Abstract:
A light emitting unit is caused to emit a laser beam having a pulse width T 1  broader than a pulse width T 2  used at a time of recording, and a light receiving unit is caused to receive the laser beam and to output a first detection signal. A first control signal V 1  is generated by comparing a value held at a peak level of the first detection signal with a target value of a quantity of the laser beam, and a second control signal V 2  is generated by comparing the first control detection signal with the target value of a quantity of the laser beam.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-400906, filed Nov. 28, 2003, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to an automatic power control circuit for a laser beam of an optical disk apparatus, and in particular, to an optical disk apparatus having an automatic power control circuit for a laser beam in accordance with ringing or waveform rounding, and a method of controlling the optical disk apparatus.  
         [0004]     2. Description of the Related Art  
         [0005]     In an optical disk apparatus, a method of controlling the intensity of a laser outgoing beam involves the detection of an outgoing laser beam, and control thereof by an APC circuit in which a front monitor signal proportional to a quantity of the detected laser beam is made to be an input. Because the outgoing beam varies at a high speed during the time of recording data, the outgoing beam is sampled-and-held by sampling pulses in the APC circuit, and the APC circuit is made to actuate at respective levels of the recording level/erasing level/reproducing (bottom) level. Further, in the case of rewritable type media such as CD-RWs, DVD-RWs, and the like, because a laser outgoing beam varies between multi-pulses at a high speed when multi-pulses are used, samplings are not sufficient for the situation. Therefore, control of an outgoing beam is stably carried out by using a bottom hold circuit.  
         [0006]     However, the signal quality of a front monitor signal inputted to the APC circuit is easily affected in the above-described control method. In particular, there arises an error between a desired outgoing laser beam and a controlled outgoing laser beam due to a factor such as ringing, waveform rounding, or the like. In contrast thereto, a related technique corresponding to waveform rounding in a monitor signal has been known.  
         [0007]     In the Patent Document (Jpn. Pat. Appln. KOKAI Publication No. 2002-109733) which is a prior art, there is disclosed a recording/reproducing apparatus for an optical disk apparatus which controls a read level at the time of a light mode. Here, a quantity of shift of a monitor signal is detected while carrying out recording, and a read level at the time of a light mode is optimized.  
         [0008]     However, in the prior art of Patent Document 1, because detection of a quantity of shift of a monitor signal is carried out simultaneously with usual processing being carried out, processing in which a pulse width of a laser beam is adjusted in order to detect the quantity of shift, or the like is not carried out. Accordingly, there is the problem that detection of a quantity of shift of a monitor signal cannot be carried out in the optimum state. Further, in the prior art of Patent Document 1, detection of a quantity of shift of a monitor signal for optimizing a light level of a laser beam at the time of a light mode is not carried out, but detection of a quantity of shift for optimizing a read level is carried out. Accordingly, there is the problem that harmful effect of ringing or waveform rounding for a writing level at the time of light mode cannot be solved.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     An embodiment of the present invention is a method of controlling an optical disk apparatus, comprising: causing a light emitting unit to emit a laser beam having a pulse width broader than a pulse width used at the time of recording; causing a light receiving unit to receive the laser beam and to output a first detection signal; generating a first control signal by comparing a value held at a peak level of the first detection signal with a target value of a quantity of a laser beam; generating a second control signal by comparing the first detection signal with the target value of a quantity of the laser beam; determining a correction amount for equalizing the first control signal and the second control signal when the first control signal and the second control signal are not equal to each other, and storing the correction amount; and when information is recorded on an optical disk, controlling a quantity of light of the laser beam by correcting a control signal generated in accordance with the detection signal from the light receiving unit by means of the correction amount, and supplying the corrected control signal to a driving unit of the light emitting unit. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0010]      FIG. 1  is a block diagram showing one example of a configuration of an optical disk apparatus according to the present invention.  
         [0011]      FIG. 2  is a block diagram showing a configuration of one example of a pick-up of the optical disk apparatus according to the invention.  
         [0012]      FIG. 3  is a block diagram showing one example of a configuration of a light APC circuit of the optical disk apparatus according to the invention.  
