KR19980078467A - CD-DVD combined optical pickup - Google Patents

Abstract

The present invention provides a CD and DVD by varying the spherical aberration of the laser light incident on the objective lens by installing a width adjusting plate for selectively adjusting the widths of the FIFA and ESPA in the path before the laser light irradiated from the laser diode is incident on the objective lens. A CD-DVD combined optical pickup device for selectively reproducing.

The present invention includes a hologram element 10 in which a laser diode 12 for irradiating laser light and a photodiode 18 for converting light reflected from the pit of the CD 52 and the DVD 50 into electric signals are embedded; A collimated lens 20 installed at an upper side of the hologram element 10 to straighten the laser light emitted in parallel; A width adjusting plate 30 disposed above the collimating lens 20 to reflect a predetermined wavelength of the laser light and transmit another predetermined wavelength; A hologram optical lens 42 is provided on the upper side of the wide adjustment plate 30 to correct spherical aberration of the laser light on the center bottom surface, and focuses the laser light on the pit of the CD 52 and the DVD 50 on the upper side. It consists of a dual focus lens 40 having an objective lens 44 for the purpose.

The present invention has an effect of improving the productivity by reducing the manufacturing cost and manufacturing process of the optical pickup device by using a wide control plate 30 that is easy to manufacture.

Description

CD-DVD combined optical pickup

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CD-DV optical pickup device. In particular, a wide-adjustment plate for selectively adjusting the widths of FIFA and ESPA is installed in the path before the laser light irradiated from the laser diode is incident on the objective lens. The present invention relates to a CD-DVD combined optical pickup device for selectively reproducing CDs and DVDs with different spherical aberrations.

In general, optical data recording media are divided into CDs for music playback with a thickness of 1.2 mm and DVDs for sound and video playback with thicknesses of 0.6 mm. CDs record data in double layers on one side and DVDs in double layers in the middle. By recording, a large amount of data is recorded on one disk. In the optical pickup apparatus for reproducing data recorded on the above two types of discs, when reading information recorded on a 1.2 mm thick CD and a 0.6 mm thick digital video disc, the DVD has a track pitch on the disc for higher recording density. Since the track pitch is 1.6 µm and the shortest length between the feet is 0.834 µm, it is different from the CD recorded with 0.74 µm and the shortest length between the feet is 0.4 µm. Since the discrepancies cannot be simultaneously played back, and the optical aberration is increased due to the difference in the thicknesses of the discs, the noise increases and the error occurrence rate is increased. Therefore, the recorded information cannot be read correctly. Therefore, the optical pickup device is a 0.6mm or 1.2mm disc. Only one of the record information was to be read.

As a result, the holographic optical lens and the objective lens can focus on two different spots on the disc by correcting mutual spherical aberration so as to selectively read information recorded on a CD having a thickness of 1.2 mm and a DVD having a thickness of 0.6 mm at the same time. An optical pickup device using a combination of CD and DVD has been developed.

As shown in FIG. 1, the conventional optical pickup apparatus of the CD-DVD combined optical pickup apparatus has a laser diode (a) for generating divergent laser light, and is provided above the laser diode (a). A diffraction grating (b) for separating incident laser light into three beams of zero-order and ± first-order diffracted light using a diffraction phenomenon, and is provided on one side of the diffraction grating (b) and has a predetermined slope. And a beam splitter (c) which transmits and reflects a part of the incident laser light and reflects all of the reflected light at a predetermined angle, and a collie which is installed above the beam splitter (c) so that the transmitted laser light proceeds in parallel. The hologram to read the recorded information by focusing on the DVD and the CD by focusing on the mate lens d and the collimated lens d, and collecting linear laser light. Astigmatism for generating astigmatism for detection of focus errors in dual focus lenses (g) in which optical lenses (e) and objective lenses (f) are arranged in combination, and laser light reflected along with information from the CDs and DVDs And a photodetector 1 for detecting the light information passing through the astigmatism generating lens k and converting it into an electrical signal.

