JP2675442B2 - Optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording / reproducing apparatus for recording or reproducing information by irradiating an optical recording medium with a beam.

[0002]

2. Description of the Related Art In recent years, an optical disk for irradiating a light beam such as a laser beam to record or reproduce information has been put into practical use. Functionally classifying such optical disks can be classified into a read-only type, a write-once type capable of recording only once, and a rewritable type capable of repeatedly recording. As a typical one, there is a compact disc in the read-only type,
The rewritable type is a magneto-optical disk.

Recently, a disc having a read-only area (ROM area) and a rewritable area on the same disk (hereinafter referred to as a partial ROM disk) has been proposed. That is, the ROM area by pits is arranged in the inner peripheral area of the disk, and the rewriting area utilizing the magneto-optical effect is arranged in the outer peripheral area, as in the current compact disk.

[0004]

In such a partial ROM disk, since the signal detection method is different in each area, it is necessary to perform various switching according to each area. On the other hand, the address of the branch point of each area is recorded in advance in the lead-in area of the innermost part of the disc, and this address is read from the disc and stored in the RAM prior to reproduction, and the address read during reproduction is A method may be considered in which the playback system is switched immediately before the address is exceeded. However, this method is not a problem when the disc is normally played from the beginning, but when a track jump is performed during high-speed access, if the playback position after the jump is within the playable area, In this case, the area cannot be discriminated because the information cannot be read.

Therefore, the present invention proposes an optical recording / reproducing apparatus capable of always discriminating in which recording area the head is located in such a disc.

[0006]

In view of the above problems, the present invention provides a first area in which a signal is recorded in the first mode and a second area in which a signal is recorded in a mode other than the first mode. An optical recording / reproducing apparatus for an optical recording medium having an area is provided with a detecting means for detecting only the signal of the first form.

[0007]

In view of the above problems, the present invention provides a first area in which a signal is recorded in the first mode and a second area in which a signal is recorded in a mode other than the first mode. In an optical recording / reproducing device for an optical disc in which a region and a region are divided in the radial direction, the reproduction position is set to the first reproduction position based on a signal from a first reading unit for reading the signal of the first form. It is characterized in that it has a detection means for detecting that it is in the area.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows a partial ROM disk according to the embodiment. A read-in area, a ROM area, a recording area, and a lead-out area are arranged in this order from the inner peripheral portion of the disk. In the ROM area, a spiral recording track is formed by a pit row, as in the current compact disc. Information can be recorded in the recording area in the form of magneto-optical recording, and a spiral groove (groove) is formed in advance. Information is perpendicularly magnetically recorded on the groove with the direction of magnetization.

The disc is a reflection type disc. Although the track pitch in each area is almost the same, the track width Wb of each area is larger than the track width Wa of the ROM area.

FIG. 2 shows the structure of the main part of an optical head for reading information from such a disc. The linearly polarized beam emitted from the semiconductor laser 1 is reflected by the diffraction grating 2.
After being divided into beams, the collimator lens 3 forms a parallel beam. Of these beams, the beam that has passed through the beam splitter 4 is converged on the disk D by the objective lens 5. The reflected beam from the disk D travels back in the same optical path, of which the beam splitter 4
The beam reflected by reaches the polarization beam splitter 8 via the half-wave plate 6 and the lens 7.

The half-wave plate 6 has a beam RO
The polarized plane of the reflected beam is polarized so that the reflected beam from the disc D is equally reflected by the polarization beam splitter 8 when the M region is illuminated (that is, the polarized plane does not change depending on the disc). Beam splitter 8
Acts to regulate against. The adjustment is made to read the magneto-optically recorded information in the recording area.

In the recording area, there are two types of magnetization in the direction perpendicular to the disc surface, depending on the recording information, and the polarization planes of the beam from the disc are the same in opposite directions depending on the direction of the magnetization. Rotate by an angle (Kerr effect). When the plane of polarization is rotated in this way, the polarization beam splitter 8
The plane of polarization of the beam incident on is also rotated accordingly, and the amount of light transmitted or reflected by the polarization beam splitter 8 changes accordingly. At this time, the increase amount of one beam light amount becomes equal to the decrease amount of the other beam light amount.
The beams transmitted or reflected by the polarization beam splitter 8 are incident on the first and second optical sensors 11 and 12 via the cylindrical lens 9 and the lens 10, respectively.

