JP4584382B2 - Optical pickup device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup device used for an optical disk device, an optical card device, an optical tape device, and the like.
[0002]
[Prior art]
As an optical pickup device mounted on an optical disc apparatus in order to enable reproduction of information on both a DVD (digital video disc) and a CD (compact disc), a short wavelength laser for DVD (laser having a wavelength of about 650 nm), 2. Description of the Related Art There is known a two-wavelength optical pickup device that reproduces information from a DVD or CD as an optical disk by using two types of lasers, a CD laser (laser having a wavelength of about 780 nm).
[0003]
In this two-wavelength optical pickup device, an example in which two lasers having different wavelengths, a hologram, and a light receiving element are integrated among components for reproducing information from each of a DVD and a CD is disclosed in Japanese Patent Application Laid-Open No. 11-149652. It is described in the publication. FIG. 2 shows an example of an optical pickup device using a two-wavelength integrated unit as described in Japanese Patent Laid-Open No. 11-149652.
[0004]
In FIG. 2, the two-wavelength integrated unit 1 includes a CD laser 2, a DVD short wavelength laser 3, a hologram (not shown), a light receiving element, and the like. The light beam from the CD laser 2 becomes substantially parallel light by the collimator lens 4, is reflected by the mirror 5, and is irradiated to the CD (not shown) by the objective lens 6. On the other hand, the light flux from the short wavelength laser 3 for DVD becomes substantially parallel light by the collimating lens 4, is reflected by the mirror 5, and is irradiated to the DVD (not shown) by the objective lens 6.
[0005]
[Problems to be solved by the invention]
In the optical pickup device as shown in FIG. 2, the light emission points of the CD laser 2 and the DVD short wavelength laser 3 are physically separated from each other, so the CD laser 2 and the DVD short wavelength laser 3 are separated. The optical axis of each luminous flux from the side has an angle. For example, when the distance between the light emitting points of the CD laser 2 and the DVD short wavelength laser 3 is 0.5 mm and the focal length of the collimating lens 4 is 15 mm, the CD laser 2 and the DVD short wavelength laser 3 are short. Assuming that the angle between the optical axes of the light beams from the wavelength laser 3 is θ, θ = 1.9 ° from SINθ = 0.5 / 15.
[0006]
That is, when the light beam from the CD laser 2 is incident on the collimating lens 4 and the objective lens 6 at 0 °, the light beam from the short wavelength laser 3 for DVD is 1.9 ° on the collimating lens 4 and the objective lens 6. Incidence occurs, and in particular, a large aberration occurs in the objective lens 6. Further, the light flux from the short wavelength laser 3 for DVD may be greatly deviated from the center of the objective lens 6, and light may not enter the entire objective lens 6. Further, the mirror 5 and the objective lens 6 are shifted upward by, for example, d with respect to the two-wavelength integrated unit 1, which is an obstacle to thinning the optical pickup device.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup device that can improve a problem caused by an optical axis angle difference between light beams from lasers and that can use an inexpensive grating.
[0008]
An object of the present invention is to provide an optical pickup device capable of improving the light utilization efficiency.
An object of this invention is to provide the optical pick-up apparatus which can be made thin.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, laser light having different wavelengths from a plurality of adjacent light emitting points is made substantially parallel light by a single collimating lens, and the substantially parallel light is grating (or hologram). And an optical pickup device that forms a minute spot on an optical information recording medium via a mirror and an objective lens, and the single collimating lens and the grating (or hologram) And the pitch and angle of incidence of the grating ( or hologram ) so as to be incident substantially perpendicularly on the objective lens after passing through the mirror, the distance between the grating ( or hologram ) and the collimating lens, wherein the distance between the collimating lens and the plurality of light emitting points coli The focal length of Torenzu, diffraction directions of light by the grating (or a hologram) is what is the direction away from the objective lens.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 shows the exemplary embodiment of the present invention. 2 wave length corresponding integrated unit 1 includes a laser 2 and short-wavelength laser 3 and an unillustrated hologram for DVD for CD, and a light receiving element or the like. The light beam from the CD laser 2 becomes substantially parallel light by the collimating lens 4, is diffracted by the grating (or hologram) 7, is reflected by the mirror 5, and is irradiated to a CD as an optical information recording medium (not shown) by the objective lens 6. As a result, a minute spot is formed on the CD. The reflected light from the CD passes through the objective lens 6, the mirror 5, the grating (or hologram) 7, and the collimating lens 4, and then the 0th order light, the + 1st order light, and the −1st order light by the hologram in the two-wavelength integrated unit 1. The signal processing system processes a signal from each light receiving unit to detect a reproduction signal, a tracking error signal, and a focus error signal. In this way, information is recorded on the CD by irradiation with a light beam modulated with information from the CD laser 2, and the signal processing system detects the reproduction signal and reproduces the recorded information on the CD.
[0014]
On the other hand, the light beam from the DVD short wavelength laser 3 becomes substantially parallel light by the collimating lens 4, is diffracted by the grating (or hologram) 7, is reflected by the mirror 5, and is irradiated to the DVD (not shown) by the objective lens 6. . The reflected light from the DVD passes through the objective lens 6, the mirror 5, the grating (or hologram) 7, and the collimating lens 4, and then the 0th order light, the + 1st order light, and the −1st order light by the hologram in the two-wavelength integrated unit 1. The signal processing system processes a signal from each light receiving unit to detect a reproduction signal, a tracking error signal, and a focus error signal. Thus, information is recorded on the DVD by irradiation with a light beam modulated with information from the DVD short wavelength laser 3, and the signal processing system detects the reproduction signal and reproduces the recorded information on the DVD.
