WO2007000682A1 - Unite de capteur optique utilisee dans un dispositif de lecture optique - Google Patents

Unite de capteur optique utilisee dans un dispositif de lecture optique Download PDF

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Publication number
WO2007000682A1
WO2007000682A1 PCT/IB2006/051962 IB2006051962W WO2007000682A1 WO 2007000682 A1 WO2007000682 A1 WO 2007000682A1 IB 2006051962 W IB2006051962 W IB 2006051962W WO 2007000682 A1 WO2007000682 A1 WO 2007000682A1
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WO
WIPO (PCT)
Prior art keywords
radiation beam
detection element
reflected
unit
optical pick
Prior art date
Application number
PCT/IB2006/051962
Other languages
English (en)
Inventor
Ronald R. Drenten
Lambertus J. M. Bouwman
Original Assignee
Arima Devices Corporation
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Arima Devices Corporation filed Critical Arima Devices Corporation
Publication of WO2007000682A1 publication Critical patent/WO2007000682A1/fr

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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
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • 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
    • G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
    • G11B7/126—Circuits, methods or arrangements for laser control or stabilisation
    • G11B7/1263—Power control during transducing, e.g. by monitoring

Definitions

  • Optical pick-up unit for use in an optical player
  • the present invention relates to an optical pick-up unit for scanning record carriers according to the preamble of claim 1.
  • the invention further concerns an optical player having such an optical pickup unit.
  • the invention further relates to a method for adjusting a beam power of a main radiation beam spot.
  • optical pick-up unit as a key component of an optical storage system, called optical player, comprising a drive unit, and an optical pick-up unit for scanning an optical record carrier
  • Optical record carriers are e.g. CDs (compact discs), DVDs, BDs (Blue ray disc) (digital versatile discs) and MOs (magneto optical discs). DVDs are available as DVD-ROMs (Read-Only-Memory), DVD-RAMs (Random Access Memory), DVD ⁇ R(W)s (Recordable, Rewritable) and so on.
  • scanning an optical record carrier means reading from and/or writing on an information layer in or on a recording surface of an optical record carrier, called record carrier in the following.
  • the optical record player comprises in general a turntable holding the record carrier and an optical pick-up unit.
  • the optical pick-up unit comprises optical components to generate and form a main radiation beam spot in order to scan the information onto or in an information layer of the record carrier.
  • a radiation beam source preferably a semi-conductor laser, emits at least one radiation beam with a specific wavelength and a specific radiation beam power.
  • An objective lens forms out of the radiation beam a radiation beam spot, called main radiation beam spot, wherein the crucial parameter for the quality of the scanning performance is the beam power of the main radiation beam spot, called main radiation beam spot power in the following.
  • the objective lens is held in an actuator, which is able to move and tilt the objective lens in a plane parallel to the recording surface of the record carrier.
  • the position of the radiation beam spot on the record carrier is controlled by the position of the objective lens.
  • the position of the objective lens is changed and controlled by the actuator and accompanying electric circuits.
  • the optical pick-up unit is mounted in the optical record player such that it can be shifted between an inner and an outer radius.
  • the information is stored in an area between the inner and the outer radius of the record carrier.
  • the optical pick-up unit is shifted not linearly, but in a stepped fashion.
  • the main radiation beam spot power is not constant due to the fact that the intensity of the emitted radiation beam has a Gaussian or close to Gaussian distribution. This is why the intensity profile of the radiation beam is not uniform when being incident onto the objective lens, resulting in a changed main radiation beam spot power dependent on the position of the objective lens.
  • Optical pick-up units which can control and change the beam power of the radiation beam spot are known, for instance from the US 2002/0080697 Al, the US 2003/0214893 Al and the US 2003/0072235 Al using different control parameters.
  • an optical pick-up unit is disclosed that comprises a detection element, called sensor, to detect the radiation beam intensity after having been reflected from the record carrier and adjust the radiation beam intensity of the radiation source according to the detected radiation beam intensity.
  • the drawback of that detection element is that only the total reflected radiation beam intensity is detectable.
  • the intensity of a radiation beam is the number of photons per time and area, which is the crucial parameter for the scanning of a record carrier, in particular the writing performance for a record carrier.
  • the reflected main radiation beam is formed from the main radiation beam spot by reflection from the record carrier.
  • the main radiation beam spot has generally spoken the necessary radiation beam power to perform the scanning of the record carrier.
