JP2010061714A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a frequency of an operation defect of an optical disk device caused by to deterioration with the passage of time of a laser element, and to enhance reliability as the optical disk device. <P>SOLUTION: Laser elements 101a and 101b having the same wavelength bands are disposed in a semiconductor laser 101 and the switching of the laser elements is performed by a laser driving circuit 200. The switching of the laser elements is performed by determining e.g. the life of the laser elements. The laser driving circuit 200 performs the power control (APC) of the laser elements 101a and 101b so that an output from a front monitor 104 is made to be a prescribed value. When a driving current value Id applied when APC is stabilized exceeds a threshold Ish, it is determined that the laser elements 101a and 101b reach the life. The usage of the laser element reaching the life is stopped and switching to a usable laser element is performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical disk device, and is particularly suitable for use in extending the life of an optical disk device.

  In recent years, the use of optical disk devices has been increasing. As the capacity of optical discs has increased, various optical disc devices such as DVD (Digital Versatile Disc) drives and Blu-ray disc drives have been commercialized.

  However, when the optical disk apparatus is driven for a long period of time, malfunction may occur. Many of the causes of the malfunction are due to optical damage (COD: Catastrophic Optical Damage) that destroys the end face of the laser element of the optical pickup device. In other words, the laser element deteriorates with time and reaches the end of its life, resulting in malfunction of the optical disc apparatus. In particular, an optical disk device used in car navigation is often driven at a high temperature for a long time, and is likely to malfunction due to deterioration over time.

  In the repair when such a malfunction occurs, it is practically impossible to replace only the laser element. Therefore, conventionally, it has been necessary to replace the optical pickup device including the laser element. However, if the entire optical pickup device is replaced, the number of parts to be replaced increases, which causes a problem of increasing costs.

Therefore, there is a method of replacing only the light source unit including the laser element instead of replacing the optical pickup device (Patent Document 1).
JP 7-334862 A

  However, in the method of replacing the light source unit including the laser element, an increase in cost due to repair can be suppressed, but the frequency of malfunction due to deterioration of the laser element over time cannot be reduced. In addition, there is a problem that the replacement of the light source unit requires complicated work.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical disc apparatus that can reduce the frequency of malfunction due to deterioration with time without requiring complicated work, thereby improving reliability. And

  The present invention relates to an optical disc apparatus having an optical pickup device and a circuit system for controlling the optical pickup device. Among these, the optical pickup device includes a laser light source having a plurality of laser elements that emit laser light of the same wavelength band, an objective lens that converges the laser light emitted from each laser element on a disk, A photodetector having a photodetecting portion for receiving a corresponding laser beam out of the laser beams emitted from the laser element, and guiding the laser light emitted from each of the laser elements to the objective lens and reflecting by the disk And an optical system that guides the laser beam to the photodetector. The circuit system includes a drive unit that drives the laser elements and a switching unit that switches the laser elements to be driven.

  According to the optical disk apparatus of the present invention, since the plurality of laser elements are switched by the switching unit, the life of the semiconductor laser can be extended as compared with the case where a semiconductor laser having one laser element is used. As a result, the frequency of malfunctions can be reduced, and the reliability as an optical disc apparatus can be improved.

  In the optical disk device according to the present invention, the optical pickup device may include a plurality of light detection units that individually receive the laser beams emitted from the plurality of laser elements.

  Further, in the optical disk device according to the present invention, the optical pickup device is emitted from the second laser element to a light detection unit that receives laser light emitted from the first laser element among the plurality of laser elements. It can be set as the structure provided with the optical path changing element which makes a laser beam enter. In this case, each laser beam emitted from the first laser element and the second laser element can be received by the common light detection unit, and the configuration of the light detection unit can be simplified.

  In the optical disk device according to the present invention, the circuit system may include a life determination unit that determines the life of the laser element. At this time, the switching unit can be configured to set the laser element to be driven based on a determination result by the life determination unit.

  In the optical disc apparatus according to the present invention, the circuit system includes an adjustment unit that adjusts a drive current value of the laser element to be driven based on a light amount of the laser light emitted from the laser element to be driven. It can be configured. At this time, the lifetime determination unit can be configured to determine the lifetime of the laser element to be driven based on the drive current value of the laser element to be driven adjusted by the adjustment unit.