         [0013]      FIG. 4  is a graph showing one example of an ideal front monitor signal in the APC circuit of the optical disk apparatus according to the invention.  
         [0014]      FIG. 5  is a graph showing one example of a front monitor signal in which ringing has arisen in the APC circuit of the optical disk apparatus according to the invention.  
         [0015]      FIG. 6  is a graph showing one example of a front monitor signal in which signal rounding has arisen in the APC circuit of the optical disk apparatus according to the invention.  
         [0016]      FIG. 7  is a graph showing one example of a case where ringing has been solved by a pulse having a long pulse width in the optical disk apparatus according to the invention.  
         [0017]      FIG. 8  is a graph showing one example of a case where signal rounding has been solved by a pulse having a long pulse width in the optical disk apparatus according to the invention.  
         [0018]      FIG. 9  is a flowchart showing one example of processing of generating a correction amount with respect to ringing, in the APC circuit of the optical disk apparatus according to the invention.  
         [0019]      FIG. 10  is a flowchart showing one example of processing of generating a correction amount with respect to signal rounding, in the APC circuit of the optical disk apparatus according to the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]     Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.  
         [0000]     Optical Disk Apparatus According to the Present Invention  
         [0000]     (Configuration)  
         [0021]     In  FIG. 1 , the optical disk apparatus according to the invention has an optical disk motor  12  which holds an optical disk D and rotates the optical disk D at a predetermined speed of rotation, an optical pick-up  14  which irradiates a light beam on the optical disk D and detects the reflected light, an RF amplifier  16  to which a detected signal is supplied and which generates an RF signal and a servo signal, and a signal processing circuit  18  and a laser output determining circuit  21  to which RF signals are supplied. Further, there are provided an interface  31  for transmitting and receiving data to and from the exterior, and a buffer memory  30  in which data provided by being connected to the interface  31  and regenerative data read by the optical pick-up  14 , or the like are temporarily stored.  
         [0022]     Further, there are provided an encoding processing circuit  28  which is connected to the buffer memory  30  and the interface  31 , and which encodes the provided data, and a laser light emitting driver  20  to which the output encoded by the encoding processing circuit  28  is supplied. The laser light emitting driver  20  is caused to control the output thereof by a control signal from the laser output determining circuit  21  connected to a system controller  10  for controlling the entire system operation, and causes the optical pick-up  14  to generate a laser beam based on an RF signal supplied from the RF amplifier  16 . Note that the system controller  10  is connected to the respective portions described above via data buses, and controls the operations thereof. Further, the system controller  10  includes a correction amount determining unit for carrying out processing of detecting an error amount corresponding to ringing and waveform rounding and processing of determining a correction signal corresponding to the error amount which are for corrective processing by a light APC circuit  11  which will be described later and the feature of the present invention.  
         [0023]     Furthermore, there are respectively provided a focus servo amplifier driver  23  which receives a focus error signal serving as a servo signal generated at the RF amplifier  16 , and carries out focus control of the optical pick-up  14 , and further, a tracking servo amplifier driver  25  which receives a tracking error signal serving as a servo signal generated at the RF amplifier  16 , and carries out tracking control of the optical pick-up  14 .  
         [0024]     Moreover, as shown in  FIG. 2 , the optical pick-up  14  of the optical disk apparatus according to the invention has an actuator  39  for holding an objective lens  39 - 2 , and driving coils  40  in a tracking direction of the actuator and driving coils  41  in a focusing direction of the actuator are provided at the actuator  39 . Here, servo control is made possible by supplying a tracking control signal CT and a focus control signal CF respectively from the tracking driver  25  and the focus driver  23  described above.  
         [0025]     The optical pick-up  14  carries out both of irradiation and light-receiving due to actuation of a beam splitter  37  or the like. Irradiation of a laser beam from a photo diode  35  corresponding to a laser light emitting drive signal d of the laser light emitting driver  20  passes through the beam splitter  37  via a lens  36 , and is condensed and irradiated on a predetermined region of the optical disk D via a ¼ wavelength plate  38  or the like by the objective lens  39 - 2 . Moreover, the reflected light from the optical disk D is enlarged by the objective lens  39 - 2 , is split toward a condensing lens  34  side by the beam splitter  37 , and is further supplied to a photo detector  32 . The photo detector  32  supplies a detection signal S, and a tracking error signal and a focus error signal are supplied to the tracking servo amplifier  25  and the focus servo amplifier  23  via the RF amplifier  16 . Further, a detection signal S for generating a regenerative signal is supplied to the signal processing circuit  18 .  
