Abstract:
In optical disc drive, laser diode is used, and also HFM (High Frequency Module) oscillator is used to reduce laser mode hopping noise. Big EMI noise is radiated by the HFM current for optical noise reduction, or by the switching current for write-strategy of recording. Then conventionally, shield was required in order to reduce EMI noise radiated by the current driving a laser diode. By giving a jitter to the HFM signal superimposed to the current of laser diode or switching signal by write-strategy for recording, a spectrum is diffused and the peak value of an EMI noise is reduced.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention is applicable both for laser drive unit, optical head, and optical disk drive equipment, to irradiating laser light when playing back or recording data on optical discs, such as a compact disk and DVD.  
         [0003]     2. Description of the Related Art  
         [0004]     Recently laser diode is used for the laser light emitting element of optical disk drive equipment because of small size and low power consumption, but when a laser diode is used as a light source of optical disk drive equipment, the reflected light from an optical disc interferes in the laser oscillation mode of a laser diode, and an optical noise arises. The high-frequency-current superposition method that superimposes AC current of the high frequency from a high-frequency-current drive circuit on DC current to a laser diode which is known as the optical noise reduction method. However, when high frequency current was superimposed, which came with problem of big EMI (Electro Magnetic Interference) noise occurred.  
         [0005]     The LD Drive output the Write power as Write-Strategy waveform to switch the current flow through the laser diode when recording data on optical disc, the period even it is not so damage but the problem which is a laser diode that the fundamental wave and harmonics of the switching still became a big EMI noise also had a laser light emitting element.  
         [0006]     there are some method to reduce EMI noise which is show up at referenced patent document 1 and a referenced patent document 2.  
         [0007]     According to a referenced patent document 1, an optical head is comprising a laser diode and some of electronic parts mounted on circuit board, these parts is connected to laser diode in between.  
         [0008]     a case of a conductive material surrounding the electronic circuit part mounted in the circuit board, a object lens drive unit which condenses the optical beam from  
         [0009]     a laser diode to a optical spot on a disk.  
         [0010]     a pedestal in which the semiconductor laser, the circuit board, the case, and the object lens drive were hold.  
         [0011]     a shaft which can be slide for the pedestal and fixed to the traverse base.  
         [0012]     Also the box is equipped with the spring part by which a force is made to act the shaft with a shield function.  
         [0013]     According to this, the case is characterized by having the spring part on which force is made to act to a shaft with a shield function, and the EMI noise is reduced by the shield function of a case.  
         [0014]     According to a referenced patent document 2, the board unit for an optical head is comprising a flexible printed wiring board, an optical element by which optical surface were attached in the surface side of the flexible printed wiring board by the terminal part toward the back side of the flexible printed wiring board, besides a high frequency superposition circuit also mounted on the flexible printed wiring board, and a shielding case.  
         [0015]     the shielding case is attached to cover on the opposite side of optical surface of the optical element and terminal to the surface side of the flexible printed wiring board of the optical element block. It is bent so that the surface sides of the flexible printed wiring board of the optical element block and the high frequency superposition circuit part may face each other. The flexible printed wiring board is next to the high frequency superposition circuit and both is located inside the shielding case. The flexible printed wiring board between the above-mentioned optical element and a high frequency superposition circuit is the flexible printed wiring board unit characterized by being located in a shielding case among the above-mentioned flexible printed wiring boards.  
         [0016]     According to this, EMI is reduced by attaching optical element towards the back side of the flexible printed wiring board, fixing by the surface side, making a flexible printed wiring board further crooked, so that the surface side may become inside, and making it arrange in a shielding case.  
         [0017]     However, since an EMI noise is made not to be emitted outside by shielding in any case, there was a fault that mechanism is restrictions to occur and cost is needed for shield.  
         [0000]     Reference Document:  
         [0018]     1. Japan Patent Publication Number H11-154334  
         [0019]     2. Japan Patent Publication Number 2000-322754  
       SUMMARY OF THE INVENTION  
       [0020]     The problem we want to solve is that, a shield required in order to reduce an EMI noise, then mechanism restrictions and cost of a shield required.  
         [0021]     By giving a jitter to the high frequency superposition signal which is superimposed by the current to a laser diode and becomes the origin of an EMI noise, and the switching signal by write-strategy at the time of record, this invention diffuses a spectrum and reduce the peak value of an EMI noise.  