  In the optical disk device according to the present invention, the circuit system may include a usage time determination unit that determines a usage time of the laser element to be driven. At this time, the switching unit can be configured to set the laser element to be driven based on a determination result by the usage time determination unit.

  In the optical disc apparatus according to the present invention, the circuit system may include a use history determination unit that determines which of the plurality of laser elements was used last time. At this time, the switching unit can be configured to set the laser element to be driven based on a determination result by the use history determination unit.

  As described above, according to the present invention, it is possible to provide an optical pickup device and an optical disc device that can improve reliability by reducing the frequency of malfunction due to deterioration over time without requiring complicated work.

The effects and significance of the present invention will become more apparent from the following description of embodiments. However, the following embodiment is merely an example when the present invention is put into practice, and the present invention is not limited to what is described in the following embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In the present embodiment, the present invention is applied to an optical disc apparatus capable of reproducing with respect to the same type of disc using laser light of the same wavelength band.

<Example>
FIG. 1 shows the configuration of the optical system of the optical pickup device according to the embodiment. In the figure, for convenience of explanation, the circuit side configuration (laser drive circuit 200) is also shown.

  The semiconductor laser 101 accommodates laser elements 101a and 101b in the same CAN. The laser elements 101a and 101b are disposed close to each other in the X-axis direction and emit laser light having the same wavelength. The arrangement of each laser element will be described later with reference to FIG.

  The laser driving circuit 200 performs switching so as to use only one of the laser elements 101a and 101b, and drives the laser element to be used. The drive terminals 200a and 200b and the ground terminal 200c are used for flowing a drive current. The terminal connection will be described later with reference to FIG. 2, and the operation will be described later with reference to FIG.

  As described above, only one of the laser elements 101a and 101b is used. That is, one laser beam is emitted from the semiconductor laser 101 by driving the laser element 101a or the laser element 101b. In FIG. 1, for convenience, both laser light paths are shown.

  The laser light emitted from the semiconductor laser 101 is split by the three-beam diffraction grating 102 into three beams of 0th-order diffracted light that is a main beam and ± 1st-order diffracted light that is a sub-beam.

  The half mirror 103 reflects and transmits the incident laser light at a ratio of 50%. As a result, the laser light transmitted through the half mirror 103 enters the front monitor 104. On the other hand, the laser beam reflected by the half mirror 103 is converted in the traveling direction to the Z-axis direction by the rising mirror 105 and guided to the collimator lens 106, the objective lens (not shown), and the optical disc (not shown). It is burned. The collimator lens 106 is displaced in the laser optical axis direction by a lens actuator (not shown). As the collimator lens 106 is displaced, the aberration generated in the laser light is corrected.

  The laser light applied to the optical disk is reflected by the recording layer disposed on the optical disk. The reflected laser light travels back along the optical path and then enters the half mirror 103 again.

  Here, since the half mirror 103 is a parallel plate and the incident laser light is convergent light, astigmatism is introduced into the transmitted laser light. The laser beam that has passed through the half mirror 103 subsequently enters the astigmatism plate 107, where astigmatism is also introduced. An appropriate astigmatism is introduced into the laser beam by the half mirror 103 and the astigmatism plate 107 and guided to the photodetector 108.

  The photodetector 108 receives the laser beam that has passed through the astigmatism plate 107 and outputs a detection signal. The configuration of the photodetector 108 will be described later with reference to FIG.

  FIG. 2A shows the semiconductor laser 101 as viewed from the Y-axis direction, that is, from the three-beam diffraction grating 102 side. In the CAN, laser elements 101a and 101b are arranged as shown. The electrodes 101c and 101d are connected to drive terminals 200a and 200b of the laser drive circuit 200, respectively. The electrode 101e is connected to the ground terminal 200c of the laser driving circuit 200. When a drive current is supplied from the drive terminals 102a and 102b, the laser elements 101a and 101b emit laser light with a corresponding power.

  FIG. 4B is a view of the photodetector 108 as viewed from the X-axis direction, that is, from the astigmatism plate 107 side. As shown in the figure, the photodetector 108 is provided with photodetectors 108a and 108b in the Y-axis direction. The light detection unit 108a includes quadrant sensors 108c, 108d, and 108e, and the light detection unit 108b includes quadrant sensors 108f, 108g, and 108h. The quadrant sensors 108c to 108e and 108f to 108h are arranged in the Z-axis direction in the light detection units 108a and 108b, respectively.

