US20050083827A1 - Optical head and optical head device - Google Patents
Optical head and optical head device Download PDFInfo
- Publication number
- US20050083827A1 US20050083827A1 US10/863,341 US86334104A US2005083827A1 US 20050083827 A1 US20050083827 A1 US 20050083827A1 US 86334104 A US86334104 A US 86334104A US 2005083827 A1 US2005083827 A1 US 2005083827A1
- Authority
- US
- United States
- Prior art keywords
- light
- prism
- light beam
- optical
- emergent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Images
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1387—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector using the near-field effect
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1359—Single prisms
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1362—Mirrors
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
- G11B7/1384—Fibre optics
Definitions
- the present invention relates to an optical head and an optical head device, and more particularly to an optical head which is suited to be used for high-density recording/reading erasing of information to or from an optical recording medium and an optical head device using this optical head.
- optical memories which optically record and read information
- high-density devices which are capable of recording an extremely large volume of information are demanded, and in order to comply with the demand, a near field optical recording technique is suggested.
- a conventional optical memory using a laser beam the recording density is limited depending on the diffraction limit of light, and such an optical memory can record and read marks of sizes at least light wavelength (several hundred nanometers).
- a recently proposed optical memory which uses near field optics radiates light to a recording medium (optical disk) for recording/reading with the optical head and the recording medium arranged at an interval of only some dozen nanometers.
- the optical memory uses a fiber probe with a minuscule aperture smaller than light wavelength and a solid immersion lens.
- a convergent lens, a mirror, a prism and other optical elements are installed in the optical head, and the optical head is large and heavy. It is, therefore, difficult to adopt an air floating method based on the air lubricating principle, which is generally adopted in magnetic recording heads, in such an optical memory.
- the solid immersion lens although the solid immersion lens itself is small and light, it is necessary to further use a convergent lens, which indispensably increases the size and weight.
- An object of the present invention is to provide a small and light optical head.
- Another object of the present invention is to provide an optical head device of which optical system can be designed freely.
- Another object of the present invention is to provide an optical head device in which light has only a small loss.
- Another object of the present invention is to provide a near field optical head which is suited to make a gap from a recording medium by an air floating method.
- Another object of the present invention is to provide an optical head which is capable of correcting spherical aberration when a parallel bundle of rays is incident thereto.
- Another object of the present invention is to provide an optical head which is capable of using a divergent bundle of rays as incident light thereto.
- Another object of the present invention is to provide an optical head which is capable of recording, reading and erasing information at a higher density by reducing the diameter of a near field light beam.
- Another object of the present invention is to provide an optical head device which is strong against external vibration and shock.
- Another object of the present invention is to provide an optical head device which records, reads and erases information by use of either one selected from near field light and propagated light.
- Another object of the present invention is to provide an optical head device which uses a non-coaxial optical system.
- an optical head device comprises: a first light source which emits light; and a prism which receives the light emitted from the first light source as first incident light, reflects the first incident light inside at least once and emits the first incident light in a direction different from a direction in which the first incident light was incident thereto.
- a prism according to the present invention comprises: an incident section which receives incident light; a first surface which reflects the incident light received by the incident section in the prism; and a second surface through which the light reflected by the first surface is emergent from the prism for reading of information.
- Another prism according to the present invention comprises: an incident section which receives incident light; a first surface which reflects the incident light received by the incident section in the prism; a second surface which reflects the light reflected by the first surface in the prism in a direction which is different from a direction in which the incident light was received by the incident section; and a third surface through which the light reflected by the second surface is emergent from the prism for reading of information.
- Another prism according to the present invention uses near field light occurring on an emergent surface for recording, reading and erasing of information, and the prism comprises an internal reflective surface which reflects light which was incident to the prism inside and converges the light on a vicinity of the emergent surface.
- a non-oaxial optical system is formed.
- an optical head can be composed of only a prism. Accordingly, the optical head is small and light and has a simple optical system. Also, an air floating method can be adopted in making a gap between the optical head and a recording medium.
- FIG. 1 is a schematic structural view of an optical head device which is a first embodiment of the present invention
- FIG. 2 is an illustration which shows an occurrence of near field light in the first embodiment
- FIG. 3 is an illustration which shows travel of light in a prism
- FIG. 4 is an illustration which shows an incident light beam spot, which is a sectional view cut along “IV-IV” in FIG. 3 .
- FIG. 5 is an illustration which shows an incident light beam spot and an occurrence of near field light, which is a sectional view cut along “V-V” in FIG. 3 ;
- FIG. 6 is a schematic structural view of a modification of the first embodiment
- FIG. 7 is a schematic structural view of another modification of the first embodiment
- FIG. 8 is a schematic structural view of another modification of the first embodiment
- FIG. 9 is a schematic structural view of the main part of an optical head device which is a second embodiment of the present invention.
- FIG. 10 is a schematic structural view of an optical head device which is a third embodiment of the present invention.
- FIG. 11 is an illustration which shows travel of light in a prism in the third embodiment
- FIG. 12 is a schematic structural view of an optical head device which is a fourth embodiment of the present invention.
- FIG. 13 is an illustration which shows an occurrence of near field light in the fourth embodiment
- FIG. 14 is a schematic structural view of an optical head device which is a fifth embodiment of the present invention.
- FIG. 15 is a schematic structural view of an optical head device which is a sixth embodiment of the present invention.
- FIG. 16 is an illustration which shows of an occurrence of near field light in the sixth embodiment
- FIG. 17 is an illustration which shows travel of light in a prism in the sixth embodiment
- FIG. 18 is an illustration which shows an incident light beam spot, which is a sectional view cut along “X VIII-X VIII” in FIG. 17 ;
- FIG. 19 is an illustration which shows an incident light beam spot and an occurrence of near field light, which is a sectional view cut along “XIX-XIX” in FIG. 17 ;
- FIG. 20 is a schematic structural view of a modification of the sixth embodiment
- FIG. 21 is a schematic structural view of another modification of the sixth embodiment.
- FIG. 22 is a schematic structural view of an optical head device which is a seventh embodiment of the present invention.
- FIG. 23 is a schematic structural view of an optical head device which is an eighth embodiment of the present invention.
- FIG. 24 is an illustration which shows travel of light in a prism in the eighth embodiment.
- the number 1 denotes a recording medium
- the number 10 denotes an optical head device.
- the recording medium 1 has a recording layer 3 on a substrate 2 and can be driven to rotate on a rotary driving shaft 4 .
- a protective layer may be formed on the recording layer 3 .
- the optical head device 10 has a prism 12 serving as an optical head at the end of an arm 11 .
- a light source 15 On the arm 11 , a light source 15 , a collimator lens 16 (see FIG. 2 ), a polarizing beam splitter 17 , a ⁇ /4 wavelength plate 18 , an optical detector 19 are provided.
- the prism 12 has an incident surface 12 a , an internal reflective surface 12 b and an emergent surface 12 c .
- the incident surface 12 a and the emergent surface 12 c are plane, and the internal reflective surface 12 b is a paraboloid of revolution, of which top is an end P of the surface 12 b (see FIG. 3 ).
- This internal reflective surface 12 b is made by forming a reflective material 13 such as Au, Ag, Cu, Cr, Ni, Al or the like into a film.
- the prism 12 is made of for example, glass such as LASF, LaF, BaSF, etc.
- the prism 12 is a high-refractive medium and at least has a higher refractive index than the medium which is in contact with the emergent surface 12 c.
- the light source 15 may be a laser diode, an LED or any other light emitting source.
- the gap between the emergent surface 12 c and the recording layer 3 of the recording medium 1 is set not more than 1 ⁇ 4 of the wavelength A (60 to 100 nm), so that the near field light N irradiates the recording layer 3 and forms a recording pit 3 a thereon.
- the spot diameter s of the near field light N (see FIG. 3 ) is substantially equal to that of the light beam as if still traveling in the prism 12 and is substantially 1/n (n: refractive index of the prism 12 ) of that of the light beam when traveling in the air.
- the wavelength ⁇ of the incident light is 630 nm
- the refractive index n of the prism 12 is 1.8
- the beam diameter w of the incident light is 1 mm and if the distance d between the converging point O of the prism 12 and the end P of the prism 12 is 0.7 mm
- the spot diameter s of the near field light N is approximately 370 nm
- the recording density at this time is approximately 3.5 Gbit/inch 2 , which is extremely high.
- the internal reflective surface 12 b of the prism 12 is a paraboloid of revolution of which top is the end P of the prism 12 , this surface has a function of correcting spherical aberration of a parallel bundle of rays.
- the near field light N irradiates the recording layer 3 on the recording pit 3 a .
- the near field light N is reflected by the recording layer 3 , and the reflected light travels backward.
- the reflected light is emergent from the prism 12 through the incident surface 12 a , passes through the ⁇ /4 wavelength plate 18 again and is reflected by the beam splitter 17 . Then, the light is received by the optical detector 19 . Thereby, a reading signal of the recording pit 3 a can be obtained.
- the reflected light is securely directed to the optical detector 19 without returning to the light source 15 , whereby the reading signal can be obtained in good conditions.
- the power of the light source 15 for reading may be weaker than that for recording. Erasing is carried out in a similar process; if necessary, however, the wavelength of light may be changed.
- incident light to the prism 12 is internally reflected once and is converged on the emergent surface 12 c, which causes a near field light N to effuse therethrough to carry out recording, reading or erasing.
- the head is composed of only the prism 12 , and neither a convergent lens nor a reflective mirror is necessary. Consequently, the head is small and light and can be floated based on the air lubricating principle. Because the light is reflected in the prism 12 only once, the loss of light is small. Because the light has only a small loss in the prism 12 and because neither a convergent lens nor a reflective mirror is necessary, the freedom of the design of the optical system is large.
- the incident beam spot is preferably elliptical as indicated by “S” in FIGS. 4 and 5 .
- FIG. 4 is the section cut along the line “IV-IV” in FIG. 3
- FIG. 5 is the section cut along the line “V-V” in FIG. 3 .
- the longer axis of the beam spot S extends in the X direction, and the prism 12 has a larger numerial aperture in the X direction. Accordingly, the diameter s′ of the beam spot on the converging point O in the X direction (see FIG. 5 ) is smaller than the diameter s in the Z direction (see FIG. 3 ).
- the longer axis a and the shorter axis b of the incident beam spot S is 1.6 mm and 1 mm, respectively, and if the distance d is 0.7 mm, the spot diameter s in the Z direction is approximately 370 nm, while the spot diameter s′ in the X direction is approximately 240 nm. Accordingly, if the X direction corresponds to the circular direction (recording direction) of the recording medium 1 , the recording density is improved.
- FIG. 6 shows a modification of the first embodiment.