The first sensor 11 is composed of a four-division sensor that receives 0th-order diffracted light among the beams split by the diffraction grating 2 and two sensors that receive two first-order diffracted light. A signal (focus error signal) that indicates the defocus of the beam on the disk by processing each output of the 4-division sensor
To form Further, a signal (tracking error signal) indicating a beam track deviation is formed by the difference component of the outputs from the two sensors that receive the first-order diffracted light.

Further, a signal formed by taking the sum of the sensor outputs of the four-division sensor is applied to one input terminal of the amplifiers 13 and 14. The second sensor 12 includes the diffraction grating 2
It is configured by only one sensor that receives only the 0th-order diffracted light among the beams divided by, and the signal from this sensor is applied to the other input terminals of the amplifiers 13 and 14.

Reference numeral 15 is a magnetic coil for applying appropriate magnetization to the beam irradiation portion when information is recorded on the recording track of the recording area.

When the recording track in the ROM area is scanned by the beam while rotating the disk D, the disk D
The intensity of the reflected beam from is changed according to the pits on the track, so that the summing amplifier 13 outputs a frequency signal corresponding to the recorded information. On the other hand, when the recording track of the recording area is scanned, the outputs of the optical sensors 11 and 12 increase / decrease according to the magnetization direction of the recording track. On this occasion,
As for the output of each sensor, the output of one increases and the output of the other decreases due to the principle of the optical system described above, and the fluctuations of each output are equal to each other. Therefore, the output of the amplifier 14 is modulated by the information on the track, and the frequency information corresponding to the information is emitted.

[0017]

As described above, in such an optical system, the amplifier 1 is used when the optical head is scanning the ROM area.
The signal from 3 becomes a read signal, and when the recording area is scanned, the signal from the amplifier 14 becomes a read signal. Therefore, when reproducing such a disc, it is necessary to determine which area the optical head is reproducing and select the signal from either one of the amplifiers as the read signal.

In the recording / reproducing system, the deviation of the beam with respect to the track is detected by the so-called three-beam method. In such a three-beam method, two first-order diffracted lights divided by the diffraction grating 2 are applied to different edges of a track, and a tracking error signal is created by a difference in intensity of a reflected beam from a disk. When the 0th-order diffracted light that is the read beam is correctly positioned on the track. The two first-order diffracted lights are equally applied to the respective edges. However, if the 0th-order diffracted light shifts in the direction crossing the track,
Of the two first-order diffracted lights, one is applied to the track more and the other is applied to the track correspondingly less. If there is a difference between the reflectance of the track and the reflectance of the area between the tracks, there will be a difference in the amount of light reflected from the disc of these two first-order diffracted lights. The tracking error signal is created by detecting this difference. In the case of the present embodiment, the difference in the reflected light amount of the first-order diffracted light is detected by the output difference between the two sensors for receiving the first-order diffracted light arranged on the first sensor 11.

However, in the case of the disc shown in FIG.
In the area, the reflectance of the recording track is lower than the reflectance of the inter-track area, but conversely, in the recording area, the reflectance of the recording track is higher than the reflectance of the inter-track area. This is based on the structure of the recording track and the inter-track area. If the track width is small,
The bottom of the track is close to a curved surface. On the contrary, when the width of the track is wide, the bottom of the track becomes flat. Such a characteristic similarly occurs in the inter-track area. In the case of the disc of FIG. 3, since the track width is narrow in the ROM area,
Since the bottom of the track is curved and the beam is diffusely reflected by this, the apparent reflectance of the track is small. On the contrary, in the recording area, since the width between the tracks is narrow, the surface between the tracks becomes a curved surface, and the beam is diffusely reflected by this, so that the apparent reflectance between the tracks becomes small.

Therefore, when the tracking error signal is created by the three-beam method as in the present embodiment, even if the beam is deviated in the same direction with respect to the track, the created tracking error signal remains in the ROM area. Since the polarities are reversed in the recording area, it is necessary to invert the polarities of the tracking error signals in one of the areas to match the polarities of the tracking error signals. Therefore, in the recording / reproducing system shown in FIG. 2, it is necessary to control the switching of the read signal and the switching of the polarity of the tracking error signal in accordance with the determination of which region is being reproduced. is there.