         [0022]     In order that the spectrum of an EMI noise may diffuse, a laser drive, an optical head, and an optical disk drive equipment of this invention in order to give a jitter to a high frequency superposition signal and the switching signal by write-strategy at the time of record, and the peak level of radiation may reduce them, a shield becomes unnecessary, therefore the mechanism restrictions of them are lost, and the advantage that the cost for shielding also becomes unnecessary and the cost reduction of it can be carried out is.  
         [0023]     In order to reduce the peak level of an EMI noise, reduction of an EMI noise was realized by adding a jitter to the output waveform of a high frequency superposition circuit at the time of record mark un-forming at the time of reproduction and record without the shield by adding a jitter to the output waveform of a write-strategy generating circuit, and diffusing the spectrum of an EMI noise at the time of record. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     This invention is described with particularity in the appended claims. The above and further advantages of this invention may be better understood by referring to the following description taken in conjunction with the accompanying drawings, in which:  
         [0025]      FIG. 1  is a block diagram of an example 1 of the optical disk drive equipment of this invention.  
         [0026]      FIG. 2  is an example 1 of jitter addition method to the high frequency signal used for the equipment of this invention.  
         [0027]      FIG. 3  is an example 2 of jitter addition method to the high frequency signal used for the equipment of this invention.  
         [0028]      FIG. 4  is an example 3 of jitter addition method to the high frequency signal used for the equipment of this invention.  
         [0029]      FIG. 5  is an explanation figure of the effect of this invention.  
         [0030]      FIG. 6  is a block diagram of an example 2 of the optical disk drive equipment of this invention.  
         [0031]      FIG. 7  is an explanation figure of write-strategy.  
         [0032]      FIG. 8  is a block diagram of example 1 of a jitter addition method to the write-strategy output used for the equipment of this invention.  
         [0033]      FIG. 9  is a block diagram of example 2 of a jitter addition method to the write-strategy output used for the equipment of this invention.  
         [0034]      FIG. 10  is an explanation figure of an example 2 of the jitter addition method to the write-strategy output used for the equipment of this invention.  
         [0035]      FIG. 11  is a block diagram of an example 3 of the optical disk drive equipment of this invention.  
         [0036]      FIG. 12  is a block diagram of example 3 of a jitter addition method to the write-strategy output used for the equipment of this invention.  
         [0037]      FIG. 13  is a block diagram of example 1 of a jitter signal generator used for the equipment of this invention.  
         [0038]      FIG. 14  is an explanation figure of example 1 of a jitter signal generator used for the equipment of this invention.  
         [0039]      FIG. 15  is a block diagram of example 2 of a jitter signal generator used for the equipment of this invention.  
         [0040]      FIG. 16  is an explanation figure of example 2 of a jitter signal generator used for the equipment of this invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0041]      FIG. 1  is a block diagram of an example 1 of the optical disk drive equipment of this invention.  
         [0042]     Number  1  is an optical disc,  2  is an optical head,  3  is a laser drive unit,  4  is an optical system,  5  is a laser diode,  6  is an optical detector,  7  is a high frequency superposition circuit,  8  is laser driver,  9  is a high frequency oscillator,  10  is jitter addition circuit,  11  is a jitter signal generator,  12  is a control circuit.  
         [0043]     Thus, in the constituted optical disk drive equipment, it is condensed by an optical system  4  and the light emitted from the laser diode  5  is irradiated by the optical disc  1 . The part of the light which emitted light from the laser diode  5  is changed into an electric signal with an optical detector  6  as a monitor signal for control of luminescence power, is controlled by a control circuit  12  to become the value as which the monitor signal for control was determined, and drives a laser diode  5  through the laser drive unit  3 . It consists of the laser driver  8 , the high frequency superposition circuit  7 , a high frequency oscillator  9 , a jitter addition circuit  10 , and a jitter signal generator, the jitter generated in the jitter signal generator  11  of the after-mentioned ( FIG. 13-16 ) carries out the frequency modulation of the high frequency signal generated by the jitter addition circuit  10  in the high frequency oscillator  9 , a jitter is given to the laser drive unit  3 .  
         [0044]      FIG. 2  is an example 1 of the jitter addition method to the high frequency signal used for the equipment of this invention.  