- light is incident to the prism 12 from slightly downward, not in parallel to the surface of the recording medium 1 .
- the incident surface 12 a of the prism 12 is slightly tilted so as to be perpendicular to the incident light.
- the numerical aperture of the prism 12 on the emergent surface 12 c becomes larger, and accordingly, the spot diameter on the converging point O becomes smaller.
- FIG. 7 shows another modification of the first embodiment.
- the collimator lens 16 shown in FIG. 2 is omitted, and a divergent bundle of rays is incident to the prism 12 .
- the incident surface 12 a of the prism 12 is convex and converges the incident divergent light into a parallel bundle of rays.
- FIG. 8 shows another modification of the first embodiment.
- a minuscule opening 14 a is made at the converging point on the emergent surface 12 c of the prism 12 .
- a light shutter film 14 is covered on the emergent surface 12 c, and at the converging point, a minuscule opening 14 a is made in the light shutter film 14 .
- the light shutter film 14 may be made of the same material of the reflective film 13 .
- the second embodiment for recording, reading and erasing, light of a wavelength ⁇ 1 , light of a wavelength of ⁇ 2 and light of a wavelength of ⁇ 3 are used, respectively.
- the second embodiment is of the same structure as the first embodiment.
- the light source 15 has light emitting sources which emit light of a wavelength ⁇ 1 , light of a wavelength of ⁇ 2 and light of a wavelength of ⁇ 3 , respectively and switches these light emitting sources for recording, reading and erasing to emit the light of the respective wavelengths toward the prism 12 .
- the recording layer 3 is preferably a photochromic medium.
- 1,2-bis (2,4,5-trimethyl-3-thienyl)-cis-1,2-dicyanoethene (trade name, made by Tokyo Chemical Industry Co., Ltd.) can be named.
- light of 355 nm is used for recording; light of 632 nm is used for reading; and light of 780 nm is used for erasing.
- Recording, reading and erasing in the second embodiment are carried out in the same processes as described in the first embodiment except that it is necessary to switch the wavelength of light.
- the third embodiment is a compatible optical head device which has a prism 22 so as to carry out recording, reading and erasing not only by a near field light but also by a propagated light beam. Accordingly, this device also can be used to record, read and erase information to and from conventional optical disk media such as CDs, DVDs, etc. by use of a propagated light beam.
- the head using a near field light is basically of the same structure as that of the first embodiment, and in FIG. 10 , the same members are denoted by the same reference symbols as in FIG. 1 .
- the prism 22 has an incident surface 22 a and an internal reflective surface 22 b on which a reflective film 23 is formed.
- a near field light N effuses through an emergent surface 22 c at a converging point O.
- the internal reflective surface 22 b is a paraboloid of revolution of which top is its end P.
- a light source 35 In order to carry out recording, reading and erasing by use of a propagated light beam, a light source 35 , a collimator lens (not shown), a polarizing beam splitter 37 , a ⁇ /4 wavelength plate 38 , an optical detector 39 and a mirror 34 are provided. Also, the prism 22 has a convex incident surface 22 a′.
- a light beam of a wavelength A 4 emitted from the light source 35 is changed into a parallel bundle of rays by the collimator lens and passes through the polarizing beam splitter 37 and the ⁇ /4 wavelength plate 38 . Thereafter, the beam is reflected by the mirror 34 and is incident to the prism 22 vertically through the incident surface 22 a ′. As FIG. 11 shows, this incident light is refracted and converged in the prism 22 and is emergent from the prism 22 through the emergent surface 22 c as a propagated light beam T.
- the emergent light beam of which spot diameter is s 1 , irradiates the recording layer of a recording medium and forms a recording pit.
- the spot diameter s 1 of the propagated light beam T is larger than the spot diameter s of the near field light N.
- the spot diameter s 1 of the propagated light beam T emergent from the prism 22 is approximately 780 nm.
- the spot diameter s of the near field light N is, under the conditions specified in the first embodiment, approximately 370 nm. Thus, the spot diameter s 1 is larger than the spot diameter s.
- the light beam T is reflected by the recording layer, and the reflected light is incident to the prism 22 and is emergent from the prism 22 through the incident surface 22 a ′.
- the light is, thereafter, reflected by the mirror 34 , deflected by the ⁇ /4 wavelength plate 38 and reflected by the polarizing beam splitter 37 . Then, the light is received by the optical detector 39 .
- the wavelength ⁇ 4 of the light emitted from the light source 35 may be equal to or different from the wavelength ⁇ of the light emitted from the light source 15 . If the wavelength ⁇ 4 is equal to the wavelength ⁇ , either the light source 35 or the light source 15 and the corresponding collimator lens can be omitted. In this case, light emitted from the remained light source is split to travel to the polarizing beam splitter 17 and to the polarizing beam splitter 37 .
- the modifications shown by FIGS. 6, 7 and 8 can be adopted.
- the wavelength of the light emitted from the light source may be changeable between ⁇ 1 , ⁇ 2 and ⁇ 3 .
- the fourth embodiment is an optical head device 40 which is a combination of a prism 42 and an optical waveguide 46 .
- the optical waveguide 46 are composed of three optical fibers 46 a , 46 b and 46 c (of a conventional type of which core is covered with cladding) which are provided on an arm 41 , and the respective one ends of the optical fibers 46 a, 46 b and 46 c are connected to an optical diverging circuit 47 .
- the other end of the optical fiber 46 a is connected to a light source 45 ; the other end of the optical fiber 46 b is connected to an incident surface 42 a of the prism 42 ; and the other end of the optical fiber 46 c is connected to an optical detector 48 .
- the optical fibers 46 a, 46 b and 46 c multi-mode fibers which have a core diameter of 50 ⁇ m, a cladding diameter of 125 ⁇ m and a numerical aperture of 0.2 are used.
- the light source 45 comprises a light emitting source, such as a laser diode, a light emitting diode or the like, a collimator lens and an objective lens. Collimated light of a specified wavelength is incident to the optical fiber 46 a.
- the prism 42 is basically of the same structure and the same materials as the prism 12 , and on an internal reflective surface 42 b, a reflective film 43 is formed (see FIG. 13 ).
- light of a wavelength ⁇ emitted from the light source 45 is incident to the optical fiber 46 a and further incident to the prism 42 via the optical diverging circuit 47 and the optical fiber 46 b.
- the incident light is reflected by the reflective surface 42 b once and converged on an emergent surface 42 c of the prism 42 .
- the light effuses through the emergent surface 42 c as a near field light N.
- the gap between the emergent surface 42 c and the recording layer 3 of the recording medium 1 is set not more than 1 ⁇ 4 of the wavelength ⁇ (50 to 100 nm), and the near filed light N irradiates the recording layer 3 and forms a recording pit 3 a.
- the internal reflective surface 42 b of the prism 42 is an ellipsoid of revolution which has two focal points on the beam waist W of the light beam emitted from the optical fiber 46 b and on the converging point O.
- the light beam emergent from the optical fiber 46 b is a divergent bundle of rays
- the reflective surface 42 b which is an ellipsoid of revolution has a function of correcting spherical aberration of a divergent bundle of rays.
- the near field light N is reflected on the recording layer 3 and travels backward in the prism 42 . Then, the reflected light is converged on the end surface of the optical fiber 46 b. This reflected light travels to the optical diverging circuit 47 through the optical fiber 46 b and is directed to the optical detector 48 by the optical fiber 46 c. Thereby, a reading signal of the recording pit 3 a is obtained
- the power of the light source 45 for reading may be weaker than the power for recording. Erasing is carried out in a similar process; the wavelength of light, however, may be required to be changed.
- the fourth embodiment brings the same effects as the first embodiment. Moreover, because the prism 42 is connected to the optical waveguide 46 , the optical head device 40 is stable against vibration of the arm 41 due to vibration of the recording medium 1 and external vibration and shock, and the optical axis does not shift, which secures stable recording/reading performance.
- a minuscule opening may be made on the converging point O of the emergent surface 42 c as FIG. 8 shows.
- the optical waveguide a thin film waveguide of a ZnO layer can be used as well as optical fibers.
- the fifth embodiment is a compatible optical head device like the third embodiment and uses an optical waveguide.
- the fifth embodiment has a prism 52 which is of the same structure as the prism 22 shown by FIG. 11 .
- the prism 52 has incident surfaces 52 a, 52 a ′, an internal reflective surface 52 b and an emergent surface 52 c.
- the optical system for a near field light is of the same structure as the fourth embodiment, and recording and reading are carried out in the same processes as described in the fourth embodiment.
- the optical system for a propagated light beam is basically of the same structure of the optical system for a near field light.
- the optical system for a propagated light beam comprises a light source 55 , an optical waveguide 56 composed of optical fibers 56 a, 56 b and 56 c, an optical diverging circuit 57 and an optical detector 58 .
- Light emitted from the light source 55 travels through the optical fiber 56 a, the optical diverging circuit 57 and the optical fiber 56 b and is incident to the prism 52 vertically through the incident surface 52 a ′. Then, the propagated light is emergent from the prism 52 through the emergent surface 52 c and irradiates a recording layer and forms a recording pit.
- the propagated light is reflected by the recording layer and travels backward to the optical diverging circuit 57 . Then, the reflected light is directed to the optical detector 58 via the optical fiber 56 c.
- one light source may be used as the light sources 45 and 55 of the near field light and of the propagated light as has been described in connection with the third embodiment.
- the first through fifth embodiment are optical head devices of a single internal reflection type.
- the sixth embodiment is an optical head device of a double internal reflection type.
- the number 101 denotes a recording medium
- the number 110 denotes an optical head device.
- the recording medium 101 has a recording layer 103 on a substrate 102 and can be driven to rotate on a rotary driving shaft 104 .
- a protective layer may be formed on the recording layer 103 .
- an optical head has a prism 112 at the end of an arm 111 .
- a light source 115 On the arm 111 , a light source 115 , a collimator lens 116 (see FIG. 16 ), a polarizing beam splitter 117 , a ⁇ /4 wavelength plate 118 and an optical detector 119 are provided
- the prism 112 has an incident surface 112 a , a first internal reflective surface 112 b , a second internal reflective surface 112 c and an emergent surface 112 d .
- the incident surface 112 a and the emergent surface 112 d are plane. Referring to FIG. 17 , the internal reflective surfaces 112 b and 112 c are described. In FIG.
- the point P is the intersection of lines which are extended in the reverse direction to the side rays of the light reflected by the first internal reflective surface 112 b
- the point O is a converging point on which the light reflected by the second internal reflective surface 112 c is converged.
- the first internal reflective surface 112 b is a paraboloid of revolution which has a focal point on the point P
- the second internal reflective surface 112 c is an ellipsoid of revolution which has two focal points on the point P and on the point O.
