 133 denotes a hologram. The inner peripheral portion 133C of the hologram 133 is the same as the inner peripheral portion 132C of the hologram 132 illustrated and described in the second embodiment. The outer peripheral portion 133B has the same grating pitch as the outer peripheral portion 132B of the hologram 132 illustrated and described in the second embodiment. However, as shown in FIG. 8B, the cross-sectional shape of the lattice formed on the outer peripheral portion 133B is different. different.
[0116]
9A, 9B, and 9C are cross-sectional views each showing a physical step during one period (p3) of a grating formed on the outer peripheral portion 133B of the hologram 133, and the blue light beam 61 corresponding to FIG. 9A. FIG. 9B is a diagram illustrating a phase modulation amount with respect to (wavelength λ1) and a diagram illustrating the phase modulation amount with respect to the red light beam 62 (wavelength λ2) corresponding to FIG. 9A.
[0117]
In FIG. 9A, the vertical direction indicates a step. nb is the refractive index of the hologram material with respect to the blue light beam 61. If the hologram material is, for example, BK7, nb = 1.5302.
[0118]
Assuming that one unit of the step is an amount such that the optical path length difference with respect to the blue light beam 61 is about 0.25 wavelength, that is, the phase difference is about π / 2, the unit step d3 is d3 = 0.25 × λ1 / ( nb-1) = 0.191 [mu] m.
[0119]
On the other hand, assuming that the refractive index of the hologram material with respect to the red light beam 62 is nr, nr = 1.5142 when the hologram material is BK7, the optical path length difference generated in the red light beam 62 by the unit step d3 is: d3 × (nr-1) /λ2=0.149, that is, about 0.15 times the wavelength λ2, and the amount of phase modulation is about 0.3π per stage.
[0120]
Therefore, as shown in FIG. 9A, when the steps of the grating are set to an integral multiple of the unit step d3 and the width ratio of each step is substantially 1: 1: 1: 1 in four steps, blue light can be obtained. As shown in FIG. 9B, when the steps are superimposed on the beam 61, as shown in FIG. 9B, the phase modulation amount changes by π / 2 per step, that is, the optical path length difference changes by +0.25 times λ1. When the physical shape of the step is formed as shown in FIG. 9A, the diffraction efficiency of the + 1st-order diffracted light, which is subjected to the convex lens action, is calculated to be about 80% (scalar calculation), and the blue light beam 61 is the strongest among the diffraction orders. Become.
[0121]
When the steps are superimposed on the red light beam 62, as shown in FIG. 9C, the phase modulation amount changes by -0.3π per step, that is, the optical path length difference is 0.15 times λ2. Change by one. When the physical shape of the step is made as shown in FIG. 9A, the red light beam 62 is calculated to have a diffraction efficiency of about 50% of the + 1st order diffracted light subjected to the convex lens action (scalar calculation), and is the strongest among the diffraction orders. However, since this is the same order as the blue light beam 61, the aberration is large with respect to the second optical disk 10 and the light is not condensed. Further, the red light beam 62 has a sufficiently low diffraction efficiency of 10% or less of the -1st-order diffracted light that is subjected to the concave lens effect. Accordingly, by reducing the numerical aperture of the red light beam 62 with respect to the second optical disc 10, the numerical aperture NAb when recording / reproducing the first optical disc 9 with the blue light beam 61 is increased. Accordingly, the condition that the numerical aperture NAr when recording / reproducing is larger (NAb> NAr) can be easily realized.
[0122]
The hologram configuration described in the present embodiment, which has a step-like cross-sectional shape in which only the outer peripheral portion 133B of the hologram 133 produces a difference in optical path length of 0.25 times the wavelength per step, or the inner peripheral portion 133C outputs conjugate light. Neither of the above-mentioned prior arts discloses the compatible recording / reproduction of a different kind of disc used.
[0123]
In the present embodiment, in addition to the advantages described in the second embodiment, the new configuration described above can reduce the grid height of the outer peripheral portion 133B where the grid pitch of the hologram 133 is relatively narrow. It can be easily manufactured, and by reducing the numerical aperture of the red light beam 62 with respect to the second optical disk 10, the numerical aperture NAb when recording / reproducing the first optical disk 9 with the blue light beam 61 is reduced. There is an advantage that the condition that the numerical aperture NAr when recording / reproducing with the light beam 62 is larger (NAb> NAr) can be easily realized.
[0124]
Further, as the overall configuration of the optical head device, it is possible to combine the configurations additionally described in the first embodiment.
[0125]
(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. The overall configuration of the optical head device according to the present embodiment is the same as the configuration shown in FIG. 1 referred to in the description of the first embodiment. In the present embodiment, the configurations of the hologram 13 and the objective lens 14 shown in FIG.
[0126]
FIG. 10 is a cross-sectional view showing a specific example of the composite objective lens including the hologram 13 and the objective lens 14 shown in FIG. In FIG. 10, reference numeral 134 denotes a hologram. The hologram 134 diffracts the blue light beam 61 having the wavelength λ1 and exerts a convex lens function. The hologram 134 diffracts the red light beam 62 having the wavelength λ2 as described later and is a convex lens which is weaker than the blue lens 61. Has an effect. Here, the lowest order diffraction that exerts a convex lens effect is defined as + 1st order diffraction. In the present embodiment, the hologram 134 is designed so that +2 order diffraction occurs most strongly for the blue light beam 61. By doing so, for the red light beam 62, + 1st-order diffraction occurs most strongly. As a result, although the red light beam 62 has a longer wavelength than the blue light beam 61, the diffraction angle at each point on the hologram 134 is small. In other words, the convex lens action when the hologram 134 diffracts the blue light beam 61 having the wavelength λ1 is stronger than the convex lens action exerted on the red light beam 62 having the wavelength λ2. In other words, the red light beam 62 is subjected to the convex lens effect by the hologram 134, but is relatively diffracted by the diffraction based on the effect of the blue light beam 61.
[0127]
The objective lens 144 further converges the blue light beam 61 after the blue light beam 61 having the wavelength λ1 is subjected to + 2nd-order diffraction by the hologram 134 and acts as a convex lens, and the first optical disk 9 has a thickness of about 0.1 mm. It is designed to converge on the information recording surface 91 through the base material.
[0128]
Next, the function of the hologram 134 when recording / reproducing the second optical disk 10 using the red light beam 62 will be described in detail. The hologram 134 diffracts the red light beam 62 having the wavelength λ2 by + 1st order to exert a convex lens function. Then, the objective lens 144 condenses the red light beam 62 on the information recording surface 101 through the base material of the second optical disc 10 having a thickness of about 0.6 mm. Here, the second optical disc 10 has a base material thickness of 0.6 mm from the light incident surface to the information recording surface 101, and the focus when recording / reproducing the first optical disc 9 having the base material thickness of 0.1 mm. The focus position needs to be farther from the objective lens 144 than the position. As shown in FIG. 10, the blue light beam 61 is converted into convergent light by wavefront conversion, and the convergence of the red light beam 62 is made smaller than the convergence of the blue light beam 61. Correction of spherical aberration due to the difference is realized.
