JP3804231B2 - Optical pickup - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup that reproduces an optical recording medium by selectively using two types of lasers having different wavelengths, and particularly relates to an optical pickup that is reduced in size and cost.
[0002]
[Prior art]
For example, in a DVD (digital video disc) player, a short wavelength laser for DVD (wavelength of about 650 nm) and a CD are used as an optical pickup to be able to reproduce both DVD and CD (compact disc). There are lasers (hereinafter referred to as “two-wavelength compatible optical pickups”) that perform reproduction using two types of lasers (laser (wavelength of about 780 nm)).
[0003]
Conventionally, as a method of constructing components (laser diode, optical system such as objective lens, diffraction grating, beam splitter, and photodetector) for reproducing each of DVD and CD in such a two-wavelength optical pickup, the following method is used. Something existed.
[0004]
(A) A laser diode that emits one of two types of lasers and a photodetector (including a necessary optical system) that detects the return light, and a laser that emits the other laser The diode and the photodetector for detecting the return light are not integrated but are installed as individual components (discrete).
[0005]
(B) a laser diode that emits one of two types of lasers, a photodetector that detects the return light, a laser diode that emits the other laser, and a photodetector that detects the return light. , Integrate as separate bodies.
[0006]
An example of the configuration of a two-wavelength compatible optical pickup employing the method (a) is shown in FIG. The integrated unit 11 includes a laser diode LD (not shown) that emits a laser L1 having a wavelength of about 780 nm for CD, a photodetector PD (not shown) that makes its return light incident, and a microprism (not shown). It is an integrated one. The laser L1 emitted from the laser diode LD in the unit 11 is incident on the beam splitter 12, reflected by the reflection surface thereof, made parallel by the collimator lens 13, reflected by the 45 degree mirror 14, and reproduced as not shown. After being directed to the recording surface of the target CD (not shown), it is converged by the objective lens 15 and irradiated onto this recording surface.
[0007]
The return light from the recording surface of the CD is reflected again by the beam splitter 12 through the objective lens 15, the 45-degree mirror 14, and the collimator lens 13, returns to the unit 11, and enters the photo detector PD in the unit 11. A signal processing system (not shown) of the DVD player detects a tracking error signal and a focus error signal during reproduction of a CD and a reproduction signal based on light incident on the photodetector PD.
[0008]
On the other hand, the laser diode 16 emits a laser L2 having a wavelength of about 650 nm for DVD. The laser L2 passes through both the beam splitters 17 and 12, and is irradiated on the recording surface of a DVD (not shown) to be reproduced through the collimator lens 13, the 45 degree mirror 14, and the objective lens 15.
[0009]
The return light from the DVD recording surface passes through the beam splitter 12 again through the objective lens 15, 45 degree mirror 14, and collimator lens 13, and then is reflected by the beam splitter 17 to improve the detection accuracy of the focus error signal. For this purpose, the beam diameter is enlarged by the concave cylindrical lens 18 and then incident on the photodetector 19. In the signal processing system, the tracking error signal and the focus error signal during the reproduction of the DVD and the reproduction signal are detected based on the incident light to the photodetector 19.
[0010]
An example of the configuration of the two-wavelength compatible optical pickup employing the method (b) is as shown in FIG. 5 (the same parts as in FIG. ). In this optical pickup, a laser diode LD2 (not shown) that emits a laser L2 having a wavelength of about 650 nm for DVD, a photodetector PD2 (not shown) that makes its return light incident, and a microprism (not shown), The integrated unit 20 is integrated.
[0011]
The laser L2 emitted from the laser diode LD2 in the unit 20 passes through the beam splitter 12, passes through the collimator lens 13, the 45 degree mirror 14, and the objective lens 15, and is recorded on a DVD (not shown) to be reproduced. The surface is irradiated.
[0012]
The return light from the recording surface of the DVD passes through the objective lens 15, the 45 ° mirror 14 and the collimator lens 13, passes through the beam splitter 12, returns to the unit 20, and is incident on the photodetector PD 2 in the unit 20.
[0013]
[Problems to be solved by the invention]
However, in the method of integrating only one of the CD and DVD playback parts of (a) above, there is a disadvantage that the size is increased due to the large number of parts as shown in FIG. It was.
