KR100245242B1 - An optical pick-up device of dual focus - Google Patents

Abstract

The present invention relates to a dual focus optical pick-up apparatus, and the prism and the prism slopes are coupled to each other, and a PBS coating surface is formed on the inclined surface, and the prism is installed at a predetermined distance from the upper prism to irradiate a beam to one side thereof. A first hologram element, a second hologram element provided at a predetermined distance to the haprism and irradiating a beam to the side thereof, a reflection mirror having a predetermined inclination at a predetermined distance on the other side of the upper prism, and the reflecting mirror It is installed at a certain distance on the upper surface of the disk and has an axial perturbation twin objective lens for condensing the incident beam to a predetermined beam size according to the type of disk. It is possible to design a dual focus optical pickup device that can read optical information of DVD discs and DAD discs at a low price.

Description

Dual focus optical pickup device {AN OPTICAL PICK-UP DEVICE OF DUAL FOCUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dual focus optical pickup device, and in particular, an inclination surface of an upper prism and a lower prism is combined, and each hologram element is formed through a cubic prism having a PBS coating surface formed thereon and a reflection mirror provided on one side of the cube prism. The present invention relates to a dual focus optical pickup apparatus capable of achieving light and small size reduction of an optical pickup apparatus by determining a path of a beam emitted from the optical pickup apparatus.

As a device for picking up recorded information, in the past, a method of detecting information on a disk surface by a mechanical change amount using a contact needle, a method of detecting information by a change in capacitance of a groove grooved in a disk, and the like have been used. However, digital audio discs (DADs) with a spot size of 1.6 μm or 0.8 spot diameters are now used with optical pickup devices in which individual parts such as objective lenses, beam splitters, diffraction gratings, laser diodes, and photodetectors are assembled. Background Art A method of reproducing information recorded on a digital video disc (DVD) having a μm as an electric signal is widely used.

In recent years, a dual focus pickup device capable of reproducing information recorded on a digital audio disc (DAD) and a digital video disc (DVD) by one player has been developed. One conventional model is shown in FIG. 1.

The dual focus optical pickup apparatus includes a laser diode 51 for emitting a laser beam of a predetermined wavelength and a diffraction grating for separating the incident beam provided on one side of the laser diode 51 into 0-order light and ± 1-order light ( 52 and a beam splitter 53 which is provided with a predetermined inclination at a predetermined interval on the diffraction grating 52 so as to reflect and transmit incident light in accordance with a predetermined ratio, and above the beam splitter 53. The collimated lens 54 is installed at a certain distance to maintain the linearity of the incident beam, and the hologram optical lens 56 and the objective lens 57 at a predetermined distance on the image side of the collimated lens 54. Is integrated to focus the incident beam onto a digital video disk (hereinafter referred to as first disk 58) having a thickness of 0.6 mm and a digital audio disk (hereinafter referred to as second disk 59) having a thickness of 0.6 mm in a different beam size. With focus lens 55 The lure is.

In addition, astigmatism is generated at one side surface of the beam splitter 53 to generate astigmatism using optical information recorded on the first and second disks 58 and 59 incident through the dual focus lens 55. A lens 60 is provided, and a photodetector 61 for detecting a beam of incident light information as a predetermined level of electrical signal at a lower distance from the astigmatism generating lens 60 is provided.

The operation of the conventional dual focus optical pickup device having such a configuration will be described.

First, a laser beam having a predetermined oscillation wavelength is emitted from the laser diode 51, and the emitted laser beam is divided into 0th order light and ± 1th order light as it passes through the diffraction grating 52 and is incident on the beam splitter 53. Become. Here, the separation into 0th order light and ± 1th order light is for detecting a tracking error. That is, a beam divided into 0-order light and ± 1-order light is incident on the beam splitter 53, reflected and transmitted by a predetermined reflectance and transmittance, and a beam reflected at a predetermined ratio is via the collimated lens 54. As a result, the beam is incident on the dual focus lens 55 while maintaining the linearity of the beam. Therefore, the beams incident through the dual focus lens 55 are irradiated to the first disk 58 and the second disk 59 by determining the beam size according to the disk.