[0129]
Both the blue light beam 61 of wavelength λ1 and the red light beam 62 of wavelength λ2 undergo wavefront conversion by the hologram 134. Therefore, if there is an error in the relative position between the hologram 134 and the objective lens 144, the wavefront as designed does not enter the objective lens 144, and the wavefront incident on the first optical disk 9 or the second optical disk 10 has an aberration and condenses. The characteristics deteriorate. Therefore, the hologram 134 and the objective lens 144 are desirably fixed integrally, and the drive is performed integrally by the common drive means 15 (FIG. 1) during focus control and tracking control.
[0130]
FIG. 11A is a plan view showing the structure of the hologram 134, and FIG. 11B is a sectional view similar to FIG. The hologram 134 has a different structure between the inner (outer peripheral portion 134C) and the outer (outer peripheral portion 134B between the inner and outer boundary 134A and the effective range 134D) the inner and outer boundary 134A. The inner peripheral portion 134C is a region including the intersection of the hologram 134 and the optical axis, that is, the center. This area is used when recording / reproducing the second optical disc 10 using the red light beam 62 and when recording / reproducing the first optical disc 9 using the blue light beam 61. Accordingly, the diffraction grating of the inner peripheral portion 134C and the portion of the objective lens 144 through which the red light beam 62 diffracted therethrough passes, the + 2nd-order diffracted light of the blue light beam 61 to the first optical disc 9 and the red light beam 62 The first order diffracted light is designed to be focused on the second optical disc 10.
[0131]
Regarding the outer peripheral portion 134B, the numerical aperture NAb when recording / reproducing the first optical disc 9 with the blue light beam 61 is larger than the numerical aperture NAr when recording / reproducing the second optical disc 10 with the red light beam 62 ( NAb> NAr), the blue light beam 61 and the red light beam 62 are focused on the corresponding first optical disk 9 and second optical disk 10, respectively. Only the first-order diffracted light is condensed on the first optical disc 9, and the + 1st-order diffracted light of the red light beam 62 has an aberration with respect to the outer peripheral portion 132 </ b> B and the objective lens 144 corresponding to the second optical disc 10. It is necessary to provide an outer peripheral portion. That is, although not shown, it is desirable that the objective lens 144 be designed differently depending on the inner and outer circumferences, similarly to the hologram 134. Thereby, the optimum NA, that is, the condition of NAb> NAr can be realized.
[0132]
12A, 12B, and 12C are cross-sectional views showing a physical shape during one period (p4) of the grating formed on the hologram 134, respectively, for a blue light beam 61 (wavelength λ1) corresponding to FIG. 12A. FIG. 13B is a diagram illustrating a phase modulation amount, and a diagram illustrating a phase modulation amount for the red light beam 62 (wavelength λ2) corresponding to FIG. 12A.
[0133]
In FIG. 12A, the physical cross-sectional shape during one period (p4) of the grating has a sawtooth cross-sectional shape. Here, in order to represent the direction of the inclined surface in the sawtooth-shaped cross-sectional shape, the cross-sectional shape in FIG. According to this designation, the cross-sectional shape of hologram 134 shown in FIG. 11B is expressed as a saw-tooth cross-sectional shape (or simply, a saw-tooth shape) in which the base material has a slope on the outer peripheral side.
[0134]
In FIG. 12A, the vertical direction indicates the depth of the grating having a sawtooth cross section. nb is the refractive index of the hologram material with respect to the blue light beam 61. If the hologram material is, for example, BK7, nb = 1.5302.
[0135]
If the depth h1 of the sawtooth grating is such that the optical path length difference with respect to the blue light beam 61 is about two wavelengths, that is, the phase difference is about 4π, h1 = 2 × λ1 / (nb−1) = 1. 53 μm.
[0136]
Since the phase modulation amount of the blue light beam 61 due to this shape changes by 4π (= 2 × 2π) in one period of the grating, the intensity of the + 2nd-order diffracted light of the blue light beam 61 becomes maximum, and the scalar calculation Is 100% diffraction efficiency.
[0137]
On the other hand, assuming that the refractive index of the hologram material with respect to the red light beam 62 is nr, when the hologram material is BK7, nr = 1.5142, so the optical path length difference generated in the red light beam 62 by the depth h1 is: h1 × (nr-1) /λ2=1.19, that is, about 1.2 times the wavelength λ2, and the amount of phase modulation is about 2.4π. Therefore, for the red light beam 62, the intensity of the + 1st-order diffracted light is the strongest, and the diffraction efficiency in scalar calculation is about 80%.
[0138]
As shown in FIG. 12A, when the shape of one grating period is a saw-tooth cross-sectional shape with a depth h1, the +2 order diffraction is the strongest for the blue light beam 61 as described above. The grating period that determines the angle is substantially p4 / 2, and the phase change is as shown in FIG. 12B. Since the + 1st-order diffraction is the strongest for the red light beam 62, the grating period that determines the diffraction angle is substantially p4.
[0139]
Using the hologram having a sawtooth-shaped cross-section having a depth that causes a difference in optical path length twice the wavelength λ1 to the blue light beam 61 and causes + 2nd-order diffraction described in the present embodiment, red light is used. The concept of realizing compatible recording / reproducing of different kinds of disks by the + 1st-order diffracted light of the beam 62 is not disclosed in any of the above-mentioned conventional examples.
[0140]
In the present embodiment, the hologram 134 has a convex lens function for both the blue light beam 61 and the red light beam 62 due to the above-described novel configuration. Since the diffractive action is such that chromatic dispersion is in the opposite direction to the refraction action, when combined with the objective lens 144, which is a refraction type convex lens, it cancels out chromatic aberration with respect to a wavelength change within several nm, particularly wavelength dependence of the focal length. There is an advantage that it can be reduced.
[0141]
Therefore, according to the present embodiment, a remarkable effect that three problems of compatibility of different kinds of disks, chromatic aberration correction, and focal position correction can be solved at once by using the hologram 134 alone is obtained.
[0142]
Further, as the overall configuration of the optical head device, it is possible to combine the configurations additionally described in the first embodiment.
[0143]
(Embodiment 5)
Next, a fifth embodiment of the present invention will be described. In the present embodiment, only the cross-sectional shape of the lattice formed on the inner peripheral portion 134C of the hologram 134 of the fourth embodiment is changed.
[0144]
13A, FIG. 13B, and FIG. 13C are cross-sectional views each showing a sawtooth shape during one period (p4) of a grating formed on the inner peripheral portion 134C of the hologram 134 according to the present embodiment, and correspond to FIG. 13A. FIG. 13B is a diagram illustrating a phase modulation amount for a blue light beam 61 (wavelength λ1), and a diagram illustrating a phase modulation amount for a red light beam 62 (wavelength λ2) corresponding to FIG. 13A.
