JP2003257041A - Optical information reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To arrange so as to obtain a reproduced signal with satisfied S/N even though a flexible optical disk is used wherein a reflective film or a protective film is not being formed. <P>SOLUTION: In a reproducing device for obtaining the reproduced signal in accordance with a reproduced light beam Lb from the optical disk 1 by using the flexible sheet-like optical disk 1 having the exposed signal recording surface 1a whereon data to be recorded are being recorded on one side as a projected/recessed or snaky groove, to irradiate this optical disk 1 with a light beam Lb, a reproduction power of a semiconductor laser emitting the light beam La is increased till the focusing is stably performed by the light beam La for the purpose of increasing the light quantity of the reproduced light beam Lb. At this time, the reproduction power is increased till the noise of the reproduced signal of the optical disk 1 controls the noise of the whole device, which is not for the noise of the whole device (electric system noise). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a flexible optical disk having an exposed signal recording surface on one side of which recording data is recorded as uneven or meandering grooves. The present invention relates to an optical information reproducing apparatus that emits a beam and detects an optical change in a reproduction light beam from a flexible optical disk to obtain a reproduction signal.

[0002]

2. Description of the Related Art Conventionally, C has been used as a read-only optical recording medium.
There are D and DVD. These have a structure in which concavities and convexities corresponding to a recording signal are formed on a disk substrate made of a transparent resin, a reflective film of Al or the like is formed immediately above this, and a protective film of an ultraviolet curable resin is further formed.

At the time of reproduction, laser light focused to the diffraction limit is applied to the irregularities through the disk substrate.
Then, phase interference occurs according to the unevenness, and the reflectance changes according to the unevenness, and the reflected light is received by the photoelectric conversion element to reproduce the signal.

[0004] The applicant of the present invention is the Japanese Patent Application No. 2001-22.
No. 8943 was filed for a recording / reproducing apparatus having a stabilizing member for stabilizing the surface wobbling of a flexible optical disk when it is rotationally driven by the pressure difference of the airflow using Bernoulli's law.

[0005]

By the way, in the above-mentioned optical disk, it is the unevenness on the disk substrate that has the signal component, not the reflective film. However, all the conventional reproducing optical discs have a metal reflection film such as Al formed thereon. Due to the presence of this metal reflection film, the reflectance of the disk was high and the processing of the reproduced signal was easy.

Ordinary CDs, DVDs and the like have a recording surface on the back side of the disk substrate with respect to the side on which laser light is incident.
Therefore, the laser light enters inside from the surface of the disk substrate, then reaches the recording surface, and is reflected as a reproduction light beam. However, the laser light is also reflected on the surface of the disk substrate, although it is as low as several%.

Therefore, it is necessary to prevent the reflection on the surface of the disk substrate from adversely affecting the reproduction signal by the reproduction light beam by forming a reflection film having a high reflectance such as Al on the recording surface.

Therefore, conventionally, a vacuum process is required for forming a reflective film in manufacturing a disk. However, vacuum processes are expensive. Therefore, it is cost effective to eliminate the formation of the reflection film or the protection film and the manufacturing process thereof in the optical disc.

The above-mentioned Japanese Patent Application 2001-filed by the applicant
In the flexible optical disk used in the recording / reproducing apparatus according to the invention of No. 228943, it is possible to eliminate the reflection film or the protective film in the same manner. However, in this case, the light amount of the reproduction light beam from the optical disk is increased. However, there was a problem that a good reproduction signal could not be obtained.

An object of the present invention is to solve the above-mentioned problems and to reproduce an optical information having a structure in which a reproduced signal having a good S / N can be obtained even when a flexible optical disk having no reflective film or protective film is used. To provide a device.

[0011]

In order to achieve the above object, the invention according to claim 1 is flexible in that a signal recording surface on which recording data is recorded as an uneven or meandering groove is exposed on one side. An optical information reproducing apparatus which obtains a reproduction signal by irradiating a flexible optical disk with a light beam and detecting an optical change in the reproduction light beam from the flexible optical disk, using an optical disk, The emission power of the light beam is set so that the signal level of noise in the reproduction signal is higher than the signal level of electrical system noise in the entire apparatus. Since there is no special formation film, the reproduction light beam receives only the interference from the signal recording surface, and S as a reproduction signal is
/ N improves. Since the amount of light in the reproduction light beam is reduced due to the configuration of the flexible optical disk, the signal level of the reproduction signal is lowered and it is easy to be affected by the electric system noise in the entire device, so that it is not affected by the electric system noise in the entire device. By increasing the amount of light in the reproduction light beam, a reproduction signal with good S / N can be obtained.