That is, the beam incident while maintaining constant linearity with the dual focus lens 55 is separated into 0th order light and ± 1th order light along the hologram optical lens 56, and the separated light has different numerical apertures (NA). = 0.6, NA = 0.45, and the light is collected through the objective lens 57 and irradiated onto the first disk 58 having a substrate thickness of 0.6 mm and the second disk 59 having 1.2 mm, respectively. Then, the beam collected by the objective lens 57 in the form of Airy on the order of several micrometers is irradiated onto the signal surface which is the pit 58a of the first disk 58 and the pit 59a of the second disk 59, The irradiated beam is reflected by the objective lens 57 almost as it is in the absence of data recorded on the disk, i.e., without the pits 58a and 59a. Where the pits 58a and 59a are located, light is diffracted by the pits 58a and 59a so that a part of the beam is out of the range of the objective lens 57, which results in only a part of the objective lens 57. The beam of is incident again.

Therefore, the beam of light information incident on the objective lens 57 is incident on the beam splitter 53 via the collimator lens 54 with a light quantity difference. Then, only a part of the beams of the light information incident on the beam splitter 53 passes through the astigmatism generating lens 60. At this time, the beam passing through the astigmatism generating lens 60 is finally incident to the photodetector 61 provided on the bottom surface of the beam in order to detect the focusing error.

On the other hand, in the conventional dual focus optical pickup device, each of the separate optical components are installed independently, the assembly is inferior, and the dual focus lens has a difficult surface in manufacturing, so that the laser diode, the photodetector, and the diffraction grating are integrally installed. By using a hologram element, a dual focus optical pickup device is designed in which an objective lens corresponding to a digital audio disc and a digital video disc rotates on an optical path by an axial perturbation method.

This dual focus optical pickup apparatus is shown in FIG.

The dual focus optical pickup device shown in this figure has a first hologram element 70 for a digital audio disc, and an upper prism 74 and a prism 73 on the upper side at a predetermined distance from the first hologram element 70. It is formed integrally through each of the four slopes of the square) and the slope is installed on one side of the upper prism 74 at a distance from the cubic prism 71, which is a PBS coating surface 72, and the cube prism 71. The collimated lens 80 which maintains the linearity of the lens, the second hologram element 81 for the digital audio disc provided at a distance from one side of the collimated lens 80, and the upper side of the cubic prism 71. It is provided with an objective lens (75, 76) of the axial perturbation system installed at a certain distance to rotate in the optical path according to the type of the selected disk.

On the other hand, in the conventional dual optical pickup device having such a structure, a predetermined beam oscillated by the first hologram element 70 is polarized by the abnormal light (S wave), and also oscillated by the second hologram element 81. When the predetermined beam is polarized by the normal light (P wave), the beams emitted from the hologram elements 70 and 81 through the PBS coating surface 72 of the cubic prism 71 have different beam paths. Therefore, the objective lenses 75 and 76 corresponding to the disks selected according to the different beam paths collect the incident beams by a predetermined beam size, and the condensed beams allow the first and second disks 77 and 78 to be used. The signal of each read optical information is incident on the photodetectors of the first hologram element 70 and the second hologram element 81, and the optical information is converted into a constant electrical signal.

However, the dual focus device is integrated with each optical component, that is, a laser diode, a photo detector, and a diffraction grating, so that the number of components due to assembly is reduced. There is a lot of difficulties in miniaturization by being limited to the installation between the individual parts, and in recent years, the optical pickup device mounted on the vehicle has a lot of problems in the manufacturing because the installation space is further limited due to its installation characteristics.

