JPH0434726A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To promote the recording density of information on a recording medium and to increase the recording capacity of the recording medium by making an amt. relative to an light beam changeable for each information unit of information to be recorded to the recording medium with the light beam to be led by an optical means. CONSTITUTION:A regenerative signal processing circuit 29 consists of an amplifier circuit 291, a position detecting circuit 293 to be connected with this amplifier circuit 291 and a peak value detecting circuit 295. That is, after a pit signal S13 to be inputted from an optical head 5 is amplified to a prescribed value, a position detecting signal S15 showing a position of the pit signal S13 is outputted by the position detecting circuit 293 to a controller 30, while when the peak value of the pit signal S13 exceeds a prescribed value, a peak signal S17 is outputted by the peak value detecting circuit 295 to the controller. Consequently, in the controller, the presence of a pit and a depth of the pit, namely, two bits of information of a recording level can be obtained from these position detecting signal S15 and peak signal S17. By this method, the high density recording of information can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to an optical recording/reproducing device that is capable of writing information onto a recording medium at high density.

(Prior art) Conventionally, signals are recorded by irradiating a light beam such as a laser beam.
Optical discs are examples of reproducible and erasable recording media. In addition, as the optical disk, generally known are magneto-optical type, phase change type, organic dye recording film type, and the like.

In addition, these optical discs are usually formed with a light beam guiding means such as a guide groove, and the signal is transmitted from the track formed in either the concave part, that is, the group part, or the convex part, that is, the land part that forms the guide groove. In addition, the binarized information obtained by binarizing the information to be recorded is recorded depending on the presence or absence of bits.

(Problems to be Solved by the Invention) As mentioned above, conventional optical discs recorded signals only depending on the presence or absence of pits. Therefore, if the pitch between tracks etc. is constant, the amount of information that can be recorded on an optical disc is It has become highly dependent on the area of

Furthermore, when a recording medium with a narrow linearity as shown in Figure 6 is used, even if different optical outputs are applied as shown in Figure 7, the peak value will fall into the saturation region and the waveform will be distorted. In some cases, the reproduced signal could not be detected because of the

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an optical recording/reproducing device that can increase the recording density of information on a recording medium and increase the recording capacity of the recording medium.

[Configuration of the Invention (Means for Solving the Problems) In order to solve the above problems, the optical recording/reproducing device provided by the present invention includes a light-emitting source that generates a light beam, and a light beam generated from the light-emitting source. The object of the present invention is to have an optical means for guiding the light beam to a recording medium, and a changing stage capable of changing the amount of the light beam guided by the optical means for each information unit of information recorded on the recording medium with the light beam guided by the optical means. do.

(Function) In the optical recording/reproducing apparatus of the present invention, when recording information on a recording medium with a light beam generated by a light emitting source and guided by an optical means, the changing means changes the amount of the light beam,
For example, the optical output, pulse width, or pulse interval may be changed.

(Embodiment) Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

First, the configuration of an optical disk device according to an optical recording/reproducing apparatus of the present invention will be explained with reference to FIG.

The optical disc 1 as a recording medium is, for example, an overridable phase change type disc, and mainly includes a recording layer in which signals as information are recorded, and a transparent material such as glass, polycarbonate, or PMMA (transparent acrylic resin). It is composed of a disk substrate 1b. In addition, tracks are formed in the recording layer formed on one side surface of the disk substrate in the form of concentric circles or spirals, usually at intervals of 1.6 μm, and signals are formed as bits on these tracks. The optical disc 1 is placed on a turntable (not shown) and is rotated by a spindle motor 3. An optical head 5 is arranged below the optical disk 1 to face it.

Next, the internal configuration of the optical head 5 will be explained in detail.

The semiconductor 7 is a light emitting source that generates a laser beam as a light beam, and the laser beam emitted from the semiconductor laser 7 is incident on a collimator lens 9, converted into parallel light, and sent to a polarizing beam splitter 11. Output to.

The polarizing beam splitter 11 transmits and reflects incident laser light.

Laser light incident on this polarizing beam splitter 11 from the semiconductor 7 side is reflected by the polarizing beam splitter 11,
The light is further converged by the objective lens 13 and focused on the recording layer of the optical disc 1.

