JP2003272209A - Optical recording/reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control variation of intensity distribution of an incident luminous flux on an objective lens, and to prevent expansion of a condensing spot diameter coping with the control, when a semiconductor laser is used which emits a light flux with a variable angle of divergence according to an optical output. <P>SOLUTION: According to recording/reproducing by an optical recording/ reproducing device, a focal position of a collimator lens is shifted, in a constitution which makes the collimator lens move to an optical, axis direction of the light flux. <P>COPYRIGHT: (C)2003,JPO

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, and more particularly to an optical recording / reproducing apparatus using a semiconductor laser in which a divergence angle of a light beam varies.

[0002]

2. Description of the Related Art Optical discs include music CDs and DVD-
Play-only discs such as VIDEO and CD-R
There are discs capable of recording / reproducing represented by / RW and DVD-R / RW. In recording on a CD-R / RW or the like, a high-intensity light spot is focused on the optical disk, and the heat of the light spot causes a change in reflectance to cause "1",
Record the "0" signal.

As a conventional example, FIG. 8 shows a schematic optical system of an optical recording / reproducing apparatus for generating the above-mentioned condensed spot. Figure 8
In FIG. 1, 1 is a light source (for example, a semiconductor laser), 2 is a beam splitter, 3 is a collimator lens, 4 is an objective lens, 5 is an actuator for controlling the objective lens 4, 6 is a photodetector, and 7 is an optical information recording medium. (Hereinafter referred to as an optical disc).

In the optical recording / reproducing apparatus shown in FIG. 8, the light beam emitted from the semiconductor laser 1 is reflected by the beam splitter 2.
Through the collimator lens 3, and after being converted into a substantially parallel light beam by the collimator lens 3, the light beam enters the objective lens 4. The objective lens 4 focuses the incident light flux on the information surface of the optical disc 7 as a spot of about 1 micron, but since the optical disc 7 is rotated by a motor (not shown), surface wobbling and eccentricity occur. . Therefore, in a state where nothing is controlled, the light spot cannot accurately follow the track on the optical disk 7. Therefore, the actuator 5 controls focusing and tracking so that the light spot always exists on the track of the information surface.

The luminous flux reflected by the optical disk 7 is
It again passes through the objective lens 4 to become a substantially parallel light beam, which is converted into a condensed light beam by the collimator lens 3, reflected by the beam splitter 2, incident on the photodetector 6, photoelectrically converted, and processed by an electric system.

In an optical recording / reproducing apparatus for recording / reproducing,
The intensity of the light spot is required to be about 15 mW during recording.
A high output semiconductor laser 1 is mounted, which is different from a read-only type which requires only about mW. The semiconductor laser 1 is a light source that emits divergent light as shown in FIG. 9, and its divergence angle differs in a direction (x direction) parallel to the active layer of the laser chip and a direction (z direction) perpendicular thereto. The intensity distribution of the emitted light flux is a Gaussian distribution. As the divergence angle, the angle at which the intensity is 1 / e ² with respect to the central intensity, and the direction parallel to the active layer is θ.
The x and vertical directions are defined as θz. The divergence angle of a general high-power semiconductor laser 1 is θx of 14 degrees and θz of 34 degrees.

Next, the size of the focused spot when the substantially parallel light flux having the Gaussian distribution is focused by the objective lens 4 will be described with reference to FIGS. 10 and 11.

FIG. 10 is a diagram schematically illustrating the relationship between a substantially parallel light beam having a Gaussian distribution which is incident on the objective lens 4 and a focused spot where the substantially parallel light beam is converted by the objective lens 4. A light flux having a Gaussian distribution is incident from the left side of FIG. Here, the radius where the intensity becomes 1 / e ² of the central intensity is defined as Wa (referred to as the light beam diameter). FIG. 10 shows a state in which a substantially parallel light beam is incident on the objective lens 4 in accordance with the optical system of FIG.
When the focal position of the collimator lens 3 in FIG. 8 is f, there is a relationship of Wa = f × sin θ (1). Where θ is θx or θ shown in FIG.
means z.

