KR100438732B1 - Slim optical pickup - Google Patents

Abstract

A collimating mirror disposed on an optical path between the objective lens and the optical path changing device, the collimating mirror having a reflective curved surface for reflecting the light incident from the light source toward the objective lens and converting the incident light into parallel light; A slim optical pickup is disclosed. According to the disclosed slim optical pickup, the distance between the collimating lens and the photodetector can be reduced by the thickness of the collimating lens and the distance between the collimating lens and the reflection mirror, compared to the conventional slim optical pickup. Accordingly, the disclosed slim optical pickup can be made smaller than the conventional slim optical pickup, so that the mechanical height and size of the portable optical player such as a laptop computer or a portable DVD player having a liquid crystal screen for image display such as a laptop computer can be obtained. This is very useful when applied to devices that are heavily constrained by).

In addition, since the collimating mirror functions as a collimating lens and a reflecting mirror, the number of parts can be reduced, the manufacturing cost can be reduced, and the bonding point of the adhesive used to bond the optical parts is reduced, so it is reliable at high temperature operation. This can be secured.

Description

Slim optical pickup

The present invention relates to an optical pickup, and more particularly, to a slim optical pickup capable of miniaturization and reducing the number of parts.

Since a notebook computer or a portable (for example, a portable DVD player having a liquid crystal screen for an image display such as a notebook computer) is highly restricted in mechanical height, a slim optical pickup is used.

In the general slim optical pickup, as shown in FIG. 1, the collimating lens 3 is disposed between the reflective mirror 5 and the plate-shaped beam splitter 8, which is an optical path changing device, so as to lower the mechanical height. (2) the light passing through the collimating lens (3) is reflected by the reflecting mirror (5) to bend the optical path by 90 degrees and to focus on the objective lens (7) to record the recording surface of the optical disc (1) The structure is formed so as to form a light spot on the image.

FIG. 1 shows an example in which two semiconductor laser pairs, also known as TWIN lasers, are provided as the light source 2 so as to make DVD and CD compatible. In FIG. 1, reference numeral 9 denotes an information signal and / or an error signal by receiving light reflected from an optical disk 1, that is, a thin optical disk 1a (for example, DVD) or a thick optical disk 1b (for example, CD). It is a photodetector for detecting.

On the other hand, a factor directly related to the optical pickup size is the focal length of the collimating lens. Therefore, when the focal length of the collimating lens is made small, the distance from the collimating lens to the photodetector may be reduced, thereby reducing the size of the optical pickup.

However, if the focal length of the collimating lens is made too small, the size of the light beam received by the photodetector decreases, thereby increasing the probability of the light escaping from the photodetector during high temperature operation.

Of course, even when the focal length of the collimating lens is reduced, if the thickness of the plate beam splitter is increased, the size of the light beam received by the photodetector can be increased, but the optical pickup is slim due to the increase in the size of the plate beam splitter. Hard to make

Alternatively, the collimating lens can be placed between the reflective mirror and the objective to make the optical length small. However, since a notebook computer, a portable computer, etc. requiring a slim optical pickup is thin, the distance between the reflective mirror and the objective lens should be very small. Therefore, in a slim optical pickup for application to notebook computers, portables, etc., it is impossible to put the collimating lens between the reflective mirror and the objective lens.

In the conventional slim optical pickup, as shown in FIG. 1, the collimating lens 3 is disposed between the reflective mirror 5 and the plate-shaped beam splitter 8.

However, in the conventional slim optical pickup, since the collimating lens 3 is disposed between the reflective mirror 5 and the plate-shaped beam splitter 8, there is a limit to miniaturization due to the above-described problems. It is difficult to respond properly.

The present invention has been made in order to improve the problems of the conventional slim optical pickup as described above, the object is to provide a slim optical pickup that can be reduced in size than the conventional slim optical pickup and the number of parts can be reduced. .