[0145]
In FIG. 13A, the vertical direction indicates the depth of the sawtooth lattice. In the present embodiment, unlike the fourth embodiment, the depth is determined based on the red light beam 62. nr is the refractive index of the hologram material with respect to the red light beam 62. If the hologram material is, for example, BK7, nr = 1.5142.
[0146]
When the depth h2 of the sawtooth grating is set such that the optical path length difference with respect to the red light beam 62 is about 1 wavelength, that is, the phase difference is about 2π, h2 = λ2 / (nr−1) = 1.28 μm. Become.
[0147]
On the other hand, assuming that the refractive index of the hologram material with respect to the blue light beam 61 is nb, when the hologram material is BK7, nb = 1.5302, so that the optical path generated in the blue light beam 61 by the depth h2 of the sawtooth grating is provided. The length difference is h2 × (nb-1) /λ1=1.68, that is, about 1.7 times the wavelength λ1, and the amount of phase modulation is about 3.35π. Therefore, the intensity of the + 2nd-order diffracted light with respect to the blue light beam 61 becomes maximum, and the scalar calculation results in a diffraction efficiency of about 80%.
[0148]
As shown in FIG. 13A, when the shape of one period of the grating is a saw-tooth cross-sectional shape with a depth h2, the +2 order diffraction is the strongest for the blue light beam 61 as described above. The grating period that determines the angle is substantially p4 / 2, and the phase change is as shown in FIG. 13B. Since the amount of phase modulation per shape period p4 shown in FIG. 13A is about 3.35π, as shown in FIG. 13B, considering the substantial optical path length difference per one period p4 / 2, 0. 83 times, the phase modulation amount is about 1.7π. Then, for the red light beam 62, the intensity of the + 1st-order diffracted light becomes maximum, the diffraction efficiency becomes 100% in scalar calculation, and the light use efficiency can be increased.
[0149]
Further, the diffraction efficiency of the + 2nd-order diffracted light of the blue light beam 61 is reduced to about 80%, but when the center is lowered, the light amount in the outer peripheral portion is relatively increased. The far-field image of a semiconductor laser light source has a lower intensity at the outer periphery, and only a part of the far-field image can be used. However, if the light amount at the inner periphery decreases, a wider range of the far-field image can be used. Efficiency can be improved. This can be realized by shortening the focal length of the collimator lens 8, but this can compensate for the decrease in the amount of light in the inner peripheral portion.
[0150]
Therefore, according to the present embodiment, as described with reference to FIG. 13A, by making the inner peripheral portion of the hologram 134 a saw-tooth grating having a depth h2, the intensity of the diffracted light of the red light beam 62 is maximized. At this time, the light use efficiency of the blue light beam 61 with respect to the focused spot does not decrease.
[0151]
Also in the present embodiment, the hologram 134 has a convex lens function for both the blue light beam 61 and the red light beam 62. Since the diffractive action is such that chromatic dispersion is in the opposite direction to the refraction action, when combined with the objective lens 144, which is a refraction type convex lens, it cancels out chromatic aberration with respect to a wavelength change within several nm, particularly wavelength dependence of the focal length. There is an advantage that it can be reduced.
[0152]
Therefore, according to the present embodiment, a remarkable effect that three problems of compatibility of different kinds of disks, chromatic aberration correction, and focal position correction can be solved at once by using the hologram 134 alone is obtained.
[0153]
Although a lens with a high NA is difficult to manufacture, there is an advantage that the difficulty in manufacturing the refraction type objective lens 144 to be combined can be eased by the hologram 134 acting as a convex lens.
[0154]
Further, as the overall configuration of the optical head device, it is possible to combine the configurations additionally described in the first embodiment.
[0155]
(Embodiment 6)
Next, a sixth embodiment of the present invention will be described. The overall configuration of the optical head device according to the present embodiment is the same as the configuration shown in FIG. 1 referred to in the description of the first embodiment. In the present embodiment, the configuration of hologram 13 shown in FIG. 1 is different from Embodiments 1 to 5.
[0156]
FIG. 14 is a cross-sectional view showing a specific example of the composite objective lens including the hologram 13 and the objective lens 14 shown in FIG. FIG. 15A is a plan view showing the structure of the hologram 135, and FIG. 15B is a sectional view similar to FIG.
In FIGS. 14, 15A and 15B, 135 is a hologram. In FIG. 15A, an inner peripheral portion 135C of hologram 135 has the same structure as inner peripheral portion 134C of hologram 134 according to the fourth or fifth embodiment, for example. Here, the inner peripheral portion 135C of the hologram 135 may have any of the configurations shown in the first to fifth embodiments, but if it has the same structure as the inner peripheral portion 134C of the hologram 134, it has a sawtooth shape. Has the advantage of being easier to fabricate.
[0157]
16A, 16B, and 16C are cross-sectional views each showing a physical sawtooth shape for one period (p7) of a grating formed on the outer peripheral portion 135B of the hologram 135 according to the present embodiment. FIG. 16B is a diagram illustrating a phase modulation amount for the corresponding blue light beam 61 (wavelength λ1), and a diagram illustrating the phase modulation amount for the red light beam 62 (wavelength λ2) corresponding to FIG. 16A.
[0158]
In FIG. 16A, the vertical direction indicates the depth of the sawtooth shape. nb is the refractive index of the hologram material with respect to the blue light beam 61. If the hologram material is, for example, BK7, nb = 1.5302.
[0159]
Assuming that the depth h3 of the sawtooth shape is such that the optical path length difference with respect to the blue light beam 61 is about one wavelength (FIG. 16B), that is, the phase difference is about 2π, h3 = λ1 / (nb−1) = 0. 0.764 μm.
[0160]
On the other hand, assuming that the refractive index of the hologram material with respect to the red light beam 62 is nr, when the hologram material is BK7, nr = 1.5142, so the optical path length difference generated in the red light beam 62 by the depth h3 is: As shown in FIG. 16C, h3 × (nr−1) /λ2=0.593, that is, about 0.6 times the wavelength λ2, and the phase modulation amount is about 1.2π. Therefore, for the red light beam 62, the intensity of the + 1st-order diffracted light is the strongest and is about 60%.
[0161]
In this manner, as shown in FIG. 16A, when the shape of one period of the grating is formed in a saw-tooth cross-sectional shape with a depth h3, the + 1st-order diffracted light is the strongest with respect to the blue light beam 61 (the fourth embodiment and the like). In FIG. 5, the + 2nd-order diffracted light is the strongest even in the outer peripheral portion, but this embodiment is different in this respect.) Therefore, the grating period that determines the diffraction angle is substantially p7, and the phase change is as shown in FIG. 16B. The + 1st-order diffracted light is also the strongest with respect to the red light beam 62, and the grating period that determines the diffraction angle is also substantially p7.