On the other hand, the diameter of the incident light beam is limited to the objective lens 4, and as shown in FIG. 10, an aperture having a radius a is provided. Then, the size of the condensed spot condensed by the objective lens 4 is defined as the size at which 1 / e ² is also obtained with respect to the central intensity, and the radius of the condensed spot at that time is Wo (condenser). Called spot diameter)
Is defined as

The focused spot diameter Wo when focused by the objective lens 4 is the smallest in the case of a plane wave in which the intensity distribution of the incident light flux is uniform, and in the case of a substantially parallel light flux having a Gaussian distribution. The focused spot diameter Wo is larger than that when the plane wave is focused. This variation of the focused spot diameter Wo changes depending on the state of the Gaussian distribution, and in FIG. 10, when the aperture diameter a of the objective lens 4 is sufficiently smaller than Wa indicating the spread of the Gaussian distribution of the substantially parallel light flux, the substantially parallel light flux. Is equivalently the same as when is a plane wave.

There are various relationships between the ratio of the diameter Wa of the substantially parallel light beam entering the objective lens 4 to the aperture diameter a of the objective lens 4 and the size of the focused spot diameter Wo focused by the objective lens 4. It is shown in the literature, for example, in "Optical Disc Technology" (published by Radio Technology Co., Morio Onoue et al.). FIG. 11 is published in the above-mentioned document, and the ratio of the substantially parallel light beam diameter Wa incident on the objective lens 4 to the aperture diameter a of the objective lens 4 and the focused spot diameter Wo.
It is a figure which shows the relationship with the magnitude | size of. In FIG. 11, the horizontal axis is the ratio of Wa to a, and the coefficient of vignetting m (= a / W
a), and the vertical axis represents the spot size ratio. Specifically, the ratio (= Wo / We) of the focused spot diameter Wo to the spot diameter We when the plane wave is focused is It is shown.

Therefore, it can be seen from FIG. 11 that the focused spot diameter Wo increases as the coefficient of eclipse m increases. Further, it can be seen that if the eclipse coefficient m is reduced, a small focused spot diameter Wo can be obtained, and good recording / reproducing characteristics can be obtained. However, a small eclipse coefficient m means that the objective lens It is shown that the ratio of the substantially parallel light flux incident on the beam No. 4 is small, and that the transmittance (= the output intensity of the objective lens / the output intensity of the semiconductor laser) of the optical system as a whole is lowered.

On the other hand, the output of the semiconductor laser 1 is increasing year by year, but the recording speed is also increasing, and the strength required for recording is also increasing. Therefore, there is no margin in the output of the semiconductor laser 1, and it is necessary to make the transmittance of the optical system as large as possible, and the optical system is designed to satisfy the contradictory requirements of the focused spot diameter Wo and the output intensity of the semiconductor laser 1. Is designed.

[0014]

By the way, the luminous flux from the semiconductor laser 1 has divergence angles θx and θz as shown in FIG.
It is a divergent light with, but until now, this divergence angle θ
x and θz did not depend so much on the output of the semiconductor laser 1. However, as a measure for higher output, the semiconductor laser 1
The structure has been changed so that a high output can be ensured with a low drive current, and at the same time, a property that the divergence angles θx and θz change corresponding to the output of the semiconductor laser 1 has also appeared.

The amount of change in the divergence angles θx and θz is about 1 to 2 degrees in the x direction parallel to the active layer, but as described above, the original divergence angle θx in the direction parallel to the active layer is 14 degrees. Since it is small, the contribution of the change is large. On the other hand, although the change also occurs in the direction perpendicular to the active layer (z direction), the amount of change is small and the original divergence angle θz itself is large at about 34 degrees, so the contribution of the change is small.

Regarding the polarity of the change, the divergence angle changes in the direction of increasing as the output of the semiconductor laser 1 increases. Therefore, when designed as an optical system for recording, the output of the semiconductor laser 1 can be small during reproduction, so that the divergence angle of the semiconductor laser 1 is smaller than the divergence angle during recording. Then, Wa becomes smaller than the expression (1), and as a result, the coefficient m of the eclipse becomes large. From FIG. 11, when the eclipse coefficient m increases, the focused spot diameter Wo
However, as a result, the reproduction performance deteriorates.

Therefore, the present invention has been made in order to solve the above-mentioned problems, and even in an optical recording / reproducing apparatus using a semiconductor laser whose divergence angle changes depending on the output, the output can be obtained. The objective is to provide an optical recording / reproducing apparatus capable of obtaining a converging spot diameter Wo as designed, without depending on it, and capable of obtaining good recording / reproducing performance.

[0018]

In order to achieve the above object, an optical recording / reproducing apparatus according to the present invention is an optical recording / reproducing apparatus capable of recording / reproducing information on / from an optical information recording medium. A light source that emits a light beam with different emission outputs during recording and reproduction, an objective lens that focuses the light beam from the light source on the optical information recording medium, and an intensity distribution of the light beam that enters the objective lens And a light flux adjusting means for adjusting corresponding to the recording and the reproducing.