The objective lens 13 is provided so as to be movable in both the tracking direction, which is the radial direction of the optical disc 1, and the focusing direction, which is a direction perpendicular to the surface of the optical disc. That is, a focusing coil 13a and a tracking coil 13b for moving this objective lens 13.
is provided. By passing a current to the focusing coil 13a, the objective lens 1
3 can be moved in the focus direction. Similarly, by passing a current to the tracking coil 13b, the objective lens 13 is adjusted according to the current value.
can be moved in the direction of the track.

The laser control circuit 15 is connected to the semiconductor laser 7 built into the optical head 5 and controls the semiconductor laser 7.

The laser light transmitted through the polarizing beam splitter 25 is
The shape of the beam in a cross section perpendicular to the optical axis is changed by a cylindrical lens 19 via a lens system 17, and the beam is incident on a detector 21.4>This detector 21 includes a 4-split photodetector 21a.

21b, 21c, and 21d are used, and the laser beam is located at a position where the cross-sectional shape of the laser beam emitted from the cylindrical lens 19 becomes a perfect circle when the laser beam is focused on the recording layer of the optical disc 1, that is, in the focused state. The center of the perfect circle and the center of the four-part photodetector 21 are arranged to match. Therefore, when in focus, the signal levels from the four photodetectors are the same. On the other hand, in the out-of-focus state, the position where the cross-sectional shape of the laser beam emitted from the cylindrical lens 19 is a perfect circle is shifted in the optical axis direction, and the laser beam with an elliptical cross-sectional shape is incident on the 4-split photodetector 21. The photodetector is on the diagonal.

For example, the outputs of the photodetectors 21a and 21c or the photodetectors 21b and 21d are the same, and the outputs of adjacent photodetectors, such as photodetectors 21a, 21b, and 21d, differ. Therefore, when out of focus, an output corresponding to the distance to the optical disc 1 can be obtained. on the other hand,
When the irradiation position of the laser beam is on one side of the land or group, the outputs from two adjacent photodetectors are the same, and when part of the laser beam is applied to the adjacent group or land, The laser light is scattered, and the output of the photodetector on the side where it is applied is reduced (push-pull method).

In addition, in this embodiment, since the astigmatism method was adopted for the focus servo, a four-segment photodetector was used as the cylindrical lens 19 and the detector 21, but when the Foucault prism method was adopted, the cylindrical lens 19
Instead, a Foucault prism is used; when the Naifezi method is employed, a Naifezi and a two-division photodetector are used; furthermore, when a critical angle detection method is employed, a critical angle prism and a two-division photodetector are used.

Similarly, although the push-pull method is used for tracking servo, an appropriate method such as the three-spot method may be used. The focusing control circuit 25 is connected to the focusing coil 13a via an amplifier, and the focusing control circuit 25 outputs a signal corresponding to the amount of displacement in the focusing direction, that is, a focus servo signal, to the focusing single 13a via the amplifier. The track position sensor 31 is connected to the tracking control circuit 47 via the operational amplifier circuit OP, and a signal corresponding to the position in the track direction is given to the tracking control circuit 47 via the operational amplifier circuit OP. This tracking control circuit 27 is connected to the tracking coil 13b via an amplifier, and the tracking control circuit 27 outputs a signal corresponding to the amount of displacement in the track direction, that is, a tracking servo signal, to the tracking coil 13b via the amplifier. As described above, the objective lens 13 is moved in the tracking direction and the focusing direction by flowing currents according to the tracking servo signal and the focus servo signal to the tracking coil 13b and the focusing coil 13a. As a result, the objective lens 13
It is designed to follow according to the side of deviation.

The reproduced signal processing circuit 29 is connected to the track position sensor 31 and also to the pass line BL. Here, the signal output from the track position sensor 31 reflects the unevenness of pits formed on the track of the optical disc 1, and is therefore used as a reproduction signal of data information. The reproduced signal processing circuit 29 outputs this reproduced signal to the pass line BL where it is subjected to binarization processing, modulation/demodulation processing, and the like.

The memory 31 is a CPU 3 that stores various control programs related to writing data information to the optical disc 1, etc.
3 is connected to each of the laser control circuit 15, the focusing control circuit 25, the tracking control circuit 27, the linear motor control circuit, and the motor control circuit 39 via the D/A converter 35 and the pass line BL, and the CPU 33
executes various control processes based on control programs stored in the memory 31. Also, the memory 31. CPU33
and the D/A converter 35 constitute the controller 30.

