KR100224893B1 - Comkpoible optical pickup apparatus - Google Patents

Abstract

A compatible optical pickup apparatus capable of interchangeably employing disks having different thicknesses is disclosed.

The compatible optical pickup apparatus is located between a light source for generating and emitting light, first and second objective lenses for converging incident light so that light spots are formed on the recording surface of the disc, and between the light source and the first and second objective lenses. First and second optical units for converting the advancing path of incident light, and first and second photodetectors for receiving light reflected from the disk and passing through the first and second objective lenses, respectively; It includes a first beam splitter for converting the traveling path of the incident light, and a first diffractive optical means coupled to the first objective lens side of the first beam splitter to diffract the incident light reflected from the disk, the second optical The unit includes a second beam splitter positioned on an optical path between the first beam splitter and the second objective lens to convert a traveling path of light, and light coupled to the second objective lens side of the second beam splitter and reflected from the disk. Diffract It includes a second diffractive optical lock means, the is characterized in that in the first and the second optical unit integrally.

Description

Compatible optical pickup apparatus

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compatible optical pickup apparatus, and more particularly, to a compatible optical pickup apparatus capable of employing compatible disk-type recording media having different thicknesses.

In general, an optical pickup device is employed in a compact disc player (CDP), digital video disc player (DVDP), CD-ROM drive, DVD-ROM drive, etc. and is mounted on a spindle motor to record information in a non-contact manner on a recording surface of a disc that rotates at high speed Or play back the recorded information.

DVDP and DVD-ROM are attracting attention in the field of video sound as a device capable of high-density recording and reproducing. The optical pickup device employed in this DVDP is not only a digital video disc (DVD) but also a compact disc (CD), CD-R (Recordable), CD-I, CD-G, etc. In the case of hiring, it should be possible to record and / or reproduce information.

However, the thickness of the DVD has been standardized to a different specification from the thickness of the CD family due to mechanical disc tilt tolerance and objective lens numerical aperture. In other words, the thickness of the existing CD pannily is 1.2mm, while the DVD is 0.6mm. As described above, since the thicknesses of the CD family and the DVD are different from each other, spherical aberration due to the difference in thickness occurs when the optical pickup device for DVD is applied to the CD family. This spherical aberration causes a problem of failing to obtain sufficient light intensity for recording the information signal or deterioration of the signal during reproduction.

Due to such a difference in standardization, recording of information on a DVD and reproduction of recorded information are impossible with a normal CDP.

Accordingly, in order to overcome the aforementioned points, a disc compatible optical pickup device having a different port format as shown in FIG. 1 has been disclosed.

1 is a view showing an optical arrangement of a conventional compatible optical pickup device.

As shown, the compatible optical pickup apparatus includes a light source 11 for generating and emitting light, an objective lens 19 for converging incident light so that an optical spot is formed on the recording surface of the disk 10, and the light source 11. A beam splitter 15 positioned on an optical path between the objective lens 19 and the optical path, and a hologram element positioned on an optical path between the objective lens 19 and the beam splitter 15; 17) and a photodetector 23 for detecting an error signal and an information signal.

The beam splitter 15 passes mostly the light 1 incident from the light source 11 toward the straight line, and reflects the light incident from the objective lens 19 toward the photodetector 23. The hologram element 17 diffracts incident light into zero order light 3 and +1 order light 5. The zero order light 3 is generally straight with respect to the incident light, and the + first order light 5 diverges. Therefore, the zero order light 3 and the +1 order light 5 form a focus at different positions. The zero shielding 3 is used for a thin disk, i.e., DVD 10b, and the + primary shield 5 is used for a relatively thick disk, i.e., CD 10a. The photodetector 23 receives the light reflected from the recording surface of the optical disc 10 to detect an RF information signal and an error signal. The collimating lens 13 is provided between the beam splitter 15 and the hologram element 17 to convert the incident divergent light into parallel light.

The compatible optical pickup device further includes a diffraction grating 25 between the light source 11 and the beam splitter 15. The diffraction grating 25 diffracts incident light into zero order diffraction light, ± first order diffraction light, and the like so that the photodetector 23 can detect the track error signal by the three beam method. The compatible optical pickup apparatus further includes an astigmatism lens 21 between the beam splitter 15 and the photodetector 23 so as to detect the focus error signal by the astigmatism method in the photodetector 23.

In the compatible optical pickup device configured as described above, since light is divided by the hologram element 17, the light efficiency is low, and thus sufficient light intensity during high density recording is difficult to obtain. In addition, optical alignment is difficult because astigmatism lenses are used to detect focus error signals using astigmatism.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described disadvantages, and an object thereof is to provide a compatible optical pickup device in which the first and second optical units are integrally formed to facilitate optical alignment.

1 is a view showing an optical arrangement of a conventional compatible optical pickup device.

2 is a schematic view showing an optical arrangement of a compatible optical pickup device according to an embodiment of the present invention.

3 schematically shows an example of the first and second diffractive optical means according to the invention;

Explanation of symbols for main parts of the drawings

100 1st optical unit 111 Light source

115 The first beam splitter 117 The first diffractive optical means

119 The first objective lens 123 The first photodetector

125 ... Diffraction grating 200 ... 2nd optical unit

215 2nd beam splitter 217 2nd optical diffraction means

219 ... second objective lens 223 ... second photodetector

In order to achieve the above object, the compatible optical pickup device of the present invention comprises a light source for generating and emitting light; First and second objective lenses for converging incident light so that light spots are formed on the recording surface of the disc; First and second optical units positioned between the light source and the first and second objective lenses to convert an advancing path of incident light; A first and second photodetectors for reflecting light from the disk and receiving light through the first and second objective lenses, respectively, wherein the first optical unit is configured to propagate incident light. A first beam splitter for converting a path; A first diffractive optical means coupled to the first objective lens side of the first beam splitter to diffract the light reflected from the disk and incident, wherein the second optical unit comprises the first beam splitter and the first optical lens; A second beam splitter positioned on an optical path between the second objective lenses and converting a traveling path of light; And second diffractive optical means coupled to the second objective lens side of the second beam splitter to diffract the incident light reflected from the disk, wherein the first and second optical units are integrated. It is done.

