CN101303864A - Laser power control system of recordable CD-ROM drive and control method thereof - Google Patents

Abstract

The invention discloses a laser power control system and method for a recordable optical drive. A laser power control system is used for driving a laser diode to output write power through a first channel according to a write power value, and driving the laser diode to output overdrive power through a second channel according to setting of a proportional value. Furthermore, the write power and the over-drive power are not changed along with the change of the peripheral temperature through closed loop control. The accurate overdrive power can be determined by a calibration curve according to the write power value, the ratio value and the calibration curve.

Description

Laser power control system and control method for recordable optical drive

technical field

The present invention relates to a laser power control system and a control method of a recordable optical drive, and in particular to an overdrive power (Over Drive Power) control system and a control method of a recordable optical drive when data is written. .

Background technique

The write quality of an optical disc is closely related to the write strategy of the recordable optical drive. The so-called write strategy is the drive signal that controls the output power of the laser diode in the optical read-write head. Please refer to FIG. 1 , which is a schematic diagram of a writing strategy of a known recordable optical drive. As we all know, in order to form a mark (Mark) 10 on the track of the optical disc, the laser diode of the optical pickup must output a high-power beam and focus on the track, so that the track is heated rapidly to form a mark 10 . In order to make the mark 10 completely formed, therefore, the output power of the laser diode will be superimposed with an overdrive power (Over drivePower, Po) in addition to using a write power (WritePower, Pw) at the initial stage of forming the mark. , so that in the early stage of forming the mark 10, the track can be heated rapidly, and then the formed mark 10 is more complete. In other words, effectively controlling the magnitude of the overdrive power can effectively reduce the jitter value (Jitter) of the recordable optical drive during the process of writing data on the optical disc, and can effectively improve the writing quality of the optical disc. The recordable optical drive uses a read power (Read Power, Pr) when reading the data of the optical disc.

Before the recordable optical drive starts to write the data of the optical disc, the recordable optical drive will first perform the Optimum Power Calibration program (Optimum Power Calibration) in the test area (PowerCalibration Area) of the optical disc and obtain a write After the power is turned on, the data writing process of the optical disc will start. In order to allow the recordable optical drive to maintain a constant writing power during the data writing process, the recordable optical drive uses a closed-loop control system to maintain a constant writing power. Please refer to FIG. 2 , which is a schematic diagram of output power control of a laser diode in a conventional recordable optical drive.

Generally speaking, a recordable optical drive utilizes a digital representation of a writing power value to control the writing power outputted by the laser diode. An analog signal can be generated after the write power value passes through a first digital-to-analog converter (Digital Analog Converter, DAC1) 11 . Then, the compensator (Compensator) 12 will generate a compensation signal to the first laser driver (Laser Driver, LDD1) 14 according to the difference between the analog signal and the feedback signal so that the first laser driver 14 can generate the first driving current (I1) and use A first channel (CH1) is used to drive the laser diode (LD) 16 to output predetermined writing power. Of course, in order to maintain a constant writing power of the laser diode 16, the Front Monitor Diode (FMD) 18 can be used to receive the laser beam output by the laser diode 16 and generate a feedback signal to achieve the purpose of closed-loop control.

Moreover, in order to make the laser diode 16 output the overdrive power superimposed on the write power at a specific time, the recordable optical drive will additionally provide a digital overdrive power value to a second digital-to-analog circuit (DAC2) 20 , and the second laser driver (LDD2) 22 will generate a corresponding second driving current (I2) at a specific time according to the output of the second digital-to-analog circuit and use a second channel (CH2) to drive the laser diode (LD) 16 outputs predetermined overdrive power.

Since the overdrive power only occurs at a specific time, and the period of occurrence is very short, the recordable optical disc drive cannot perform closed-loop control of the overdrive power. It can be known from the illustration of FIG. 2 that the known recordable optical drive can only provide an overdrive power value for the overdrive power, and utilize open loop control to make the second laser driver (LDD2) 22 operate on the second channel ( CH2) provides a second driving current (I2) superimposed on the first driving current (I1) to drive the laser diode (LD) 16 .

