JPH04106736A - Laser driving circuit for optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To obtain laser power equivalent to a set value by correcting a current value upon a variation of the current value due to a changeover of high frequency superimposing and a change of recording and reproducing power in using a memory recorded with a set power as an address and a correction value as a data. CONSTITUTION:When the high frequency superimposing (HF) is off, since a digital memory 104 is not selected by an HF on/off switch 103, an output of the memory 104 is zero. Recording power (Pw) is inputted also to a recording current setting circuit 105 to decide a current. Thus current is switched by a current circuit 107 in accordance with the recorded data 108, and a laser 109 is emitted. Then, when the HF is on, reproducing power (Pr) and the Pw are inputted to an address in the memory 104. Data of the memory 104 in contents is a difference between Iwon 204 when the HF is off and Iwoff 203 when the HF is off. When the HF is on, a value of a current to flow is increased, and this is added to the current of the circuit 107 after converting a correction data from the memory 104 at the address of the set Pr and Pw by a D/A converter 106. By this method, light power equivalent to the set value is obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a laser drive circuit for an optical recording/reproducing device.

[Prior Art] A laser drive circuit of a conventional optical recording/reproducing device will be explained based on the block diagram shown in FIG. The reproduction power is set by a reproduction power setting section 101 and the recording power is set by a recording power setting section 102. The recording current Iw 301 required to emit the recording power is the value obtained by dividing the recording setting power input to the recording current setting circuit 105 by the luminous efficiency of the laser 1 pLL (laser power per unit current).

The recording current Iw is switched by a current circuit 107 according to recording data 108 and is supplied to a laser 109. The emitted light from the laser 106 is monitored by a monitor photodiode 302 and subjected to current-to-voltage conversion, and then input to an automatic power control circuit 304 (hereinafter referred to as the A20 circuit), which uses a bias current Ib 305 to compensate for fluctuations in laser output caused by temperature fluctuations, etc. It was regulated by controlling.

[Problem to be solved by the invention] However, in the laser drive circuit of the conventional optical recording and reproducing device, the change in the luminous efficiency of the semiconductor laser when high frequency superimposition is performed is not corrected, so the emitted recording power is set. This has disadvantages in that the recording power is lower than the value of the recording power, and signals cannot be optimally recorded on the recording medium, and data remains unerased during erasing.

The present invention is intended to solve these problems, and its purpose is to maintain the recording and erasing power emitted from the laser even if the set optical power is changed or the high frequency superimposition is switched. It is an object of the present invention to provide a laser drive circuit for an optical recording/reproducing device that has an optical power equal to a set optical power.

[Means for Solving the Problems] A laser drive circuit for an optical recording and reproducing apparatus of the present invention is a laser driving circuit for an optical recording and reproducing apparatus that uses an optical pickup to record and reproduce information on an optical recording medium such as an optical disk or an optical card. In order to correct fluctuations in laser drive current that occur when performing high frequency superimposition, there is a digital memory that uses the values of the reproduction laser power and recording laser power as addresses and records correction values as data, and a digital memory that converts the correction values into analog values. It is characterized by comprising an A converter and a current circuit that adds the correction value to the current value when high frequency superimposition is not performed to obtain a drive current.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings. First, the current-optical power characteristics (hereinafter abbreviated as IP characteristics) of a semiconductor laser will be explained using FIG. 2. In FIG. 2, the horizontal axis represents current, and the vertical axis represents laser emission power. 201 is the I-P characteristic when high frequency superimposition is not performed, and 202 is the I-P characteristic when high frequency superimposition is performed. The r-P characteristic 201 when high frequency superimposition is not performed has the same nonlinear characteristic as a diode, and the current is the threshold current I th20
When the value exceeds 5, the optical power increases linearly with a constant slope.

Next, the I-P characteristic when high frequency superimposition is performed is that the drive current is modulated with high frequency, so as in the I-P characteristic of 202, light emission starts from a lower current value compared to 201, and as the power increases. Therefore, it gradually approaches 201. Therefore, unlike the case where high frequency superimposition is not performed, the luminous efficiency when high frequency superimposition is performed is not a constant value, but changes depending on the value of recording and reproducing power.

When high-frequency superimposition is not performed, the current required during recording is determined by dividing the optical power of Pw by the luminous efficiency (current required to output unit laser power, i.e., linear It can be uniquely determined by the value divided by the slope). For example, Pw=5mW, luminous efficiency 50 uW
/mA, the drive current will be 10mA. However, when high frequency superimposition is performed, the luminous efficiency is not constant, so even if the PW value is the same, the current value required during recording changes depending on the value of the reproducing power. When determining the recording sensitivity of a recording medium such as an optical disk or the characteristics of an optical pickup with an appropriate reproduction power, it becomes necessary to change the reproduction power or change the high frequency superimposition to N/FF. An embodiment for solving this problem will be explained in detail using FIG. 1.

In FIG. 1, the reproduction power Pr and the recording power Pw are digitally set by a reproduction power setting section 101 and a recording power setting section 102. For example, 0.1m per 1 bit
Set the optical power as W.

If high frequency superposition is not performed, HF ON10 FF
Since the switch 103 does not select the digital memory 104, the output of the digital memory 104 is always O.

The recording power is also input to a recording current setting circuit 105 to uniquely determine the current.

This current is switched in a current circuit 107 according to recorded data 108, and a laser 109 emits light.

Next, when high frequency superimposition is ON, the reproduction power and recording power are input to the address of the digital memory 104. The content of the data in the digital memory 104 is the difference between Iwon 204 when high frequency superimposition is ON and Iwoff 203 when high frequency superimposition is OFF, as shown in FIG. As described above, when high frequency superimposition is ON, the current value to be passed increases. Correction data is output from the digital memory 104 using the set reproduction power and recording power as addresses. This data is added as an analog value to the current value of the current circuit 107 by the D/A converter 106, and optical power equal to the set value is obtained.

[Effects of the Invention] As explained above, when the laser drive circuit of the optical recording/reproducing apparatus of the present invention is used, the fluctuation of the current value caused by switching the high frequency superimposition or changing the recording/reproducing power can be adjusted by using the set power as an address and adjusting the correction value. By correcting the current value using a digital memory that records the data as data, it becomes possible to obtain a laser power equal to the set value, so data can be recorded and erased with high reliability.

Furthermore, individual differences in lasers can be easily corrected by changing the data in the digital memory.

Furthermore, when evaluating the recording/reproducing characteristics of an optical disk or the performance of an optical pickup, it is possible to switch high frequency superimposition and change the recording/reproducing power without adjustment, thereby providing useful data.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a laser drive circuit of an optical recording/reproducing apparatus according to the present invention. Figure 2 shows the optical power of the laser for explaining the present invention.
A diagram showing current characteristics. FIG. 3 is a block diagram of a laser drive circuit of a conventional optical recording/reproducing device. ot Reproduction power setting section Recording power setting section HF0N10FF switch Digital memory recording current setting circuit D/A converter current circuit Recording data laser Higento Seiko Epson Co., Ltd. Agent Patent attorney Kizobe Suzuki (and 1 other person) Iwon: 204

Claims (1)

[Claims] In the laser drive circuit of an optical recording and reproducing device that uses an optical pickup to record and reproduce information on optical recording media such as optical disks and optical cards, the reproduction laser power and the A digital memory that uses the recording laser power value as an address and records the correction value as data, a D/A converter that converts the correction value into an analog value, and a drive current that adds the correction value to the current value when high frequency superimposition is not performed. A laser drive circuit for an optical recording/reproducing device, characterized by comprising a current circuit having the following characteristics: