KR980011137A - Optical pick-up device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pick-up apparatus for simultaneously reproducing a digital audio disc (DAD) for general music reproduction and a digital video disc (DVD) for video and audio reproduction. A two-wavelength laser diode formed inside one side of the silicon substrate and radiating laser beams having different wavelengths at the same time; a support formed on the other side of the silicon substrate; Wavelength laser diode formed on the silicon substrate, a prism that transmits the laser beam, and a prism that is formed inside the prism and forms an incidence beam into three beams A polarizing beam splitter for reflecting the extraordinary rays of the three beams separated from the prism inner diffraction grating and separated from the prism inner diffraction grating and transmitting an upper light beam, a polarizing beam splitter formed on one side of the prism and reflected from the polarization beam splitter A holographic grating for focusing the returning beam and for irradiating with a photodetector, And a wavelength conversion and beam control plate which is formed on the surface of the disk to selectively transmit only a laser beam of a specific wavelength and to adjust a spot size of the optical information to be converted into an ideal light beam.

Description

The optical pickup device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pick-up apparatus for recording a signal on an optical data recording medium and reproducing the recorded information as an electric signal, And a video disk (DVD) can be played back at the same time.

2. Description of the Related Art In general, an optical pick-up apparatus for reproducing electric signals from information recorded in a digital audio disk (DAD) or a digital video disk (DVD) is provided with individual components such as an objective lens, a beam splitter, a diffraction grating, a laser diode, Assembly.

That is, as shown in FIG. 1, a structure of an optical pick-up device used in a digital audio disc generally includes a laser diode 51 for generating a laser beam, And diffraction gratings 52 for separating light into tracking error detection light are provided at predetermined intervals.

A beam split 53 is disposed on one side of the diffraction grating 52 to have a predetermined slope and has a constant ratio of reflectivity and transmittance to separate incident light into reflected light and transmitted light.

An objective lens 54 having a diffraction limit performance of a predetermined wavelength or less and condensing the separated light to focus information on the disk 55 and reading information recorded thereon is disposed at a predetermined interval And a photodetector 56 for converting the optical information recorded on the audio and video disk 55 through an objective lens 54 into a current is provided at a predetermined interval below the beam split 53 .

In the conventional optical pick-up apparatus having such a structure, first, a laser beam having a predetermined oscillation wavelength is emitted from the laser diode 51. As the laser beam passes through the diffraction grating 52, the focus and tracking error Three beams for detection (THREE BEAM: zero-order light and ± one-order light) are separated and emitted.

Therefore, the light separated by the diffraction grating 52 is emitted to the beam split 53 having a constant reflectance and transmittance to separate the incident light into the reflected light and the transmitted light, and the reflected light is separated by the objective lens 54 The beam is condensed at a diffraction limit performance of a predetermined wavelength or less and is sent on the audio or video disk 55 to focus on the disk 55 to read the information recorded on the disk 55. [

In other words, the objective lens 54 condenses light onto the signal surface of the disk 55 in the form of air having a size of several micrometers. The light is returned almost as it is without the pit 55a on which the data is recorded, The light is diffracted by the pit 55a and is emitted outside the range of the objective lens 54. As a result, only a part of the incident light is returned, thereby causing a light amount difference in the photodetector 56. [

On the other hand, the intensity of the light reflected and returned from the audio or video disk 55 is modulated by the pit 55a. The modulated light information is transmitted through the objective lens 54 and the beam split 53 to the photodetector 56, So that the audio signal recorded on the disk 55 can be reproduced by demodulating the converted current into an original signal by a digital signal processing unit (not shown).

Such a conventional optical pick-up apparatus reads only information recorded on one of a digital audio disk (DAD) and a digital video disk (DVD), and can not selectively read data recorded on two kinds of disks do.

The reason is that the data recording capacity of the digital video disk is four times as large as that of the digital audio disk, and the width of the pit is reduced to about half that of the digital audio disk, so that the spot size is also small Should be formed.

