JPH0411334A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To promote the recording performance by raising a bottom level with a bottom level varying means when recording power of a semi-conductor laser is lowered and the recording performance is insufficient. CONSTITUTION:One part of a regenerative signal is detected by a regenerative signal amplitude detecting circuit 11, and a value of a reference voltage Vb of a comparator 6b for setting the bottom level in accordance with the output state of the above detected signal is in creased or decreased. Consequently, a value of a signal inputted from a bottom power detecting circuit 6a to the comparator 6b is controlled to be coincident with the value of the reference voltage Vb by a bottom power control circuit 6c. That is, when an amplitude of the regenerative signal is lowered due to adherence of dust, etc., the control is performed in order to increase a value of bottom power Pb. By this method, the recording performance of an optical information recording medium is promoted, and the accurate recording is feasible.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical information recording/reproducing apparatus equipped with a laser pressure power dividing circuit for a laser light source.

BACKGROUND OF THE INVENTION Conventionally, in optical information recording and reproducing devices, when dust or the like adheres to an objective lens, the amount of light emitted from a semiconductor laser as a laser light source decreases, and this deteriorates the recording characteristics of an optical disk as an optical information recording medium. The phenomenon of deterioration has become a problem.

Therefore, in the past, various devices have been devised to deal with such dust. For example, the first conventional example is disclosed in Japanese Patent Laid-Open No. 60-74130. In this method, a photodetector is placed at a position facing the laser beam emitting part of the semiconductor laser that constitutes the optical head when no recording or playback is being performed on the optical disc.
This photodetector is covered with a cover. Thereby, it is possible to prevent dust and the like from adhering to the laser beam emitting section, and also to notify that cleaning is necessary when dust and the like have adhered to the laser beam emitting section.

In addition, as a second conventional example, Japanese Patent Application Laid-Open No. 60-8323
There is something disclosed in Publication No. 4.

This is the square wave duty (
A detection means for detecting the duty ratio is provided, and a control means is provided for controlling the intensity of the laser power of the laser drive means for driving the semiconductor laser according to the output of the detection means. With this, a signal with a constant frequency is recorded in advance on a predetermined track before data is recorded, and the bias value of the laser recording power is changed according to the duty ratio of the signal that reproduces the recorded data. When the ratio reaches 50%, the data recording operation is performed while maintaining the recording power state, so even if the sensitivity of the recording surface on the information track of the optical disc is different, good data recording and reproduction can be achieved. It becomes possible to do two things.

Problems to be Solved by the Invention In the conventional device as described above, first, in the case of the first conventional example, the surface of the lens must be cleaned when dust or the like is detected by the photodetector. However, providing such a linting mechanism would be very cumbersome and expensive. Additionally, if the user cleans the lens carelessly, there is a risk of damaging the surface of the lens, which may require special precision cleaning equipment and increase maintenance costs for the cleaning equipment. there is a possibility.

Furthermore, in the case of the second conventional example, the output of the semiconductor laser used as the laser light source is limited by the absolute maximum rated output of the element. If the semiconductor laser is emitted in excess of this rated value, the semiconductor laser may be destroyed and the device itself may suffer irreparable damage. In addition, as in this conventional example, when the recording power is set so that the duty ratio is 50% by looking at the reproduced signal, the amount of emitted light decreases due to the adhesion of dust, etc., and as a result, the recording performance decreases. In such cases, the output of the semiconductor laser is set to increase the recording power, and the peak value of the recording power will eventually exceed the absolute maximum rated output, destroying the semiconductor laser. This will lead to a situation.

Means for Solving the Problems In order to solve these problems, the present invention focuses light emitted from a laser light source using an objective lens to form a minute light spot on the surface of an optical information recording medium. In an optical information recording and reproducing device that records and reproduces information by forming a Recording level light emitting means for emitting light emitted from a light source at a recording level is provided, and bottom level light emitting means for emitting light emitted from a laser light source at a bottom level relatively lower than the recording level when recording information is provided. A bottom level variable means is provided for detecting the recording state of information and changing the bottom level of the bottom level light emitting means in accordance with the detected output state.

Effect: Therefore, when the recording power of the semiconductor laser decreases due to adhesion of dust, etc. and the recording capacity becomes insufficient, the bottom level is increased by the bottom level variable means, thereby increasing the preheating effect of the semiconductor laser and further improving the recording capacity. becomes possible.

Example An embodiment of the present invention will be described based on the drawings.

First, the overall configuration of this embodiment will be described based on FIG.