  Laser light emitted from the laser elements 101a and 101b is received by the light detection units 108a and 108b, respectively. The arrangement of the photodetectors 108 is adjusted in advance so that the optical axes of the laser elements 101a and 101b coincide with the centers of the four-divided sensors 108d and 108g, respectively, so that an appropriate amount of received light can be obtained in each of the photodetectors. Has been.

  Further, the four-divided sensors 108c to 108e on the light detection unit 108a receive the laser light (main beam / sub beam) of the laser element 101a that has been converted into three beams by the three-beam diffraction grating 102, one beam at a time. Similarly, the four-divided sensors 108f to 108h on the light detection unit 108b receive one beam of laser light (main beam / sub beam) of the laser element 101b that is converted into three beams by the three-beam diffraction grating 102.

  A reproduction signal by the laser beam of the laser element 101a is generated from an output signal of the quadrant sensor 108d. Similarly, the reproduction signal by the laser beam of the laser element 101b is generated from the output signal of the quadrant sensor 108g.

  A focus error signal and a tracking error signal due to the laser beam of the laser element 101a are generated from output signals of the four-divided sensors 108c to 108e. Similarly, the focus error signal and the tracking error signal due to the laser beam of the laser element 101b are generated from the output signals of the four-divided sensors 108f to 108h. The focus error signal is generated by the differential astigmatism method, and the tracking error signal is generated by the differential push-pull method.

  FIG. 3 is a diagram showing a main configuration of the optical disc apparatus. As illustrated, the optical disc apparatus includes an optical pickup device 20, a laser drive circuit 200, a signal calculation circuit 201, a reproduction circuit 202, a servo circuit 203, and a memory 205.

  The optical pickup device 20 includes an optical system excluding the laser drive circuit 200 in the configuration shown in FIG. The actuator 111 displaces an objective lens (not shown) in the focus direction and the tracking direction in the optical pickup device 20. Thereby, the laser beam is appropriately converged and positioned with respect to the irradiation target.

  The laser drive circuit 200 receives the reproduction command input from the controller 204 and drives the semiconductor laser 101. That is, one of the laser elements 101a and 101b in the semiconductor laser 101 is selected, and the selected laser element is driven so as to emit laser light at a predetermined power while referring to the output of the front monitor 104. The laser element emission power adjustment process and the laser element selection process will be described later with reference to FIGS.

  The memory 205 is a nonvolatile memory that stores information necessary for driving the laser driving circuit 200. Specific storage information will be described with reference to FIG.

  The signal arithmetic circuit 201 performs arithmetic processing on the output signal of the photodetector 108 arranged in the optical pickup device 20 to generate a reproduction signal, a focus error signal, and a tracking error signal, and outputs them to corresponding circuits, respectively. To do.

  The reproduction circuit 202 demodulates and reproduces the reproduction signal input from the signal arithmetic circuit 201 to generate reproduction data, and outputs this to a subsequent circuit (not shown).

  The servo circuit 203 generates a focus servo signal and a tracking servo signal based on the focus error signal and tracking error signal input from the signal calculation circuit 201 and supplies them to the actuator 111. The servo circuit 203 monitors the reproduction signal input from the signal arithmetic circuit 201 and controls the collimator lens 106 so that the reproduction signal becomes the best. Further, the servo circuit 203 controls the rotation of the spindle motor of the optical disc 10 in response to a command from the controller 204.

  FIG. 4 is a diagram illustrating the operation of the laser driving circuit 200. In FIG. 5A, the laser drive circuit 200 adjusts the emission power of the laser element 101a or 101b (hereinafter referred to as APC) and determines whether the used laser element has reached the end of its life. It is a flowchart showing this.

  In S101, the target front monitor output It and the threshold value Ish are read from the built-in memory. The built-in memory stores values of It and Ish as shown in FIG. The target front monitor output It is an amount of light received by the front monitor 104 when the laser element to be used emits a laser light amount optimum for reading the disk information. The threshold value Ish will be described in S105 of the flowchart.

