JP2007128593A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent recording and reproducing errors by identifying and detecting the lifetime of a laser diode and contamination on an objective lens or the surface of an optical disk medium to alarm a user, in an optical disk drive device. <P>SOLUTION: When a gradient of a current flowing through the laser diode 101 and an output current of a front monitor 107 is smaller than a value obtained by multiplying a gradient measured when shipping the drive by a prescribed coefficient, it is determined that the laser diode is deteriorated. Further, the ratio of the reflectance of an existing optical disk to that of the reference optical disk is stored. When the reflectance of the optical disk 110 is less than a value obtained by multiplying the reflectance of the reference optical disk measured when shipping the drive by the ratio and further by a prescribed coefficient, it is determined that the objective lens 109 or the optical disk 110 is contaminated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that can prevent information recording or reproduction errors.

  Optical discs known as CDs and DVDs have been widely popularized by consumers as information recording media with large capacity and low price that can be accessed randomly. Information recording on the optical disk is performed by changing the state of the information recording surface by the heat of the laser beam condensed by the objective lens. On the other hand, information is reproduced by reading a change in reflectance caused by a change in the state of the information recording surface with a laser beam condensed by an objective lens. Therefore, it is important to control the power of the laser beam in order to stably record or reproduce information on the optical disc.

  When reproducing the information, the current flowing through the laser diode is controlled by the laser driving circuit so that the output current of the front monitor is constant. Thereby, the light emission power of the laser can be kept constant. However, laser diodes deteriorate with the passage of time. The current for outputting the laser beam of the same power gradually increases, and finally no light is emitted even if the current is increased. If this occurs during the operation of the drive, the power of the laser beam applied to the information recording surface of the optical disk is reduced, and a recording or reproduction error occurs. Thereafter, recording / reproduction becomes impossible and the drive becomes unusable. Thus, the main factor of the drive life is the deterioration of the laser diode. Therefore, in order to accurately determine the drive life time, it is necessary to detect the deterioration of the laser diode.

  As a method for detecting deterioration of a laser diode, Japanese Patent Laid-Open No. 62-248686 detects deterioration of a laser diode when the amount of current flowing through the laser diode exceeds a predetermined value. As another method, in Japanese Patent Laid-Open Nos. 2000-90438, 2001-77459, and 2004-39189, the amount of current flowing in the laser diode is a predetermined value relative to the initial value at the time of drive shipment. With this increase, laser diode degradation is detected. In JP-A-11-213425, a recording light emission waveform is monitored, and deterioration of the laser diode is detected by a change in the waveform. In Japanese Patent Laid-Open No. 2004-335049, it is stated that the output obtained by the front monitor is smaller than a predetermined reference output when the maximum current is applied in the current range expected to flow through the laser diode. The deterioration of the diode is detected.

  By the way, the reduction of the power of the laser beam irradiated to the information recording surface of the optical disk, which causes a recording / reproducing error, is caused not only by the deterioration of the laser diode but also by contamination of the objective lens and the optical disk. Therefore, when detecting the possibility of occurrence of a recording / reproducing error, it is necessary to be able to determine whether the cause is deterioration of the laser diode or contamination of the objective lens or the optical disk.

  As a method for detecting dirt on an objective lens or an optical disk, Japanese Patent Laid-Open No. 8-63771 discloses that when the amount of light falls below the threshold value, the value obtained by multiplying the reflected light amount at the time of manufacturing the device by a comparison coefficient (1 or less) is used as a threshold value. In addition, an alarm is activated to urge the objective lens or optical disk to be cleaned. In JP-A-10-269603, a laser beam reflecting means is provided in the drive, and the output of the photodetector when the reflecting means is irradiated with the laser light is compared with a reference value, whereby the objective lens or Detecting dirt on the optical disc. In Japanese Patent Laid-Open No. 2005-78701, contamination of the objective lens or the optical disk is detected when the reflected light amount of the used optical disk is smaller than the reflected light amount of the reference optical disk by a predetermined amount or more.