FIG. 1 shows the configuration of a processing device for processing a signal read by the optical head. In the figure, 1
00 is the above-mentioned optical head, 200 is a head amplifier, 3
00 and 400 are a ROM signal reproducing circuit for reproducing a ROM signal and a magneto-optical signal reproducing circuit for reproducing a magneto-optical signal, 5
00 is a discriminating circuit for discriminating whether the optical head is scanning the ROM area or the recording area, and 600 is a signal from the ROM signal reproducing circuit 300 and the magneto-optical signal reproducing circuit 4
A switching circuit that receives signals from the optical head 00 and selects one of the signals as a reproduction signal in accordance with the signal from the discriminating circuit 500. Reference numeral 700 denotes an optical head from the optical head according to the focus deviation and tracking deviation of the beam with respect to the track. It is a control circuit that issues a signal for controlling the position of the beam spot.

The discrimination circuit 500 includes a high pass filter 50.
1, rectifying circuit 502, integrating circuit 503 and comparing circuit 50
Consists of four. A signal obtained by amplifying the output signal (ROM signal) from the amplifier 13 of FIG. 2 by the head amplifier 200 is applied to the high-pass filter 501. As described above, when the optical head scans the ROM area, the signal becomes a high frequency signal corresponding to the recording information. On the other hand, when scanning the recording area, the signal has a low frequency corresponding to the tracking error signal. The high-pass filter 501 is set to pass only the former of these two signals. Therefore, in the rectifier circuit 502,
The high frequency signal is transmitted only when the optical head is scanning the ROM area.

The rectifying circuit 502 and the integrating circuit 503 convert the signal into a DC level signal. The comparator circuit 504 outputs a determination signal when detecting that this signal exceeds the set value level Vc. When the switching circuit 600 outputs the determination signal, the switching circuit 600 outputs R
The signal from the OM signal reproducing circuit 300 is selected, and when the discrimination signal is not output, the signal from the magneto-optical signal reproducing circuit is selected. Further, the control circuit 700 inverts the polarity of the tracking error signal depending on the presence / absence of the determination signal.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments.
Needless to say, various other restrictions are possible.
For example, in the above embodiment, the reproduced area is determined according to the signal from the amplifier 13, but instead of this,
The area may be discriminated according to the signal from the amplifier 14. In the present embodiment, assuming that the beam is scanning the track correctly, if the photoelectric conversion rates of the optical sensors 11 and 12 are the same, and if the optical head is reproducing the ROM area, each sensor The outputs from are canceled out and become 0. In this case, the amplifier 14 outputs a low-frequency signal corresponding to the tracking error. Therefore, the signal from the amplifier 14 applied to the discrimination circuit 50
If it is applied to the same circuit as 0, from this discrimination circuit,
The discrimination signal is output while the optical head is scanning the recording area. Using such a signal, the switching circuit 600
Also, the control circuit 700 is controlled. However, in this case, it should be noted that the generation of the discrimination signal occurs when the optical head scans the recording area, unlike the above embodiment.

[0026]

As described above, according to the present invention, a light having a first area in which a signal is recorded in the first mode and a second area in which a signal is recorded in a mode other than the first mode is provided. When reproducing the recording medium, it is possible to determine which area is being reproduced, so that the medium can be reproduced favorably and smoothly.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an embodiment.

FIG. 2 is a diagram showing a configuration of an optical head of an example.

FIG. 3 is a diagram showing a configuration of a disc of an example.

[Explanation of symbols]

 100 optical head 500 discrimination circuit (detection means)

Claims (1)

(57) [Claims] 1. A first area in which a signal is recorded in the first mode and a second area in which a signal is recorded in a mode other than the first mode.
In the optical recording / reproducing apparatus in the optical disc in which the area of 1) and the area of 1 are radially divided, the reproduction position is set to the first position based on the signal from the first reading unit for reading the signal of the first form. An optical recording / reproducing apparatus having a detecting means for detecting that the optical recording / reproducing apparatus is in the area.