A laser drive circuit 2 is connected to a semiconductor laser 1 serving as a laser light source, and a modulation circuit 3 is connected to the second laser drive circuit 2. Further, a recording level light emitting means 4, a reproduction level light emitting means 5, and a bottom level light emitting means 6 are connected to the laser driving circuit 2 to drive and control the laser driving circuit 2, respectively. The recording level light emitting means 4
teeth.

It consists of a recording power detection circuit 4a, a comparator 4b, and a recording power control circuit 4c. Further, the reproduction level light emitting means 5 includes a reproduction power detection circuit 5a, a comparator 5b, and a reproduction power control circuit 5c. Further, the bottom level light emitting means 6 includes a bottom power detection circuit 6a, a comparator 6b, and a bottom power control circuit 6c.

Further, a light receiving element 9 for detecting reflected light from an optical disk 8 as an optical information recording medium is provided in the optical pickup section 7 in which the semiconductor laser 1 is housed. 10 is connected to a reproduced signal amplitude detection circuit 1 as bottom level varying means. This reproduced signal amplitude detection circuit 11 is connected to the comparator 6b constituting the bottom level light emitting means 6.

Furthermore, a monitor light receiving element 1 is provided in the optical pickup section 7.
2 is built-in, and this monitor light receiving element 12 is connected to the recording power detection circuit 4a and the reproduction power detection circuit 5a.
and the bottom power detection circuit 6a, respectively.

In such a configuration, the light emitted from the semiconductor laser 1 in the optical pickup section 7 is transmitted through the collimating lens 13.
A part of the light is reflected by the beam splitter 14 and detected by the monitor light receiving element 12, while the remaining light continues straight and is focused by the objective lens 16 via the wavelength plate 15. Optical disk 8
form a light spot on the surface of the And optical disc 8
The reflected light is reflected by the beam splitter 14, focused by the condensing lens 17, and detected by the light receiving element 9. The detected signal is converted into an electrical signal and sent to the demodulation circuit 10 for reproduction, thereby making it possible to obtain a reproduction signal for data.

Furthermore, data can be recorded by driving the laser drive circuit 2 using a modulation signal from the modulation circuit 3 to change the intensity of the laser light, thereby causing a physical or scientific change on the optical disk 8. can.

FIG. 2 shows the state of light intensity in the recording mode and reproduction mode of the modulated signal. The playback level of light intensity in playback mode is Pr (playback power), the recording level of light intensity in record mode is Pw (recording power), and the bottom level of light intensity weaker than these is Pb (bottom power).
Then, these generally have a relationship of Pw>Pr>Pb.

Then, when the output of the laser light from the semiconductor laser 1 is detected by the monitor light receiving element 12, among the detected signals,
The light intensity at the recording level of Pw is detected by the recording power detection circuit 4a, the light intensity at the reproduction level of Pr is detected by the reproduction power detection circuit 5a, and the light intensity at the bottom level of pb is detected by the bottom power detection circuit 6a. Ru. In this case, Pw
, Pr, the level signals corresponding to the respective comparators 4b,
5b, and the outputs from these comparators 4b and 5b are sent to a recording power control circuit 4c and a reproduction power control circuit 5c, respectively. These recording power control circuit 4c and reproduction power control circuit 5c each have a reference voltage Vw at a level corresponding to pw and Pr.
, Vr, the semiconductor laser drive path 2 is controlled so that the levels of Pw and Pr are stabilized, thereby making it possible to perform normal recording and reproduction.

Next, the function of the reproduced signal amplitude detection circuit 11 will be described. Since the monitor light receiving element 12 is built in the optical pickup unit 7, its output does not change even if dust or the like adheres to the objective lens 16. Therefore, the output power from the semiconductor laser 1 does not change, and the amount of light after passing through the objective lens 16 with the dust attached decreases, and the recording power of the laser beam that is opened onto the optical disk 8 decreases. There will be a shortage. If the recording power is insufficient,
As shown in FIG. 3, the reproduced signal that is the output of the light receiving element 9 at this time is the amplitude W of the signal waveform A when performing normal recording.
The signal waveform B becomes a signal waveform B whose amplitude wb is significantly smaller than that of a. Note that the reason why the level of the signal waveform B decreases is that the objective lens 16 is dirty and the optical disc 8
This is because the reflected light from the source also decreases, which causes the reproduced signal level to decrease as well.