1 is a view schematically showing an example of a conventional slim optical pickup,

2 is a view schematically showing an optical configuration of a slim optical pickup according to a first embodiment of the present invention;

3 is a view showing a comparison between a slim type optical pickup and a slim type optical pickup according to a first embodiment of the present invention;

4 is a view schematically showing an optical configuration of a slim optical pickup according to a second embodiment of the present invention;

5 is a view schematically showing an optical configuration of a slim optical pickup according to a third embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10 ... optical disc 10a ... thin optical disc

10b ... thick optical discs 20,70

21,51 ... First light source 23,53 ... Second light source

21a, 51a ... first light 23a, 53a ... second light

33,55 ... plate-type beam splitter 40 ... collimating mirror

45 ... reflective surface 47 ... objective

49 ... photodetector 57 ... cubic beam splitter

Slim optical pickup according to the present invention for achieving the above object is a light source; An objective lens for focusing the light emitted from the light source to form a light spot on the recording medium; A photodetector for receiving information reflected from the recording medium to detect an information signal and / or an error signal; An optical path changing device for converting a traveling path of the light; A collimating mirror disposed on an optical path between the objective lens and the optical path changing device, the collimating mirror having a reflective curved surface for reflecting the light incident from the light source toward the objective lens and converting the incident light into parallel light; Characterized in that.

According to an aspect of the present invention, the light source has a structure in which first and second light sources emitting first and second light having different wavelengths are integrated, and employs a plurality of types of recording media having different thicknesses. I can do it.

The optical path changing device may be a plate type beam splitter.

According to another feature of the invention, the light source has a first and a second light source for emitting the first and second light of different wavelengths, the optical path conversion device, for converting the traveling path of the first light A first optical path changing device for; And a second optical path changing device for converting a traveling path of the second light.

The optical path changing device positioned near the objective lens among the first and second optical path changing devices may be a cubic beam splitter, and the optical path changing device positioned near the optical detector may be a plate beam splitter.

In the above description, the first light is light having a wavelength suitable for a DVD recording medium, and the second light is light having a wavelength suitable for a CD recording medium. It is desirable that at least some of the media be compatible.

According to another feature of the invention, the light source is a single light source, the optical path conversion device may be a plate-shaped beam splitter.

In the above, the reflective curved surface of the collimating mirror is preferably a total reflection coated concave reflective curved surface.

The slim optical pickup according to the present invention records and / or plays back at least some of the optical discs of the DVD series, or at least some of the optical discs of the DVD series and / or at least some of the optical discs of the CD series. And / or to a portable player that can play.

Hereinafter, exemplary embodiments of the slim optical pickup according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a view schematically showing an optical configuration of a slim optical pickup according to a first embodiment of the present invention.

Referring to FIG. 2, the slim type optical pickup according to the first exemplary embodiment of the present invention is capable of interchangeably employing a thin first optical disk 10a and a thick second optical disk 10b. A light source 20 for emitting the first and second lights 21a and 23a, an objective lens 47 for condensing the light emitted from the light source 20 to form an optical spot on the optical disc 10, An optical detector 49 for receiving the light reflected from the optical disk 10 to detect an information signal and / or an error signal, an optical path changing device for converting a traveling path of the light, an objective lens 47 and an optical path changing device It is configured to include a collimating mirror 40 disposed between.

In the first embodiment of the present invention, the light source 20 is integrated with the first and second light sources 21 and 23 emitting the first and second light 21a and 23a of different wavelengths. Made of structure. The light source 20 may include a TWIN laser. Here, the TWIN laser refers to a light source module in which two semiconductor lasers are packaged in a single package.

In the optical pickup according to the first embodiment of the present invention, an optical disk 10a that is thin, that is, an optical disk (hereinafter, DVD) of at least a portion of a DVD-based optical disk and a thick optical disk 10b, that is, a CD-based optical disk When at least some of the optical disks (hereinafter, referred to as CDs) are adopted to be compatible, any one of the first and second lights 21a and 23a is light having a wavelength suitable for DVD, for example, a wavelength of 650 nm. Light having a wavelength suitable for CD, for example, a wavelength of 780 nm.