Further, the light flux adjusting means may be a collimator lens which is arranged between the light source and the objective lens and is movable in the optical axis direction of the light flux.

Further, the light flux adjusting means changes the optical distance between the collimator lens arranged between the light source and the objective lens and the optical distance between the light source and the collimator lens. And means.

Further, the optical distance changing means may be a first optical element having a refractive index different from that of air, which can be put in and taken out from an optical path between the light source and the collimator lens.

The luminous flux adjusting means is arranged between the collimator lens arranged between the light source and the objective lens, and between the light source and the collimator lens, and diverges the luminous flux from the light source. A coupling lens that has a small angle and is movable in the optical axis direction of the light flux may be provided.

The light flux adjusting means may be a light intensity attenuating means disposed between the light source and the objective lens to attenuate the intensity of the light flux emitted from the light source.

Further, in an optical recording / reproducing apparatus capable of recording / reproducing information on / from an optical information recording medium, a light source for emitting a light beam with the same emission output during recording and reproduction, and a light beam from the light source. The light flux adjusting means comprises an objective lens for converging on the optical information recording medium, and a light flux adjusting means for adjusting the intensity distribution of the light flux incident on the objective lens in correspondence with the recording and the reproduction. May be a light intensity attenuator arranged between the light source and the objective lens to attenuate the intensity of the light flux emitted from the light source.

Further, the light intensity attenuating means may be a second optical element which can be put in and taken out from an optical path between the light source and the objective lens.

Further, a collimator lens arranged between the light source and the objective lens is further provided, and the second optical element is put in and out of an optical path between the light source and the collimator lens. It is possible, and it may further have a function of changing the optical distance between the light source and the collimator lens.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to the drawings showing the embodiments thereof. The same reference numerals as those used in the prior art indicate the same or equivalent members.

<First Embodiment> FIG. 1 is a diagram showing a schematic optical system of an optical recording / reproducing apparatus of the present embodiment. Figure 1
In FIG. 1, 1 is a light source (for example, a semiconductor laser), 2 is a beam splitter, 3 is a collimator lens, 4 is an objective lens, 5 is an actuator for controlling the objective lens 4, 6 is a photodetector, and 7 is an optical information recording medium. (Hereinafter, referred to as an optical disc). Here, the collimator lens 3 can be moved in the optical axis direction of the light flux by a moving mechanism (not shown).

Next, the operation will be described. The light beam emitted from the semiconductor laser 1 passes through the beam splitter 2, is converted into a substantially parallel light beam by the collimator lens 3 arranged at the focal position, and then enters the objective lens 4. The objective lens 4 passes the incident substantially parallel light flux onto the optical disk 7
It is condensed as a condensed spot of about 1 micron on the information surface of. Here, focusing and tracking are controlled by the actuator 5 with respect to surface wobbling and eccentricity of the optical disk 7 so that a focused spot always exists on the information track. The condensed spot reflected by the optical disk 7 is transmitted through the objective lens 4 again to become a substantially parallel luminous flux, converted into a condensed luminous flux by the collimator lens 3, reflected by the beam splitter 2, and incident on the photodetector 6. It is photoelectrically converted and processed in the electrical system.

If the divergence angle of the light beam emitted from the semiconductor laser 1 does not change, this state is acceptable, but the output intensity of the semiconductor laser 1 changes between recording and reproduction, and the light is emitted from the semiconductor laser 1. The divergence angles θx and θz of the light flux change, and the diameter of the focused spot increases. Therefore, in accordance with this change, the position of the collimator lens 3 is moved in the optical axis direction of the light beam, and the relationship between the intensity distribution of the light beam entering the objective lens 4 and the aperture diameter of the objective lens 4 is suppressed so as not to change. The objective lens 4 allows the optical disk 7
It is also possible to suppress changes in the diameter of the focused spot focused on the. This situation will be described with reference to FIG.

FIG. 2 shows only the semiconductor laser 1 and the collimator lens 3 in FIG. 1, and when the collimator lens 3 is a lens having an infinite diameter, the luminous flux incident on the objective lens 4 is shown. The relationship between the intensity distribution 11 (the range of the intensity of 1 / e ² with respect to the central intensity is shown by a curve) and the aperture diameter 10 of the objective lens 4 is shown. Here, the size of the aperture diameter 10 is constant in all the states of FIG.