JP-A-62-223486 JP 2000-90438 A Japanese Patent Laid-Open No. 2001-77459 Japanese Patent Laid-Open No. 2004-39189 Japanese Patent Laid-Open No. 11-213425 JP 2004-335049 A JP-A-8-63771 Japanese Patent Laid-Open No. 10-269603 JP 2005-78701 A

  The current vs. optical power characteristics of a laser diode change not only with the deterioration of the device but also with the ambient temperature. In particular, the emission threshold current increases with increasing temperature, as shown in FIG. In the methods disclosed in JP-A-62-223486, JP-A-2000-90438, JP-A-2001-77459, JP-A-2004-39189, and JP-A-2004-335049, the laser is changed by changing the temperature. Since the threshold current of the diode changes, the current value and the optical power do not have a one-to-one relationship. Therefore, in order to accurately detect the deterioration of the laser diode, it is necessary to remove the influence of the threshold current change due to the temperature change.

  In addition, regarding the detection of dirt on the objective lens and the optical disk, when various types of optical disks are mounted so that this can be carried out in a normal drive use state, the objective lens and the optical disk are detected based on the reflectance. It is necessary to be able to detect dirt.

  The present invention eliminates the influence of a change in threshold current due to a temperature change and can detect deterioration of a laser diode, and detects contamination of an objective lens and an optical disk regardless of the type of the mounted optical disk. An object of the present invention is to provide an optical disc device that can perform the above-described operation. Another object of the present invention is to provide an optical disc apparatus capable of identifying and detecting whether the laser diode is deteriorated and whether the objective lens or the optical disc is dirty, and warning the user.

In the present invention, the following means are used to solve the above problems.
When detecting deterioration of the laser diode, in order to respond to changes in the threshold current of the laser diode due to temperature changes, the rate of change of the output level of the front monitor with respect to changes in the current flowing through the laser diode is measured, and this is determined according to a predetermined standard. When the value is smaller, it is determined that the laser diode has deteriorated. The predetermined reference value can be a value obtained by multiplying a measured value at the time of drive shipment by a predetermined coefficient α (0 <α <1).

Further, when detecting dirt on the objective lens and the optical disk, in order to cope with various types of optical disks, a reference value is previously determined for each type of optical disk of an existing type at the time of drive shipment. During the drive operation, when the laser beam is focused on the area where the data of the optical disk loaded in the drive is not recorded, the ratio between the output of the photodetector and the output of the front monitor is On the other hand, if it is smaller than a predetermined reference value, it is determined that the objective lens or the optical disk is dirty. This reference value can be determined as follows. For an existing type optical disc, the type and the reflectivity of an area where no data is recorded are tabulated and stored in a nonvolatile memory in advance. The reflectivity is expressed in the form of a ratio k _i to the reflectivity R ₀ of the reference optical disc. In addition, when the drive is shipped, the reflectance R ₀ of the reference optical disk is measured and stored in the same nonvolatile memory. The reference value is a value obtained by multiplying the reflectance R ₀ by the ratio k _i and further multiplying by a predetermined coefficient β (0 <β <1).

  In this specification, the “reflectance” of the optical disk represents the ratio of the output current of the photodetector to the output current of the front monitor.

  According to the present invention, it is possible to identify and detect the life of the laser diode, which is the main cause of the life of the optical disk drive, and the contamination of the objective lens and the optical disk, thereby improving the reliability of information recording and reproduction. it can.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 schematically shows a configuration of an optical disc apparatus according to an embodiment of the present invention. The linearly polarized laser beam 102 generated from the laser diode 101 is converted into a parallel beam by the collimator lens 103 and is incident on the polarization beam splitter 104. A polarization beam splitter is an optical element having a property of transmitting linearly polarized light in a certain direction with almost no loss and reflecting linearly polarized light in a direction perpendicular thereto with almost no loss. The polarizing beam splitter 104 in FIG. 1 is arranged so as to transmit the laser beam 102 generated from the laser diode 101 with almost no loss. The laser beam 102 that has passed through the polarization beam splitter 104 is reflected by the half mirror 105 and changes its direction vertically. The half mirror 105 transmits a small part of the incident laser light, and the transmitted laser light 102 is collected by the front monitor lens 106 and enters the front monitor 107. The front monitor 107 outputs a current proportional to the power of the incident laser beam. The current output from the front monitor is usually used to monitor the power output from the laser diode and perform power control. The laser beam 102 reflected by the polarization beam splitter 104 changes to circularly polarized light by passing through the λ / 4 plate 108. The laser beam 102 changed to circularly polarized light is condensed by the objective lens 109 and enters the optical disk 110.

