• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:

    公开号:NL1010825A1
    申请号:NL1010825
    申请日:1998-12-16
    公开日:1999-06-17
    发明作者:Yang-Oh Choi
    申请人:Daewoo Electronics Co Ltd；
    IPC主号:
    专利说明:

    Field of the invention
    The invention relates to an optical recording system, and more particularly to an improved optical recording system having dimensions reduced by accommodating an integrated beam splitter for reading information signals outside of both thin and thick optical disks.
    Description of the prior art
    As is known, a short wavelength light source and a large numerical aperture (NA) are important optical requirements in optical recording heads for realizing the reproduction of data from a high-density optical storage medium. Therefore, preferably a lens with large numerical aperture, for example 0.6, is used in an optical head for use with a high density DVD (digital video disc) with a thickness of, for example, 0.6 mm. If such an optical head for reading the thin optical disc is used to read a conventional 1.2mm thick CD (compact disc), the spherical aberration caused by the difference in the thickness of the optical disk are corrected.
    One of the optical heads introduced to solve the problem is a dual focal optical head with a holographic optical element (HOE) shown in Fig. 1.
    Fig. 1 shows a conventional dual focus optical head 100 capable of reproducing information signals stored in optical disks of different thicknesses, as further described in
    Kanda and Hayashi, "Dual Focus Optical Head for 0.6mm and 1.2mm Disks", SPIE Vol. 2338 Optical Data Storage _H994] _Z283 · The dual focus optical head 100 includes: a light source 126 for generating a light beam, a beam splitter 106, a collimating lens 108, an HOE 110, an objective lens 112, a cylindrical lens 104, and a detector 102 provided with four photoelectric cells. A beam of light from the collimating lens 108 is split by the HOE 110 into refracted beams of the 0th order and the 1Bt order, which are then focused by the objective lens 112, the focal length of the refracted beam 128 of the 1st order being greater than that of the 0th order broken light beam 124.
    In the optical head 100, the refracted 0th order light beam 124 is used to display the information signal outside a recording surface 118 of a thin optical disk 116. The light beam emitted from the light source 126, for example, a laser diode, enters the HOE 110 inside via the beam splitter 106 and the collimating lens 108, wherein the beam splitter 106 partially reflects the light beam through a surface disposed therein and the collimating lens 108 makes the light beam from the beam splitter 106 parallel. The 0th order broken light beam 124 is focused on the recording surface 118 of thin optical disk 116 through the objective lens 112. The HOE 110 simply plays the role of a parallel plate for the 0th order broken light beam 124 of the parallel light beam. When the 0th order refracted light beam 124 is reflected by thin optical disk 116 to the HOE 110 through the objective lens 112, the HOE 110 also plays the role of a parallel plate. The 0th order refracted light beam 124, after passing through the collimating lens 108 and the beam splitter 106, becomes astigmatic as it passes through the cylindrical lens 104, causing the detector 102 to read the information signal outside the recording surface 118 of the thin optical disc 116. .
    Meanwhile, to display the information signal outside a recording surface 120 of a thick optical disk 122, the 1st order broken light beam 128 transmitted from the HOE 110 is used. In this case, the HOE 110 in combination with the objective lens 112 functions as a lens for focusing the refracted light beam 128 of the 1st order on the recording surface 120 of the thick optical disk 122. Therefore, the optical head 100 is for use with a thin optical disk 116 also capable of displaying the information signal outside the recording surface 120 of the thick optical disk 122.
    One of the drawbacks associated with the conventional optical head 100 described above is its optical efficiency resulting from the use of the HOE 110, using either the 0th order or 1st order refracted light beam in the reading information from a disc.
    Another problem present with the optical head 100 is its large size due to the use of the cylindrical lens 104 interposed between the optical detector 102 and the beam splitter 106, making the overall dimensions of the optical head 100 bulky .
    Summary of the invention
    It is therefore a primary object of the present invention to provide a reduced size optical pickup system and a simpler structure for reading a thin and a thick optical disk.
