JP2008217982A - Optical head and optical recording medium driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain good characteristics and to ensure an exact output power control of a light source by making the required variation of an output power of the light source smaller at the recording and reproducing operation or in relation to respective recording surfaces of optical recording media of different kind and multilayered optical recording media and by using the light source of smaller optical output rating having good productivity. <P>SOLUTION: An optical coupling efficiency relating to the luminous flux with which the optical recording medium 102 is irradiated from an optical head 104, is controlled by optical coupling efficiency variable elements 214, 215 according to the kind of optical recording medium 102 and the recording surface and operation mode of the multilayered optical recording medium to change the power of the luminous flux with which the optical recording medium 102 is irradiated to a large extent without excessively increasing the variation of the output power of the light source 212. Also, the optical coupling efficiency is fixed regardless of the operation mode at a temperature lower than the prescribed temperature. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical head that records and / or reproduces various information with respect to an optical recording medium, and an optical recording medium driving apparatus that includes such an optical head.

  Conventionally, as an optical recording medium represented by an optical disk, a pit or the like is formed in advance on a disk substrate and used exclusively for reproduction, phase change along a groove structure formed on the disk substrate, or magneto-optical There have been proposed recording and playback using recording or the like.

  Among these, in an optical recording medium driving apparatus such as an optical disk apparatus using an optical disk capable of recording and reproduction, a semiconductor laser element having a relatively large maximum emitted light amount (maximum optical output rating) is generally used as a light source of an optical head. It is normal. On the other hand, in a reproduction-only device, a light source with a large maximum rating is usually not necessary. This is due to the following reasons.

  (1) In general, in a semiconductor laser element, when the light emission output is small, it is difficult to obtain stable oscillation, and laser noise increases. Therefore, in order to ensure a CNR (Carrier to Noise Ratio) at the time of information reproduction, it is necessary to set the light output of the laser to a value higher than a certain level. This value is usually about 2 mW to 5 mW.

  (2) In a recordable optical recording medium, it is used to perform recording by using a temperature rise of a recording layer or the like caused by condensing a light beam on a recording surface of the optical recording medium. In this case, there are two conditions: “the recorded signal does not deteriorate even when irradiated with a light beam of reproduction power” and “stable recording can be performed using the light beam of recording power”. If both are to be satisfied, it is necessary to ensure a predetermined output ratio or more between the optical power during reproduction and the optical power during recording. Usually, the maximum power of the recording light beam is about 5 to 20 times the power of the reproduction light beam. Further, when recording at a higher speed than the standard speed (when rotating the optical disk faster than the standard speed), a larger output ratio is required.

  For these two reasons, the light output maximum rating of the light source used in the optical head corresponding to recording and reproduction, and the light source used in the optical head performing recording and / or reproduction on a plurality of types of optical recording media is Usually, an optical recording medium (for example, a so-called “CD-R / RW” type optical disc) that records at a high speed of about 20 mW to 50 mW and about eight times the standard speed is about 100 mW.

Japanese Patent Laid-Open No. 10-124919

  By the way, as described above, a light source having a large maximum light output rating is not only difficult to realize, but also has problems such as increased power consumption in the light source. In addition, if such a light source is used with a reduced light output, such as during reproduction, laser noise will increase and good reproduction characteristics will not be obtained.

  On the other hand, in the reproduction-only “DVD” (“DVD-ROM” or “DVD-Video”) (registered trademark), an optical disc having two recording surfaces has already been put into practical use. In recent years, an optical disc having a multi-layered recording surface such as two layers or four layers has been proposed as an optical disc of a type capable of recording and reproduction.

  These optical recording media having multiple recording surfaces require about 1.5 to 2 times or more recording optical power and reproducing optical power compared to optical recording media having only one recording surface. It becomes.

  Therefore, in an optical recording medium driving apparatus that supports both an optical recording medium having a single recording surface and an optical recording medium having a multi-layer recording surface, the maximum power of a recording light beam for an optical recording medium having a multi-layer recording surface is The ratio (magnification) with respect to the power of the reproducing light beam with respect to the optical recording medium having one recording surface is the reproducing light flux of the power of the recording light beam in the optical recording medium driving apparatus that handles only the optical recording medium having the one recording surface. It becomes about twice the ratio to the power of.

  Further, even when the linear velocity of the optical recording medium with respect to the light beam is different, the required power of the recording light beam and the power of the reproducing light beam are different. That is, when the linear velocity of the optical recording medium with respect to the light beam increases, a recording light beam and a reproduction light beam with higher power are required.

  As described above, when the recording capacity of the optical recording medium is increased and the recording capacity is further increased in the future, the light source is required to have a wider dynamic range of light output.

  Therefore, in view of the above situation, the present invention reduces the optical power ratio of the light source during recording (in recording mode) and during reproduction (in reproduction mode), and sufficiently reduces laser noise during reproduction. It is an object of the present invention to provide an optical head and an optical recording medium driving apparatus that can obtain good recording and reproducing characteristics even when a light source having a small maximum optical output rating with good manufacturability is used.

  Furthermore, the present invention provides a plurality of types of optical recording media, multilayer optical recording media having different optical powers for optimum recording and / or reproduction, or optical recording media having a recording surface divided into a plurality of recording areas. Even for various types of optical recording media, the laser noise during reproduction is made sufficiently small, and even if a light source with a small maximum output power rating with good manufacturability is used, each type of optical recording medium and multilayer optical recording medium It is an object of the present invention to provide an optical head and an optical recording medium driving device that can obtain good recording and / or reproducing characteristics for each recording surface and each of a plurality of recording areas on the recording surface.

  In order to solve the above-described problems, an optical head according to the present invention includes a light source, a light condensing unit that condenses and irradiates a light beam emitted from the light source on an optical recording medium, and light emitted from the light source. A light separating means for separating the optical path of the beam from the optical path of the reflected light beam reflected by the optical recording medium and passing through the light collecting means; and a light detecting means for receiving the reflected light beam passed through the light separating means. An optical coupling efficiency variable means provided between the light source and the light condensing means for changing the optical coupling efficiency, which is a ratio of the amount of light collected on the optical recording medium to the total amount of light emitted from the light source. ing.

  The optical head further controls the optical coupling efficiency varying means of the optical coupling efficiency varying means based on the temperature sensor disposed in the vicinity of the light source or the optical coupling efficiency varying means and the temperature detected by the temperature sensor. Control means.

  In this optical head, when the temperature detected by the temperature sensor is equal to or higher than the predetermined temperature, the control unit controls the optical coupling efficiency variable unit to change the optical coupling efficiency according to the operation mode. When the temperature detected by the temperature sensor is lower than a predetermined temperature, the optical coupling efficiency variable means is controlled to fix the optical coupling efficiency regardless of the operation mode.

  In order to solve the above-described problem, an optical recording medium driving apparatus to which the present invention is applied includes a light source, a light condensing unit that condenses and irradiates the optical recording medium with a light beam emitted from the light source, A light separating means for separating the optical path of the light beam emitted from the light source and the optical path of the reflected light beam reflected by the optical recording medium and passing through the light collecting means; and the light passing through the light separating means. The ratio of the amount of light collected on the optical recording medium with respect to the total amount of light emitted between the light detection means for receiving the reflected light beam, the light source and the light condensing means. The optical coupling efficiency variable means for changing the optical coupling efficiency, the light source, a temperature sensor arranged in the vicinity of the optical coupling efficiency variable means, and the optical coupling efficiency based on the temperature detected by the temperature sensor. Variable means An optical head having a Gosuru control means, and a driving means for rotationally driving the optical recording medium.

  In this optical recording medium driving device, the control means controls the optical coupling efficiency varying means when the temperature detected by the temperature sensor is equal to or higher than a predetermined temperature, and controls the optical coupling efficiency according to the operation mode. When the temperature detected by the temperature sensor is lower than a predetermined temperature, the optical coupling efficiency is controlled regardless of the operation mode by controlling the optical coupling efficiency variable means.

  In the optical head and the optical recording medium driving apparatus according to the present invention, the power ratio of the light source in the recording mode and the reproduction mode can be reduced to sufficiently reduce the laser noise during reproduction, and optimum recording and / or reproduction is possible. Laser noise during playback can also be applied to multiple types of optical recording media, such as multiple types of optical recording media with different optical power, multilayer optical recording media, or optical recording media whose recording surface is divided into multiple recording areas. Can be made sufficiently small.

  In the optical head and the optical recording medium driving apparatus according to the present invention, when the temperature detected by the temperature sensor is lower than the predetermined temperature, the optical coupling efficiency is fixed regardless of the operation mode. There is no problem that the response speed of the variable means becomes slow, and even at such low temperatures, even when a semiconductor laser element is used as the light source, the generation of laser noise is small, so the reproduction characteristics are affected. I do not receive it.

  Embodiments of an optical head and an optical recording medium driving apparatus according to the present invention will be described below in detail with reference to the drawings. The embodiments described below are preferred specific examples of the present invention, and thus various technically preferable limitations are given. However, the scope of the present invention is not limited to the following description. As long as there is no description which limits, it is not restricted to these aspects.

[Schematic configuration of optical recording medium driving apparatus]
As shown in FIG. 1, an optical recording medium driving apparatus according to the present invention includes a spindle motor 103 as driving means for rotating an optical disk 102 serving as an optical recording medium, an optical head 104 according to the present invention, and driving means therefor. As a feed motor 105.

  Here, the spindle motor 103 is driven and controlled by a system controller 107 and a servo control unit 109 that also serve as a disk type discriminating unit, which will be described later, and is driven at a predetermined rotational speed.

  The optical disk 102 is an optical disk (for example, a so-called “CD”) that is a recording / reproducing disk using optical modulation recording (including so-called “magnetomagnetic recording”, “phase change recording”, “dye recording”, etc.). -R / RW "," DVD-RAM "," DVD-R / RW "," DVD + RW ", etc.) or various magneto-optical recording media.

  Further, the optical disk 102 may be selectively used from at least two types of optical disks having different optimum recording and / or reproducing light power on the recording surface, and the optimum recording and / or reproducing light power. It is also possible to use an optical disc in which the recording surface is divided into at least two different recording areas, and an optical disc in which a plurality of recording surfaces (recording layers) are laminated via a transparent substrate.

  The difference in the optimum recording and / or reproducing light power on the recording surface is not only due to the difference in the recording method itself on the optical disc, but also due to the difference in the rotational speed (linear velocity relative to the optical head) of the optical disc (so-called standard). N-times speed disk relative to high-speed disk).

  As the optical disc 102, a multilayer optical disc having optimum recording and / or reproducing light power or having the same at least two recording surfaces can be used. In this case, the optimum recording and / or reproducing light power difference for each recording surface occurs depending on the design of the multilayer optical disk.

  Incidentally, the wavelength of the recording and / or reproducing light of these optical discs can be about 400 nm to about 780 nm.

  The optical head 104 irradiates the recording surface of the optical disc 102 with a light beam, and detects the reflected light from the recording surface of this light beam. Further, the optical head 104 detects various light beams as will be described later based on the reflected light from the recording surface of the optical disk 102 and supplies signals corresponding to the respective light beams to the preamplifier unit 120.

  The output of the preamplifier unit 120 is sent to the signal modulation / demodulation unit and the ECC block 108. The signal modulation / demodulation unit and ECC block 108 performs signal modulation, demodulation, and addition of an ECC (error correction code). The optical head 104 irradiates light onto the recording surface of the rotating optical disk 102 in accordance with instructions from the signal modulation / demodulation unit and the ECC block 108. By such light irradiation, a signal is recorded on or reproduced from the optical disk 102.

  The preamplifier unit 120 is configured to generate a focus error signal, a tracking error signal, an RF signal, and the like based on a signal corresponding to each light beam. Depending on the type of optical recording medium to be recorded or reproduced, the servo control unit 109, signal modulation / demodulation unit, ECC block 108, and the like perform predetermined processing such as demodulation and error correction processing based on these signals. Is called.

  Thereby, the demodulated recording signal is sent to the external computer 130 or the like via the interface 111 if the optical disk 102 is for data storage of a computer, for example. The external computer 130 or the like can receive a signal recorded on the optical disc 102 as a reproduction signal.

  If the optical disc 102 is for so-called “audio / visual”, the digital / analog conversion is performed by the D / A conversion unit of the D / A / A / D converter 112 and supplied to the audio / visual processing unit 113. And this audio. The signal supplied to the visual processing unit 113 is the audio. Audio / video signal processing is performed in the visual processing unit 113 and transmitted to an external imaging / projection device via the audio / visual signal input / output unit 114.