The operation of the conventional optical pickup device having such a configuration is first, the laser light irradiated from the laser diode (a) having a predetermined oscillation wavelength is diffused into the diffraction grating (b), the laser light is a diffraction grating (b) ) And split into zero-order and ± first-order light, that is, three beams, and continue to diffuse upward. This three-beam is used for focusing and tracking errors. The three-beams penetrate the diffraction grating b, enter the beam splitter c, and are reflected and transmitted at a constant rate. The laser beam transmitted through the beam splitter (c) enters the collimated lens (d) and passes through it, and goes straight in parallel. Then, the laser light is incident on the holographic optical lens (e) of the dual focus lens (g), whereby optical spherical aberration is increased. It is corrected and diffracted at the same time. The diffracted laser light is incident from the hologram optical lens (e) to the objective lens (f), and the diffracted laser light is collected by the objective lens (f) to have a DVD (h) of 0.6 mm and a CD (i) of 1.2 mm (i). ) Are collected in different airy shapes with diameters of 1.6 μm and 0.8 μm, respectively, and are irradiated to the pits of the DVD or CD, and the laser light is reflected almost as it is in the absence of the pits on the disc. Returning to (f), where the pit is located, the laser light is diffracted by the pit to be emitted outside the range of the objective lens f, whereby only part of the incident laser light is returned to the photodetector l. Cause a difference. This is because the depth of the pit is set to λ / 4 of the wavelength, and the reflected light is canceled by interference because the half-waves reflected from the upper and lower sides of the pit are canceled, thereby reducing the amount of light returned to the photodetector 1.

The reflected light modulated by the DVD h or the CD i is reflected through the dual focus lens g and the collimated lens d, and is incident from the collimated lens d to the beam splitter c. It is prevented from being reflected by the beam splitter c and irradiated back to the laser diode a. The modulated reflected light is sent from the beam splitter (c) to the astigmatism generating lens (k), and the reflected light is generated by the astigmatism generating lens (k) to generate astigmatism for detecting a focus error, and the photodetector (c) Proceed to the installed path. The reflected light whose path is changed is converted into a current which reproduces the focus error detection, the tracking error detection, and the recording of the pit by the photodetector 1, and the converted current is demodulated to the original signal by a control circuit (not shown). Will be played.

Therefore, the laser light irradiated from the laser diode (a) as described above is focused on the CD (i) and the DVD (h) via the hologram optical lens (e) in the form of different airy, so that the beam focus is formed at different positions The information recorded on the 1.2mm thick CD and the 0.6mm thick DVD can be selectively read.

In the conventional dual focus optical pickup device, the beam splitter (c) coats a polarizing film on two inclined planes of two rectangular prisms so that the incident light is polarized by 90 ° to distinguish the reflected light from the reflected light. The laser diode (a) and the photodetector (l) are installed because the amount of light is lost when the optical information is read from the high density DVD (h) and the path between the incident light and the reflected light is different from each other. Due to the complexity of the arrangement of the positions, the precision is required, and thus, the manufacturing price of the optical pickup device is increased due to the difficulty of manufacturing, and the manufacturing process is increased, thereby decreasing productivity.

The present invention has been made to improve the above problems, an object of the present invention is easy to manufacture in place of the beam splitter, and selectively transmits the FIFA and the ESPA of the FIFA or ESPA of the laser light irradiated from the laser diode Manufacturing width and manufacturing process of optical pick-up device by installing wide-width control panel to regenerate CDs and DVDs by adjusting the width to change the spherical aberration of FIFA and ESPA formed on the dual focus lens to focus on CD and DVD feet To increase productivity.

In order to achieve the above object, the present invention provides a hologram device having a laser diode for irradiating laser light, a photodiode for converting light reflected from a pit of a CD and a DVD into an electrical signal, and an upper side of the hologram element. A collimating lens installed in parallel with the laser light emitted and diverging in parallel, a width adjusting plate provided on an upper side of the collimating lens to reflect a predetermined wavelength among the laser light and transmitting another predetermined wavelength, and an upper side of the wide adjusting plate. To form a holographic optical lens for correcting spherical aberration at the bottom of the center, and to provide an optical pickup device having a dual focus lens having an objective lens for focusing laser light on the CD and DVD pit. This can be achieved by.

