KR100705168B1 - Optical pick-up apparatus - Google Patents

Abstract

The present invention relates to an optical pickup device, in particular to an optical pickup device for minimizing optical components.

An optical pickup apparatus according to the present invention comprises: first and second laser diodes for generating beams of different wavelengths; First optical path switching means for transmitting or reflecting a beam generated by the first or second laser diode according to the incident direction; Second optical path switching means for reflecting a path of the beam emitted by the first optical path switching means in a disc direction and transmitting a reflected light beam from the disk; A photo detector positioned on one side of the second optical path switching means and configured to detect light as an electrical signal; And a collimator lens for converting the beam incident from the second optical path switching means in parallel to be incident on the objective lens, and condensing the beam reflected from the disk to the optical detector through the second optical path switching means. .

Laser diode, plate beam splitter, photo detector

Description

Optical pick-up apparatus

1 is a perspective view of a conventional optical pickup device.

2 is a perspective view of an optical pickup device according to the present invention.

3 shows the position of a photo detector according to the invention;

4 is a view showing the distance between the main cell and the sub-cell of the photo detector according to the present invention.

5 shows an example of aberration compensation in a flat plate according to the present invention.

<Description of the symbols for the main parts of the drawings>

101,102 ... Laser diode 103,105 ... Grating element

104 Compensation Lens 106,107 Beam Splitter

108 ... collimator lens 109 ... objective lens

110 ... light detector 111 ... monitor light detector

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus, in particular having an optical system in which an optical detector and / or a monitor optical detector are arranged on one side of an optical component under the objective lens.

An optical disc is a product that records and reproduces information by using optical characteristics, and is generally manufactured in a small disc shape. In order to use such an optical disc, an optical disc driver is required, and information of the optical disc is reproduced or recorded by an optical pickup mounted inside the optical disc driver.

The optical pickup device is a circuit component such as one or more laser diodes, an optical component that reflects, converges and diverges a beam of a laser, and an instrument component that implements a structure in which the components are mounted and adjustable. Can be divided into the core parts of the part. In addition, a mechanism called an actuator is used in order for the beam to be accurately formed on the optical disk. The actuator is a device that improves the reproduction / recording performance of the laser information by moving the position of the objective lens that collects the laser beam from the laser diode at the exact point where the information on the optical disk is recorded. Such an optical pickup device may be used by applying one or more laser diodes among CD, DVD, and BD laser diodes.

1 is a block diagram showing an optical system of a conventional optical pickup device of two wavelengths.

Referring to FIG. 1, a first light source generated from a first laser diode (eg, CD LD) 11 is converted into a direction of linearly polarized light through a correction lens (CD lens) 13 and a grating lens 15. Incident on the cubic prism 17.

Here, the correction lens 13 is a lens that compensates for the mechanical position and the like so as to maintain a certain distance from the collimator lens 19 that makes the parallel beam. The grating lens 15 is divided into three beams by using a diffraction phenomenon of the incident beam.

Then, the cubic prism 17 transmits or reflects the incident beam according to the polarization direction, and the reflected beam is reflected in the total lens 18 in the direction of the objective lens and is collimated by the collimator lens 19 to the parallel beam. It is made and condensed at a point on the disk (not shown) through the objective lens (20).

Then, the first reflected light beam reflected from the disk is transmitted through the objective lens 20, the collimator lens 19, the total mirror 18, the cubic prism 17, the plate beam splitter 16, and the sensor lens 21. The light is collected by the detector 22 and detected as an electrical signal. The detected signal is used to output servo and RF control signals. Here, the sensor lens 21 is not a uniform curvature of the lens surface, but differently configured in the vertical direction and the horizontal direction to generate astigmatism.

On the other hand, the second light source generated from the second laser diode (eg, DVD LD) 12 is incident on the plate beam splitter 16 via the grating lens 15, and the plate beam splitter 16 is second. The light source is reflected and condensed at a point on the disk through the cubic prism 17, the total mirror 18, the collimator lens 19, and the objective lens 20.

Then, the second light beam generated from the second laser diode 12 is reflected from the disk, and the second reflected light beam is detected as an electrical signal to the photo detector 22 through the reverse path and output as a servo and RF signal. .

As described above, different laser diode powers are required when recording or removing information on the disc and when reading the record information. Thus, in order to check the power state of the objective lens 20 in order to change the laser diode power. By means, the monitor PD 23 detects the optical power.

The optical pickup device is provided with an optoelectronic component for switching the optical path to change the optical path to focus the beam generated by the two laser diodes on the disk in a limited space, the optoelectronic component is transmitted according to the polarization direction of the beam Or it has a property of reflecting, and is typically composed of a cubic prism and / or plate beam splitter.

Conventionally, when composed of three optoelectronic components, a first laser diode (CD LD), a second laser diode (DVD LD), and a photo detector (PD IC) for a two wavelength optical system, at least one that does not interfere with each other's optical path Two mirrors are required. That is, if there is no plate beam splitter, the paths of the second laser diode DVD LD and the photo detector overlap, and if there is no cubic prism, the paths of the first laser diode CD LD and the photo detector overlap. In addition, since the light spot components are arranged laterally, a total mirror for bending the optical path is necessary.