  The optical head 104 is moved to a predetermined recording track on the optical disk 102 by a feed motor 105. The control of the spindle motor 103, the control of the feed motor 105, and the driving in the focusing direction and the driving in the tracking direction of the biaxial actuator that holds the objective lens serving as the light condensing means in the optical head 104 are respectively servo controlled. This is performed by the unit 109.

  In addition, the servo control unit 109 operates the optical coupling efficiency variable element disposed in the optical head 104 according to the present invention, so that the optical coupling efficiency in the optical head 104, that is, a laser light source such as a semiconductor laser element serving as a light source. The ratio of the total light amount of the light beam emitted from the optical disc 102 and the amount of light collected on the optical disc 102 is controlled differently depending on the recording mode and the reproduction mode and according to the type of the optical disc 102. This method is variable according to the temperature.

  Further, the laser control unit 121 controls a laser light source in the optical head 104. In particular, in this embodiment, an operation for controlling the output power of the laser light source to be different between the recording mode and the reproduction mode and according to the type of the optical disk 102 is performed.

  Further, when the optical disk 102 is selectively used from at least two types of optical disks having different optimum recording and / or reproducing light power on the recording surface (different recording methods, divided recording areas) The disc type discriminating sensor 115 is the type of the optical disc 102 on which the disc type discriminating sensor 115 is mounted. Is determined. As the optical disk 102, as described above, various types of optical disks using optical modulation recording or various magneto-optical recording media can be considered, and these have optimum recording and / or reproducing optical power on the recording surface. Different things are included. The disc type discrimination sensor 115 detects the surface reflectance of the optical disc 102 and other differences in shape and shape.

  Then, the system controller 107 determines the type of the optical disk 102 based on the detection result sent from the disk type determination sensor 115.

  Further, as a method for discriminating the type of the optical recording medium, it is conceivable to provide a detection hole for this cartridge in the optical recording medium housed in the cartridge. In addition, based on the information of the optical recording medium, for example, pre-mastered pits in the innermost circumference or table information (Table of Contents: TOC) recorded in the groove, the “disc type” or “recommended recording power” And “recommended reproduction power” may be detected, and recording and reproduction optical power suitable for recording and reproduction of the optical recording medium may be set.

  Then, the servo control unit 109 serving as an optical coupling efficiency control unit is controlled by the system controller 107, so that the optical coupling efficiency in the optical head 104 is changed according to the determination result of the disk type determination sensor 115. Control is performed according to the type of 102.

  Further, when an optical disc having a recording surface divided into at least two or more recording areas having different optimum recording and / or reproducing optical powers is used as the optical disc 102, recording and / or reproduction is performed by the recording area identifying means. The recording area to be detected is detected. When a plurality of recording areas are concentrically divided according to the distance from the center of the optical disc 102, the servo control unit 109 can be used as the recording area identifying means. The servo control unit 109 performs recording and / or reproduction by, for example, detecting the relative position between the optical head 104 and the optical disk 102 (including the case where the position is detected based on the address signal recorded on the disk 102). The recording area to be tried can be determined. Then, the servo control unit 109 controls the optical coupling efficiency in the optical head 104 according to the determination result of the recording area to be recorded and / or reproduced.

  Further, when the optical disk 102 is a multilayer optical disk having at least two or more recording surfaces having different optimum recording and / or reproducing light power, the recording surface to be recorded and / or reproduced by the recording surface identification means. Is determined. As the recording surface identification means, the servo control unit 109 can be used. The servo control unit 109 can detect the recording surface to be recorded and / or reproduced by detecting the relative position between the optical head 104 and the optical disc 102, for example. Then, the servo control unit 109 controls the optical coupling efficiency in the optical head 104 according to the determination result of the recording surface to be recorded and / or reproduced.

  Information on the type, recording area, and recording surface of these optical discs can also be determined by reading inventory information such as so-called TOC recorded on each optical disc.

  Further, in this optical recording medium driving device, a temperature sensor 122 is disposed in the vicinity of a semiconductor laser element or the like serving as a light source in the optical head 104 or a liquid crystal element serving as an optical coupling efficiency variable element. A signal indicating the temperature detected by the temperature sensor 122 is sent to the system controller 107 serving as control means. When the temperature detected by the temperature sensor 122 becomes lower than a predetermined temperature, the system controller 107 fixes the optical coupling efficiency via the servo control unit 109 regardless of the operation mode. That is, the system controller 107 stops the switching operation of the optical coupling efficiency regardless of the operation mode when the temperature detected by the temperature sensor 122 is lower than the predetermined temperature, for example, the optical coupling efficiency is maximized. To control.

  This is because, at low temperatures, the response speed of the liquid crystal becomes slow, so that the operation control for the liquid crystal element cannot be performed satisfactorily. On the other hand, the minimum value (lower limit) of the optical power that can be used without generating laser noise in the semiconductor laser element. This is because the reproduction characteristics are not affected even if the light emission power of the semiconductor laser element is sufficiently lowered.

[Configuration of optical head]
As shown in FIG. 2, the optical head according to the present invention used in the above-described optical recording medium driving apparatus includes a semiconductor laser element 212 serving as a light source, a collimator lens 213, and an optical coupling that constitutes an optical coupling efficiency variable means. An anamorphic prism 215 having a liquid crystal element 214 serving as an efficiency variable element and a polarization beam splitter film surface 215R serving as a polarization separating means, for example, a phase plate 217 such as a half (half) wavelength plate, a light separating means, A beam splitter 218, a detector element 219 for a FAPC (Front Auto Power Control) which is a photodetector for detecting the light emission power of the semiconductor laser element 212, a quarter (quarter) wavelength plate 224, a light condensing element. Objective lens 220, detection lens 221, multi-lens 222 as means, and light detection as light detection means It has a child 223, each of these optical components are configured individually mounted.

  The optical coupling efficiency varying means includes a liquid crystal element 214 that receives a light beam from the semiconductor laser element 212 and changes the polarization state of the light beam, and a polarization beam splitter film 215R that receives a light beam that has passed through the liquid crystal element 214. And is provided between the semiconductor laser element 212 and the beam splitter 218.

  The optical coupling efficiency variable means is a ratio of the amount of light collected on the optical disk 102 to the total amount of light emitted from the semiconductor laser element 212 by changing the polarization state of the light beam by the liquid crystal element 214. To change.

  In the following description, first, in the recording mode, the optical coupling efficiency variable element (liquid crystal element 214) is controlled to increase the optical coupling efficiency (this optical coupling efficiency mode is hereinafter referred to as “Open”). ), The optical coupling efficiency variable element is controlled in the reproduction mode to lower the optical coupling efficiency (this optical coupling efficiency mode is hereinafter referred to as “Close”). The operation will be described. In this optical head, the dynamic range required for the semiconductor laser element 212 can be reduced.

  After that, as shown in FIG. 8, the optical coupling efficiency variable element should be used even when the dynamic range of the board power required as a total is further expanded in order to cope with a plurality of types of recording media. Will explain that the dynamic range required for the semiconductor laser element 212 can be kept small. In this case, not only the switching between the recording mode and the reproduction mode but also the operation state of the optical coupling efficiency variable element is selected and used according to the recording and / or reproduction power of each recording medium.

  In this optical head, the reference for switching the optical coupling efficiency by the optical coupling efficiency variable element is changed according to the temperature detected by the temperature sensor 122. Thereby, even if the recording and / or reproducing power changes depending on the temperature in a plurality of media, this change can be dealt with.

  In this optical head 104, as shown in FIG. 2, the linearly polarized diffused light beam emitted from the semiconductor laser element 212 is incident on the collimator lens 213 to become a parallel light beam, and is incident on the liquid crystal element 214. Then, the light beam that has passed through the liquid crystal element 214 is sequentially incident on the anamorphic prism 215, the phase plate 217, and the beam splitter 218.

  In this optical head 104, a temperature sensor 122 is disposed in the vicinity of the semiconductor laser element 212 or the liquid crystal element 214. A signal indicating the temperature detected by the temperature sensor 122 is sent to the system controller 107.

  The anamorphic prism 215 shapes the cross-sectional shape of the light beam emitted from the semiconductor laser element 212 from an ellipse to a substantially circular shape. That is, the light beam emitted from the semiconductor laser element 212 is linearly polarized light and has an elliptical cross-sectional shape in which the polarization state indicated by the arrow P in FIG. Then, the light beam is incident from the incident surface of the anamorphic prism 215 inclined with respect to the minor axis direction of the cross-sectional shape, so that the beam diameter is expanded in the minor axis direction, and is substantially circular. Shaped into a light beam.

  The incident light beam incident on the beam splitter 218 via the anamorphic prism 215 and the phase plate 217 is directed to a planar reflecting surface inclined with respect to the optical axis of the incident light beam of the beam splitter 218. Thus, it is substantially P-polarized light. Note that the phase plate 217 is rotationally adjusted around the optical axis so that the polarization state of the incident light beam is P-polarized light with respect to the reflecting surface of the beam splitter 218.

  In this beam splitter 218, a constant ratio (for example, a constant ratio of 95% or less) of the incident light beam is transmitted through the reflecting surface and is incident on the quarter-wave plate 224. Here, a part of the incident light beam reflected by the reflecting surface of the beam splitter 218 (for example, at a constant ratio of 5% or more) is incident on a detection element 219 for FAPC described later. The incident light beam that has passed through the beam splitter 218 is converted into circularly polarized light by passing through the quarter-wave plate 224, and is condensed on the recording surface of the optical disc 102 by the objective lens 220.

  Then, the reflected light beam reflected by the recording surface of the optical disc 102 passes through the objective lens 220 and passes through the quarter-wave plate 224, so that a straight line in a direction orthogonal to the polarization state of the light beam in the outgoing optical path. The polarized light is returned to the beam splitter 218. At this time, the reflected light beam is substantially S-polarized light with respect to the reflecting surface of the beam splitter 218, and substantially the entire amount is reflected by this reflecting surface and separated from the optical path from the semiconductor laser element 212. The The reflected light beam separated from the optical path from the semiconductor laser element 212 is converted into convergent light by the detection lens 221 and given astigmatism by the multi-lens 222 to obtain a focus error signal by the astigmatism method. , Is incident on the light detection element 223. An RF signal, a focus error signal, a tracking error signal, and the like are generated based on a signal received and output by the light detection element 223.

  In this optical head 104, the light beam emitted from the semiconductor laser element 212 is subjected to the action of the liquid crystal element 214, which is an optical coupling efficiency variable element, and the polarization beam splitter film surface 215R of the anamorphic prism 215. After passing through the polarizing beam splitter film surface 215R, the optical coupling efficiency is appropriately variably controlled. When the light beam emitted from the semiconductor laser element 212 is changed from the recording mode to the reproduction mode in the same type of optical disc, or in the same recording area or on the same recording surface, than in the recording mode. The optical coupling efficiency is reduced to a small optical coupling efficiency. Further, when the playback mode is changed to the recording mode, the optical coupling efficiency is made larger than that in the playback mode and the light enters the optical disc 102.

  Note that the action of the liquid crystal element is not limited to that functioning as a wave plate, but for example, a twisted nematic type liquid crystal used in a display or the like can change the state of polarized light incident on the beam splitter. The same effect can be obtained.

  In the optical head 104, a current for driving a semiconductor laser element chip (not shown) in the semiconductor laser element 212 is supplied from the laser control unit 121 of the optical head 104. The laser control unit 121 may be outside the optical head 104 or may be mounted on the optical head 104.

  The liquid crystal element 214 changes the polarization state of the transmitted light based on the applied voltage. The applied voltage to the liquid crystal element 214 is controlled by the servo control unit 109. The light beam transmitted through the liquid crystal element 214 is incident on the anamorphic prism 215 in a state in which the polarization state is changed.

  The polarization beam splitter film surface 215R of the anamorphic prism 215 has a planar shape having a predetermined angle with respect to the optical axis of the incident light beam, transmits substantially 100% of the P-polarized light, and approximately 100 of the S-polarized light. % Reflection. Therefore, in the optical coupling efficiency mode Open, the polarization state of the light beam that passes through the liquid crystal element is substantially in the P-polarization direction, and substantially all light is transmitted. In the optical coupling efficiency mode “Close”, the polarization state of the light beam passing through the liquid crystal changes and the S polarization component is reflected by the anamorphic prism 215. For example, when the polarization state of the liquid crystal element 214 is rotated by 45 degrees, 50% of the light beam passes through the polarizing beam splitter film surface 215R of the anamorphic prism 215, and the remaining 50% of the light beam is reflected by the polarizing beam splitter film surface 215R.