FIG. 2A shows the state of recording (semiconductor laser 1
The intensity distribution of the substantially parallel light flux entering the objective lens 4 from the semiconductor laser 1 is shown in FIG.
And the aperture diameter 10 of the objective lens 4 are as designed.

Next, FIG. 2B shows the same optical system when the intensity of the semiconductor laser 1 is at the time of reproduction (the output intensity is smaller than that at the time of recording), and the substantially parallel light flux at the objective lens 4 is shown. The relationship between the intensity distribution 11 and the aperture diameter 10 is shown. As described above, as the property of the semiconductor laser 1, the divergence angle becomes smaller as the output intensity becomes smaller. Therefore, the intensity distribution 11 becomes smaller than that at the time of recording, and in particular, the variation amount of θx in the direction of small divergence angle (x direction) is large. . Where the dotted line is
The intensity distribution at the time of recording is shown, and the solid line shows the intensity distribution 11 changed by the time of reproduction.

Further, FIG. 2C is a diagram in which the collimator lens 3 is moved from the state of FIG. 2B to the semiconductor laser 1 side along the optical axis direction of the light flux. Semiconductor laser 1
Since the light emitting point of is shifted from the focal position of the collimator lens 3 in the direction of shortening, the light flux transmitted through the collimator lens 3 enters the objective lens 4 as a divergent light flux. Therefore, the relationship between the aperture diameter 10 of the objective lens 4 and the intensity distribution 11 of the incident light flux is almost the same in the x direction as during recording,
In the z direction, the intensity distribution 11 becomes wider than that at the time of recording. Here, the dotted line shows the intensity distribution during recording, and the solid line shows the state of the intensity distribution 11 during reproduction when the collimator lens 3 is moved.

Looking at the relationship of the focused spot diameters in each state of FIG. 2, since the coefficient m of the eclipse in the x direction is large in the state of (b), the design of (a) in the x direction. The focused spot diameter is larger than the value. On the other hand, in the state of (c), the x direction has the same relationship as the design value of (a), and the focused spot diameter in the x direction is as designed, but in the z direction, the design value state. Since the coefficient of vignetting m is smaller, the focused spot diameter is further smaller. However, in the state of (c), the transmittance of the optical system is smaller than that in the state of (a), so that the utilization factor of the light flux of the semiconductor laser 1 is lowered. However, the state where this adjustment is performed is during reproduction, and the semiconductor laser 1 for recording has a sufficient margin with respect to the reproduction intensity, so there is no problem at all.

As described above, in this embodiment, since the position of the collimator lens 3 is changed in the optical axis direction of the light beam, even if the divergence angle of the light beam from the semiconductor laser 1 changes, the collimator lens 3 is moved to the objective lens 4. It is possible to adjust the intensity distribution 11 of the incident light flux, and it is possible to suppress the change in the focused spot diameter.

<Second Embodiment> FIG. 3 is a diagram showing a schematic optical system of an optical recording / reproducing apparatus according to a second embodiment of the present invention. The optical recording / reproducing apparatus of the present embodiment is
It can be moved in and out of the optical path between the beam splitter 2 and the collimator lens 3 of the conventional device (see FIG. 8),
A first optical element (for example, a glass plate) 20 having a refractive index higher than that of air is newly provided. The other configuration is similar to that of FIG. 8, and thus the description is omitted.

Next, the operation will be described. When recording,
The first optical element 20 is outside the optical path, and the semiconductor laser 1
Has its light emitting point located at the focal position of the collimator lens 3, so that the light flux transmitted through the collimator lens 3 is converted into a substantially parallel light flux. The converted substantially parallel light flux is incident on the objective lens 4 having an aperture diameter of a predetermined size, and in the objective lens 4, the substantially parallel light flux is converted into the optical disk 7.
It is condensed as a condensed spot of about 1 micron on the information surface of.

As described with reference to FIG. 2, at the time of reproduction, the divergence angle in the direction of the light beam emitted from the semiconductor laser 1 becomes small and the focused spot diameter becomes large. Therefore, the light beam leaving the collimator lens 3 is slightly increased. By making it divergent, it is possible to prevent expansion of the focused spot diameter. Therefore, by inserting the first optical element 20 into the optical path between the beam split 2 and the collimator lens 3, the refractive index of the first optical element 20 is larger than the refractive index of air. The optical distance between the collimator lens 3 and the collimator lens 3 is shortened, and the state is equivalent to that the collimator lens 3 approaches the semiconductor laser 1. That is, the collimator lens 3 is displaced from the focal position. Specifically, the optical distance in the first optical element 20 having a thickness t and a refractive index N is t /
Since it is represented by N, the distance is shortened by t−t / N which is the difference from the actual distance t. Therefore, the light flux that has passed through the collimator lens 3 can be made into a divergent light flux.