According to a second aspect of the present invention, in the optical information reproducing apparatus according to the first aspect, the amplification gain for the reproduction signal is increased, and with this configuration, the light amount of the reproduction light beam is increased as described above. By increasing the gain and the gain of the amplifier that amplifies the reproduction signal, S
A reproduced signal with a good / N is obtained.

According to a third aspect of the present invention, in the optical information reproducing apparatus according to the first aspect, there is provided a stabilizing member for stabilizing the surface wobbling of the flexible optical disc during rotational driving by the pressure difference of the air flow. , The flexible optical disk is installed on the side opposite to the signal recording surface, and the light reflectance on the surface of the stabilizing member is lowered. With this configuration, the reproduction light beam by the stabilizing member is installed. It is possible to minimize the optical influence on the.

The invention according to claim 4 is the invention according to claim 1 or 3.
In the optical information reproducing apparatus described in the above, as a material of the flexible optical disk, a material excellent in light absorption for a light beam is used, and with this configuration, both sides of the flexible disk interfering with the reproduction light beam. It is possible to suppress the occurrence of light reflection in.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a basic configuration diagram of an optical disk reproducing apparatus for explaining an embodiment of the present invention, in which 1 is a flexible sheet-shaped optical disk and 2 is a spindle shaft for holding a hub 3 of the optical disk 1. Reference numeral 4 denotes a spindle motor that drives the spindle shaft 2 to rotate, and reference numeral 6 denotes an optical disk 1 which irradiates the optical beam 1 with a light beam La.
The optical pickup as a reproducing means for reading the written information based on the reproduced light beam Lb reflected from the optical pickup 7, 7 is an objective lens provided in the optical pickup 6, 8
Is a stabilizing member that is installed to face the optical pickup 6 via the optical disc 1 and prevents surface wobbling of the optical disc 1.

In FIG. 1, a flexible optical disk 1 is set on a spindle shaft 2 at the time of reproduction and is rotationally driven by a spindle motor 4 to rotate between an optical pickup 6 and a stabilizing member 8. The rotating optical disk 1 itself has a small amount of rigidity, and has a force that, when rotated, tends to be in a straight state by the action of centrifugal force. Therefore, by bringing the stabilizing member 8 closer to the optical disc 1 and generating a repulsive force due to the pressure difference of the air flow based on Bernoulli's law and giving the repulsive force to the optical disc 1, a force that makes the optical disc 1 straighten, By the balance of the repulsive force from the stabilizing member 8,
Large surface runout can be reduced.

Then, in the optical disc 1, the light beam La is applied to the portion where the surface wobbling is stable as described above, and the written information is read based on the reproduction light beam Lb reflected from the optical disc 1. .

FIG. 2 is an explanatory view of the reproducing means constituting the optical pickup, which comprises a photoelectric conversion element 10 including a photodiode and a reproduction signal processing circuit 11, and the like.
With respect to the recording bit formed on the recording surface of the optical disc 1, a light beam La of low emission energy is emitted from a laser light source 12 formed of a semiconductor laser or the like, and its reflected light (reproduction light beam) Lb is passed through an objective lens 7. Through the photoelectric conversion element 10, the light is received and the output from the photoelectric conversion element 10 is subjected to signal expansion processing or the like by the reproduction signal processing circuit 11 to generate a reproduction signal.

FIG. 3 is an enlarged explanatory view of this embodiment shown in FIG. 1. In this embodiment, the optical disk 1 is formed by molding a polycarbonate resin to form concave and convex pits as the signal recording surface 1a on the lower surface. No reflection film, UV-curable resin protective film, or the like is provided on the signal recording surface 1a. Therefore, the uneven pits on the signal recording surface 1a are exposed and the surface is in contact with the atmosphere. The light beam La emitted from the optical pickup 6 is focused on this portion as a light spot.

When there is a reflective film, the reflectance is highest in the vicinity of the concave and convex pits and is several tens% or more. Therefore, focusing of the light spot is simple, but in the case of this example, the pit interface on the signal recording surface 1a has a low reflectance of 5% to 6%. Further, since the reflectance of the signal recording surface 1a and the reflectance of the back surface 1b of the optical disk 1 opposite to the signal recording surface 1a are almost the same, the back surface 1b
If the reflected light from is large, S / in the reproduction light beam Lb
N gets worse. Therefore, it is necessary to devise to reduce the influence of the reflected light from the back surface 1b of the optical disc 1.