That is, when the spot size in the digital audio disk is 1.6 mu m in diameter and the spot size in the digital video disk is 0.8 mu m in diameter, audio and video data recorded on the disk can be accurately reproduced.

Therefore, since the conventional optical pick-up apparatus shown in FIG. 1 can form a spot size of only one of the diameter of 1.6 μm and the diameter of 0.8 μm, it is possible to selectively reproduce audio and digital video disks having different data recording systems There is no problem.

The present invention relates to a two-wavelength laser diode which emits two different wavelengths to a silicon substrate, a polarization beam splitter which transmits P-wave of an incident beam, S-wave reflects a prism, a diffraction grating which separates and irradiates an incident beam into three beams, A wavelength conversion and beam control plate for selectively converting only the laser beam of wavelength and controlling the spot size on the disk and converting the P wave into S wave, a holographic grating for diffracting optical information returning through the disk, When a laser beam of a specific wavelength passes through the wavelength conversion and beam control plate, a beam focus of diameters of 1.6 mu m and 0.8 mu m is formed on the disk at the same time, so that the data recording capacity of the digital audio disk, It is possible to reproduce a digital video disk in which the width of the pit is remarkably narrow, Thereby contributing to improvement in reliability.

That is, the present invention provides a method for manufacturing a semiconductor device, comprising: a silicon substrate on which a plurality of optical elements are placed; a two-wavelength laser diode which is formed inside one side of the silicon substrate and emits laser beams of first and second wavelengths, A photodetector formed at a predetermined position inside the support to convert the optical information of the disk into a current, a prism formed at a predetermined size on the silicon substrate on which the two-wavelength laser diode is formed and transmitting the laser beam, A diffraction grating formed in the prism so as to form a concavo-convex shape in a diagonal direction so as to separate the incident beam into three beams, an extraordinary ray of the three beams separated from the prism inner diffraction grating at a predetermined interval, A polarization beam splitter formed on one side of the prism and reflecting the beam reflected from the polarization beam splitter, A hologram grating formed on an upper surface of the prism for selectively transmitting only a laser beam of a specific wavelength and capable of adjusting a spot size for changing an upper ray of the optical information returned through the disk to an ideal ray; Conversion and beam control.

FIG. 1 is a block diagram of a conventional optical pick-up apparatus. FIG.

FIG. 2 is a configuration diagram of an optical pick-up apparatus according to the present invention; FIG.

DESCRIPTION OF THE REFERENCE NUMERALS

54: objective lens 55: disk

60: silicon substrate 61: support

62: photodetector 63: two-wavelength laser diode

64: diffraction grating 65: polarized beam split

66: prism 67: holographic grating

68: first transparent portion 69: second transparent portion

70: Wavelength conversion and beam control plate

Fig. 2 is a schematic view of the optical pick-up apparatus according to the present invention. In the optical pick-up apparatus according to the present invention, two wavelengths λ 1 and λ 2, which radiate beams of first and second wavelengths λ 1 and λ 2, A laser diode 63 is formed and a prism 66 transmitting a laser beam is formed in a predetermined size on the silicon substrate 60 on which the two-wavelength laser diode 63 is formed.

Here, the two-wavelength laser diode 63 uses a space-emission type laser diode in which a laser beam is emitted upward by P / N bonding.

A polarization beam splitter 65 for transmitting only the upper light beam (P wave) and reflecting the extraordinary light beam (S wave) to the laser beam radiated from the two-wavelength laser diode 63 is formed in the central portion of the prism 66 in the diagonal direction And a prism 66 on the lower side of the polarization beam splitter 65 is provided with a diffraction grating 64 of a concavo-convex shape for separating the laser beam radiated from the two-wavelength laser diode 63 into three beams of zero-order light and ± first- Is formed.

A hologram grating 67 is formed on one side of the prism 66 for diffracting the light information reflected from the disk 55 and irradiating the light to the photodetector 62. On the upper surface of the prism 66, A wavelength conversion and beam control plate 70 capable of selectively transmitting only the laser beam and adjusting the spot size on the disk 55 by reflecting the laser beam of the other wavelengths is formed.