  • the satellite radiation beam spots are of a weaker radiation beam power due to the generation mechanism by a diffraction element and serve as auxiliary radiation beams. With that a focus error signal and/or a tracking error signal can be estimated to keep the main radiation beam spot focused on a recording track of the record carrier.
  • the beam power of the main radiation beam spot is adjustable in dependency on the detected reflected main radiation beam and/or the reflected satellite radiation beams.
  • optical pick-up units used in high-speed optical players and/or slim- form factor optical players.
  • These new generation optical player have tolerances for the alignment of the optical components which are very narrow.
  • the use of the detected reflected radiation beams, reflected from the record carrier during scanning, results in a more constant quality of the recording.
  • the physical way of storing information on an information layer of the record carrier is different.
  • CD compact disc
  • DVD digital versatile disc
  • BD blue-ray disc
  • MO magnetic-optical disc
  • the physical way of storing information on an information layer of the record carrier is different.
  • optical discs CD, DVD and BD
  • a phase change or deformation is induced by the main radiation beam spot.
  • Different materials are used, wherein the different materials requires different beam powers of the main radiation beam spot for inducing the phase change.
  • a phase change from a crystalline phase in an amorphous phase is obtained by melting and subsequent cooling of the material on the information-recording layer of the record carrier.
  • the melting is achieved by the power of the radiation beam. Accordingly different radiation beam powers have to be achieved during writing and erasing information. If the beam power of the main radiation beam spot is fluctuating during the process of writing, a switching between the radiation beam power for writing and erasing can occur, resulting in a loss of information and/or a not perfect writing of information on the record carrier, which is called bad writing quality.
  • the writing is based on the Kerr effect at reflection.
  • the sign of the magnetization depends on the sign of the magnetization.
  • a layer of magnetic material, for instance GdTbFe, is heated with the radiation beam spot and during writing a magnetic field is applied such that the heated area changes the sign of the magnetization. Fluctuations of the main radiation beam spot power can here result in insufficient heating of the material, resulting in a not complete magnetization and with that in a bad writing quality.
  • the main radiation beam spot is adjustable in dependency on the detected intensity of the reflected satellite radiation beams.
  • the intensity of the main radiation beam spot shows variations during continuous scanning of an optical record carrier, which are caused by the fact that the intensity profile of the radiation beam entering the objective lens is not uniform. Therefore the intensity of the main radiation beam spot varies with time, resulting in bad writing performance. This is why it is advantageous to detect the intensity of the main radiation beam spot and use the obtained signal for an adjustment of the main radiation beam spot power.
  • the detection element comprises detection element components, each detection element component comprises at least two radiation sensitive surface areas, and each detection element component having at least two output signals.
  • a reflected main radiation beam and at least two reflected satellite radiation beam It is advantageous to form a reflected main radiation beam and at least two reflected satellite radiation beam and detect all three of them. Either the reflected satellite radiation beams can be used or both the reflected main radiation and the satellite radiation beams can be used for adjusting the radiation beam power and with that the main radiation beam spot power.
  • each detection element component With three detection element components the scanning main radiation beam and the scanning satellite radiation beams can be detected separately.
  • the radiation sensitive surface areas change the radiation into an electrical signal, using the photoelectric effect.
  • each detection element components delivers an electrical signal, which can be used in the means for controlling the radiation beam power.
  • the amount of radial movement of the actuator is detectably using the output signals of the detection element which comprises at least three detection element components.
  • the radial movement of the actuator is detectable measuring the reflected satellite radiation beams or the reflected main radiation beam.
  • the detection element is a three spot push-pull detector.
  • a three spot detector comprises three detection elements with at least two radiation sensitive areas.
  • the detection element for detecting the reflected main radiation beam is a quadrant detector and placed in between the detection elements for detecting the reflected satellite radiation beams.
  • the detection element for the reflected satellite radiation beams comprises in general two radiation sensitive areas.
  • the focus of the main radiation beam spot on the record carrier is controlled using the four radiation sensitive areas of the quadrant detector by calculating the difference of two sums of diagonally placed areas.
  • the intensity of the reflected main radiation beam is detected by the four radiation sensitive areas. This is called focus error signal. It is advantageous to use the output signals of these radiation sensitive areas, because these signals are available anyway in a three-radiation beam spot optical pick-up unit. No additional detection element components are needed.