The objective lens 47 is designed to minimize aberration when, for example, parallel light is incident.

As the optical path changing device, it is preferable to include a plate-type beam splitter 33 as shown in FIG.

The plate beam splitter 33 is disposed to be inclined 45 degrees with respect to the optical axis of the light emitted from the light source 20. The plate-shaped beam splitter 33 is preferably coated to have a transmittance of, for example, 50 ± 5% of the wavelength of the first and / or second lights 21a and 23a.

When the plate-type beam splitter 33 is provided as the optical path changing device, the plate-type beam splitter 33 which is inclined to the first and second lights 21a and 23a traveling toward the optical disc 10 is transmitted. In order not to include coma aberration generated, the light source 20 allows the first and second lights 21a and 23a emitted therefrom to be reflected from the plate-shaped beam splitter 33 to be directed toward the collimating mirror 40. It is preferred to be arranged.

When the optical path changing device includes the plate-shaped beam splitter 33 disposed to be inclined at 45 degrees with respect to the optical axis, the plate-shaped beam splitters are provided in the first and second lights 21a and 23a reflected from the optical disc 10. Astigmatism occurs as it passes through 33). Therefore, it is possible to detect the focus error signal by the astigmatism method without providing a lens or the like which separately generates astigmatism.

On the other hand, the slim optical pickup according to the first embodiment of the present invention and the slim optical pickup according to the second and third embodiments of the present invention to be described later, between the optical path conversion device and the photodetector 49, a collimating mirror ( It is preferable to provide a concave lens (not shown), namely, a yaw lens so as to increase the size of the light formed on the photodetector 49 in combination with 40). When the optical path changing device is provided with a plate-shaped beam splitter 33, and the light reflected from the optical disc 10 is allowed to pass through the plate-shaped beam splitter 33 and proceed toward the photodetector 49, the concave lens is a plate. It is preferable to be inclined opposite to the plate-shaped beam splitter 33 so as to remove the coma aberration generated in the first and second lights 21a and 23a while passing through the type-beam splitter 33.

The collimating mirror 40 is disposed on the optical path between the objective lens 47 and the plate-shaped beam splitter 33 which is an optical path changing device. The collimating mirror 40 is capable of performing both the collimating lens (3 in FIG. 1) and the reflection mirror (5 in FIG. 1) in the conventional slim optical pickup, and is incident from the light source 20 side. It is provided with a reflective curved surface 45 for reflecting the first and second light 21a, 23a to be directed toward the objective lens 47, and converts incident light into parallel light.

The reflective curved surface 45 of the collimating mirror 40 is a concave reflective curved surface that functions as a collimating lens and can bend the light path of the incident light by 90 degrees, and reflects the incident light by, for example, 97% or more. It is preferable that the transfer board is coated. In this case, the divergent light emitted from the light source 20 becomes parallel light while being reflected by the concave reflective curved surface 45 of the collimating mirror 40 and the optical path is bent 90 degrees to the objective lens 47.

The photodetector 49 receives the first and second lights 21a and 23a reflected from the recording surface of the optical disc 10 to detect information signals and / or error signals. As in this embodiment, the structure of the photodetector 49 suitable for the case of adopting DVD and CD compatible using the light source 20 of the TWIN laser structure is well known in the art, so the photodetector 49 is here. ) A detailed description of the structure is omitted.

In FIG. 2, reference numeral 31 denotes a grating for splitting the first and / or second light 23a emitted from the light source 20 into at least three lights to enable detection of a track error signal by a three-beam method.

For example, the slim optical pickup according to the first embodiment of the present invention is CD and DVD compatible, and the tracking error signal is detected by the phase difference detection method for the DVD, and the tracking error signal is detected by the 3-beam method for the CD. In this case, the grating 31 is provided to branch the CD light into the three beams among the first and second lights 21a and 23a.

As another example, when the slim optical pickup according to the first embodiment of the present invention is CD and DVD compatible, and the tracking error signal is detected by the 3-beam method for both DVD and CD, the grating 31 is The first and second lights 21a and 23a are provided to branch into three beams.