As described above, since the first optical element 20 can be put into and taken out of the optical path by the optical recording / reproducing apparatus having the above-mentioned configuration, the first optical element 20 can be put in the optical path at the time of reproduction and the collimator. The light beam that has passed through the lens 3 can be made a slightly divergent light beam. Therefore, the objective lens 4
It is possible to widen the intensity distribution of the incident light flux to the light source and suppress the expansion of the focused spot diameter.

Further, in the present embodiment, the semiconductor laser 1
To the collimator lens 3 without changing the actual distance, the physical distance is used to shorten the distance between them to obtain an optical distance that is always accurate and stable.

Here, in this embodiment, the first optical element 20 is arranged between the beam split 2 and the collimator lens 3 (see FIG. 3), but as shown in FIG. It is also possible to adopt a configuration in which it can be taken in and out from the split 2. However, in this case, since the light flux reflected from the optical disk 7 and traveling to the photodetector 6 is not attenuated, the conjugation relationship between the light emitting point of the semiconductor laser 1 and the light receiving surface of the photodetector 6 is determined. The first optical element 20 to be kept needs to be further configured to be able to be put in and taken out between the beam split 2 and the photodetector 6.

<Third Embodiment> FIG. 5 is a diagram showing a schematic optical system of an optical recording / reproducing apparatus according to a third embodiment of the present invention. In the optical recording / reproducing apparatus of the present embodiment, in order to efficiently convert the light flux of the semiconductor laser 1 in the collimator lens 3, the optical path between the beam splitter 2 and the collimator lens 3 of the conventional apparatus (see FIG. 8). A coupling lens 30 having a function of reducing the divergence angle of the light beam emitted from the semiconductor laser 1 is newly provided therein. Further, by moving the position of the coupling lens 30 in the optical axis direction of the incident light flux, an optical system for converting the divergence angle of the light flux emitted from the semiconductor laser 1 is configured. The other configuration is similar to that of FIG. 8, and thus the description is omitted.

Next, the operation will be described. At the time of recording, the coupling lens 30 and the collimator lens 3
Is arranged at a predetermined position, and the light beam emitted from the semiconductor laser 1 passes through the beam split 2, the coupling lens 30, and the collimator lens 3 and is converted into a substantially parallel light beam by the collimator lens 3. The converted substantially parallel light flux has an objective lens 4 having an aperture diameter of a predetermined size.
Then, the objective lens 4 focuses the substantially parallel light flux on the information surface of the optical disc 7 as a focused spot of about 1 micron.

As described with reference to FIG. 2, during reproduction, the divergence angle of the light beam emitted from the semiconductor laser 1 becomes small,
Since the focused spot diameter becomes large, the collimator lens 3
By making the outgoing light flux slightly divergent, it is possible to prevent the focused spot diameter from expanding. Therefore, by moving the position of the coupling lens 30 in the optical axis direction of the light beam incident on the lens 30, the position of the collimator lens 3 is not at the focal position, so that the light beam that has passed through the collimator lens 3 is changed to that shown in FIG. It is possible to obtain a slightly divergent light flux as shown in. Here, by using the coupling lens 30 having a lower light condensing power than the collimator lens 3, the position control can be performed more accurately than when the collimator lens 3 is moved (in the case of the first embodiment). Is.

In this way, in the optical recording / reproducing apparatus of the present embodiment, the coupling lens 30 is inserted between the semiconductor laser 1 and the collimator lens 3 and the coupling lens 30 is used as a light beam for reproduction. Since it is configured to move in the axial direction, it is possible to easily adjust the intensity distribution of the light flux incident on the objective lens 4, and it is possible to accurately suppress the expansion of the focused spot diameter.

<Fourth Embodiment> FIG. 6 is a diagram showing a schematic optical system of an optical recording / reproducing apparatus according to a fourth embodiment of the present invention. The optical recording / reproducing apparatus of the present embodiment is
It can be moved in and out of the optical path between the beam splitter 2 and the collimator lens 3 of the conventional device (see FIG. 8),
A second optical element (for example, an ND filter) 40 that attenuates the intensity of the incident light beam is newly provided. Further, the point different from the other embodiments is that the intensity of the light beam emitted from the semiconductor laser 1 is high during reproduction. The other configuration is similar to that of FIG. 8, and thus the description is omitted.