  • the three spot push-pull detector is a standard component in an optical pick-up unit and therefore produced in high quantities and cheap in production.
  • the radial deviation, - being the position on the record carrier in the radial direction - is ascertainable using the output signals of the detection element components.
  • the relation of the beam power of the main radiation beam spot to the specific radial deviation of the actuator for a certain optical pick-up unit is known and can be stored in data storage elements, for instance in an electronic component like an EPROM.
  • the objective lens held in the actuator is moveable between an inner radius and an outer radius of the record carrier by shifting the actuator.
  • the actuator allows further to realize a tilt of the objective lens. This is in general performed to obtain a focused main radiation beam spot on the track of the record carrier.
  • the main radiation beam spot power is adjustable as a function of the radial deviation of the actuator, the radial deviation being the position of the actuator in the radial direction on the record carrier.
  • the main radiation beam spot power can be controlled and if necessary the radiation beam power emitted by the radiation source, preferably a semiconductor laser, can be adjusted.
  • the power can be increased in case the main radiation beam spot power is too low and can be decreased, in case the main radiation beam spot power is too high.
  • a direct control of the main radiation beam spot power can be performed.
  • the output signals of the detection elements measuring the reflected satellite radiation beams are usable to determine the amount of adjustment needed for the beam power of the main radiation beam spot.
  • the reflected satellite radiation beams have less intensity than the reflected main radiation beam. Additionally they are detected anyway to perform the focus error signal and/or the tracking error signal in most of the optical pick-p units with a three-beam push pull set-up.
  • the optical pick-up unit comprises at least one grating element to generate the main radiation beam and the at least two satellite radiation beams.
  • control unit and the apparatus for controlling and changing the radiation beam power of the main radiation beam are realizable in a single unit.
  • a single unit is advantageous, because it is space saving. This is important because the optical pick-up units are small in dimensions. Additionally, it allows to realize the shortest possible connection elements like electrical cables.
  • the radiation beam power is adjustable in order to keep the main radiation beam spot power nearly constant.
  • the object is achieved according to the invention, in that a main radiation beam spot and at least two satellite beam spots are formed from the at least one radiation beam, in particular by using a grating element, the main radiation beam and at least two satellite radiation beams are directed onto an information layer of at least one type of record carriers to form a main radiation beam spot and at least two satellite beam spots on that information layer, a reflected main radiation beam and the at least two reflected satellite radiation beams are detected separately after being reflected from the record carrier and the main radiation beam spot power is changed in dependency on the detected reflected main radiation beam and/or the detected reflected satellite radiation beams and/or in dependency on the beam power of the reflected satellite radiation beams.
  • the radial deviation that is the radial position on the record carrier on the actuator is determined in a control unit using the output signals of the detection element components.
  • the direct measurement of the radial deviation of the actuator is advantageous, because with that the position in the radial direction on the record carrier is estimated.
  • the radial position is changed during the process of writing and reading in formation on the record carrier. Therefore it is advantageous to estimate the position.
  • the beam power that is the intensity of the radiation beam is changed due to the fact that the radiation cone of the radiation beam is of a Gaussian shape. This results in a non-flat intensity profile, but an intensity variation across the diameter of the radiation beam cone.
  • the radial position of the objective lens is achieved by moving and tilting the objective lens in order to form the radiation beam spots onto the information-recording layer of the record carrier.
  • a tilt objective lens leads to a main radiation beam spot having an angle not equal 90° with the surface of the record carrier.
  • the intensity of the radiation beam on the record carrier - the beam power- is then less than the maximal intensity of the radiation beam, because either the right or the left side of the radiation beam cone is incident on the surface of the record carrier.
  • the fluctuations of the main radiation beam spot power are dependent on the radial position of the actuator and with that from a radial deviation. Therefore it is advantageous to estimate the main radiation beam spot power directly from the radial deviation of the actuator.
  • the relationship (dependency) can be stored in a memory of the control unit and used to determine the main radiation beam spot power from the radial deviation of the actuator.