  Since It and Ish are eigenvalues, the built-in memory is used as a storage location. However, it can be stored in the memory 205 as in a life determination memory described later.

  In S102, APC is executed in the laser element to be used so that the output of the front monitor 104 becomes It.

  In S103, it is determined whether or not the APC is stable. If the APC is not stable (S103: NO), the process proceeds to S104 after waiting until it is stabilized. Whether APC has stabilized is determined, for example, based on whether a predetermined period (a period sufficient to stabilize) has elapsed since the start of APC execution.

  In S104, when the APC is completed, the drive current value Id of the laser element being used is obtained.

  In S105, Id and Ish are compared in size. If Id is large, it is determined that the laser element being used has reached the end of life, and the process proceeds to S106. If Id is equal to or less than Ish, the laser element being used has reached the end of its life. It judges that it is not, and ends.

  The threshold value Ish is a current value used to determine whether the laser element to be used has reached the end of its life. That is, in order to obtain It as the output of the front monitor 104, when an excessively large drive current is required for the laser element, it can be determined that the laser element has been deteriorated and has reached its lifetime. The threshold value Ish is a current value used for determining whether or not the drive current of the laser element is excessively large.

  FIG. 4D is a graph showing the relationship between the total drive time of the laser element and the drive current value Id necessary for realizing the target front monitor output It. As shown in the figure, the drive current value Id increases according to the total drive time of the laser element. That is, when the total drive time of the laser element becomes longer, the deterioration of the laser element proceeds and the required drive current value increases. When the drive current value Id exceeds the threshold value Ish, it can be determined that the laser element has reached the end of its life.

  In S106, the fact that the laser element being used has reached the end of its life is written in the life determination memory. The life determination memory is in the memory 205, and the content to be written is a flag using 0 or 1 as shown in FIG. That is, in the laser elements 101a and 101b, “0” is stored when the lifetime is not reached, and “1” is stored when the lifetime is reached, thereby storing whether the lifetime is reached.

  In general, it is known that the current value of a laser element varies depending on the amount of heat generated. That is, since the current of the laser element to be used is also changed by the heat generation of the laser elements 101a and 101b, the actuator 111, etc., the drive for obtaining the target front monitor output It is performed even if the total drive time of the laser elements is the same. A difference occurs in the current value Id, resulting in an error in the life determination.

  In order to reduce such errors, a temperature sensor is placed in a location where the temperature can be detected appropriately in the housing (housing), and after performing the calculation to correct the fluctuation of the current of the laser element due to the measured temperature, the above-mentioned lifetime If the determination is made, a more accurate life determination can be realized. Examples of the location of the temperature sensor include the periphery of the semiconductor laser 101 and the actuator 111.

  Next, a method for switching the laser elements 101a and 101b in the laser driving circuit 200 will be described.

  FIG. 5 is a diagram showing a case where only one of the laser elements 101a and 101b is always used until the end of its lifetime.

  In S201, the life determination memory in the memory 205 is referred to and it is checked whether the laser element 101a has reached the life. If the laser element 101a has reached the end of its life, the process proceeds to S204 without using the laser element 101a. If the laser element 101a has not reached the end of its life, the process proceeds to S202.

  In S202, the laser element 101a is used to perform APC execution and lifetime determination shown in FIG.

  In S203, if it is determined that the laser element 101a has reached the lifetime by the APC execution and the lifetime determination in the previous step S202, use of the laser element 101a is stopped and the process proceeds to S204. If it is determined that the lifetime has not been reached, the process returns to S202 to continue using the laser element 101a.

  In S204 to S206, the laser element 101b performs the same operation as S201 to S203. That is, in S204, it is checked whether the laser element 101b has reached the end of its life. If it has not reached the end of life (S204: NO), the APC execution and life determination shown in FIG. (S205).

  The laser element 101b continues to be used until it is determined in S206 that the lifetime has been reached. If it is determined in S206 that the laser element 101b has reached the end of its life, the process ends. That is, both the laser elements 101a and 101b reach the end of their lives, and the laser pickup as a whole cannot be used continuously.

  As described above, according to the present embodiment, since the above-described switching is performed using the two laser elements 101a and 101b, the laser element is approximately twice that when the semiconductor laser 101 having one laser element is used. Lifespan is obtained. Therefore, it is possible to suppress a decrease in the life of the optical disk device due to the end of the life of the laser element, and as a result, it is possible to improve the reliability of the optical disk device.