As described in the above embodiment, the parameter of the divergence angle change of the light beam output from the semiconductor laser 1 is the output intensity of the semiconductor laser 1, and the divergence occurs during reproduction, that is, when the output intensity is low. The corner becomes smaller. Therefore, even during reproduction, by increasing the output intensity of the semiconductor laser 1 more than during normal reproduction, it is possible to suppress the expansion of the focused spot diameter during reproduction. However, if the output intensity of the semiconductor laser 1 is simply increased at the time of reproduction, the intensity of the focused spot incident on the optical disk 7 is too large, and normal reproduction processing cannot be executed.

Therefore, as in the present embodiment, at the time of reproduction, the second optical element 40 for attenuating the intensity of the incident light beam is inserted in the optical path between the beam splitter 2 and the collimator lens 3. As a result, even if the intensity of the light beam output from the semiconductor laser 1 is increased, the intensity of the focused spot incident on the optical disc 7 can be suppressed to a level at which normal reproduction processing can be performed.

At the time of recording, the second optical element 40 is located outside the optical path between the beam splitter 2 and the collimator lens 3 so that the output intensity of the semiconductor laser 1 is not reduced, and the semiconductor laser 1 is provided with the second optical element 40. Since the light emitting point is arranged at the focal position of the collimator lens 3, the light flux transmitted through the collimator lens 3 is converted into a substantially parallel light flux. The converted substantially parallel light beam is incident on the objective lens 4 having an aperture diameter of a predetermined size, and in the objective lens 4, the substantially parallel light beam is formed as a focused spot of a predetermined size on the information surface of the optical disk 7. Focus.

With the above structure, the second optical element 40 is inserted into the optical path diameter at the time of reproduction, so that the output of the semiconductor laser 1 can be increased even at the time of reproduction, and the divergence angle changes depending on the output. Even when the semiconductor laser 1 is used, the divergence angle can be reduced and the focused spot diameter can be prevented from expanding.

Further, since the second optical element 40 also has a large refractive index with respect to air, the collimator lens 3 may be used to convert the substantially parallel light beam into a slightly divergent light beam as in the second embodiment. It becomes possible, the coefficient of eclipse m becomes small, and further reduction of the focused spot diameter at the time of reproduction can be promoted.

Since the second optical element 40 is inserted in the optical path between the beam splitter 2 and the collimator lens 3 in FIG. 6, the light flux reflected by the optical disk 7 and directed to the photodetector 6 is also the second. Since the light passes through the optical element 40, the amount of light incident on the photodetector 6 is also attenuated.

However, as shown in FIG.
In the optical path between the beam splitter 2 and the beam splitter 2, when the second optical element 40 is configured to be able to be put in and taken out, the light flux toward the photodetector 6 is not attenuated, but the light emission of the semiconductor laser 1 Since the point and the light-receiving surface of the photodetector 6 are in a conjugate relationship, it is necessary to further arrange the second optical element 40 that maintains the conjugate relationship between the beam splitter 2 and the photodetector 6. is there.

Further, the collimator lens 3 and the objective lens 4
A configuration is also possible in which the second optical element 40 can be put in and taken out in the optical path between and. In this case, since the light flux from the semiconductor laser 1 is converted into a substantially parallel light flux by the collimator lens 3, Although it is not possible to reduce the diameter of the focused spot due to the refractive index of the second optical element 40, the output intensity of the semiconductor laser 1 can be increased during reproduction, so that the divergence angle can be suppressed from decreasing and the focused light can be focused. Normal reproduction processing can be executed while preventing the spot diameter from increasing.

Further, the output intensity of the semiconductor laser 1 at the time of reproduction is set to the same output intensity as that at the time of recording, and the luminous flux intensity is sufficiently attenuated by the second optical element 40 to reduce the focused spot diameter to the maximum. Is possible.

[0057]

The optical recording / reproducing apparatus according to the first aspect of the present invention is an optical recording / reproducing apparatus capable of recording / reproducing information on / from an optical information recording medium, and is different between recording and reproducing. A light source that emits a light beam with an emission output, an objective lens that collects the light beam from the light source on the optical information recording medium, and an intensity distribution of the light beam that enters the objective lens during the recording and the reproduction. Since the light beam adjusting means for adjusting correspondingly is provided, it is possible to suppress the change of the intensity distribution of the light beam incident on the objective lens at the time of recording and reproducing, and thereby the light beam is condensed by the objective lens. It is possible to suppress the expansion of the diameter of the focused spot.