         [0026]     In addition, the optical disk apparatus according to the present invention has the light APC (Automatic power controller) circuit  11  which carries out control of the laser light emitting driver  20  by receiving a front monitor signal M from a front monitor  33  of the optical pick-up  14 , and by supplying a control signal C which appropriately corresponds to the signal to the laser light emitting driver  20 . The light APC circuit  11  particularly carries out power control of a laser beam at the time of writing on the optical disk D.  
         [0027]     Here, as shown in  FIG. 3 , the light APC circuit  11  has a peak hold circuit  49  for receiving a front monitor signal M from the front monitor  33  of the optical pick-up  14 , a switch part  48  which can arbitrarily select one of an input terminal  46  receiving a front monitor signal M and an input terminal  47  from the peak hold circuit  49 , a gain amplifier  42  to which an output of the switch part  48  and a reference electric potential are inputted, a sampling hold circuit  43  to which the gain amplifier  42  is supplied, and a gain amplifier  44  to which an output of the sampling hold circuit  43  and a register  45  in which a correction amount is stored are supplied.  
         [0000]     (Basic Operation)  
         [0028]     In the optical disk apparatus having such a configuration, processing of regenerating an optical disk is carried out as follows. Namely, under the control of the system controller  10 , the optical disk D rotated at a predetermined speed by the optical disk motor  12  emits a laser beam in accordance with the laser light emitting driver  20  set at the laser output setting circuit  21 , the reflected light thereof is detected by the optical pick-up  14 , and a detection signal based on the detection is output. The detection signal is supplied to the RF amplifier  16 , an RF signal output therefrom is supplied to the signal processing circuit  18  and the laser output setting circuit  21 , and a focus error signal and a tracking error signal serving as servo signals generated at the RF amplifier  16  are respectively supplied to the focus servo amplifier  23  and the tracking servo amplifier  25 . At the signal processing circuit  18 , the RF signal is decoded, and the decoded signal is temporarily stored in the buffer memory  30 , or is directly output to the exterior via the interface  31 . Further, the system controller  10  controls rotation of the optical disk motor  12  by generating a control signal for controlling the rotation of the optical disk motor  12 .  
         [0029]     Moreover, in the optical disk apparatus having such a configuration, processing of recording onto an optical disk is carried out as follows. Namely, under the control of the system controller  10 , for example, the data supplied via the interface  31  is supplied to the encoding processing circuit  28  after being temporarily stored in the buffer memory  30 , and is encoded and output. In accordance with the encoded output and an output from the laser output setting circuit  21 , a driver output of the laser light emitting driver  20  is supplied to the optical pick-up  14 . In the optical pick-up  14 , recording processing is carried out by emitting a laser beam corresponding to the driver output from the mounted photo diode  35 , and by irradiating the laser beam on the storage region of the optical disk D which has been being rotated at a predetermined speed of rotation by the optical disk motor  12 .  
         [0000]     Light APC Circuit According to the Present Invention  
         [0030]     Hereinafter, operations of the light APC circuit according to the invention will be described in detail with reference to the drawings.  FIG. 4  is a graph showing one example of an ideal front monitor signal in the APC circuit of the optical disk apparatus according to the invention.  FIG. 5  is a graph showing one example of a front monitor signal in which ringing has arisen in the APC circuit of the optical disk apparatus according to the invention.  FIG. 6  is a graph showing one example of a front monitor signal in which signal rounding has arisen in the APC circuit of the optical disk apparatus according to the invention.  FIG. 7  is a graph showing one example of a case where ringing has been solved by a pulse having a long pulse width in the optical disk apparatus according to the invention.  FIG. 8  is a graph showing one example of a case where signal rounding has been solved by a pulse having a long pulse width in the optical disk apparatus according to the invention.  FIG. 9  is a flowchart showing one example of processings of determining/storing a correction amount, in the APC circuit of the optical disk apparatus according to the invention.  