  Further, since the laser element is installed in the semiconductor laser 101, high reliability can be realized without increasing the number of parts as an optical pickup device, and the cost increase can be suppressed to a minute. In addition, since the lifetime of the laser element as a whole of the optical pickup device is extended, the frequency of parts replacement due to failure is reduced, so that the product is environmentally friendly.

<Modification 1>
Below, the case where the switching method of the laser elements 101a and 101b in an Example is changed variously from the method shown in FIG. 5 is demonstrated.

  FIG. 6 is a diagram showing a case where the laser element to be used is switched every time it is started.

  In S301, the memory 205 is referred to and information on which laser element was used at the time of the previous activation is obtained. As shown in FIG. 5B, the memory 205 stores information on the laser element used last time in addition to the above-mentioned life determination memory. The written contents are flags using 0 or 1 as shown in FIG. That is, “1” is stored in the laser element used last time, and “0” is stored in the laser element not used last time, so that the last used laser element is stored.

  In S302, if the laser element used last time is the laser element 101a, the process proceeds to S306, and if it is not the laser element 101a, the process proceeds to S303.

  In S303, the lifetime determination memory is referred to and it is determined whether the laser element 101a has reached the lifetime. If the life has been reached, the process proceeds to S306, and if the life has not been reached, the process proceeds to S304.

  In S304, using the laser element 101a, APC execution and life determination are performed as shown in FIG.

  In S305, if it is determined that the laser element 101a has reached the lifetime by the APC execution and the lifetime determination in the previous step S304, use of the laser element 101a is stopped and the process proceeds to S306. If it is determined that the lifetime has not been reached, the process returns to S304 to continue using the laser element 101a.

  In S306 to S308, the laser element 101b performs the same operation as S303 to S305. That is, first, in S306, it is checked whether the laser element 101b has reached the end of its life.

  If it is determined in S306 that the laser element 101b has reached the end of life (S306: YES), the process proceeds to S309. If it is determined that the life has not been reached (S306: NO), the process proceeds to S307. APC execution and life determination shown in 4 (a) are performed. If it is determined in S308 that the laser element 101b has reached the end of its life, the process returns to S303.

  In step S309, the lifetime determination memory is referred to and it is determined whether the laser element 101a has reached the lifetime. If the laser element 101a has not reached the lifetime, the process returns to S303, and if the lifetime has been reached, the process ends.

  At the end of the operation of the optical pickup device, information on the laser element used this time is written in the memory 205. That is, “1” is written in the flag corresponding to the laser element used at the end, and “0” is written in the flag corresponding to the laser element used last time.

  Since the laser element 101b is determined to have a lifetime at the time of proceeding to S309 (S306: YES), if the laser element 101a is determined to have a lifetime in S309 (S309: YES), both of the laser elements 101a and 101b are lifetimes. As a result, the entire optical pickup cannot be used continuously.

  According to the modified example of FIG. 6, since switching is performed as described above using two laser elements 101a and 101b, the semiconductor laser 101 having one laser element is used as in the above embodiment. The lifetime of the laser element can be approximately doubled. Therefore, it is possible to suppress a decrease in the life of the optical disk device due to the end of the life of the laser element, and as a result, it is possible to improve the reliability of the optical disk device.

  FIG. 7 is a diagram showing a case where the laser element to be used is switched at regular time intervals. The basic operation is the same as the switching process of FIG. In the processing flow of FIG. 7, steps S321, S322, S323, and S324 are added compared to FIG. In the following description, these added steps will be described, and description of the other steps will be omitted.

  In S321 and S323 in FIG. 5A, a timer is started to measure the usage time of the laser elements 101a and 101b. That is, at the start of use of the laser element, the timer measurement time T is reset to T = 0 and time measurement is started.

  In S322 and S324, if the measurement time T exceeds the predetermined time T0, the use of the laser element being used is stopped and the process proceeds to the next step. That is, in S322, when it is determined that the measurement time T has exceeded the predetermined time T0 (S322: YES), the process proceeds to S306 to perform a process of switching the laser element to be used to the laser element 101b. In S324, the measurement time T If it is determined that T has exceeded the predetermined time T0 (S324: YES), the process proceeds to S303 to perform a process of switching the laser element to be used to the laser element 101a.

