JPS644256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording device that irradiates a recording medium with a light beam such as a laser and records information such as a video signal by the heating effect caused by the irradiation of the light beam. .

Conventionally, as seen in the example of an optical video disk system, a signal is recorded on a disk-shaped recording medium (hereinafter referred to as a disk) as a concentric circle or a spiral recording trajectory as a binary signal such as unevenness or light and shade. Devices that perform high-density recording and reproduction are being considered. In such devices, recorded signals are subjected to FM modulation or PCM processing, converted into binary signals, recorded as recording pits on a disk, and then reproduced.

Further, in the case of such a recording/reproducing apparatus, the recording pit is generally minute, about 1 .mu.m in diameter, and the recording track pitch is also about 2 to 3 .mu.m, so that a large capacity signal recording/reproducing apparatus can be obtained.

In such a device, when a light beam such as a laser is used to record a signal as irregularities or dark and dark pits, the light beam is generally 1 μm in diameter.
The heat is focused below, and the heat causes unevenness on the recording medium and the formation of pits of light and shade. When creating a device using the above recording method to record and reproduce signals, the environment in which the device is used is generally not kept at a constant temperature, for example, in an environment with a temperature difference of about 0℃ to 40℃. You have to think about how it will be used.

If you try to record signals in a wide range of operating environment temperature conditions using a recording method that uses the heat of a light beam such as a laser, as described above, if the environment is low temperature, the recording will be insufficient. , in the case of high temperatures, there is a possibility that the light intensity of the light beam is too strong.

SUMMARY OF THE INVENTION An object of the present invention is to solve these drawbacks and provide an apparatus that can always record and reproduce signals of good quality even in a wide range of environmental temperatures.

First, with reference to FIG. 1, a conventional optical recording apparatus for recording and reproducing one frame of still images on one track of one rotation of a disk will be explained.

A video signal input from a signal input terminal 1 is processed by a signal processing circuit 2 and guided to a semiconductor laser drive circuit 3.

The light corresponding to the video signal emitted from the semiconductor laser 4 passes through a lens system 5, is reflected by a polarizing beam splitter 6, passes through a λ/4 plate 7, and is condensed through an aperture lens 8, and is directed to a disk. 10 and recorded. The focus element 9 moves the aperture lens 8 to follow the surface wobbling of the disk 10, so that the light beam is always focused on the disk 10.

On the other hand, during playback, the semiconductor laser 4 is operated to output light at a constant level that is weaker than during recording, and the light beam reflected from the disk 10 is
The light passes through the four plates 7, the polarizing beam splitter 6, and enters the light receiver 14.

The electrical signal output from the light receiver 14 is sent to the head amplifier 1.
5, passes through a signal processing circuit 16 including demodulation, and is output as a reproduced signal from a signal output terminal 17.

When recording one frame of NTSC images with one rotation of the disk using such a device, the motor 11 is
Rotate at 1800rpm. The one-rotation detector 12 detects one rotation of the motor 11, processes the signal in the one-rotation detection processing circuit 13, and supplies the one-rotation signal to the semiconductor drive circuit 3 when recording an image signal.
Semiconductor laser 4 transmits a signal of only one frame per rotation.
We are trying to supply it to If you do this,
One frame of image can be recorded in one rotation of the disk, and one image can be recorded one after another in one revolution of the disk.

When recording signals on the disk using the apparatus described above, the heat of a light beam, such as a laser, focused to 1 μm or less may be used to record the signal on the disk.

FIG. 2 shows an example of the irradiation power on the disk versus the reproduction output. In the case of a disk material exhibiting the characteristics shown in Figure 2, the signal recording and reproducing quality is poor when the irradiation power of the area is high, the signal recording and reproducing characteristics of good quality are obtained when the irradiation power of the area is In this case, the quality of signal recording and reproduction deteriorates due to, for example, evaporation of the material, although conditions differ slightly depending on the recording material used.

When trying to record and reproduce high-quality signals using such materials, the irradiation power must be selected in the range of , but since the heat of the light beam is used during recording, the operating environment temperature For example, 0℃
The region of can become substantially narrower at 40°C than at 40°C.

Conventionally, due to variations in the setting of irradiation power, variations in disk material, etc., there has been a problem that when the operating environment temperature is low, it falls into the area shown in FIG. 2, and when it is high temperature, it falls into the area .

The present invention proposes a method to eliminate such drawbacks.

FIG. 3 shows an embodiment of the present invention. In FIG. 3, the same numbers as in FIG. 1 indicate the same things.

In FIG. 3, the output of the temperature sensor 18 is
A sensor output processing circuit 19 performs circuit processing, and the processed output is guided to a semiconductor laser drive circuit 3, which controls the emission power of the semiconductor laser 4 to be high when the temperature is low and low when the temperature is high.

Next, we will explain the above controls in a little more detail.

FIG. 4 shows how the relational diagram of irradiation power versus reproduction output shown in FIG. 2 differs depending on the operating environment temperature. As can be seen from FIG. 4, in order to obtain reproduction output in a constant state, high irradiation power is supplied to the disk when the temperature is low, and low irradiation power is supplied to the disk when the temperature is high.

FIG. 5 shows a relationship between the supply current and the emission power of the semiconductor laser.

Normally, if a current is passed through a semiconductor laser around the current value shown in FIG. 5, the output power will vary from around this value.

By controlling the current center value from the outside, if a larger value is given, the light emitting power will be increased, and if a smaller value is given, the light emitting power can be decreased.

Therefore, with the output of the sensor output processing circuit 19 shown in Fig. 3, when the operating environment temperature is low, the current center value of is increased, and when the operating environment temperature is high, the current center value of is decreased to achieve the desired control. will be possible. A general bias control method can be used to control the current center value up and down, and a detailed explanation will be omitted here.

As described above, according to the present invention, a temperature detector for detecting the environmental temperature is arranged near the recording medium, and the intensity of the light beam is changed by the light beam intensity control means according to the output of the temperature detector. With this configuration, when trying to record and reproduce signals in a wide range of operating environment temperature conditions using a recording method that utilizes the heat of a light beam such as a laser,
A great effect can be achieved in that high-quality recording and playback can always be realized.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional optical recording and reproducing device that records and reproduces one frame of still images on one track of one rotation of a disk, Figure 2 is a diagram of the relationship between the irradiation power on the disk and the reproduction output, and Figure 3 The figure is a block diagram of an optical recording/reproducing device in one embodiment of the present invention, Figure 4 is a diagram explaining how the relationship diagram in Figure 2 changes due to changes in the operating environment temperature, and Figure 5 is a diagram showing how the relationship diagram in Figure 2 changes due to changes in the operating environment temperature. FIG. 3 is a diagram showing current versus light emission power. 3... Semiconductor laser drive circuit, 4... Semiconductor laser, 10... Disk, 18... Environmental temperature detector, 19... Sensor output processing circuit.

Claims (1)

[Claims] 1. A light beam whose intensity is modulated by a light beam intensity control means according to an information signal to be recorded is irradiated onto a recording medium having a recording layer on which recording is performed by heat generated by irradiation of a light beam, and a light beam in the vicinity of the recording medium is 1. An optical recording apparatus, characterized in that a temperature detector for detecting an environmental temperature is disposed in the temperature detector, and the intensity of the light beam is changed by the light beam intensity control means in accordance with the output of the temperature detector.