[0162]
The outer peripheral portion 135B of the hologram 135 is designed such that the blue light beam 61 is focused through a substrate having a thickness of about 0.1 mm. At this time, the red light beam 62 also undergoes + 1st-order diffraction, which is the same diffraction order as the blue light beam 61, and the diffraction angle increases because the wavelength λ2 of the red light beam 62 is longer than the wavelength λ1 of the blue light beam.
[0163]
The blazing direction of the outer peripheral portion 135B of the hologram 135 is designed to have a convex lens action, similarly to the inner peripheral portion 135C. At this time, since the diffraction angle of the red light beam 62 is larger than that of the blue light beam 61, the red light beam 62 receives a strong convex lens action at the outer peripheral portion 135 </ b> B of the hologram 135. This is because, for example, the red light beam 62 receives a weaker convex lens action than the blue light beam 61 at the inner peripheral portion 134C of the hologram 134 according to the fourth or fifth embodiment, or the hologram 131 according to the first embodiment, for example. Is completely different from receiving a concave lens action at the inner peripheral portion 131C. For this reason, the red light beam 62 diffracted by the outer peripheral portion 135B is not focused on the same place as the red light beam 62 passing through the inner peripheral portion 135C.
[0164]
In this way, the numerical aperture NAb when recording / reproducing the first optical disc 9 with the blue light beam 61 is larger than the numerical aperture NAr when recording / reproducing the second optical disc 10 with the red light beam 62 (NAb). > NAr).
[0165]
Further, as the overall configuration of the optical head device, it is possible to combine the configurations additionally described in the first embodiment.
[0166]
(Embodiment 7)
Next, a seventh embodiment of the present invention will be described. The overall configuration of the optical head device according to the present embodiment is the same as the configuration shown in FIG. 1 referred to in the description of the first embodiment. In the present embodiment, the configuration of hologram 13 shown in FIG. 1 is different from Embodiments 1 to 6.
[0167]
In the present embodiment, as an intermediate form between Embodiment 4 and Embodiment 5 described above, the depth h4 of the sawtooth-shaped grating in the inner peripheral portion of the hologram is set to h2 <h4 <h1. is there.
[0168]
FIG. 17 is a graph showing the relationship between the depth h4 of the sawtooth grating formed on the inner peripheral portion 136C of the hologram 136 and the diffraction efficiency in the present embodiment. In FIG. 17, the horizontal axis indicates how many times the optical path length difference of the blue light beam 61 determined by the depth h4 of the sawtooth grating becomes larger than the wavelength λ1. The vertical axis is the calculated value of the diffraction efficiency.
[0169]
Making the depth h4 of the saw-toothed grating h2 <h4 <h1 means that the horizontal axis (optical path length difference / λ1) is selected to be a value larger than 1.7 and smaller than 2. means. In particular, the (optical path length difference / λ1) is set so that the diffraction efficiency of the + 1st-order diffracted light of the red light beam 62 (shown by a broken line) and the diffraction efficiency of the + 2nd-order diffracted light of the blue light beam 61 (shown by a solid line) are substantially equal. To 1.88 (about 1.9). That is, the depth h4 of the sawtooth lattice is
h4 × (nb-1) /λ1=1.88
Is chosen to satisfy By doing so, it is calculated that a diffraction efficiency of about 95% can be obtained for the + 1st-order diffracted light of the red light beam 62 and for the + 2nd-order diffracted light of the blue light beam 61. be able to.
[0170]
H4 that satisfies the above conditions has λ1 of 405 nm, and is about 1.44 μm when the hologram material is BK7.
[0171]
(Embodiment 8)
Next, an eighth embodiment of the present invention will be described. The overall configuration of the optical head device according to the present embodiment is almost the same as the configuration shown in FIG. 1 referred to in the description of the first embodiment. In the present embodiment, the configuration of the compound objective lens including the hologram 13 and the objective lens 14 shown in FIG. 1 is different from the first to seventh embodiments.
[0172]
FIG. 18 is a cross-sectional view illustrating a specific example of the objective lens according to the present embodiment. In FIG. 18, the refraction type objective lens 147 in the present embodiment is configured as a doublet lens of a first lens 1471 and a second lens 1472. Since the doublet lens naturally has four refraction surfaces, the degree of freedom in design is high, and for example, aberrations generated when the objective lens 147 is inclined with respect to the blue light beam 61 and off-axis aberrations can be reduced. For example, the aberration characteristics of the objective lens can be improved. In particular, by making the refraction surface outside the first lens 1471 (away from the second lens 1472) aspheric, off-axis aberrations can be reduced.
[0173]
Further, as described in the first embodiment, forming the hologram 137 on the surface of the objective lens 147 has an advantage that the number of components can be reduced. By forming it on the light spot or on the surface farthest from the second lens 1472), the aberration generated when the objective lens 147 is inclined with respect to both the red light beam 62 and the blue light beam 61 can be reduced. There is an advantage. Note that, as hologram 137, any of the hologram configurations of Embodiments 5 to 7 is used.
[0174]
Although the sixth conventional example described above is apparently similar to the configuration of the present embodiment, it is disclosed that the refracting surface outside the first lens 1471 (on the side away from the second lens 1472) is made aspheric. In that sufficient aberration characteristics cannot be obtained. Further, the sixth conventional example is different from the present embodiment in that the red light beam is made to be a strong divergent light and is incident on the hologram and the objective lens. A servo signal cannot be detected using a photodetector.
[0175]
(Embodiment 9)
FIG. 19 is a schematic configuration diagram of an optical information device according to Embodiment 9 of the present invention. The optical information device 67 according to the present embodiment uses the optical head device according to any of the first to eighth embodiments.
[0176]
In FIG. 19, a first optical disk 9 (or a second optical disk 10, the same applies hereinafter) is placed on a turntable 82 and rotated by a motor 64. The optical head device 55 is roughly moved by the drive device 51 of the optical head device up to a track on the first optical disc 9 where desired information exists.
[0177]
The optical head device 55 sends a focus error (focus error) signal and a tracking error signal to the electric circuit 53 in accordance with the positional relationship with the first optical disc 9. The electric circuit 53 receives this signal and sends a signal for finely moving the objective lens to the optical head device 55. With this signal, the optical head device 55 reads, writes (records), or erases information while performing focus control and tracking control on the first optical disc 9.
[0178]
Since the optical information device 67 uses any one of the first to eighth embodiments as the optical head device, a single optical head device can support a plurality of optical disks having different recording densities.
[0179]
(Embodiment 10)
FIG. 20 is a schematic diagram showing a configuration example of a computer according to the tenth embodiment of the present invention. The computer 100 according to the present embodiment incorporates the optical information device 67 according to the ninth embodiment.