[0014]
On the other hand, in the method of integrating both the CD and DVD playback parts in (b), the number of parts is reduced as compared with the method in (a) as shown in FIG. Therefore, a certain size reduction is realized. However, this system has the disadvantage that the cost increases because two integrated units for CD playback and DVD playback are provided. Also in this method, as shown in FIG. 5, the beam splitter 12 that plays the role of matching the optical paths of the lasers L1 and L2 and the role of making the optical paths of the return lights different from each other is necessary. was there.
[0015]
The present invention has been made in view of the above points, and an object of the present invention is to provide a two-wavelength optical pickup that realizes further miniaturization and cost reduction.
[0016]
[Means for Solving the Problems]
An optical pickup according to the present invention emits a first laser in an optical pickup that reproduces an optical recording medium by selectively using a first laser and a second laser having different wavelengths. A first laser light source, a second laser light source that emits a second laser, a laser emitted from the first laser light source, and a collimator lens that collimates the laser emitted from the second laser light source An objective lens for condensing the laser beam collimated by the collimator lens onto the optical recording medium, a light branching means for branching the return light from the optical recording medium, and a return branched by the light branching means a light detecting means for detecting light, the first and the laser light source and the second laser light source in the range of about 200~500μm The first laser light source, the second laser light source, the light branching means, and the light detecting means are integrated as a unit, and the objective lens and the collimator lens are integrated. An optical path synthesizing element having a function of tilting a laser beam incident vertically so that the laser beam incident in an oblique direction is aligned with the laser beam incident vertically is arranged. To do.
[0017]
According to this two-wavelength optical pickup, the laser light source that emits the first laser and the laser light source that emits the second laser are integrated together, so that these laser light sources are integrated into the same casing. Stored. As a result, the number of housings is reduced as compared to the case where these laser light sources are provided separately as in the methods (a) and (b) (that is, these laser light sources are housed in separate housings). Therefore, downsizing and cost reduction are realized.
[0018]
As an example, in this two-wavelength compatible optical pickup, the return light from the optical recording medium of the first laser and the return light from the optical recording medium of the second laser are both the same integrated type. It is preferable that the light is branched by the light branching means in the unit and detected by the light detection means in the unit.
[0019]
By doing so, one photodetecting means in the same unit is shared between the reproduction of the optical recording medium by the first laser and the reproduction of the optical recording medium by the second laser. Therefore, as compared with the case where two photodetecting means are provided as in the above methods (a) and (b), further miniaturization and cost reduction are realized.
[0020]
In addition, by doing so, the return light of the first laser and the return light of the second laser are incident on the same unit (that is, the optical paths of these return lights before entering the light detection means are substantially the same. Therefore, the optical paths of the first laser and the second laser and the optical paths of these return lights substantially coincide with each other over the entire length. Therefore, the beam splitters (the beam splitters 12 and 17 in FIG. 4 and the figure) that play the role of matching the optical paths of these lasers as in the systems (a) and (b) and the optical path of the return light. The beam splitter 12) in FIG. 5 is not necessary, so that further miniaturization and cost reduction can be realized from this point.
[0021]
In addition, since the first and second lasers and the return light do not need to pass through the beam splitter in this way, the laser is compared with the case of passing through the beam splitter as in the methods (a) and (b). The optical path is shortened (projection area is reduced).
[0022]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an example of the configuration of an integrated unit of a two-wavelength optical pickup according to the present invention.
[0023]
The integrated unit 1 includes a laser diode 3 that emits a laser L1 having a wavelength of about 650 nm for DVD, a laser diode 4 that emits a laser L2 having a wavelength of about 780 nm for CD, and a plurality of laser diodes 4 on a photodiode IC2. The photodetector 5 having the sensor elements 5a to 5d and the micro prism 6 functioning as a reflection mirror are provided in an integrated manner, and the 0th order light and the + order light of the return light from the disk to be reproduced are provided above the microprism 6. The hologram plate 7 for branching the −1st order light and making it incident on the sensor elements 5a to 5d is provided, and these are arranged in one casing (for example, a can package as shown in FIG. 2 or a plastic package). It is what was stored.
[0024]
The laser diode 3 and the laser diode 4 are arranged in contact with each other on the LOP 8 so that their back surfaces are aligned with each other, and the distance between the light emitting points of these laser diodes is about 10 μm.
[0025]
FIG. 2 shows an example of the overall configuration of a two-wavelength compatible optical pickup using such an integrated unit 1. The same parts as those in FIG.