         [0000]     (Basis Operation)  
         [0031]     In the optical disk apparatus described above, basic operation of the light APC (Automatic power control) circuit  11  according to the invention will be described. In FIGS.  1  to  3 , control of a light power serving as a laser beam at the time of recording processing is carried out, the detection signal M from the front monitor  33  is supplied to the peak hold circuit  49  and the input terminal  46 , and the output of the peak hold circuit  49  is supplied to the input terminal  47 . However, at the time of usual data recording, the detection signal M from the front monitor  33  is supplied from the input terminal  46  to the input terminal of the gain amplifier  42 , and a control signal which is appropriate as compared with a reference electric potential VR shown in  FIG. 4  is output from the gain amplifier  42 . The control signal is further supplied to the input terminal of the gain amplifier  44  via the sampling hold circuit  43 , and when a correction value is not supplied from the register  45 , the control signal is directly supplied to the laser light emitting driver  20  as a laser control current C. The laser light emitting driver  20  controls a quantity of light of the laser beam from the photo diode  35  serving as a light emitting unit by supplying a laser light emitting drive signal d to the photo diode  35  in order to appropriately control a quantity of light of the laser beam in accordance with the laser control current C.  
         [0000]     (Malfunction due to Ringing and Waveform Rounding)  
         [0032]     However, in the detection signal from the front monitor  33  of the optical pick-up  14 , there are cases in which ringing R shown in  FIG. 5  or waveform rounding H shown in  FIG. 6  arises, and an error component caused therefrom deteriorates the signal quality of the detection signal.  
         [0033]     Namely, in  FIG. 5 , the front monitor signal M shows a level L 1  including an error amount a due to ringing R, in place of showing an original level L 0 . Here, the ringing is a noise generated in a short time, and in accordance therewith, not the original level L 0 , but the larger level L 1  to which the error amount a is added is shown, which affects controlling a quantity of laser beam.  
         [0034]     Further, in  FIG. 6 , the front monitor signal M shows a level L 2  including an error amount b due to waveform rounding H, in place of showing an original level L 0 . The waveform rounding H shows an error value due to a pulse period being completed before the signal sufficiently reaches an original value because of an insufficient pulse width, and the original level L 0  of the front monitor signal M is not shown, but the insufficient level L 2  to which an error amount b is added is shown, which affects controlling a quantity of laser beam in the same way.  
         [0035]     It is said that such ringing R and waveform rounding H are caused by dispersion in each of a quantity of incident light to a pin photo diode converting a laser beam into electric information, a gain of an I/V converting circuit, a capacity of an external capacitor, and such ringing R and waveform rounding H deteriorate the signal quality of a detection signal. Therefore, for example, because a detection signal M shows a value lower than an original value when ringing R arises, it is misunderstood that the quantity of laser beam is higher than an actual value. Accordingly, the laser beam is made too dark by controlling the quantity of laser beam to be lower than a target value by the control function of the light APC circuit  11 .  
         [0036]     In the same way, because the detection signal M shows a value higher than an original value when waveform rounding H arises, it is misunderstood that a quantity of laser beam is lower than an actual value. Accordingly, the laser beam is made too bright by controlling a quantity of laser beam to be higher than a target value by the control function of the light APC circuit  11 . An optimum recording power cannot be obtained as a driving apparatus in both of the cases, which brings about a deterioration in the reliability of recording processing.  
         [0000]     (Processing of Correction with Respect to Ringing and Waveform Rounding)  
         [0037]     Next, processing of generation a correction amount with respect to such ringing and waveform rounding H will be described in detail hereinafter by using the timing charts of  FIGS. 7 and 8  and the flowcharts of  FIGS. 9 and 10 . It is preferable that the generating of a correction amount with respect to ringing and waveform rounding H according to the invention be carried out by an engineer, for example, by using a tool, at the time of factory shipment with respect to a single optical pick-up unit, and be carried out so as to store the correction amount in the register  45  of the light APC circuit  11 . Further, it is preferable that the generating of a correction amount with respect to ringing and waveform rounding H is carried out due to a test mode being set in an operating program of the system controller  10  of the optical disk apparatus, and a user or an engineer accessing the test mode. Furthermore, such an operation may be carried out at the time of starting of the optical disk apparatus without being noticed by a user by being set as one part of the operating program of the system controller  10 , and is preferably automatically carried out periodically, such as, once a year.  