  The light beam reflected by the polarization beam splitter film surface 215R of the anamorphic prism 215 passes through the total reflection preventing element (light emitting part) 215T and is received by the light detecting element 216 for monitoring the amount of light splitting, which serves as an optical coupling efficiency detecting means. Is done. The total reflection preventing element 215T prevents the light beam reflected on the polarization beam splitter film surface 215R from being totally reflected on the inner surface of the anamorphic prism 215. As shown in FIG. It is formed in a staircase shape having a plurality of orthogonal surfaces, and is disposed in optical close contact with the anamorphic prism 215. As shown in FIG. 4, the total antireflection element 215T is formed as a triangular prism having a surface substantially orthogonal to the light beam, and is disposed in optically close contact with the anamorphic prism 215, or As shown in FIG. 5, it may be formed integrally with the anamorphic prism 215.

  The output of the light detection element 216 for monitoring the amount of light branching corresponds to the product of the light emission output of the semiconductor laser element 212 and the light branching rate on the polarization beam splitter film surface 215R of the anamorphic prism 215. The optical head 104 substantially corresponds to the optical coupling efficiency. In this optical head, when the optical coupling efficiency is high, the amount of light incident on the optical branching amount monitoring photodetecting element 216 decreases, and when the optical coupling efficiency is low, the optical branching amount monitoring photodetecting element 216 The amount of incident light increases. The amount of light incident on the light detection element 216 for monitoring the amount of light split is an amount proportional to the product of 100%-[passage rate (%) of variable optical coupling efficiency] and "laser emission power". The output of the light splitting amount monitoring photodetecting element 216 is sent to the preamplifier 120 as shown in FIG.

  The light beam that has passed through the anamorphic prism 215 enters the beam splitter 218. The beam splitter 218 detects the light beam emitted from the semiconductor laser element 212 by using the FAPC detection element for monitoring the light that actually travels toward the recording surface of the optical disc 102 via the objective lens 220 and the light amount of the light beam that travels toward the recording surface. 219 and the light incident on 219 are separated at a constant ratio. The output of the FAPC detection element 219 is sent to the laser control unit 121, and an auto power control operation is executed. That is, the laser control unit 121 controls the light emission output of the semiconductor laser element 212 so that the output from the FAPC detection element 219 becomes a predetermined value. By this control, the output (board surface power) of the irradiated light beam on the recording surface of the optical disc 102 is made constant. Note that, as will be described later, the output value of the irradiation light beam that is set to a predetermined value on the recording surface of the optical disc 102 is a different value in the recording mode and the reproduction mode, and also differs depending on the type of the optical disc (optical light). In the case of the modulation recording method, pulse emission is used).

  The light beam from the semiconductor laser element 212 that has passed through the beam splitter 218 is incident on the objective lens 220 as described above. The objective lens 220 irradiates the incident light by focusing it on a certain point on the recording surface of the optical disk. The objective lens 220 is driven by a biaxial actuator (not shown) in a focus direction indicated by an arrow F in FIG. 2 and a tracking direction indicated by an arrow T in FIG.

  Further, the system controller 107, when the temperature in the vicinity of the liquid crystal element 214 becomes lower than a predetermined temperature based on the signal indicating the temperature sent from the temperature sensor 122, regardless of the operation mode as described above. Via the servo controller 109, the liquid crystal element 214 is controlled so that the optical coupling efficiency is maximized. In this case, in the reproduction mode, the light emission output of the semiconductor laser 212 is lower than when the optical coupling efficiency is small.

  At low temperatures, as shown in FIG. 6, the response speed of the liquid crystal becomes slow, so that the operation control on the liquid crystal element cannot be performed satisfactorily. On the other hand, as shown in FIG. Since the minimum value (lower limit) of the optical power that can be used without being generated is low, the reproduction characteristics are not affected even if the light emission power of the semiconductor laser element 212 is sufficiently low. Therefore, the above-mentioned “predetermined temperature” in this case is a temperature at which no laser noise is generated to the extent that the reproduction characteristics are affected even when the light emission power of the semiconductor laser element 212 is sufficiently lowered.

  In FIG. 7, the horizontal axis represents the output (mW) of the semiconductor laser element 212, and the vertical axis represents the laser noise level (dB / Hz). The output of the semiconductor laser element 212 whose laser noise level is equal to or lower than the predetermined value A in FIG. 6 is about 2 mW or more when the temperature is 0 ° C., about 3 mW or more when the temperature is 25 ° C., and the temperature is 45 °. In C, it is about 3.5 mW or more, and when the temperature is 65 ° C., it is about 4 mW or more. When the output of the semiconductor laser element 212 falls below these values at each temperature, the laser noise increases rapidly. Therefore, the optical coupling efficiency in the reproduction mode at each temperature needs to be set so that the light emission output of the semiconductor laser 212 does not increase the laser noise when the panel power is set to a predetermined output. .

  Assuming that the laser output corresponding to reproduction in the optical coupling efficiency mode “Open” with the maximum optical coupling efficiency is, for example, 2.5 mW, the temperature at which the laser noise is equal to or less than the predetermined value A is 0 ° C. and 25 ° C. It means between ℃.

  On the other hand, in FIG. 6, the horizontal axis indicates the temperature, and the vertical axis indicates the response speed of the liquid crystal element. “O → C” indicates switching from a state in which the liquid crystal element 214 corresponds to the optical coupling efficiency mode “Open” to a state corresponding to the optical coupling efficiency mode “Close”. The device 214 is switched from a state corresponding to the optical coupling efficiency mode “Open” to a state corresponding to the optical coupling efficiency mode “Close”. In the case of “O → C”, the response time, which was about 20 ms when the temperature is 20 ° C. or higher, is increased to about 80 ms when the temperature is around 0 ° C. Further, in the case of “C → O”, the response time, which was about 5 ms when the temperature is 20 ° C. or higher, is increased to about 20 ms when the temperature is around 0 ° C. At a lower temperature, the response speed decreases more rapidly. However, in this optical recording medium driving device, the operation mode is switched between temperatures of 0 ° C. and 25 ° C., and control is performed so that the state is always “Open” at temperatures of 0 ° C. or lower. There is no need to consider the effect of slowing down.

[Operation of optical recording medium driving apparatus]
In this optical recording medium driving device, in the recording mode, the optical coupling efficiency of the light emitted from the semiconductor laser element 212 and guided to the optical disk 102 is set to CEW (Coupling Efficiency write), and in the signal reproduction mode, the semiconductor When the optical coupling efficiency of the light emitted from the laser element 212 and guided to the optical disk 102 is CER (Coupling Efficiency Read), the following relationship is established.

CEW> CER
The same applies to the case where the optical coupling efficiency of the light guided to the optical disc 102 differs depending on the type of optical recording medium.

  Accordingly, by controlling the optical coupling efficiency of the optical coupling efficiency variable element at the time of recording and reproduction and at the time of changing the type of the optical recording medium, the output power of the semiconductor laser element 212 in the recording mode and in the reproducing mode is controlled. Even if the ratio is not extremely increased, the level of the light beam applied to the recording surface of the optical disk 102 can be changed greatly between the recording mode and the reproducing mode and according to the change of the type of the optical recording medium. It becomes possible. Further, the optical coupling efficiency is variably controlled according to the optical power on the recording surface at the time of optimum recording and / or reproduction depending on the type of the optical disk, the recording area, or the recording surface. The optical coupling efficiency increases as the optical power on the optimum recording surface increases. Depending on the configuration of the optical system, the relationship between the optical coupling efficiency and the optical power on the recording surface may be reversed.

  As described above, in this optical recording medium driving device, the optical disc is supplied with the optimum level of light in the recording mode and in the reproducing mode, or for each of the selected optical disc type, recording area, or recording surface. The recording surface can be irradiated to perform recording or reproduction, and good recording and reproduction characteristics can be obtained.

  Hereinafter, the operation of the optical coupling efficiency variable element in the present embodiment will be described in detail.

First, when the optical coupling efficiency when the optical coupling efficiency variable element is not used is CE0, and the passing light ratio of the optical coupling efficiency variable element is TW at the time of signal recording and TR at the time of signal reproduction, the following relation is established. .
(Optical coupling efficiency during signal recording) CEW = CE0 × TW
(Optical coupling efficiency during signal regeneration) CER = CE0 × TR
Further, assuming that the necessary recording surface condensing amount is PW at the time of signal recording and PR at the time of signal reproduction, the following relationship is established if the output required at the light source is LDW at the time of recording and LDR at the time of reproduction.
(When recording a signal) LDW = PW / CEW = PW / (CE0 × TW)
(During signal reproduction) LDR = PR / CER = PR / (CEO × TR)
Next, the dynamic range LDW / LDR required for the light output of the light source is shown as follows.

LDW / LDR = (PW / PR) × (TR / TW)
In addition, when not using an optical coupling efficiency variable element, it is the same as that of TR = TW. Thus, in this optical recording medium driving apparatus, the dynamic range required for the light output of the light source can be changed by the ratio of the transmitted light ratio of the optical coupling efficiency variable element.

  Further, in this optical recording medium driving device, as described above, when the temperature in the vicinity of the liquid crystal element 214 becomes lower than a predetermined temperature, the servo control unit 109 is used regardless of the operation mode as described above. Thus, the liquid crystal element 214 is controlled so that the optical coupling efficiency is maximized. In this case, in the reproduction mode, the light emission output of the semiconductor laser 212 is lower than when the optical coupling efficiency is small.

  At a low temperature, the response speed of the liquid crystal becomes slow, so that the operation control for the liquid crystal element cannot be performed satisfactorily. On the other hand, in the semiconductor laser element 212, the minimum value (lower limit) of the optical power that can be used without generating laser noise is set. This is because the reproduction characteristics are not affected even if the light emission power of the semiconductor laser element 212 is sufficiently lowered.

  Next, consider the case where a plurality of types of optical recording media are used. As the assumed optical recording medium, various media such as a multi-layer disc and a high linear velocity recording optical recording medium can be considered as described above.

  It is assumed that a semiconductor laser element is used as the light source. Here, the maximum optical output rating is 60 mW, the laser oscillation becomes stable, and the optical output that sufficiently reduces the laser noise changes depending on the temperature T. Let it be LDR (T).

  For example, as shown in FIG. 7, when T = 65 ° C., LDR (T) is LDR (65) = 4 mW. Similarly, LDR (45) = 3.5 mW LDR (25) = 3 mW, LDR (0) = 2mW.

  Further, it is assumed that the light collection amounts PW (A) and PR (A) on the recording surface required from the characteristics of the optical recording medium A (first type optical disc) are as follows.

PW (A) = 20mW
PR (A) = 1.5mW
Assume that the light collection amounts PW (B) and PR (B) on the recording surface required from the characteristics of the optical recording medium B (second type optical disc) are as follows.

PW (B) = 10mW
PR (B) = 1mW
In this case, if the optical coupling efficiency varying means is not used, the dynamic range of the light output of the light source can be expressed as follows.

  The dynamic range of the light output of the light source at T = 65 ° C. in which the laser noise has deteriorated due to the temperature rise can be expressed as follows.

[Dynamic range of light output of light source] = 60 mW / 4 mW = 15
Similarly, at T = 45 ° C., it can be expressed as follows.

[Dynamic range of light output of light source] = 60 mW / 3.5 mW = 17
At T = 25 ° C., it can be expressed as follows.

[Dynamic range of light output of light source] = 60 mW / 3 mW = 20
At T = 0 ° C., it can be expressed as follows.

[Dynamic range of light output of light source] = 60 mW / 2 mW = 30
The required dynamic range of the optical output on the recording surface of the optical disk can be expressed as follows.

[Necessary optical output dynamic range] = LDW (A) / LDR (B)
= PW (A) / PR (B) = 20 mW / 1 mW = 20
That is, at 25 ° C. or higher, the dynamic range of the light output of the light source is smaller than the required dynamic range of the light output. Therefore, good recording and reproduction cannot be performed with this light source.

  On the other hand, when the optical coupling efficiency variable means in the optical recording medium driving apparatus of the present invention is used, it becomes as follows.

  Considering that the dynamic range of the light output is 2/3 of the dynamic range of the light source in consideration of variations in the optical system.

  From the dynamic range of the light source, the required dynamic range of the light output can be expressed as follows.

T = 65 ° C. 15 * 2/3 = 10
T = 45 ° C. 17 * 2/3 = 11.4
T = 25 ° C. 20 * 2/3 = 13.3
T = 0 ° C, 30 * 2/3 = 20
The ratio of light passing through the optical coupling efficiency varying means is T1 = 100% in the optical coupling efficiency mode Open, and the optical coupling efficiency mode Close is changed depending on the temperature to be T2 (T). Assuming that T1 is set at the time of recording and T2 (T) is set at the time of reproducing the optical recording medium B, the required dynamic range of the optical output can be expressed as follows.