Therefore, in order to prevent a drop in the level of the reproduced signal due to such insufficient recording power, in this embodiment, a part of the reproduced signal is detected by the reproduced signal amplitude detection circuit 11, and the output state of the detected signal is adjusted according to the output state of the detected signal. , the reference voltage vbO value of the comparator 6b for setting the bottom level Pb is increased or decreased. Thereby, the value of the signal input from the bottom power detection circuit 6a to the comparator 6b is controlled by the bottom power control circuit 6c so as to match the value of the reference voltage vb. That is, when the amplitude of the reproduced signal decreases due to adhesion of dust, etc., the PbO value is controlled to increase.

As mentioned above, even if the recording power of the semiconductor laser decreases due to adhesion of dust and the recording capacity is insufficient, by increasing the bottom level Pb, it is possible to increase the preheating effect of the semiconductor laser 1 and further improve the recording capacity. It becomes possible. Furthermore, in the method of increasing the recording power using a method such as the second conventional example, the upper limit is limited by the maximum rating of the semiconductor laser, whereas in the method of this embodiment, the bottom power Pb is lower than the recording power Pw. Since Pb is also small, the emission limit of the semiconductor laser 1 is determined by Pw, and as a result, even if the value of Pb is increased, the semiconductor laser 1 will not be destroyed and the reliability of the single component can be further improved. can.

Note that the method for detecting a decrease in recording performance due to adhesion of dust, etc. is not limited to the method described in this embodiment. Alternatively, the duty of the reproduced signal may be detected. Also, P
The method of controlling each level of w, Pr, and Pb is not limited to the method of this embodiment.

Finally, by using the configuration as in this example (see Figure 1), we will discuss the effects specifically obtained from the experimental results in the fourth example.
Let me explain based on the diagram. Figure 4(a) shows the appropriate Pw
, Pb shows a reproduced signal (eye pattern) when recording is performed with Pb. FIG. 4(b) shows the state of the reproduced signal when Pw and Pb are reduced due to adhesion of dust or the like. FIG. 4(c) shows a situation in which specific effects of this embodiment are produced. That is, P with the same Pw as in Fig. 4(b)
This shows the situation when only b is increased, and by comparing FIG. 4(c) with FIG. 4(b), it can be confirmed that the eye pattern has been improved.

Effects of the Invention The present invention provides an optical information recording and reproducing method that records and reproduces information by condensing light emitted from a laser light source using an objective lens and forming a minute light spot on the surface of an optical information recording medium. In the apparatus, there is provided a reproduction level light emitting means for emitting light emitted from a laser light source at a reproduction level when reproducing information, and a recording level light emitting means for emitting light emitted from a laser light source at a recording level when recording information. and a bottom level light emitting means for emitting light emitted from a laser light source at a bottom level relatively lower than the recording level when recording information, detects the recording state of information and responds to the detected output state. Since the bottom level variable means is provided to change the bottom level of the bottom level light emitting means, even if the recording power of the semiconductor laser decreases due to adhesion of dust etc. and the recording capacity is insufficient, the bottom level variable means can be used to change the bottom level. By increasing the level, the preheating effect of the semiconductor laser can be increased, thereby further improving the recording ability of the optical information recording medium and making it possible to perform accurate recording.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the present invention, Fig. 2 is a waveform diagram showing how the light intensity of the laser beam changes in each mode of the modulation signal, and Fig. 3 is a waveform diagram showing changes in the light intensity of the laser beam in each mode of the modulation signal. FIG. 4 is an explanatory diagram showing the state of the reproduced signal when there is a shortage, and FIG. 4 is a waveform diagram showing a specific experimental example in which the eye pattern changes depending on the presence or absence of dust. 1... Semiconductor laser, 4... Reproduction level light emitting means,
5... Recording level light emitting means, 6... Bottom level light emitting means, 8... Optical information recording medium, 11 - Bottom level variable means, 16... Objective lens, Pw... Recording level, Pr... Reproduction level, Pb/bottom level ○shi 1
death

Claims (1)

[Claims] In an optical information recording and reproducing apparatus that records and reproduces information by condensing light emitted from a laser light source with an objective lens to form a minute light spot on the surface of an optical information recording medium, the information is reproduced. providing a reproduction level light emitting means for emitting light emitted from the laser light source at a reproduction level when recording the information, and providing a recording level light emitting means for emitting light emitted from the laser light source at a recording level when recording the information; Bottom level light emitting means is provided for emitting light emitted from the laser light source at a bottom level relatively lower than the recording level when recording the information, detecting the recording state of the information and adjusting the detected output state. An optical information recording and reproducing apparatus characterized in that a bottom level variable means is provided for changing the bottom level of the bottom level light emitting means accordingly.