- the paraboloid of revolution 112 b and the ellipsoid of revolution 112 c are so designed that neither of the respective axes of rotation symmetry intersects the center of the bundle of rays emitted from the light source 116 .
- the internal reflective surfaces 112 b and 112 c are made by forming reflective films 113 a and 113 b (for example, Au, Ag, Cu, Cr, Ni or Al) thereon.
- the paraboloid of revolution 112 b and the ellipsoid of revolution 112 c are expressed by the following expression in the XYZ rectangular coordinate system.
- Z cY 2 /1+(1 ⁇ c 2 Y 2 ) 1/2 ⁇
- the prism 112 is made of, for example, glass such as LaSF, LaF, BaSF, etc.
- the prism 112 is a high-refractive medium and at least has a higher refractive index than the medium which is in contact with the emergent surface 112 d.
- the light source 115 may have a laser diode, a light emitting diode or any other light emitting source.
- the center ray L of the bundle of rays converging on the emergent surface 112 d of the prism 112 is perpendicular to the emergent surface 112 d.
- the gap between the recording layer 103 of the recording medium 101 and the emergent surface 112 d is set not more than 1 ⁇ 4 of the wavelength ⁇ (60 to 100 nm), and the near field light N irradiates the recording layer 103 and forms a recording pit 103 a.
- the spot diameter S 1 (see FIG. 17 ) of the near field light N is substantially equal to that of the light beam as if still traveling in the prism and is substantially 1/n (n: refractive index of the prism) of the spot diameter of the light when traveling in the air.
- the wavelength ⁇ of the incident light is 650 nm
- the refractive index n of the prism 112 is 1.8
- the diameter W of the incident beam is 1 mm and if the prism 112 has a height of 2.1 mm and a length of 3.5 mm
- the spot diameter S 1 of the near field light N is approximately 260 nm
- the recording density is approximately 7 Gbit/inch 2 , which is extremely high.
- first internal reflective surface 112 b is a paraboloid of revolution which has a focal point on the point P and because the second internal reflective surface 112 c is an ellipsoid of revolution which has two focal points on the point P and on the point O, these surfaces 112 b and 112 c have a function of correcting spherical aberration of a parallel bundle of rays.
- the near field light N irradiates the recording pit 3 a of the recording layer in the way described in connection with the recording process and is reflected thereon, and the reflected light travels backward.
- the reflected light is emergent from the prism 112 through the incident surface 112 a and passes through the ⁇ /4 wavelength plate 118 again.
- the light is reflected by the beam splitter 117 and received by the optical detector 119 .
- a reading signal of the recording pit 103 a is obtained.
- the reflected light is directed to the optical detector 119 without returning to the light source 115 , whereby a reading signal in good conditions can be obtained.
- the power of the light source 115 for reading may be weaker than that for recording. Erasing is carried out in a similar process; if necessary, however, the wavelength of light may be changed.
- the head is composed of the prism 112 , and neither a convergent lens nor a reflective mirror is necessary. Thus, the head is small and light and can be floated based on the air lubricating principle. Since neither a convergent lens nor a reflective mirror is necessary, the freedom of the design of the optical system is large.
- the beam spot S incident to the prism 112 is preferably elliptic as shown by FIGS. 18 and 19 .
- FIG. 18 is the section cut along the line “XVIII-XVIII” in FIG. 17
- FIG. 19 is the section cut along the line “XIX-XIX” in FIG. 17 .
- the longer axis of the beam spot S extends in the X direction, and the prism 112 has a larger numerical aperture in the X direction. Accordingly, the spot diameter S 2 (see FIG. 19 ) on the converging point O in the X direction is larger than the spot diameter S 1 in the Z direction (see FIG. 17 ).
- the longer axis a and the shorter axis b of the incident beam spot S is 1.5 mm and 1 mm, respectively, if the wavelength ⁇ of the incident beam is 650 nm, the refractive index n of the prism 112 is 1.8 and if the prism 112 has a height of 2.1 mm and has a length of 3.5 mm, the spot diameter S 1 in the Z direction is approximately 260 nm, while the spot diameter S 2 in the X direction is approximately 220 nm. Accordingly, if the X direction corresponds to the circular direction (recording direction) of the recording medium 101 , the recording density is improved.
- FIG. 20 shows a modification of the sixth embodiment.
- the collimator lens 116 shown in FIG. 16 is omitted, and a divergent bundle of rays is incident to the prism 112 .
- the incident surface 112 a of the prism 112 is convex and changes the incident divergent light into a parallel bundle of rays.
- FIG. 21 shows another modification of the sixth embodiment.
- a minuscule opening 114 a is made at the converging point on the emergent surface 112 d of the prism 112 .
- a light shutter film 114 is covered on the emergent surface 112 d, and at the converging point, a minuscule opening 114 a is made in the light shutter film 114 .
- the light shutter film 114 may be made of the same material of the reflective films 113 a and 113 b .
- the seventh embodiment for recording, reading and erasing, light of a wavelength ⁇ 1 , light of a wavelength of ⁇ 2 and light of a wavelength of ⁇ 8 are used, respectively.
- the seventh embodiment is of the same structure as the sixth embodiment.
- the light source 115 has light emitting sources which emit light of a wavelength ⁇ 1 , light of a wavelength of ⁇ 2 and light of a wavelength of ⁇ 3 , respectively and switches these light emitting sources for recording, reading and erasing to emit the light of the respective wavelengths toward the prism 112 .
- the recording layer 103 is preferably a photochromic medium.
- 1,2-bis(2,4,5-trimethyl-3-thienyl)-cis-1,2-dicyanoethene (trade name, made by Tokyo Chemical Industry Co., Ltd.) can be named.
- light of 355 nm is used for recording; light of 532 nm is used for reading; and light of 780 nm is used for erasing.
- Recording, reading and erasing in the seventh embodiment are carried out in the same processes as described in the sixth embodiment except that it is necessary to switch the wavelength of light.
- the eighth embodiment is an optical head device 140 which is a combination of a prism 142 and an optical waveguide 146 .
- the optical waveguide 146 are composed of three optical fibers 146 a, 146 b and 146 c (of a conventional type of which core 151 is covered with cladding 152 ) which are provided on an arm 141 , and the respective one ends of the optical fibers 146 a, 146 b and 146 c are connected to an optical diverging circuit 147 .
- the other end of the optical fiber 146 a is connected to a light source 146 ; the other end of the optical fiber 146 b is connected to an incident surface 142 a of the prism 142 ; and the other end of the optical fiber 146 c is connected to an optical detector 148 .
- the optical fibers 146 a, 146 b and 146 c single-mode fibers which have a core diameter of 4 ⁇ m, a cladding diameter of 125 ⁇ m are used.
- the light source 145 comprises a light emitting source, such as a laser diode, a light emitting diode or the like, a collimator lens and an objective lens. Collimated light of a specified wavelength is incident to the optical fiber 146 a.
- the prism 142 has an incident surface 142 a, a first internal reflective surface 142 b , a second internal reflective surface 142 c and an emergent surface 142 d .
- the incident surface 142 a , the first internal reflective surface 142 b and the emergent surface 142 d are plane.
- the second internal reflective surface 112 c is described.
- the point P is the intersection of lines which are extended in the reverse direction to the side rays of the light reflected by the first internal reflective surface 142 b , that is, the mirror image point of the emergent point R of the optical fiber 146 b in connection with the first internal reflective surface 142 b.
- the point O is a converging point on which the light reflected by the second internal reflective surface 112 c is converged.
- the second internal reflective surface 142 c is an ellipsoid of revolution which has two focal points on the point P and on the point O.
- the ellipsoid of revolution 142 c is so designed that its axis of rotation symmetry does not intersect the center of the bundle of rays emitted from the light source 146 .
- the internal reflective surfaces 142 b and 142 c are made by forming reflective films 143 a and 143 b.
- light of a wavelength ⁇ emitted from the light source 145 is incident to the optical fiber 146 a and further incident to the prism 142 via the optical diverging circuit 147 and the optical fiber 146 b.
- the incident light is reflected by the reflective surface 142 b once and reflected by the reflective surface 142 c once.
- the light is converged on the emergent surface 142 d of the prism 142 , and the light effuses through the emergent surface 142 d as a near field light N.
- the center ray L of the bundle of rays converging on the emergent surface 142 d of the prism 142 is perpendicular to the emergent surface 142 d.
- the gap between the emergent surface 142 d and the recording layer 103 of the recording medium 101 is set not more than 1 ⁇ 4 of the wavelength ⁇ (50 to 100 nm), and the near filed light N irradiates the recording layer 103 and forms a recording pit 103 a.
- the internal reflective surface 142 c of the prism 142 is an ellipsoid of revolution which has two focal points on the emergent point R of the optical fiber 146 b , that is, the beam waist W of the light beam emitted from the optical fiber 146 b and on the converging point O.
- the light beam emergent from the optical fiber 146 b is a divergent bundle of rays
- the reflective surface 142 c which is an ellipsoid of revolution has a function of correcting spherical aberration of a divergent bundle of rays.
- the near field light N is reflected on the recording layer 103 at the recording pit 103 a and travels backward in the prism 142 . Then, the reflected light is converged on the end surface of the optical fiber 146 b . This reflected light travels to the optical diverging circuit 147 through the optical fiber 146 b and is directed to the optical detector 148 by the optical fiber 146 c. Thereby, a reading signal of the recording pit 103 a is obtained.
- the power of the light source 145 for reading may be weaker than the power for recording. Erasing is carried out in a similar process; the wavelength of light, however, may be required to be changed.
- the eighth embodiment brings the same effects as the sixth embodiment. Moreover, because the prism 142 is connected to the optical waveguide 146 , the optical head device 140 is stable against vibration of the arm 141 due to vibration of the recording medium 101 and external vibration and shock, and the optical axis does not shift, which secures stable recording/reading performance.
- a modification shown by FIG. 20 can be adopted.
- a minuscule opening may be made on the converging point O of the emcrgent surface 142 d as FIG. 21 shows.
- FIG. 22 shows, light of a wavelength ⁇ 1 , light of a wavelength ⁇ 2 and light of a wavelength ⁇ 3 may be used.
- the optical waveguide a thin film waveguide of a ZnO layer can be used as well as optical fibers.
- the light source and the optical elements may be of any other structure, and the prism may be of any other shape.
- the emergent surface of the prism may be convex toward the recording medium so that positioning of the optical head in a closed place to the recording medium will be easier.