[Necessary optical output dynamic range] = LDW (A) / LDR (B)
= (PW (A) / PR (B)) × (T2 (T) / T1)
= (20mW / 1mW) × (T2 (T) / 100%)
Therefore, by setting T2 (T) to the following value, the required dynamic range of the light output becomes sufficiently smaller than the dynamic range of the light output of the light source.
T = 65 ° C., 50% or less T = 45 ° C., 57% or less T = 25 ° C., 67% or less T = 0 ° C., 100% or less Therefore, within the dynamic range of the light output of the light source, the first type of optical disc Recording on (A) and reproduction of the second type of recording disk (B) are possible.

  In this way, by increasing the ratio of light passing through the optical coupling efficiency variable means as the temperature rises, an increase in laser noise can be suppressed even when the temperature becomes high, and good reproduction characteristics can be obtained. .

  In this case, the following relationship is established by setting the design of the optical system as CE0 = 40% and setting the value of T2 (T) to the above value.

[Optical coupling efficiency during optical recording medium A signal recording] CE1 = CE0 × T1 = 40%
[Optical coupling efficiency during reproduction of optical recording medium B signal] CE2 = CE0 × T2 = 20% (T = 65 ° C.)
[Optical coupling efficiency during reproduction of optical recording medium B signal] CE2 = CE0 × T2 = 23% (T = 45 ° C.)
[Optical coupling efficiency during reproduction of optical recording medium B signal] CE2 = CE0 × T2 = 27% (T = 25 ° C.)
[Optical coupling efficiency during reproduction of optical recording medium B signal] CE2 = CE0 × T2 = 40% (T = 0 ° C.)
Therefore, the necessary light source light output is as follows.

[Optical recording medium A signal recording]
LDW (A) = PW (A) / CE1 = 20 mW / 40% = 50 mW
[When reproducing optical recording medium B signal]
(T = 65 ° C)
LDR (B) = PR (B) / CE2 = 1 mW / 20% = 5 mW
LDR (T) = 4mW
(T = 45 ° C)
LDR (B) = PR (B) / CE2 = 1 mW / 23% = 4.3 mW
LDR (T) = 3.5mW
(T = 25 ° C)
LDR (B) = PR (B) / CE2 = 1 mW / 27% = 3.7 mW
LDR (T) = 3mW
(T = 0 ° C)
LDR (B) = PR (B) / CE2 = 1 mW / 40% = 2.5 mW
LDR (T) = 2mW
As described above, recording can be performed at a light output of 50 mW with a margin with respect to the maximum light output rating of 60 mW, and the light output LDR (T) with sufficiently small laser noise can be recorded regardless of the temperature. Good reproduction is possible with a certain light output.

  At this time, the playback of the optical recording medium A signal is as follows.

LDR (A) = PR (A) /CE1=1.5 mW / 40% = 3.8 mW
(T = 65 ° C)
LDR (A) = PR (A) /CE2=1.5 mW / 20% = 7.5 mW
LDR (T) = 4mW
(T = 45 ° C)
LDR (A) = PR (A) /CE2=1.5 mW / 23% = 6.5 mW
LDR (T) = 3.5mW
(T = 25 ° C)
LDR (A) = PR (A) /CE2=1.5 mW / 27% = 5.6 mW
LDR (T) = 3mW
(T = 0 ° C)
LDR (A) = PR (A) /CE2=1.5 mW / 40% = 3.8 mW
LDR (T) = 2mW
Therefore, regarding the reproduction of the optical recording medium A signal, in consideration of a margin for LDR (T), T ≦ 25 ° C. may be CE1, and T ≧ 25 ° C. may be CE2.

  Regarding the recording of the optical recording medium B signal, it is as follows.

LDW (B) = PW (B) / CE1 = 10 mW / 40% = 25 mW
LDW (B) = PW (B) / CE2 = 10 mW / 20% = 25-50 mW (T = 0-65 ° C.)
In this case, either CE1 or CE2 may be used for the optical coupling efficiency.

  As will be described later, when the optical coupling efficiency is changed at the time of recording and / or reproducing, switching takes a certain time. Therefore, for the optical recording medium A, CE ≦ 1 It can be determined that it is easier to use CE2 for reproduction only at T ≧ 25 ° C. and CE2 for recording and reproduction for the optical recording medium B.

  As long as the information of “recommended recording / reproducing power” is recorded on the optical recording medium in advance, it can be handled in the same manner regardless of which medium is loaded.

  Here, it is assumed that the recommended recording power of a medium is PW0, the recommended reproduction power is PR0, the optical coupling efficiency is 40% when the passing light ratio in the optical coupling efficiency variable means is approximately 100%, and the optical coupling is performed at a certain temperature T. The optical coupling efficiency when the passing light ratio in the efficiency variable means is reduced is 40 × T2 (T)%, the assumed PW0 range is 9 mW to 22.5 mW, and the PR0 range is 0.9 mW to 2. 25 mW.

  As shown in FIG. 8, the combination of PR0 and PW0 read from the optical recording medium is one of the four recording medium modes (A), (B), (C1), and (C2). A determination is made, and in accordance with each, it is determined what to do with the attenuation state (passing light ratio in the optical coupling efficiency varying means) in the recording mode and the reproduction mode.

That is, considering the dynamic range of the light source,
PR0 ≦ PR (T)
PR (T) = LDR (T) × 40/100 (when T = 65 ° C., PR (65) = 1.6 mW)
Then, it is necessary to reduce the passing light ratio in the optical coupling efficiency variable means,
PW0 ≧ PW (T)
PW (T) = 60 × {40 × T2 (T)} / 100 (PW (65) = 12 mW at T = 65 ° C.)
Then, it is necessary to increase the passing light ratio in the optical coupling efficiency variable means.

  Accordingly, in the recording medium mode (A), it is necessary to reduce the passing light ratio in the optical coupling efficiency variable means in the reproduction mode, and either may be used in the recording mode. It is desirable to always lower the passing light ratio in the means.

  In the recording medium mode (B), it is necessary to reduce the passing light ratio in the optical coupling efficiency varying means in the reproducing mode, and it is necessary to increase the passing light ratio in the optical coupling efficiency varying means in the recording mode. It is necessary to switch the attenuation state by switching.

  In the recording medium mode (C1), either the reproducing mode or the recording mode may be used, so “the passing light ratio in the optical coupling efficiency varying means is always increased” may be used.

  In the recording medium mode (C2), the reproduction mode may be used. In the recording mode, it is necessary to increase the passing light ratio in the optical coupling efficiency variable means. It is desirable to always increase the light ratio.

  Therefore, in both the recording medium modes (C1) and (C2), it is only necessary to always increase the passing light ratio in the optical coupling efficiency variable means.

  When discriminating by providing a hole in the cartridge for storing the optical recording medium, if two (2 bits) holes are provided so that the four recording medium modes can be discriminated, the above-described processing can be performed. it can.

  Further, the present invention is not limited to this, and the value of the optical coupling efficiency may be set as appropriate within a range that satisfies the dynamic range of the light source. In some cases, a plurality of optical coupling efficiencies of 3 or more are possible. In this case, the manufacture of the light source can be facilitated. Further, it is possible to realize an optical head and an optical recording medium driving device that can easily obtain good characteristics without using a special light source.

  The order of control when dealing with a multi-layer (two-layer) disc having a plurality of recording surfaces is as follows. First, when the optical disc 102 is mounted, the optimum recording power is smaller than that of the multi-layer disc, for example, playback corresponding to a single-layer disc. First, disc type data (inventory data) recorded on the disc is reproduced by power. If the disc is a two-layer disc, the recording and / or reproducing power and optical coupling efficiency corresponding to the two-layer disc are set. .

  In FIG. 8, the value of “1.6 mW” that divides the recording medium modes (A), (B), and (C) is considered to change as the laser noise generation state changes depending on the temperature. It is done. Here, the boundary portion of “1.6 mW” is indicated as a function PR (T) of the temperature T. If the light output at which the laser noise is sufficiently reduced is 4 mW or more at room temperature and 2.25 mW or more at a “certain temperature” lower than room temperature, PR (T) is, for example, 1 Although it is .6 mW, at “a certain temperature”, for example, it is 0.9 mW. That is, since PR (T) changes in accordance with the temperature in this manner, all are in the recording medium mode (C) below “a certain temperature”, and switching of the optical coupling efficiency becomes unnecessary.

  In addition, when the environmental temperature repeatedly rises and falls across a certain temperature that makes it unnecessary to switch the optical coupling efficiency, the necessity and necessity of switching the optical coupling efficiency frequently fluctuate. Control becomes complicated. Assuming such a case, the temperature at which the temperature is lowered and “switching of the optical coupling efficiency is not required” is different from the temperature at which the temperature is increased and “switching of the optical coupling efficiency is necessary”. It is desirable to be temperature.

  Next, the switching operation between the recording mode and the reproduction mode in the optical recording medium driving apparatus 101 as described above will be described.

  FIG. 9 is a timing chart showing the state of laser light associated with the switching operation between the recording mode and the reproduction mode in the optical recording medium driving apparatus 101. FIG. 9A shows the amount of light condensed on the recording surface of the optical disc 102 ( 9B is the laser beam transmittance of the optical coupling efficiency variable element, FIG. 9C is the output of the optical branching amount monitoring light detection element 216, and FIG. 9D is the laser emission power. Shows changes.

  In the optical recording medium driving apparatus 101, after the response of the liquid crystal element 214 is started, the timing is measured in accordance with a command from the system controller 107 as follows, so that the laser control unit 121 switches between the recording mode and the reproduction mode. Do.

  That is, in the playback mode, the liquid crystal element 214 changes the polarization state of the light beam passing therethrough so that the S-polarized component is reflected by the polarization beam splitter film surface 215R of the anamorphic prism 215. An applied voltage is applied, and the transmittance of the optical coupling efficiency variable element is set to 50%. The laser emission power is 5 mW, there is little laser noise, and good reproduction characteristics are obtained.

  When switching from the reproduction mode to the recording mode, first, the applied voltage to the liquid crystal element 214 is changed by the servo control unit 109 in accordance with a command from the system controller 107, and the polarization state of the light beam passing through the liquid crystal element 214 is changed. The film surface 215R is changed so as to be substantially P-polarized light.

  With the response of the liquid crystal element 214, the transmittance of the optical coupling efficiency variable element changes from 50% to 100%, and the laser emission power changes from 5 mW to 2.5 mW by the operation of auto power control. At this time, the output of the light branching amount monitoring photodetecting element 216 also decreases according to the change in the transmittance of the optical coupling efficiency variable element and the change in the laser emission power. At this time, since the liquid crystal element has a finite response speed, the power focused on the disk is maintained as the reproduction power in the transition period of the response.

  When the output from the optical branching amount monitor is input to the servo control unit 109 via the preamplifier 120 and falls below the preset output level reference value Poff, the transmittance by the optical coupling efficiency variable means is sufficiently close to 100%. The signal recording pulse is generated from the laser control unit 121 according to the signal modulation and the instruction of the ECC block 108 via the system controller 107, and the laser emission power is modulated to record the signal. Is called.

  Next, when switching from the recording mode to the reproduction mode, first, the laser control unit 121 switches between the recording mode and the reproduction mode in accordance with a command from the system controller 107. In this state, since the laser emission power is as low as 2.5 mW, the laser noise is increased.

  After the laser output is switched to the reproduction power, the applied voltage to the liquid crystal element 214 is changed by the servo control unit 109 in accordance with a command from the system controller 107, and the polarization state of the light beam passing through the liquid crystal element 214 is changed.

  According to the response of the liquid crystal element 214, the pass rate of the optical coupling efficiency variable element is changed from 100% to 50%, and the laser output power is changed from 2.5 mW to 5 mW and the laser noise is reduced by the operation of the auto power control. As a result, a good reproduction signal can be detected. At this time, it is determined that the optical coupling efficiency has sufficiently decreased at the stage where the optical divider amount monitor output exceeds the preset reference value Pon, and signal regeneration is started. In some cases, when switching to the playback mode, signal playback may be started immediately, and retry may be performed while an error occurs in the playback signal due to laser noise. At this time, the output of the light branching amount monitoring photodetecting element 216 also increases in accordance with the change in the transmittance of the optical coupling efficiency variable element and the change in the laser emission power.

  If the procedure for switching the recording / reproducing mode is not performed according to the above procedure, the following problems occur.

  First, when switching from the playback mode to the recording mode, the optical output remains high (the optical coupling efficiency remains low) and the recording operation starts. Therefore, an attempt to obtain an output exceeding the maximum optical output rating of the laser may occur. Is destroyed.