[0180]
In FIG. 20, a computer 100 includes an optical information device 67, an input device 101 such as a keyboard or a mouse or a touch panel for inputting information, information input from the input device 101, and information read from the optical information device 67. Processing device 102 such as a central processing unit (CPU) that performs a calculation based on the obtained information and the like, and an output device such as a CRT display device, a liquid crystal display device, and a printer that displays information such as a result calculated by the calculation device 102 103. FIG. 18 illustrates a case where a keyboard is used as the input device 101 and a CRT display device is used as the output device 103.
[0181]
(Embodiment 11)
FIG. 21 is a schematic diagram showing a configuration example of an optical disc player according to Embodiment 11 of the present invention. Note that the optical disc player 110 according to the present embodiment incorporates the optical information device 67 according to the ninth embodiment.
[0182]
21, the optical disc player 110 includes an optical information device 67, a decoder 111 for converting an information signal obtained from the optical information device 67 into an image signal, and a liquid crystal monitor 112. In the present embodiment, the portable optical disk player 110 in which the liquid crystal monitor 112 as a display device is integrated has been illustrated and described, but a configuration in which the display device is a separate device is also possible.
[0183]
(Embodiment 12)
FIG. 22 is a schematic configuration diagram of an automobile equipped with a car navigation system according to Embodiment 12 of the present invention. In FIG. 22, the car navigation system includes a GPS (Global Positioning System) 161, an optical disc player 110 according to the eleventh embodiment, and a display device 163 for displaying a video signal from the optical disc player 110. Here, the optical disc player 110 is not limited to a specific application as long as it can reproduce information such as a video, a game, and a map from the optical disc.
[0184]
A car equipped with such a car navigation system can reproduce a large amount of video and the like using a blue light beam, can handle a wide range of detailed map data, and can also record information recorded on an existing DVD. The convenience of being able to use it can be enjoyed.
[0185]
In this embodiment, a vehicle is described as an example of a vehicle. However, it is needless to say that the present invention is not limited to a vehicle but can be applied to other vehicles such as a train, an airplane, and a ship.
[0186]
(Embodiment 13)
FIG. 23 is a schematic diagram showing a configuration example of an optical disc recorder according to Embodiment 13 of the present invention. The optical disc recorder 120 according to the present embodiment incorporates the optical information device 67 according to the ninth embodiment.
[0187]
In FIG. 23, an optical disk recorder 120 includes an optical information device 67, an encoder 121 that converts an image signal into an information signal to be recorded on an optical disk, and a decoder 111 that converts an information signal obtained from the optical information device 67 into an image signal. The output device 103 such as a CRT display device is connected to the optical disk recorder 120. Thereby, while the input image signal is converted into an information signal by the encoder 121 and recorded on the optical disk, the information signal already recorded on the optical disk is reproduced and converted into an image signal by the decoder 111, and the output device 103 It can be displayed on a certain CRT display device.
[0188]
(Embodiment 14)
FIG. 24 is a schematic diagram showing a configuration example of the optical disc server according to Embodiment 14 of the present invention. The optical disc server 150 according to the present embodiment incorporates the optical information device 67 according to the ninth embodiment.
[0189]
In FIG. 24, an optical disc server 150 is provided with an optical information device 67 and a wired or wireless input / output device that fetches an information signal to be recorded on the optical information device 67 from the outside or outputs an information signal read from the optical information device 67 to the outside. It comprises a terminal 151 and a changer 152 for taking a plurality of optical disks into and out of the optical information device 67. Further, a keyboard is connected as the input device 101 and a CRT display device is connected as the output device 103 to the optical disk server 150.
[0190]
Thus, the optical disc server 150 can exchange information with the network 153, that is, a plurality of devices, for example, a computer, a telephone, a television tuner, and the like, and use the information as a shared information server for the plurality of devices. Further, by incorporating the changer 152, a large amount of information can be recorded and accumulated.
[0191]
【The invention's effect】
As described above, according to the present invention, an optical disk capable of recording / reproducing with a red light beam having a substrate thickness of 0.6 mm and a wavelength of λ2 (typically about 660 nm) is provided. It is possible to provide a compound objective lens having high light use efficiency, which realizes compatible reproduction and compatible recording with an optical disk compatible with recording and reproduction using a blue light beam of λ1 (typically about 405 nm).
[0192]
In addition, by using such a compound objective lens for an optical head device and mounting the optical head device on an optical information device, a single optical head device can handle a plurality of optical discs having different recording densities. Become.
[0193]
Furthermore, by incorporating the above optical information device into a computer, an optical disk player, an optical disk recorder, an optical disk server, and a car navigation system, it is possible to record or reproduce information stably on different types of optical disks. It can be used.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing one configuration example of an optical head device according to a first embodiment of the present invention.
FIG. 2 is a sectional view showing a specific example of a composite objective lens including the hologram 13 and the objective lens 14 in FIG.
FIG. 3A is a plan view showing the structure of the hologram 131 of FIG. 2;
FIG. 3B is a sectional view showing the structure of the hologram 131 of FIG. 2;
FIG. 4A is a cross-sectional view showing a staircase shape for one period (p1) of a grating formed on an inner peripheral portion 131C of the hologram 131 shown in FIG. 3A.
4B is a diagram showing a phase modulation amount for a red light beam 62 (wavelength λ2) corresponding to FIG. 4A.
5 is a cross-sectional view showing a specific example of a compound objective lens including the hologram 13 and the objective lens 14 shown in FIG. 1 according to the second embodiment of the present invention.
FIG. 6A is a plan view showing the structure of a hologram 132 in FIG. 5;
6B is a sectional view showing the structure of the hologram 132 in FIG. 5;
FIG. 7A is a sectional view showing a stepped shape during one period (p2) of a grating formed on a hologram 132;
7B is a diagram showing a phase modulation amount for the blue light beam 61 (wavelength λ1) corresponding to FIG. 7A.
7C is a diagram showing a phase modulation amount for the red light beam 62 (wavelength λ2) corresponding to FIG. 7A.
FIG. 8A is a plan view showing a specific example of the hologram 13 shown in FIG. 1 according to Embodiment 3 of the present invention.
FIG. 8B is a sectional view showing a specific example of the hologram 13 shown in FIG. 1 according to the third embodiment of the present invention.
FIG. 9A is a cross-sectional view showing a staircase shape for one period (p3) of a grating formed on an outer peripheral portion 133C of a hologram 133;
9B is a diagram showing the amount of phase modulation for the blue light beam 61 (wavelength λ1) corresponding to FIG. 9A.
9C is a diagram showing the amount of phase modulation for the red light beam 62 (wavelength λ2) corresponding to FIG. 9A.
FIG. 10 is a sectional view showing a specific example of a compound objective lens including the hologram 13 and the objective lens 14 shown in FIG. 1 according to the fourth embodiment of the present invention.