    According to one aspect of the present invention, there is provided an optical pick-up system, comprising: a light source; an optical detector; an objective lens, a beam splitter having a first and a second surface that are substantially parallel to each other, the first surface reflecting a first part of an incident light beam and transmitting a second part thereof, and the second surface reflecting an incident light beam which is transmitted through the first surface; and an optical device disposed between the objective lens and the beam splitter, having a first and a second electric switching region in a first or a second mode, the first region being transmissive in either the first or the second mode and the second region impermeable in the first mode and partially transmissive in the second mode.
    According to another aspect of the present invention, there is provided an optical pick-up system, comprising: a light source for a first light beam which is linearly polarized; an optical detector; an objective lens; an optical element having a surface reflecting the first incident light beam and a second light beam polarized perpendicular to the light beam transmission; and an optical device disposed between the objective lens and the beam splitter, having a first and a second region operating in a first or second electrical switching mode, the first region being transmissive in either the first or second mode and the second region not - is transmissive in the first mode and partially transmissive in the second mode.
    Brief description of the drawings
    The invention will now be explained in more detail by way of example with reference to the drawings and the description in the following.
    Fig. 1 shows a schematic of a known optical head; Fig. 2 shows a schematic of an optical recording system according to a first preferred embodiment of the present invention when a thick optical disk is loaded on a disk tray; Figures 3A and 3B illustrate the operation of the optical device as shown in Figure 2 when a predetermined voltage Vcc is not applied thereto; FIG. 4 is a schematic of an optical recording system according to the first preferred embodiment of the present invention when a thin optical disc is loaded on a disc tray; Figures 5A and 5B show explanatory diagrams for the operation of the optical device shown in Figure 4 when the voltage Vcc is applied thereto; FIG. 6 is a schematic diagram for an optical recording system according to a second preferred embodiment of the present invention; and FIG. 7 shows a schematic for an optical recording system according to a third preferred embodiment of the present invention.
    Detailed description of the preferred embodiments
    Referring to Figs. 2 to 7, optical recording systems are shown according to preferred embodiments of the present invention. It should be noted that the same parts that appear in Figures 2 to 7 are represented by the same reference numerals.
    In Fig. 2, there is schematically shown an optical pick-up system 200 operating in an electrical first and second switching mode according to a first preferred embodiment of the invention. The optical pick-up system 200 includes a light source 210, for example a semiconductor laser, for generating a light beam, which may be non-polarized or a first linearly polarized, for example, P-polarized light beam with a wavelength λ; a beam splitter 220 having a base 223 transparent to the light beam, and a first and second surfaces 222, 224; an optical device 230 / an objective lens 240; and an optical detector 260. The beam splitter 220 can be produced, for example, by depositing on the first surface 222 of a first material reflecting the first linearly polarized component, i.e., a P-polarized component of an incident light beam and the other linearly polarized component, that is, transmitting an S-polarized component of the light beam, and by coating a second material 224 on the second surface that reflects an incident light beam.
    For example, when a thick optical disk 252 of 1.2 mm thickness is loaded on a disk tray (not shown), the pickup system 200 operates in the first mode, with no voltage applied to the optical device 230. In the first mode is a central region 230-1 of the optical device 230 transmissive and serves as an aperture, while a peripheral region 230-2 becomes opaque or opaque to the beam from the beam splitter 220, as will be described in detail below.
    When the light beam emanating from the light source 210 falls on the beam splitter 220, its first surface 222 reflects the P-polarized component of the light beam as a first P-polarized light beam to the optical device 230. Part of the first P-polarized light beam incident on the central region 230-1 of the optical device 230 is converted into a first circularly polarized light beam after being transmitted therethrough. The first circularly polarized light beam is focused on a recording surface of the charged optical disk 252 through the objective lens 240 and is reflected back there to enter the central region 230-1. The remainder of the first P-polarized light beam is obstructed by the peripheral region 230-2 of the optical device 230.
    Therefore, the remainder represented by dashed lines in Fig. 2 is not used for reading information signals outside of the loaded optical disk 252.
