JPS63214922A - Semiconductor laser driving circuit - Google Patents

Abstract

PURPOSE:To record a pit by which reliable read data with small quantity of jitter can be obtained by providing a logic circuit which generates the write data obtained by chopping the part of the write data longer than a gate signal length with a pulse wave from an oscillation circuit from the write data and outputs from a gate signal generation circuit and the oscillation circuit. CONSTITUTION:The write data 1 is inputted from a terminal 11 and the output signal 15 from the logic circuit 9 is the write data 2 which is the signal as it is if it is the signal shorter than a gate time T and which is obtained by chopping the part after T from a first transition with a signal 14 if it is longer than T. It is the write data 2 of the signal 15 that drives a semiconductor laser for the write data 1 of the signal 12, and the recorded pit becomes as long as the pit length which should be really recorded like 25-27. Thus, reproduced read data 28 becomes reliable on with small quantity of jitter, having no time lag by the pit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser drive circuit for an optical recording/reproducing device that records and reproduces information using a semiconductor laser as a light source.

[Conventional technology]

In a conventional optical recording/reproducing device using a semiconductor laser, when recording information, the semiconductor laser is driven by applying a pulse current based on external write data in addition to a bias current. There are two types of recording methods: pit position recording, in which information is recorded in the presence or absence of pits, and recording is performed by changing the interval between pits, and e-t length modulation recording, in which information is recorded in both ends of pits. In the case of pit position recording, the temporal length of each pit is always constant, but in the case of pit length modulation recording, the temporal length of each pit is modulated by data and changes.

[Problem that the invention seeks to solve]

However, in the above-mentioned prior art, a gap occurs between the pits to be recorded and the pits actually recorded, or the waveform of the recorded data. This situation is shown in FIG. 2. The reason for this is that pits are formed on the recording medium using thermal energy, that is, the bit portions are recorded by irradiating a high-power laser. However, since the heat is biased in the moving direction of the recording laser beam, the temperature rises too much at the end, resulting in a deviation of Lr and Lm between the read data 24 and the write data 12. This phenomenon is remarkable in pits with long pit lengths. Therefore, the read data obtained by reproducing the pits contains a lot of jitter and has low reliability, resulting in a worsening of the error rate.

The present invention is intended to solve these conventional problems, and its purpose is to provide a semiconductor laser drive circuit that can record pits with low jitter (reliable read data can be obtained). Our goal is to provide the following.

[Means for solving problems]

The semiconductor laser drive circuit of the present invention includes: (a) a semiconductor laser drive circuit for an optical recording and reproducing device that records and reproduces information using a semiconductor laser as a light source; (b) recording signal 1 (hereinafter referred to as write data 1); ); (e) an oscillation circuit that generates a pulse wave with a frequency sufficiently higher than the frequency band of the write data l; (d) ) From the write data 1 and the outputs of the gate signal generation circuit and the oscillation circuit, write data 2 is generated in which the portion of the write data 1 that is longer than the gate signal length T is tilofupped by the pulse wave from the /A oscillation circuit. and (e) a pulse current drive circuit that pulse-drives a semiconductor laser when recording information using the write data 2.

[Effect]

According to the above configuration of the present invention, compared to write data 1, write data 2 is longer than a certain time width T,
Since the latter half is cheated with high frequency, if you drive the semiconductor laser with this signal, the temperature of the recording medium will not rise too much at the end of the pit, and the pit length will be the same as the original write data. The read data is played back.

〔Example〕

FIG. 1 is a block diagram of a semiconductor laser drive circuit of the present invention,
FIG. 3 is a circuit diagram of the main parts in one embodiment of the present invention. A detailed explanation will be given below based on the drawings.

First, in FIG. m1, the optical output of the semiconductor laser 1 is monitored by the monophotodiode 2, and converted and amplified from a current signal to a voltage signal by the l-V conversion amplifier circuit 3, and the optical output is obtained as a voltage value. The difference between this value and the reference voltage 4 is taken by a differential amplifier circuit 5, and the difference is then changed from the set optical output.

Based on this difference signal, the bias current drive circuit 0 controls the bias current flowing through the semiconductor laser 1, so that the optical output of the semiconductor laser remains constant regardless of temperature changes, etc. a L i c I'
o wcr ConLrol) is performed.

Next, the operation during writing will be explained. In Fig. 1, a specific circuit diagram of the gate signal generation circuit 7, oscillation circuit 8, and logic circuit 1) which are the main parts of the present invention is shown in Fig. 3, and signal waveforms of each part are shown in Fig. 4. . Write data 1 is input manually from the terminal 11. This is the middle number 12 in Figure 4. The gate signal generation circuit 7 is composed of a one-shot multivibrator, and the gate time T is determined by a resistor R and a capacitor C. Write data 1 is input to the clock input terminal, a trigger is activated at the rising edge, and a signal with a time width T is output from the output terminal Q. (Signal 13)
On the other hand, the oscillation circuit 8 is realized using a crystal resonator in this case. (Signal 14) A portion 9 surrounded by a dotted line in the figure is a logic circuit, which is composed of an in/verter and a two-man AND gate. The output signal 15 of the logic circuit 9 is as shown in FIG.
Signals shorter than the gate time T are left as they are, and signals longer than the gate time T are ticked by the signal 14 from the rising edge, and this is write data 2. Based on the write data 2, the semi-3D body laser 1 is pulse-driven by the pulse current drive circuit 10 to record the write data. Alternatively, the gate signal generation circuit can be easily realized using a delay element (for example, a delay line).

〔Effect of the invention〕

As described above, according to the present invention, the following effects are brought about. In FIG. 4, write data 1 of signal 12
On the other hand, it is the signal that drives the semiconductor laser! 5 write data 2, the recorded bits are 25.2G,
It will look like 27. The length is the same as the bit length that was originally intended to be recorded, that is, it is equal to the time for write data 1. As a result, the reproduced read data 28 has no time lag with respect to the read data 24 due to pitting, and is highly reliable with fewer sicks. It goes without saying that the present invention is particularly effective in the case of a pit length modulation method in which information is provided at both ends of a pit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a semiconductor laser drive circuit according to the present invention. FIG. 2 is a diagram showing the relationship between write data, pits, and read data in a conventional example. Figure m3 is a specific circuit diagram of main parts in an embodiment of the present invention. FIG. 4 is a signal waveform diagram of each part of FIG. 3. 1...Semiconductor laser 2...Gate signal generation circuit 8...Oscillation circuit 0...Logic circuit or above Applicant: Seiko Epson Co., Ltd. Agent Patent attorney Tsutomu Mogami and 1 other person 4m

Claims (1)

[Claims] (1) (a) In the semiconductor laser drive circuit of an optical recording and reproducing device that records and reproduces information using a semiconductor laser as a light source, (b) the rising edge of recording signal 1 (hereinafter referred to as write data 1) (c) an oscillation circuit that generates a pulse wave having a sufficiently high frequency in the frequency band of the write data 1; (d) the write data 1 and the gate; a logic circuit that generates write data 2 in which a portion of write data 1 that is longer than the gate signal length T is chopped by a pulse wave from the oscillation circuit from the output of the signal generation circuit and the oscillation circuit; A semiconductor laser drive circuit comprising a pulse current drive circuit that pulse-drives a semiconductor laser during information recording using write data 2.