JP3066133B2 - Method of reproducing information from optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reproducing information from an optical recording medium such as a read-only optical disk, a write-once optical disk, a rewritable optical disk, a magneto-optical disk, an optical tape, an optical card and an optical floppy disk.

[0002]

2. Description of the Related Art Conventionally, an information reproducing method for an optical recording medium is performed by irradiating an optical recording medium such as an optical disk with a condensed laser beam as reproducing light and relatively scanning the reproducing light and the optical recording medium. The reflected light or transmitted light is photoelectrically converted by a light receiver to reproduce information recorded on the optical recording medium.

In such an information reproducing method for an optical recording medium, it is necessary to set the power of the condensed laser beam so that the optical recording medium such as an optical disk is not damaged.
In order to obtain a good reproduction signal from the photodetector, it is better to increase the power of the focused laser beam.

Therefore, while scanning the optical disk, the optical disk is irradiated with a focused laser beam to form a light spot, and the reflected light is photoelectrically converted by a photodetector to reproduce the information recorded on the optical recording medium. Japanese Patent Application Laid-Open No. Sho 62-17 discloses a method of reproducing information from an optical recording medium in which the irradiation light amount of the focused laser beam is set in two or more steps.
No. 2536.

[0005] Also, in "Transimpedance switching type preamplifier IC", Ishihara, Goto, Mabuchi, Kobayashi, IEICE Spring National Convention C-366, in 1991, an input at the time of recording at a light receiving unit in a magneto-optical disk device. Since the light and the input light at the time of reproduction are largely different, a preamplifier IC for a light receiving unit is described which can switch the transimpedance at the time of recording and at the time of reproduction.

[0006]

In the above information reproducing method for an optical recording medium, the irradiation light amount of the condensed laser beam is set in two or more steps. The level of the reproduction signal has changed, and a problem has occurred in the detection of the reproduction signal (in the detection of the recorded information). In addition, when a light spot on an optical disk is scanned at a high speed, in order to obtain a good S / N reproduction signal, it is necessary to not only increase the irradiation light amount of the condensed laser beam but also to detect the reproduction signal at a high frequency. However, there was no effect of improving the S / N of the reproduced signal with respect to the detection of the reproduced signal having a fast response.

The preamplifier IC for the light receiving section in the above-mentioned magneto-optical disk device is for reducing the level fluctuation of the output signal at the time of recording and at the time of reproduction, and is not intended to improve the reproduction signal detection capability at the time of reproduction. Absent.

The present invention solves the above-mentioned drawbacks, and the S / N of the reproduced signal is always optimized in accordance with the relative scanning speed between the reproduced light and the optical recording medium without damaging the optical recording medium by the reproduced light. It is an object of the present invention to provide an information reproducing method for an optical recording medium which can be set as described above.

[0009]

According to a first aspect of the present invention, an optical recording medium is irradiated with reproduction light to relatively scan the reproduction light with the optical recording medium. A method of reproducing information recorded on the optical recording medium by photoelectrically converting the reflected light or transmitted light with a light receiver and amplifying the reflected light or transmitted light with a preamplifier, As the scanning speed of the optical recording medium increases, the power of the reproduction light increases, and at the same time, the feedback resistance of the preamplifier decreases in inverse proportion to the power of the reproduction light, thereby increasing the frequency band of the preamplifier. band
Extend to the area. According to a second aspect of the present invention, in the information reproducing method for an optical recording medium according to the first aspect, the inner peripheral portion and the outer peripheral portion are described.
Optical record recorded so that the size of the recording mark is almost the same
Using a recording medium, the reproduction light and the optical recording medium are relatively scanned by rotating the optical recording medium at a constant rotation speed, and the power of the reproduction light is changed from the inner peripheral portion of the optical recording medium. Is also increased at the outer periphery.

