JPS6215Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical disc recording device, and more particularly to a focus servo for an optical disc.

In conventional optical disk recording, a laser is frequency-modulated with a recording signal and recorded on a disk master, etc., but it is necessary to perform focus servo to correctly connect a light spot on the disk master.

However, when recording with a laser, the photoresist of the disk master melts and the reflected light cannot be extracted, making it impossible to perform focus servo. For this reason, a method using an auxiliary laser for focus servo has been proposed.

However, this structure had the disadvantage that the optical system was complicated and accuracy was difficult to obtain. There are also systems that perform focus servo by extracting the reflected light until the spot is pierced without using an auxiliary laser, but this has the drawback that the error increases due to differences in recording frequency and relative speed with the disk, making it difficult to maintain accuracy. .

The present invention provides an optical disk recording device which eliminates the above-mentioned drawbacks, and which performs focus servo using reflected light from a recording laser without using an auxiliary laser. It is something that you are trying to gain.

For this reason, in the present invention, the output of the recording laser is output at the same output as during playback during the cut section other than the time used for recording, and only the focus servo error output at that time is extracted. be.

The details of the present invention will be explained below with reference to FIGS. 1 to 4. FIG. 1 shows a recording system, in which a laser beam from a light emitting means 3 such as a laser diode is passed through a beam splitter 4 and an objective lens 5 in order to connect a spot 2 to the upper surface of a disk 1.
The reflected light from the disk 1 is transmitted from the beam splitter 4 through the cylindrical lens 6 so as to be focused on the light receiving surface of a light receiving element such as a photodiode.

Figures 2A to 2C show the state of a reflective spot connected to the light-receiving surface of the light-receiving element 7. The light-receiving element is divided into four parts, the opposing electrodes are connected to each other, and the output of each connected pair is Added to differential amplifier 8 etc.
A focus control voltage is extracted from the output of the error dynamic amplifier. That is, in FIG. 2A, spot 2 is too close to the disk, and +V output is taken out, and the second
In Figure C, it is too far away and the -V output is taken out from the amplifier. FIG. 2b shows a case where the focus position is correctly set, and the output is 1V.

Each of the above outputs is proportional to the height between the disk and the spot, and is also proportional to the intensity of the laser reflected light, so normally a problem occurs where the servo gain changes due to the influence of the recording modulator. In the present invention, the detection circuit is configured as shown in FIG. That is, first, the recording modulation pulse shown in Figure 4A is connected to the terminal.
Add to mixing circuit 9 in addition to T ₁ . A bias voltage 〓 is applied to the terminal T ₃ of the mixing circuit so as to obtain the same laser output as during reproduction to obtain the superimposed waveform shown in FIG. Add to 10. As a result, holes are formed on the disk master 1 with the laser output corresponding to the pulse shown in FIG. 4A. The focus signal detection input shown in _FIG .

The sample hold circuit 11 is supplied with a signal obtained by inverting the recording modulation pulse by a phase inversion circuit 12.

In the above configuration, if the displacement (vertical fluctuation) of the disk surface is as shown in Figure 4 C, then the terminal
The waveform of the focus signal detection input applied to T ₂ (Fig. 4 D) corresponds to the bias voltage Ω when there is no recording modulation pulse, and the reflection becomes even more intense when there is a recording modulation pulse. It increases in size and becomes as shown in Fig. 4-2 (b).Next, as the disk master is burnt and holes are made, the reflected signal disappears and becomes as shown in Fig. 4-2-C.Here, the modulation pulse ( Figure 4 a) is phase inverted and used as a sample pulse,
When the focus signal detection input shown in Fig. 4D is sampled, the focus signal corresponding to the recording modulation pulse (b and c in Fig. 4D) is removed and the signal shown in Fig. 4E is obtained, which is independent of the presence or absence of holes. A zero focus detection signal is obtained at terminal _T4 .

Since the present invention is constructed as described above, in order to be able to extract a constant focus difference signal regardless of the modulation of the recording pulse, a stable focus difference signal can be obtained using the above signal without using a special focus laser. Focus servo can be performed. Further, in the above embodiments, a semiconductor laser is used as the laser source, but a laser source composed of a gas laser and a modulator may also be used. In other words, the modulator is on. If off-switching is to be performed, it is obvious that the laser beam in front of the modulator should be divided into two, modulated on one side, and then mixed.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the optical system of a conventional focus servo, Fig. 2 A, B, and C are plan views showing the shape of the focus surface in Fig. 1, and Fig. 3 is a system diagram of the present invention.
FIG. 4 is a waveform explanatory diagram of FIG. 3. In the figure, 1 is a disk, 3 light emitting means, 4 is a beam splitter, 5 is an objective lens, 6 is a cylindrical lens, 7 is a light receiving element, 8 is a differential amplifier, 9 is a mixing circuit, and 10 is a light beam. The light emitting element 11 is a sample and hold circuit.

Claims (1)

[Scope of utility model registration request] In an optical disk recording device that modulates the laser beam emitted from one laser emitting section to record on the disk and performs focus servo using the recording laser, the focus servo can be performed even in sections other than the laser recording section. 1. An optical disk recording device comprising means for emitting bias light to perform this, and means for performing focus servo by extracting a focus detection signal in a section other than the laser recording section.