Hereinafter, a compatible optical pickup apparatus according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 is a view schematically showing an optical arrangement of a compatible optical pickup device according to an embodiment of the present invention.

As shown, the compatible optical pickup apparatus includes a light source 111 for generating and emitting light, and first and second objective lenses 119 and 219 for converging incident light to form an optical spot on the recording surface of the disk 110. ), First and second optical units 100 and 200 for converting optical paths, and first and second photodetectors 123 and 223 for detecting error signals and information signals.

Here, the first and second optical units 100 and 200 are integrally provided.

The first and second objective lenses 119 and 219 converge the incident light to form light spots on the recording surface of the disc 110. Each of the objective lenses 119 and 219 is provided with different focal lengths so that the disks 110a and 110b having different thicknesses can be compatible with each other.

The first optical unit 100 is positioned between the light source 111 and the first objective lens 119 and includes a first beam splitter 115 and a first beam splitter 115 for converting a traveling path of incident light. It comprises a first diffractive optical means 117 coupled to the first objective lens 119 of the.

The second optical unit 200 is positioned between the first beam splitter 115 and the second objective lens 219 to convert a traveling path of incident light, and the second beam splitter. And second diffractive optical means 217 coupled to the second objective lens 219 side of 215.

The first beam splitter 115 transmits part of the light incident from the light source 111 and reflects the rest. The transmitted light is converged by the first objective lens 119 and condensed on the recording surface 110a on the disk 110. The light reflected by the first beam splitter 115 is incident on the second beam splitter 215, and the second beam splitter 215 reflects the incident light toward the second objective lens 219. The second objective lens 219 focuses the incident light so that a light spot is formed on the recording surface 110b on the disk 110.

Each of the first and second photodetectors 123 and 223 is reflected by the disk 110 and is connected to the first objective lens 119, the first optical unit 100, and the second objective lens 219. By receiving the light incident through the second optical unit 200 and converting the light into an electric signal, an error signal and an information signal of the disc 110 are detected. The photodetectors 123 and 223 include a plurality of dividers each capable of receiving light independently so that information and error signals can be detected by differential and summation.

Each of the first and second diffractive optical means 117 and 217 is a diffractive optical element for transmitting light incident from the light source 111 and diffracting the light reflected from the disk 110, eg For example, as shown in FIG. 3, the first and second hologram elements 118 and 218 are provided. The first hologram element 118 is formed of at least two regions 118a and 118b having different diffraction, and the two regions 118a and 118b are divided by a band 119 to prevent light from being transmitted. In addition, the second hologram element 218 is also formed of at least two regions 218a and 218b having different diffraction effects, and similarly, the two regions 218a and 218b are also formed of a band 219 in which light is not transmitted. Are distinguished. Here, the first and second hologram elements 118 and 218 are preferably provided on a single substrate.

The first diffractive optical means 117 diffracts the light incident from the disk 110 and changes the optical path so that the diffracted light is directed to the first photodetector 123. Here, the focus error signal can be detected by using the diffracted light by the first and second diffractive optical means 117 and 217.

In addition, in the compatible optical pickup device of the present invention, the diffraction grating 125 is further provided between the light source 111 and the first beam splitter 115. The diffraction grating 125 diffracts incident light and diffracts it into a zero-order diffraction light, a + -first diffraction light, and the like. Thereby, the track error signal can be detected by the three beam method.

The light emitted from the light source 111 of the compatible optical pickup device provided in this way and transmitted through the first beam splitter 115 is focused on the first objective lens 119 to have a thick disk, for example, a recording surface of a CD ( Focus on 110a). The light reflected by the first beam splitter 115 is focused on the second objective lens 219 via the second beam splitter 215 and is formed on a recording surface 110b of a thin disk, for example, a DVD. Focus on.

Accordingly, the compatible optical pickup apparatus of the present invention has good light efficiency since light is not divided by diffraction optical means. In addition to using the diffractive optical means for detecting the focus error signal, the first and second optical units are integrally provided to facilitate optical alignment.

Although the present invention has been described with reference to the embodiments shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the claims.

Claims (3)

A light source for generating and emitting light; First and second objective lenses for converging incident light so that light spots are formed on the recording surface of the disc; First and second optical units positioned between the light source and the first and second objective lenses to convert an advancing path of incident light; A first and second photodetectors for reflecting light from the disk and receiving light through the first and second objective lenses, respectively. The first optical unit includes a first beam splitter for converting a traveling path of incident light; A first diffractive optical means coupled to the first objective lens side of the first beam splitter to diffract the light reflected and incident from the disk; The second optical unit includes: a second beam splitter positioned on an optical path between the first beam splitter and the second objective lens to convert a propagation path of light; And second diffractive optical means coupled to the second objective lens side of the second beam splitter to diffract the incident light reflected from the disk. And the first and second optical units are integrated, and the focal lengths of the first and second objective lenses are different from each other. The compatible optical pickup apparatus of claim 1, wherein each of the first and second diffractive optical means is formed into at least two regions having different diffraction to detect a focus error signal. The compatible optical pickup apparatus of claim 1, further comprising a diffraction grating diffracting incident light between the light source and the first beam splitter to divide the light into multiple pieces.