         [0045]     Number  9  is a high frequency oscillator,  10  is a jitter addition circuit,  11  is a jitter signal generator, Q 1  is a transistor, R 1 - 4  are resistances, C 1 - 4  are capacitors, L 1  is a coil, and D 1  is a variable capacitance diode,  
         [0046]     A collector is connected to a power supply as a collector grounding type amplifier Q 1 . Load resistance R 1  is connected to emitter, and bias voltage is given to a base by resistance division of R 2  and R 3 . A resonant circuit consists of series circuits of C 1  and C 2  via the capacitor C 3  for a direct-current cut L 1 . The Colpitz oscillator circuit which returns from emitter of Q 1  between C 1  and C 2  is constituted, and the electric capacity of the amount diode D 1  of good changes is further added to the resonant circuit in parallel with the in-series capacity of C 1  and C 2  via the capacitor C 4  for a direct-current cut L 1 . The output of the jitter signal generator  11  is applied via R 4 , since the capacity value of D 1  changes according to a jitter signal, resonance frequency changes and, as for D 1 , the frequency modulation of the high frequency signal is carried out by a jitter signal.  
         [0047]     Moreover, although the Hartley type may be used although the Colpitz type explained the oscillating circuit here, a emitter grounding type or a common base type may be used although the collector grounding type explained the grounded type, and the bipolar transistor explained the transistor, it is the same also with FET or other amplification elements.  
         [0048]      FIG. 3  is an example 2 of jitter addition method to the high frequency signal used for the equipment of this invention.  
         [0049]     Number  9  is a high frequency oscillator,  10  is a jitter addition circuit,  11  is a jitter signal generators,  13 ,  14 , and  15  is inverters,  16  is a inverter drive circuit, and C 5 , C 6  and C 7  are capacitor.  
         [0050]     The oscillating circuit which each output is connected to the input of the following stage in the shape of a ring, and C 1 , C 2 , and C 3  for delay are connected to each output, and will oscillate an inverter  13 , an inverter  14 , and an inverter  15  on the frequency from which total of delay of each inverter becomes 180 phase delay if the power supply is connected to the inverter drive circuit  16  and odd inverters are connected in the shape of a ring in this way is constituted. It was equivalent to the jitter addition circuit  10 , and has given variable power supply current or power supply voltage to the inverter  13 , the inverter  14 , and the inverter  15 , and its delay is large, when the power supply current is large, the current and delay by C 5 , C 6 , and C 7  of the inverter drive circuit  16  are small and its power supply current is small. When ON resistance of an inverter  14  and an inverter  15  changes with power supply voltage, when power supply voltage is low, since ON resistance is high, delay is large [since ON resistance is small when power supply voltage is high, the ON resistance and delay by C 5 , C 6 , and C 7  are small, and], when power supply voltage is given. Although C 5 , C 6 , and C 7  for delay are written here, if the input gate capacity of parasitism of an inverter  13 , an inverter  14 , and an inverter  15  is used, there will be no necessity specially. If the power supply current or power supply voltage supplied to the inverter drive circuit  16  with the output of a jitter signal generator is changed, since the frequency from which phase delay becomes  180  degrees will change, the frequency modulation of the high frequency signal is carried out by a jitter signal.  
         [0051]      FIG. 4  is an example 3 of jitter addition method to the high frequency signal used for the equipment of this invention.  
         [0052]     Number  9  is a high frequency oscillator,  10  is a jitter addition circuit,  11  is a jitter signal generator, Q 2 , Q 3 , Q 4 , Q 5 , and Q 6  are N channel MOS types FETs, R 5 , R 6 , R 7  and R 8  are resistances, and C 8  is a capacitor.  
         [0053]     The high frequency oscillator  9  which is called sauce knot-pattern multi-vibrator by Q 2 , Q 3 , R 5 , R 6 , and C 8  is constituted. The current supplied to Q 2  and Q 3  is supplied in the source of current of Q 4  and Q 5 , the mirror of the current which flows through the current value into R 7  and Q 6  is carried out in the mirror circuit of Q 4  and Q 5 , and oscillation frequency is decided by the mirror current and the capacity value of C 8 . In order that the output of the jitter signal generator  11  may pour in current between R 7  and Q 6  through R 8 , R 8  becomes the jitter addition circuit  10 , and since oscillation frequency is decided by the mirror current which changes with jitter signals, the frequency modulation of the high frequency signal is carried out by a jitter signal.  