  The laser beam 102 reflected by the information recording surface 111 of the optical disc passes through the objective lens 109 again and returns to linearly polarized light by passing through the λ / 4 plate 108. At this time, the polarization direction is perpendicular to the forward path. For this reason, after being reflected by the half mirror 105, it passes through the polarization beam splitter 104 with almost no loss. Thereafter, the laser light is collected by the detection lens 112 and enters the photodetector 113.

  Information recording is performed by changing the state of the information recording surface by the heat of the laser beam condensed by the objective lens. On the other hand, information is reproduced by reading a change in reflectance caused by a change in the state of the information recording surface with a laser beam condensed by an objective lens. A change in the reflectance of the information recording surface is detected as a change in the output current of the photodetector.

  The output current of the photodetector 113 becomes a reproduction signal by the reproduction signal generation circuit 114. The reproduction signal is subjected to signal processing such as waveform equalization processing in the signal processing circuit 115 of FIG. 1 and then converted into a binary signal in the decoding circuit 116. The binary signal is converted into data by the microprocessor 117 and sent to the host device. When recording data, the microprocessor 117 encodes the data sent from the higher-level device and generates a recording signal. The recording signal is sent to the laser drive circuit 118, and the current flowing through the laser diode 101 is modulated based on the recording signal. The state of information recording or reproduction is indicated by the status of the access lamp 121 or the like.

  Next, the drive life determination process in the embodiment of the present invention will be described with reference to the device configuration diagram of FIG. 1 and the flowchart of FIG. FIG. 3A shows a processing process at the time of drive shipment, and FIG. 3B shows a processing process at the time of drive operation.

First, with reference to FIG. 3A, processing at the time of drive shipment will be described.
(i) Step 301: Start Start processing.
(ii) Step 302: Learning of the Initial State of the Laser Diode The output current FM of the front monitor 107 is measured while changing the current I flowing through the laser diode 101, and these values are sequentially stored in the memory 119. The gradient IL ₀ (= ΔFM / ΔI) is calculated and stored in the nonvolatile memory 120 within a range where the relationship between I and FM is linear. This process is a process for fetching data for determining deterioration of the laser diode 101. The following processing is processing for taking in data for determining whether the objective lens or the optical disk is dirty.
(iii) Step 303: Learning of Reflectance of Reference Optical Disc This step is performed with the reference optical disc loaded in the drive. The laser diode 101 is made to emit light at a power about the reproduction power so as not to damage the information recording surface, the output current RF _{0 of the} photodetector 113 and the output current FM ₀ of the front monitor 107 are measured, and the ratio R ₀ ( = RF ₀ / FM ₀ ) is stored in the nonvolatile memory 120.
(iv) Step 304: Storage of reflectance data of existing optical disk For the optical disk on the market at the time of shipment of the drive, the relationship between the optical disk model and the reflectance ratio of the reference optical disk is tabulated as shown in FIG. , And stored in the nonvolatile memory 120. Here, as the type of the optical disk, a code indicating the manufacturer or optical disk type described in the control data of the optical disk may be used. The reflectance ratio with respect to the reference optical disk is measured by measuring the ratio R ₀ between the photodetector output current RF ₀ and the front monitor output current FM ₀ by mounting the reference optical disk with an arbitrary drive. Next, each type of optical disk is mounted, and the ratio R _i (= RF _i / FM _i ) (i: type of optical disk type) of the photodetector output current RF _i and the front monitor output current FM _i is measured. A ratio k _i (= R _i / R ₀ ) between R _i and R ₀ is calculated for each type of optical disc, and stored in the nonvolatile memory 120 together with a code for specifying the type of the optical disc. The data table created here can be used in common for all drives.
(v) Step 305: End The processing is ended.

Next, referring to FIG. 3B, processing during the drive operation will be described.
(i) Step 306: Start Start processing.
(ii) Step 307: Checking the laser diode While changing the current I flowing through the laser diode, the output current FM of the front monitor is measured, and these values are sequentially stored in the memory 119. The gradient IL ₁ (= ΔFM / ΔI) is calculated within a range where the relationship between I and FM is linear.
(iii) Step 308: laser diode deterioration determination gradient IL ₁ (= ΔFM / ΔI) is multiplied by the slope IL ₀ when drives shipped (= ΔFM / ΔI) in a predetermined coefficient alpha of (0 <α <1) value Determine if greater than. That is,
IL ₁ > α × IL ₀ (0 <α <1)
If yes, it is determined that the laser diode has not deteriorated, and the process proceeds to step 309. In the case of No, it is determined that the laser diode has deteriorated, and the process proceeds to step 312 to raise an alarm. The coefficient α may be determined in advance through experiments or the like.