Here, the configuration of the wavelength conversion and beam control plate 70 is the same as that of the first embodiment except that the first transmissive portion 68 (not shown) that transmits only the first wavelength lambda 1 emitted from the two-wavelength laser diode 63 and reflects the laser beam having the other wavelength A second wavelength? 2 emitted from the two-wavelength laser diode 50 is formed to have a predetermined size on the outer circumferential surface of the first transparent portion 68, and a laser beam of another wavelength is reflected And a second transparent portion 69.

A support body 61 integrally formed with a photodetector 62 for detecting optical information of the disk 55 is formed on the other side of the silicon substrate 60, And an objective lens 54 for forming a beam focus on the disk 55 is provided on the upper side.

In the present invention as described above, the two-wavelength laser diode 63 of the surface-emission type, which is formed at the central portion of one side of the silicon substrate 60 and emits the laser beam upward by the P / N junction, The laser beam of the first and second wavelengths lambda 1 and lambda 2 is simultaneously radiated and the laser beam of the wavelength is guided by the diffraction grating 64 formed inside the prism 66 to form the zero- And separated into three beams of ± 1-order light.

Therefore, this separated beam is irradiated by the polarization beam splitter 65, and only the upper light ray (P wave) included in the incident beam is transmitted, and the extraordinary ray (S wave) is reflected, And is irradiated to the beam control plate 70.

The laser beams of the first and second wavelengths lambda 1 and lambda 2 which are the phase beams (P waves) irradiated onto the wavelength conversion and beam control plate 70 are transmitted to the first and second transparent portions 68 and 69 And the information recorded on the digital audio disk (DAD) or the digital video disk (DVD) is read according to the beam path.

That is, the laser beam of the first wavelength? 1 transmitted through the polarization beam splitter 65 is focused at the angle of? 1 as it is irradiated to the objective lens 54 via only the first light projecting unit 68, The laser beam of the second wavelength lambda 2 transmitted through the polarization beam splitter 65 is irradiated to the objective lens 54 only through the second light projecting portion 69 2 and forms a beam focus on the disk 55. [0064]

Therefore, it is divided into two first and second numerical apertures NA1 (NA2) by the first and second transparent portions 68 and 69 of the wavelength conversion and beam control plate 70, The size of the beam formed on the disk 55 is changed, resulting in a difference in the amount of light.

Here, the numerical expression of the numerical aperture is as follows.

NA1 =? Sin? 1 (1)

, And NA2 =? Sin? 2.

(Where eta is the refractive index and eta in the air is 1.)

NA1 = Sin? 1 (2)

, And NA2 = Sin &thetas; 2.

D = K x lambda / NA, H = R x lambda / (NA) ² (3)

(Where D is the beam size, H is the depth of focus, and K and R are constants, respectively, the beam size and depth of focus change as the NA changes.

Therefore, the beam size and the depth of focus, which are transmitted through the first transparent portion 68 of the wavelength conversion and beam control plate 70 and converged at the angle &thetas; 1, are transmitted through the second transparent portion 69, Size and depth of focus (because the beam size is inversely proportional to NA and the depth of focus is inversely proportional to (NA) ² )

Therefore, the laser beam that has been transmitted through the first transparent portion 68 of the wavelength conversion and beam control plate 70 and focused by the objective lens 54 at the angle of &thetas; 1 is focused on the disk 55 with a beam spot having a size of 1.6 mu m The data recorded on the digital audio disk DAD having a longer length of the pit 55a is read and the data is transmitted through the second transparent portion 69 of the wavelength conversion and beam control plate 70 to the objective lens 54 The laser beam focused at the angle of? 2 is formed with a beam spot having a size of 0.8 mu m on the disk 55, thereby reading the data recorded on the digital video disk (DVD) having a narrower length of the pit 55a.

