JP2003331454A - Optical disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect the power of recording laser beams with a simple configuration. <P>SOLUTION: In the combination type optical disk drive furnished with an LD 10 for CD and an LD 12 for DVD, the light partially reflected or partially transmitted on a dichroic surface of a dichroic prism is totally reflected further in the surface of the dichroic prism 16 and guided to a photodetector 26. The power of the laser beams is detected by the photodetector 26 and subjected to feedback control. The power of the laser beams is detected by the simple constitution in such a manner that the laser beams are guided to the photodetector 26 by using the dichroic prism 16 itself for combination, not guided by the use of a reflection mirror on an optical path. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk device, and more particularly to a so-called combo type optical disk device for recording / reproducing a plurality of kinds of optical disks.

[0002]

2. Description of the Related Art In recent years, a so-called combo type optical disk device has been developed which is provided with a plurality of light sources for emitting laser beams having different wavelengths and which records and reproduces a plurality of types of optical disks by using the plurality of laser beams. There is. A typical example of such an optical disc device is an optical disc device that performs recording and reproduction on a CD and a DVD.
, A device capable of recording / reproducing data to / from a CD and a DVD, a CD and a D
There are devices that can record and reproduce both VDs. Taking a device for recording / reproducing data on / from a CD and reproducing a DVD as an example, it is equipped with two light sources, a light source for CD and a light source for DVD, and a CD-R or a CD-R
A laser beam having a recording power is emitted to record data on W. Laser light of reproducing power is emitted from the DVD light source. The wavelength of laser light from the light source for CD is about 780n
m, the laser light wavelength from the DVD light source is about 650 nm.

In order to record data on a CD,
It is necessary to control the recording power to a desired value. For example,
In the case of CD-R, the recording film is irradiated with a laser beam and the thermal energy thereof melts and evaporates a part of the recording film to form a pit. Therefore, if the recording power is insufficient or excessive, the shape of the pit becomes defective and the quality deteriorates. Therefore, it is necessary to monitor the intensity of the laser beam having the recording power and perform feedback control so that the intensity becomes a desired value.

As an example of the feedback control, a photodetector is provided in the vicinity of the CD light source, a mirror is provided on the optical path of the laser light emitted from the CD light source, and a part of the laser light is reflected by the mirror and guided to the photodetector. This is a configuration for detecting the intensity.

FIG. 6 shows an example of the structure of an optical pickup for detecting the laser light power. C as light source
LD (laser diode) 10 for D and LD 1 for DVD
2 are provided, and respectively emit a laser light for CD and a laser light for DVD. The CD laser light passes through the coupling lens 14 for adjusting the magnification, and then enters the dichroic prism 16 as a combining prism. On the other hand, the DVD laser light also enters the dichroic prism 16.

The dichroic prism 16 is constructed by cementing two prisms, and the cemented surface constitutes the dichroic surface 16a. The dichroic surface 16a has a characteristic of transmitting light in a specific wavelength region and reflecting light other than that, transmitting CD laser light and reflecting DVD laser light. The optical axes of the CD laser light transmitted through the dichroic surface 16a and the DVD laser light reflected by the dichroic surface 16a coincide with each other. Combined laser light for CD and D
The VD laser light passes through the collimator lens 18 and the objective lens 20, and is applied to the optical disc 22.

When a CD-R or the like is mounted as the optical disk 22 and data is recorded by the laser light from the CD LD 10, the drive current of an LDD (laser diode driver) (not shown) is controlled to emit laser light of recording power. To do. A reflection mirror 24 is provided on the optical path between the coupling lens 14 and the dichroic prism 16, and the emitted C
A part of the laser light for D is reflected and the photo detector 26
Lead to. The laser light power converted into an electric signal by the photo detector 26 is supplied to a controller (not shown) and an LD.
It is fed back to D and adjusted to a desired value.

[0008]

However, in the structure in which the reflection mirror 24 is newly provided on the optical path, there is a problem that the number of parts increases and the cost increases. Further, it is necessary to secure a space for installing the reflection mirror 24 and the photodetector 26, which makes it difficult to reduce the size and weight of the optical pickup. In particular, when the optical disk device is incorporated into a notebook personal computer or the like, it is required to make the entire optical disk device compact, and it is desirable to eliminate extra parts and spaces as much as possible. Further, in the configuration in which a part of the main beam incident on the objective lens is guided to the photodetector by the reflection mirror, there is a problem that the power of the main beam itself is also reduced.

The present invention has been made in view of the problems of the prior art, and an object thereof is to provide an apparatus capable of detecting the power of laser light without increasing the number of parts. Especially.

[0010]

In order to achieve the above object, the present invention is an optical disc apparatus having a plurality of light sources, which records data on an optical disc using light from at least one light source. A plurality of light sources, a dichroic prism having a dichroic surface that transmits at least one of the light from the plurality of light sources and reflects the other, and receives light of the one light that is reflected by the dichroic surface And a light receiving unit that operates.

It is preferable that the light receiving means is arranged in the vicinity of the dichroic prism, and the dichroic prism totally reflects the light reflected by the dichroic surface of the one light and guides it to the light receiving means. .

Further, the present invention is an optical disc apparatus having a plurality of light sources and recording data on an optical disc using light from at least one light source, the plurality of light sources and the light from the plurality of light sources. It is characterized by comprising a dichroic prism having a dichroic surface that transmits at least one of the two lights and reflects the other, and a light receiving unit that receives light of the other light that passes through the dichroic surface.

It is preferable that the light receiving means is arranged in the vicinity of the dichroic prism, and the dichroic prism totally reflects the light passing through the dichroic surface of the other light and guiding it to the light receiving means. .

In the present invention, the plurality of light sources emit long-wavelength laser light and short-wavelength laser light, respectively, or emit CD laser light and DVD laser light, respectively.

As described above, in the optical disk device of the present invention, the dichroic prism for multiplexing a plurality of laser beams is used to guide the laser beams to the light receiving means, thereby eliminating parts such as a reflection mirror. That is, most of the light in the specific wavelength region is transmitted through the dichroic surface (more specifically, the surface on which the dichroic film is formed), but part of the light is reflected without being transmitted. Most of the light in other wavelength regions is reflected, but part of it is transmitted without being reflected.
By receiving these components that do not enter the objective lens by the light receiving means, it is possible to detect the laser light power without affecting the main beam entering the objective lens and without newly installing a reflection mirror or the like.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION <First Embodiment> Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
A description will be given by taking as an example an optical disk device that reproduces data.

FIG. 1 shows the structure of an optical pickup section in an optical disk device. Similar to the configuration shown in FIG. 6, the CD LD 10 and the DVD LD are used as light sources.
12 are provided to emit a laser light for CD having a wavelength of 780 nm and a laser light for DVD having a wavelength of 650 nm, respectively. The laser light for CD passes through the coupling lens 14 and enters the dichroic prism 16 as a multiplexing prism. On the other hand, the DVD laser light also enters the dichroic prism 16. The laser light for CD passes through the dichroic surface 16 a of the dichroic prism 16 and enters the collimator lens 18. The laser light for DVD is
The collimator lens 1 is reflected by the dichroic surface 16a.
It is incident on 8. The laser light for CD and the laser light for DVD, which are combined by the dichroic prism 16 (the optical axes are matched), further enter the objective lens 20, are condensed, and are irradiated onto the optical disk 22.

The optical pickup section shown in FIG. 1 differs from the configuration shown in FIG. 6 in that there is no reflection mirror 24 for reflecting the CD laser light between the coupling lens 14 and the dichroic prism 16. , And CD
The photodetector 26 for receiving the laser light for use is disposed in the vicinity of the specific surface of the dichroic prism 16. The photodetector 26 may be in contact with the surface of the dichroic prism 16 or may be arranged separately. In the present embodiment, the reflection mirror 24 in FIG.
The function of is a dichroic prism 1 which is a combining prism
6 is achieved. The laser light for CD is the dichroic surface 16
Although the laser light for CD is transmitted, not all the laser light for CD is transmitted, and a part (several percent) thereof is transmitted through the dichroic surface 16.
Reflects without passing through a. Conventionally, such a reflection component has not been used, but in the present embodiment, the power of the laser light for CD is detected by positively utilizing this reflection component. Specifically, the CD laser light reflected by the dichroic surface 16a is further totally reflected by the surface of the dichroic prism 16 and guided to the photodetector 26 disposed adjacent to the specific surface. The photodetector 26 converts the received laser light for CD into an electric signal and supplies the electric signal to a controller (not shown) and LDD to feedback-control the laser light power. Dichroic surface 16a
The ratio of light reflected by is known, and the laser light power of the main beam incident on the objective lens 20 can be calculated from the laser power received by the photodetector 26.