Accordingly, the present invention has been made to solve the conventional problems, the slope of the upper prism and the lower prism is coupled, the cubic prism formed with a PBS coating surface on the slope and the objective beam path of the incident beam on one side of the cube prism It is an object of the present invention to provide a dual focus optical pickup apparatus capable of contributing to the assembly and adjustment of the optical pickup apparatus as well as to the reduction in light weight and shortness of the optical pickup apparatus.

1 is a block diagram of a conventional dual focus optical pickup device.

2 is a block diagram of another conventional dual focus optical pickup device.

3 is a block diagram of a dual focus optical pickup apparatus according to the present invention;

4 illustrates detection of a focus error according to the present invention.

* Explanation of symbols for main parts of the drawings

1: first hologram element 2: collimated lens

3: cubic prism 4: PBS coated surface

5: Prism 6: Harprism

7: second hologram element 8: mirror reflection

9: objective lens for DAD 10: objective lens for DAD

11: first disk 12: second disk

The present invention for achieving the above object, the first hologram element having an integrated optical element for emitting and receiving a beam of a predetermined wavelength; A collimated lens disposed below the first hologram element at a predetermined distance to maintain linearity of the incident beam; A cubic prism having a PBS coating surface formed on the inclined surface by combining the inclined surfaces of the upper prism and the lower prism with a predetermined distance under the collimated lens; A second hologram element which is provided at one side of the haprism at a predetermined distance and integrally has an optical element that emits and receives a beam of a predetermined wavelength toward one side thereof; A reflection mirror installed at a predetermined slope with a predetermined distance on one side of the upper prism; And an axial perturbation twin objective lens installed at an upper portion of the reflective mirror at a predetermined distance to focus the incident beam at a predetermined beam size according to the type of the disk.

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

3 illustrates a dual focus optical pickup apparatus according to the present invention.

The optical pickup device is provided with a first hologram element 1 having integrally an optical element for emitting and receiving a beam of a constant wavelength, and a lower portion of the first hologram element 1 at a predetermined distance to provide an incident beam. A cubic prism in which a collimating lens 2 which maintains straightness and an inclined surface of the upper prism 5 and the lower prism 6 are formed at a distance from the lower part of the collimating lens 2 to form a cube. 3) and a second hologram element 7 which is provided at one side of the lower prism 6 at a predetermined distance to emit and receive a beam to one side of the lower prism 6, and the upper prism 5 Axial mirrors installed at a predetermined distance on one side with a predetermined inclination, and at an upper portion of the reflecting mirror 8 at a predetermined distance, and rotated in an optical path according to the types of the disks 11 and 12. It consists of twin objective lenses 9 and 10 of the method.

In addition, the slopes of the cubic prism 3 coupled to the upper prism 5 and the lower prism 6 are formed with a PBS coating surface 4 which reflects and transmits the incident prism. In addition, the laser diode of the first hologram device 1 emits a beam polarized by the normal light (P wave), and the laser diode of the second hologram device 7 emits a beam polarized by the abnormal light (S wave). .

In addition, the twin objective lenses 9 and 10 rotate the objective lens corresponding to the selected disk in the optical path, and are usually installed in the axial perturbation actuator. In other words, this axial perturbation method is a method in which objective lenses for DAD and DAD are mounted in one lens holder, and the lens holder is rotated about an axis so that the objective lens suitable for the type of disc is located in the optical path.

On the other hand, looks at the operation of the present invention made of such a configuration.

First, when the first disk 11, which is a DVD, is mounted on the dual focus player, the objective lens actuator, which is not shown, operates and the lens holder rotates about the axis. Thus, the DVD object for playing the first disk 11 is rotated. The lens 10 is positioned in the light path. That is, in the state in which the DVD objective lens 10 is rotated by the optical path, the laser beam polarized with the normal light (P wave) is emitted from the first hologram element 1, and the laser beam is collimated lens 2. The linearity is maintained by passing through and is incident on the PBS coating surface 4 through the upper prism 5 of the cubic prism 3. At this time, the PBS coating surface 4 transmits and reflects according to the polarization state of the incident beam, that is, the beam polarized by the normal light (P wave) is predetermined by the surface when incident on the PBS coating surface 4. When a beam reflected at an angle and polarized with an abnormal light beam (S wave) is incident, it is transmitted as it is.