That is, the light is converged at the angles of? 1 and? 2 by the first and second transparent portions 68 and 69 and the objective lens 54 of the wavelength conversion and beam control plate 70, And the light is irradiated onto the signal surface of the digital video disk or the digital audio disk 55. This light returns almost as it is without the pit 55a where the data is recorded, Diffracted by the diffraction grating 55a and emitted out of the range of the objective lens 54. As a result, only a part of the incident light is returned, resulting in a light amount difference in the photodetector.

Assuming that the disc 55 is a digital audio disc in this state, the optical information of the digital audio disc, which is an upper ray (P wave) converging at the angle of? 1, is again incident on the objective lens 54 (S wave) by passing through the first transparent portion 68 of the wavelength conversion and beam regulating plate 70 and is irradiated to the polarization beam splitter 65. [

Therefore, the polarization beam splitter 65 reflects only the extraordinary ray (S wave) and transmits the upper ray (P wave) line to transmit the optical information of the reflected optical ray (P wave) And is converged by the hologram grating 67 formed on the support 61 to the photodetector 62 formed on the support 61.

On the other hand, assuming that the disk 55 is a digital audio disk, the optical information of the digital audio disk, which is the phase ray (P wave) focused on the angle of 2, (S wave) by passing through the second transparent portion 69 of the beam control plate 70 and irradiated to the polarization beam splitter 65.

At this time, the polarization beam splitter 65 reflects only the extraordinary ray (S wave) and transmits the upper ray (P wave) line so that the optical information of the reflected optical ray (P wave) And is converged by the hologram grating 67 formed on the support 61 to the photodetector 62 formed on the support 61.

Therefore, in the structure of the present invention, the focus error detection is detected by the Foucault method, and the tracking error detection is detected by the three beam method by the diffraction grating 64.

The photodetector 62 converts the optical information of the disk into a current and outputs an RF signal, a focus signal, and an RF signal by a digital signal processing unit (not shown) The audio signal recorded on the digital audio and video disc is reproduced by detecting and demodulating the tracking signal into the original signal.

In the present invention, when a laser beam of a specific wavelength passes through the wavelength conversion and beam control plate by integrating a two-wavelength laser diode, a polarization beam splitter, a diffraction grating, a wavelength conversion and a beam control plate, a holographic grating and a photodetector on a silicon substrate, And a beam focus of diameters of 1.6 mu m and 0.8 mu m are formed on the optical disk at the same time so that a digital video disk having a data recording capacity of several times larger than that of the audio disk and having a significantly narrower pit width can be reproduced, It is possible to contribute to the improvement of the reliability of the power-up device.

Claims (1)

A optical pick-up apparatus for condensing a beam with a laser beam as an objective lens to record a signal on a disk and reproduce the recorded information as an electric signal, comprising: a silicon substrate (60) on which a plurality of optical elements A two-wavelength laser diode 63 that is formed inside one side of the silicon substrate 60 and emits laser beams of first and second wavelengths having different wavelengths at the same time, a two-wavelength laser diode 63 which is formed on the other side of the silicon substrate 60, A photodetector 62 formed at a predetermined position in the support 61 for converting the optical information of the disk into a current and formed on the silicon substrate 60 on which the two-wavelength laser diode 63 is formed, A diffraction grating 64 formed in a shape of a concavo-convex shape in a diagonal direction inside the prism 66 so as to separate the incident beam into three beams, a prism 66 having an inner diffraction grating 64) A polarizing beam splitter 65 which reflects an extraordinary ray of the three separated beams and transmits an upper ray of light, a condensing lens 65 which is formed on one side of the prism 66 to focus a returning beam reflected from the polarization beam splitter 65, A hologram grating 67 for irradiating the laser beam to the detector 62, a prism 66 for selectively transmitting only a laser beam of a specific wavelength formed on the prism 66, And a wavelength conversion and beam control plate (70) capable of adjusting a spot size. ※ Note: It is disclosed by the contents of the first application.