FIG. 2 shows the optical path of the CD laser light in the dichroic prism 16. The CD laser light enters from the surface B of the dichroic prism 16 and further enters the position P0 of the dichroic surface 16a. Most of the laser light for CD is dichroic surface 1
6a, dichroic prism 1 from position P3
6 is emitted and enters the collimator lens 18.

On the other hand, the laser light for CD reflected without passing through the dichroic surface 16a reaches the surface B again and is incident on the position P1 of the surface B at the incident angle θ1. When θ1 satisfies the condition of total reflection, that is, θ1 is sin ⁻¹ (n2 / n1) (where n1 is the refractive index of the dichroic prism 16 and n2
Is higher than the refractive index of air), the surface B is totally reflected. Set the Dacroic prism 16 to BK7 glass (refractive index n1 =
In the case of 1.51), total reflection occurs if the angle is 41.5 ° or more. The laser light totally reflected at the position P1 enters the surface A of the dichroic prism 16 at an incident angle θ2, passes through the surface A, and reaches the photodetector 26. The condition that light is transmitted without being totally reflected on the surface A is that θ2 is 41.5 ° when the photodetector 26 is arranged apart from the surface A.
It is less than. When the photodetector 26 is arranged in contact with the surface A, the refractive index of the resin portion of the photodetector 26 is about 1.55, which is higher than the BK7 of the dichroic prism 16. Therefore, in this case, the light is not totally reflected on the surface A and always enters the photodetector 26.

In FIG. 2, the dichroic prism 1
The angle formed by the dichroic surface 16a of 6 and the surface B is φ,
The distance between the position at which the laser light for CD is first incident on the surface B and the position P0 at which it is incident on the dichroic surface 16a is h, and the position at which the laser light for CD is first incident on the surface B and the dichroic surface 16a are reflected on the surface again. The distance from the position P1 incident on B is a, the distance between the position P1 and the surface A is b, the distance between the position P2 and the surface B on which the CD laser light totally reflected on the surface B is incident on the surface A is w, A position P at which the laser light for CD transmitted through the dichroic surface 16a is emitted from the dichroic prism 16.
If the distance between 3 and the surface A is d, the following equation holds.

[0022]

[Formula 1] Incident angle of surface B θ1 = 2 · φ

[Formula 2] Incident angle of surface A θ2 = 90 ° -2 · φ

## EQU00003 ## The exit angle .theta.3 from the surface A = sin ^-1 (n.cos
(2 ・ φ))

[Equation 4] a = h · tan (2 · φ)

[Equation 5] b = d−h · tan (2 · φ)

## EQU00006 ## w = d / tan (2..phi.)-H In these equations, the angle .phi. Required for total reflection of .theta.1 and .theta.2 on the surface B and transmission on the surface A is determined. In addition, the installation position w of the photo detector 26 is also determined.

The reflectance on surface B and the transmittance on surface A are
Calculated as follows from Fresnel's formula.

[0024]

## EQU00007 ## Surface B reflectance R = tan ² (θ ₁ i−θ ₁ t) / t
an ² (θ ₁ i + θ ₁ t)

[Equation 8] Surface A transmittance T = sin (2 · θ ₂ i) sin
(2 · θ ₂ t) / {sin ² (θ ₂ i + θ ₂ t) sin
² (θ ₂ i−θ ₂ t)} In the above equation, θ _j i and θ _j t (j = 1, 2) are the incident angle and the refraction angle at the point P _j, respectively. When the dichroic prism 16 is made of BK7 glass,
1 for the laser light for CD reflected by the dichroic surface 16a
The laser light power emitted from the surface A when 00 (%) is as shown in FIG.

In FIG. 3, the horizontal axis represents the dichroic surface 1.
6a, and the vertical axis represents the ratio of laser light power emitted from the surface A. As can be seen from this graph, when the angle φ is 26 ° or more and 40 ° or less, the dichroic surface 16a
96% or more of the laser light for CD reflected by is emitted from the surface A and received by the photodetector 26. From this,
By setting the angle φ of the dichroic surface 16a in an appropriate range, almost all of the laser light for CD reflected by the dichroic surface 16a is guided to the photodetector 26,
It can be seen that the power of the laser light for CD can be detected.