  Further, when the recording mode is switched to the reproduction mode, the reproduction operation is started with the light output being low (the optical coupling efficiency is high), so that there is a lot of laser noise and good reproduction characteristics cannot be obtained. Further, if the optical coupling efficiency is first reduced after the recording operation, there is a possibility that the laser may be destroyed in some cases in order to obtain an output exceeding the maximum optical output rating of the laser.

  Therefore, by performing the switching operation of the recording / reproducing mode using the above-described procedure of the present example, even if the laser output ratio at the time of recording and reproduction is small, the laser noise at the time of reproduction can be sufficiently reduced, and the manufacturability Therefore, it is possible to provide an optical recording medium driving device that can obtain good recording and reproducing characteristics even when using a light source with good quality and a light source with a small maximum light output rating. That is, in order to prevent the above problems from occurring, it is necessary to observe the timing and wait for a time for the variable operation of the optical coupling efficiency variable means to be completed to complete recording or reproduction, or to perform a variable operation. ON / OFF (increase / decrease in optical coupling efficiency) may be detected and managed by some method.

  As a technique for detecting ON / OFF of the variable operation (increase / decrease in the optical coupling efficiency), the following technique can be considered.

  For example, when performing a variable operation mechanically, it is possible to know the driving state using a position sensor or the like. Also, the rear monitor terminal of the semiconductor laser element (output from the light receiving element that monitors the light emitted in the direction opposite to the emission direction) is used, or light that is discarded without reaching the optical recording medium is provided for monitoring. Thus, it is also possible to detect a change in light output.

  Further, when the light branching ratio is variable by the polarization beam splitter film surface 215R, the branched light power may be detected by providing a light receiving element as described above.

  FIG. 10 is a timing chart showing the state of laser light accompanying the switching operation between the recording mode and the reproduction mode when the temperature in the vicinity of the liquid crystal element 214 is lower than a predetermined temperature in the optical recording medium driving apparatus 101. 10 (A) is the amount of light (board surface power) collected on the recording surface of the optical disk 102, FIG. 10 (B) is the laser beam transmittance in the optical coupling efficiency variable element, and FIG. 10 (C) is for monitoring the optical branching amount. The output of the light detection element 216, FIG. 10D, shows a change in laser emission power.

  In this optical recording medium driving apparatus 101, when the temperature in the vicinity of the liquid crystal element 214 is lower than a predetermined temperature, the liquid crystal element 214 functions as described below regardless of switching between the recording mode and the reproduction mode. It will not be allowed.

  That is, in the reproduction mode, the transmittance of the optical coupling efficiency variable element is set to approximately 100%. The laser emission power is 2.5 mW, which is lower than the predetermined temperature, so that there is little laser noise and good reproduction characteristics are obtained.

  When switching from the reproduction mode to the recording mode, the voltage applied to the liquid crystal element 214 is not changed, and the phase difference of the liquid crystal element 214 does not change.

  The transmittance of the optical coupling efficiency variable element remains 100%, and the laser emission power is maintained at 2.5 mW by the operation of auto power control. At this time, the output of the light branching amount monitoring photodetecting element 216 also does not change. The power focused on the disc is also kept at the playback power.

  Next, a signal recording pulse is generated from the laser controller 121 according to the signal modulation and the instruction of the ECC block 108 via the system controller 107, and the laser emission power is modulated to record the signal.

  When switching from the recording mode to the reproduction mode, first, the laser control unit 121 switches between the recording mode and the reproduction mode in accordance with a command from the system controller 107. In this state, the laser emission power is as low as 2.5 mW, but the laser noise is small because the temperature is lower than a predetermined temperature.

  Even after the laser output is switched to the reproduction power, the applied voltage to the liquid crystal element 214 is not changed, and the polarization state of the light beam passing through the liquid crystal element 214 does not change.

  The passing rate of the optical coupling efficiency variable element remains 100%, and the laser emission power is maintained at 2.5 mW by the operation of auto power control. Since the temperature is lower than the predetermined temperature, there is little laser noise and a good reproduction signal can be detected. Also at this time, the output of the light branching amount monitoring photodetecting element 216 does not change because the transmittance of the optical coupling efficiency variable element does not change.

  Next, the operation of the optical recording medium driving apparatus will be described in more detail with reference to a flowchart.

  In the case where the optical coupling efficiency mode is switched with a hysteresis, the temperature at which the optical coupling efficiency mode is switched is Ta and Tb (Ta ≦ Tb), and the following characteristics are obtained. In the recording mode, the optical coupling efficiency mode is not switched. For simplicity, the optical coupling efficiency mode “Open” is used in the recording mode regardless of the temperature.

  When T ≦ Ta, the laser noise is very good in the optical coupling efficiency mode “Open” and very good in the optical coupling efficiency mode “Close”, but the liquid crystal response speed is slow.

  When Ta ≦ T ≦ Tb, the laser noise is good in the optical coupling efficiency mode “Open”, very good in the optical coupling efficiency mode “Close”, and the liquid crystal response speed is normal.

  When Tb ≦ T, the laser noise is poor in the optical coupling efficiency mode “Open”, good in the optical coupling efficiency mode “Close”, and the liquid crystal response speed is fast.

As the system operation mode, three modes of “recording mode”, “reproduction mode”, and “standby mode” are conceivable, and the optical coupling efficiency mode is switched in the reproduction mode or the standby mode. Switching the optical coupling efficiency mode in the recording mode is not desirable because the APC loop gain is changed, and in particular, in the case of pulse recording, a defect is likely to occur in the recording waveform.
When T ≦ Ta, the optical coupling efficiency mode “Open” is set in the reproduction mode, the optical coupling efficiency mode “Open” in the recording mode, and the optical coupling efficiency mode “Close mode” in the standby mode.

  In Ta ≦ T ≦ Tb, the “O / C mode” in the reproduction mode, the optical coupling efficiency mode “Close” has priority in the recording mode, and the previous state is maintained in the standby mode.

  In Tb ≦ T, the optical coupling efficiency mode “Close” is set in the reproduction mode, the optical coupling efficiency mode “Close” in the recording mode, and the optical coupling efficiency mode “Close” in the standby mode.

  The “O / C mode” means that the previous “attenuation” state is maintained in the standby mode and “attenuation switching” is performed after receiving the commands “playback” and “recording”. However, “attenuate switching” is not performed during execution of “reproduction mode”. What is “Close mode”? In the “standby” state, “attenuate close” is always set, and only when a “record” command is received, the mode is switched to “attenuate open”. “Open” is always “Attenuate Open” regardless of recording / playback.

  In the “standby” state, the above three modes are switched at temperatures Ta and Tb. In the “standby” state, “Attenuate Close” is always executed when T> Tb in a change from low temperature to high temperature, and “Attenuate Open” is always executed in T <Ta in a change from high temperature to low temperature. Thus, by providing hysteresis with respect to the temperature, even if the temperature fluctuates, the attenuation state is repeatedly switched and does not become unstable.

  Further, regardless of whether recording is performed before or after recording, the previous attenuation state is maintained while Ta ≦ T ≦ Tb, so that the switching of the attenuation state is not repeated unnecessarily depending on the temperature.

  In the “regeneration” state, “Attenuate Close” is always executed when T> Tb in a change from low temperature to high temperature, and “Attenuate Open” is always executed in T <Ta in a change from high temperature to low temperature. Thus, by providing hysteresis with respect to the temperature, even if the temperature fluctuates, the attenuation state is repeatedly switched and does not become unstable.

  In addition, when “standby” is changed to “reproduction” in the state of Ta ≦ T ≦ Tb, “attenuate close” is executed, so that better reproduction characteristics can be obtained.

Then, it is considered that the optical coupling efficiency is changed in switching between the recording mode and the reproduction mode using the output of the photodetection element 216 for branch amount monitoring. As the operation mode of the optical recording medium driving device, three states of “recording mode”, “reproduction mode”, and “standby mode” can be considered. When “recording mode” is indicated by “W”, “reproduction mode” is indicated by “R”, and “standby mode” is indicated by “−”, the following operation mode can be changed.
[R-W-R-R-R-W-R-W-R-R]
Then, there are three possible timings for changing the optical coupling efficiency, that is, the “switching of the attenuation state” as follows.

  (1) In the “standby” state, the previous “attenuation state” is held, and the “switching of the attenuation state” is performed after receiving the next “playback” or “record” command (the operation in this case is illustrated in FIG. 11 and FIG. 12).

  (2) In the “standby” state, the “attenuated state” with low optical coupling efficiency is always set, and only when the “record” command is received, the “attenuated state” with high optical coupling efficiency is switched (the operation in this case is shown in FIG. (Shown in FIG. 14).

  (3) In the “standby” state, the “attenuated state” with high optical coupling efficiency is always set, and only when the “regeneration” command is received, the “attenuated state” with low optical coupling efficiency is switched (the operation in this case is shown in FIG. (Shown in FIG. 16).

  Hereinafter, these three types will be described.

  (1) In the “standby” state, the previous “attenuation state” is held, and the “switching of the attenuation state” is performed after receiving the next “playback” or “record” command (FIGS. 11 and 12). ).

  First, in the “standby” state, the system controller 107 retains the “attenuation state” until then, and performs the “switching of the attenuation state” after receiving the next “playback” or “record” command. When the command “record” is received, as shown in FIG. 11, the process starts at step st1, and at the next step st2, the liquid crystal application voltage is controlled, and the liquid crystal application voltage increases the optical coupling efficiency. If the voltage applied to the liquid crystal is a voltage that increases the optical coupling efficiency, the process proceeds to step st3, and if it is a voltage that decreases the optical coupling efficiency, the process proceeds to step st4. In step st4, the system controller 107 controls the liquid crystal application voltage to set the liquid crystal application voltage as a voltage for increasing the optical coupling efficiency (voltage corresponding to “Open”), and proceeds to step st3. In step st3, the system controller 107 determines whether or not the output of the light branching amount monitoring photodetecting element 216 is lower than a predetermined set value (reference value Poff). If it is lower than the predetermined set value (reference value Poff), the process proceeds to step st5, and if it is not lower than the predetermined set value (reference value Poff), the process stays at step st3. In step st <b> 5, the system controller 107 determines whether or not the change width of the output of the optical branching amount monitoring photodetecting element 216 is smaller than a predetermined set width over a predetermined set time. . If it has been smaller than the predetermined setting width for a predetermined set time or longer, the process proceeds to step st6, and if it has been smaller than the predetermined set width for not longer than the predetermined set time. Remains at step st5. In step st6, the system controller 107 starts a recording operation. When it is time to end the recording operation, the process proceeds to the next step st7, where the recording operation is ended, the reproduction power is restored, the mode is shifted to the “standby” mode, and the operation ends at step st8.

  Next, in the “standby” state, the system controller 107 holds the “attenuation state” until then, and performs “switching of the attenuation state” after receiving the next “playback” or “record” command. When the command “replay” is received, the process starts at step st9 as shown in FIG. 12, and at the next step st10, it is determined whether the temperature in the vicinity of the liquid crystal element 214 is equal to or higher than a predetermined temperature. If the temperature is equal to or higher than the predetermined temperature, the process proceeds to step st11. If the temperature is lower than the predetermined temperature, the process proceeds to step st12. In step st12, the voltage applied to the liquid crystal is set to a voltage for increasing the optical coupling efficiency (voltage corresponding to “Open”), and the process proceeds to step st16.

  In step st11, the liquid crystal application voltage is controlled to determine whether the liquid crystal application voltage is a voltage that lowers the optical coupling efficiency (a voltage corresponding to “Close”). Proceeding to st13, if the voltage increases the optical coupling efficiency, the process proceeds to step st14. In step st14, the system controller 107 controls the liquid crystal application voltage to set the liquid crystal application voltage as a voltage that lowers the optical coupling efficiency (voltage corresponding to “Close”), and proceeds to step st13. In step st13, the system controller 107 determines whether or not the output of the light branching amount monitoring photodetecting element 216 is higher than a predetermined set value (reference value Pon). The system controller 107 proceeds to step st15 if it is higher than the predetermined set value (reference value Pon), and stays in step st13 if it is not higher than the predetermined set value (reference value Pon). In step st <b> 15, the system controller 107 determines whether or not the change width of the output of the light splitting amount monitoring photodetecting element 216 is smaller than a predetermined set width over a predetermined set time. . The system controller 107 proceeds to step st16 if it has been smaller than the predetermined set width for a predetermined set time or longer, and proceeds to step st16, and if it has been smaller than the predetermined set width is longer than the predetermined set time. If not, the process stays at step st15. In step st16, the system controller 107 starts a reproduction operation. Then, when it is time to end the reproduction operation, the system controller 107 proceeds to the next step st17, ends the reproduction operation, shifts to the “standby” mode, and ends the operation at step st18.