[0010]

FIG. 2 shows an example of an optical disk apparatus to which the present invention is applied. An optical recording medium 1 such as an optical disk is rotationally driven by a spindle motor 2 in a direction of an arrow 3 at a constant rotation speed. At the time of reproduction for reproducing information recorded on the optical disk 1, light from the semiconductor laser 4 passes through the beam splitter 5 and is irradiated by the condenser lens 6 so as to be focused on the recording surface of the optical recording medium 1. A light spot is formed. The optical recording medium 1 has marks (for example, depressions in the reflection film, holes in the reflection film, changes in reflectivity on the reflection film, magneto-optical marks, etc.) recorded on the recording surface as information.
The reflected light (or transmitted light) is reflected by the beam splitter 5 through the condenser lens 6 and is incident on a light receiver 9 such as a photodiode as indicated by an arrow 8, and the amount of incident light is converted into an electric signal 10. You. The semiconductor laser 4 is driven by a semiconductor laser drive circuit 11, and the light output is controlled.

The optical disk 1 uses a magneto-optical recording film such as a metal, semimetal, alloy, organic dye, chalcogen glass, TbFeCo, or the like as a recording film, and may be any of a read-only type, a write-once type, and a rewritable type. Used to reproduce recorded information. This optical disk device requires a well-known focus control mechanism and tracking control mechanism having an optical element for performing focus control and tracking control of the reproduction light (condensed laser light) 7, a light receiving element, a servo control actuator, and the like. Can be used accordingly.

For example, when the optical disk 1 is rotationally driven by the spindle motor 2 at a constant rotation speed, the recording surface of the optical disk 1 is scanned in the circumferential direction by the light spot by the reproduction light 7, but the scanning speed is The light spot by the reproduction light 7 goes faster toward the outer periphery of the optical disk 1 and is proportional to the distance between the rotation center of the optical disk 1 and the light spot by the reproduction light 7. As the power of the reproduction light 7 increases, the power of the reflected light from the optical disk 1 also increases, and the reproduction signal 10 from the light receiver 9 also increases, and the S / N is improved.
When the power of the reproduction light (condensed laser light) 7 is increased, the temperature of the recording surface of the optical disk 1 rises. If the temperature exceeds a certain limit, the recording surface of the optical disk 1 is burned and damaged. Further, the temperature rise of the recording surface of the optical disk 1 decreases as the scanning speed of the reproduction light 7 increases, and the maximum value Pr of the power of the reproduction light 7 that does not damage the recording surface of the optical disk 1 is higher than the recording surface of the optical disk 1. It is proportional to the 0.5V to 1st power of the scanning speed v relative to the reproduction light 7. Therefore, the scanning speed of the reproduction light 7 on the optical recording medium 1 is increased so that the power of the reproduction light 7 becomes the maximum value Pr from the inner circumference to the outer circumference of the optical disk 1 by controlling the semiconductor laser drive circuit 11 by the controller 20 described later. By increasing the power of the reproduction light 7 as much as possible, the S / N of the reproduction signal 10 over the entire surface of the optical disc 1 is kept high.

Another means is used to increase the S / N of the reproduced signal 10, and as shown in FIG. 1, a preamplifier 2 comprising an operational amplifier 25 and feedback resistors R1 to R5.
6 is larger than the conventional one by the switch circuit 21 based on the transimpedance instruction signal 24 from the controller 20 (the feedback resistance value over the entire surface of the optical disc 1).
And the transimpedance is made larger than before (over the entire surface of the optical disc 1).
Over the past) . As a result, the output voltage of the preamplifier 26 becomes (from the beam splitter 5 to the light receiver 9).
8) × (transimpedance of the preamplifier 26), so that even if the photocurrent of the light receiver 9 is small ,
As the lance impedance increases, the output voltage of the preamplifier 26 increases and its S / N increases. Here, a reverse bias voltage Vb is applied to the light receiver 9.