         [0038]     The generating of a correction amount for eliminating the effect of ringing is carried out such that a laser beam having a pulse width which is about the laser beam used at the time of light is generated, and a control signal V 1  at the time of preparing a detection signal which is not affected by ringing is determined. Next, a control signal V 2  including the effect of ringing is determined by turning the peak hold circuit on, and a control amount for equalizing the both signals is determined.  
         [0039]     In processing of determining a correction amount corresponding to ringing, in the test mode described above, and by an operation of an engineer or under the control of the system controller  10 , as shown in the timing chart of  FIG. 7 , and in the flowchart of  FIG. 9 , a recording power Pw is set to the register A (S 11 ), and respective parameters are recorded and set in the RF amplifier  16  (S 12 ). Further, a test strategy is set to a pulse width T 1  (for example, provided that a pulse width T 2  usually used for recording and playback is 20 nsec, it is 1 μsec, which is about 50 times 20 nsec (S 13 ). Then, the peak hold circuit  49  is made to be in an OFF-state (S 14 ), the light mode is turned on (S 15 ), and a laser beam is emitted having a pulse width T 1  (s), which is long enough to make the effect of ringing negligible. At this time, the outgoing beam is Pw 1  (mW), the control voltage is V 1  (V), and the register value to which the outgoing beam is set is A.  
         [0040]     By setting such a laser beam having a sufficiently long pulse width T 1 , it is possible to ignore a settling time until the time when ringing is settled down, and a real control voltage V 1  without the effect of ringing is obtained by sampling-and-holding the portions in which ringing has not arisen (S 16 ). Namely, the control voltage V 1  corresponds to the laser control current C serving as an output of the gain amplifier  44  of  FIG. 3  at the time of irradiating a laser beam having the pulse width T 1 . The control voltage V 1  is stored in, for example, the storage region of the laser light emitting driver  20 , a storage region provided by an engineer (S 17 ).  
         [0041]     Next, in order to determine the control voltage V 2  which is affected by ringing, the peak hold circuit is turned on (S 18 ). At this time, as shown in  FIG. 7 , because the monitor signal M shows E 1  (V) in place of showing E 2  (V) due to the effect of ringing, a control voltage (corresponding to the control current C) is varied to show the control voltage V 2  (V) due to the actuation of the light APC circuit  11  (S 19 ). As a result, the laser beam is made to be Pw 2  (mW), and the laser beam is made unreasonably dark due to the effect of ringing (Pw 1 &gt;Pw 2 ).  
         [0042]     Originally, in a state in which there is no ringing, by using the fact that E 1 =E 2  and V 1 =V 2 , it is determined whether or not it is V 1 =V 2  (S 20 ). When the control voltage V 1 =V 2 , it is determined that ringing has not arisen, and the routine proceeds to processing of generating a correction amount corresponding to waveform rounding in  FIG. 10 . When it is not V 1 =V 2 , it is questioned whether or not it is V 1 &gt;V 2  (S 21 ), and when it is V 1 &gt;V 2 , the value of the register A which is a correction value is increased by one unit (S 22 ), and when it is V 1 &lt;V 2 , the value of the register A which is a correction value is decreased by one unit (S 23 ), and a variation in the control signal V 2  is investigated again (S 24 ). This adjustment of the value of the register A is repeated until the time when it is made to be V 1 =V 2  (S 25 ), and the value of the register A when it is made to be finally V 1 =V 2  is determined to be the correction amount for solving the effect of ringing (S 26 ).  
         [0043]     Next, processing of generating of a correction amount corresponding to waveform rounding will be described by using the flowchart of  FIG. 10 . In step S 20 , when it is V 1 =V 2 , it is determined that there is no ringing, and next, the effect of waveform rounding is investigated, and a correction amount corresponding thereto is generated.  
