KR0181815B1 - Dual focus optical pickup device - Google Patents

Abstract

The present invention relates to a dual focus optical pick-up device of a digital disc player, in particular having a thickness of 1.2. With a disc thickness of 0.6 The present invention relates to a dual focus optical pick-up device of a digital disc player that enables reading information recorded on an in-disk.

To this end, in a dual focus optical pick-up apparatus that reads information on disks having different thicknesses by concentrating a laser beam generated from a hologram element in which a laser diode, a hologram lattice, a photodetector, etc. are integrated with an objective lens. And a dual beam reflection lens which is installed at a predetermined interval between the hologram element and the objective lens and maintains the incident beam at two kinds of reflection angles to irradiate the beam widths differently to form beam focus on each disk. That's it.

Description

Dual Focus Optical Pick-Up Unit

1 is a data recording state according to the type of disc.

2 is a block diagram of a conventional dual focus optical pick-up device.

3 is a block diagram of an optical pick-up apparatus according to the present invention.

* Explanation of symbols for main parts of the drawings

61 hologram element 62 dual beam reflection lens

63: prism 64: beam split surface

65: first reflective surface 66: second reflective surface

67: objective lens 58: the first disc (0.6 )

59: second disk (1.2 )

The present invention relates to an optical pick-up device of an optical disc player, in particular having a thickness of 1.2. With a disc thickness of 0.6 The present invention relates to a dual focus optical pick-up device of an optical disc player that enables reading information recorded on an in-disk.

In general, disks are larger than 1.2 And 0.6 It is divided into two types having a thickness of 0.6. In recent years, a large amount of video signals can be compressed and recorded on a compact disc (CD) to reproduce them. The research on the Digital Video Player of the DVD (DVD) is being actively conducted.

In such a digital video disc player, as shown in (a) and (b) of FIG. The disc writes data in multiple layers on one side, 0.6 Discs record optical data on both sides so that a large amount of data can be recorded on one disc.

Therefore, the optical pick-up device for reading data recorded on these two types of discs is 0.6 Or 1.2 It is possible to read only the information recorded on either of the discs, and not to read the information recorded on both types of discs.

The reason is that the thickness is 1.2 0.6 compared to disk 0.6 when reading the information recorded on the disc This is because the difference in the thickness of the optical aberration increases and the noise increases, thereby increasing the error occurrence rate so that the recorded information cannot be read accurately.

Therefore, recently, an optical path difference occurs in a beam incident on a main lens according to the degree of diffraction (0th order and ± 1st order diffracted light) of the laser beam by the diffraction grating, and thus the focus is formed at different positions. 1.2 0.6 with disk A dual focus optical pick-up device has been developed for selectively reading information recorded on a disc.

In the structure of the conventional dual focus optical pick-up apparatus, as shown in FIG. 2, a hologram element 51 in which a laser diode, a hologram grating, a photodetector, etc. is integrally installed is provided, and a predetermined slope is provided on one side thereof. The beam split 52 is provided so as to have a constant ratio of reflectance and transmittance to separate incident light into reflected light and transmitted light.

In addition, the holographic optical lens 54 and the objective lens 55 are compositely arranged on the upper portion of the beam split 52 to condense the separated light to be 0.6 Disc (hereinafter referred to as "the first disc") 58 and 1.2 On the disk (hereinafter referred to as " second disk ") 59, a dual focus lens 53 for reading information recorded by focusing is provided.

In the conventional dual focus optical pick-up apparatus having such a structure, first, a laser beam having a predetermined oscillation wavelength is transmitted from the hologram element 51, and such a laser beam has a beam split having a constant ratio of reflectance and transmittance. The incident light is irradiated to 52 to separate the reflected light and the transmitted light, and the reflected light is sent to the dual focus lens 53.

In this case, when the beam processing process of the dual focus lens 53 is examined, the beam reflected through the beam split 52 causes diffraction to occur differently at an arbitrary angle according to the holographic optical lens 54. The beam having such an arbitrary diffraction angle is sent to the objective lens 55 so that the objective lens 55 can condense the beam at another position to produce 0.6 First disk 58 and 1.2 About 1.6 on the second disc 59 The focus is on reading the information recorded on the disc.