    The portion of the first circularly polarized light beam entering the central region 230-1 is converted into a first S-polarized light beam upon passage therethrough. The first S-polarized light beam, after transmitting through the first surface 222 and the base 223 of the beam splitter 220, falls on the second surface 224 of the beam splitter 220. The second surface 224 of the beam splitter 220 reflects the first incident S-polarized light beam. optical detector 260.
    Referring to Fig. 3A, a cross-sectional view of the optical device 230 shown in Fig. 2 is shown. In the first mode, the Vcc is not applied to a lower and an upper transparent electrode 233, 235 of the optical device 230 by opening a switch 238. The optical device 230 includes a λ / 4 wafer 232, the lower and upper transparent electrodes 233, 235, which are made of, for example, ITO (indium tin oxide) or the like, a liquid crystal device 234 and a linear polarizer 236. In a preferred embodiment, the lower transparent electrode 233 is applied on top of the λ / 4 wafer 232 and the liquid crystal 234A, the upper transparent electrode 235 and the linear polarizer 236 are successively applied to a peripheral region of the lower transparent electrode 233. so that the peripheral area 230-2 corresponds to an area of the optical device 230 below the linear polarizer 236.
    When the first P-polarized light beam reflected from the first surface 222 of the beam splitter 220 enters the λ / 4 wafer 232, the phase of the first P-polarized light beam becomes λ / 4 making the first P-polarized light beam a circular polarized beam. The circularly polarized light beam is incident on the liquid crystal device 234. The liquid crystal device 234 is divided into a liquid crystal 234A in the form of an annular disk and an empty space 234B by an internal circle 234C of the liquid crystal 234A, as shown in FIG. 3B. The liquid crystal 234A is located between the lower and the upper transparent electrode 233, 235. The liquid crystal 234A is made of a birefringent crystal such as a nematic liquid crystal or the like. In a preferred embodiment, the thickness of the liquid crystal 234A is set to a value that changes the phase of the first P-polarized light beam by an odd multiple of λ / 4 when Vcc is not applied to the electrodes 233, 235.
    Therefore, part of the circularly polarized light beam incident on the liquid crystal 234A is converted into an S-polarized light beam upon transmission therethrough, while a remaining part of the circularly polarized light beam passing through the void space 234B of the liquid crystal device 234 is unchanged. remains, whereby the first circularly polarized light beam is obtained. Thereafter, the S-polarized light beam is blocked by the linear polarizer 236, so that the central region 230-1 corresponding to the void space 234B of the optical device 230 serves as the aperture shape to form a cross section of a light beam incident on the objective lens. 240. It is preferred that the linear polarizer 236 be in the form of an annular disk whose inner circle is equal to that of the liquid crystal 234A. The light beam passing through the central region 230-1 is incident on the objective lens 240 as the first linearly polarized light beam and focuses on the charged optical disk 252. The first circularly polarized light beam is then reflected by the charged optical disk 252 and is incident on the λ / 4 plate 232 after passing through the lower transparent electrode 233, whereby the first circularly polarized light beam is converted into the first S-polarized light beam. The first S-polarized light beam emerges from the optical device 230 and enters the beam splitter 220.
    For example, when a thin optical disk 250 having a thickness of 0.6 mm is loaded on the disk tray, the pickup system 200 operates in the second mode shown in Fig. 4. In the second mode, a predetermined voltage Vcc is applied to the optical device 230 so that the control panel and peripheral area 230-1, 230-2 are transmissive. Therefore, the entire region of the optical device 230 functions as an aperture shape to form a cross section of a light beam incident on the objective lens 240, as will be described in more detail below.
