JPS60243832A - Optical information detecting device - Google Patents

Abstract

PURPOSE:To make the S/N ratio of read signals higher and, at the same time, to prevent deterioration of an optical information recording medium, by irradiating a laser light of a frequency higher than the reading frequency upon the optical information recording medium at the time of reproduction. CONSTITUTION:In this optical disk device, a semiconductor laser 1 is driven at a duty ratio 50% when information is reproduced and an output B having power which is about twice conventional fixed output power A is intermittently emitted at a duty ratio 50%. The quantity of light C reflected at this time in accordance with the condition of pits 9 provided on an optical disk 6 becomes larger than the conventional reflecting quantity of light D and is intermittent at a duty ratio 50% and, therefore, information signals recorded by means of the pits 9 are detected when detected signals from a photoreceptor element 7 are peak-held. The S/N ratio of this information signal becomes sufficiently high because the peak of the reflecting quantity of light C is high and, at the same time, deterioration of the optical disk can be prevented since the quantity of exposure of the optical disk is not changed from conventional ones.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optical information detection device that reads information from an optical information recording medium.

(Prior Art) Conventionally, as an optical information detection device, an optical disk device uses an optical pickup to detect an optical disk. FIG. 1 shows an example of the optical pickup. The light beam from the semiconductor laser 1 is converted into parallel light by a coupling lens 2, and is irradiated onto an optical disc G as a minute spot 1 by an objective lens 5 via a polarizing beam splitter 3' and a quarter-wave plate 4.

The reflected light from the optical disk 6 is treated as an objective L/lens 5,1//1 wavelength4. The light is received by the light receiving element 7 via the polarizing beam splitter 3, and information prerecorded on the optical disc 6 is read as the difference in the amount of reflected light. Here, information is recorded by forming holes 9 of 1 to 2 μm called pinot 1 in the guide groove 8 formed in advance in the optical disk 6, as shown in FIG. is different from the non-pill section. Generally, this information is recorded by increasing the output power of the semiconductor laser 1 by about 10 times as compared to that during information reproduction to form pits 9 in the guide grooves 8. When reproducing information, the semiconductor laser 1 irradiates the optical disk 6 with as low output power as possible in order to prevent deterioration due to irradiation with the output power of the semiconductor laser 1 on the optical disk 6. However, in this optical disk device, the output power of the semiconductor laser 1 is minimized when reproducing information. Because it will be lower.

The S/N of the read signal from the light receiving element 7 is not high enough.

(Objective) An object of the present invention is to provide an optical information detection device that can sufficiently increase the S/N of a read signal and at the same time prevent deterioration of an optical information recording medium.

(Structure) The present invention will be described below based on embodiments with reference to the drawings.

In the present invention, for example, in the above-mentioned optical disk device, when reproducing information, the semiconductor laser 1 is driven at a duty ratio of 50%, and as shown in FIG.
Output B with twice the power is intermittently emitted at a duty ratio of 50%. At this time, as shown in FIG. 5, the amount of reflected light C depending on the presence or absence of pits 9 on the optical disc 6 is similarly larger than the amount of conventional reflected light and is intermittent at a duty ratio of 50%, so that the amount of reflected light from the light receiving element 7 is By peak-holding the detection signal, an information signal depending on the presence or absence of the pit 9 is detected. The S/N ratio of this information signal is sufficiently high because the peak of the reflected light amount C is high, and deterioration of the optical disk is prevented without changing the exposure amount of the optical disk from the conventional one.

Further, the semiconductor laser 1 is driven at a duty ratio other than 50% to intermittently emit an output E having a power greater than the conventional constant output power A at a duty ratio other than 50% as shown in FIG. The exposure amount of No. 6 may be set to be approximately the same as that of the conventional method.

Also, the detection signal from the light receiving element 7 is peak held and S/
In order to obtain a high N information signal, the output of the semiconductor laser may be a high frequency wave such as a sine wave instead of a rectangular wave. The modulation frequency of the semiconductor laser 1 needs to be at least twice the frequency of the information signal (information reading frequency), and in order to prevent the optical disk 6 from melting due to the irradiation of the output of the semiconductor laser 1, 5 of the frequency of the signal
It is desirable to make it ~10 times or more.

FIG. 6 shows an embodiment of the present invention, and FIG. 7 shows waveforms of various parts thereof. When reproducing information in the optical disk device, the semiconductor laser is driven at a high frequency by the high frequency drive circuit 10, and this high frequency is set sufficiently higher than the information reading frequency as described above. An optical pickup 11 including a semiconductor laser 1 sends a very small output of the semiconductor laser 1 to an optical information recording medium 6 consisting of an optical disk on which information has been recorded in advance by forming pits 9 in a guide groove 8 and is rotationally driven by a motor. The light is irradiated along the guide groove 8 as a spot, and the reflected light is received by the light receiving element 7 and converted into a photocurrent. This photocurrent is detected by a photocurrent detection circuit 12, converted into a voltage, and peak-held by a peak hold circuit 13, thereby detecting an information signal. This information signal has the same high-power waveform as that emitted from the semiconductor laser 1 during information recording, passes through a bandpass filter 14, is waveform-shaped by a waveform shaping circuit 15, and becomes a binary signal.

Note that an optical pickup circuit is indispensable in an optical disk device, and the present invention is applied to this optical system and circuit to drive a semiconductor laser at high frequency and peak-hold the detection signal from the light receiving element, thereby achieving S/P. Error detection with a high number of N can be performed.

(Effects) As described above, in the optical information detection device according to the present invention, the detection signal from the light receiving element is held at its peak by irradiating the information recording medium with a laser beam modulated at a frequency higher than the information reading frequency. , the peak of the laser beam can be raised to increase the read signal S/N, and at the same time, the amount of exposure of the optical information r2@ medium can be reduced to prevent deterioration of the optical information recording medium.

[Brief explanation of drawings]

Fig. 1 is a side view showing a conventional optical pickup, Fig. 2 is a perspective view showing a part of an optical disc, Figs. 3 and 4 are waveform diagrams showing output waveforms of a semiconductor laser, and Fig. 5 is a diagram of an optical disc. FIG. 6 is a diagram showing reflected light in relation to a pit, and FIG. 6 is a diagram showing it in relation to a button showing an embodiment of the present invention. 10... High frequency drive circuit, 13... Peak hold circuit.

Claims (1)

[Claims] In an optical information detection device that irradiates an optical information recording medium on which information has been recorded in advance with one laser beam in minute spots, and reads information by receiving reflected light from the optical information recording medium with a light receiving element. , means for irradiating the optical information recording medium with laser light modulated at a frequency higher than the information reading frequency; and means for peak-holding the detection signal from the light receiving element. Information detection device.