  • the detection element component which is positioned in the middle of the two outer detection element components is used to detect the reflected main radiation beam and the two outer detection element components are used to detect the reflected satellite radiation beams. With that, the reflected main radiation beam and the reflected satellite radiation beams can be detected separately.
  • each detection element component delivering at least two output signals.
  • Detection element components with two radiation sensitive suria.ce areas called area, are standard detectors in an optical pick-up unit. The radiation beam incident on the area is converted into an electric signal by the photoelectric effect. The signal is than used as input signal of a control unit. Two areas of each detection element component can give more accurate information about the radial position of the main radiation beam spot.
  • the beam power of the main radiation beam spot is estimated in the control unit using the detected reflected main radiation beam and/or the detected reflected satellite radiation beams.
  • a control unit is any electric circuit able to process electric signals and perform a logical interconnection of the between them. At least one output signal is in general provided to control another means for controlling components like a radiation beam source.
  • a radial deviation of an actuator of the objective lens is estimated by the control unit calculating the difference between two sensitive areas of each detection element component.
  • the feet-forward method To use the radial deviation of the actuator to change the beam power of the radiation beam is called the feet-forward method.
  • a three spot push-pull detection element is used.
  • Three spot push pull detection elements are standard components in optical pick-up units of optical players. Therefore no additional detection elements are needed, which is cost saving.
  • a calibration information for a specific type of pick-up unit is stored in the control unit.
  • a calibration of the main radiation beam spot power is necessary for each optical pick-up unit, because the requirements on alignment between the radiation source for instance and the objective lens and the record carrier are dependant on the specific operation data. That means for an optical pick-up unit being designed for scanning different types of record carriers, other requirements are needed than for an optical pick-up unit which is designed for scanning only CDs. Therefore a calibration in advance is necessary.
  • Fig. 1 is a schematic view of a record and an optical pick-up unit
  • Fig. 2 is a diagram of the relation between the radial deviation of the actuator and the time of scanning (a) and the variation of the main radiation beam spot power (b);
  • Fig. 3 is a schematic diagram of an optical pick-up unit, which comprises a three-push pull detection element used for adjusting the beam power of the main radiation beam spot;
  • Fig. 4 is a schematic view of a set-up of a detection element, comprising three detection element components, each having two radiation sensitive surfaces;
  • Fig. 5 shows embodiments of the detection element.
  • Fig. 1 shows a schematic view of an optical record player 10 comprising an optical pick-up unit (OPU) 12 and a record carrier 14.
  • the record carrier 14 is held by a turntable 16, which turns the record carrier 14 during scanning, recording (writing) and reading.
  • Different types of record carriers 14 are suitable to be scanned in the optical record player 10. That are CDs (compact discs), DVDs (digital versatile discs), BDs (blue ray discs) and MOs (magneto optical discs).
  • the record carrier has typically a diameter of 12 cm and information to be scanned (read or write) is stored on or in the information layer not shown here, of an information surface 18 of the record carrier 14 in a train of pits on a track or a groove of the record carrier 14.
  • the tracks are made from a dye or a phase-change material and writing the pits is realized by modifying the dye or the phase of the phase change material by the radiation beam.
  • the tracks and the grooves are in general arranged radially on the record carrier 14. The tracks and grooves as well as the train of pits are not shown in figure 1.
  • the different types of record carriers 14 are characterized by different information densities (pits per cm 2 ).
  • the information density of a record carrier 14 is determined by a specific distance between tracks and/or grooves. Record carriers with high information density have a small distance between adjacent tracks and/or grooves and with that comprise a greater number of tracks and/or grooves.
  • Some kind of record carriers 14 have one information-carrying layer, other comprises two information-carrying layers.
  • an optical player is designed to scan different types of record carriers 14. This results in different requirements of the alignment accuracy of the optical components of the optical pick-up unit.
  • the optical pick-up unit 12 comprises at least one radiation source 20, emitting a radiation beam 22 having at least one wavelength ⁇ and a radiation beam power.
  • Optical components 24 direct the radiation beam 22 onto the track of the information surface 18 of the record carrier 14.
  • An objective lens 28 is arranged in front of the information surface 18 of the record carrier 14 and forms a radiation beam spot 26 out of the radiation beam 22.