<Second Embodiment> In the first embodiment described above, the power of the CD laser light is detected by utilizing the reflected light of the CD laser light emitted from the CD LD 10 on the dichroic surface 16a. But DVD as well
It is also possible to detect the power of the laser light for DVD from the LD 12 for use by the photodetector 26. That is, DV
Most of the D laser light is reflected by the dichroic surface 16a, but part of it is transmitted through the dichroic surface 16a. The transmitted DVD laser light reaches the surface B of the dichroic prism 16. Therefore, as in the first embodiment described above, the laser light for DVD reaching the surface B is transferred to the surface B.
By totally reflecting the light on the surface A and transmitting the light through the surface A to the photodetector 26, the power of not only the laser light for CD but also the laser light for DVD can be detected by the single photodetector 26.

FIG. 4 shows the optical path of the DVD laser light in the dichroic prism 16 in this embodiment. Laser light for DVD (wavelength λ2 = 650n
m) enters the dichroic prism 16 and reaches the dichroic surface 16a. Most of the laser light for DVD is reflected by the dichroic surface 16a, but a part (several percent) thereof passes through the dichroic surface 16a and reaches the surface B. The incident angle θ1 on the surface B is sin ⁻¹ (n2 / n1)
In the above case, the light is totally reflected on the surface B. For example, when the dichroic prism 16 is made of BK7 glass, the light is totally reflected and reaches the surface A when the incident angle θ1 is 41.5 ° or more. The condition for the DVD laser light incident on the surface A at the incident angle θ2 to pass through the surface A is that the incident angle θ2 is less than 41.5 °. It can be detected at 26. The arrangement position of the LD 12 for DVD may be adjusted so that θ1 and θ2 satisfy the above condition.

The DVD laser light transmitted through the dichroic surface 16a is incident on the photodetector 26 along the same optical path as the CD laser light reflected by the dichroic surface 16a (however, the refractive index of the dichroic prism 16 is The two optical paths do not exactly coincide with each other due to their influence, because they differ slightly depending on the wavelength.) Therefore, a single photodetector 26 installed at the same position
Thus, the powers of the laser light for CD and the laser light for DVD can be detected. The LD 10 for CD and the LD 12 for DVD are driven alternatively, and the photodetector 26 detects the power of the laser light for CD when driving the CD, and detects the power of the laser light for DVD when driving the DVD.

<Third Embodiment> In the first and second embodiments described above, the LD 10 for a CD and the LD 12 for a DVD are used.
Although the case where the laser light for CD and the laser light for DVD are combined by the dichroic prism 16 using the two light sources described above, the present invention is not limited to the two light sources, and for example, three or more light sources are used. It is also applicable to the case where the light source of is arranged.

FIG. 5 shows the structure of an optical pickup section in which three light sources are arranged. In addition to the CD LD 10 and the DVD LD 12, an LD 13 that emits laser light of shorter wavelength laser light (for example, 405 nm) is provided. Further, a prism 17 is provided as a multiplexing prism in addition to the dichroic prism 16, and the two prisms are joined to form a dichroic surface 17a. C
The CD laser light from the D LD 10 passes through the coupling lens 14 and enters the dichroic prism 16. Further, the DVD laser light from the DVD LD 12 also enters the dichroic prism 16. The laser light for CD passes through the dichroic surface 16a and enters the dichroic prism 17. On the other hand, the DVD laser light is reflected by the dichroic surface 16 a and enters the dichroic prism 17. The laser light for CD and the laser light for DVD both pass through the dichroic surface 17 a and enter the collimator lens 18.

On the other hand, the ultrashort wavelength laser light from the LD 13 passes through the coupling lens 15 and enters the dichroic prism 17. The ultrashort-wavelength laser light is reflected by the dichroic surface 17a, coincides with the optical axis of the CD laser light or the DVD laser light, and enters the collimator lens 18. Thus, the three light sources LD10, LD12, L
Even when three laser lights are emitted from D13, the three laser lights can be combined by using the two combining prisms 16 and 17 and guided to the common objective lens 20.