As such, cubic prism or wedge prism, which is inevitably provided on the optical path to configure the two-wavelength optical system, is an expensive optical component and acts as a factor of price increase.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides an optical pickup apparatus capable of coping with three photoelectric components using two mirrors.

The present invention provides an optical pickup apparatus that can provide a path of light for two laser diodes and one optical detector using two plate beam splitters.

The present invention provides an optical pickup device capable of minimizing an optical component disposed on an optical path.

Optical pickup device according to the present invention for achieving the above object,

First and second laser diodes for generating beams of different wavelengths;

First optical path switching means for transmitting or reflecting a beam generated by the first or second laser diode according to the incident direction;

Second optical path switching means for reflecting a path of the beam emitted by the first optical path switching means in a disc direction and transmitting a reflected light beam from the disk;

A photo detector positioned on one side of the second optical path switching means and configured to detect light as an electrical signal;

And a collimator lens for converting the beam incident from the second optical path switching means in parallel to enter the objective lens, and for condensing the beam reflected from the disk to the optical detector through the second optical path switching means. do.

Preferably, the collimator lens and the light detector are installed in a 180 degree direction with respect to the second optical path switching means.

Preferably, the monitor photodetector is further disposed behind the second optical path switching means.

Preferably, the first and second optical path switching means is a plate beam splitter.

Preferably, the focal length of the collimator lens with respect to the light detector is characterized in that less than 11.5mm.

Preferably, the interval between the main and subcells of the photo detector is at most 100um.

Preferably, the incidence side of the first optical path switching means further comprises an aberration compensation lens to compensate for the aberration generated by the plate beam splitter.

Hereinafter, with reference to the accompanying drawings as follows.

2 is a block diagram showing an optical pickup device according to an embodiment of the present invention.

2, first and second laser diodes 101 and 102 for generating beams of different wavelengths; First and second grating elements 103 and 105 provided on the output side of each laser diode 101 and 102; A first plate beam splitter (106) for transmitting or reflecting the generated beam according to the incident direction; A compensation lens 104 provided between the first grating element 105 and the second laser diode 102; A second plate beam splitter (107) for converting the beam emitted from the first plate beam splitter in a disc direction; A collimator lens 108 for paralleling the beam emitted from the second plate beam splitter 107, an objective lens 109 for irradiating the parallelized beam to the disc, and the second plate beam splitter 107 The photodetector 110 and the monitor photodetector 111 are arranged on one side of each other at right angles.

Referring to the accompanying drawings, the optical pickup device according to an embodiment of the present invention as described above are as follows.

Referring to FIG. 2, the first laser diode 101 and the second laser diode 102 use one beam splitter in common. Here, the first laser diode 101 may be a CD LD, and the second laser diode 102 may be a DVD LD.

Grating elements 103 and 105 are arranged on the exit sides of the first and second laser diodes 101 and 102, and are divided into several (eg, three) beams by using the diffraction phenomenon of the incident beam.

In addition, a compensation lens 104 is disposed between the second laser diode 102 and the grating element 105, and the compensation lens 104 corrects the aberration of the beam generated from the second laser diode 102. . An aberration compensation lens such as a toric lens or a cylinder lens is installed on one surface of the compensation lens 102. The aberration compensating lens corrects astigmatism and coma aberration caused by two optical systems using one plate beam splitter.

The toric lens or the cylinder lens generates astigmatism by forming two focal spots using lenses having different horizontal and vertical curvatures. That is, the astigmatism generated by the inclined plate beam splitter 106 is compensated by generating the astigmatism opposite to the astigmatism originally generated by using a toric lens or a cylinder lens having different horizontal / vertical curvatures.

As shown in FIG. 5, the astigmatism and coma aberration in the plate beam splitter 106 are coma aberration and astigmatism of the beam passing through the plate beam splitter 106. It is obtained by Equation 1, and astigmatism is obtained by Equation 2.

Here, Up is an angle formed by the normal of the plate, that is, the vertical plane of the plate, and the chief ray of the incident light, and U is the chief ray and the marginal ray after passing through the plate. T is the thickness of the plate, N is the refractive index of the material constituting the plate, ls 'is the Sagittal Focal Length, and lt' is the Tangential Focal Length. In order to solve the astigmatism and coma aberration problem, a toric lens is formed on the incidence side of the plate beam splitter 106 through which the beam is transmitted, thereby compensating the astigmatism and coma aberration.

Then, the beam emitted from the first plate beam splitter 106 is diverted in the disc direction in the second plate beam splitter 107, and the beam whose path is diverted is converted into a parallel beam by the collimator lens 108. The disk is irradiated at one point by the objective lens 109 of the converted parallel beam.

The reflected light beam reflected from the disk is collected by the objective lens 109, the collimator lens 108, and the second plate beam splitter 107 at the photo detector 110 located below the pickup apparatus.

