JP3788873B2 - Optical information recording method and recording / reproducing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention records information on an optical information recording medium in which information can be additionally recorded (added), or reproduces information from a recording medium on which information has already been recorded. Regarding the method.
[0002]
[Prior art]
In recording information on a recording medium capable of optical information recording and reproduction using a light beam and reproducing information from the recording medium, each light beam of the recording beam, tracking beam, focusing beam, and reproduction beam is: A light beam emitted from the same light source is used.
[0003]
A conventional optical information recording / reproducing apparatus is equipped with a plurality of light sources having different wavelengths in order to support various optical information recording media, and recording / reproducing is performed at a wavelength according to the type of the recording medium to be loaded. Even in this case, a light beam emitted from the same light source is used for recording and reproduction on one recording medium.
[0004]
Today, with the advancement of the advanced information society, the information recording / reproducing speed of the recording / reproducing apparatus is improved as the information processing speed of information devices such as computers is improved. However, for example, in the case of a write once optical information recording medium recording / reproducing apparatus capable of writing only once, generally, as represented by the recording speed of the recording apparatus being slower than the reproducing speed of the reproducing apparatus, The recording speed is slower than the playback speed.
[0005]
In recording information on a write-once optical information recording medium, a recording pit can be formed with a smaller output by using a recording beam with a large output and a wavelength at which the recording layer of the medium exhibits a high light absorption rate.
[0006]
because,
The moving speed of the recording head is V (m / S),
The width of the recording beam is D (m),
The recording beam irradiation time is ΔT (s),
The output of the recording beam is P (J / s),
When the absorption coefficient of the recording layer is A,
The energy absorbed during the irradiation time of ΔT is P × A × ΔT, and the area S of the portion that absorbs energy during the irradiation time is indicated by V × D × ΔT, and is absorbed in the area S. The average surface density W (J / m mouth) of the energy
(P × A × ΔT) / (V × D ×× T)
= (P × A) / (V × D)
However, if D is constant, the average surface density of the energy applied to the recording layer is proportional to the absorption rate and inversely proportional to the moving speed of the recording head.
[0007]
For this reason, when the recording speed is increased, it is effective to use a recording light beam having a wavelength that exhibits a high recording output or a high absorption rate.
On the other hand, in information reproduction from a write-once optical information recording medium, a large contrast is produced between the reflected light beam from the recording pit portion of the recording layer of the information recording medium and the reflected light beam from a portion other than the recording pit. As the light beam having the present wavelength is used, a reproduction signal having a higher S / N (signal to noise) ratio can be obtained. Here, qualitative characteristics to be considered in order to obtain a large contrast include, for example, the reflectance of the light beam and the polarization angle of the light beam.
[0008]
By the way, generally, the light beam having the same wavelength does not satisfy the items required for the recording beam and the items required for the reproduction beam at the same time.
For example, the recording layer has an organic dye film and a metal reflective film (that is, a recording layer having a structure in which an organic dye is disposed between the transparent substrate and the metal reflective film) and is irradiated with energy by a laser beam transmitted through the substrate. An information recording medium that can be recorded (written) only once by forming a recording pit by thermal alteration of the organic dye as a recording layer is commercially available. This type of recording medium is shown in FIG. Thus, the recording pit portion for the light beam having a wavelength in the vicinity of the near infrared region and the other portion have characteristics that the reflectance of the recording layer is greatly different. For this reason, when information is reproduced from the recording medium that can be recorded only once, a recording pit obtained by irradiating a near-infrared wavelength light beam whose intensity does not vary with time and monitoring the amount of reflected light. Using the contrast of the amount of reflected light from the other parts, the reproduction light beam of near-infrared wavelength is traversed at a predetermined speed, and the reflected light amount at that time is monitored to reflect the time interval and reflection where the reflected light amount is strong A method of measuring a time interval in which the amount of light is weak is used. In general, in the recording medium described above, the reflectance with respect to near infrared rays having a wavelength of about 800 nm is about 80% in a region other than the recording pit portion (unrecorded portion, curve b), and the recorded pit portion (recorded portion, curve). a) It is about 40% in the region (the reflectivity shown here is a value in the case where the recording layer is provided on a smooth surface without unevenness).
[0009]
On the other hand, when recording information on an unrecorded portion of the write-once optical information recording medium described above, if near infrared light having the same wavelength as the reproduction beam described above is used, as shown in FIG. It remains about 20% {100% -reflectance-transmittance (about 0%), curve b}. This indicates that the recording speed cannot be improved.