    When the light beam emanating from the light source 210 falls on the beam splitter 220, its first surface 222 reflects the first P-polarized light beam to the optical device 230. The portion of the first P-polarized light beam incident on the central region 230-1 of the optical device 230 shown in Fig. 4 behaves similarly to what is stated with respect to the first P-polarized light beam shown in Fig. 2. However, the remaining part of the first P-polarized light beam incident on the peripheral region 230-2 is different from that of the first P-polarized light beam, as shown in Fig. 2. It should be noted that the part and the remaining parts of the first linearly polarized light beam represented by dashed and solid lines, respectively, as shown in Fig. 4, are used to read information signals outside of the loaded disk 250.
    In the second mode, the remainder of the first linearly polarized light beam incident on the peripheral region 230-2 of the optical device 230 is also converted into a circularly polarized light beam and its P-polarized component enters the objective lens 240 after passage therethrough. . The P-polarized component of the circularly polarized light beam is focused on a recording surface of the charged optical disk 250 through the objective lens 240 and is reflected there back to the peripheral regions 230-2. The P-polarized component of the circularly polarized light beam entering the peripheral region 230-2 is converted into a second circularly polarized light beam upon transmission therethrough. An S-polarized light beam from the second circularly polarized light beam, after passing through the first surface 222 and the base 223 of the beam splitter 220, falls on the second surface 224 of the beam splitter 220. The second surface 224 of the beam splitter 220 reflects the S-polarized light component of the second circularly polarized light beam incident thereon to the optical detector 260 after passage through the first surface 222.
    With reference to fig. 5A and 5B are a cross-sectional view of the optical device 230 shown in FIG. 4 and a plan view of the liquid crystal 234A, respectively. In the second mode, the liquid crystal 234A serves as a material transparent to an incident light beam when the Vcc is applied to the electrodes 233, 235 by closing a switch 238.
    When the first P-polarized light beam reflected from the first surface 222 of the beam splitter 220 enters the λ / 4 wafer 232 that changes the phase of the first P-polarized light beam by λ / 4, the first P-polarized light beam becomes the circularly polarized beam. The circularly polarized light beam incident on the liquid crystal device 234. Therefore, the part of the circularly polarized light beam incident on the liquid crystal 234A remains unchanged after transmission therethrough. Thereafter, the P-polarized component of the circularly polarized light beam is transferred by the linear polarizer 236 to the objective lens 240 so that the entire region of the optical device 230 serves as the aperture shape to form a cross section of a light beam incident on the objective lens 240. The P-polarized component of the circularly polarized light beam is focused on the charged optical disk 250 through the objective lens 240 and is reflected there back to the linear polarizer 236.
    The P-polarized component of the circularly polarized light beam from the objective lens 240 is incident on the λ / 4 wafer 232 after passing through the linear polarizer 236, the upper transparent electrode 235, the liquid crystal 234A, and the lower transparent electrode 233 sequentially, thereby the P-polarized component is converted into the second circularly polarized light beam.
    Compared to the prior art optical head 100, the optical pick-up system 200 of the invention achieves improved optical efficiency by accommodating an optical device 230 capable of operating in an electrical first or second switching mode according to the charged optical disc, whereby the HOE 110 in the prior art optical head 100 can be omitted.
    Furthermore, the optical pick-up system 200 of the invention has reduced dimensions compared to the optical head 100 of the prior art. This is achieved by accommodating the beam splitter 220 thick enough to induce astigmatic aberration and the first and second surfaces 222, 224, the first surface 222 being formed by depositing a first material, which reflects one polarized component of an incident light beam and transmits the other polarized component, and wherein the second surface 224 of the beam splitter 220 is generated by forming a second material, which reflects the incident light beam, whereby the cylindrical lens 104 the prior art optical head 100 is omitted and the optical detector 260 is placed near the light source 210.
    In Fig. 6, there is shown as a variant a schematic for an optical pick-up system 300 comprising a beam splitter 320 in accordance with a second preferred embodiment of the present invention. The beam splitter 320 is similar to that of the first preferred embodiment, shown in Figs. 2 and 4 except that a portion 324 of a second surface 325 is coated with a material that reflects an incident light beam and a remaining portion is not coated about an incident incident beam through. The second surface 325 is divided in two by a line passing through a point where an optical axis intersects with the second surface 325, and the part 324 is part of the second surface 325 below the intersection. The optical axis is formed by connecting a central point of the objective lens 240 and a focal point thereof. The portion 324 serves as a knife edge, whereby the optical recording system 300 can also display information signals outside the recording surfaces of the optical disks 250, 252 using a knife edge method.