That is, about 1.6 by the objective lens 55 The light is collected in an airy shape to a degree and irradiated to the signal surfaces of the pits 58a and 59a of the first disk 58 and the second disk 59. This light is returned almost as it is when there are no pits 58a and 59a in which data is recorded, but where the pits 58a and 59a are light, the light is diffracted by the pits 58a and 59a to produce an objective lens. Out of the field of view of 55, only part of the incident light is returned, thereby generating a light quantity difference in the photodetector built in the hologram element 51.

Therefore, the modulated light information reflected from the first disk 58 and the second disk 59 is embedded in the hologram element 51 through the dual focus lens 53 and the beam split 52. By being sent to a photodetector, the RF signal, the focus signal, and the tracking signal are converted to current, and the converted current is demodulated and reproduced by the digital signal processor, not shown.

That is, since the laser beam emitted from the hologram element 51 passes through the holographic optical lens 54, the beam focus is formed at different positions according to the degree of diffraction of the beam, so that the thickness is 1.2. With disc, 0.6 The information recorded on the disc can be read selectively.

In the conventional dual focus optical pick-up apparatus, the dual focus lens focusing according to the thickness of the disk and the beam splitting split the incident light into the reflected light and the transmitted light are independently separated, so that each component is precisely assembled between the components. As alignment is required, assembly is deteriorated, and it is difficult to control the amount of light of the laser diode due to the difference in thickness between the two disks, and the difference in the degree of flatness causes an error rate to be high, thereby reducing the reliability of the dual focus optical pick-up device. This will occur.

In order to solve the above problems, a triangular prism is disposed between the hologram element and the objective lens, and a beam split film is formed on one surface of the prism, and the other two surfaces are irradiated with the objective lens. By arranging the beam's incidence angle differently and placing the dual beam reflecting lens with different focus positions, two types of discs with different thicknesses can be read so that precision is not required when aligning between the components. In addition, it is easy to adjust the amount of light of the laser diode due to the difference in the thickness of the two disks, and there is no difference in the degree of flatness, so that the error occurrence rate is lowered to provide a dual focus optical pick-up device that can contribute to improving the reliability of the optical disk player. It is an object of the present invention.

In order to achieve the above object, the present invention provides a dual focus for focusing a laser beam generated from a hologram element in which a laser diode, a hologram grating, a photodetector, or the like is integrated with an objective lens to read information on disks having different thicknesses. In the optical pick-up device, the hologram element and the objective lens are provided at a predetermined interval, and the incident beams are maintained at two kinds of reflection angles to irradiate the beam widths differently so that beam focus is formed on each disk. The present invention provides a dual focus optical pickup apparatus having a dual beam reflective lens.

Hereinafter, described in detail by the accompanying drawings as follows.

3 is a block diagram of an optical pick-up apparatus according to the present invention, wherein one side of the hologram element 61 in which a laser diode, a hologram grating, a photodetector, etc. are integrally formed has a triangular shape to form an incident beam having two kinds of reflection angles. The dual beam reflecting lens 62 which is held and irradiated is arranged at a predetermined interval, and the incident beam is connected to the upper side of the dual beam reflecting lens 62 to 0.6. First disk 58 and 1.2 On the second disk 59, an objective lens 67 for reading the recorded information is provided.

In addition, the dual beam reflecting lens 62, on one surface of the triangular prism 63, receives incident light with a constant ratio of reflectance and transmittance of the laser beam irradiated from the hologram element 61 and the objective lens 67. First and second reflection surfaces forming a beam split surface 64 separating the reflected light and the transmitted light, and reflecting the laser beam irradiated from the hologram element 61 on the remaining surfaces of the triangular prism 63. 65, 66 are formed. The laser beam transmitted through the beam splitter surface 64 is refracted by the prism 63, and the refracted beam is totally reflected by the first and second reflecting surfaces 65 and 66, and the total reflected beam is beamed. The incidence point of the splitter surface 64 is directed. The beam exits the prism 63 through the incident point of the beam splitter surface 64 and travels in the same direction as the beam reflected from the beam splitter surface 64 toward the optical disk, so that the beam splitter surface 64 Reflects and turns to form a dual beam with the beam directed to the optical disc. The dual beam reflects light information of the disk irradiated from the objective lens 67 and is irradiated with a photodetector built into the hologram element 61.