A stabilizing member 8 is installed near the back surface 1b of the optical disc 1. Since the distance between the stabilizing member 8 and the optical disk 1 is several μm or less, the stabilizing member 8
The reflected light on the surface of is also a noise component for signal reproduction.

As shown in FIG. 3, in order to prevent erroneous focusing on the surface of the stabilizing member 8, the stroke of the objective lens 7 of the optical pickup 6 in the focusing direction is set to 20.
μm. The thickness t of the optical disc 1 is 70 μm in this example.
Is. Here, the maximum strokeable distance value for the focusing operation of the objective lens 7 is d, the distance between the objective lens 7 and the stabilizing member 8 is L, and the working distance of the objective lens 7 is WD.
And The range in which the focus servo error signal can be generated is shown as p.

The flexible optical disk 1 wobbles, but the signal recording surface 1a is farthest from the objective lens 7 when the back surface 1b of the optical disk 1 comes into contact with the stabilizing member 8. This is the state shown in FIG. At this time, the objective lens 7 comes closest to the stabilizing member 8. In this state, the light beam La may not be focused on the surface of the stabilizing member 8. In this case, since the back surface 1b of the optical disk 1 is in contact with the front surface of the stabilizing member 8, the back surface 1b of the optical disk 1 is not focused.

This relationship is expressed by the equation (Equation 1).

[0026]

WD + d / 2 + p <L When the objective lens 7 is closest to the stabilizing member 8, L
= WD-d / 2 + t.

Therefore, the relationship shown in (Equation 2) is established.

[0028]

## EQU00002 ## d + p <t Now, the optical disc 1 stabilized by the action of the stabilizing member 8.
Since the surface deviation is 10 μm or less, the stroke in the focus direction of the objective lens 7 of the optical pickup 6 can be set to 20 μm. Therefore, d = 20 μm
And The focus servo error signal can be generated in a depth range of about 20 μm. Therefore, p
= 20 μm. Here, the thickness t of the optical disc 1 is 70
μm.

Then, (Equation 2) becomes (20 + 20) <7
It becomes 0 and is materialized.

Therefore, stable focusing can be performed on the signal recording surface 1a of the optical disc 1 having a low reflectance. In addition, the surface of the stabilizing member 8 and the optical disk 1
Since the converging point of the light beam La of the optical pickup 1 does not reach any of the back surface 1b of the optical pickup 1, the reproduction light beam Lb can be stably focused on the signal recording surface 1a, as described in FIG. In addition, the S / N of the reproduction signal detected from the reproduction light beam Lb can be kept good.

A known D is recorded on the signal recording surface 1a of the optical disc 1.
A recording pit similar to that of a VD-ROM is formed, and the wavelength of the light beam La emitted from the semiconductor laser 12 is 660n.
FIG. 4 is a waveform diagram obtained by reproducing a signal using the optical pickup 6 having the objective lens 7 of m and NA of 0.65.

DVD for the pits on the optical disk 1
But the pit depth is different. In the light reflection type reproducing method, the degree of modulation of the reproduced signal becomes maximum when the phase difference between the pit portion and the mirror surface portion is λ / 4. In a normal DVD, the disc substrate has a refractive index of 1.
Since there are about 5, it is about 1 at 650 nm / (4 × 1.5)
A pit depth of 10 nm is optimal, but in the present embodiment, the phase difference in air becomes a problem, so 650 n
The pit depth was 160 nm at m / 4, the pits had a shortest length of 0.4 μm, and the track pitch was 0.74 μm. The reproducing linear velocity was 3.5 m / s, and the reproducing power of the semiconductor laser 12 was 2 mW. Also, the reproduction signal processing circuit 11
The gain of the RF amplifier for signal amplification in the above was also increased by about twice. The reproducing power of the semiconductor laser 12 at this time is
This is more than five times as much as when reproducing an ordinary DVD with a reflective film.

As can be seen from FIG. 4, a good eye pattern is obtained. The degree of modulation is 60% or more. The jitter of the clock and the signal was 8.5% which could be reproduced without error. The reflected potential of the signal is about 300 mV.