    Compared to the first embodiment of the present invention, the second embodiment is capable of reducing the thickness of the beam splitter 320. This is achieved by using the portion 324 of the second surface 325 as the blade edge. Therefore, the beam splitter 320 need not be thick enough to produce an astigmatic aberration. In addition, the remaining portion of the second surface 325 transmits a light beam incident thereon to the outside environment of the optical pick-up system 220, thereby reducing noise.
    Fig. 7 shows a schematic for a third preferred embodiment of an optical pick-up system 400, the third embodiment being the same as the first embodiment except that an optical element 420, for example, a cylindrical lens or a Fresnel lens with a rear surface 422 takes the place of the beam splitter 220 in the first embodiment, wherein the back surface 422 is coated with a material that reflects a P-polarized component of an incident light beam and transmits the other polarized component.
    In such an array, a light beam falls on the back surface 422 after being transmitted through the objective lens 240 and the optical device 230. The P-polarized component of the light beam is made astigmatic by the optical element 420 and then images on the optical detector 260, whereby the optical recording system 400 can also display information signals outside the recording surfaces of the optical disks 250, 252 using an astigmatic method, the optical detector 260 being positioned in a focus of the optical element 420.
    The third embodiment replaces the beam splitter 220 in the first embodiment of the present invention with the optical element 420, its rear surface 422 playing the role of the beam splitter 220 in the first embodiment.
    While the present invention has been described with reference to preferred embodiments, other modifications and variations are possible without exceeding the scope of the invention as set forth in the following claims.
    权利要求:
    Claims (20)
    [1]
    An optical recording system comprising: a light source; an optical detector; an objective lens; a beam splitter having a first and a second surface which are substantially parallel to each other, the first surface reflecting a first part of an incident light beam and transmitting a second part thereof and the second surface reflecting an incident light beam passing through the first surface is let through; and an optical device disposed between the objective lens and the beam splitter having a first and a second region operating in a first electric switching mode or a second electric switching mode, the first region being transmissive in either the first or the second mode and the second region is impermeable in the first mode and partially transmissive in the second mode.
    [2]
    Optical recording system according to claim 1, characterized in that the first part is a first linearly polarized light and the second part is a second linearly polarized light.
    [3]
    Optical recording system according to claim 2, characterized in that the first region of the optical device comprises means for converting a light beam from a first linearly polarized light into a light beam of a circularly polarized light and converting a light beam from a circularly polarized light in a beam of light from a second linearly polarized light.
    [4]
    Optical recording system according to claim 3, characterized in that the second region of the optical device comprises: means for converting a light beam from a first linearly polarized light into a light beam from a second linearly polarized light in the first mode and converting a light beam from a first linearly polarized light to a circularly polarized light in the second mode; and . means for transmitting a light beam from a first linearly polarized light and blocking a light beam from a second linearly polarized light.
    [5]
    Optical pick-up system according to claim 4, characterized in that the converter comprises: a λ / 4 wafer for converting a light beam from a first linearly polarized light into a circularly polarized light; and an optical element for changing the circularly polarized light into a beam of light from a second linearly polarized light in the first mode and transmitting the circularly polarized light in the second mode.
    [6]
    Optical pick-up system according to claim 5, characterized in that the optical element comprises: an upper and a lower transparent electrode; and a liquid crystal interposed between the electrodes serving as the y * wavelength plate when an electrical signal is not applied to the electrodes and serving as the wavelength plate transparent to an incident light beam when the electrical signal is applied to the electrodes, thereby the optical device can operate in the first electrical switching mode or the second electrical switching mode.
    [7]
    Optical recording system according to claim 6, characterized in that the liquid crystal is in the form of an annular disc.