  • the radiation beam spot 26 writes the information into the information-carrying surface of the record carrier 14.
  • the objective lens 26 is held in an actuator 30.
  • the actuator 30 moves the objective lens 28 in a radial direction x, indicated with an arrow 32 in order to direct the radiation beam spot 26 on different tracks arranged on different radii on the record carrier 14.
  • the actuator 30 is as well able to tilt the objective lens 28, if necessary.
  • the radial deviation is therefore the position in radial direction on the record carrier, wherein specific positions belong to specific tracks and/or grooves.
  • the optical pickup unit 12 is shifted in the direction x in a stepped fashion. This is shown in Fig, 2.
  • the main radiation beam spot power is not constant during this shift due to the fact that the radiation beam is not uniform, but has a Gaussian profile.
  • a Gaussian profile means that the radiation beam incident on the objective lens 28 has a distribution of the power, also known as intensity cone, of the radiation beam across a plane facing the objective lens 28.
  • the maximum intensity is in the middle of the radiation beam and lower intensity is on the right and the left side of the radiation beam cone.
  • the radiation beam power incident on the objective lens 28 will be different compared to the case the centers do coincide. That means that radiation beam spot 26 with a different power is focused onto the record carrier 14. This results in fluctuations of the radiation beam spot power p sc of the radiation beam spot 26, scanning the record carrier 14 even if the radiation beam 22 emitted from the radiation source 20 is kept constant. These fluctuations are schematically shown also in figure 2.
  • the radiation beam power is adjusted in order to keep the beam power of the main radiation beam spot constant, which performs the scanning of the record carrier 14.
  • Fig. 2 shows a two dimensional diagram.
  • the distance x of a shift of the actuator in the optical pick-up unit 12 is drawn on the y-axis of a two dimensional diagram and time t on the x-axis (a). That means x is depicted as function oft. It can be seen that the time t is divided in distinct time intervals t ls t 2 , t 3 indicating periods between which the optical pick-up unit 12 is shifted.
  • the distance x is arranged across the radius of the record carrier 14. Because the shift of the objective lens 28 is performed by the actuator 30, it is obvious that a shift of the optical pick-up unit 12 causes a deviation of the actuator from a zero position, when the optical pick-up unit is shifted in order to follow the position of a track on the record carrier 14. Therefore the wording radial deviations is used.
  • Radial means between an inner radius and an outer radius of the information carrying part of the record carrier 14A.
  • a typical value for the distance x, is 0.2 mm for an optical player being able to scan DVDs and CDs.
  • the difference between the main radiation beam spot power is in this case about 3 % of the maximum radiation beam power depending on the design of the optical pick-up unit.
  • Fig. 3 shows a schematic view of an example of an optical pick-up unit 12.
  • the optical pick-up unit comprises the radiation source 20, typically a semiconductor laser. Radiation sources 20 emitting the radiation beam 22, where in the radiation beam may have different wavelengths, typically in use are: 430 nm, 635 nm, 650 nm, 780 nm for scanning the different types of record carriers 14.
  • the embodiment includes as well optical pick-up units 12 comprising one or two or even three radiation sources 20. Also optical pick-up units comprising a dual wavelength radiation source is included in the embodiments according to the present invention. The invention is not limited to the mentioned specific embodiments in this example.
  • the optical pick-up unit 12 according to the present invention comprises further a grating element 34 that from the radiation beam 22 forms a main radiation beam 36 and at least two satellite radiation beams, not shown here.
  • the main radiation beam 36 and the satellite radiation beams pass a beam-splitter element 38, typically a beam splitter, an optical lens 40 and is incident on a folding mirror 42, where the main radiation beam 36 and the satellite radiation beams are folded by 90 ° and is directed onto the objective lens 28, which forms a main radiation beam spot 46 as well as satellite radiation beam spots onto an information recording layer 18 of the record carrier 14.
  • the satellite radiation beam spots are not shown here.
  • the main radiation beam spot 46 and the two-satellite radiation beam spots are important for the tracking mechanism of the optical pick-up unit 12 and will be described later.
  • the main radiation beam spot 46 and the satellite radiation beam spots are reflected by the record carrier 14.
  • the reflected radiation beam spots are called reflected radiation beam spots: the reflected main radiation beam 47 and the reflected satellite beams. They are directed passing the folding mirror 42 and the optical component 38, in particular the beam-splitter element onto a detection element 48.
  • an astigmatic lens is included to make possible an astigmatic focusing counted method.
  • the main radiation beam spot 46 performs the reading/writing of the information from the information-carrying layer of the record carrier 14.
  • the main radiation beam spot 46 is reflected from the record carrier forming the reflected main radiation beam 47, which can be detected by the detection element 48.