The photodetector 26 and the photodetector 2 are provided on a specific surface of the dichroic prism 16.
7 are arranged close to each other. The photo detectors 26 and 27 may be arranged in contact with a specific surface of the dichroic prism 16 or may be arranged apart from each other. As described in the first embodiment, most of the laser light for CD is transmitted through the dichroic surface 16a, but a part of it is reflected, and is further totally reflected within the surface of the dichroic prism 16 and received by the photodetector 26. As described in the second embodiment, the DV
Most of the laser light for D is the dichroic surface 16a.
However, a part of the light is transmitted through the dichroic surface 16a, is totally reflected on the surface of the dichroic prism 16 like the CD laser light, and is received by the photodetector 26. Therefore, the photodetector 26 can detect the power of the laser light for CD and the laser light for DVD. Further, most of the ultrashort wavelength laser light from the LD 13 is reflected by the dichroic surface 17a,
A part of the light passes through the dichroic surface 17a and is received by another photodetector 27 which is disposed in the vicinity of the specific surface of the dichroic prism 16. Photo detector 27
The installation position of is adjusted according to the installation position of the LD 13. Therefore, the power of the ultrashort wavelength laser light is detected by the photodetector 27, and the obtained electrical signal is supplied to the controller or LDD, whereby the laser light power of the ultrashort wavelength can be adjusted.

Also in this embodiment, the three laser beams from the three light sources can be guided to the photodetectors 26 and 27 by the combining prism without newly providing a reflection mirror.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made.

For example, in FIG. 5, 3 from 3 light sources
The power of one laser beam is detected by two photo detectors.
The power of the ultra-short wavelength laser light may be detected by the photo detector 27 by detecting only the power of the laser light for DVD or only the power of the laser light for DVD. Further, in FIG. 5, only the photodetector 27 may be arranged close to the dichroic prism 26 and only the power of the ultrashort wavelength laser light may be detected. Further, it may be considered that the outer shape of the dichroic prism 16 is adjusted so that the ultrashort wavelength laser light transmitted through the dichroic surface 17a is further totally reflected within the surface of the dichroic prism 16 and guided to the photodetector 26. In this case, the single photodetector 26 can detect three laser light powers.

[0036]

As described above, according to the present invention, it is possible to detect the power of laser light without increasing the number of parts and without needing to secure an extra space.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is an explanatory diagram of an optical path of a laser light for CD in a dichroic prism.

FIG. 3 is a graph showing the relationship between the angle of the dichroic surface and the ratio of emitted laser light.

FIG. 4 is an explanatory diagram of an optical path of a DVD laser beam in a dichroic prism according to a second embodiment.

FIG. 5 is a configuration diagram of a third embodiment.

FIG. 6 is a configuration diagram of a conventional device.

[Explanation of symbols]

10 LD for CD, 12 LD for DVD, 14 Coupling lens, 16 dichroic prism, 18 Collimator lens, 20 Objective lens, 22 Optical disk,
26,27 Photo detector.

Claims (6)

[Claims] 1. An optical disc apparatus having a plurality of light sources, wherein data from an at least one light source is used to record data on an optical disc, wherein at least two of the plurality of light sources and the light from the plurality of light sources are included. An optical disk device comprising: a dichroic prism having a dichroic surface that transmits one of the two lights and reflects the other; and a light receiving unit that receives the light of the one light that is reflected by the dichroic surface. 2. The apparatus according to claim 1, wherein the light receiving unit is arranged in the vicinity of the dichroic prism, and the dichroic prism totally reflects the light reflected by the dichroic surface of the one light. An optical disk device, characterized in that it is guided to the light receiving means. 3. An optical disc device having a plurality of light sources, wherein data from an at least one light source is used to record data on an optical disc, wherein at least two of the plurality of light sources and the light from the plurality of light sources are included. An optical disk device comprising: a dichroic prism having a dichroic surface that transmits one of the two lights and a reflection of the other light; and a light receiving unit that receives light of the other light that passes through the dichroic surface. 4. The apparatus according to claim 3, wherein the light receiving unit is arranged in the vicinity of the dichroic prism, and the dichroic prism totally reflects the light that passes through the dichroic surface among the other light. An optical disk device, characterized in that it is guided to the light receiving means. 5. The optical disk device according to claim 1, wherein the plurality of light sources emit long-wavelength laser light and short-wavelength laser light, respectively. 6. The optical disk device according to claim 1, wherein the plurality of light sources emit a laser light for CD and a laser light for DVD, respectively.