- the light converges on the converging point O of the emergent surface of the prism in such a way that the center ray L is perpendicular to the emergent surface of the prism, it is satisfactory even if the angle of the center ray L shifts within ⁇ 10° from the vertical direction. If the angle of the center ray L shifts more, the quantity of light transmitting through the minuscule opening may be lowered, and near field light distribution may be out of order, which are undesirable.
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Head (AREA)
Abstract
An optical head which has a prism with an incident section, an internal reflective surface and an emergent surface, and an optical head device which employs the optical head. Light emitted from a light source is incident to the prism through the incident section, reflects at least once on the internal reflective surface and is converged in the vicinity of the emergent surface. Then, the light effuses through the emergent surface as near field light.
Description
- This application is based on application Nos. 10-337671 and 11-077460 filed in Japan, the content of which is hereby incorporated by reference.
- 1. Field of the Invention
- The present invention relates to an optical head and an optical head device, and more particularly to an optical head which is suited to be used for high-density recording/reading erasing of information to or from an optical recording medium and an optical head device using this optical head.
- 2. Description of Related Art
- In the art of optical memories which optically record and read information, in recent years, with speed-up of computer processing and development of multimedia, high-density devices which are capable of recording an extremely large volume of information are demanded, and in order to comply with the demand, a near field optical recording technique is suggested. In a conventional optical memory using a laser beam, the recording density is limited depending on the diffraction limit of light, and such an optical memory can record and read marks of sizes at least light wavelength (several hundred nanometers). A recently proposed optical memory which uses near field optics radiates light to a recording medium (optical disk) for recording/reading with the optical head and the recording medium arranged at an interval of only some dozen nanometers. At this time, the optical memory uses a fiber probe with a minuscule aperture smaller than light wavelength and a solid immersion lens. Thereby, in spite of the diffraction limit, it becomes possible to record and read minuscule marks of some dozen nanometers.
- In a conventional memory which uses propagated light, such as a CD, a DVD, an MO or the like, a convergent lens, a mirror, a prism and other optical elements are installed in the optical head, and the optical head is large and heavy. It is, therefore, difficult to adopt an air floating method based on the air lubricating principle, which is generally adopted in magnetic recording heads, in such an optical memory. In the above-mentioned optical head using a solid immersion lens, although the solid immersion lens itself is small and light, it is necessary to further use a convergent lens, which indispensably increases the size and weight.
- Lately, “Objective Lenses for DVD& Near Field Optical Disk Pick-up” ODF'98, Tokyo, Jun. 16, 1998 suggests an SIM (solid immersion mirror) which does not require a convergent lens. This SIM converges light by performing refraction once and reflection twice in a prism. Since this eliminates the necessity of using a convergent lens, an optical head using this SIM is small and light. However, because the SIM uses a coaxial optical system, the design is strongly limited. Also, since a direction of light incident to the SIM is perpendicular to a recording surface, a mirror for bending optical path of incident light is required. Accordingly, vibration and shift of the mirror must be adjusted, which obstructs reduction of the size and weight of the optical head device.
- An object of the present invention is to provide a small and light optical head.
- Another object of the present invention is to provide an optical head device of which optical system can be designed freely.
- Another object of the present invention is to provide an optical head device in which light has only a small loss.
- Another object of the present invention is to provide a near field optical head which is suited to make a gap from a recording medium by an air floating method.
- Another object of the present invention is to provide an optical head which is capable of correcting spherical aberration when a parallel bundle of rays is incident thereto.
- Another object of the present invention is to provide an optical head which is capable of using a divergent bundle of rays as incident light thereto.
- Another object of the present invention is to provide an optical head which is capable of recording, reading and erasing information at a higher density by reducing the diameter of a near field light beam.
- Another object of the present invention is to provide an optical head device which is strong against external vibration and shock.
- Another object of the present invention is to provide an optical head device which records, reads and erases information by use of either one selected from near field light and propagated light.
- Another object of the present invention is to provide an optical head device which uses a non-coaxial optical system.
- In order to attain the objects, an optical head device according to the present invention comprises: a first light source which emits light; and a prism which receives the light emitted from the first light source as first incident light, reflects the first incident light inside at least once and emits the first incident light in a direction different from a direction in which the first incident light was incident thereto.
- A prism according to the present invention comprises: an incident section which receives incident light; a first surface which reflects the incident light received by the incident section in the prism; and a second surface through which the light reflected by the first surface is emergent from the prism for reading of information.
- Another prism according to the present invention comprises: an incident section which receives incident light; a first surface which reflects the incident light received by the incident section in the prism; a second surface which reflects the light reflected by the first surface in the prism in a direction which is different from a direction in which the incident light was received by the incident section; and a third surface through which the light reflected by the second surface is emergent from the prism for reading of information.
- Another prism according to the present invention uses near field light occurring on an emergent surface for recording, reading and erasing of information, and the prism comprises an internal reflective surface which reflects light which was incident to the prism inside and converges the light on a vicinity of the emergent surface. In this prism, a non-oaxial optical system is formed.
- According to the present invention, light of a specified wavelength which was incident to a prism through an incident section is reflected inside at least once and is converged on an emergent surface. Then, the light effuses through the emergent surface as near field light (in other words, optical near field). By use of this near field light, recording, reading and erasing of information are carried out. According to the present invention, an optical head can be composed of only a prism. Accordingly, the optical head is small and light and has a simple optical system. Also, an air floating method can be adopted in making a gap between the optical head and a recording medium.
- These and other objects and features of the present invention will be apparent from the following description with reference to the accompanying drawings, in which:
-
FIG. 1 is a schematic structural view of an optical head device which is a first embodiment of the present invention; -
FIG. 2 is an illustration which shows an occurrence of near field light in the first embodiment; -
FIG. 3 is an illustration which shows travel of light in a prism; -
FIG. 4 is an illustration which shows an incident light beam spot, which is a sectional view cut along “IV-IV” inFIG. 3 . -
FIG. 5 is an illustration which shows an incident light beam spot and an occurrence of near field light, which is a sectional view cut along “V-V” inFIG. 3 ; -
FIG. 6 is a schematic structural view of a modification of the first embodiment; -
FIG. 7 is a schematic structural view of another modification of the first embodiment; -
FIG. 8 is a schematic structural view of another modification of the first embodiment; -
FIG. 9 is a schematic structural view of the main part of an optical head device which is a second embodiment of the present invention; -
FIG. 10 is a schematic structural view of an optical head device which is a third embodiment of the present invention; -
FIG. 11 is an illustration which shows travel of light in a prism in the third embodiment; -
FIG. 12 is a schematic structural view of an optical head device which is a fourth embodiment of the present invention; -
FIG. 13 is an illustration which shows an occurrence of near field light in the fourth embodiment; -
FIG. 14 is a schematic structural view of an optical head device which is a fifth embodiment of the present invention; -
FIG. 15 is a schematic structural view of an optical head device which is a sixth embodiment of the present invention; -
FIG. 16 is an illustration which shows of an occurrence of near field light in the sixth embodiment; -
FIG. 17 is an illustration which shows travel of light in a prism in the sixth embodiment; -
FIG. 18 is an illustration which shows an incident light beam spot, which is a sectional view cut along “X VIII-X VIII” inFIG. 17 ; -
FIG. 19 is an illustration which shows an incident light beam spot and an occurrence of near field light, which is a sectional view cut along “XIX-XIX” inFIG. 17 ; -
FIG. 20 is a schematic structural view of a modification of the sixth embodiment; -
FIG. 21 is a schematic structural view of another modification of the sixth embodiment; -
FIG. 22 is a schematic structural view of an optical head device which is a seventh embodiment of the present invention; -
FIG. 23 is a schematic structural view of an optical head device which is an eighth embodiment of the present invention; and -
FIG. 24 is an illustration which shows travel of light in a prism in the eighth embodiment. - Preferred embodiments of an optical head and an optical head device according to the present invention are described with reference to the accompanying drawings.