However, the S / N of the reproduced signal 10 is increased.
That before just size <br/> comb conventionally a feedback resistance value of the preamplifier 26 to a transimpedance preamplifier 26 prior
Even if it is larger, the transimpedance of the preamplifier 26 in the high frequency range is lower than that of the conventional transformer as shown in FIG.
Than the frequency band of the preamplifier with small impedance
Also, the frequency band of the preamplifier 26 becomes narrower at the high frequency side where the frequency is higher, so that the capability of detecting the reproduced signal at the higher frequency component is reduced. On the other hand, since the mark recorded on the outer peripheral portion and the mark recorded on the inner peripheral portion of the optical disc 1 are almost the same size as the reproduction light 7, the frequency of the reproduced signal is compared with that of the inner peripheral portion of the optical disc 1. In order to reproduce the reproduction signal faithfully, the optical disc 1
The higher the outer circumference, the higher the bandwidth required for the output signal 22 of the preamplifier 26. In response to this request, in this optical disk device, the power of the reproduction light 7 is increased toward the outer periphery of the optical disk 1 by the control of the semiconductor laser drive circuit 11 and the switch circuit 21 by the controller 20, and at the same time, the output of the preamplifier 26 The level of the signal 22 is kept constant with respect to the change in the power of the reproduction light 7 with respect to the inner and outer peripheral portions , that is, the S / N of the reproduced signal 10 increases.
As described above, the feedback resistance value of the preamplifier 26 is
The transimpedance of the preamplifier 26 is
Output signal of the preamplifier 26
Level 2 (as described above (from the beam splitter 5 to the
9 detection light 8) × (transimpedance of preamplifier 26)
-Dance)) is kept constant as described above so that
The power of the raw light 7 increases toward the outer periphery (the detection light 8
The feedback resistance of the preamplifier 26
The value decreases in inverse proportion to the power of the reproduction light and the preamplifier 2
6 transimpedance is inversely proportional to the power of the reproduction light
As shown in FIG. 3, the transimpedance 31 for information reproduction on the outer periphery of the optical disc 1 is kept constant over a wide frequency range as compared with the transimpedance 30 for signal reproduction on the inner periphery of the optical disc 1 as shown in FIG. Therefore, signal reproduction in a high band becomes possible, and the maximum S / N can be obtained in a necessary and sufficient band for each position from the inner peripheral portion to the outer peripheral portion of the optical disc 1.

As shown in FIG . 4 , the controller 20 detects the position of the light spot on the optical disk 1 by the reproduction light 7 by the track address indicating the track on which the reproduction light 7 is irradiated, and reproduces the optical disk 1 at the detected position. The relative scanning speed of the light 7 is calculated. Then, the controller 20 calculates the power of the reproduction light 7 having a predetermined value as described above based on the scanning speed, transmits a reproduction laser power instruction signal 23 corresponding to the calculated value to the semiconductor laser drive circuit 11, and By controlling the drive current of the laser 11, the power of the reproduction light 7 is set to the predetermined value as described above.
At the same time, the controller 20 calculates the transimpedance of the preamplifier 26 from the power of the reproduction light 7 according to the relationship (transimpedance of the preamplifier 26) ∝1 / (power of the reproduction light 7), and according to the calculated value. The transimpedance instruction signal 24 is transmitted to the switch circuit 21, and the switch circuit 21 selectively connects the feedback resistors R 1 to R 5 to the operational amplifier 25 in accordance with the transimpedance instruction signal 24, and sets the feedback resistance value of the preamplifier 26. Are set so that the transimpedance of the preamplifier 26 changes as described above in inverse proportion to the power of the reproduction light 7.