  As in FIG. 6, at the end of the operation of the optical pickup device, information on the laser element used this time is written in the memory 205. That is, “1” is written in the flag corresponding to the laser element used at the end, and “0” is written in the flag corresponding to the laser element used last time.

  With the above operation, as in the above-described embodiment, the life of the laser element approximately twice that when using one laser element can be obtained, so that the reliability of the optical pickup and the optical disk apparatus can be improved.

  FIG. 8 is a diagram showing a case where the laser element is always started from one laser element at the time of start-up, and the laser element to be used is switched at regular intervals during use. Although the basic operation is the same as the switching flow of FIG. 7, in the processing flow of FIG. 8, it is not necessary to check the laser element used last time when starting use, so S301 and S302 in the processing flow of FIG. 7 are omitted. Yes.

  Unlike the processing flow of FIG. 7, since use is always started from one laser element at the time of startup, it is not necessary to write the laser element used at the end of the operation of the optical pickup device.

  Also in this case, as in the above-described embodiment, the life of the laser element is approximately twice that of the case where one laser element is used, so that the reliability of the optical pickup and the optical disk apparatus can be improved.

<Modification 2>
Below, the example of a change of the optical system in the said Example is demonstrated. In the above embodiment, the laser beams emitted from the laser elements 101a and 101b are reflected by the optical disc 10 and then received by the light detection units 108a and 108b, respectively. On the other hand, in this modified example, light is received by one light detection unit.

  FIG. 9A is a diagram in which a step type diffraction grating 112 is installed between the astigmatism plate 107 and the photodetector 108. FIG. 2B is an enlarged view of the step type diffraction grating 112. The photodetector 108 includes only the photodetector 108a out of the two photodetectors 108a and 108b.

  In FIG. 6A, the optical system is set so that the laser beams of the laser elements 101a and 101b incident from the astigmatism plate 107 side are incident on the light detection unit 108a by the diffractive action of the step type diffraction grating 112. ing. That is, the lattice pattern interval W shown in FIG. 5B is appropriately set so that the + 1st order light of the laser light from the laser element 101b is incident on the light detection unit 108a. As the laser light of the laser element 101a, zero-order light that is not diffracted by the step type diffraction grating 112 is incident on the light detection unit 108a.

  The light amounts of the 0th-order light and the + 1st-order light of the laser element 101b incident on the light detection unit 108a are reduced from the laser light amount of the laser element 101b before being incident on the step type diffraction grating 112, but the step height of the grating pattern It can be adjusted by H. When the step height H of the grating pattern is adjusted to increase the amount of + first-order light of the laser element 101b, the amount of zero-order light of the laser element 101a decreases. The height H of the step type diffraction grating 112 is adjusted so that the light amount of the + 1st order light of the laser element 101b and the light amount of the 0th order light of the laser element 101a are substantially equal.

  FIG. 7C is a diagram showing a configuration example when a blazed diffraction grating 113 is installed instead of the step type diffraction grating 112.

  Similarly, when the blazed diffraction grating 113 is used, the laser light of the laser elements 101a and 101b can be received only by the light detection unit 108a if the optical system is appropriately set.

  When the blazed diffraction grating 113 is used, the −1st order light can be prevented from being generated, and therefore the light amounts of the 0th order light and the + 1st order light can be increased as compared with the case where the step type diffraction grating 112 is used. . Therefore, the laser light from the laser element 101a and the laser light from the laser element 101b can be more efficiently guided to the light detection unit 108a. Also in this case, the height H of the blazed diffraction grating 113 is adjusted so that the light amount of the + 1st order light of the laser element 101b and the light amount of the 0th order light of the laser element 101a are substantially equal.

  FIG. 10 is a diagram illustrating a modified example of the arrangement method of the step type diffraction grating 112. This modification can be applied to the case where the processing flow of FIG. 5 is used, that is, the case where the laser element 101a is continuously used until the end of its lifetime.