- In
FIGS. 1 and 2 , thenumber 1 denotes a recording medium, and thenumber 10 denotes an optical head device. Therecording medium 1 has arecording layer 3 on asubstrate 2 and can be driven to rotate on a rotary driving shaft 4. A protective layer may be formed on therecording layer 3. - The
optical head device 10 has aprism 12 serving as an optical head at the end of anarm 11. On thearm 11, alight source 15, a collimator lens 16 (seeFIG. 2 ), apolarizing beam splitter 17, a λ/4wavelength plate 18, anoptical detector 19 are provided. Theprism 12 has anincident surface 12 a, an internalreflective surface 12 b and anemergent surface 12 c. The incident surface 12 a and theemergent surface 12 c are plane, and the internalreflective surface 12 b is a paraboloid of revolution, of which top is an end P of thesurface 12 b (seeFIG. 3 ). This internalreflective surface 12 b is made by forming areflective material 13 such as Au, Ag, Cu, Cr, Ni, Al or the like into a film. Theprism 12 is made of for example, glass such as LASF, LaF, BaSF, etc. Theprism 12 is a high-refractive medium and at least has a higher refractive index than the medium which is in contact with theemergent surface 12 c. - The
light source 15 may be a laser diode, an LED or any other light emitting source. - First, a recording process is described. Light of a wavelength λ emitted from the
light source 15 is changed into a parallel bundle of rays by thecollimator lens 16, and the parallel bundle of rays is incident to theprism 12 via thepolarizing beam splitter 17 and the λ/4wavelength plate 18. The incident light is reflected by thereflective surface 12 b only once and is converged on theemergent surface 12 c. Then, the light effuses through theemergent surface 12 c as a near field light (in other words, optical near field) N. The gap between theemergent surface 12 c and therecording layer 3 of therecording medium 1 is set not more than ¼ of the wavelength A (60 to 100 nm), so that the near field light N irradiates therecording layer 3 and forms arecording pit 3 a thereon. - The spot diameter s of the near field light N (see
FIG. 3 ) is substantially equal to that of the light beam as if still traveling in theprism 12 and is substantially 1/n (n: refractive index of the prism 12) of that of the light beam when traveling in the air. Referring toFIG. 3 , if the wavelength λ of the incident light is 630 nm, if the refractive index n of theprism 12 is 1.8, if the beam diameter w of the incident light (the parallel bundle of rays) is 1 mm and if the distance d between the converging point O of theprism 12 and the end P of theprism 12 is 0.7 mm, the spot diameter s of the near field light N is approximately 370 nm, and the recording density at this time is approximately 3.5 Gbit/inch2, which is extremely high. - Because the internal
reflective surface 12 b of theprism 12 is a paraboloid of revolution of which top is the end P of theprism 12, this surface has a function of correcting spherical aberration of a parallel bundle of rays. - Next, a reading process is described. As has been described in connection with the recording process, the near field light N irradiates the
recording layer 3 on therecording pit 3 a. In this process, the near field light N is reflected by therecording layer 3, and the reflected light travels backward. The reflected light is emergent from theprism 12 through theincident surface 12 a, passes through the λ/4wavelength plate 18 again and is reflected by thebeam splitter 17. Then, the light is received by theoptical detector 19. Thereby, a reading signal of therecording pit 3 a can be obtained. Because of the λ/4wavelenth plate 18, the reflected light is securely directed to theoptical detector 19 without returning to thelight source 15, whereby the reading signal can be obtained in good conditions. The power of thelight source 15 for reading may be weaker than that for recording. Erasing is carried out in a similar process; if necessary, however, the wavelength of light may be changed. - In the first embodiment, incident light to the
prism 12 is internally reflected once and is converged on theemergent surface 12 c, which causes a near field light N to effuse therethrough to carry out recording, reading or erasing. The head is composed of only theprism 12, and neither a convergent lens nor a reflective mirror is necessary. Consequently, the head is small and light and can be floated based on the air lubricating principle. Because the light is reflected in theprism 12 only once, the loss of light is small. Because the light has only a small loss in theprism 12 and because neither a convergent lens nor a reflective mirror is necessary, the freedom of the design of the optical system is large. - The Shape of the Incident Beam Spot; See
FIGS. 4 and 5 - The incident beam spot is preferably elliptical as indicated by “S” in
FIGS. 4 and 5 .FIG. 4 is the section cut along the line “IV-IV” inFIG. 3 , andFIG. 5 is the section cut along the line “V-V” inFIG. 3 . The longer axis of the beam spot S extends in the X direction, and theprism 12 has a larger numerial aperture in the X direction. Accordingly, the diameter s′ of the beam spot on the converging point O in the X direction (seeFIG. 5 ) is smaller than the diameter s in the Z direction (seeFIG. 3 ). - Now, a specific example is given, referring to
FIG. 4 . If the longer axis a and the shorter axis b of the incident beam spot S is 1.6 mm and 1 mm, respectively, and if the distance d is 0.7 mm, the spot diameter s in the Z direction is approximately 370 nm, while the spot diameter s′ in the X direction is approximately 240 nm. Accordingly, if the X direction corresponds to the circular direction (recording direction) of therecording medium 1, the recording density is improved. -
FIG. 6 shows a modification of the first embodiment. In this modification, light is incident to theprism 12 from slightly downward, not in parallel to the surface of therecording medium 1. The incident surface 12 a of theprism 12 is slightly tilted so as to be perpendicular to the incident light. By making the light incident to theprism 12 from slightly downward, the numerical aperture of theprism 12 on theemergent surface 12 c becomes larger, and accordingly, the spot diameter on the converging point O becomes smaller. -
FIG. 7 shows another modification of the first embodiment. In this modification, thecollimator lens 16 shown inFIG. 2 is omitted, and a divergent bundle of rays is incident to theprism 12. The incident surface 12 a of theprism 12 is convex and converges the incident divergent light into a parallel bundle of rays. -
FIG. 8 shows another modification of the first embodiment. In this modification, aminuscule opening 14 a is made at the converging point on theemergent surface 12 c of theprism 12. Specifically, alight shutter film 14 is covered on theemergent surface 12 c, and at the converging point, aminuscule opening 14 a is made in thelight shutter film 14. Thelight shutter film 14 may be made of the same material of thereflective film 13. By providing theminuscule opening 14 a, the spot of the near filed light N can be made smaller, which permits higher-density recording. - In the second embodiment, for recording, reading and erasing, light of a wavelength λ1, light of a wavelength of λ2 and light of a wavelength of λ3 are used, respectively. The second embodiment is of the same structure as the first embodiment. The
light source 15 has light emitting sources which emit light of a wavelength λ1, light of a wavelength of λ2 and light of a wavelength of λ3, respectively and switches these light emitting sources for recording, reading and erasing to emit the light of the respective wavelengths toward theprism 12. - In this case, the
recording layer 3 is preferably a photochromic medium. As a specific example, 1,2-bis (2,4,5-trimethyl-3-thienyl)-cis-1,2-dicyanoethene (trade name, made by Tokyo Chemical Industry Co., Ltd.) can be named. For such arecording layer 3, light of 355 nm is used for recording; light of 632 nm is used for reading; and light of 780 nm is used for erasing. - Recording, reading and erasing in the second embodiment are carried out in the same processes as described in the first embodiment except that it is necessary to switch the wavelength of light.
- The third embodiment is a compatible optical head device which has a
prism 22 so as to carry out recording, reading and erasing not only by a near field light but also by a propagated light beam. Accordingly, this device also can be used to record, read and erase information to and from conventional optical disk media such as CDs, DVDs, etc. by use of a propagated light beam. - The head using a near field light is basically of the same structure as that of the first embodiment, and in
FIG. 10 , the same members are denoted by the same reference symbols as inFIG. 1 . Referring toFIG. 11 , theprism 22 has anincident surface 22 a and an internal reflective surface 22 b on which areflective film 23 is formed. A near field light N effuses through anemergent surface 22 c at a converging point O. The internal reflective surface 22 b is a paraboloid of revolution of which top is its end P. - Recording, reading and erasing by use of the
prism 22 and the near field light N are carried out in the processes described in connection with the first embodiment, and the same effects can be obtained. The detailed description is omitted here. - In order to carry out recording, reading and erasing by use of a propagated light beam, a
light source 35, a collimator lens (not shown), apolarizing beam splitter 37, a λ/4wavelength plate 38, anoptical detector 39 and a mirror 34 are provided. Also, theprism 22 has aconvex incident surface 22 a′. - A light beam of a wavelength A4 emitted from the
light source 35 is changed into a parallel bundle of rays by the collimator lens and passes through thepolarizing beam splitter 37 and the λ/4wavelength plate 38. Thereafter, the beam is reflected by the mirror 34 and is incident to theprism 22 vertically through theincident surface 22 a′. AsFIG. 11 shows, this incident light is refracted and converged in theprism 22 and is emergent from theprism 22 through theemergent surface 22 c as a propagated light beam T. The emergent light beam, of which spot diameter is s1, irradiates the recording layer of a recording medium and forms a recording pit. - The spot diameter s1 of the propagated light beam T is larger than the spot diameter s of the near field light N. Referring to
FIG. 11 , if thelight source 35 emits a light beam of 780 nm (wavelength λ4=780 nm) at an emergent angle θ of 30°, the spot diameter s1 of the propagated light beam T emergent from theprism 22 is approximately 780 nm. The spot diameter s of the near field light N is, under the conditions specified in the first embodiment, approximately 370 nm. Thus, the spot diameter s1 is larger than the spot diameter s. - In a reading process by use of the propagated light beam, the light beam T is reflected by the recording layer, and the reflected light is incident to the
prism 22 and is emergent from theprism 22 through theincident surface 22 a′. The light is, thereafter, reflected by the mirror 34, deflected by the λ/4wavelength plate 38 and reflected by thepolarizing beam splitter 37. Then, the light is received by theoptical detector 39. - The wavelength λ4 of the light emitted from the
light source 35 may be equal to or different from the wavelength λ of the light emitted from thelight source 15. If the wavelength λ4 is equal to the wavelength λ, either thelight source 35 or thelight source 15 and the corresponding collimator lens can be omitted. In this case, light emitted from the remained light source is split to travel to thepolarizing beam splitter 17 and to thepolarizing beam splitter 37. - In the third embodiment, the modifications shown by
FIGS. 6, 7 and 8 can be adopted. Further, asFIG. 9 shows, the wavelength of the light emitted from the light source may be changeable between λ1, λ2 and λ3. - The fourth embodiment is an
optical head device 40 which is a combination of aprism 42 and anoptical waveguide 46. Theoptical waveguide 46 are composed of threeoptical fibers arm 41, and the respective one ends of theoptical fibers circuit 47. The other end of theoptical fiber 46 a is connected to alight source 45; the other end of theoptical fiber 46 b is connected to an incident surface 42 a of theprism 42; and the other end of theoptical fiber 46 c is connected to anoptical detector 48. As theoptical fibers - The
light source 45 comprises a light emitting source, such as a laser diode, a light emitting diode or the like, a collimator lens and an objective lens. Collimated light of a specified wavelength is incident to theoptical fiber 46 a. Theprism 42 is basically of the same structure and the same materials as theprism 12, and on an internalreflective surface 42 b, areflective film 43 is formed (seeFIG. 13 ). - In a recording process, light of a wavelength λ emitted from the
light source 45 is incident to theoptical fiber 46 a and further incident to theprism 42 via the optical divergingcircuit 47 and theoptical fiber 46 b. The incident light is reflected by thereflective surface 42 b once and converged on anemergent surface 42 c of theprism 42. Then, the light effuses through theemergent surface 42 c as a near field light N. The gap between theemergent surface 42 c and therecording layer 3 of therecording medium 1 is set not more than ¼ of the wavelength λ(50 to 100 nm), and the near filed light N irradiates therecording layer 3 and forms arecording pit 3 a. - The internal
reflective surface 42 b of theprism 42 is an ellipsoid of revolution which has two focal points on the beam waist W of the light beam emitted from theoptical fiber 46 b and on the converging point O. The light beam emergent from theoptical fiber 46 b is a divergent bundle of rays, and thereflective surface 42 b which is an ellipsoid of revolution has a function of correcting spherical aberration of a divergent bundle of rays. - In a reading process, the near field light N is reflected on the
recording layer 3 and travels backward in theprism 42. Then, the reflected light is converged on the end surface of theoptical fiber 46 b. This reflected light travels to the optical divergingcircuit 47 through theoptical fiber 46 b and is directed to theoptical detector 48 by theoptical fiber 46 c. Thereby, a reading signal of therecording pit 3 a is obtained The power of thelight source 45 for reading may be weaker than the power for recording. Erasing is carried out in a similar process; the wavelength of light, however, may be required to be changed. - The fourth embodiment brings the same effects as the first embodiment. Moreover, because the
prism 42 is connected to theoptical waveguide 46, theoptical head device 40 is stable against vibration of thearm 41 due to vibration of therecording medium 1 and external vibration and shock, and the optical axis does not shift, which secures stable recording/reading performance. - Further, in the fourth embodiment, a minuscule opening may be made on the converging point O of the
emergent surface 42 c asFIG. 8 shows. As the optical waveguide, a thin film waveguide of a ZnO layer can be used as well as optical fibers. - The fifth embodiment is a compatible optical head device like the third embodiment and uses an optical waveguide. The fifth embodiment has a
prism 52 which is of the same structure as theprism 22 shown byFIG. 11 . Theprism 52 has incident surfaces 52 a, 52 a′, an internalreflective surface 52 b and anemergent surface 52 c. In the fifth embodiment, the optical system for a near field light is of the same structure as the fourth embodiment, and recording and reading are carried out in the same processes as described in the fourth embodiment. - The optical system for a propagated light beam is basically of the same structure of the optical system for a near field light. The optical system for a propagated light beam comprises a
light source 55, anoptical waveguide 56 composed ofoptical fibers circuit 57 and anoptical detector 58. Light emitted from thelight source 55 travels through the optical fiber 56 a, the optical divergingcircuit 57 and theoptical fiber 56 b and is incident to theprism 52 vertically through theincident surface 52 a′. Then, the propagated light is emergent from theprism 52 through theemergent surface 52 c and irradiates a recording layer and forms a recording pit. - In a reading process, the propagated light is reflected by the recording layer and travels backward to the optical diverging
circuit 57. Then, the reflected light is directed to theoptical detector 58 via theoptical fiber 56 c. - In the fifth embodiment, one light source may be used as the
light sources - The first through fifth embodiment are optical head devices of a single internal reflection type. The sixth embodiment is an optical head device of a double internal reflection type.