  • the main radiation beam spot 46 itself is influenced by the writing/reading process. Therefore the beam power of the main radiation beam spot 46 is in general different from the beam power of the reflected main radiation beam 47.
  • the reflected satellite radiation beams have the same beam power as the satellite radiation beam spots, incident on the record carrier 14.
  • the detection element 48 typically comprises at least three detection element components 52, 54, 56, which are shown in more details in Fig. 4.
  • the detection element component 52 detects the main radiation beam spot 46 and the detection element components 54 and 56 detect the satellite radiation beam spots. That means the detection element has at least three output signals, which are directed to a control unit, not shown here.
  • the control unit is connected to means for controlling the radiation beam power.
  • every radiation source 20 comprises means for controlling and changing the radiation beam power.
  • the means for controlling and change the radiation beam power obtains an input signal from the control unit, which specify the value of the radiation beam power. This input signal for the means for controlling and change of the radiation beam power is calculated by the control unit according to the input signal of the detection element components 52, 54, 56.
  • the output signal can be obtained in two different ways: Firstly, out of the reflected main radiation beam spot 47 and the reflected satellite beam spots a radial deviation of the actuator 30 is ascertainable. This is called the Feed-forward method. From the radial deviation of the actuator the amount of change of the radiation beam power is than directed to the output signal of the control unit and given to the means for controlling and changing the radiation beam power.
  • the power of the reflected satellite radiation beam spots can be detected by the detection element components 54 and 56.
  • the output signals of the detection element components 54 and 56 give information about the beam power of the reflected satellite radiation beam spots.
  • the reflected satellite radiation beam spots are not influenced by the writing/reading process of the record carrier 14.
  • the beam power of the reflected satellite radiation beam spots reflect the beam power being incident on the information-carrying layer of the record carrier 14.
  • the main radiation beam spot is influenced by the writing/reading process itself and therefore the beam power of the reflected main radiation beam does not reflect the beam power which is relevant for the writing/reading process itself.
  • Fig. 4 an example for an embodiment of the detection element 48 is shown, comprising three detection element components 52, 54 and 56.
  • Each of the detection element components comprises at least two radiation sensitive surface areas, transforming the reflected main radiation beam incident on this surface area into an electric signal.
  • the areas of the detection element components 52, 54 and 56 are depicted as: a (62), b (64), c (58), d (60) and e (66), f (68), respectively.
  • Areas a, c and e are the left half areas of the detection element components 52, 54, 56 and areas b, d, f are the right half areas of the detection element components 52, 54 and 56.
  • Any of the detection element components 52, 54, 56 can also be a so-called four quadrant detector having four separated radiation sensitive areas, resulting in four separate electrical signals.
  • the radial position x is for example estimated using the detected radiation beam spot intensity from the detection element components 52, 54, 56 with the areas a, b, c, e, d, f by the following formula:
  • y is the grading ratio, which is the power ratio of the main radiation beam spot with respect for the satellite radiation beam spots.
  • the intensity of the main radiation beam spot, the main radiation beam power can be estimated using the reflected radiation beams, detected by the detection element components 52, 54 and/or 56 or by the means for detecting the intensity of the main radiation beam spot directly.
  • the output signal of the detection element components or the means is directed to the means for controlling and changing the radiation beam power of the at least one radiation beam 22 in order to adjust the beam power of the main radiation beam spot.
  • FIG. 5 further embodiments of the detection element 48, comprising at least three detection element components 52, 54, 56 are shown.
  • the left depicted detection element 48 has a four-quadrant detection element component 52, comprising four radiation sensitive areas.
  • the detection element 48 shown in the right part of Fig. 5 has four quadrant detection element components 52, 54 and 56. It is advantageous to use four radiation sensitive detection areas to obtain more detailed information on the reflected main radiation beam and on the reflected satellite radiation beams.
  • Fig. 5 also a fourth embodiment of the detection element 48 comprising at least three detection element components 52, 54 and 56 is shown.
  • the radiation sensitive areas are arranged in a different way, than in the above-discussed embodiments.
  • Areas a, c, e are shown in the upper areas of the detection element components 52, 54, 56 and areas b, d, f are the bottom areas of the detection element components 52, 54 and 56.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)
  • Optical Recording Or Reproduction (AREA)