    [8]
    Optical recording system according to claim 7, characterized in that the transmission is in the form of an annular disc, the inner circle of which has a radius which is the same as that of the liquid crystal.
    [9]
    Optical pick-up system according to claim 8, characterized in that the top transparent electrode is in the form of an annular disc, the inner circle of which has a radius that is the same as that of the liquid crystal.
    [10]
    Optical recording system according to claim 1, characterized in that if one of the optical disks is thinner than the other optical disk and is loaded on a disk tray, the optical device operates in the second mode.
    [11]
    Optical recording system according to claim 10, characterized in that when the other optical disk is loaded on the disk tray, the optical device operates in the first mode.
    [12]
    Optical pick-up system according to claim 1, characterized in that the beam splitter is thick enough to produce an astigmatic aberration.
    [13]
    Optical pick-up system according to claim 12, characterized in that the optical detector is arranged close to the light source.
    [14]
    Optical pick-up system according to claim 1, characterized in that only part of the second surface is coated with a material that reflects an incident light beam transmitted through the first surface and a remaining part of the second surface transmits a striking light beam into the outside of the optical pick-up system, reducing noise.
    [15]
    Optical pick-up system according to claim 14, characterized in that the second surface is divided into two parts by a line passing through a point where an optical axis intersects with the second surface, the optical axis being formed by connecting a central point of the objective lens and a focal point thereof.
    [16]
    An optical pick-up system, comprising: a light source for a first light beam that is linearly polarized; an optical detector; an objective lens; an optical element having a surface reflecting the first incident light beam and a second light beam perpendicularly polarized to the light beam transmission; and an optical device disposed between the objective lens and the beam splitter, a first and a second region operating in a first electric switching mode or a second electric switching mode, the first region being transmissive in either the first or the second mode and second region is impermeable in the first mode and partially transmissive in the second mode.
    [17]
    Optical recording system according to claim 16, characterized in that the first region of the optical device comprises means for converting the first light beam into a light beam of a circularly polarized light and converting a light beam into a circularly polarized light in the light beam second beam.
    [18]
    Optical recording system according to claim 17, characterized in that the second area of the optical device comprises: means for converting the first light beam into the second light beam in the first mode and converting a light beam of a first linearly polarized light in a circularly polarized light in the second mode; and means for transmitting the first light beam and blocking the second light beam.
    [19]
    Optical recording system according to claim 18, characterized in that the change means are arranged between the focusing member and the optical device.
    [20]
    Optical recording system according to claim 19, characterized in that the optical element is a cylindrical lens.
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    同族专利:
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    KR19990049997A|1999-07-05|
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    CN1220451A|1999-06-23|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US5331622A|1991-05-28|1994-07-19|Applied Magnetics Corporation|Compact optical head|
    US6026065A|1995-03-04|2000-02-15|Lg Electronics Inc.|Optical pick-up apparatus capable of reading data irrespective of disc type|
    JP2725632B2|1995-05-24|1998-03-11|日本電気株式会社|Optical head device|
    JP3476989B2|1995-08-04|2003-12-10|パイオニア株式会社|Optical pickup|
    US5787061A|1995-08-31|1998-07-28|Sanyo Electric Co., Ltd.|Optical disc recording reproducing apparatus recording/reproducing information to/from optical discs according to different standards|
    US5659533A|1996-07-23|1997-08-19|Sampo Corporation|Method of using a single pick-up head to read and store data on discs of different thicknesses and structure of a pick-up head apparatus therefor|
    法律状态:
    1999-08-02| AD1A| A request for search or an international type search has been filed|
    1999-12-01| RD2N| Patents in respect of which a decision has been taken or a report has been made (novelty report)|Effective date: 19991007 |
    2000-02-01| EDI| The registered patent application has been withdrawn|
    优先权:
    申请号 | 申请日 | 专利标题
    KR19970069019|1997-12-16|
    KR1019970069019A|KR19990049997A|1997-12-16|1997-12-16|Reflective Dual Focus Optical Pickup Device|
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