As a comparative example, FIG. 5 shows a substrate of the same optical disk as that of the present embodiment, on which an Ag reflective film is formed by sputtering.
The reproduction signal of a disk having a film thickness of 0 nm is shown. Since the reflectance is high, the reproducing power of the semiconductor laser 12 is reduced to 0.3 mW. The jitter at this time was 8.0%.
The reflected potential is about 900 mV.

As in the present embodiment, the reproduction power of the semiconductor laser 12 is increased to increase the absolute light amount of the light beam La, and the RF of the reproduction signal processing circuit 11 is applied to the reproduction signal.
By correcting the gain with the amplifier, the S / N ratio of the signal could be largely taken in as in the conventional case.

It can be seen that the degree of modulation is not related to the presence or absence of the reflective film because it is caused by phase interference. Therefore, by increasing the absolute light quantity of the light beam, the flexible optical disk can be reproduced as a reflective read-only disk without forming a reflective film.

In the present embodiment, the reproduction light beam Lb has the minimum condition that the reproduction power of the semiconductor laser 12 is increased until the focusing can be stably performed. However, the reproduction light beam Lb causes noise (electric system noise) in the entire apparatus. Instead, the reproduction power is increased until the noise of the reproduction signal of the optical disk 1 dominates the noise of the entire device. By doing so, all the essential S / N of the disk are used up. This state is shown in FIGS. 6 (a) and 6 (b).

FIG. 6A shows a state where the reproducing power of the semiconductor laser 12 is small. A curve having a sharp peak shows the inherent signal level and noise of the optical disc 1. A curve without a broad peak shown by a dotted line shows noise of the entire device. If the playback power is small,
Since the noise of the entire device is larger than the signal noise of the disc, the overall S / N is determined by the signal peak of the optical disc 1 and the noise of the entire device.

A photoelectric conversion element 10 for receiving the reproduction light beam Lb and photoelectrically converting it, or R of the reproduction signal processing circuit 11.
The noise of the F amplifier has little relation to the amount of received light, whereas the electric signal due to the amount of reflected light from the optical disc 1 increases in proportion to the amount of received light. Therefore, when the reproduction light beam Lb is increased, the noise of the disk exceeds the noise of the electric system at a certain point, and the S / N of the entire apparatus becomes dominated by the optical disk 1. This is shown in FIG. 6 (b). The S / N is better as shown in FIG.
Is obviously good.

In the present embodiment, the reproducing power of the semiconductor laser is raised up to the state shown in FIG. 6 (b). As a result,
A disk drive device capable of excellent reproduction was realized by omitting an expensive vacuum process and using a reproduction-only optical disk manufactured only by resin molding.

At the time of the basic design of the reproducing apparatus, such noise and the frequency spectrum of the signal are analyzed. Actually, the difference between FIG. 6A and FIG. 6B is the reproduction of the semiconductor laser 12. It is just the size of the power. Therefore, at the time of basic design, the noise characteristics of the reproducing apparatus are measured using a spectrum analyzer, then the non-reflective ROM disk is reproduced, and the change in the noise level is observed while changing the reproduction power of the semiconductor laser 12. The S / N becomes saturated as the reproduction power increases. The saturated point is shown in FIG. The reproduction power is set as the reproduction power for the ROM disk in the reproduction device.

Further, in an actual product, the initial value of the reproduction power is set based on the above-mentioned data obtained during the basic design. Then, in order to absorb variations in individual differences of the reproducing apparatus or the disc, it is preferable to install a circuit for finely adjusting the reproducing power while observing the error rate, if necessary.

The flexible optical disk 1 used in the present embodiment does not have a reflective layer or a protective layer formed on the surface thereof, so that it may be put in a cartridge as shown in FIG. 7 for protection. That is, the optical disc 1 has the same structure as that described above, and the optical disc 1 is housed in the cartridge case 20.
The optical disc 1 is exposed to the outside through an opening 20a which is opened and closed by a shutter plate 21 which is slidably provided. Therefore, the human hand does not touch the signal recording surface 1a.

Further, in order to prevent dust and the like from adhering to the optical disc 1 for a long period of time, a non-woven fabric 22 made of nylon fiber or the like is hot-pressed and touched lightly during rotation of the optical disc 1 to remove the dust and the like adhering to the optical disc 1. I am trying to get rid of it.