         [0054]     Here, although MOS type FET of N channels explained, even if a case of the operation is MOS type FET of P channels, it is junction type FET, and it is a bipolar transistor, it can be constituted similarly.  
         [0055]      FIG. 5  is an explanation figure of the effect of this invention.  
         [0056]     A horizontal axis is frequency and a vertical axis is radiation field intensity.  17  is a radiation level when not giving a jitter to the conventional high frequency which carries out high frequency superposition, and generates a big peak in superposition frequency.  18  is a radiation level at the time of giving a jitter to the superposition frequency of this invention and applying frequency modulation, since a spectrum distributes, a peak level falls, the disturbance to other apparatus is reduced remarkably, and needlessness or simplification can do a shield.  
         [0057]      FIG. 6  is a block diagram of an example 2 of the optical disk drive equipment of this invention.  
         [0058]     Number  1  is an optical disc,  2  is an optical head,  3  is a laser drive unit,  4  is an optical system,  5  is a laser diode,  6  is an optical detector,  8  is a laser driver,  10  is a jitter addition circuit,  11  is a jitter signal generator,  12  is a control circuit,  21  is a write-strategy generating circuit, and  22  is recording signal generator.  
         [0059]      FIG. 7  is an explanation figure of write-strategy.  
         [0060]     (a) is a recording signal, (b) is a record clock, (c) is a write-strategy output.  
         [0061]     Write-strategy indicated here is an over-write type waveform, and in the portion which forms a mark, a multi-pulse has occurred, in the space part which does not form a mark, the signal of elimination power has occurred.  
         [0062]     Operation at the time of recording on an optical disc  1  is explained using  FIG. 6  and  FIG. 7 . First, if a recording signal (a) and a record clock (b) are outputted from the recording signal generating circuit  22  and it is inputted into the write-strategy generating circuit  21 , the write-strategy output (c) which becomes the origin of the optical power waveform of the laser diode  5  when recording on an optical disc  1  will be outputted from the write-strategy generating circuit  21 . A write-strategy output (c) is inputted into the laser driver  5 , drives a laser diode  5 , and is irradiated by the disk  1  through an optical system  4 , and a recording signal is recorded. A part of light outputted from a laser diode  5  is changed into an electric signal with an optical detector  6  as a monitor signal for control of luminescence power, and it is controlled by a control circuit  12  to become the value as which the monitor signal for control was determined. Furthermore, in order that switching of the laser drive current by a write-strategy output (c) may prevent a big EMI noise from occurring, a jitter signal occurs in the jitter signal generator  11 , a jitter is added to a write-strategy output (c) in the jitter addition circuit  10 , the spectrum of an EMI noise is spread, and a peak level falls.  
         [0063]      FIG. 8  is a block diagram of example 1 of a jitter addition method to the write-strategy output used for the equipment of this invention.  
         [0064]     Number  11  is a jitter signal generator,  23  is a phase comparator,  24  is a loop filter,  25  is an adding machine, and  26  is a voltage controlled oscillator.  
         [0065]     In  FIG. 8 , since the output of the record clock (b) from the recording signal generating circuit  22  and a voltage controlled oscillator  26  is inputted into the phase comparator  23 , phase comparison is carried out and the output is inputted into a voltage controlled oscillator  26  via a loop filter  24  and an adding machine  25 , the output of a voltage controlled oscillator  26  constitutes PLL used as the signal by which the phase lock was carried out on the record clock (b). Since the jitter signal from the jitter signal generator  11  is added to the output of a loop filter  24  with an adding machine  25  at this time, the output of a voltage controlled oscillator  26  serves as a signal with a jitter. If a write-strategy signal is generated based on this signal, a jitter will be added also to a write-strategy signal.  
         [0066]     Here, if the write-strategy generating circuit  21  needs the clock of the integral multiple of a record clock, and the output of a voltage controlled oscillator  26  is divided by divider and it inputs into the phase comparator  23 , the clock of divide ratio times of a record clock can be obtained.  
         [0067]      FIG. 9  is a block diagram of example 2 of a jitter addition method to the write-strategy output used for the equipment of this invention.  