[0010]
That is, since the information recording medium that can be recorded only once has a low reflectance and a high absorption rate with respect to a light beam having a wavelength in the visible light region, energy can be recorded by recording information using the light beam in this wavelength region. The efficiency is improved, and as a result, the recording speed can be increased. However, on the other hand, there is almost no difference in the amount of reflected light between the recording pit portion and the portion other than the recording pit with respect to the light beam having a wavelength in the visible light region. This causes a problem that it cannot be used.
[0011]
In order to compensate for this drawback, for example, in Japanese Patent Laid-Open No. 2-187937, “information is recorded by irradiating a recording light beam having a light absorbing property of the recording layer during recording, and lower than the wavelength of the recording light beam. It is disclosed that a previously recorded signal is reproduced by a reproduction light beam having a wavelength exhibiting light absorption ”.
[0012]
[Problems to be solved by the invention]
By the way, also by the recording / reproducing method disclosed in Japanese Patent Laid-Open No. 2-187937, the wavelength of the light beam at the time of recording and at the time of reproducing is changed (a plurality of light sources are installed and used according to recording and reproduction). There is a problem that needs to be selected). Further, at the time of recording, a recording light beam having a wavelength having a light absorption property of the recording layer was irradiated to record a signal, and the signal was recorded by a reproducing light beam having a wavelength lower than the wavelength of the recording light beam. If the signal is reproduced, information recording can be performed at a higher speed at the time of recording while maintaining the S / N of the reproduced signal, but the restriction from the maximum output value of the light source cannot be removed. Note that, for a recording layer having the characteristics already shown in FIG. 2, there is a problem that an expected recording speed is not improved only by using a light beam having a wavelength exhibiting a high absorption rate when recording on an unrecorded portion. is there.
[0013]
That is, as already shown in FIG. 2, even if the absorptivity of the unrecorded portion with respect to near infrared rays having a wavelength of about 800 nm is about 20%, a change occurs in the dye film when information is actually recorded. Since the absorptance rises to about 70%, when a recording light beam having a low absorptivity in an unrecorded portion is irradiated, the recording layer has a low absorptance immediately after irradiation (starting moment), and energy utilization efficiency Although the phenomenon that the absorptance increases as the recording pits are formed and the energy efficiency is improved is observed, a light beam having a wavelength that exhibits an absorptance of about 50% with respect to the unrecorded part is observed. Even if it is used, the increase in the absorption rate as described above does not occur, so that there is a problem that an improvement in recording speed cannot be expected.
[0014]
Further, since the emission wavelength of a semiconductor laser generally used as a light source in an optical information recording medium recording / reproducing apparatus changes due to temperature change, the absorptance of the recording layer of the optical information recording medium with respect to slight wavelength change. When information is recorded using a light beam with a wavelength that greatly changes the optical information recording medium, the temperature of the semiconductor laser element changes due to a change in the temperature outside the device and the emission wavelength changes. As a result, the recording layer has a change in the absorptance of the recording layer, and the recording sensitivity changes greatly. As a result, a new problem arises in that jitter increases during reproduction.
[0015]
An object of the present invention is to provide an optical head device that is used for recording / reproducing for an optical information recording medium having a high recording speed and capable of stably reproducing a recorded signal.
[0016]
[Means for Solving the Problems]
This invention is based on the above problems, A first light source that emits a light beam of a first wavelength, a second light source that emits a light beam of a second wavelength different from the first wavelength, and each of the first and second light sources And an optical system that guides the emitted light beam to a recording medium in an overlapping manner on substantially the same optical path, and includes the first and second light sources. The wavelength of the light beam emitted by at least one light source is ,Record The amount of energy absorbed by the recorded portion of the recording layer of the recording medium is a high wavelength, The wavelength of the light beam emitted from at least one of the first and second light sources is ± 5% in the change in the absorptance of the unrecorded portion of the optical information recording medium with respect to the change in wavelength of ± 10 nm. Within the wavelength range, When recording information, From each of the first and second light sources Light beam But, at the same time On recording media Irradiation Be done Information recording characterized by /Regeneration apparatus What to provide It is.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an optical head device capable of recording information on an optical information recording medium and reproducing information from the recording medium and a recording / reproducing method thereof will be described with reference to the drawings.