According to the optical disk apparatus, the power of the reproduction light 7 is set to the maximum value P from the inner circumference to the outer circumference of the optical disk 1.
As the scanning speed of the reproduction light 7 with respect to the optical recording medium 1 increases so as to be r, the power of the reproduction light 7 is increased so that the S / N of the reproduction signal 10 over the entire surface of the optical disk 1 is kept high, The feedback resistance value of the amplifier 26 is set to a transimpedance instruction signal 24 from the controller 20.
, The transimpedance is selected by the switch circuit 21 so as to be larger than the conventional one , and the output signal of the preamplifier 26 is increased as described above.
22 is the level of the reproduction light 7 with respect to the inner and outer peripheral portions.
Preamplifier so that it remains constant with power changes
26 is reduced in inverse proportion to the power of the reproduction light.
The transimpedance of the preamplifier 26
, The maximum reproduction signal is always obtained according to the scanning speed of the reproduction light 7 on the optical recording medium 1, and the detection band of the preamplifier 26 is secured in proportion to the scanning speed. . For this reason, the maximum reproduction signal can always be obtained with a good S / N in a necessary and sufficient band.
This is effective in increasing the storage capacity of the device. In particular, in the future, the effectiveness will be increased under the condition that the sensitivity of the light receiver 9 is reduced by using a laser beam having a short wavelength (700 nm to 400 nm).

The present invention is not limited to the example in which the optical recording medium 1 rotates at a constant rotational speed as described above, but is also applicable to a variable rotational speed type in which the rotational speed of the optical recording medium changes. And the setting is made such that the scanning speed of the reproduction light with respect to the optical recording medium and the feedback resistance of the preamplifier 26 are in inverse proportion. The output signal of the plurality of preamplifiers 26 may be used not only for reproducing information but also for detecting a focusing signal and a tracking signal.

[0018]

As described above, according to the first aspect of the present invention,
Since the power of the reproducing light increases as the scanning speed of the reproducing light with respect to the optical recording medium increases, the feedback resistance of the preamplifier decreases in inverse proportion to the power of the reproducing light.
S of the reproduced signal without damage to the optical recording medium by the reproduction light
/ N can always be set to be optimal in accordance with the relative scanning speed between the reproduction light and the optical recording medium.

According to the invention of claim 2, according to claim 1,
In the information reproducing method for an optical recording medium described in the above, the reproducing light and the optical recording medium are relatively scanned by rotating the optical recording medium at a constant rotational speed, and the power of the reproducing light is recorded in the optical recording medium. Since it is increased at the outer periphery rather than the inner periphery of the medium, the S / N of the reproduction signal is always optimized according to the relative scanning speed between the reproduction light and the optical recording medium without being damaged by the reproduction light of the optical recording medium. It can be set to be.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a reproducing system in an example of an optical disk device to which the present invention is applied.

FIG. 2 is a schematic diagram showing an optical system of the optical disc device.

FIG. 3 is a characteristic curve diagram for explaining the optical disc device.

FIG. 4 is a flowchart showing a part of a processing flow of a controller in the optical disc device.

[Explanation of symbols]

4 the semiconductor laser 9 photoreceiver 11 semiconductor laser driving circuit 20 the controller 21 the switching circuit 26 preamplifier R ₁ to R ₅ feedback resistor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B ^7/ 00-7/013 G11B 7/125

Claims (2)

(57) [Claims] 1. An optical recording medium is irradiated with reproduction light to relatively scan the reproduction light and the optical recording medium, and the reflected light or transmitted light is photoelectrically converted by a light receiver and is subjected to a preamplifier. In the information reproducing method for an optical recording medium for reproducing information recorded on the optical recording medium by amplifying, the power of the reproducing light increases as the scanning speed of the reproducing light with respect to the optical recording medium increases. At the same time, the feedback resistance of the preamplifier is reduced in inverse proportion to the power of the reproduction light, and the frequency band of the preamplifier is extended to a high band.
Information reproducing method for an optical recording medium, characterized in that that. 2. The information reproducing method for an optical recording medium according to claim 1, wherein the size of the recording mark is the same between the inner peripheral portion and the outer peripheral portion.
Using an optical recording medium recorded to a degree, the optical recording medium is rotated at a constant rotation number to relatively scan the reproduction light and the optical recording medium, and the power of the reproduction light is reduced. An information reproducing method for an optical recording medium, wherein the number is increased at an outer peripheral portion of the optical recording medium than at an inner peripheral portion.