  (2) In the “standby” state, the “attenuated state” with low optical coupling efficiency is always set, and only when the “record” command is received, the “attenuated state” with high optical coupling efficiency is switched (FIGS. 13 and 14).

  Then, the system controller 107 always sets the “attenuation state” with low optical coupling efficiency in the “standby” state, and switches to the “attenuation state” with high optical coupling efficiency only when receiving the “record” command. When the command "is received, as shown in FIG. 13, the process starts at step st19, and at the next step st20, the liquid crystal application voltage is controlled so that the liquid crystal application voltage increases the optical coupling efficiency (" As a voltage corresponding to “Open”, the process proceeds to step st21. In step st21, it is determined whether or not the output of the light branching amount monitoring photodetecting element 216 is lower than a predetermined set value (reference value Poff). The system controller 107 proceeds to step st22 if it is lower than the predetermined set value (reference value Poff), and stays in step st21 if it is not lower than the predetermined set value (reference value Poff). In step st <b> 22, the system controller 107 determines whether or not the change width of the output of the optical branching amount monitoring photodetecting element 216 is smaller than a predetermined set width over a predetermined set time. . The system controller 107 proceeds to step st23 if it has been smaller than the predetermined set width for a predetermined set time or longer, and proceeds to step st23, and has been smaller than the predetermined set width for the predetermined set time or longer. If not, the process stays at step st22. In step st23, the system controller 107 starts a recording operation. If it is time to end the recording operation, the system controller 107 proceeds to the next step st24, ends the recording operation, returns to the reproduction power, and proceeds to step st25. In step st25, the system controller 107 controls the liquid crystal application voltage to set the liquid crystal application voltage as a voltage (voltage corresponding to “Close”) that lowers the optical coupling efficiency, and proceeds to step st26. In step st26, the system controller 107 shifts to the “standby” mode, and ends the operation in step st27.

  Further, the system controller 107 always sets the “attenuation state” having low optical coupling efficiency in the “standby” state, and performs “reproduction” in the operation of switching to the “attenuation state” having high optical coupling efficiency only when the “record” command is received. 14 ”, the process starts at step st28 as shown in FIG. 14, and at the next step st29, it is determined whether or not the temperature in the vicinity of the liquid crystal element 214 is equal to or higher than a predetermined temperature. If the temperature is equal to or higher than the temperature, the process proceeds to step st30. If the temperature is lower than the predetermined temperature, the process proceeds to step st31. In step st31, the voltage applied to the liquid crystal is set to a voltage for increasing the optical coupling efficiency (voltage corresponding to “Open”), and the process proceeds to step st33.

  In step st30, it is determined whether or not the output of the light branching amount monitoring photodetecting element 216 is higher than a predetermined set value (reference value Pon). The system controller 107 proceeds to step st32 if it is higher than the predetermined set value (reference value Pon), and stays in step st30 if it is not higher than the predetermined set value (reference value Pon). In step st <b> 32, the system controller 107 determines whether or not the change width of the output of the optical branching amount monitoring photodetecting element 216 is smaller than a predetermined set width over a predetermined set time. . The system controller 107 proceeds to step st33 if it has been smaller than the predetermined set width for a predetermined set time or longer, and proceeds to step st33, and has been smaller than the predetermined set width for the predetermined set time or longer. If not, the process stays at step st32. In step st33, the system controller 107 starts a reproduction operation. Then, when it is time to end the reproduction operation, the system controller 107 proceeds to the next step st34 to end the reproduction operation, shift to the “standby” mode, and end the operation at step st35.

  (3) In the “standby” state, the “attenuated state” with high optical coupling efficiency is always set, and the “attenuated state” with low optical coupling efficiency is switched only when the “regeneration” command is received (FIGS. 15 and 16).

  Then, the system controller 107 always sets the “attenuation state” with high optical coupling efficiency in the “standby” state, and switches to the “attenuation state” with low optical coupling efficiency only when the “reproduction” command is received. 15, the process starts at step st36, and at the next step st37, the output of the light detection element 216 for monitoring the optical branching amount is a predetermined set value (reference value Poff). To determine if it is lower. The system controller 107 proceeds to step st38 if it is lower than the predetermined set value (reference value Poff), and stays in step st37 if it is not lower than the predetermined set value (reference value Poff). In step st <b> 38, the system controller 107 determines whether or not the change width of the output of the optical branching amount monitoring photodetecting element 216 is smaller than the predetermined set width over a predetermined set time. . The system controller 107 proceeds to step st39 if it has been smaller than the predetermined set width for a predetermined set time or longer, and proceeds to step st39, and has been smaller than the predetermined set width for the predetermined set time or longer. If not, the process stays at step st38. In step st39, the system controller 107 starts a recording operation. Then, when it is time to end the recording operation, the system controller 107 proceeds to the next step st40, ends the recording operation, returns to the reproduction power, shifts to the “standby” mode, and proceeds to step st41. End the operation.

  Next, the system controller 107 is in an “attenuated state” where the optical coupling efficiency is always high in the “standby” state, and in an operation of switching to an “attenuating state” where the optical coupling efficiency is low only when a “regeneration” command is received. When the command “play” is received, the process starts at step st42 as shown in FIG. 16, and at the next step st43, it is determined whether the temperature in the vicinity of the liquid crystal element 214 is equal to or higher than a predetermined temperature. When the temperature is higher than the predetermined temperature, the process proceeds to step st44, and when the temperature is lower than the predetermined temperature, the process proceeds to step st45. In step st45, the voltage applied to the liquid crystal is set to a voltage for increasing the optical coupling efficiency (voltage corresponding to “Open”), and the process proceeds to step st48.

  In step st44, the liquid crystal application voltage is controlled, and the liquid crystal application voltage is set to a voltage for reducing the optical coupling efficiency (voltage corresponding to “Close”), and the process proceeds to step st46. In step st46, the system controller 107 determines whether or not the output of the light splitting amount monitoring photodetecting element 216 is higher than a predetermined set value (reference value Pon). The system controller 107 proceeds to step st47 if it is higher than the predetermined set value (reference value Pon), and stays in step st46 if it is not higher than the predetermined set value (reference value Pon). In step st <b> 47, the system controller 107 determines whether or not the change width of the output of the light detection element 216 for monitoring the optical branching amount has been smaller than the predetermined set width over a predetermined set time. . If the system controller 107 has been smaller than the predetermined set width for a predetermined set time or longer, the system controller 107 proceeds to step st48, and the system controller 107 has been smaller than the predetermined set width for the predetermined set time or longer. If not, the process stays at step st47. In step st48, the system controller 107 starts a reproduction operation. Then, when it is time to end the reproduction operation, the system controller 107 proceeds to the next step st49, ends the recording operation, and proceeds to step st50. In step st50, the system controller 107 controls the liquid crystal application voltage to set the liquid crystal application voltage as a voltage for increasing the optical coupling efficiency (voltage corresponding to “Open”), and then proceeds to step st51. In step st51, the process shifts to the “standby” mode, and the operation ends in step st52.

  As shown in FIG. 17, the system controller 107 starts at step st53 as a response to different types of optical recording media, and at the next step st54, based on the temperature sensor output, the recommended reproduction power PR0. The reference powers PR (T) and PW (T) corresponding to the temperature are compared with the recommended recording power PW0. In step st55, the output of the irradiated light beam (board surface power) on the recording surface of the optical disc is set to a predetermined value as a voltage (voltage corresponding to “Close”) for controlling the liquid crystal application voltage to lower the optical coupling efficiency. For example, 0.9 mW (min) is set, and the process proceeds to step st56.

  In step st56, the system controller 107 determines whether or not the output of the light splitting amount monitoring photodetecting element 216 is higher than a predetermined set value (reference value Pon (0.9 mW and a value corresponding to the temperature at that time)). Determine. The output of the light detection element 216 for monitoring the optical branching amount changes according to the setting of the panel power and the passage rate of the optical coupling efficiency variable means at that temperature, and accordingly, the set value (reference value Pon ) Is set as appropriate. The system controller 107 proceeds to step st57 if the output of the light branching amount monitoring photodetecting element 216 is higher than a predetermined set value (reference value Pon), and if not higher than the predetermined set value (reference value Pon), the system controller 107 proceeds to step st57. Stay at st56.

  In step st57, the system controller 107 determines whether or not the change width of the output of the optical detection unit 216 for monitoring the optical branching amount is smaller than the predetermined set width over a predetermined set time. . The system controller 107 proceeds to step st58 if it has been smaller than the predetermined set time for a predetermined set time or longer, and proceeds to step st58, and has been smaller than the predetermined set width for the predetermined set time or longer. If not, the process stays at step st57. In step st58, the system controller 107 starts a focus servo operation in the optical head (focus ON), and proceeds to step st59. In step st59, the system controller 107 moves the optical head to the innermost peripheral position of the optical disc, and proceeds to step st60. In step st60, the system controller 107 detects the recommended recording power PW0 and the recommended reproduction power PR0, and proceeds to step st61.

  In step st61, the system controller 107 determines whether or not the recommended reproduction power PR0 is smaller than the reference power PR (T) at that temperature. The system controller 107 proceeds to step st62 if the recommended reproduction power PR0 is smaller than the reference power PR (T) at that temperature, and proceeds to step st65 if the recommended reproduction power PR0 is not smaller than the reference power PR (T) at that temperature. move on. In step st62, the system controller 107 determines whether or not the recommended recording power PW0 is smaller than the reference power PW (T) at that temperature. If the recommended recording power PW0 is smaller than the reference power PW (T) at that temperature, the process proceeds to step st63, and if the recommended recording power PW0 is not smaller than the reference power PW (T) at that temperature, the process proceeds to step st64.

  In step st63, the system controller 107 determines that the “attenuate type” is the recording medium mode (A) shown in FIG. 8, and controls the liquid crystal applied voltage in accordance with the determination result. In step st64, the system controller 107 determines that the “attenuate type” is the recording medium mode (B) shown in FIG. 8, and controls the liquid crystal applied voltage according to the determination result. In step st65, the system controller 107 determines that the “attenuate type” is the recording medium mode (C) ((C1) or (C2)) shown in FIG. 8, and the liquid crystal applied voltage is determined according to the determination result. Control.

  PR (T) is, for example, 1.6 mW at room temperature, but at “a certain temperature”, it is, for example, 0.9 mW. That is, PR (T) changes in this way depending on the temperature, so that below “a certain temperature”, everything becomes the recording medium mode (C), and the switching of the optical coupling efficiency becomes unnecessary.

  Regarding the reference power PW (T), the semiconductor laser element is more likely to be deteriorated as the temperature is higher, and the semiconductor laser element is more likely to be deteriorated as the power is higher. May be made smaller.

[Other Embodiments]
In all the configurations of the optical head described above, the beam splitter 218 may be configured so that S-polarized light having passed through the phase plate 217 is incident thereon. In this case, the optical head is configured in a state in which the positional relationship among the quarter-wave plate 224, the objective lens 220, the optical disk 102, and the FAPC detection element 219 in FIG.

  That is, in this optical head 104, the incident light beam that has passed through the phase plate 217 is substantially S-polarized light with respect to the reflecting surface of the beam splitter 218. The phase plate 217 is rotationally adjusted around the optical axis so that the polarization state of the incident light beam is S-polarized light with respect to the reflecting surface of the beam splitter 218. In this beam splitter 218, the incident light beam is reflected by the reflecting surface at a certain ratio (for example, a certain ratio of 95% or less) and is incident on the quarter-wave plate 224. Here, a part of the incident light beam transmitted through the reflecting surface (for example, at a constant ratio of 5% or more) enters the FAPC detection element 219. The incident light beam reflected by the beam splitter 218 is converted into circularly polarized light by passing through the quarter-wave plate 224 and condensed on the recording surface of the optical disc 102 by the objective lens 220.

  Then, the reflected light beam reflected by the recording surface of the optical disc 102 passes through the objective lens 220 and passes through the quarter-wave plate 224, so that a straight line in a direction orthogonal to the polarization state of the light beam in the outgoing optical path. The polarized light is returned to the beam splitter 218. At this time, the reflected light beam is substantially P-polarized with respect to the reflecting surface of the beam splitter 218, and substantially the entire amount is transmitted through the reflecting surface and separated from the optical path from the semiconductor laser element 212. Is done. The reflected light beam separated from the optical path from the semiconductor laser element 212 is converted into convergent light by the detection lens 221 and given astigmatism by the multi-lens 222 to obtain a focus error signal by the astigmatism method. , Is incident on the light detection element 223.