[0018]
As shown in FIG. 1, an optical head device 1 emits a first semiconductor laser element 11 that emits a light beam (laser beam) having a first wavelength, and a light beam (laser beam) having a second wavelength. The second semiconductor laser element 21 is provided. The semiconductor laser elements 11 and 21 are arranged so that the polarization directions of the laser beams emitted from the semiconductor laser elements 11 and 21 are orthogonal to each other.
[0019]
The laser beam emitted from the first semiconductor laser element 11 is collimated through the first collimating lens 12, passes through the polarization beam splitting surface 13 a of the polarization beam splitter 13, and is a λ / 4 plate (retarder) 14. Thus, the direction of polarized light is converted from linearly polarized light to circularly polarized light and guided to the objective lens 15.
[0020]
The laser beam guided to the objective lens 15 is converged by the objective lens 15 on a recording layer (a dye layer between the transparent substrate and the reflective film) (not shown) of the optical disc D that is an optical information recording medium.
[0021]
The laser beam that reaches the recording layer of the optical disk D and is reflected by the reflecting film is returned to the objective lens 15 again, and passes through the λ / 4 plate 14 so that the direction of polarization is changed from circularly polarized light toward the optical disk. It is converted into linearly polarized light directed in a direction different from the direction of polarization by 90 ° and returned to the polarization beam splitter 13.
[0022]
The laser beam returned to the polarization beam splitter 13 is now reflected by the beam split surface 13a, passes through the half mirror beam splitter 16 having a transmittance of approximately 20%, and enters a light receiving surface (not shown) of the photodetector 17. Is done.
[0023]
On the other hand, the laser beam emitted from the second semiconductor laser element 21 is collimated through the second collimating lens 22, and is approximately 80% (preferably at least 3/4 or more) of the light intensity by the half mirror beam splitter 16. Is reflected and guided to the polarization beam splitter 13.
[0024]
The laser beam from the second semiconductor laser element 21 guided to the polarization beam splitter 13 is further reflected by the polarization beam split surface 13a (the polarization direction of the laser beam is the first semiconductor laser element as already described). In this case, the laser beam is rotated by 90 ° with respect to the laser beam 11, and the polarization direction is converted from linearly polarized light to circularly polarized light by the λ / 4 plate 14 and guided to the objective lens 15.
[0025]
The laser beam from the second semiconductor laser element 21 guided by the objective lens 15 is converged on a recording layer (a dye layer between the transparent substrate and the reflective film) (not shown) of the optical disc D by the objective lens 15.
[0026]
The laser beam from the second semiconductor laser element 21 that has reached the recording layer of the optical disk D and reflected by the reflecting film is returned again to the objective lens 15 and passes through the λ / 4 plate 14 to cause the direction of polarization. Is converted into linearly polarized light directed in a direction 90 ° different from the direction of polarization when traveling from the circularly polarized light toward the optical disk, and returned to the polarization beam splitter 13.
[0027]
In FIG. 1, an optical head device using a collimator lens, a λ / 4 plate (retarder), and a polarization beam splitter has been described as an example, but light that does not use a λ / 4 plate (does not use a polarization beam splitter). The head device can be similarly configured. That is, a known semiconductor laser element is used today by adding a second laser element corresponding to the encircled portion in FIG. 1 and a half mirror for beam synthesis during recording to one optical head device. It can be applied to almost all optical head devices.
[0028]
By the way, as already described with reference to FIGS. 2 and 3, the write-once type recording medium that can be written only once among the optical information recording media has a laser beam wavelength and reproduction suitable for recording. The wavelength of the suitable laser beam is different.
[0029]
Here, in the optical head device 1 shown in FIG. 1, the wavelengths of the laser beams emitted by the first and second semiconductor laser elements 11 and 21 are optimally combined (for example, the second semiconductor laser element 21 emits). The laser beam wavelength is set to a wavelength that maximizes the amount of energy absorbed by the recording layer of the recording medium. Speed can be increased.
[0030]
That is, as already shown in FIG. 3 with respect to the energy absorption characteristics of the recording medium, even if the absorptivity of the unrecorded portion with respect to near infrared rays having a wavelength of about 800 nm is about 20% (curve b), When information starts to be recorded, a change occurs in the dye film and the absorptance rises to about 70% (see curve b in FIG. 2). Therefore, a recording light beam having a wavelength with a low absorptance is applied to the unrecorded portion. When irradiated, immediately after irradiation (moment of starting), the absorption rate of the recording layer is low and the energy utilization efficiency is low, but the absorption rate increases as the recording pits are formed, and the energy efficiency is improved (recording) Speed is improved). Note that, as shown in FIG. 4A, the radiation control (light emission timing) of the laser beam emitted from the laser element gives a large output at the start of recording, and the output level is set at a predetermined ratio after a certain period of time. A method of reducing is used. According to such light emission control, it is possible to prevent the width of the recording pit formed on the recording medium from expanding with time.