1 is a schematic diagram of a conventional CD-DVD combined optical pickup device.

Figure 2 is a schematic diagram of a CD-DVD combined optical pickup apparatus according to the present invention.

3 is a perspective view schematically showing a hologram element according to the present invention;

<Explanation of symbols for main parts of drawing>

10 hologram element 12 laser diode

14 diffraction grating 16 diffraction plate

18: photodiode 20: collimated lens

30: wide control plate 32: light transmitting substrate

34: PB coating surface 40: dual focus lens

42 hologram optical lens 44 objective lens

50: DVD 52: CD

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, the present invention is constructed with a laser diode 12 for irradiating laser light and a photodiode 18 for converting light reflected from the pits of the CD 52 and DVD 50 into electrical signals. A hologram element 10 having a built-in, a collimator lens 20 installed at an upper side of the hologram element 10 to linearly diverge the laser light emitted, and an upper side of the collimator lens 20. The width adjusting plate 30 reflecting a predetermined wavelength of the laser light and transmitting the other predetermined wavelength, and the hologram optical lens 42 formed on the upper side of the width adjusting plate 30 to correct spherical aberration on the bottom of the center and form an image side And a dual focus lens 40 having an objective lens 44 for focusing laser light onto the pit of the CD 52 and the DVD 50.

As shown in FIG. 3, the hologram device 10 includes a laser diode 12, a CD 52, and a DVD 50 for selectively irradiating a laser light of FI or P s (s). A photodiode 18 for converting light reflected from the light into an electrical signal is provided therein, and a diffraction grating 14 for separating the laser light into 0th order and ± 1st order light above the optical path of the laser diode 12. Is provided, and a diffraction plate 16 for changing the path of the light reflected from the CD 52 and the DVD 50 to the photodiode 18 is provided above the diffraction grating 14.

The width adjusting plate 30 is a polarized beam splitter coating surface 34 reflecting only the E-spa on the upper surface of the light transmitting substrate 32 that transmits both the P-wave and the E-spa of the laser light. ) Is formed to coincide with the width of the holographic optical lens 42 of the dual focus lens 40.

Hereinafter, the operation of the present invention having the configuration as described above.

First, when reproducing the CD 52, the laser diode 12 in the hologram element 10 irradiates the emitted laser light of only the espa s upwards. Then, the laser light irradiated from the laser diode 12 is incident on the diffraction grating 14 provided on the upper side, and is separated into a three-beam beam that is 0-order light and ± 1-order light for focus and tracking error detection. ) And continue upward.

The laser beam transmitted through the diffraction plate 16 goes straight in parallel in the form of diverging while passing through the collimated lens 20 provided on the image side. Subsequently, the laser light passes through the width adjusting plate 30 provided on the upper side. Since the laser light is composed only of an espa (s), the light transmitting substrate 32 of the width adjusting plate 30 is transmitted as it is, but the light transmitting substrate On the PSI coating surface 34 coated on the upper side of the 32, it is not reflected and transmitted. Therefore, only the laser light passing through the center portion without the PBS coating surface 34 of the laser light proceeds upward.

The laser light transmitted through the wide adjustment plate 30 passes through the holographic optical lens 42 formed below the dual focus lens 40, and the spherical aberration is corrected and incident on the objective lens 44. The objective lens 44 ) Is focused on the pit of the CD 52 with a spot size of 1.6 mu m in diameter, and is reflected with digital audio information.

Reflected light reflected from the CD 52 with information passes straight through the objective lens 44 formed on the dual focus lens 40 and the holographic optical lens in parallel, and is installed below the dual focus lens 40. It is transmitted to the center of the light transmitting substrate 32 of the wide control plate 30, and is focused while passing through the collimating lens 20 provided below the wide control plate 30. Subsequently, the reflected light is incident on the diffraction plate 16 of the hologram element 10 provided below the collimated lens 20, the path is changed, and irradiated to the photodiode 18.

The photodiode 18 outputs a digital audio signal from the reflected light modulated and reflected by the CD 52 as an original electrical signal and demodulates the original signal by a digital signal processor (not shown). An RF signal, which is an audio signal recorded on the screen, and a focus signal and a tracking signal, which are error detection signals, are output.