         [0068]     Number  11  is a jitter signal generator,  31  is a delay line,  32  is a phase comparator,  33  is a loop filter,  34  is an adding machine,  35  is a delay line drive circuit,  36  is a write-strategy control circuit, and  37  is a selection gate circuit.  
         [0069]     A delay line  31  consists of buffers of number n for delay and it lets all the buffers for delay pass, only about 1 cycle of a record clock (b) will be delayed. For example, if delay time of one buffer for delay is set to 0.3 ns for the cycle of a record clock (b) for 30 ns, when it lets the buffer for delay of the number of n=100 pass, it will be behind by one cycle of a record clock (b) exactly.  
         [0070]      FIG. 10  is an explanation figure of the block diagram of  FIG. 9   
         [0071]     (0) is a input signal of the delay line  31  and the same as a record clock (b), (1), (2), . . . (n−1), and (n) are the output signals through the buffer for delay of the number of stages in a parenthesis, and (p) is a phase comparison output from the phase comparator  32 .  
         [0072]     When the delay time of n delay lines is late by one cycle of a record clock (b) exactly, a phase comparison output (p) is not outputted, but delay time is small, and it progresses like  41 , negative is outputted like  42 , and a phase comparison output (p) has large delay time, and it late like  43 , positive is outputted like  44 .  
         [0073]     Operation is explained using  FIG. 9  and  FIG. 10 .  
         [0074]     The phase comparison output (p) of the phase comparator  32  is smoothed, and will be carried out with a loop filter  32 , the delay line drive circuit  35  will be supplied through an adding machine  34 , and the power supply voltage of the buffer for delay of the delay line  31  will be controlled. Thus, if constituted, when the delay time of the buffer for delay is small, negative will be outputted to a phase comparison output (p). The voltage from the delay line drive circuit  35  falls, and the delay time of the buffer for delay becomes large. Moreover, when the delay time of the buffer for delay is large, positive is outputted to a phase comparison output (p). The voltage from the delay line drive circuit  35  goes up, and the feedback loop that the delay time of the buffer for delay becomes small is constituted, and it is controlled so that the output of the delay line  31  always becomes 1 cycle delay to a record clock (b). By doing in this way, the arbitrary delay waveforms for write-strategy can be obtained without using a high-speed clock, and a required write-strategy waveform is decided in the write-strategy control circuit  36  according to a recording signal (a), and the selection gate of the pulse from which delay from the delay line  31  to which delay is outputted as a write-strategy output (c) is carried out by the selection gate circuit  37 , and it is outputted. At this time, by adding the jitter output from the jitter signal generator  11  to the output of a loop filter  33  with an adding machine  34 , a jitter is added to the delay line  31  via a delay line drive circuit, and a jitter is added to a write-strategy output (c).  
         [0075]      FIG. 11  is a block diagram of an example 3 of the optical disk drive equipment of this invention.  
         [0076]     Number  1  is an optical disc,  2  is an optical head,  4  is an optical system,  5  is a laser diode,  6  is an optical detector,  8  is a laser driver,  10  is a jitter addition circuit,  11  is a jitter signal generator,  12  is a control circuit,  21  is a write-strategy generating circuit, and  22  is recording signal generator.  
         [0077]     This is an example that a write-strategy generating circuit  21  for record is put on the circuit block side of optical disk drive equipment instead of in the optical head  2 .  
         [0078]     Although the method of  FIG. 8  and the method of  FIG. 9  can also be used for the method of adding a jitter to a write-strategy output, the method of  FIG. 12  can be further used as method of example 3.  
         [0079]      FIG. 12  is a block diagram of example 3 of a jitter addition method to the write-strategy output used for the equipment of this invention.  
         [0080]     Number  11  is a jitter signal generator,  51  is a wobble signal detector circuit,  52  is a phase comparator,  53  is a loop filter,  54  is an adding machine,  55  is a voltage controlled oscillator, and  56  is a divider.  
         [0081]     In  FIG. 12 , the tracking error signal is inputted into the wobble signal detector circuit  51 .  