In the case of the optical disc 1 according to this embodiment, only the resin is used as a whole, there is no metal film, and there is no bonded structure. Therefore, uneven deformation of the substrate sheet at intervals of several millimeters does not occur due to film-forming stress as in the prior art, and since the front and back surfaces of the optical disk 1 have the same moisture vapor transmission rate, minute deformation due to the influence of moisture in the air also occurs. Does not happen.

As described above, the optical disc 1 according to the present embodiment has very little complicated deformation due to temperature or humidity. The subtle unevenness of the optical disc 1 adversely affects the stabilization of the surface run-out due to the air bearing effect of the stabilizing member 8. However, the optical disc 1 of the present embodiment is also accommodated in the cartridge case 20 for protection. , JIS C5
Even if the 024 temperature / humidity cycle test was performed, there was no hindrance to regeneration. Regarding the jitter, there was no significant difference from the example in FIG.

In the present embodiment having the above-mentioned structure, the case where the anti-reflection coating is applied to the surface of the stabilizing member 8 shown in FIGS. 1 and 3 will be described.

In the optical pickup 6, the laser light La emitted from the semiconductor laser 12 has a wavelength of 405 nm and the objective lens 7 has an NA of 0.85. The signal pits had a shortest pit length of 0.25 μm, a track pitch of 0.35 μm, and a pit depth of 0.1 μm. The signal is a random signal subjected to 1-7 modulation. The thickness t of the flexible optical disk 1 is 40 μm, and the stroke amount d of the objective lens 7 is 100 μm. Therefore, under the above conditions, the optical pickup 6 can physically focus on the surface of the stabilizing member 8.

As shown in FIGS. 1 and 3, the stabilizing member 8
Is installed on the opposite side of the optical disc 1 from the signal recording surface 1a, and is separated from the signal recording surface 1a by only a minute distance. Therefore, if the reflectance of the surface of the stabilizing member 8 is high, the stabilizing member 8 may be focused at the first focusing operation on the signal recording surface 1a. Depending on the surface condition, the malfunction may be reduced by applying the antireflection coating to the surface of the stabilizing member 8.

The stabilizing member 8 is made of stainless steel (SUS3
04), and a ZrO ₂ film was vapor-deposited on the surface. When the optical film thickness is λ / 4n, the reflectance can be minimized. In this example, the optical disc 1 has a thickness of 70 μm,
Since the wavelength of the light beam is 405 nm and the refractive index of ZrO ₂ is about 2.0, the optical film thickness is 50 nm.

In this way, the reflectance of the reproducing light beam on the surface of the stabilizing member 8 becomes equal to or less than the reflectance of the surface of the optical disc 1, so that the focus pull-in is extremely stabilized, and stable focus and tracking are possible. It was

Due to the specifications of the optical pickup 6, the stabilizing member 8
Even with the structure in which the front surface of the optical disk 1 or the rear surface 1b of the optical disk 1 is focused, it is possible to improve the reproduction stability by applying the antireflection coating to the surface of the stabilizing member 8.

When the reproducing power of the semiconductor laser of the optical pickup 6 was set to 1.5 mW or more, the jitter was minimized and stabilized. Therefore, the disk noise limit can be reproduced with the reproducing power of 1.5 mW. The jitter of the reproduced signal was 9% or less, and a signal that could sufficiently reduce the error was obtained.

As another example of the present embodiment, the thickness t of the optical disk 1 is 70 μm, the stroke amount d of the objective lens 7 is 5 μm, the NA of the objective lens 7 is 0.85, and the focus pickup servo of the optical pickup 6 is performed. Assuming that the range p in which an error signal can be generated is 10 μm or less, the relational expression of (d + p <t) is satisfied as 25 + 10 <70. The light spot of the light beam emitted from the optical pickup 6 does not physically move to the surface of the stabilizing member 8.

A non-reflective coating is applied to the surface of the stabilizing member 8 so that the reflectance of the surface of the stabilizing member 8 is low, and because of the thickness of the optical disc 1 and the stroke of the objective lens 7 in the focusing direction, the physical properties are reduced. Due to both of the fact that the surface of the stabilizing member 8 cannot be focused on, the signal recording portion 1a on the surface of the transparent optical disc 1 can be focused most stably and easily. If the stroke of the objective lens 7 in the focus direction is equal to or less than the thickness of the optical disc 1, the stabilizing member 8 is not physically focused. Further, since the depth of focus of the objective lens 7 is substantially several μm or less, it is almost unnecessary to consider the depth of focus. If the stroke of the objective lens 7 in the focus direction is smaller than the thickness of the optical disc 1 by 10 to 20 μm or more, the focusing on the surface of the stabilizing member 8 will hardly occur.