In the optical recording / reproducing apparatus according to the second aspect of the present invention, the light flux adjusting means is disposed between the light source and the objective lens and is movable in the optical axis direction of the light flux. Since it is a lens, by changing the position of the collimator lens in the direction of the optical axis of the light beam, the focal position is deviated, and for example, at the time of reproduction, it is converted into a slightly diffused light beam by the collimator lens. Therefore, even when the divergence angle of the light flux from the light source changes, it is possible to suppress the change in the intensity distribution of the light flux incident on the objective lens, and it is possible to suppress the change in the focused spot diameter.

In the optical recording / reproducing apparatus according to a third aspect of the present invention, the light flux adjusting means includes a collimator lens arranged between the light source and the objective lens, the light source and the collimator lens. Since the optical distance changing means for changing the optical distance between the light source and the collimator lens is provided, it is possible to cause a change in the optical distance between the light source and the collimator lens. A shift occurs, and for example, at the time of reproduction, it is converted into a slightly diffused light flux by the collimator lens. Therefore, even when the divergence angle of the light flux from the light source changes, it is possible to suppress the change in the intensity distribution of the light flux incident on the objective lens, and it is possible to suppress the change in the focused spot diameter.

In the optical recording / reproducing apparatus according to a fourth aspect of the present invention, the optical distance changing means is a refractive index different from air that can be put in and taken out from the optical path between the light source and the collimator lens. Since it is the first optical element having, the distance between the optical elements can be shortened in terms of the optical distance by using a physical feature, and an accurate and stable change of the optical distance can always be obtained.

In the optical recording / reproducing apparatus according to claim 5 of the present invention, the light flux adjusting means includes a collimator lens arranged between the light source and the objective lens, the light source and the collimator lens. And a coupling lens that is disposed between the light sources and reduces the divergence angle of the light beam from the light source and that is movable in the optical axis direction of the light beam. By moving the beam to the position, the intensity distribution of the light flux incident on the objective lens can be easily adjusted, and the change in the focused spot diameter can be easily suppressed. Furthermore, by using a coupling lens having a lower light condensing power than the collimator lens, it is possible to perform position control more accurately than moving the collimator lens (in the case of claim 2). Further, since the coupling lens has a function of reducing the divergence angle of the light flux emitted from the light source, the light flux of the light source can be efficiently converted in the collimator lens.

In the optical recording / reproducing apparatus according to the sixth aspect of the present invention, the light flux adjusting means is disposed between the light source and the objective lens and attenuates the intensity of the light flux emitted from the light source. Since it is a light intensity attenuator that makes it possible to suppress the reduction of the divergence angle from the light source by increasing the output of the light source during playback, normal playback processing is performed even if the output of the light source is increased. can do. As a result, it is possible to suppress the expansion of the focused spot diameter during reproduction.

An optical recording / reproducing apparatus according to a seventh aspect of the present invention is an optical recording / reproducing apparatus capable of recording / reproducing information on / from an optical information recording medium, and has the same emission output during recording and reproduction. A light source that emits a light beam, an objective lens that collects the light beam from the light source on the optical information recording medium, and an intensity distribution of the light beam that enters the objective lens at the time of the recording and the time of the reproduction. Since the light flux adjusting means is a light intensity attenuating means that is disposed between the light source and the objective lens and attenuates the intensity of the light flux emitted from the light source, By setting the output intensity of the light source during reproduction to the same output intensity as during recording and sufficiently attenuating the luminous flux intensity by the light intensity attenuating means, the focused spot diameter can be reduced most.

In the optical recording / reproducing apparatus according to the eighth aspect of the present invention, the light intensity attenuating means is a second optical element which can be inserted into and removed from the optical path between the light source and the objective lens. Therefore, in a simple structure of the optical system device, it is possible to obtain the same effects as those of claims 6 and 7.

An optical recording / reproducing apparatus according to a ninth aspect of the present invention further comprises a collimator lens arranged between the light source and the objective lens, and the second optical element is the light source. Since the optical path between the light source and the collimator lens can be moved in and out, and a function of changing an optical distance between the light source and the collimator lens is further provided, an effect similar to that of claim 8 is obtained. In addition to,
Furthermore, the optical distance can be changed by the second optical element, and the collimator lens can be used to convert the light flux into a slightly divergent light flux during playback, and the focused spot diameter during playback. Can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an optical recording / reproducing apparatus according to a first embodiment.