[0015]
Here, for example, the wavelength of the laser 2 for CD is 780 nm, the wavelength of the short wavelength laser 3 for DVD is 650 nm, and the distance between the light emitting points of the laser 2 for CD and the short wavelength laser 3 for DVD is 0.5 mm. When the focal length of the collimating lens 4 is 15 mm and the pitch P of the grating (or hologram) 7 is 5.4 μm, the light beam from the CD laser 2 is incident on the collimating lens 4 at 0 °, and the grating (or hologram) ) Is incident on 7 at 45 °.
[0016]
Since the angle at which the light beam enters the grating (or hologram) 7 is α, the first-order diffraction angle of the grating (or hologram) 7 is β, and the wavelength of the light beam is λ, P (SINα−SINβ) = λ. The light beam from the laser 2 has an emission angle (first-order diffraction angle β) of the grating (or hologram) 7 of 34.3 °.
[0017]
On the other hand, the light flux from the short wavelength laser 3 for DVD enters the collimating lens 4 at 1.9 ° and enters the grating (or hologram) 7 at 43.1 °. The exit angle (first-order diffraction angle β) of the grating (or hologram) 7 of the light beam from the short wavelength laser 3 for DVD is 34.3 ° from P (SINα−SINβ) = λ, and from the laser 2 for CD It becomes the same as the luminous flux. That is, by appropriately selecting the angle of the mirror 5, it is possible to cause both the light beam from the CD laser 2 and the light beam from the DVD short wavelength laser 3 to enter the objective lens 6 perpendicularly.
[0018]
Further, in the optical pickup device shown in FIG. 2, the mirror 5 and the objective lens 6 are shifted upward by, for example, d with respect to the two-wavelength integrated unit 1. However, in this reference example, it is possible to shift the light beam downward by the grating (or hologram) 7 (the diffraction direction of the light by the grating or hologram 7 is the direction away from the objective lens 6). By appropriately setting the distance from the grating (or hologram) 7, the mirror 5 and the objective lens 6 can be shifted downward by d to reduce the thickness.
[0019]
According to this reference example , laser beams having different wavelengths from a plurality of adjacent light emitting points are made into substantially parallel light by the collimator lens 4, and a CD or DVD as an optical information recording medium is passed through the objective lens 6 by this substantially parallel light. In the optical pickup device that forms a minute spot on the optical pickup device, the optical pickup device includes a grating or a hologram 7 that makes laser beams having different wavelengths from the plurality of light emitting points incident on the objective lens 6 substantially perpendicularly. It is possible to improve a defect (aberration caused by light obliquely entering the objective lens) caused by the optical axis angle difference between the bundles.
[0020]
According to this reference example , since the grating or hologram 7 is arranged between the collimating lens 4 and the objective lens 6, it is possible to use an inexpensive grating or hologram.
[0021]
Furthermore, according to this reference example , since the diffraction direction of the light by the grating or the hologram 7 is a direction away from the objective lens 6, a thin optical pickup device can be realized.
[0022]
In this reference example , the grating (or hologram) 7 is arranged between the collimating lens 4 and the mirror 5, but the grating (or hologram) 7 is arranged between the collimating lens 4 and the two-wavelength integrated unit 1. May be.
[0023]
3 shows the embodiment of the present invention. 3, the intensity center of the laser beam is indicated by a broken line. In this embodiment, when the focal length of the collimating lens 4 (the distance between the collimating lens 4 and the light emitting point of the CD laser 2 and the DVD short wavelength laser 3) is f in the reference example , the grating (or The distance between the hologram 7) and the collimating lens 4 is f, so that the intensity center of the light beam from the CD laser 2 and the intensity center of the light beam from the short wavelength laser 3 for DVD are matched. .
[0024]
According to this embodiment, the distance between the grating or hologram 7 and the collimating lens 4 and the distance between the collimating lens 4 and the light emitting points of the CD laser 2 and the DVD short wavelength laser 3 are substantially the same. It is possible to improve the light utilization efficiency.
[0025]
The present invention is not limited to the above-described embodiments, and can be applied to an optical pickup device used in an optical disk device, an optical card device, an optical tape device, and the like.
[0026]
【The invention's effect】
As described above, according to the present invention , it is possible to improve the problem caused by the optical axis angle difference between the light beams from the lasers, and it is possible to use an inexpensive grating or hologram.
Further, according to the present invention, it is possible to improve the light utilization efficiency, it is possible to realize a thin optical pickup apparatus.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a reference example of the present invention.
FIG. 2 is a schematic view showing a conventional optical pickup device.
FIG. 3 is a schematic view showing an embodiment of the present invention.
[Explanation of symbols]
1 2 wavelength integrated unit 2 CD laser 3 DVD short wavelength laser 4 collimating lens 5 mirror 6 objective lens 7 grating (or hologram)

Claims (1)

Laser light having different wavelengths from a plurality of adjacent light emitting points is made into substantially parallel light by a single collimating lens, and this substantially parallel light is minutely applied to an optical information recording medium via a grating (or hologram), a mirror, and an objective lens. In an optical pickup device that forms a simple spot, laser beams having different wavelengths from the plurality of light emitting points are emitted.
Set the pitch and incident angle of the single collimating lens and the grating (or a hologram) and the grating so as to be incident substantially perpendicular to <br/> the objective lens after passing through the mirror (or hologram),
The distance between the grating ( or hologram ) and the collimating lens, and the distance between the collimating lens and the plurality of light emitting points are the focal lengths of the collimating lens, and the diffraction direction of light by the grating ( or hologram ) is An optical pickup device characterized by being in a direction away from the objective lens.

Images