At this time, one side of the second plate beam splitter 107 is provided with a photo detector 110 and a monitor photo detector 111 disposed in the direction perpendicular to each other. The photo detector 110 is disposed in a 180 degree direction with the collimator lens 108 about the second plate beam splitter 107 and is located within the focal length of the collimator lens 108.

Here, as shown in FIG. 3, the photodetector 110 is disposed under the optical pickup. If the focal length a of the collimator lens 108 is long, the path of light reaching the photodetector becomes long. The thickness of the pickup becomes thick, which causes problems due to the movement of the pickup. In order to prevent this, in the present invention, the focal length (distance) a of the collimator lens 108 is 11.5 mm or less, and the photodetector 110 is disposed in the corresponding position.

In addition, the distance between the main and subcells of the photodetector 110 is determined by the difference in the focal length of the objective lens and the magnification of the light receiving system after the collimator lens. For example, the objective lens has a focal length of 3 mm and a very small magnification with the light receiver, so that when the cell gap of the light detector exceeds about 100 μm, the main and sub beams are formed on the disc when the cell gap is based on two cell gaps. Since the intervals of are further spaced, they become vulnerable to eccentric discs and the like. To this end, the present invention arranges the spacing d of the main and subcells to be less than or equal to 100 μm as shown in FIG.

In addition, the monitor light detector 111 is disposed in the rear direction of the second plate beam splitter 107 to detect the power of the light emitted from the first plater beam splitter 107. That is, different laser diode powers are required when recording or removing information on the disc and when reading the record information, and means for confirming the power state of the objective lens 109 in order to change the laser diode power in this way. The optical power of the monitor is detected by the monitor light detector 111. Since the monitor photodetector 111 is located behind the second plate beam splitter 107, a predetermined beam traveling through the optical path passes through the second plate beam splitter 107 and condenses on the monitor photodetector 111. do. Accordingly, it is not necessary to provide a sensor lens in front of the monitor photodetector as in the prior art.

The present invention can use two plate beam splitters without a cubic prism to advance the path of light emitted from the two laser diodes in the objective lens direction, and to place the photodetector at a position corresponding to the focal length of the collimator lens. Thus, the photo detector does not overlap the path of light with other laser diodes.

Therefore, the present invention can be applied to an optical pickup device without disturbing the path of light of two laser diodes and a photo detector by using two mirrors such as a plate beam splitter. The present invention may use the first plate beam splitter as a cubic prism that is another lens without using the same lens as the second plate beam splitter.

So far, the present invention has been described with reference to the preferred embodiments, and those skilled in the art to which the present invention pertains to the detailed description of the present invention and other forms of embodiments within the essential technical scope of the present invention. Could be implemented. Here, the essential technical scope of the present invention is shown in the claims, and all differences within the equivalent range will be construed as being included in the present invention.

As described above, according to the optical pick-up apparatus according to the present invention, all three photoelectric components can be arranged and used using an inexpensive plate beam splitter without using an expensive cubic prism in an optical system using two or more laser diodes. It is effective.

In addition, there is an effect that can minimize the optical component disposed on the light path.

Claims (11)

First and second laser diodes generating beams of different wavelengths; A plate beam splitter for transmitting or reflecting a beam generated by the first or second laser diode according to an incident direction; Optical path switching means for reflecting the path of the beam emitted by the plate beam splitter in the direction of the disc and transmitting the reflected light beam from the disc; A photo detector positioned at one side of the optical path switching unit and configured to detect light as an electrical signal; And It includes a collimator lens for converting the beam incident from the optical path switching means in parallel to enter the objective lens, and focuses the beam reflected from the disk through the optical path switching means to the optical detector, And an aberration compensating lens further configured to compensate for aberration caused by the transmission thickness of the plate beam splitter at an incident part passing through the plate beam splitter. The method of claim 1, And the collimator lens and the optical detector are installed on opposite sides of the optical path switching means. The method of claim 1, And a monitor photodetector further disposed behind the optical path switching means. delete The method of claim 1, And a focal length of the collimator lens with respect to the optical detector is 11.5 mm or less. The method of claim 1, Optical pickup device, characterized in that the distance between the main and sub-cells of the photo detector is up to 100um. delete In the optical pickup device, Optical path switching means for transmitting or reflecting according to the direction of the beam incident from the plurality of laser diodes; A plate beam splitter for reflecting the beam incident from the optical path switching means toward the objective lens and transmitting the beam reflected from the objective lens; And A photo detector disposed under the plate beam splitter and detecting a transmission beam of the plate beam splitter as an electrical signal; And an aberration compensation lens on the incidence side of the optical path switching means to compensate for the aberration caused by the transmission thickness of the plate beam splitter. The method of claim 8, And a condenser lens which receives the beam reflected by the objective lens and condenses the light detector through the plate beam splitter. The method of claim 9, And said condenser lens is a collimator lens. The method of claim 8, And a monitor photodetector in a direction perpendicular to the photodetector with respect to the plate beam splitter.

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