[0026]
The laser L1 emitted from the laser diode 3 in the integrated unit 1 in which the components shown in FIG. 1 are housed in the can package CP is reproduced through the collimator lens 13, the 45 degree mirror 14, and the objective lens 15. The recording surface of the target CD (not shown) is irradiated.
[0027]
The return light from the recording surface of the CD returns to the unit 1 again through the objective lens 15, 45 degree mirror 14, and collimator lens 13, and is branched by the hologram plate 7 (FIG. 1), and the microprism 6 (FIG. 1). And is incident on the sensor elements 5 a to 5 d (FIG. 1) of the photodetector 5. In a signal processing system (not shown) of an optical DVD player equipped with this two-wavelength pickup, detection of a tracking error signal and a focus error signal at the time of reproducing a CD is performed based on incident light to the sensor elements 5a to 5d. The reproduction signal is detected.
[0028]
On the other hand, the laser L2 emitted from the laser diode 4 in the integrated unit 1 also passes through the collimator lens 13, the 45-degree mirror 14, and the objective lens 15 in the same manner as the laser L1 emitted from the laser diode 3. The recording surface of a DVD (not shown) is irradiated.
[0029]
The return light from the recording surface of the DVD returns to the unit 1 through the objective lens 15, 45 ° mirror 14, and collimator lens 13 as well as the return light of the laser L 1, and is branched by the hologram plate 7. The light is reflected and enters the sensor elements 5 a to 5 d of the photodetector 5. In the signal processing system described above, the tracking error signal and the focus error signal and the reproduction signal are detected during reproduction of the DVD based on the incident light on the sensor elements 5a to 5d.
[0030]
According to this two-wavelength optical pickup, the laser diode 3 that emits the laser L1 for CD and the laser diode 4 that emits the laser L2 for DVD are integrated into the unit 1 and integrated into one unit package CP. Therefore, as compared with the conventional case where these laser diodes are housed in separate housings, a reduction in size and cost can be realized by reducing the number of housings.
[0031]
In addition, since one photo detector 5 in the same unit 1 is shared between the CD reproduction by the laser L1 and the DVD reproduction by the laser L2, compared with the conventional case where two photo detectors are provided, Further downsizing and cost reduction are realized.
[0032]
Further, since the optical paths of the lasers L1 and L2 and the optical paths of these return lights substantially coincide with each other over the entire length, the roles of matching the optical paths of these lasers as in the prior art and the roles of making the optical paths of the return lights different In this respect, further downsizing and cost reduction are realized.
[0033]
In addition, since the lasers L1 and L2 and the return light do not pass through the beam splitter in this way, the optical path of the laser is shortened compared to the case of passing through the beam splitter as in the conventional case (the projection area is reduced). ).
[0034]
Next, FIG. 3 shows another example of the configuration of the integrated unit of the two-wavelength optical pickup according to the present invention. The same parts as those in FIG. . In this integrated unit 9, the laser diode 3 and the laser diode 4 are arranged at a certain distance (about 200 to 500 μm) on the LOP 8 without bringing the back surfaces of the laser diode 3 and the laser diode 4 into contact with each other as in the unit 1 of FIG. Are spaced apart by a distance within the range of
[0035]
The overall configuration of the two-wavelength compatible optical pickup using the integrated unit 9 may be the same as that shown in FIG. 2 as an example. However, in this integrated unit 9, the distance between the light emitting point of the laser diode 3 and the light emitting point of the laser diode 4 is considerably larger than in the unit 1 of FIG. 1, so that the optical axes of the emitted lasers L1 and L2 The deviation of the direction is increased accordingly. As a result, for example, when the laser L1 that has passed through the collimator lens 13, the 45-degree mirror 14, and the objective lens 15 is irradiated perpendicularly to the recording surface of the CD to be reproduced, the laser L2 that has passed through these is ignored in terms of reproduction accuracy. There is a possibility that the recording surface of the DVD to be reproduced is irradiated at an angle separated from the vertical as much as possible. (On the other hand, in the integrated unit 1 of FIG. 1, it can be said that the deviation in the optical axis direction of the lasers L1 and L2 is so small as to be negligible within the error range in terms of reproduction accuracy.)