As shown in FIG. 3, the slim optical pickup according to the first embodiment of the present invention having the optical configuration as described above has a distance between the collimating mirror 40 and the photodetector 49 as compared to the conventional slim optical pickup. In the conventional slim optical pickup, the thickness of the collimating lens (3 of FIG. 1) and the distance between the collimating lens 3 and the reflective mirror (5 of FIG. 1) may be shortened.

In the conventional slim optical pickup, when the thickness of the collimating lens 3 is t _CL and the distance between the collimating lens 3 and the reflection mirror 5 is d, the slim type according to the first embodiment of the present invention In the optical pickup, the distance shortening amount Δ between the collimating mirror 40 and the photodetector 49 becomes t _CL + d.

Figure 3 is provided with a collimating mirror 40 as in the slim optical pickup according to the present invention, in order to show that the size of the slim optical pickup can be much smaller than conventional, collimating in the conventional slim optical pickup The focal length of the lens 3 and the focal length of the collimating mirror 40 in the slim optical pickup according to the first embodiment of the present invention are illustrated and compared in the same manner.

4 is a view schematically showing an optical configuration of a slim optical pickup according to a second embodiment of the present invention. Here, members having substantially the same functions as those in FIG. 2 are denoted by the same reference numerals, and repetitive descriptions are omitted.

The slim optical pickup according to the second exemplary embodiment of the present invention has a structure in which the first and second light sources 51 and 53 which emit the first and second light 51a and 53a having different wavelengths are separated. The optical path conversion device is characterized in that the first optical path conversion device for converting the traveling path of the first light (51a) and the second optical path conversion device for converting the traveling path of the second light (53a). Here, the first light source 51 and the first light 51a correspond to the first light source 21 and the first light 21a in the foregoing embodiment, and the second light source 53 and the second light 53a. ) Corresponds to the second light source 23 and the second light 23a in the foregoing embodiment.

4 shows a cubic beam splitter 57 as a first optical path changing device located near the objective lens 47, and a plate beam splitter as a second optical path converting device located near the photodetector 49 as shown in FIG. An example with 55 is shown.

FIG. 4 shows an example in which a detection lens 59 is further provided for enlarging the size of the light beam received by the photodetector 49 between the plate-type beam splitter 55 and the photodetector 49, which are second optical path conversion devices. Shows.

5 is a view schematically showing an optical configuration of a slim optical pickup according to a third embodiment of the present invention. Here, members having substantially the same functions as those in FIG. 2 are denoted by the same reference numerals, and repetitive descriptions are omitted.

As shown in FIG. 5, the slim optical pickup according to the present invention may include a single light source 70. When the slim optical pickup according to the third embodiment of the present invention is for DVD and / or CD including DVD, it is preferable that the light source 70 includes a semiconductor laser that emits light having a wavelength of 650 nm, for example. Do.

The slim optical pickup according to the third embodiment of the present invention as shown in FIG. 5 can be applied to recording and / or playing an optical disk of a single thickness, for example, a DVD or a CD. Further, the slim optical pickup according to the third embodiment of the present invention can be applied to recording and / or playing back a plurality of types of optical disks having different thicknesses, for example, DVDs and CDs.

Here, when the slim optical pickup according to the third embodiment of the present invention is for recording and / or reproducing a DVD, and the tracking error signal is detected by the phase difference detection method, the grating 31 is removed in FIG.

The slim optical pickup according to the present invention as described above may be applied to a slim optical pickup such as a portable computer for a portable computer such as a laptop computer or a portable player for a DVD having a liquid crystal screen for an image display such as a laptop computer. Here, the portable player for DVD records and / or plays back at least some of the optical discs of the DVD series, or at least some optical discs of the DVD series and / or at least some optical discs of the CD series. Or means a portable player that can be played.