  Further, as shown in FIG. 18, the optical head according to the present invention may be configured by rotating the semiconductor laser element 212, the liquid crystal element 214, and the anamorphic prism 215 by 90 degrees around the optical axis. Even in this case, the light beam incident on the beam splitter 218 is adjusted by the phase plate 217 so as to be substantially P-polarized with respect to the reflection surface of the beam splitter 218.

  Further, in the optical head according to the present invention, as shown in FIG. 19, the optical axis of the light beam incident on the anamorphic prism 215 is inclined more greatly than the above-described configuration with respect to the incident surface of the anamorphic prism 215. The semiconductor laser element 212 may be positioned and configured as described above. In this case, the emitted light from the anamorphic prism 215 to the light branching amount monitoring light detecting element 216 is emitted substantially perpendicularly to the side surface of the anamorphic prism 215. 215T is not necessary.

  Further, as shown in FIG. 20, the optical head according to the present invention may be configured using a cubic polarization beam splitter 215 instead of the anamorphic prism 215. In this case, the cross section of the outgoing light beam from the semiconductor laser element 212 is not shaped into a circle.

  As described above, in the optical head and the optical recording medium driving device to which the present invention is applied, based on the temperature sensor arranged in the vicinity of the light source or the optical coupling efficiency variable means and the temperature detected by the temperature sensor. And a control means for controlling the optical coupling efficiency variable means. When the temperature detected by the temperature sensor is equal to or higher than a predetermined temperature, the control unit controls the optical coupling efficiency varying unit to change the optical coupling efficiency according to the operation mode, and is detected by the temperature sensor. When the temperature is lower than the predetermined temperature, the optical coupling efficiency variable means is controlled to fix the optical coupling efficiency regardless of the operation mode.

  Therefore, in this optical head and the optical recording medium driving device, there is no problem that the response speed of the optical coupling efficiency variable means becomes slow at low temperatures, and the semiconductor laser element is used as the light source at such low temperatures. Even in the case of using, since the minimum value of the optical power that can be used without generating laser noise is lowered, the reproduction characteristics are not affected.

  Also, in this optical head and optical recording medium driving device, the power ratio of the light source in the recording mode and the reproduction mode can be reduced to sufficiently reduce the laser noise during reproduction, and the light output maximum rating can be reduced with good manufacturability. Even if a simple light source is used, good recording and reproduction characteristics can be obtained.

  Further, in the optical head and the optical recording medium driving apparatus, according to the type of the optical recording medium having different optimum recording and / or reproducing optical power, according to the recording surface of the optical recording medium, or according to the optical recording Depending on the recording area on the recording surface of the medium, the optical coupling efficiency variable means can be controlled to optimize the recording and / or reproducing light power on the recording surface of the optical recording medium, and to reduce the laser noise during reproduction. Can be made sufficiently small.

  That is, the present invention can provide an optical head and an optical recording medium driving device which are designed not to cause a problem that the response speed of the optical coupling efficiency variable means becomes slow even at a low temperature lower than a predetermined temperature. It is.

  Further, the present invention reduces the light power ratio of the light source during recording (in recording mode) and during reproduction (in reproduction mode), sufficiently reduces laser noise during reproduction, and provides a light output with good manufacturability. It is possible to provide an optical head and an optical recording medium driving device capable of obtaining good recording and reproducing characteristics even when a light source having a smaller maximum rating is used.

  Furthermore, the present invention provides a plurality of types of optical recording media, multilayer optical recording media having different optical powers for optimum recording and / or reproduction, or optical recording media having a recording surface divided into a plurality of recording areas. Even for various types of optical recording media, the laser noise during reproduction is made sufficiently small, and even if a light source with a small maximum output power rating with good manufacturability is used, each type of optical recording medium and multilayer optical recording medium It is possible to provide an optical head and an optical recording medium driving apparatus that can obtain good recording and / or reproducing characteristics for each recording surface and each of a plurality of recording areas on the recording surface.

1 is a block diagram showing a configuration of an optical recording medium driving apparatus incorporating an optical coupling efficiency variable element and an optical head in an embodiment of the present invention. It is a side view which shows the optical head in the said optical recording medium drive device. It is a side view which shows the structure of the anamorphic prism of the said optical head. It is a side view which shows the other example of a structure of the said anamorphic prism. It is a side view which shows the further another example of a structure of the said anamorphic prism. It is the schematic which shows the relationship between the response speed of the liquid crystal element which comprises the optical coupling efficiency variable element of the said optical head, and temperature. It is a graph which shows the relationship between the laser noise and temperature in the semiconductor laser element of the said optical head. It is a graph which shows the relationship between "recommended reproduction power" and "recommended recording power" about the optical recording medium used in the said optical recording medium drive device. 4 is a timing chart showing a state of laser light accompanying a switching operation between a recording mode and a reproduction mode in the optical recording medium driving device. 6 is a timing chart showing a state of laser light accompanying a switching operation between a recording mode and a reproduction mode when the temperature is lower than a predetermined temperature in the optical recording medium driving device. In the above-mentioned optical recording medium driving device, in the “standby” state, the “attenuation state” is maintained, and the operation of “switching the attenuation state” is performed after receiving the command “recording”. In the optical recording medium driving apparatus, in the “standby” state, the “attenuation state” is maintained and a “replay” command is received and then “attenuation state switching” is performed. In the above optical recording medium driving apparatus, in the “standby” state, the “attenuation state” with low optical coupling efficiency is always set, and only when the “record” command is received, the operation is switched to the “attenuation state” with high optical coupling efficiency. 6 is a flowchart showing an operation when receiving a command “record”. In the above optical recording medium driving apparatus, in the “standby” state, the “attenuation state” with low optical coupling efficiency is always set, and only when the “record” command is received, the operation is switched to the “attenuation state” with high optical coupling efficiency. 6 is a flowchart showing an operation when receiving a command “play”. In the optical recording medium driving apparatus, in the “standby” state, the “attenuation state” with high optical coupling efficiency is always set, and only when the “reproduction” command is received, the operation is switched to the “attenuation state” with high optical coupling efficiency. 6 is a flowchart showing an operation when receiving a command “record”. In the optical recording medium driving apparatus, in the “standby” state, the “attenuation state” with high optical coupling efficiency is always set, and only when the “reproduction” command is received, the operation is switched to the “attenuation state” with high optical coupling efficiency. 6 is a flowchart showing an operation when receiving a command “play”. 6 is a flowchart showing an “attenuated state” switching operation when the optical recording medium driving apparatus supports a plurality of types of optical recording media. FIG. 5 is a side view showing another configuration of the optical head in the optical recording medium driving apparatus (a semiconductor laser element and an anamorphic prism rotated 90 degrees around the optical axis). It is a side view which shows the further another form (Things which inclined the optical axis of the incident light beam to an anamorphic prism.) Of the structure of the optical head in the said optical recording medium drive device. FIG. 10 is a side view showing still another form of the optical head in the optical recording medium driving apparatus (using a cubic polarizing beam splitter instead of an anamorphic prism).

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Optical recording medium drive device, 102 Optical disk, 103 Spindle motor, 104 Optical head, 107 System controller, 109 Servo control circuit, 122 Temperature sensor, 212 Semiconductor laser element, 214 Liquid crystal element, 215 Anamorphic prism, 216 Optical branching amount Photodetector for monitor, 218 beam splitter, 219 detector for FAPC, 220 objective lens, 223 photodetector

Claims (84)