On the other hand, when the DVD 50 is reproduced by the optical pickup device, the laser light emitted only by the wave p is irradiated upward by the laser diode 12 in the hologram element 10. Then, the laser light irradiated from the laser diode 12 is incident on the diffraction grating 14 provided on the upper side, and is separated into a three-beam beam that is 0-order light and ± 1-order light for focus and tracking error detection. ) And continue upward.

The laser beam transmitted through the diffraction plate 16 goes straight in parallel in the form of diverging while passing through the collimated lens 20 provided on the image side. Subsequently, the laser light passes through the width adjusting plate 30 provided on the upper side, and since the laser light is composed only of components of the wave p, the light transmitting substrate 32 and the light transmitting substrate 32 of the width adjusting plate 30 are provided. Penetrating the coated PS coating surface 34 on the upper side of the as it proceeds to the upper side.

The laser beam transmitted through the wide adjustment plate 30 includes a hologram optical lens 42 formed below the dual focus lens 40 and transmits to the outside of the objective lens 44. ) Focuses to a spot size of 0.8 mu m in diameter, focuses on the pit for recording digital video information with high density on the DVD 50, and is reflected along with the optical information.

Reflected light reflected from the DVD 50 with information passes straight through the objective lens 44 and the hologram optical lens 42 formed in the dual focus lens 40 and goes straight in parallel. It is transmitted to the center of the light transmitting substrate 32 of the wide control plate 30 provided below, and is focused while passing through the collimating lens 20 provided below the wide control plate 30. Subsequently, the reflected light is incident on the diffraction plate 16 of the hologram element 10 provided below the collimated lens 20, the path is changed, and irradiated to the photodiode 18.

The photodiode 18 outputs the digital audio signal from the reflected light modulated and reflected by the DVD 50 as an original electrical signal and demodulates the original signal by the digital signal processing unit, thereby recording the audio recorded on the DVD 50. Outputs the signal RF and the error detection signal, the focus signal and tracking signal.

Therefore, in reproducing the CD 152 and the DVD 150 by the optical pickup apparatus according to the present invention, the path of the laser light incident on the CD 152 and the DVD 150 and the CD 152 and the DVD 150 are used. Since the path of the laser light reflected from the same is the same, there is no loss of the amount of light, so that good reproduction is possible.

According to the present invention, the PBS coating surface 34 reflecting only the ESPA s among the laser light emitted from the laser diode 12 of the hologram element 10 is formed on the light transmitting substrate 32 so that the width of the ESPA s is wide. To focus on the CD 52 and to form the focus on the DVD 50 using FI (p) penetrating the PBS coating surface 34 to reproduce the CD 52 and the DVD 50. As the optical pickup device to be used, the wide adjustment plate 30, which is easy to manufacture, is used, which reduces the manufacturing cost and manufacturing process of the optical pickup device and improves the productivity compared to the conventionally used beam split C, which is difficult to manufacture. It can be effective.

Claims (2)

In the CD-DVD combined optical pickup apparatus for reproducing the recording of the pit from the reflected light by irradiating the laser light to the pit recorded on the CD 52 and the DVD 50, the laser diode 12 for irradiating the laser light 12 And a hologram element 10 having a photodiode 18 for converting light reflected from the pit into an electrical signal; A collimated lens 20 installed at an upper side of the hologram element 10 to straighten the laser light emitted in parallel; A width adjusting plate 30 disposed above the collimating lens 20 to reflect a predetermined wavelength of the laser light and transmit another predetermined wavelength; It is provided on the upper side of the wide adjustment plate 30 to form a holographic optical lens 42 for correcting the spherical aberration, and to focus the laser light on the pit of the CD 52 and the DVD 50 on the upper side CD-TV combined optical pickup device, characterized in that consisting of a dual focus lens 40 formed with an objective lens (44). According to claim 1, wherein the width adjusting plate 30 is formed on the upper side of the light transmitting substrate 32, the PBS coating surface 34 for reflecting the Espa (s) of the laser light to a predetermined width, characterized in that CD-DVD optical pickup device.