11A is a plan view showing the structure of the hologram 134 in FIG. 10;
11B is a sectional view showing the structure of the hologram 134 in FIG. 10;
FIG. 12A is a sectional view showing a sawtooth shape during one period (p4) of a grating formed on a hologram 134;
FIG. 12B is a diagram showing the amount of phase modulation for the blue light beam 61 (wavelength λ1) corresponding to FIG. 12A.
12C is a diagram showing a phase modulation amount for the red light beam 62 (wavelength λ2) corresponding to FIG. 12A.
FIG. 13A is a cross-sectional view showing a sawtooth shape for one period (p4) of a grating formed on the inner peripheral portion 134C of the hologram 134 according to Embodiment 4 of the present invention.
13B is a diagram showing a phase modulation amount for the blue light beam 61 (wavelength λ1) corresponding to FIG. 13A.
13C is a diagram showing a phase modulation amount for the red light beam 62 (wavelength λ2) corresponding to FIG. 13A.
FIG. 14 is a sectional view showing a specific example of a compound objective lens including the hologram 13 and the objective lens 14 shown in FIG. 1 according to the fifth embodiment of the present invention.
FIG. 15A is a plan view showing the structure of the hologram 135 in FIG. 14;
15B is a sectional view showing the structure of the hologram 135 in FIG.
16A is a cross-sectional view showing a physical sawtooth shape for one period (p7) of a grating formed on an outer peripheral portion 135B of a hologram 135. FIG.
16B is a diagram showing a phase modulation amount for the blue light beam 61 (wavelength λ1) corresponding to FIG. 16A.
16C is a diagram showing a phase modulation amount for the red light beam 62 (wavelength λ2) corresponding to FIG. 16A.
FIG. 17 is a graph showing the relationship between the depth h4 of the sawtooth grating formed on the inner peripheral portion 136C of the hologram 136 and the diffraction efficiency according to the seventh embodiment of the present invention.
FIG. 18 is a sectional view showing a specific example of a compound objective lens according to Embodiment 8 of the present invention.
FIG. 19 is a schematic configuration diagram of an optical information device according to a ninth embodiment of the present invention.
FIG. 20 is a schematic diagram showing a configuration example of a computer according to a tenth embodiment of the present invention.
FIG. 21 is a schematic diagram showing a configuration example of an optical disc player according to Embodiment 11 of the present invention;
FIG. 22 is a schematic diagram showing a configuration example of a car navigation system according to a twelfth embodiment of the present invention.
FIG. 23 is a schematic diagram showing a configuration example of an optical disc recorder according to Embodiment 13 of the present invention;
FIG. 24 is a schematic diagram showing a configuration example of an optical disk server according to Embodiment 14 of the present invention;
FIG. 25A is a cross-sectional view showing a schematic configuration of an optical head device that condenses zero-order diffracted light 42 on an optical disk 10 having a substrate thickness of 0.6 mm in the first conventional example.
FIG. 25B is a cross-sectional view showing a schematic configuration of an optical head device that focuses the + 1st-order diffracted light 43 on the optical disc 11 having a base material thickness of 1.2 mm in the first conventional example.
FIG. 26 is a sectional view showing a schematic configuration of an optical head device as a second conventional example.
27A is a plan view showing the structure of the wavelength selection phase plate 205 of FIG. 26.
FIG. 27B is a sectional view showing the structure of the wavelength selection phase plate 205 of FIG. 26;
FIG. 28 is a sectional view showing a schematic configuration of an optical head device as a sixth conventional example.
[Explanation of symbols]
1 Blue laser light source
2 Beam shaping element
3,22 3-beam grating
4, 16 beam splitter
5 1/4 wavelength plate
6 Condensing lens
7 Photodetector
8 Collimating lens
9 First optical disk
10 Second optical disk
13, 131, 132, 133, 134, 135, 136, 137 Hologram
14, 141, 142, 143, 144, 145, 147 Objective lens
1471 First objective lens
1472 Second objective lens
15 Driving means
20 Red laser light source
32 detection lens
33 Photodetector
51 Driving device for optical head device
53 electric circuit
55 Optical Head Device
61 blue light beam (first light beam)
62 red light beam (second light beam)
64 motor
67 Optical Information Equipment
100 computer
101 Input device
102 arithmetic unit
103 Output device
110 Optical Disc Player
111 decoder
112 LCD monitor
120 Optical Disk Recorder
121 encoder
150 Optical Disk Server
151 I / O terminal
152 changer
153 Network
161 GPS
163 Display device

Claims (32)

A composite objective lens comprising a hologram and a refraction lens, wherein the hologram includes a grating having a step-shaped cross-sectional shape formed in at least a partial region, and the step having the step-shaped cross-sectional shape is an integer of a unit step d1. The unit step d1 is a step that gives an optical path difference of about one wavelength to the first light beam having the wavelength λ1 in the range of 390 nm to 415 nm, and one period of the grating is the hologram. A composite objective lens comprising stairs having heights in the order of 0, 2, 1 and 3 times the unit step d1 from the outer peripheral side toward the optical axis side. The ratio of the width of the steps of the stepped cross-sectional shape of the lattice is 2: 3: 3: 2, corresponding to the order of 0 times, 2 times, 1 time, and 3 times the unit steps d1. The compound objective lens according to claim 1, wherein: The compound objective lens according to claim 1, wherein the grating is formed only on an inner peripheral portion of the hologram. The compound objective lens condenses the 0th-order diffracted light of the first light beam through a substrate having a thickness of t1, and converts the first-order diffracted light of the second light beam having a wavelength λ2 in the range of 630 nm to 680 nm into: The compound objective lens according to claim 1, wherein the light is condensed through a substrate having a thickness (t2) greater than the thickness (t1). A composite objective lens comprising a hologram and a refraction lens, wherein the hologram includes a grating having a step-shaped cross section formed at least on an inner peripheral portion, and a step having the step-shaped cross section is an integral multiple of a unit step d2. Wherein the unit step d2 is a step that gives an optical path difference of about 1.25 wavelength to the first light beam having the wavelength λ1 in the range of 390 nm to 415 nm, and one period of the grating is A composite objective lens comprising stairs having heights of 0, 1, 2, 3 times the unit step d2 from the outer peripheral side of the hologram to the optical axis side. The ratio of the width of the steps of the stepped cross-sectional shape of the lattice is 1: 1: 1: 1, corresponding to the order of 0 times, 1 time, 2 times, and 3 times the unit steps d2, respectively. 6. The compound objective lens according to claim 5, wherein: The hologram includes a grating having a step-shaped cross-sectional shape formed on an outer peripheral portion, and a step of the step-shaped cross-sectional shape of the lattice formed on the outer peripheral portion is an integral multiple of a unit step d3, and the unit step d3 Is a step that gives an optical path difference of about 0.25 wavelength to the first light beam, and one period of the grating formed on the outer peripheral portion is such that the period from the outer peripheral side of the hologram toward the optical axis side is 6. The compound objective lens according to claim 5, comprising a step having a height of 0, 1, 2, 3 times the unit step d3. The compound objective lens focuses the + 1st-order diffracted light of the first light beam through a base material having a thickness of t1, and has a wavelength λ2 in a range of 630 nm to 680 nm, and is formed on an inner peripheral portion of the hologram. 6. The compound objective lens according to claim 5, wherein the -1st-order diffracted light of the second light beam passing through the grating is converged through a substrate having a thickness t2 greater than the thickness t1. A composite objective lens comprising a hologram and a refraction lens, wherein the hologram includes a grating having a sawtooth cross-sectional shape formed at least on an inner peripheral portion, and a depth h1 of the sawtooth cross-sectional shape is 390 nm to 415 nm. The depth is such that an optical path difference of about 2 wavelengths is given to the first light beam having the wavelength λ1 which is within the range described above, and the + 2nd order diffracted light is generated most strongly, and has the wavelength λ2 which is within the range of 630 nm to 680 nm. A composite objective lens having a depth at which + 1st-order diffracted light is generated most strongly with respect to the second light beam. A composite objective lens comprising a hologram and a refractive lens,
The hologram includes a grating having a sawtooth cross-sectional shape formed at least on an inner peripheral portion thereof, and a depth h2 of the sawtooth cross-sectional shape is a second light beam having a wavelength λ2 in a range of 630 nm to 680 nm. This is a depth at which an optical path difference of about one wavelength is given to generate the + 1st-order diffracted light most strongly, and the + 2nd-order diffracted light is generated most strongly for the first light beam having the wavelength λ1 in the range of 390 nm to 415 nm. A composite objective lens having a depth to be applied. A composite objective lens comprising a hologram and a refractive lens,
The hologram includes a grating having a sawtooth cross-sectional shape formed at least on an inner peripheral portion, and a depth h4 of the sawtooth cross-sectional shape is equal to a first light beam having a wavelength λ1 in a range of 390 nm to 415 nm. On the other hand, it is a depth at which an optical path difference larger than 1.7 wavelengths and smaller than 2 wavelengths is given to generate the + 2nd-order diffracted light most strongly, and +1 for the second light beam having the wavelength λ2 within the range of 630 nm to 680 nm. A compound objective lens having a depth at which the next-order diffracted light is generated most strongly. The compound objective lens according to claim 11, wherein the depth h4 of the sawtooth cross-sectional shape is a depth that gives an optical path difference of 1.9 wavelength to the first light beam. A composite objective lens comprising a hologram and a refractive lens,
The hologram generates the + 2nd-order diffracted light most strongly for the first light beam having the wavelength λ1 in the range of 390 nm to 415 nm, and generates the second light beam having the wavelength λ2 in the range of 630 nm to 680 nm. On the other hand, the + 1st order diffracted light is generated most strongly,
The refraction type lens condenses + 2nd-order diffracted light of the first light beam through the hologram through a base material having a thickness of t1, and + 1st time of the second light beam through the inner periphery of the hologram. A compound objective lens for condensing folded light through a substrate having a thickness t2 greater than the thickness t1. The hologram includes a grating having a sawtooth cross-sectional shape formed on an outer peripheral portion, and a depth h3 of the sawtooth cross-sectional shape of the grating formed on the outer peripheral portion is about one wavelength with respect to the first light beam. 11. The depth at which the + 1st-order diffracted light is generated most strongly by giving the optical path difference of, and the depth at which the + 1st-order diffracted light is also generated most strongly for the second light beam. 14. The composite objective according to any one of claims 11, 11 and 13. The hologram is configured to act as a convex lens to reduce a change in focal length for a change in the wavelength λ1 when the first light beam is focused through a substrate having a thickness of t1. A composite objective according to any one of claims 5, 9, 10, 11, and 13, characterized in that: The hologram is configured such that, when the first light beam is focused through a base material having a thickness of t1, the second light beam passing through an inner peripheral portion of the hologram is used to separate a focus position on the optical disk side from the compound objective lens. The second light beam passing through the inner periphery of the hologram is collected through the base material having the thickness t2 so that the function as a convex lens is greater than when the light beam is collected through the base material having the thickness t2. 10. The device according to claim 4, wherein when the light is emitted, the function as a convex lens is smaller than when the first light beam is condensed through a substrate having a thickness of t1. 14. The compound objective lens according to any one of 10, 11, and 13. 14. The cross-sectional shape of the grating forming the hologram is a saw-tooth shape in which a base material forming the hologram has a slope on the outer peripheral side. Compound objective lens. The composite objective lens according to any one of claims 1, 5, 9, 10, 11, and 13, wherein the hologram and the refractive lens are integrally fixed. The compound objective lens according to any one of claims 1, 5, 9, 10, 11, and 13, wherein the refraction lens has a non-spherical refraction surface opposite to a condensing spot. The compound objective lens according to claim 19, wherein the hologram is formed integrally with the aspheric surface of the refractive lens. 14. The compound objective lens according to claim 1, wherein the hologram is integrally formed on a surface of the refractive lens. When the numerical aperture at which the first light beam is condensed through the base material having the thickness t1 is NAb, and the numerical aperture at which the second light beam is condensed through the base material having the thickness t2 is NAr, NAb> NAr. The compound objective lens according to any one of claims 4, 8, and 14, wherein: A first laser light source that emits a first light beam having a wavelength λ1 in a range of 390 nm to 415 nm;
A second laser light source that emits a second light beam having a wavelength λ2 in the range of 630 nm to 680 nm;
A first light beam emitted from the first laser light source is received and condensed on a recording surface of a first optical disk through a base material having a thickness of t1, and a second light beam emitted from the second laser light source is emitted. The light receiving device according to any one of claims 1, 5, 9, 10, 11, and 13, wherein the light is condensed on a recording surface of a second optical disc through a base material having a thickness t2 greater than the thickness t1. A compound objective lens,
And a photodetector that receives the first and second light beams respectively reflected on the recording surfaces of the first and second optical discs and outputs an electric signal according to the amount of light. Optical head device. The optical head device includes a collimating lens that collimates the first and second light beams emitted from the first and second laser light sources, respectively.
When condensing the second light beam on the recording surface of the second optical disc, the collimating lens is brought closer to the second laser light source side to convert the second light beam to a diffused light and the composite objective lens 24. The optical head device according to claim 23, wherein a focal position on the side of the second optical disk is separated from the compound objective lens by making the light incident on the composite objective lens. The first and second laser light sources are arranged such that both light emission points thereof are in an image-forming relationship with respect to the focal positions of the compound objective lens on the first and second optical disk sides, and the light detector Is provided in common with the first and second light beams respectively reflected on the recording surfaces of the first and second optical disks, and detects the servo signal in response to the first and second light beams. 25. The optical head device according to claim 23, wherein: A first laser light source that emits a first light beam having a wavelength λ1 in a range of 390 nm to 415 nm, a second laser light source that emits a second light beam having a wavelength λ2 in a range of 630 nm to 680 nm, A first light beam emitted from the first laser light source is received and condensed on a recording surface of a first optical disc through a base material having a thickness of t1, and a second light beam emitted from the second laser light source is emitted. The light receiving device according to any one of claims 1, 5, 9, 10, 11, and 13, wherein the light is condensed on a recording surface of a second optical disc through a base material having a thickness t2 greater than the thickness t1. A compound objective lens; and a photodetector that receives the first and second light beams respectively reflected on the recording surfaces of the first and second optical discs and outputs an electric signal corresponding to the light amount. Light Storage device,
A motor for rotating the first and second optical disks;
Optical information, comprising: a signal obtained from the optical head device; and an electric circuit for driving and controlling the motor, the compound objective lens, and the first and second laser light sources based on the signal. apparatus. The optical head device includes a collimating lens that collimates the first and second light beams emitted from the first and second laser light sources, respectively, and the optical information device has a thickness t2 of a base material. 27. The optical information apparatus according to claim 26, wherein when the second optical disc having a height of 0.6 mm is loaded, the collimating lens is controlled to move toward the second laser light source. An optical information device;
Input means for inputting information;
An arithmetic unit that performs an arithmetic operation based on information input from the input unit and information reproduced from the optical information device;
A computer comprising: information input from the input means, information reproduced from the optical information device, and output means for displaying or outputting a result calculated by the arithmetic device,
The optical information device,
A first laser light source that emits a first light beam having a wavelength λ1 in a range of 390 nm to 415 nm, a second laser light source that emits a second light beam having a wavelength λ2 in a range of 630 nm to 680 nm, A first light beam emitted from the first laser light source is received and condensed on a recording surface of a first optical disc through a base material having a thickness of t1, and a second light beam emitted from the second laser light source is emitted. The light receiving device according to any one of claims 1, 5, 9, 10, 11, and 13, wherein the light is condensed on a recording surface of a second optical disc through a base material having a thickness t2 greater than the thickness t1. A compound objective lens; and a photodetector that receives the first and second light beams respectively reflected on the recording surfaces of the first and second optical discs and outputs an electric signal corresponding to the light amount. Light Storage device,
A motor for rotating the first and second optical disks;
A computer comprising: a signal that is received from the optical head device; and an electric circuit that drives and controls the motor, the compound objective lens, and the first and second laser light sources based on the signal. An optical information device;
An optical disc player comprising a decoder for converting an information signal obtained from the optical information device into an image signal,
The optical information device,
A first laser light source that emits a first light beam having a wavelength λ1 in a range of 390 nm to 415 nm, a second laser light source that emits a second light beam having a wavelength λ2 in a range of 630 nm to 680 nm, A first light beam emitted from the first laser light source is received and condensed on a recording surface of a first optical disc through a base material having a thickness of t1, and a second light beam emitted from the second laser light source is emitted. The light receiving device according to any one of claims 1, 5, 9, 10, 11, and 13, wherein the light is condensed on a recording surface of a second optical disc through a base material having a thickness t2 greater than the thickness t1. A compound objective lens; and a photodetector that receives the first and second light beams respectively reflected on the recording surfaces of the first and second optical discs and outputs an electric signal corresponding to the light amount. Light Storage device,
A motor for rotating the first and second optical disks;
An optical disc player comprising: a signal obtained from the optical head device; and an electric circuit that drives and controls the motor, the compound objective lens, and the first and second laser light sources based on the signal. . An optical information device;
A decoder for converting an information signal obtained from the optical information device into an image signal,
The optical information device,
A first laser light source that emits a first light beam having a wavelength λ1 in a range of 390 nm to 415 nm, a second laser light source that emits a second light beam having a wavelength λ2 in a range of 630 nm to 680 nm, A first light beam emitted from the first laser light source is received and condensed on a recording surface of a first optical disc through a base material having a thickness of t1, and a second light beam emitted from the second laser light source is emitted. The light receiving device according to any one of claims 1, 5, 9, 10, 11, and 13, wherein the light is condensed on a recording surface of a second optical disc through a base material having a thickness t2 greater than the thickness t1. A compound objective lens; and a photodetector that receives the first and second light beams respectively reflected on the recording surfaces of the first and second optical discs and outputs an electric signal corresponding to the light amount. Light Storage device,
A motor for rotating the first and second optical disks;
A car navigation system comprising: a motor that receives a signal obtained from the optical head device, and based on the signal, an electric circuit that drives and controls the motor, the compound objective lens, and the first and second laser light sources. system. An optical information device;
An encoder for converting an image signal into an information signal to be recorded in the optical information device, comprising:
The optical information device,
A first laser light source that emits a first light beam having a wavelength λ1 in a range of 390 nm to 415 nm, a second laser light source that emits a second light beam having a wavelength λ2 in a range of 630 nm to 680 nm, A first light beam emitted from the first laser light source is received and condensed on a recording surface of a first optical disc through a base material having a thickness of t1, and a second light beam emitted from the second laser light source is emitted. The light receiving device according to any one of claims 1, 5, 9, 10, 11, and 13, wherein the light is condensed on a recording surface of a second optical disc through a base material having a thickness t2 greater than the thickness t1. A compound objective lens; and a photodetector that receives the first and second light beams respectively reflected on the recording surfaces of the first and second optical discs and outputs an electric signal corresponding to the light amount. Light Storage device,
A motor for rotating the first and second optical disks;
An optical disc recorder comprising: a signal obtained from the optical head device; and an electric circuit for driving and controlling the motor, the compound objective lens, and the first and second laser light sources based on the signal. . An optical information device;
An optical disc server having an input / output terminal for recording an information signal input from outside in the optical information device and outputting an information signal reproduced from the optical information device to the outside,
The optical information device,
A first laser light source that emits a first light beam having a wavelength λ1 in a range of 390 nm to 415 nm, a second laser light source that emits a second light beam having a wavelength λ2 in a range of 630 nm to 680 nm, A first light beam emitted from the first laser light source is received and condensed on a recording surface of a first optical disc through a base material having a thickness of t1, and a second light beam emitted from the second laser light source is emitted. The light receiving device according to any one of claims 1, 5, 9, 10, 11, and 13, wherein the light is condensed on a recording surface of a second optical disc through a base material having a thickness t2 greater than the thickness t1. A compound objective lens; and a photodetector that receives the first and second light beams respectively reflected on the recording surfaces of the first and second optical discs and outputs an electric signal corresponding to the light amount. Light Storage device,
A motor for rotating the first and second optical disks;
An optical disc server comprising: a signal obtained from the optical head device; and an electric circuit for driving and controlling the motor, the compound objective lens, and the first and second laser light sources based on the signal. .

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