         [0044]     With respect to waveform rounding, as shown in  FIG. 8 , the effect thereof is detected as a form of a control voltage V 3  by using a pulse T 2  (s) having the same length as that of the pulse used at the time of writing. Namely, in the flowchart of  FIG. 10 , the light mode is tuned off (S 31 ), and a test strategy is set as a pulse width T 2  (S 32 ). Then, due to the light mode being turned on (S 33 ), and due to the peak hold circuit  49  being turned on (S 34 ), as shown in  FIG. 8 , when there is waveform rounding, an effect appears as a value of the control voltage V 3 . Here, the control voltage V 3  is read (S 35 ), and is compared with the control voltage V 1  in the case where there is no effect of ringing or waveform rounding. When it is V 1 =V 3  (S 36 ), it is determined that there is neither ringing nor waveform rounding, and the correction amount is zero or the correction amount is not generated (S 37 ).  
         [0045]     When it is not V 1 =V 3 , it is questioned whether or not it is V 1 &gt;V 3  (S 38 ), and when it is V 1 &gt;V 3 , the value of the register A which is a correction value is increased by one unit (S 39 ), and when it is V 1 &lt;V 3 , the value of the register A which is a correction value is decreased by one unit (S 40 ), and a variation in the control signal V 3  is investigated again (S 41 ). This adjustment of the value of the register A is repeated until the time when it is made to be V 1 =V 3  (S 42 ), and the value of the register A when it is made to be finally V 1 =V 3  is determined to be the correction amount for solving the effect of waveform rounding (S 43 ).  
         [0046]     The correction amount is stored in the register  45  of the light APC circuit  11  in  FIG. 3  in order to reduce/eliminate the effect of ringing or waveform rounding. This operation may be automatically carried out by the system controller  10 , or may be carried out by an engineer at the time of factory shipment. Then, at the time of the operation of usual recording of the optical disk apparatus, the control signal generated in order for the front monitor signal M to be close to the reference voltage VR is further corrected by the operation of the gain amplifier  44  based on the correction amount provided from the register  45 , and for example, the effect of ringing or the effect of waveform rounding is reduced or eliminated. In accordance therewith, it is possible to avoid that a quantity of light of the laser beam is made inappropriate due to the effect of ringing or waveform rounding, and to provide an optical disk apparatus which carries out highly reliable recording processing.  
         [0047]     As described above, in the method of controlling the optical disk apparatus according to the invention, in order to solve an error which included in a detection signal of a front monitor detecting a quantity of light of a laser beam, and which is generated due to ringing and waveform rounding, a laser beam having a pulse width sufficiently long which is not used in the usual operation is used with being away from a usual operation. One example of this pulse width is a laser beam having a sufficiently long pulse width in which, provided that the pulse width usually used for recording or playback is 20 nsec, a pulse width is 1 μsec which is about 50 times 20 nsec.  
         [0048]     Namely, a laser beam is emitted by two types of a recording pulse having a sufficiently long pulse width (for example, 1 μsec) with respect to a time width of ringing and waveform rounding and a recording pulse having a short pulse width (for example, 20 nsec) with respect to the above-described time width. The peak hold circuit is turned on and off at that time, and an error amount generated due to ringing and waveform rounding is determined on the basis of a difference of the voltages controlling the outgoing laser beam.  
         [0049]     Due to a control signal being corrected at the time of recording in accordance with the error amount determined in this way, even in a front monitor in which ringing or waveform rounding is great, due to a laser beam having an appropriate quantity of light being supplied without including these error amounts, an optical disk apparatus which can carry out stable recording processing can be provided.  
         [0050]     Note that, in the prior art in the Patent Document 1, only a laser beam having a normal pulse width can be used because of the detection of a quantity of shift carried out at the time of usual writing operation, and therefore, errors of ringing and waveform rounding cannot be sufficiently detected.  
         [0051]     In accordance with the various embodiments described above, those skilled in the art can realize the present invention. However, it is easy for those skilled in the art to further conceive of various modifications of these embodiments, and the present invention can be realized using various embodiments without inventive ability. Accordingly, the present invention extends over a broad range which does not contradict the disclosed principles and the novel features, and is not limited to the embodiments described above.