As we all know, the temperature of a recordable optical drive will continue to rise during the process of writing data, and the output power of the laser diode will decrease with the increase of the peripheral temperature under the same driving current. Therefore, the closed-loop control can be used to increase the first driving current ( I1 ) as the temperature rises so as to achieve the purpose of maintaining a constant writing power. However, since the control of the overdrive power is an open-loop control, the second drive current (I2) cannot change with the change of temperature, so that the output overdrive power of the laser diode will decrease as the peripheral temperature rises. Therefore, there is a risk that the jitter value (Jitter) will deteriorate during the data writing process of the recordable optical drive and the writing quality will be degraded. In severe cases, the written data may even be unreadable. Therefore, how to control the overdrive power and improve the writing quality of the recordable optical drive will be the focus of the present invention.

Contents of the invention

The object of the present invention is to provide a laser power control system and control method for a recordable optical drive, so that the overdrive power can be precisely controlled and will not be affected by changes in peripheral temperature.

Furthermore, the present invention proposes a laser power control system for a recordable optical drive, which includes: a digital-to-analog circuit that receives a write power value and converts it into an analog signal; a compensator that combines the analog signal with a feedback The signal difference produces a compensation signal; a laser diode; a first laser driver can generate a first drive current to the laser diode according to the compensation signal so that the laser diode can generate a beam of writing power; a proportional control unit can By setting a proportional value, the proportional control unit generates an output signal; wherein, the output signal is the multiplication of the input signal by the proportional value; a second laser driver can generate a first laser driver in a time period according to the output signal Two driving currents are superimposed on the first driving current and make the laser diode generate a beam of overdrive power plus the write power; a front-end photodetection diode can be used to receive the beam output by the laser diode and generate the feedback signal and, a memory can store a calibration curve, the calibration curve records the relationship between a ratio between the overdrive power and the write power and the ratio value; wherein, the overdrive power is determined by the write power value, The proportional value, and the calibration curve are determined.

Moreover, the present invention further proposes a laser power control method for a recordable optical drive. The firmware used in the recordable optical drive can set a write power value and a laser power control system with a proportional value so that the laser power control The system drives a laser diode to output a write power through a first channel according to the write power value, and drives the laser diode to output an overdrive power through a second channel according to the setting of the ratio value, and the write power and The overdrive power will not change with the peripheral temperature. The laser power control method of the recordable optical drive includes the following steps: providing a correction curve, which is used to record the difference between the overdrive power and the writing power A relationship between a ratio and the proportional value; and, the magnitude of the overdrive power is determined by the write power value, the proportional value, and the calibration curve.

Description of drawings

In order for the examiner to further understand the features and technical content of the present invention, please refer to the following detailed description and accompanying drawings of the present invention. However, the attached drawings are only for reference and description, and are not intended to limit the present invention. Among them:

FIG. 1 is a schematic diagram of a writing strategy of a known recordable optical drive;

FIG. 2 is a schematic diagram showing the output power control of a laser diode in a known recordable optical drive;

FIG. 3 is a schematic diagram of laser diode output power control in the recordable optical drive of the present invention;

FIG. 4 is a schematic diagram of the calibration curve of the present invention.

Detailed ways

Please refer to FIG. 3 , which is a schematic diagram of output power control of the laser diode in the recordable optical drive of the present invention. After the written power value passes through the digital-to-analog circuit (DAC1) 110, an analog signal can be generated. Then, the compensator 112 will generate a compensation signal to the first laser driver (LDD1) 114 according to the difference between the analog signal and the feedback signal so that the first laser driver 114 can generate the first driving current (I1) and use a first channel (CH1 ) to drive the laser diode (LD) 116 to output a writing power. Furthermore, the front-end light detection diode (FMD) 118 can be used to receive the laser beam output by the laser diode 116 and generate a feedback signal to achieve the purpose of closed-loop control. Furthermore, the present invention also provides a proportional control unit (ProportionalElement) 120 to receive the compensation signal, and multiply the compensation signal by the proportional value (P) according to a proportional value (P) set in the proportional control unit 220 Provided to a second laser driver (LDD2) 122, so that the second laser driver (LDD2) 122 generates a corresponding second driving current (I2) and uses a second channel (CH2) to drive the laser diode (LD) 16 Output predetermined overdrive power.