- In
FIGS. 15 and 16 , thenumber 101 denotes a recording medium, and thenumber 110 denotes an optical head device. Therecording medium 101 has arecording layer 103 on asubstrate 102 and can be driven to rotate on arotary driving shaft 104. On therecording layer 103, a protective layer may be formed. - In the
optical head device 110, an optical head has aprism 112 at the end of anarm 111. On thearm 111, alight source 115, a collimator lens 116 (seeFIG. 16 ), a polarizing beam splitter 117, a λ/4wavelength plate 118 and anoptical detector 119 are provided Theprism 112 has anincident surface 112 a, a first internalreflective surface 112 b, a second internalreflective surface 112 c and anemergent surface 112 d. Theincident surface 112 a and theemergent surface 112 d are plane. Referring toFIG. 17 , the internalreflective surfaces FIG. 17 , the point P is the intersection of lines which are extended in the reverse direction to the side rays of the light reflected by the first internalreflective surface 112 b, and the point O is a converging point on which the light reflected by the second internalreflective surface 112 c is converged. The first internalreflective surface 112 b is a paraboloid of revolution which has a focal point on the point P, and the second internalreflective surface 112 c is an ellipsoid of revolution which has two focal points on the point P and on the point O. Further, the paraboloid ofrevolution 112 b and the ellipsoid ofrevolution 112 c are so designed that neither of the respective axes of rotation symmetry intersects the center of the bundle of rays emitted from thelight source 116. The internalreflective surfaces reflective films - The paraboloid of
revolution 112 b and the ellipsoid ofrevolution 112 c are expressed by the following expression in the XYZ rectangular coordinate system.
Z=cY 2/1+(1−εc 2 Y 2)1/2} -
- c: curvature
- In the expression, when ε=0, it expresses the paraboloid of
revolution 112 b, and when ε=0.91, it expresses the ellipsoid ofrevolution 112 c. - The
prism 112 is made of, for example, glass such as LaSF, LaF, BaSF, etc. Theprism 112 is a high-refractive medium and at least has a higher refractive index than the medium which is in contact with theemergent surface 112 d. - The
light source 115 may have a laser diode, a light emitting diode or any other light emitting source. - First, a recording process is described. Light of a wavelength λ emitted from the
light source 115 is changed into a parallel bundle of rays by thecollimator lens 116. Then, the light passes through the polarizing beam splitter 117 and theA 14wavelength plate 118 and is incident to theprism 112 through theincident surface 112 a. This incident light is reflected on thereflective surface 112 b once and on thereflective surface 112 c once, and is converged on theemergent surface 112 d. Then, the light effuses through theemergent surface 112 d as a near field light (in other words, optical near field) N. At this time, the center ray L of the bundle of rays converging on theemergent surface 112 d of theprism 112 is perpendicular to theemergent surface 112 d. The gap between therecording layer 103 of therecording medium 101 and theemergent surface 112 d is set not more than ¼ of the wavelength λ (60 to 100 nm), and the near field light N irradiates therecording layer 103 and forms arecording pit 103 a. - The spot diameter S1 (see
FIG. 17 ) of the near field light N is substantially equal to that of the light beam as if still traveling in the prism and is substantially 1/n (n: refractive index of the prism) of the spot diameter of the light when traveling in the air. Referring toFIG. 17 , if the wavelength λ of the incident light is 650 nm, if the refractive index n of theprism 112 is 1.8, if the diameter W of the incident beam (the parallel bundle of rays) is 1 mm and if theprism 112 has a height of 2.1 mm and a length of 3.5 mm, the spot diameter S1 of the near field light N is approximately 260 nm, and the recording density is approximately 7 Gbit/inch2, which is extremely high. - Because the first internal
reflective surface 112 b is a paraboloid of revolution which has a focal point on the point P and because the second internalreflective surface 112 c is an ellipsoid of revolution which has two focal points on the point P and on the point O, thesesurfaces - Next, a reading process is described. The near field light N irradiates the
recording pit 3 a of the recording layer in the way described in connection with the recording process and is reflected thereon, and the reflected light travels backward. The reflected light is emergent from theprism 112 through theincident surface 112 a and passes through the λ/4wavelength plate 118 again. Then, the light is reflected by the beam splitter 117 and received by theoptical detector 119. Thereby, a reading signal of therecording pit 103 a is obtained. Because of the λ/4wavelength plate 118, the reflected light is directed to theoptical detector 119 without returning to thelight source 115, whereby a reading signal in good conditions can be obtained. The power of thelight source 115 for reading may be weaker than that for recording. Erasing is carried out in a similar process; if necessary, however, the wavelength of light may be changed. - In the sixth embodiment, light is incident to the
prism 112 to be reflected twice therein and is converged on theemergent surface 112 d. Then, recording, reading and erasing are carried out by the resultant near field light N. The head is composed of theprism 112, and neither a convergent lens nor a reflective mirror is necessary. Thus, the head is small and light and can be floated based on the air lubricating principle. Since neither a convergent lens nor a reflective mirror is necessary, the freedom of the design of the optical system is large. - The shape of the Incident Beam Spot; See
FIGS. 18 and 19 - The beam spot S incident to the
prism 112 is preferably elliptic as shown byFIGS. 18 and 19 .FIG. 18 is the section cut along the line “XVIII-XVIII” inFIG. 17 , andFIG. 19 is the section cut along the line “XIX-XIX” inFIG. 17 . The longer axis of the beam spot S extends in the X direction, and theprism 112 has a larger numerical aperture in the X direction. Accordingly, the spot diameter S2 (seeFIG. 19 ) on the converging point O in the X direction is larger than the spot diameter S1 in the Z direction (seeFIG. 17 ). - Referring to
FIG. 18 , if the longer axis a and the shorter axis b of the incident beam spot S is 1.5 mm and 1 mm, respectively, if the wavelength λ of the incident beam is 650 nm, the refractive index n of theprism 112 is 1.8 and if theprism 112 has a height of 2.1 mm and has a length of 3.5 mm, the spot diameter S1 in the Z direction is approximately 260 nm, while the spot diameter S2 in the X direction is approximately 220 nm. Accordingly, if the X direction corresponds to the circular direction (recording direction) of therecording medium 101, the recording density is improved. -
FIG. 20 shows a modification of the sixth embodiment. In this modification, thecollimator lens 116 shown inFIG. 16 is omitted, and a divergent bundle of rays is incident to theprism 112. Theincident surface 112 a of theprism 112 is convex and changes the incident divergent light into a parallel bundle of rays. -
FIG. 21 shows another modification of the sixth embodiment. In this modification, aminuscule opening 114 a is made at the converging point on theemergent surface 112 d of theprism 112. Specifically, alight shutter film 114 is covered on theemergent surface 112 d, and at the converging point, aminuscule opening 114 a is made in thelight shutter film 114. Thelight shutter film 114 may be made of the same material of thereflective films minuscule opening 114 a, the spot of the near filed light N can be made smaller, which permits higher-density recording. - In the seventh embodiment, for recording, reading and erasing, light of a wavelength λ1, light of a wavelength of λ2 and light of a wavelength of λ8 are used, respectively. The seventh embodiment is of the same structure as the sixth embodiment. The
light source 115 has light emitting sources which emit light of a wavelength λ1, light of a wavelength of λ2 and light of a wavelength of λ3, respectively and switches these light emitting sources for recording, reading and erasing to emit the light of the respective wavelengths toward theprism 112. - In this case, the
recording layer 103 is preferably a photochromic medium. As a specific example, 1,2-bis(2,4,5-trimethyl-3-thienyl)-cis-1,2-dicyanoethene (trade name, made by Tokyo Chemical Industry Co., Ltd.) can be named. For such arecording layer 103, light of 355 nm is used for recording; light of 532 nm is used for reading; and light of 780 nm is used for erasing. - Recording, reading and erasing in the seventh embodiment are carried out in the same processes as described in the sixth embodiment except that it is necessary to switch the wavelength of light.