[0031]
The optical information recording medium to be recorded is a normally available write-once recording medium, in which the groove (guide groove) has a spiral shape, a groove width of about 0.8 μm, and a groove depth. On a transparent plastic plate having a diameter of 120 mm and a thickness of 1.2 mm with a groove pitch of about 1.6 μm and an organic dye having a thickness of about 0.1 μm and gold (Au ) Of a group called a known CD-R having a recording layer on which a film (reflective film) is laminated and a protective layer such as an ultraviolet curable resin for protecting the recording layer (reflective film).
[0032]
In the CD-R described above, the recording layer, that is, the organic dye is a recording formed by a method described in detail later by using an appropriate material from cyanine-based, phthalocyanine-based, or azo-based organic dyes. The pit (recorded portion) and the portion other than the recorded pit (unrecorded portion) provide a contrast with a large reflectance with respect to a laser beam (reproduced light) having a near infrared wavelength.
[0033]
Hereinafter, recording of information on the CD-R and reproduction of information from the CD-R will be described in detail. That is, by the method described below, the energy of the laser beam can be efficiently absorbed into the recording layer during recording without deteriorating the S / N of the reproduction signal, and the recording speed can be improved.
[0034]
[Example 1]
In the optical head device 1 shown in FIG. 1, the first and second semiconductor laser elements are laser elements having an emission wavelength of 780 nm. Hereinafter, using a well-known control circuit (not shown), a recording signal is connected in parallel to each of the two semiconductor laser elements, and the respective semiconductor laser elements are driven simultaneously.
[0035]
As a result, the energy of the laser beam applied to the recording layer cannot be simply regarded as being doubled, but is increased as compared with a method of driving only one of the laser elements. However, since the amount of reflected light guided to the photodetector 17 is lower than that of a known optical head device, it is preferable to increase the amplification factor of an amplifier (not shown).
[0036]
In the known optical head device, the intensity of the laser beam that can use the laser beam (energy) emitted from the laser element as a focused spot is about ¼ of the total energy of the laser beam emitted from the laser element. is there. Further, since the allowable radiation capacity of a general semiconductor laser that emits a laser beam having a wavelength of 780 nm is about 50 mW in intermittent radiation, the energy irradiated to the recording layer is about 12 mW at the maximum.
[0037]
Based on these conditions, the CD-R linear velocity (rotational speed) is changed from 1 m / second to 20 m / second, and the length of the recording pulse and the interval between the recording pulses are changed in accordance with the linear velocity. A sample was created by irradiating a CD-R with a laser beam of 20 mW in total from the laser element, and then the reflected light amount was monitored by running a constant beam of 0.1 mW over the recorded track. A signal modulated well up to about 20 m / sec was obtained.
[0038]
For comparison, when the output of one laser element was stopped, the output was set to 12 mW, a similar sample was created, and the reflected light was monitored by irradiating the recorded track with a constant beam of 0.1 mW. A well-modulated signal was obtained up to a linear velocity of about 7 m / sec.
[0039]
Therefore, it is confirmed that by using two semiconductor laser elements having the same emission wavelength and simultaneously emitting a laser beam, the laser element can increase the recording speed as compared with one known recording apparatus and recording method. It was done.
[0040]
[Example 2]
In the optical head device 1 shown in FIG. 1, a semiconductor laser element that emits a laser beam having a wavelength of 780 nm is used for one of the two semiconductor laser elements, and a semiconductor laser element that emits a laser beam having a wavelength of 730 nm is used for the other. Use.
[0041]
Here, a laser beam with a wavelength of 780 nm is used for well-known tracking and focusing by irradiating a laser beam with a wavelength of 780 nm at a constant output, and the laser beam with a wavelength of 730 nm is irradiated intermittently. As shown in FIG. 4B, the emission control (light emission timing) of the laser beam emitted from each laser element gives a large output at the start of recording, and the output level is set to a predetermined level after a certain time has elapsed. A method of decreasing in proportion is used. According to such light emission control, it is possible to prevent the width of the recording pit formed on the recording medium from expanding with time. As is clear from FIG. 4B, the laser beam having a wavelength of 730 nm is not continuously emitted at a constant intensity, but the output is varied within a predetermined intensity range.