  In the processing flow of FIG. 5, the switching from the laser element 101a to the laser element 101b is performed after the laser element 101a reaches the end of its life. At this time, a position shift may occur in the light detection unit 108a due to deterioration of the adhesive or the like until the laser element 101a reaches the end of its life. Such a tendency of misalignment can be determined using results of an acceleration test or the like.

  In the case of FIG. 10, the light detection unit 108a is shifted by Δd1 in the Y-axis direction until the laser element 101a reaches the end of its life. For this reason, when the step type diffraction grating 112 is installed so that the + 1st order light of the laser element 101b is properly incident on the light detection unit 108a as in the case of FIG. 9A, the laser element to be used is the laser element. At the time of switching from 101a to the laser element 101b, the + 1st order light of the laser element 101b is not properly incident on the light detection unit 108a. Further, if the laser element 101b continues to be used thereafter, further positional displacement occurs in the light detection unit 108a until the laser element 101b reaches the end of its life, and laser light (+1) from the laser element 101b with respect to the light detection unit 108a The positional deviation of (next light) becomes larger.

  In this modified example, the laser light (+ 1st order light) from the laser element 101b is detected by the light detection unit 108a when the light detection unit 108a is displaced by Δd1 so as to cope with the positional deviation of the light detection unit 108a. In advance, the diffraction grating 112 is shifted by Δd2 in the X-axis direction so as to be appropriately incident on the X-axis. Thus, at the time when the laser element to be used is switched from the laser element 101a to the laser element 101b, the laser light (+ 1st order light) from the laser element 101b can be appropriately incident on the light detection unit 108a.

  Further, when the blazed diffraction grating 113 is used (not shown), the same effect can be obtained if the diffraction grating 113 is shifted in advance so as to cope with the positional deviation of the light detection unit 108a. .

  As described above, when the step type diffraction grating 112 and the blazed diffraction grating 113 are used, the laser light can be received by one light detection unit while realizing the effects described in the embodiment, and the configuration of the light detector can be achieved. It can be simplified. Furthermore, if the step-type diffraction grating 112 and the blazed diffraction grating 113 are arranged as described with reference to FIG. 10, it is possible to prevent the laser beam from being appropriately received due to the positional deviation of the light detection unit. .

  As mentioned above, although the Example and modification of this invention were demonstrated, this invention is not restrict | limited at all to the said Example and modification, Moreover, a various change besides the above is also possible for the Example of this invention. is there.

  For example, in the above description, two laser elements are arranged in the same CAN. However, three or more laser elements may be arranged in the same CAN. For example, when three laser elements are arranged, three photodetectors are also arranged in the photodetector 108 corresponding to each laser element. Alternatively, the laser light from the three laser elements may be received by a common light detection unit using a step type diffraction grating or a blaze type diffraction grating as in the case of FIG. 9 or FIG. In this case, the three laser beams are received by one photodetection unit, and two of the three laser beams are received by one photodetection unit, and the other one is received by the other photodetection unit. May be.

  In FIG. 10, the diffraction gratings are shifted in advance so as to correspond to the positional deviation of the light detection unit. However, as in the above-described embodiment, the laser light is received by each of the light detection units. It is possible to deal with the positional deviation of the detection unit. That is, at the start of use of laser light that will be used later, the light detector may be arranged in advance so that the optical axis of the laser light overlaps the center of the light detector that receives the laser light.

  Further, in the above, if it is determined that the laser element has reached the lifetime even once in the lifetime determination, it is determined that the lifetime is always reached in the subsequent steps, but the lifetime has been reached a certain number of times. The life determination may be retried until it is determined. For example, in FIG. 4A, the total number of times that the laser element being used has reached the step of S106 is counted, and the laser element being used in the lifetime determination memory reaches the lifetime only when the count reaches a certain value. You may make it write what has been reached.

  Alternatively, the life determination may be retried for a certain period after it is determined for the first time that the laser element being used has reached the end of its life. For example, in FIG. 4A, even if the laser element being used reaches the step of S106 for the first time, the laser element being used in the lifetime determination memory has a lifetime within a certain period even if it reaches the step of S106. You may not write something.

  In the above description, the astigmatism action introduced into the laser beam is adjusted using the astigmatism plate 107, but the astigmatism action by the half mirror 103 is omitted by omitting the astigmatism plate 107. Astigmatism may be introduced into the laser beam. In this case, it is necessary to adjust the arrangement of the light detection units 108a and 108b on the light detector 108 according to the direction of occurrence of astigmatism.