In the slim optical pickup according to the embodiments of the present invention described above, either a light source of the first light source 21, 51 or the second light source 23, 53 or the light source 70 is formed of a blue violet wavelength. A semiconductor laser that emits light having a wavelength of 405 nm may be applied to record and / or reproduce a plurality of types of optical discs including a next-generation DVD having a recording capacity higher than DVD, for example, 20 GB or more, or the next-generation DVD.

In the above, a detailed optical configuration of the slim optical pickup according to the present invention has been described with reference to the drawings, but the optical configuration of the slim optical pickup according to the present invention is not limited to the above-described embodiments. That is, in the slim optical pickup according to the present invention, the optical configuration other than the collimating mirror 40 which serves as a function of the collimating lens and the reflecting mirror may be variously modified.

Therefore, the true technical protection scope of the slim optical pickup according to the present invention should be determined by the technical spirit of the claims.

According to the present invention as described above, since it has a collimating mirror which serves to function as a collimating lens and a reflecting mirror, the thickness of the collimating lens and the distance between the collimating lens and the reflecting mirror as compared to the conventional slim optical pickup. As a result, the distance between the collimating mirror and the photodetector can be reduced.

Therefore, the slim optical pickup according to the present invention can be miniaturized than the conventional slim optical pickup.

Accordingly, the slim optical pickup according to the present invention may be applied to a device that is highly restricted in mechanical height and size, such as a portable computer such as a laptop computer or a portable DVD player having a liquid crystal screen for image display such as a laptop computer. Greatly useful in application

In addition, in the slim optical pickup according to the present invention, since the collimating mirror also functions as the collimating lens and the reflecting mirror, the number of parts can be reduced, the manufacturing cost can be reduced, and the adhesive used for bonding the optical parts As the bonding point is reduced, reliability in high temperature operation can be ensured.

Claims (10)

A light source; An objective lens for focusing the light emitted from the light source to form a light spot on the recording medium; A photodetector for receiving information reflected from the recording medium to detect an information signal and / or an error signal; An optical path changing device for converting a traveling path of the light; A collimating mirror disposed on an optical path between the objective lens and the optical path changing device, the collimating mirror having a reflective curved surface for reflecting the light incident from the light source toward the objective lens and converting the incident light into parallel light; Slim optical pickup characterized in that. 2. The light source of claim 1, wherein the light source has a structure in which first and second light sources emitting first and second light having different wavelengths are integrated, and a plurality of types of recording media having different thicknesses can be used interchangeably. Slim optical pickup characterized in that it is. The slim optical pickup according to claim 2, wherein the optical path changing device is a plate type beam splitter. The method of claim 1, wherein the light source, First and second light sources emitting first and second light having different wavelengths, The optical path conversion device, A first optical path changing device for converting a traveling path of the first light; And a second optical path changing device for converting a traveling path of the second light. 5. The optical path changing device of claim 4, wherein the optical path changing device located near the objective lens among the first and second optical path changing devices is a cubic beam splitter, and the optical path changing device located near the photodetector is a plate beam splitter. Slim optical pickup characterized by. 6. The DVD light according to any one of claims 2 to 5, wherein the first light is light of a wavelength suitable for a DVD-based recording medium, and the second light is light of a wavelength suitable for a CD-based recording medium. At least a portion of the recording medium and at least a portion of the recording medium of the CD series of the slim optical pickup, characterized in that it can be adopted. 7. The slim optical pickup of claim 6, wherein the reflective curved surface of the collimating mirror is a total reflection coated concave curved surface. The slim optical pickup according to claim 1, wherein the light source is a single light source, and the optical path changing device is a plate type beam splitter. The slim optical pickup according to any one of claims 1 to 5 and 8, wherein the reflective curved surface of the collimating mirror is a total reflection coated concave reflective curved surface. The optical disc of claim 1, wherein at least some optical discs of the DVD-based optical disc are recorded and / or played back, or at least some optical discs and / or CD-based optical discs of the DVD-based optical disc. A slim optical pickup, characterized in that it is applied to a portable player capable of recording and / or playing back at least some optical disks.