Therefore, the laser beam of the normal light (P wave) incident on the PBS coating surface 4 is reflected at a predetermined angle and irradiated to the reflection mirror 8 provided at one lower end of the objective lens 10 for DVD. The beam irradiated to the reflecting mirror 8 is then reflected upwards at a constant angle, and the reflected laser beam is incident on the DVD objective lens 10 having a predetermined numerical aperture (NA = 0.6). At this time, the beam incident on the DVD objective lens 10 is condensed into a beam having a predetermined size, focuses on the first disk 11 whose substrate thickness is 0.6 mm, and reads the information recorded on the disk.

That is, the beam focused by the DVD objective lens 10 in the form of a predetermined airy is irradiated onto a signal surface which is a pit 11a to the first disk 11, and the laser beam irradiated onto this signal surface records data. Where there is no pit 11a, the return is almost as it is, but where the pit 11a is located, the laser beam is diffracted by the pit 11a so that a certain amount of beam is out of the range of the DVD objective lens 10. . Therefore, the information recorded on the pit 11a of the first disk 11 is reflected by constant light and is incident again on the DVD objective lens 10.

On the other hand, the beam of light information incident again to the DVD objective lens 10 is irradiated to the reflecting mirror 8, and the beam of light information irradiated to the reflecting mirror 8 has a beam path at a predetermined angle. It is changed and is incident on the PBS coating surface 4 formed on the slope via one side of the upper prism 5. Since the beam of light information incident on the PBS coating surface 4 is in the form of a normal ray (P wave), it is reflected by the PBS coating surface 4 at a predetermined angle and passes through the collimating lens 2 to the first hologram element. It enters into the photodetector in (1).

On the other hand, when the second disk 12, which is a DAD, is mounted on such a dual-focus player, the objective lens actuator, which is not shown, is operated to rotate the lens holder about the axis, so that the DAD for reproducing the second disk 12 is performed. The objective lens 9 is rotated by the optical path. At this time, the laser diode of the second hologram element 7 emits a beam having a predetermined oscillation wavelength (760 nm) and polarized with an abnormal light beam (S wave). 6) is incident on the PBS coating surface 4 via one side. At this time, the PBS coated surface 4 transmits the beam polarized with the abnormal light beam as it is, and the beam radiated from the laser diode of the first hologram element 7 passes through the PBS coated surface 4 and the upper prism 5 Through the incident to the reflective mirror (8) having a predetermined thickness at a predetermined distance on one side of the upper prism (5). Then, in the reflecting mirror 8, the beam path is changed at a predetermined angle so that the incident laser beam is incident on the DAD objective lens 9 provided at a predetermined distance above the reflecting mirror 8. That is, the beam incident on the DAD objective lens 9 is condensed into a beam having a predetermined size, focuses on the second disk 12 whose substrate thickness is 1.2 mm, and reads the information recorded on the disk.

That is, the beam collected by the DAD objective lens 9 in a predetermined airy form is irradiated onto the signal surface, which is the pit 12a of the second disk 12, and the laser beam irradiated onto the signal surface provides data. Where there is no recorded pit 12a, it is returned almost as it is, but where there is a pit 12a the laser beam is diffracted by the pit 12a so that a certain amount of beam is out of the range of the objective lens 9 for the DAD. do. Therefore, the information recorded on the pit 12a of the second disk 12 is reflected by constant light and is incident again on the objective lens 9 for DAD.