         [0082]     The track wobble signal included in a tracking error signal is formed into 2 values, and is inputted into the phase comparator  52 . Phase comparison is carried out with the output which divided the voltage controlled oscillator  55  by divider  56 , it is smoothed with a loop filter  53 , the PLL circuit inputted into a voltage controlled oscillator  55  through an adding machine  54  is constituted, and the record clock which synchronized with the track wobble is generated. For example, when generating  186  record clocks per track wobble, the divide ratio of divider  56  is set as 186. Thus, although the method of  FIG. 8  can be used for the generated record clock and a jitter can also be added, the record clock to which the direct jitter was added can be obtained by adding the jitter signal of the jitter signal generator  11  to the output of a loop filter  53  with an adding machine  54  like the case of the operation of  FIG. 12 .  
         [0083]      FIG. 13  is a block diagram of example 1 of a jitter signal generator used for the equipment of this invention.  
         [0084]     Number  61  is an up/down counter,  62  is a maximum detector circuit,  63  is a zero value detector,  64  is a flip-flop of a set and reset type, and  65  is a DAC (Digital to Analog Converter).  
         [0085]      FIG. 14  is an explanation figure of  FIG. 13  case of the jitter signal generator  11  ( FIG. 13 ) used for the equipment of this invention.  
         [0086]     This is the figure of the output of the up/down counter  61 , and  66  is the maximum value of the up/down counter  61 , and  67  is zero value of the up/down counter  61 .  
         [0087]     Using  FIG. 13  and  FIG. 14 , operation of the jitter signal generator  11  of this case of the operation is explained.  
         [0088]     At the up/down counter  61 , first, the output and record clock of a high frequency oscillator, Or if clocks, such as a system clock oscillated with crystal, are inputted, a rise count is carried out with a clock at first, the value goes up and maximum  66  is reached It is detected that it is maximum in the maximum detector circuit  62 , it is inputted into S (set) terminal of a flip-flop  64 , a flip-flop  64  is set, and the output is inputted into the up/down change input terminal of the up/down counter  61 , and changes to a down count. If it does so, the down count of the next is carried out with a clock, the value falls, if zero value  67  is reached, it will be detected that it is zero value in zero value detector circuit  63 , it will be used as R (reset) terminal of a flip-flop  64 , a flip-flop  64  is reset, and the output is inputted into the up/down change input terminal of the up/down counter  61 , and changes to a rise count. Thus, from the up/down counter  61 , the chopping sea of a digital signal is outputted, it is changed into the chopping sea of an analog signal with the DAC  65 , and the chopping sea is used as a jitter signal.  
         [0089]      FIG. 15  is a block diagram of the 2nd case of the operation of the jitter signal generator  11  used for the equipment of this invention,  
         [0090]      68  is a counter and  65  is a DAC.  
         [0091]      FIG. 16  is an explanation figure of  FIG. 15  case of the operation of the jitter signal generator  11  used for the equipment of this invention.  
         [0092]     Number  66  is maximum value of a counter  68 , and  67  is zero value of a counter  68 . Using  FIG. 15  and  FIG. 16 , operation of the jitter signal generator  11  of this case of the operation is explained.  
         [0093]     At a counter  68 , first, the output and record clock of a high frequency oscillator, Or if clocks, such as a system clock oscillated with crystal, are inputted, a rise count is carried out with a clock at first, the value goes up and maximum  66  is reached  
         [0094]     It overflows with the following clock, and becomes zero value, and it is repeated, from a counter  68 , the saw blade-like wave of a digital signal is outputted, it is changed into the saw blade-like wave of an analog signal with the DAC  65 , and the saw blade-like wave signal is used as a jitter signal.  
         [0095]     Here, the DAC  65  used for  FIG. 13  and  FIG. 15  may be a DAC of a  1 -bit input and  2  value output.  
         [0096]     Moreover, in order to divide a clock at a counter, to be able to use the signal through a digital analog low-pass passage filter as a jitter signal as composition of the jitter signal generator  11  and to avoid the step in every bit of the output of the DAC  65 , a low-pass passage filter can be added and a smooth jitter signal can also be acquired.  
         [0097]     Moreover, after carrying out false random number conversion of the output of a counter  68 , it is also possible by inputting into the DAC  65  to make move of frequency random and to eliminate the influence of the beat by a regular signal.  
         [0098]     This invention is applicable to the equipment which drives the equipment or the laser light emitting element which drives a laser light emitting element, and if it is what carried out high frequency superposition at the drive current, and the thing which carries out a switching drive, it is applicable not only to optical disk drive equipment but all the uses of a communication apparatus, the equipment for data reading, etc.