Abstract

L'invention concerne une unité de capteur optique permettant le balayage d'un support (14) d'enregistrement à l'aide d'un faisceau de rayonnement focalisé, désigné sous le nom de point (46) de faisceau de rayonnement principal d'une puissance correspondante, et comprenant au moins une source (20) de rayonnement émettant au moins un faisceau (22) de rayonnement, un objectif (28) amovible par un dispositif (30) de commande, un élément (48) de détection destiné à détecter un faisceau de rayonnement réfléchi, un moyen de commande et de changement de la puissance dudit faisceau (22) de rayonnement émis par ladite source (20) de rayonnement, l'unité de capteur optique (12) étant amovible entre un rayon interne et un rayon externe du support (14) d'enregistrement au cours du balayage du support (14) d'enregistrement. L'élément (48) de détection comprend au moins trois composants (52, 54, 56) de détection d'un faisceau (47) de rayonnement principal réfléchi, et/ou d'au moins deux faisceaux de rayonnement satellite réfléchis.
PCT/IB2006/051962 2005-06-27 2006-06-19 Unite de capteur optique utilisee dans un dispositif de lecture optique WO2007000682A1 (fr)

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EP05105694.3 2005-06-27
EP05105694 2005-06-27

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2169675A2 (fr) 2008-09-30 2010-03-31 Hitachi Consumer Electronics Co. Ltd. Support d'enregistrement d'informations et appareil de reproduction/enregistrement optique

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0512625A2 (fr) * 1991-05-10 1992-11-11 Koninklijke Philips Electronics N.V. Dispositif de balayage optique
WO1998033177A2 (fr) * 1997-01-29 1998-07-30 Koninklijke Philips Electronics N.V. Procede et dispositif pour enregistrer et/ou reproduire des informations
US20020080697A1 (en) * 2000-12-22 2002-06-27 Jun Akiyama Optical disk apparatus and method for adjusting optical disk apparatus laser power
WO2004059625A1 (fr) * 2002-12-30 2004-07-15 Koninklijke Philips Electronics N.V. Dispositif de lecture de disques optiques

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0512625A2 (fr) * 1991-05-10 1992-11-11 Koninklijke Philips Electronics N.V. Dispositif de balayage optique
WO1998033177A2 (fr) * 1997-01-29 1998-07-30 Koninklijke Philips Electronics N.V. Procede et dispositif pour enregistrer et/ou reproduire des informations
US20020080697A1 (en) * 2000-12-22 2002-06-27 Jun Akiyama Optical disk apparatus and method for adjusting optical disk apparatus laser power
WO2004059625A1 (fr) * 2002-12-30 2004-07-15 Koninklijke Philips Electronics N.V. Dispositif de lecture de disques optiques

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2169675A2 (fr) 2008-09-30 2010-03-31 Hitachi Consumer Electronics Co. Ltd. Support d'enregistrement d'informations et appareil de reproduction/enregistrement optique
EP2169675A3 (fr) * 2008-09-30 2010-06-09 Hitachi Consumer Electronics Co. Ltd. Support d'enregistrement d'informations et appareil de reproduction/enregistrement optique
US8102750B2 (en) 2008-09-30 2012-01-24 Hitachi Consumer Electronics Co., Ltd Super resolution producing apparatus capable of adjusting reproduction power

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