Since the proportional control unit 120 can set the proportional value (P), the relationship between the overdrive power output by the laser diode and the write power can be maintained at the proportional value (P). That is to say, since the writing power is controlled in a closed loop, the first driving current ( I1 ) can change the magnitude of the first driving current according to the change of the peripheral temperature to maintain the writing power. Since the present invention adds the proportional control unit and sets the proportional value (P) in the proportional control unit 220 via the recordable optical drive firmware, the second driving current (I2) can also follow the change of the peripheral temperature and change, and can make the overdrive power not decrease with the increase of the peripheral temperature during the writing process of the optical disc data. Therefore, the present invention can prevent the jitter value of the recordable optical drive from deteriorating during the data writing process and maintain the excellent writing quality.

However, although the above-mentioned laser power control system can make the second drive current (I2) not cause the overdrive power to decrease with the rise of the peripheral temperature through setting the proportional value (P) of the proportional control unit 120, however, The above-mentioned laser power control system cannot accurately control the magnitude of the overdrive power. The reason is that the gains of the first channel ( CH1 ) and the second channel ( CH2 ) where the first laser driver ( LDD1 ) 114 and the second laser driver ( LDD2 ) 222 are located are not the same. That is to say, when the gains on the first channel (CH1) and the second channel (CH2) are different, the ratio between the write power and the overdrive power actually output by the laser diode of the recordable optical drive is not the same. is equal to the proportional value (P) set by the proportional control unit 120 .

In order to be able to accurately control the size of the overdrive power, the present invention adds a calibration curve to the recordable optical drive, which is generated after actual measurement and calibration before the recordable optical drive leaves the factory, and is recorded in the recordable optical drive. in the memory of the CD-ROM. Please refer to FIG. 4 , which shows a schematic diagram of the calibration curve of the present invention. The proportional value (P) and multiple write power values in the multiple proportional control units 120 are sequentially set through the firmware, and the actual output write power and overdrive of the laser diode are directly measured by a power meter (Power Meter). The ratio of power (Po/Pw) can obtain the calibration curve. That is to say, when the recordable optical drive is used to write the data of the optical disc after leaving the factory, using the calibration curve, the recordable optical drive can obtain accurate overdrive power according to the provided writing power value and the proportional value (P) , and this overdrive power will not change with the change of peripheral temperature. In this way, the purpose of the present invention to maintain the writing quality of the recordable optical drive can be achieved.

In summary, although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make various changes without departing from the spirit and scope of the present invention. and retouching, so the scope of protection of the present invention should be defined by the scope of the appended patent application.

Claims (2)

1. A laser power control system of a recordable optical drive, characterized in that, comprising: A digital-to-analog circuit, which can receive a write power value and convert it into an analog signal; a compensator, which can generate a compensation signal according to the difference between the analog signal and a feedback signal; a laser diode; A first laser driver, the first laser driver can generate a first driving current to the laser diode according to the compensation signal so that the laser diode can generate a beam of writing power; A proportional control unit, the proportional control unit can generate an output signal by setting a proportional value; wherein, the output signal is the input signal multiplied by the proportional value; A second laser driver, the second laser driver can generate a second drive current superimposed on the first drive current and make the laser diode generate an overdrive power plus the write power in a time period according to the output signal Beam; A front-end light detection diode, which can be used to receive the light beam output by the laser diode and generate the feedback signal; and a memory, the memory can store a calibration curve, the calibration curve records the relationship between a ratio between the overdrive power and the writing power and the ratio value; Wherein, the overdrive power is determined by the writing power value, the ratio value, and the calibration curve. 2. A laser power control method for a recordable optical drive, the firmware used in the recordable optical drive can set a write power value and a laser power control system with a proportional value so that the laser power control system according to the write The power value drives a laser diode to output a write power through a first channel and drives the laser diode to output an overdrive power through a second channel according to the setting of the ratio value, and the write power is not the same as the overdrive power It will change as the peripheral temperature changes, and it is characterized in that the laser power control method of the recordable optical drive includes the following steps: providing a calibration curve for recording the relationship between a ratio between the overdrive power and the writing power and the ratio value; and The magnitude of the overdrive power is determined by the write power value, the ratio value, and the calibration curve.

Images