[0042]
According to this configuration, while a recording beam having a wavelength of 730 nm is irradiated, a laser beam having a wavelength of 780 nm is also irradiated. As a result, two laser beams from the respective laser elements constitute a recording beam. For reproduction, a continuous beam having a wavelength of 780 nm may be used. In this case, the output of the continuous beam at the time of reproduction may be an output level according to recording or an output level lower than that.
[0043]
By the way, in the configuration of Example 2, when a laser beam having a wavelength of 780 nm is used for recording simultaneously with a laser beam having a wavelength of 730 nm during recording, the laser beam having a wavelength of 780 nm with respect to the recording layer of the recording medium is absorbed by the unrecorded portion as already described. The degree to which the recording is performed is about 20%, but increases to about 60% at the same time as the recording is started. Therefore, the absorption rate increases as the recording pits are formed, and the energy efficiency is improved. Therefore, even if a laser beam having a wavelength at which the recording layer does not exhibit a large absorptance when unrecorded, it contributes to the improvement of the recording capability by giving a trigger, so that the recording speed is increased.
[0044]
In addition, using the above-mentioned conditions, while irradiating a continuous beam having a wavelength of 780 nm and 2 mW from one light source, an intermittent beam having a wavelength of 730 nm and 10 mW is irradiated from the other light source, and the linear velocity is changed from 1 m / second to 20 m / second. Samples were prepared while changing the recording pulse length and recording pulse interval in accordance with the linear velocity (tracking and focusing at this time are 730 nm, 0. 3mW laser beam was used), and then a constant beam with a wavelength of 780 nm and 0.1 mW was run on the recorded track and the amount of reflected light was monitored. As a result, a signal modulated well to a linear velocity of about 15 m / second was obtained. Obtained.
[0045]
Here, for comparison, the linear velocity is changed from 1 m / sec to 20 m / sec using only a laser beam having a wavelength of 730 nm, and the length of the recording pulse and the interval between the recording pulses are changed in accordance with the linear velocity. A sample was irradiated with a 10 mW recording beam intermittently (tracking and focusing at this time use a 730 nm, 0.3 mW laser beam while the recording beam was stopped), and then similarly, a wavelength of 780 nm. When the laser beam was run and the amount of reflected light at that time was monitored, a well-modulated signal was obtained up to a linear velocity of about 10 m / sec.
[0046]
By the way, in the configuration shown in this example 2, it is necessary to use a laser beam exhibiting a low absorption rate in an unrecorded portion at the time of reproduction, that is, a good reproduction signal is applied to a laser beam that can be used for reproduction. This indicates that there is a restriction on the wavelength that can be obtained. For this reason, in the method in which the laser element that emits the reproducing laser beam is also used during recording, the wavelength of the reproducing laser beam cannot be freely set. However, as the wavelength of the other recording beam, a semiconductor laser element capable of emitting a laser beam of an arbitrary wavelength whose absorptance does not change with respect to a change of ± 10 nm of a predetermined wavelength at which absorption by the recording medium is maximum is used. Can be used.
[0047]
Therefore, two semiconductor laser elements that emit laser beams having different wavelengths are used, and the emission wavelength of one laser element is set to a wavelength in the vicinity of the wavelength (± 10 nm) at which the recording layer of the recording medium has the maximum absorption, and the other By providing the light emission wavelength of one of the laser elements to a wavelength suitable for reproducing information recorded on a recording medium, an optical head device having a high recording speed and capable of obtaining a stable reproduction signal is provided. .
[0048]
Next, an optical head device that can cope with a change in wavelength of a laser beam emitted from a semiconductor laser element due to a temperature change will be considered.
A laser having a wavelength of 780 nm from the first semiconductor laser element in the optical head device 1 shown in FIG. 1 is used for the optical information recording medium comprising the recording layer having the absorption / reflection characteristics already described with reference to FIGS. Consider recording information using a laser beam having a wavelength of 720 nm from the second semiconductor laser element.