On the other hand, the beam of light information incident again on the DAD objective lens 9 is irradiated to the reflecting mirror 8, and the beam of light information irradiated on the reflecting mirror 8 has a predetermined path angle. It is changed to enter the PBS coating surface 4 formed on the slope via one side of the upper prism (5). Since the beam of light information incident on the PBS coating surface 4 is in the form of an abnormal light beam (S wave), the second hologram element 7 which is transmitted to the PBS coating surface 4 as it is and provided on one side of the haprism 6 is provided. Is incident on the photodetector.

In order to detect a focusing error and a tracking error together with the light information incident to the quadrant photodetector in the first hologram element 1 and the second hologram element 7, a light quantity of the beam is diffracted to detect an error. That is, in the present invention, the tracking error detects an error using the one beam method and a focus error using the focal method. In other words, the beam of diffracted light information is received by the photodetector region of each of the usual four-divided hologram elements (1,7), where the focus of the beam as shown in FIG. The shape is irradiated to each area of the photodetector. In the case where the focus is correctly formed on the photodetector, the shape of the beam as shown in FIG. 4B is irradiated to each region of the photodetector. In addition, when the focus comes to the front of the photodetector, each area of the photodetector is irradiated in a beam shape as shown in FIG. 4C.

In this case, each region of the photodetector is divided into D1, D2, D3, and D4, and the focus error detection signal may be represented by the following equation.

F.E.S = (D1 + D4)-(D2 + D3) (where F.E.S is the focus error detection signal)

Therefore, by using the difference in the amount of light in the differential amplifier (not shown) provided at the rear end of the beam irradiated to the photodetector regions of each hologram element 1, 7, an error is detected and this error is corrected by a control device not shown. do.

In the present invention, the tracking error is detected by using the one-beam method. That is, when the beam irradiated to the pits 11a and 12a of the discs 11 and 12 deviates to the left and right sides of the pits 11a and 12a, a difference in the amount of light irradiated to the tracking error detection region appears, whereby the amount of light Is used to correct the error.

In addition, the beam of light information irradiated by the photodetectors of each hologram element (1,7) can be represented by the following equation.

R.F = D1 + D2 + D3 + D4 (where R.F is the optical information signal)

In this way, the positional accuracy of the optical pickup device with respect to the disc, i.e., focusing and tracking error signals, is generated from the shape of the beam irradiated to the photodetectors of the respective hologram elements 1 and 7, and the control not shown in response to the signal is generated. The optical pickup device operates stably by applying a current to the coil of the actuator of the objective lens to correct it.

As described above, the present invention provides a holographic element for radiating and receiving a cubic prism in which the upper prism and the lower prism are fastened, a PBS coated surface formed on the slope of the cube prism, and a beam reflected and transmitted by the PBS coated surface, respectively; The dual-focus optical fiber is equipped with a reflecting mirror installed on one lower surface of the twin objective lens, so that the optical pickup device can be designed in an optimum structure, and the optical pickup device can be read at low cost. The pickup device can be designed.

Claims (2)

A first hologram element 1 having integrally an optical element for emitting and receiving a beam of a constant wavelength; A collimated lens (2) provided at a lower distance to the first hologram element (1) to maintain linearity of the incident beam; A cubic prism (3) having a PBS coating surface (4) formed on the inclined surface by combining the inclined surfaces of the upper prism (5) and the lower prism (6) at a predetermined distance under the collimated lens (2); A second hologram element (7) which is provided at one side of the haprism (6) at a predetermined distance and integrally has an optical element for emitting and receiving a beam of a predetermined wavelength to one side thereof; A reflection mirror 8 installed at a predetermined slope with a predetermined distance on one side of the upper prism 5; And An axial perturbation twin objective lens (9, 10) installed at a predetermined distance above the reflective mirror (8) to focus the incident beam in a predetermined beam size according to the type of the disk (11, 12); Dual focus optical pickup device characterized in that. The laser diode of claim 1, wherein the laser diode of the first hologram element 1 emits a beam polarized with normal light (P wave); The dual focus optical pickup apparatus of claim 2, wherein the laser diode of the second hologram element 7 emits a beam polarized by an abnormal light beam (S wave).

Images