[0036]
Therefore, when the integrated unit 9 is used, for example, between the collimator lens 13 and the 45-degree mirror 14 shown in FIG. By providing a hologram element having a function of tilting most of the + and −1 order lights so that the direction of the optical axis coincides with the former laser, both of the lasers L1 and L2 are placed on the recording surface of the disc to be reproduced. It is preferable to irradiate vertically.
[0037]
In the above example, both the return light from the CD of the laser L1 and the return light from the DVD of the laser L2 are returned to the unit 1 and passed through the hologram plate 7 and the microprism 6 by the sensor elements 5a to 5d of the photodetector 5. Although detected, only one of these return lights may be returned to the unit 1 and detected by the photodetector 5. In that case, it is necessary to provide a photodetector for detecting the remaining one return light and a beam splitter for making the optical paths of these return lights different. However, the laser diode 3 and the laser diode 4 are combined into one. The reduction in size and cost by housing in the can package CP and the reduction in projection area due to the fact that the optical paths of the lasers L1 and L2 immediately after emission substantially coincide are realized.
[0038]
In the above example, the present invention is applied to a two-wavelength compatible optical pickup that selectively uses a short wavelength laser for DVD and a laser for CD. However, two wavelengths that use two types of lasers in other combinations are used. The present invention may be applied to a compatible optical pickup.
Further, the present invention is not limited to the above-described embodiments, and various other configurations can be taken without departing from the gist of the present invention.
[0039]
【The invention's effect】
As described above, according to the two-wavelength compatible optical pickup according to the present invention, the laser light source that emits the first laser and the laser light source that emits the second laser are housed in the same single casing. Compared with the case where these laser light sources are housed in separate casings as in the prior art, it is possible to achieve downsizing and cost reduction by reducing the number of casings.
[0040]
As an example, the return light from the optical recording medium of the first laser and the return light from the optical recording medium of the second laser are both branched by the optical branching means in the same integrated unit. When detection is performed by the light detection means in the lever unit, further miniaturization and cost reduction can be realized from the following points.
[0041]
(1) Since one photodetecting means in the same unit is commonly used for reproduction of the optical recording medium by the first laser and reproduction of the optical recording medium by the second laser, 2 as in the prior art. There is no need to provide one light detection means.
[0042]
(2) Since the optical paths of the first laser and the second laser almost coincide with each other over the entire length, the role of matching the optical paths of these lasers and the optical path of the return light are made different as in the prior art. The beam splitter which plays a role becomes unnecessary.
[0043]
In addition, in this case, since the first and second lasers and the return light do not need to pass through the beam splitter, the optical path of the laser is shortened as compared with the case of passing through the beam splitter as in the prior art. (The projected area can be reduced).
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of a configuration of an integrated unit of an optical pickup according to the present invention.
2 is a diagram showing an example of the entire configuration of an optical pickup using the integrated unit of FIG. 1;
FIG. 3 is a perspective view showing another example of the configuration of the integrated unit of the optical pickup according to the present invention.
FIG. 4 is a diagram illustrating an example of the overall configuration of a conventional optical pickup.
FIG. 5 is a diagram showing another example of the overall configuration of a conventional optical pickup.
[Explanation of symbols]
1, 9, 11, 20 Integrated unit, 2 Photodiode IC, 3, 4, 16 Laser diode, 5, 19 Photo detector, 5a-5d sensor element, 6 Micro prism, 7 Hologram plate, 8 LOP, 12, 17 beam Splitter, 13 collimator lens, 14 45 degree mirror, 15 objective lens, 18 cylindrical lens

Claims (1)

In an optical pickup for reproducing an optical recording medium by selectively using a first laser and a second laser having different wavelengths,
A first laser light source that emits the first laser;
A second laser light source that emits the second laser;
A collimator lens that collimates the laser emitted from the first laser light source and the laser emitted from the second laser light source;
An objective lens for condensing the laser made into parallel light by the collimator lens on the optical recording medium;
Light branching means for branching the return light from the optical recording medium;
A light detecting means for detecting the return light branched by the light branching means,
The first laser light source and the second laser light source are arranged apart from each other by a distance within a range of about 200 to 500 μm and emit laser from the same direction,
Integrating the first laser light source, the second laser light source, the light branching means, and the light detecting means integrally;
Optical path synthesis having a function of transmitting a vertically incident laser between the objective lens and the collimator lens and tilting the obliquely incident laser so that the direction of the optical axis coincides with the vertically incident laser An optical pickup characterized in that an element is arranged.

Images