[0049]
When the absorption / reflection characteristics of the recording layer of the recording medium are the characteristics shown in FIGS. 2 and 3, the absorption rate is about 23% at the wavelength of 780 nm of the laser beam emitted by the first laser element. When the wavelength changes by ± 10 nm, the absorptance changes from about 17% to about 34%. The rate of change at this time is 74% to 147% when 23% is 100 (the rate of change of the absorption rate is -26% to + 47%). On the other hand, at the wavelength 720 nm emitted by the second laser element, the absorptance is about 64% and the energy efficiency is high, but when the wavelength changes ± 10 nm, the absorptance is about 56% to about 71%. Change to. The variation rate at this time is 88% to 110% when 64% is 100 (the change rate of the absorption rate is −12% to + 11%).
[0050]
Accordingly, when the wavelength of each laser beam emitted from each laser element changes by ± 10 nm, the rate of change of the absorption rate of the information recording medium changes by more than ± 10%.
[0051]
This is because even when information is recorded using a laser beam of the same output, the recording sensitivity changes by more than 10% when the emission wavelength changes by ± 10 nm due to temperature changes of the laser element body and the surroundings. As a result, it becomes difficult to form a recording pit having an optimum size by controlling the recording output. The optimum recording pit size referred to here indicates the size of the recording pit that minimizes jitter during reproduction.
[0052]
In other words, in optical information reproduction, the length of recorded pits and the length of unrecorded parts are detected as signals, so when the recording sensitivity changes, the length of recorded pits and the length of unrecorded parts change. Jitter increases.
[0053]
Since the correct reproduction cannot be performed when the jitter level exceeds a certain value, the size of the recording pit must be controlled to be as close as possible to the optimum value. A recording method that can form recording pits with high accuracy only by output control is required.
[0054]
This is because, as already described in Example 2 above, a change of ± 10 nm of a predetermined wavelength at which absorption by the recording medium is maximized as the wavelength of a laser element that emits a recording beam using two semiconductor laser elements. This is easily achieved by emitting a laser beam of any wavelength that does not change the absorption rate, and setting the emission wavelength of the other laser element to a wavelength suitable for reproducing information recorded on the recording medium. Is done. The wavelength of the laser element that emits the recording beam is selected so that the rate of change of the absorption rate of the information recording medium is preferably ± 5% or less.
[0055]
【The invention's effect】
As detailed above, the present invention Information recording / reproducing device Accordingly, in recording information on a write once optical information recording medium that can be written only once, the amount of energy absorbed by the recording layer can be improved without deteriorating the characteristics of the reproduced signal during reproduction. Thereby, the recording speed can be increased.
[0056]
In addition, since the emission wavelength of a laser element that mainly emits laser light having a recording wavelength can be set to a wavelength at which the energy absorption of the recording layer of the recording medium is high, the wavelength of the recording laser light may vary. Even if it exists, the fluctuation | variation of recording sensitivity can be suppressed. This can suppress jitter generated in the recorded signal and achieve highly stable recording.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a configuration of an optical head device according to an embodiment of the present invention.
2 is a graph for explaining the relationship between the reflectance and wavelength of a recording layer of an optical information recording medium on which information is recorded by the optical head device shown in FIG. 1;
FIG. 3 is a graph for explaining the relationship between the energy absorption amount and the wavelength of the recording layer of the optical information recording medium on which information is recorded by the optical head device shown in FIG. 1;
4 is a timing chart showing an example of control of the emission timing of a laser beam emitted from a laser element when information is recorded by the optical head device shown in FIG.
[Explanation of symbols]
1 ... Optical head device,
11... First semiconductor laser element,
12 ... collimating lens,
13: Polarizing beam splitter,
14 λ / 4 plate (retarder),
15 ... objective lens,
16 ... Beam splitter,
17... Photodetector
21... Second semiconductor laser element,
22: Collimating lens.

Claims (1)

A first light source that emits a light beam of a first wavelength;
A second light source that emits a light beam having a second wavelength different from the first wavelength;
An optical system for guiding a light beam emitted from each of the first and second light sources to a recording medium by superimposing them on substantially the same optical path;
With
The wavelength of the light beam at least one of the light sources emits the first and second light sources, the wavelength energy is high to be absorbed by the recorded portion of the recording layer of the record medium, and wherein the first and The wavelength of the light beam emitted from at least one of the second light sources is such that the change in the absorptance of the unrecorded portion of the optical information recording medium is within ± 5% with respect to the change in wavelength of ± 10 nm. The information recording / reproducing apparatus is characterized in that, at the time of information recording , a light beam from each of the first and second light sources is simultaneously irradiated onto the recording medium .

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