FIG. 2 is a diagram showing a change in intensity distribution of a light beam incident on an objective lens due to a change in output of a semiconductor laser and a change in position of a collimator lens.

FIG. 3 is a schematic diagram showing a configuration of an optical recording / reproducing apparatus according to a second embodiment.

FIG. 4 is a schematic diagram of an optical recording / reproducing apparatus showing another configuration position of the first optical element.

FIG. 5 is a schematic diagram showing a configuration of an optical recording / reproducing apparatus according to a third embodiment.

FIG. 6 is a schematic diagram showing a configuration of an optical recording / reproducing apparatus according to a fourth embodiment.

FIG. 7 is a schematic diagram of an optical recording / reproducing device showing another configuration position of the second optical element.

FIG. 8 is a schematic diagram showing a configuration of a conventional optical recording / reproducing apparatus.

FIG. 9 is a diagram showing how a light beam emitted from a semiconductor laser diverges.

FIG. 10 is a diagram showing a state of intensity distribution of a substantially parallel light beam incident on an objective lens and a condensed spot converted by the objective lens.

FIG. 11 is a diagram showing a relationship between a focused spot diameter converted by an objective lens and a light beam diameter incident on the objective lens.

[Explanation of symbols]

1 light source (semiconductor laser), 3 collimator lens, 4
Objective lens, 7 Optical information recording medium (optical disk), 10 Aperture diameter, 11 Light intensity distribution, 2
0 first optical element, 30 coupling lens, 40
Second optical element.

Continued front page    F-term (reference) 5D119 AA11 AA22 BA01 BB01 BB02                       BB04 DA01 DA05 EB02 EB03                       EC37 FA05 HA66 JA02 JA43                       JA63 JA70 LB11                 5D789 AA11 AA22 BA01 BB01 BB02                       BB04 DA01 DA05 EB02 EB03                       EC37 FA05 HA66 JA02 JA43                       JA63 JA70 LB11

Claims (9)

[Claims] 1. An optical recording / reproducing apparatus capable of recording / reproducing information on / from an optical information recording medium, wherein a light source for emitting a light beam with different emission outputs during recording and reproduction and a light beam from the light source are provided. An objective lens for condensing on the optical information recording medium, and a light flux adjusting means for adjusting the intensity distribution of the light flux incident on the objective lens in correspondence with the recording and the reproduction. Optical recording / reproducing device. 2. The light flux adjusting means is a collimator lens which is arranged between the light source and the objective lens and is movable in the optical axis direction of the light flux. Optical recording / reproducing device. 3. The light flux adjusting means changes the optical distance between the collimator lens arranged between the light source and the objective lens and the optical distance between the light source and the collimator lens. The optical recording / reproducing apparatus according to claim 1, further comprising: 4. The optical distance changing means is a first optical element having a refractive index different from that of air, which can be put in and taken out from an optical path between the light source and the collimator lens. The optical recording / reproducing apparatus according to claim 3. 5. The light flux adjusting means is arranged between the light source and the objective lens, and a collimator lens is arranged between the light source and the collimator lens.
The optical recording / reproducing apparatus according to claim 1, further comprising: a coupling lens that reduces a divergence angle of the light beam from the light source and is movable in an optical axis direction of the light beam. 6. The light flux adjusting means is a light intensity attenuating means which is disposed between the light source and the objective lens and attenuates the intensity of the light flux emitted from the light source. Item 1. The optical recording / reproducing apparatus according to Item 1. 7. An optical recording / reproducing apparatus capable of recording / reproducing information on / from an optical information recording medium, wherein a light source for emitting a light beam with the same emission output during recording and reproduction, and a light beam from the light source. The light flux adjusting device comprises: an objective lens that focuses the light on the optical information recording medium; and a light flux adjusting unit that adjusts the intensity distribution of the light flux incident on the objective lens in correspondence with the recording and the reproduction. The means is an optical intensity attenuating means that is disposed between the light source and the objective lens and attenuates the intensity of the light flux emitted from the light source. 8. The light intensity attenuating unit is a second optical element that can be inserted into and removed from an optical path between the light source and the objective lens, according to claim 6 or 7. The optical recording / reproducing apparatus described. 9. A collimator lens arranged between the light source and the objective lens is further provided, and the second optical element is inserted into and removed from an optical path between the light source and the collimator lens. The optical recording / reproducing apparatus according to claim 8, further comprising a function of changing an optical distance between the light source and the collimator lens, which is possible.