As a result, stable signal reproduction can be carried out, and the jitter of 8 when the reproduction power of the semiconductor laser 12 is 2 mW.
%was gotten.

As another example of the present embodiment, the material of the optical disk 1 is changed to polyethylene terephthalate, and a mixture of about 10% by weight of phthalocyanine pigment is used. The antireflection coating on the surface was omitted.

By mixing the dye in the optical disk 1,
The transmitted 405 nm light beam was absorbed by about 20%. Therefore, the reflected light from the back surface 1b of the optical disc 1 is reduced by about 50%, and the focus pull-in error in the optical pickup 6 is reduced. Further, the influence of reflection on the surface of the stabilizing member 8 is reduced, and even if the non-reflective coating on the surface of the stabilizing member 8 is eliminated, there is no problem with the error rate of the reproduced signal.

As described above, by making the optical disc 1 absorb light, it is possible to improve the readability of the read-only optical disc having no reflective layer as in the present embodiment.

As a method of forming the recording data on the signal recording surface 1a of the optical disc 1, there is a method of recording as a meandering groove in addition to the method of forming the unevenness as described above. The same effect can be obtained regardless of the above.

As a device for obtaining a reproduction signal from the reproduction-only optical disc in the present embodiment as described above, any structure may be used as long as it has the function of the above-described embodiment at the time of reproduction, and may be a reproduction-only device. Also, it can be applied to an apparatus having both recording / reproducing functions.

[0062]

As described above, according to the present invention,
Since the flexible optical disc does not have a special forming film, it is possible to use a flexible optical disc with a low manufacturing cost, and the reproduction light beam receives only interference from the signal recording surface of the flexible optical disc. As a result, the S / N as a reproduction signal is improved. Even if the signal level of the reproduction light beam decreases due to the reduction of the light amount of the reproduction light beam due to the configuration of the flexible optical disk, the reproduction signal with good S / N can be obtained by increasing the light amount of the reproduction light beam. An information reproducing device can be provided.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of an optical disc reproducing apparatus for explaining an embodiment of the invention.

FIG. 2 is an explanatory diagram of a reproducing means in the optical disk reproducing device of FIG.

FIG. 3 is an enlarged explanatory diagram of the optical disc reproducing apparatus of FIG.

FIG. 4 is a waveform diagram of a reproduced signal according to the embodiment of the present invention.

FIG. 5 is a waveform diagram of a reproduction signal in a comparative example of the embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between a signal level and frequency.

FIG. 7 is a cross-sectional view showing an example in which an optical disc according to an embodiment of the present invention is stored in a cartridge.

[Explanation of symbols]

1 optical disc 1a Signal recording surface 6 Optical pickup 7 Objective lens 8 stabilizing members 10 Photoelectric conversion element 11 Reproduction signal processing circuit 12 Laser light source (semiconductor laser) La light beam (emitted light) Lb reproduction light beam (reflected light)

Continued front page    (72) Inventor Shozo Murata             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 5D090 AA02 BB02 CC04 CC14 CC16                       DD03 EE13 FF41 KK02

Claims (4)

[Claims] 1. A flexible optical disk having an exposed signal recording surface, on one side of which recording data is recorded as concaves and convexes or meandering grooves, is irradiated with a light beam, An optical information reproducing apparatus for obtaining a reproduction signal by detecting an optical change in a reproduction light beam from a flexible optical disk, wherein a signal level of noise in the reproduction signal is higher than a signal level of electric system noise in the entire apparatus. The optical information reproducing device is characterized in that the emission power of the light beam is set so that 2. The optical information reproducing apparatus according to claim 1, wherein an amplification gain for the reproduction signal is increased. 3. A stabilizing member for stabilizing surface wobbling during rotational driving of the flexible optical disk by a pressure difference of an air flow is provided on a surface of the flexible optical disk opposite to the signal recording surface. The light reflectance on the surface of the stabilizing member is set to be low by installing the light stabilizer.
The described optical information reproducing device. 4. The optical information reproducing apparatus according to claim 1, wherein a material having a high light absorption property for a light beam is used as a material of the flexible optical disk.