  Further, in the above description, APC is performed based on the light amount detected by the front monitor 104. However, APC is performed based on the light amount detected by the monitor PD disposed in the semiconductor laser 101. May be. In this case, the monitor PD may be individually arranged corresponding to the laser elements 101a and 101b, or the laser light emitted backward from the laser elements 101a and 101b is received by the common monitor PD. You may do it. Further, APC may be performed based on the amount of light received by the light detection units 108a and 108b. For example, when APC is performed on the laser element 101a, APC is performed based on a signal obtained by adding the outputs from the three quadrant sensors 108c to 108e constituting the light detection unit 108a.

  In addition, the embodiment of the present invention can be variously modified as appropriate within the scope of the technical idea shown in the claims.

The figure which shows the structure of the optical pick-up apparatus which concerns on an Example. The figure which shows the structure of the semiconductor laser which concerns on an Example, and a photodetector The figure which shows the principal part structure of the optical disk apparatus based on an Example. The figure explaining APC execution and life judgment concerning an example The figure explaining the switching method of the laser element which concerns on an Example The figure explaining the example of a change of the switching method of the laser element of an Example The figure explaining the example of a change of the switching method of the laser element of an Example The figure explaining the example of a change of the switching method of the laser element of an Example The figure which shows the example of a change of the optical system of an Example The figure which shows the example of a change of the optical system of an Example

Explanation of symbols

200: Laser drive circuit (drive unit, switching unit, life determination unit, adjustment unit, usage time determination unit, usage history determination unit)
101 ... Semiconductor laser (laser light source)
DESCRIPTION OF SYMBOLS 101a ... Laser element 101b ... Laser element 108 ... Photodetector 108a ... Photodetection part 108b ... Photodetection part 10 ... Optical disk 20 ... Optical pick-up apparatus 112 ... Step type diffraction grating (optical path changing element)
113… Blaze type diffraction grating (optical path changing element)

Claims (7)

In an optical disc apparatus having an optical pickup device and a circuit system for controlling the optical pickup device,
The optical pickup device;
A laser light source having a plurality of laser elements emitting laser light of the same wavelength band;
An objective lens for converging the laser beam emitted from each of the laser elements on the disk;
A photodetector having a photodetection unit that receives a corresponding laser beam among the laser beams emitted from the laser elements;
An optical system that guides the laser light emitted from each laser element to the objective lens and guides the laser light reflected by the disk to the photodetector;
The circuit system is:
A drive unit for driving each of the laser elements;
A switching unit that switches the laser element to be driven,
An optical disc device characterized by the above. The optical disc apparatus according to claim 1,
The optical pickup device includes a plurality of light detection units that individually receive the laser beams emitted from the plurality of laser elements,
An optical disc device characterized by the above. The optical disc apparatus according to claim 1,
The optical pickup device is:
An optical path changing element that causes the laser beam emitted from the second laser element to be incident on a light detection unit that receives the laser beam emitted from the first laser element among the plurality of laser elements;
An optical disc device characterized by the above. The optical disc apparatus according to any one of claims 1 to 3,
The circuit system includes a lifetime determination unit that determines the lifetime of the laser element,
The switching unit sets the laser element to be driven based on a determination result by the life determination unit.
An optical disc device characterized by the above. The optical disk apparatus according to claim 4, wherein
The circuit system includes an adjustment unit that adjusts a drive current value of the laser element to be driven based on a light amount of the laser light emitted from the laser element to be driven,
The lifetime determination unit determines the lifetime of the laser element to be driven based on the drive current value of the laser element to be driven adjusted by the adjustment unit.
An optical disc device characterized by the above. In the optical disc device according to any one of claims 1 to 5,
The circuit system includes a usage time determination unit that determines a usage time of the laser element to be driven,
The switching unit sets the laser element to be driven based on a determination result by the usage time determination unit.
An optical disc device characterized by the above. The optical disc apparatus according to any one of claims 1 to 6,
The circuit system includes a usage history determination unit that determines which of the plurality of laser elements was used last time,
The switching unit sets the laser element to be driven based on a determination result by the use history determination unit.
An optical disc device characterized by the above.

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