  The process so far is a process of determining the deterioration of the laser diode and notifying when the deterioration is detected. Next, the process proceeds to a process for determining contamination of the objective lens or the optical disk.

(iv) Step 309: Discrimination of the optical disc type It is judged whether the reflectance data of the type of the optical disc currently loaded in the drive is in the nonvolatile memory 120. If yes, go to the next step. If it is No, it will progress to step 313 and will complete | finish a process. The type of the optical disk currently mounted in the drive is determined by reading the code indicating the manufacturer and optical disk type described in the control data of the optical disk.
(v) Step 310: Optical disk reflectivity check The ratio R ₁ (RF ₁ / FM ₁ ) between the output current RF _{1 of the} photodetector 113 and the output current FM ₁ of the front monitor 107 is measured.
(vi) Step 311: reflectance _{R 0 (RF 0 / FM 0} ) reflectivity deterioration determination reference optical disk, and nonvolatile memory 120 of the type of the optical disk, that are installed on the drive, the reflectance ratio k _i with respect to the reference optical disk Read from. Using the measured R ₁ , R ₀ , k _i read from the non-volatile memory, and a coefficient β (0 <β <1) determined in advance through experiments or the like
_{R 1> β × R 0 ×} k i (0 <β <1)
If it is Yes, it is determined that the objective lens and the optical disk are clean, and the process proceeds to step 313 to end the process. If No, it is determined that the objective lens or the optical disk is dirty, and the process proceeds to step 312 to activate an alarm.
(vii) Step 312: Alarm The user is warned that a recording / playback error may occur. If the process proceeds from step 308, an alarm indicating the deterioration of the laser diode is activated to prompt the user to repair or replace the drive. On the other hand, when the process proceeds from step 310, an alarm indicating that the objective lens or the optical disk is dirty is activated to prompt the user to clean the objective lens or the optical disk. As an alarm means, for example, an access lamp 121 provided to indicate the state of recording or reproducing information is used. The access lamp 121 blinks in different patterns depending on whether the laser diode is deteriorated or the objective lens or optical disk is dirty.
(viii) Step 313: End The processing is ended.

  In each of the above steps, the reflectance is measured in an area where no data is recorded for both the reference optical disc and each type of optical disc. The position of an area where data is not recorded or an area where data recording is prohibited is known in advance for each optical disc.

In the above embodiment, the alarm means is based on blinking of the access lamp, but other means may be used. For example, the color of the access lamp may be changed and turned on, or a buzzer sound may be emitted. Also, the contamination determination process of the objective lens or the optical disk has been provided to store the reflectance ratio k _i with respect to the reference optical disc and the reflectance R ₀ of the reference optical disk in the nonvolatile memory 120 to the optical disc of each type, each type of optical disc may be stored the value of R ₀ × value of k _i or β × R ₀ × k _i, against. Further, the order of the process for determining the deterioration of the laser diode and the process for determining the contamination of the objective lens or the optical disk may be reversed.

The figure which represents typically the structure of the optical disk apparatus of this invention. The figure showing the relationship between electric current and light emission power in a laser diode. The flowchart of the drive life determination process in the Example of this invention. The figure which shows the example of the reflectance data table of the existing optical disk.

Explanation of symbols

101: Laser diode 102: Laser beam 103: Collimating lens 104: Polarizing beam splitter 105: Half mirror 106: Front monitor lens 107: Front monitor 108: λ / 4 plate 109: Objective lens 110: Optical disk 111: Information recording surface 112: Detection lens 113: photodetector 114: reproduction signal generation circuit 115: signal processing circuit 116: decoding circuit 117: microprocessor 118: laser driving circuit 119: memory 120: nonvolatile memory 121: access lamp

Claims (12)