In the dual focus optical pick-up apparatus according to the present invention, the reading process of the disk information is as follows.

First, a laser beam having a predetermined oscillation wavelength is transmitted from the hologram element 61, and the laser beam has a beam ratio having a constant ratio of reflectance and transmittance formed on one surface of the prism 63, which is a dual beam reflecting lens 62. The pleated surface 64 is irradiated to separate incident light into reflected light and transmitted light, and the reflected light is focused through the objective lens 67 to be 0.6 The focus is formed on the first disk 58.

On the other hand, when the laser beam of the hologram element 61 transmitted by the beam split surface 64 reaches the first reflection surface 65, the transmitted beam is totally reflected, and the reflected beam is again reflected by the second half. Total reflection is caused by irradiation on the slope 66 again, and the reflected beam passes through the beam split surface 64 and is focused through the objective lens 67 to be 1.2. The focus is formed on the second disk 59.

That is, the first and second reflecting surfaces 65 and 66 may be formed by the beam split surface 64 of the laser beam of the hologram element 61 to directly focus the first disk 58. Since the beams forming the focus on the two disks 59 are made different from each other, the beam focus can be formed on two kinds of disks having different thicknesses.

Therefore, the laser beam focused by the objective lens 67 is 0.6 First disk 58 and 1.2 1.6 on the second disk 59 At the same time, the recorded information is read.

At this time, about 1.6 by the objective lens 67 Condensed in the form of airy disks of the first and second disks 58 and 59 and irradiated onto the signal planes of the pits 58a and 59a of the first and second disks 58 and 59, and the light is absent from the pits 58a and 59a in which data is recorded. Wherever the pit 58a, 59a is returned, the light is diffracted by the pit 58a, 59a and out of the receiving range of the objective lens 67. By returning only a part, a light quantity difference is generated in the photodetector built in the hologram element 61.

Therefore, the modulated light information reflected by the first and second disks 58 and 59 is returned through the objective lens 67 to the light detector embedded in the hologram element 67, thereby providing R.F. ) Signals, focus signals, and tracking signals are converted into electrical signals, and the converted electrical signals are demodulated and reproduced into original signals by a control circuit (not shown).

As described above, in the present invention, a triangular prism is disposed between the hologram element and the objective lens, a beam split film is formed on one surface of the prism, and a reflective film is coated on the other two surfaces to irradiate the objective lens. By arranging the beams of different incidence angles and placing dual beam reflecting lenses with different focus positions, two types of discs with different thicknesses can be read so that the precision of alignment of the components is not required. In addition, it is easy to control the amount of light of the laser diode due to the difference in thickness between the two disks, and the difference does not occur even when it is flat, thereby reducing the error occurrence rate, thereby contributing to improving the reliability of the optical disk player.

Claims (2)

Dual-focus optical pick-up device that reads information of discs having different thicknesses by concentrating a laser beam generated from the hologram element 61 in which a laser diode, hologram lattice, photodetector, etc. are integrally formed with the objective lens 67 In the present invention, the hologram element 61 and the objective lens 67 are provided with a predetermined interval, and some of the incident beams are first reflected, and some of them pass through internal reflection and then merge with the first reflected beam. And a dual beam reflecting lens (62) for forming a beam focus on each disk by irradiating the beam widths differently so as to form a reflected beam of the respective beams. The dual beam reflecting lens 62 is formed on a triangular prism 63 and one surface of the prism 63, and is irradiated from the hologram element 61 and the objective lens 67. A beam split surface 64 which separates the beam into reflected light and transmitted light of a constant ratio, and a beam splitter surface which is formed on the prism 63 and the other two surfaces to reflect the laser beam incident from the hologram element 61, respectively. And a first and second reflecting surface (65, 66) for forming a dual beam towards the disk at (64).