The linear motor control circuit 37 is connected to a drive coil 41 of the linear motor, and by controlling this linear motor, the fixed portion of the optical head 5 is moved in the radial direction of the optical disc 1. The scale sensor 43 detects the position of the optical head 5 in the tracking direction.

Next, the configuration and operation of the laser control circuit 15 will be explained with reference to FIGS. 2 and 4.

The laser control circuit of this embodiment is roughly divided into a read system and a write system. The read system inputs the semiconductor laser light output monitor signal S1 input from the optical head 5 and the timing signal S3 input from the controller 30 to control the light output of the semiconductor laser 7 to a predetermined constant value. - Consists of a control circuit (APC) 151 and a semiconductor laser drive circuit 153. The write system also includes a pulse generation circuit 155 that outputs a pulse S9 with a constant pulse width based on a recording pulse generation timing signal S5 output from the controller 30, and this pulse generation circuit 1.
A power switching circuit 157 inputs the pulse S9 outputted from the controller 55 and the recording output switching signal S7 outputted from the controller 30, and switches the optical output of the semiconductor laser 7 to a high level only when the switching signal is rHJ. A semiconductor laser drive circuit 159 outputs a current signal S I+ for driving the semiconductor laser 7 according to the control signal of the power switching circuit 157.
Consisted of. This semiconductor laser drive circuit 159
The optical output of the semiconductor laser 7 is increased by the signal, and a deep pit is formed.

Next, the configuration and operation of the reproduced signal processing circuit 29 will be explained with reference to FIGS. 3 and 5.

The reproduced signal processing circuit 29 of this embodiment includes an amplifier circuit 291,
It is composed of a position detection circuit 293 and a peak value detection circuit 295 connected to this amplifier circuit 291. That is, after amplifying the bit signal S13 input from the optical head to a predetermined value, the position detection circuit 293 outputs a position detection signal S15 indicating the position of the pit signal S13 to the controller 30, and also outputs the peak value Detection circuit 29
5, when the peak value of the bit signal S13 exceeds a predetermined value, a peak signal S17 is output to the controller 30.

Therefore, in the controller 30, these position detection signals S
15 and the peak signal S 17, it is possible to obtain two pieces of information: the presence or absence of pits and the depth of the pits, that is, the recording level, thereby achieving high density recording of information.

In this example, the optical output was switched, that is, the energy product, which is the product of the optical output and the pulse width, was changed depending on the pit depth, but the same result could be obtained even if the pulse width was changed in the same way. Obtainable.

Furthermore, as is clear from the diagram showing the relationship between the energy product and the peak value shown in Figure 6, when a recording medium with a wide range of linearity is used, it becomes easier to detect the peak value. It is possible to subdivide the optical output into two or more stages.

[Effects of the Invention] As explained above, according to the present invention, when information is optically recorded on a recording medium, the amount of the light beam can be changed, and the amount of the light beam can be changed depending on whether there is an information unit or not. Since information is added by changing the amount of information, it is possible to significantly increase the recording density of the recording medium, and therefore, even with the same recording medium as before, the recording capacity can be increased. play.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of an optical disk device according to the present invention, FIG. 2 is a block diagram showing the configuration of a laser control circuit, and FIG. 3 is a block diagram showing the configuration of a reproduced signal processing circuit. FIG. 4 is a time chart showing the state of signals in each part of the laser control circuit shown in FIG. 2, FIG. 5 is a time chart showing the state of signals in each part of the reproduced signal processing circuit shown in FIG. 3, and FIG. 7 is a diagram showing the product of optical output and pulse width in comparison with the conventional method, and FIG. 7 is a diagram showing the state of the conventional signal. 1... Optical disk (recording medium) 5... Optical head 7... Semiconductor laser 15... Laser control circuit 29... Playback signal processing circuit

Claims (1)

[Claims] A light emitting source that generates a light beam, an optical means for guiding the light beam generated from the light source to a recording medium, and information recorded on the recording medium by the light beam guided by the optical means. 1. An optical recording/reproducing device comprising a changing stage capable of changing the amount of the light beam for each information unit.