- As
FIGS. 23 and 24 show, the eighth embodiment is anoptical head device 140 which is a combination of aprism 142 and anoptical waveguide 146. Theoptical waveguide 146 are composed of threeoptical fibers core 151 is covered with cladding 152) which are provided on anarm 141, and the respective one ends of theoptical fibers circuit 147. The other end of theoptical fiber 146 a is connected to alight source 146; the other end of theoptical fiber 146 b is connected to anincident surface 142 a of theprism 142; and the other end of the optical fiber 146 c is connected to anoptical detector 148. As theoptical fibers - The
light source 145 comprises a light emitting source, such as a laser diode, a light emitting diode or the like, a collimator lens and an objective lens. Collimated light of a specified wavelength is incident to theoptical fiber 146 a. Theprism 142 has anincident surface 142 a, a first internalreflective surface 142 b, a second internalreflective surface 142 c and an emergent surface 142 d. Theincident surface 142 a, the first internalreflective surface 142 b and the emergent surface 142 d are plane. - Referring to
FIG. 24 , the second internalreflective surface 112 c is described. In FIG, 24, the point P is the intersection of lines which are extended in the reverse direction to the side rays of the light reflected by the first internalreflective surface 142 b, that is, the mirror image point of the emergent point R of theoptical fiber 146 b in connection with the first internalreflective surface 142 b. The point O is a converging point on which the light reflected by the second internalreflective surface 112 c is converged. The second internalreflective surface 142 c is an ellipsoid of revolution which has two focal points on the point P and on the point O. Further, the ellipsoid ofrevolution 142 c is so designed that its axis of rotation symmetry does not intersect the center of the bundle of rays emitted from thelight source 146. The internalreflective surfaces reflective films 143 a and 143 b. - In a recording process, light of a wavelength λ emitted from the
light source 145 is incident to theoptical fiber 146 a and further incident to theprism 142 via the optical divergingcircuit 147 and theoptical fiber 146 b. The incident light is reflected by thereflective surface 142 b once and reflected by thereflective surface 142 c once. Then, the light is converged on the emergent surface 142 d of theprism 142, and the light effuses through the emergent surface 142 d as a near field light N. At this time, the center ray L of the bundle of rays converging on the emergent surface 142 d of theprism 142 is perpendicular to the emergent surface 142 d. The gap between the emergent surface 142 d and therecording layer 103 of therecording medium 101 is set not more than ¼ of the wavelength λ (50 to 100 nm), and the near filed light N irradiates therecording layer 103 and forms arecording pit 103 a. - The internal
reflective surface 142 c of theprism 142 is an ellipsoid of revolution which has two focal points on the emergent point R of theoptical fiber 146 b, that is, the beam waist W of the light beam emitted from theoptical fiber 146 b and on the converging point O. The light beam emergent from theoptical fiber 146 b is a divergent bundle of rays, and thereflective surface 142 c which is an ellipsoid of revolution has a function of correcting spherical aberration of a divergent bundle of rays. - In a reading process, the near field light N is reflected on the
recording layer 103 at therecording pit 103 a and travels backward in theprism 142. Then, the reflected light is converged on the end surface of theoptical fiber 146 b. This reflected light travels to the optical divergingcircuit 147 through theoptical fiber 146 b and is directed to theoptical detector 148 by the optical fiber 146 c. Thereby, a reading signal of therecording pit 103 a is obtained. The power of thelight source 145 for reading may be weaker than the power for recording. Erasing is carried out in a similar process; the wavelength of light, however, may be required to be changed. - The eighth embodiment brings the same effects as the sixth embodiment. Moreover, because the
prism 142 is connected to theoptical waveguide 146, theoptical head device 140 is stable against vibration of thearm 141 due to vibration of therecording medium 101 and external vibration and shock, and the optical axis does not shift, which secures stable recording/reading performance. - Further, in the eighth embodiment, a modification shown by
FIG. 20 can be adopted. Also, a minuscule opening may be made on the converging point O of the emcrgent surface 142 d asFIG. 21 shows. Further, asFIG. 22 shows, light of a wavelength λ1, light of a wavelength λ2 and light of a wavelength λ3 may be used. As the optical waveguide, a thin film waveguide of a ZnO layer can be used as well as optical fibers. - In order to maintain the gap between the optical head and the recording medium, not only an air floating method but also any other methods can be adopted. The light source and the optical elements may be of any other structure, and the prism may be of any other shape. The emergent surface of the prism may be convex toward the recording medium so that positioning of the optical head in a closed place to the recording medium will be easier.
- In the
optical head devices - Although the present invention has been described in connection with the preferred embodiments above, it is to be noted that various changes and modifications are possible to those who are skilled in the art. Such changes and modifications are to be understood as being within the scope of the present invention.
Claims (11)
1-26. (canceled)
27. An optical head device for use in at least one of recording and reading of information to or from an optical recording medium, comprising:
a light source for emitting a light beam; and
a prism for converging the light beam from the light source, the prism comprising:
a first surface through which the light beam advancing along a first direction enters into the prism, the first direction being parallel to a recording surface of the optical recording medium;
a second surface for reflecting the light beam which has entered into the prism through the first surface within the prism;
a third surface for reflecting the light beam reflected by the second surface within the prism; and
a fourth surface through which the light beam reflected by the third surface is emergent from the prism for at least one of recording and reading of information,
wherein, in vicinity of the fourth surface, at least one of the first, second and third surfaces converges the light beam and forms a beam spot.
28. The optical head device according to claim 27 , wherein the third surface reflects the light beam to a second direction which is perpendicular to the first direction.
29. The optical head device according to claim 27 , wherein:
the fourth surface has a light shutter layer having a minuscule opening which is smaller than the beam spot;
the light shutter layer except the minuscule opening prevents the light beam from passing through the fourth surface; and
a near field light effuses from the minuscule opening.
30. The optical head device according to claim 27 , wherein the fourth surface is parallel to the first direction.
31. An optical head device for use in at least one of recording and reading of information to or from an optical recording medium, comprising:
a light source for emitting a light beam; and
a prism for converging the light beam from the light source in vicinity of an emergent surface thereof, wherein
a light beam advancing along a direction parallel to a recording surface of the recording medium enters into the prism;
the light beam which has entered into the prism is reflected within the prism twice; and
the light beam reflected within the prism is emergent from the prism through the emergent surface.
32. The optical head device according to claim 31 , wherein:
the emergent surface has a light shutter layer having a minuscule opening which is smaller than the beam spot;
the light shutter layer except the minuscule opening prevents the light beam from passing through the emergent surface; and
a near field light effuses from the minuscule opening.
33. A prism for converging an incident light beam, comprising:
a first surface through which a light beam advancing along a first direction enters into the prism;
a second surface for reflecting the light beam which has entered into the prism through the first surface within the prism, the light beam reflected by the second surface advancing along a second direction different from the first direction;
a third surface for reflecting the light beam reflected by the second surface within the prism, the light beam reflected by the third surface advancing along a third direction different from the first and second directions; and
a fourth surface through which the light beam reflected by the third surface is emergent from the prism,
wherein, in vicinity of the fourth surface, at least one of the first, second and third surfaces converges the light beam and forms a beam spot.
34. The prism according to claim 33 , wherein:
the fourth surface has a light shutter layer having a minuscule opening which is smaller than the beam spot;
the light shutter layer except the minuscule opening prevents the light beam from passing through the fourth surface; and
a near field light effuses from the minuscule opening.
35. A prism for converging an incident light beam in vicinity of an emergent surface thereof, wherein:
a light beam advancing along a first direction enters into the prism, the first direction being substantially parallel to the emergent surface of the prism; and
the light beam which has entered into the prism is reflected within the prism twice.
36. The prism according to claim 35 , wherein:
the emergent surface has a light shutter layer having a minuscule opening which is smaller than the beam spot;
the light shutter layer except the minuscule opening prevents the light beam from passing through the emergent surface; and
a near field light effuses from the minuscule opening.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/863,341 US20050083827A1 (en) | 1998-11-27 | 2004-06-09 | Optical head and optical head device |
US11/489,484 US7489617B2 (en) | 1998-11-27 | 2006-07-20 | Optical head and optical head device |
Applications Claiming Priority (6)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP10-337671.PAT | 1998-11-27 | ||
JP10337671A JP2000163784A (en) | 1998-11-27 | 1998-11-27 | Optical head device |
JP11077460A JP2000276758A (en) | 1999-03-23 | 1999-03-23 | Optical head device |
JP11-77460.PAT | 1999-03-23 | ||
US09/448,467 US6831886B1 (en) | 1998-11-27 | 1999-11-24 | Optical head and optical head device |
US10/863,341 US20050083827A1 (en) | 1998-11-27 | 2004-06-09 | Optical head and optical head device |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/448,467 Division US6831886B1 (en) | 1998-11-27 | 1999-11-24 | Optical head and optical head device |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/489,484 Division US7489617B2 (en) | 1998-11-27 | 2006-07-20 | Optical head and optical head device |
Publications (1)
Publication Number | Publication Date |
---|---|
US20050083827A1 true US20050083827A1 (en) | 2005-04-21 |
Family
ID=33492314
Family Applications (3)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/448,467 Expired - Fee Related US6831886B1 (en) | 1998-11-27 | 1999-11-24 | Optical head and optical head device |
US10/863,341 Abandoned US20050083827A1 (en) | 1998-11-27 | 2004-06-09 | Optical head and optical head device |
US11/489,484 Expired - Fee Related US7489617B2 (en) | 1998-11-27 | 2006-07-20 | Optical head and optical head device |
Family Applications Before (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US09/448,467 Expired - Fee Related US6831886B1 (en) | 1998-11-27 | 1999-11-24 | Optical head and optical head device |
Family Applications After (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/489,484 Expired - Fee Related US7489617B2 (en) | 1998-11-27 | 2006-07-20 | Optical head and optical head device |
Country Status (1)
Country | Link |
---|---|