A light source;
A light condensing means for condensing and irradiating the light beam emitted from the light source on an optical recording medium;
A light separating means for separating the optical path of the light beam emitted from the light source and the optical path of the reflected light beam reflected by the optical recording medium and passing through the light collecting means;
A light detecting means for receiving the reflected light beam that has passed through the light separating means;
An optical coupling efficiency variable unit that is provided between the light source and the light condensing unit and changes an optical coupling efficiency that is a ratio of a light amount collected on the optical recording medium to a total light amount emitted from the light source. When,
A temperature sensor arranged in the vicinity of the light source or the optical coupling efficiency variable means;
Control means for controlling the optical coupling efficiency variable means based on the temperature detected by the temperature sensor,
When the temperature detected by the temperature sensor is equal to or higher than a predetermined temperature, the control means controls the optical coupling efficiency varying means to change the optical coupling efficiency according to an operation mode, and the temperature sensor An optical head characterized in that when the detected temperature is lower than a predetermined temperature, the optical coupling efficiency variable means is controlled to fix the optical coupling efficiency regardless of the operation mode. 2. The optical head according to claim 1, wherein the control unit fixes the optical coupling efficiency as a maximum when the temperature detected by the temperature sensor is lower than a predetermined temperature. The optical coupling efficiency variable means includes a liquid crystal element that changes a polarization state of the light beam and a polarization separation means on which the light beam that has passed through the liquid crystal element is incident, and the polarization state of the light beam is changed by the liquid crystal element. The optical head according to claim 1, wherein the optical coupling efficiency is changed. A light beam emitted to the optical recording medium is detected by detecting the light power of the light beam emitted from the light source and reaching the light separation means, and controlling the light emission power of the light source based on the detected light power. The optical head according to claim 1, further comprising light emission power control means for maintaining the optical power of the light constant. 2. The optical head according to claim 1, wherein the control unit performs switching to change the optical coupling efficiency from a small state to a large state and switching to change the optical coupling efficiency from a large state to a small state at different temperatures. . The optical head according to claim 1, wherein the control means switches the optical coupling efficiency when the operation mode is a standby mode. 2. The optical head according to claim 1, wherein the control means switches the optical coupling efficiency when the operation mode is a reproduction mode. The optical head according to claim 1, wherein the control means does not switch the optical coupling efficiency when the operation mode is a recording mode. 2. The optical head according to claim 1, wherein, in the same type of optical recording medium, the control means makes the optical coupling efficiency smaller in the reproduction mode than in the recording mode. The optical coupling efficiency variable means further comprises an optical coupling efficiency detecting means comprising a light detecting means for receiving a light beam branched from an optical path directed to the optical recording medium by the polarization separating means. The optical head according to 1. 11. The optical head according to claim 10, wherein the start of the recording / reproducing switching operation is determined based on a detection result by the optical coupling efficiency detecting means. 12. The optical head according to claim 11, wherein the switching time of the optical coupling efficiency variable means is determined based on a change amount per time of a detection result by the optical coupling efficiency detection means. 12. The optical head according to claim 11, wherein a reference value for switching the optical coupling efficiency variable means is preset. 14. The optical head according to claim 13, wherein the reference value is variably set in accordance with an optimum reproduction light power that varies depending on temperature. 14. The optical head according to claim 13, wherein the switching time of the optical coupling efficiency variable means is determined based on a magnitude relationship between a detection result by the optical coupling efficiency detection means and the reference value. The switching time of the optical coupling efficiency variable means is determined based on the magnitude relationship between the detection result by the optical coupling efficiency detection means and the reference value and the amount of change per hour of the detection result by the optical coupling efficiency detection means. The optical head according to claim 13. The optical head according to claim 13, wherein the reference value is changed according to temperature. 11. The optical head according to claim 10, wherein whether or not the operation of the optical coupling efficiency variable means is normal is confirmed based on a detection result by the optical coupling efficiency detection means. 19. The optical head according to claim 18, wherein the switching time of the optical coupling efficiency variable means is determined based on a change amount per time of a detection result by the optical coupling efficiency detection means. 19. The optical head according to claim 18, wherein a reference value for performing a switching operation of the optical coupling efficiency by the optical coupling efficiency variable unit is set in advance as a detection result by the optical coupling efficiency detection unit. 21. The optical head according to claim 20, wherein the reference value is variably set according to the optimum reproducing light power for the optical recording medium. 21. The optical head according to claim 20, wherein the switching time of the optical coupling efficiency by the optical coupling efficiency variable means is determined based on a magnitude relationship between a detection result by the optical coupling efficiency detection means and the reference value. . When the optical coupling efficiency is switched by the optical coupling efficiency variable means based on the magnitude relationship between the detection result by the optical coupling efficiency detection means and the reference value and the amount of change per hour of the detection result by the optical coupling efficiency detection means The optical head according to claim 20, wherein the optical head is determined. The optical head according to claim 20, wherein the reference value is changed according to temperature. The optical head according to claim 1, wherein recording and / or reproduction is performed on at least two types of optical recording media having different optimum recording and / or reproducing optical powers. An optical coupling efficiency detecting means comprising a light detecting means for receiving a light beam branched from the optical path toward the optical recording medium by the polarization separating means in the optical coupling efficiency varying means;
An optical coupling efficiency control means for controlling a change in the optical coupling efficiency by the optical coupling efficiency detection means and a light emission power of the light source based on a detection result by the optical coupling efficiency detection means;
26. The optical head according to claim 25, wherein the optical coupling efficiency control means controls the optical coupling efficiency variable means in accordance with the type of the optical recording medium. 27. The optical recording medium according to claim 26, wherein the two or more types of optical recording media have different optimum recording and / or reproducing optical power on the recording surface due to a difference in relative speed with the optical head. head. 27. The optical head according to claim 26, wherein the two or more types of optical recording media have different optimum recording and / or reproducing light power on a recording surface due to a difference in recording method. 27. The optical head according to claim 26, wherein the two or more types of optical recording media are each recording surface in a multilayer optical recording medium having at least two recording surfaces. 27. The optical head according to claim 26, wherein at least one of the two or more types of optical recording media is each recording surface in a multilayer optical recording medium having at least two or more recording surfaces. 27. The optical head according to claim 26, wherein the two or more types of optical recording media are each recording area in an optical recording medium in which a recording surface is divided into at least two recording areas. 27. The optical head according to claim 26, wherein at least one of the two or more types of optical recording media is each recording area in the optical recording medium in which a recording surface is divided into at least two recording areas. In the optical coupling efficiency variable means, when the operation for decreasing the optical coupling efficiency is faster than the operation for increasing, the state in which the optical coupling efficiency is increased is set to the standby state, and the operation for increasing the optical coupling efficiency is faster than the operation for decreasing. 27. The optical head according to claim 26, wherein the standby state is a state where the optical coupling efficiency is lowered. A medium type determining means for determining the type of the optical recording medium;
27. The optical head according to claim 26, wherein the optical coupling efficiency control means controls the optical coupling efficiency variable means in accordance with the type of the optical recording medium determined by the medium type determination means. 35. The optical head according to claim 34, wherein the medium type discriminating unit discriminates the type of the optical recording medium based on a result of reading the catalog information recorded on the optical recording medium. 35. The optical head according to claim 34, wherein the medium type determining means determines the type of the optical recording medium based on an outer shape of the optical recording medium. 35. The optical head according to claim 34, wherein the medium type discriminating unit discriminates the type of the optical recording medium by detecting which one of the multilayer recording layers in the optical recording medium is a recording layer. 35. The type of optical recording medium according to claim 34, wherein the medium type discrimination means discriminates the type of the optical recording medium by detecting which of the recording areas is divided into a plurality of recording areas. Light head. Based on the combination of the “recording power” according to the optical recording medium determined by the medium type determining means and the “reproduction power” according to the optical recording medium and the usable output range of the light source output, the optical coupling efficiency is determined. The optical head according to claim 34, wherein the optical head is determined. 40. The optical head according to claim 39, wherein the presence or absence of switching of the optical coupling efficiency at the time of switching between recording and reproducing operation is determined based on the determined optical coupling efficiency. The optical coupling efficiency control unit controls the optical coupling efficiency while monitoring the detection result by the optical coupling efficiency detection unit based on a combination of the determination result by the medium type determination unit and the selected operation mode. The optical head according to claim 34, wherein: When the control unit switches from the reproduction mode to the recording mode, the timing for changing the optical coupling efficiency precedes the timing at which the amount of light collected on the optical recording medium changes, and also switches from the recording mode to the reproduction mode. 10. The optical head according to claim 9, wherein the timing at which the amount of light condensed on the optical recording medium is changed precedes the timing at which the optical coupling efficiency is changed. A light source, a light condensing means for condensing and irradiating the light beam emitted from the light source on the optical recording medium, an optical path of the light beam emitted from the light source, and the light beam reflected by the optical recording medium. A light separating means for separating the optical path of the reflected light beam passed through the light collecting means, a light detecting means for receiving the reflected light beam passed through the light separating means, and a space between the light source and the light collecting means. An optical coupling efficiency variable means for changing optical coupling efficiency, which is a ratio of the amount of light collected on the optical recording medium to the total amount of light emitted from the light source, and the light source or the optical coupling efficiency. An optical head having a temperature sensor arranged in the vicinity of the variable means, and a control means for controlling the optical coupling efficiency variable means based on the temperature detected by the temperature sensor;
Driving means for rotationally driving the optical recording medium,
When the temperature detected by the temperature sensor is equal to or higher than a predetermined temperature, the control means controls the optical coupling efficiency varying means to change the optical coupling efficiency according to an operation mode, and the temperature sensor When the detected temperature is lower than a predetermined temperature, the optical coupling efficiency variable means is controlled to fix the optical coupling efficiency regardless of the operation mode. 44. The optical recording medium driving device according to claim 43, wherein the control means fixes the optical coupling efficiency as a maximum when the temperature detected by the temperature sensor is lower than a predetermined temperature. The optical coupling efficiency variable means includes a liquid crystal element that changes a polarization state of the light beam and a polarization separation means on which the light beam that has passed through the liquid crystal element is incident, and the polarization state of the light beam is changed by the liquid crystal element. 44. The optical recording medium driving device according to claim 43, wherein the optical coupling efficiency is changed accordingly. A light beam emitted to the optical recording medium is detected by detecting the light power of the light beam emitted from the light source and reaching the light separation means, and controlling the light emission power of the light source based on the detected light power. 44. The optical recording medium driving device according to claim 43, further comprising light emission power control means for maintaining the optical power of the light source constant. 44. The optical recording according to claim 43, wherein the control means performs switching to change the optical coupling efficiency from a small state to a large state and switching to change the optical coupling efficiency from a large state to a small state at different temperatures. Medium drive device. 44. The optical recording medium driving device according to claim 43, wherein the control means switches the optical coupling efficiency when the operation mode is a standby mode. 44. The optical recording medium driving device according to claim 43, wherein the control means switches the optical coupling efficiency when the operation mode is a reproduction mode. 44. The optical recording medium driving device according to claim 43, wherein the control means does not switch the optical coupling efficiency when the operation mode is a recording mode. 44. The optical recording medium driving device according to claim 43, wherein the control means makes the optical coupling efficiency smaller in the reproduction mode than in the recording mode in the same type of optical recording medium. The optical coupling efficiency variable means further comprises an optical coupling efficiency detecting means comprising a light detecting means for receiving a light beam branched from an optical path directed to the optical recording medium by the polarization separating means. 44. The optical recording medium driving device according to 43. 53. The optical recording medium driving device according to claim 52, wherein the start of the recording / reproducing switching operation is determined based on a detection result by the optical coupling efficiency detecting means. 54. The optical recording medium driving device according to claim 53, wherein the switching time of the optical coupling efficiency variable means is determined based on a change amount per time of a detection result by the optical coupling efficiency detection means. 54. The optical recording medium driving device according to claim 53, wherein a reference value for switching the optical coupling efficiency varying means is preset. 56. The optical recording medium driving device according to claim 55, wherein the reference value is variably set in accordance with an optimum reproducing optical power that varies with temperature. 56. The optical recording medium driving device according to claim 55, wherein the switching time of the optical coupling efficiency variable means is determined based on a magnitude relationship between a detection result by the optical coupling efficiency detection means and the reference value. The switching time of the optical coupling efficiency variable means is determined based on the magnitude relationship between the detection result by the optical coupling efficiency detection means and the reference value and the amount of change per hour of the detection result by the optical coupling efficiency detection means. 56. The optical recording medium driving device according to claim 55. The optical recording medium driving device according to claim 55, wherein the reference value is changed according to temperature. 53. The optical recording medium driving device according to claim 52, wherein whether or not the operation of the optical coupling efficiency variable means is normal is confirmed based on a detection result by the optical coupling efficiency detection means. 61. The optical recording medium driving device according to claim 60, wherein the switching time of the optical coupling efficiency variable means is determined based on a change amount per time of a detection result by the optical coupling efficiency detection means. 61. The optical recording medium driving device according to claim 60, wherein a reference value for performing a switching operation of the optical coupling efficiency by the optical coupling efficiency variable means is preset for a detection result by the optical coupling efficiency detecting means. . 64. The optical recording medium driving device according to claim 62, wherein the reference value is variably set according to the optimum reproducing optical power for the optical recording medium. 63. The optical recording according to claim 62, wherein the switching time of the optical coupling efficiency by the optical coupling efficiency variable means is determined based on a magnitude relationship between a detection result by the optical coupling efficiency detection means and the reference value. Medium drive device. When the optical coupling efficiency is switched by the optical coupling efficiency variable means based on the magnitude relationship between the detection result by the optical coupling efficiency detection means and the reference value and the amount of change per hour of the detection result by the optical coupling efficiency detection means 63. The optical recording medium driving device according to claim 62, wherein: 64. The optical recording medium driving device according to claim 62, wherein the reference value is changed according to temperature. 44. The optical recording medium driving device according to claim 43, wherein recording and / or reproduction is performed on at least two or more types of optical recording media having different optimum recording and / or reproducing optical powers. An optical coupling efficiency detecting means comprising a light detecting means for receiving a light beam branched from the optical path toward the optical recording medium by the polarization separating means in the optical coupling efficiency varying means;
An optical coupling efficiency control means for controlling a change in the optical coupling efficiency by the optical coupling efficiency detection means and a light emission power of the light source based on a detection result by the optical coupling efficiency detection means;
68. The optical recording medium driving device according to claim 67, wherein the optical coupling efficiency control means controls the optical coupling efficiency variable means in accordance with the type of the optical recording medium. The optical recording medium according to claim 68, wherein the two or more types of optical recording media have different optimum recording and / or reproducing optical power on the recording surface due to a difference in relative speed with the optical head. Recording medium driving device. 69. The optical recording medium driving device according to claim 68, wherein the two or more types of optical recording media have different optimum recording and / or reproducing light power on the recording surface due to a difference in recording method. 69. The optical recording medium driving device according to claim 68, wherein the two or more types of optical recording media are each recording surface in a multilayer optical recording medium having at least two recording surfaces. 69. The optical recording medium driving device according to claim 68, wherein at least one of the two or more types of optical recording media is each recording surface in a multilayer optical recording medium having at least two recording surfaces. 69. The optical recording medium driving device according to claim 68, wherein the two or more types of optical recording media are each recording area in an optical recording medium in which a recording surface is divided into at least two or more recording areas. 69. The optical recording medium driving device according to claim 68, wherein at least one of the two or more types of optical recording media is each recording area in an optical recording medium in which a recording surface is divided into at least two or more recording areas. . In the optical coupling efficiency variable means, when the operation for decreasing the optical coupling efficiency is faster than the operation for increasing, the state in which the optical coupling efficiency is increased is set to the standby state, and the operation for increasing the optical coupling efficiency is faster than the operation for decreasing. 69. The optical recording medium driving device according to claim 68, wherein the standby state is a state where the optical coupling efficiency is lowered. A medium type discriminating unit for discriminating the type of the optical recording medium, wherein the optical coupling efficiency control unit controls the optical coupling efficiency varying unit according to the type of the optical recording medium discriminated by the medium type discriminating unit; 69. The optical recording medium driving device according to claim 68, wherein: 77. The optical recording medium driving apparatus according to claim 76, wherein the medium type determining means determines the type of the optical recording medium based on a result of reading the catalog information recorded on the optical recording medium. 77. The optical recording medium driving device according to claim 76, wherein the medium type determining means determines the type of the optical recording medium based on an outer shape of the optical recording medium. 77. The optical recording medium according to claim 76, wherein the medium type discriminating means discriminates the type of the optical recording medium by detecting which one of the multilayer recording layers in the optical recording medium is a recording layer. Drive device. 77. The medium type discriminating means discriminates the type of the optical recording medium by detecting which one of the recording areas is divided into a plurality of recording areas. Optical recording medium driving device. Based on the combination of the “recording power” according to the optical recording medium determined by the medium type determining means and the “reproduction power” according to the optical recording medium and the usable output range of the light source output, the optical coupling efficiency is determined. 77. The optical recording medium driving device according to claim 76, wherein the optical recording medium driving device is determined. 82. The optical recording medium driving device according to claim 81, wherein whether or not the optical coupling efficiency is switched when switching between recording and reproducing operation is determined based on the determined optical coupling efficiency. The optical coupling efficiency control unit controls the optical coupling efficiency while monitoring the detection result by the optical coupling efficiency detection unit based on a combination of the determination result by the medium type determination unit and the selected operation mode. 77. The optical recording medium driving device according to claim 76. When the control unit switches from the reproduction mode to the recording mode, the timing for changing the optical coupling efficiency precedes the timing at which the amount of light collected on the optical recording medium changes, and also switches from the recording mode to the reproduction mode. 52. The optical recording medium driving apparatus according to claim 51, wherein the timing at which the amount of light collected on the optical recording medium is changed precedes the timing at which the optical coupling efficiency is changed.

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