A laser diode for generating laser light;
A laser driving circuit for adjusting a power of the laser beam by controlling a current passed through the laser diode;
A front monitor that receives a portion of the generated laser light and generates an output proportional to the power of the laser light;
An objective lens for condensing the laser beam on an optical disc;
A photodetector that receives the laser beam reflected by the optical disc and generates an output proportional to the power of the reflected laser beam;
An optical disc apparatus, wherein a warning is displayed when a rate of change of an output level of the front monitor with respect to a change of a current flowing through the laser diode is smaller than a predetermined reference value.   2. The optical disk apparatus according to claim 1, wherein the reference value is a predetermined coefficient α (0 <α <) for a rate of change of the output level of the front monitor with respect to a change in current flowing through the laser diode measured at the time of shipment of the optical disk apparatus. 1. An optical disc apparatus characterized by being multiplied by 1).   2. The optical disk apparatus according to claim 1, further comprising a storage unit that stores the reference value.   2. The optical disk device according to claim 1, further comprising an access lamp for indicating a state of recording or reproducing information, wherein the warning is displayed by lighting the access lamp in a predetermined pattern. apparatus. A laser diode for generating laser light;
A laser driving circuit for adjusting a power of the laser beam by controlling a current passed through the laser diode;
A front monitor that receives a portion of the generated laser light and generates an output proportional to the power of the laser light;
An objective lens for condensing the laser beam on an optical disc;
A photodetector that receives the laser beam reflected by the optical disc and generates an output proportional to the power of the reflected laser beam;
Means for detecting the type of the mounted optical disc,
When the laser beam is focused on an area where the data of the mounted optical disk is not recorded, the ratio R ₁ between the output of the photodetector and the output of the front monitor is compared with the optical disk of the detected type. An optical disc apparatus that displays a warning if it is smaller than a predetermined reference value.   6. The optical disk apparatus according to claim 5, further comprising a storage unit that stores the reference values for a plurality of optical disks of different types. 6. The optical disc apparatus according to claim 5, wherein a ratio k _i (i is a type of optical disc type) of reflectances of various known optical discs of different types and reference optical discs, and the light detection when the reference optical disc is mounted. a storage unit which stores a ratio R ₀ of the outputs of said front monitor vessels, the ratio k for the optical disk to the ratio R ₁ has mounted with the ratio R ₀ that is stored in the storage unit An optical disc apparatus, wherein the warning is displayed when the product of _i is smaller than a value obtained by multiplying a predetermined coefficient β (0 <β <1).   6. An optical disc apparatus according to claim 5, further comprising an access lamp for indicating a state of recording or reproducing information, wherein the warning is displayed by lighting the access lamp in a predetermined pattern. apparatus. A laser diode for generating laser light;
A laser driving circuit for adjusting a power of the laser beam by controlling a current passed through the laser diode;
A front monitor that receives a portion of the generated laser light and generates an output proportional to the power of the laser light;
An objective lens for condensing the laser beam on an optical disc;
A photodetector that receives the laser beam reflected by the optical disc and generates an output proportional to the power of the reflected laser beam;
Means for detecting the type of the mounted optical disc,
When the rate of change of the output level of the front monitor with respect to the change of the current flowing through the laser diode is smaller than a first reference value, it is determined that the laser diode has deteriorated,
When the laser beam is focused on an area where the data of the mounted optical disk is not recorded, the ratio R ₁ between the output of the photodetector and the output of the front monitor is compared with the optical disk of the detected type. An optical disc apparatus, wherein the objective lens or the optical disc is judged to be dirty if it is smaller than a predetermined second reference value. 10. The optical disk apparatus according to claim 9, wherein the first reference value is a predetermined coefficient α (0) for a rate of change of the output level of the front monitor with respect to a change in current flowing through the laser diode measured at the time of shipment of the optical disk apparatus. <Α <1), and the second reference value is the light when the reference optical disk is mounted on the ratio k _i of the reflectance of the detected optical disk to the reflectance of the reference optical disk. An optical disc apparatus characterized by a value obtained by multiplying a value R ₀ between the output of the detector and the output of the front monitor and a predetermined coefficient β (0 <β <1).   10. The optical disk apparatus according to claim 9, wherein a warning is displayed by a method capable of discriminating between the determination that the laser diode is deteriorated and the determination that the objective lens or the optical disk is dirty. An optical disc apparatus characterized by:   10. The optical disk apparatus according to claim 9, further comprising an access lamp for indicating a state of recording or reproducing information, wherein the warning indication is displayed when the laser diode is determined to be deteriorated, the objective lens or An optical disc apparatus, wherein the access lamp is turned on in a different pattern when it is determined that the optical disc is dirty.

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