US (3) | US6831886B1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20020131357A1 (en) * | 2001-03-17 | 2002-09-19 | Lg Electronics Inc. | Lens for optical recording and reproducing system |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6831886B1 (en) * | 1998-11-27 | 2004-12-14 | Minolta Co., Ltd. | Optical head and optical head device |
JP2001176118A (en) * | 1999-12-15 | 2001-06-29 | Minolta Co Ltd | Optical head, recorder-reproducer and solid immersion lens |
JP3849523B2 (en) * | 2001-12-26 | 2006-11-22 | ティアック株式会社 | Optical pickup and optical disc apparatus |
TWI329869B (en) * | 2004-11-05 | 2010-09-01 | Hon Hai Prec Ind Co Ltd | Semiconductor laser assembly and optical pickup device using the same |
US7596072B2 (en) * | 2004-12-22 | 2009-09-29 | Seagate Technology Llc | Optical recording using a waveguide structure and a phase change medium |
KR100738078B1 (en) * | 2005-10-12 | 2007-07-12 | 삼성전자주식회사 | Near field light generating device and heat assisted magnetic recording head employing the same |
FR3023600B1 (en) * | 2014-07-11 | 2021-04-16 | Valeo Vision | LIGHTING MODULE OF A MOTOR VEHICLE |
Citations (20)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4475787A (en) * | 1981-02-06 | 1984-10-09 | Xerox Corporation | Single facet wobble free scanner |
US4656618A (en) * | 1983-08-26 | 1987-04-07 | Hitachi, Ltd. | Optical information recording and reproducing apparatus |
US4710911A (en) * | 1984-04-27 | 1987-12-01 | Matsushita Electric Industrial Co., Ltd. | Method for recording, reproducing and erasing optical information |
US4778984A (en) * | 1985-10-16 | 1988-10-18 | Canon Denshi Kabushiki Kaisha | Apparatus for detecting focus from astigmatism |
US4878720A (en) * | 1987-03-05 | 1989-11-07 | Optische Werke G. Rodenstock | Device for deflecting a bundle of light rays |
US5018865A (en) * | 1988-10-21 | 1991-05-28 | Ferrell Thomas L | Photon scanning tunneling microscopy |
US5253005A (en) * | 1988-05-18 | 1993-10-12 | Canon Kabushiki Kaisha | Small-sized camera |
US5289313A (en) * | 1988-09-28 | 1994-02-22 | Canon Kabushiki Kaisha | Optical head using semiconductor laser array as light source |
US5402269A (en) * | 1990-10-04 | 1995-03-28 | Asahi Kogaku Kogyo Kabushiki Kaisha | Compound prism |
US5748581A (en) * | 1996-02-15 | 1998-05-05 | Kim; Jin Tae | Optical head of an optical disc recording/reproducing apparatus having a polygonal prism |
US5859814A (en) * | 1996-10-18 | 1999-01-12 | The Board Of Trustees Of The Leland Stanford Junior University | Magneto-optic recording system and method |
US5874726A (en) * | 1995-10-10 | 1999-02-23 | Iowa State University Research Foundation | Probe-type near-field confocal having feedback for adjusting probe distance |
US6034797A (en) * | 1998-02-19 | 2000-03-07 | Industrial Technology Research Institute | Prism-type objective lens for the pickup head of an optical disc drive capable of driving two types of optical discs |
US6154326A (en) * | 1998-03-19 | 2000-11-28 | Fuji Xerox Co., Ltd. | Optical head, disk apparatus, method for manufacturing optical head, and optical element |
US6188132B1 (en) * | 1997-09-15 | 2001-02-13 | Industrial Technology Research Institute | Two-wavelength semiconductor laser diode package for use on the read/write head of an optical drive capable of reading different types of optical discs |
US6215756B1 (en) * | 1997-03-13 | 2001-04-10 | Hitachi, Ltd. | Optical head having two lasers of different wavelength and an objective lens made of one material having a rectangular groove shifting phase to decrease focused laser beam spot aberration for focusing laser beams on different thickness substrates |
US6275453B1 (en) * | 1997-11-06 | 2001-08-14 | Fuji Xerox Co., Ltd. | Optical head and optical disk apparatus |
US6320841B1 (en) * | 1998-10-07 | 2001-11-20 | Sony Corporation | Slider for optical head |
US6327238B1 (en) * | 1997-08-29 | 2001-12-04 | Matsushita Electric Industrial Co., Ltd. | Optical disk device |
US6377535B1 (en) * | 1998-07-06 | 2002-04-23 | Read-Rite Corporation | High numerical aperture optical focusing device having a conical incident facet and a parabolic reflector for use in data storage systems |
Family Cites Families (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS59187309A (en) | 1983-04-07 | 1984-10-24 | Mitsubishi Electric Corp | Light converging device |
JP2545239B2 (en) | 1987-09-19 | 1996-10-16 | 日立機電工業株式会社 | Control device in goods sorting device |
JPH0266733A (en) * | 1988-08-31 | 1990-03-06 | Asahi Optical Co Ltd | Optical system for optical information recording and reproducing device |
JPH02227840A (en) | 1989-03-01 | 1990-09-11 | Matsushita Electric Ind Co Ltd | Optical head device |
DE69023390T2 (en) * | 1989-05-16 | 1996-03-28 | Victor Company Of Japan | Electrostatic charge image recording medium and recording / playback device. |
JPH04370536A (en) | 1991-06-19 | 1992-12-22 | Nikon Corp | Optical recording/reproducing device |
US5311496A (en) * | 1992-11-13 | 1994-05-10 | Hyundai Electronics America | Achromatic expansion prism for magneto-optical drive |
US6016301A (en) * | 1996-04-01 | 2000-01-18 | Sony Corporation | Optical pickup device and optical disc reproducing apparatus |
JPH10162413A (en) | 1996-11-27 | 1998-06-19 | Matsushita Electric Ind Co Ltd | Optical head device |
JPH10199008A (en) | 1997-01-08 | 1998-07-31 | Nippon Hoso Kyokai <Nhk> | Multibeam optical head |
US6185056B1 (en) * | 1997-01-22 | 2001-02-06 | Matsushita Electric Industrial Co. Ltd. | Prism and manufacturing method thereof, optical beam shaping apparatus and optical head device utilizing such prism, and optical beam shaping method |
US6034823A (en) * | 1997-02-07 | 2000-03-07 | Olympus Optical Co., Ltd. | Decentered prism optical system |
US5883872A (en) | 1997-05-29 | 1999-03-16 | The Board Of Trustees Of The Leland Stanford Junior University | Near field magneto-optical recording system employing slit illumination |
US6130779A (en) * | 1998-07-06 | 2000-10-10 | Read-Rite Corporation | Near field magneto-optical head made using wafer processing techniques |
US6831886B1 (en) * | 1998-11-27 | 2004-12-14 | Minolta Co., Ltd. | Optical head and optical head device |
-
1999
- 1999-11-24 US US09/448,467 patent/US6831886B1/en not_active Expired - Fee Related
-
2004
- 2004-06-09 US US10/863,341 patent/US20050083827A1/en not_active Abandoned
-
2006
- 2006-07-20 US US11/489,484 patent/US7489617B2/en not_active Expired - Fee Related
Patent Citations (22)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4475787B1 (en) * | 1981-02-06 | 1995-04-11 | Xeros Corp | Single facet wobble free scanner. |
US4475787A (en) * | 1981-02-06 | 1984-10-09 | Xerox Corporation | Single facet wobble free scanner |
US4656618A (en) * | 1983-08-26 | 1987-04-07 | Hitachi, Ltd. | Optical information recording and reproducing apparatus |
US4710911A (en) * | 1984-04-27 | 1987-12-01 | Matsushita Electric Industrial Co., Ltd. | Method for recording, reproducing and erasing optical information |
US4778984A (en) * | 1985-10-16 | 1988-10-18 | Canon Denshi Kabushiki Kaisha | Apparatus for detecting focus from astigmatism |
US4878720A (en) * | 1987-03-05 | 1989-11-07 | Optische Werke G. Rodenstock | Device for deflecting a bundle of light rays |
US5253005A (en) * | 1988-05-18 | 1993-10-12 | Canon Kabushiki Kaisha | Small-sized camera |
US5289313A (en) * | 1988-09-28 | 1994-02-22 | Canon Kabushiki Kaisha | Optical head using semiconductor laser array as light source |
US5018865A (en) * | 1988-10-21 | 1991-05-28 | Ferrell Thomas L | Photon scanning tunneling microscopy |
US5402269A (en) * | 1990-10-04 | 1995-03-28 | Asahi Kogaku Kogyo Kabushiki Kaisha | Compound prism |
US5874726A (en) * | 1995-10-10 | 1999-02-23 | Iowa State University Research Foundation | Probe-type near-field confocal having feedback for adjusting probe distance |
US5748581A (en) * | 1996-02-15 | 1998-05-05 | Kim; Jin Tae | Optical head of an optical disc recording/reproducing apparatus having a polygonal prism |
US5859814A (en) * | 1996-10-18 | 1999-01-12 | The Board Of Trustees Of The Leland Stanford Junior University | Magneto-optic recording system and method |
US6215756B1 (en) * | 1997-03-13 | 2001-04-10 | Hitachi, Ltd. | Optical head having two lasers of different wavelength and an objective lens made of one material having a rectangular groove shifting phase to decrease focused laser beam spot aberration for focusing laser beams on different thickness substrates |
US6327238B1 (en) * | 1997-08-29 | 2001-12-04 | Matsushita Electric Industrial Co., Ltd. | Optical disk device |
US6188132B1 (en) * | 1997-09-15 | 2001-02-13 | Industrial Technology Research Institute | Two-wavelength semiconductor laser diode package for use on the read/write head of an optical drive capable of reading different types of optical discs |
US6275453B1 (en) * | 1997-11-06 | 2001-08-14 | Fuji Xerox Co., Ltd. | Optical head and optical disk apparatus |
US6034797A (en) * | 1998-02-19 | 2000-03-07 | Industrial Technology Research Institute | Prism-type objective lens for the pickup head of an optical disc drive capable of driving two types of optical discs |
US6154326A (en) * | 1998-03-19 | 2000-11-28 | Fuji Xerox Co., Ltd. | Optical head, disk apparatus, method for manufacturing optical head, and optical element |
US6320708B1 (en) * | 1998-03-19 | 2001-11-20 | Fuji Xerox Co., Ltd. | Optical head, disk apparatus, method for manufacturing optical head, and optical element |
US6377535B1 (en) * | 1998-07-06 | 2002-04-23 | Read-Rite Corporation | High numerical aperture optical focusing device having a conical incident facet and a parabolic reflector for use in data storage systems |
US6320841B1 (en) * | 1998-10-07 | 2001-11-20 | Sony Corporation | Slider for optical head |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20020131357A1 (en) * | 2001-03-17 | 2002-09-19 | Lg Electronics Inc. | Lens for optical recording and reproducing system |
US7239597B2 (en) * | 2001-03-17 | 2007-07-03 | Lg Electronics Inc. | Lens for optical recording and reproducing system |
Also Published As
Publication number | Publication date |
---|---|
US20060256697A1 (en) | 2006-11-16 |
US6831886B1 (en) | 2004-12-14 |
US7489617B2 (en) | 2009-02-10 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US6236514B1 (en) | Optical head device and near-field light emitting device | |
US7489617B2 (en) | Optical head and optical head device | |
KR100813943B1 (en) | Reflection type complex prism and optical pickup apparatus employing it | |
EP0814468B1 (en) | Optical recording and reproducing device | |
US7362693B2 (en) | Near-field optical storage medium and optical data storage system therefor | |
US6034797A (en) | Prism-type objective lens for the pickup head of an optical disc drive capable of driving two types of optical discs | |
US5646929A (en) | Optical pickup device | |
US5930434A (en) | Optical disc data storage system using optical waveguide | |
KR930000991B1 (en) | Objective lens for optical disk system and optical head using the same | |
US6298018B1 (en) | Optical recording and reproducing method optical recording and reproducing device, and optical recording medium | |
KR20010024437A (en) | Optical scanning device and optical apparatus for reading and/or writing information in an information plane provided with such a device | |
US5220553A (en) | Optical head | |
KR100393772B1 (en) | Optics for optical recording and reproducing system | |
KR100535341B1 (en) | Optical pickup apparatus | |
JP2000276758A (en) | Optical head device | |
JP2002050073A (en) | Floating head device and optical recording/reproducing device | |
KR100404084B1 (en) | Lens for optical recording and reproducing system | |
KR100366154B1 (en) | Optical pickup apparatus for read/write heads in high density optical storages | |
KR100388060B1 (en) | Optical data storage device using solid immersion lens and waveguide grating coupler | |
JP2000163784A (en) | Optical head device | |
JP2002048973A (en) | Solid immersion mirror and reproducing device | |
KR100438571B1 (en) | Lens for optical recording and reproducing system | |
JP2002117581A (en) | Surface readout type optical read-only medium and readout device | |
US20020167893A1 (en) | Multiple optical-recording apparatus using solid immersion lens | |
KR20040098107A (en) | Optical pickup apparatus |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |