KR100421458B1 - Optical pick-up - Google Patents

Abstract

The present invention relates to an optical pickup device, and more particularly, two semiconductor chips for projecting light beams having different wavelengths are installed so that light emitting points face each other at predetermined intervals, and are symmetrical between two semiconductor chips. A mirror having an inclined surface to reflect the light beam emitted from each semiconductor chip in a direction perpendicular to the surface on which the semiconductor chip is installed, and a prism for reflecting and transmitting the light beam projected from the two wavelength light source A polarization transducer for converting the linearly polarized beam reflected and transmitted through the prism into a circularly polarized beam, an objective lens for condensing the incident circularly polarized beam at one point of the optical disk, and hitting and reflecting a signal track of the optical disk. It comprises a light detector that detects the light beam and converts it into an electrical signal, the present invention comprises two projections from a two wavelength light source It is not necessary to develop and produce a photodetector having a 10 division pattern because the light beam is formed at a very close point when the light beam is formed on the photo detector, and it is possible to use a photo detector having a 6 division pattern that is produced and used. Since the rain is reduced, there is an effect to develop a low-cost optical pickup device.

Description

Optical pick-up device

The present invention relates to an optical pickup device, and more particularly, to an optical pickup device configured to reduce the difference in path width between light beams projected from a two-wavelength light source to which light beams having different wavelengths are selectively projected. It is about.

In general, an optical pickup is a device for reproducing signals recorded on various optical disks or recording signals on optical disks. DVD and CD products are now widely used.

Of course, although DVD products have high capacity technology, most people are relatively inexpensive and are more accustomed to the widespread use of CD products. Cannot survive, and for this reason, all DVD products on the market are designed to read CD discs together.

In the optical system of such a DVD product, conventionally, two light sources having different wavelengths, that is, wavelengths of 650 nm and 780 nm, have been used. In recent years, two semiconductor chips have two wavelengths in order to reduce the number of components of the optical system. It is a trend that one light source is used.

Fig. 1 schematically shows the configuration of a conventional optical pickup using a two wavelength light source.

Referring to this, the conventional optical pickup has a two-wavelength light source 1 for generating two light beams having different wavelengths, and a prism 3 for projecting and orthogonally diffracting the light beam emitted from the two-wavelength light source 1. ), A polarization converter 4 for converting the linearly polarized beam passing through the prism into a circularly polarized beam, and an objective lens 5 for condensing the circularly polarized beam converted by the polarization converter at one point of the optical disk 6. And a sensor lens 7 for focusing the diffracted light beam when the light beam reflected from the optical disk 6 is orthogonally rotated in the prism 3, and the light beam focused by the sensor lens. It consists of the photodetector 8 which converts an electrical signal.

Briefly describing the operation of the optical pickup thus constructed, the light beam generated from the two-wavelength light source 1 is incident and projected onto the prism 3, and then the linearly polarized beam is converted into a circularly polarized beam by the variable conversion converter 4. . The converted circularly polarized beam is then focused by the objective lens 5 and subsequently reflected on the signal track of the optical disk 6, where the reflected beam is returned to the same path and then by the prism 3 The path is refracted, and the subsequently refracted light beam is focused at the sensor lens 7 and then converted by the photo detector 8 into an electrical signal.

However, in the conventional optical pickup device configured as described above, the two-wavelength light source 1 is slightly different in the position of the light emitting point at which the light beam is projected, so that the light beam emits light and forms a focus on the light detector 8 through the optical path. There were some differences in the location.

Therefore, there is a drawback that the conventional six-split pattern photodetector used in the optical pickup device having two light sources having different wavelengths cannot be applied to the optical pickup device having the two wavelength light sources 1.

That is, in the case of the optical pickup device having two light sources, the light beams projected by the two light sources are formed at one point of the optical detector through the same path, but in the case of the optical pickup device having the two wavelength light sources, Since the paths are different from each other, the light beams are formed at different focal points of the photodetectors, which makes it impossible to apply a six-segment photodetector that cannot detect a signal with a wavelength misaligned.

As such, since the six-segment photodetector is not compatible with each other, when using a two-wavelength light source, as shown in FIG. 1, an additional four-segmentation pattern is additionally added to the existing six-segmentation pattern that can satisfy both wavelengths. Since the photodetector 8 having a 10-split pattern has been developed and used, the cost of using a new pattern of the photodetector has been added, resulting in an increase in the cost of the optical pickup device.

The present invention has been made to solve the above-mentioned problems, the object of which is to reduce the difference in the path width between the light beams having different wavelengths projected from the two-wavelength light source to a minimum two light beams The present invention provides an optical pickup apparatus capable of applying a six-segment pattern photodetector so that it can be formed at a point very close to the detector.

The optical pickup device of the present invention for achieving the above object is provided with two semiconductor chips projecting light beams having different wavelengths so that the light emitting points face each other at a predetermined interval, and are symmetrical between the two semiconductor chips. A two-wavelength light source having a mirror having an inclined surface to reflect the light beam emitted from each semiconductor chip in a direction perpendicular to the surface where the semiconductor chip is installed, a prism that reflects and transmits the light beam projected from the two-wavelength light source; A polarizer for converting the linearly polarized beam reflected and transmitted through the prism into a circularly polarized beam, an objective lens for condensing the incident circularly polarized beam at one point of the optical disk, and the light reflected by hitting the signal track of the optical disk And a photo detector for detecting the beam and converting the beam into an electrical signal.

1 is a schematic view showing a conventional optical pickup apparatus to which a two wavelength light source is applied;

2 is a schematic view showing an optical pickup apparatus according to the present invention;

Figure 3 is a perspective view showing the structure of a two-wavelength light source in the present invention,

4 is a partial plan view schematically showing an example of an image in which two light beams having different wavelengths are formed on a light detector in the present invention.

◎ Explanation of symbols for main part of drawing

1: 2-wavelength light source 1a, 1b: semiconductor chip

2: mirror 3: prism

4: polarization converter 5: objective lens

6: optical disk 7: sensor lens

8: photo detector

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. The same components as in the prior art will be described using the same names and symbols as in the prior art.

Figure 2 is a schematic view showing an optical pickup apparatus according to the present invention, Figure 3 is a perspective view showing the structure of a two-wavelength light source in the present invention, Figure 4 is two light beams having different wavelengths in the present invention A partial plan view schematically showing an example of an image formed on the photodetector.

Referring to this, in the optical pickup apparatus of the present invention, a two wavelength light source 1 for selectively projecting light beams having different wavelengths is used.

Here, the two-wavelength light source 1 is built so that two semiconductor chips 1a and 1b for emitting light beams face each other at predetermined intervals, and one of the two semiconductor chips 1a and 1b is provided. The semiconductor chip 1a emits light beams having a wavelength of 650 nm, and the other semiconductor chip 1b emits light beams having a wavelength of 780 nm.

In addition, a mirror 2 having inclined surfaces symmetrical to each other is provided between the two semiconductor chips 1a and 1b, and the mirror 2 receives a light beam emitted from each of the semiconductor chips 1a and 1b. It is reflected in the direction perpendicular to the reference plane on which (1a, 1b) is installed.

At this time, the inclined plane angle of the mirror 2 is formed such that the distance between the optical axes of each other is 10 占 퐉 or less when the light beams emitted from each of the semiconductor chips 1a and 1b are reflected on the inclined plane.

The light beam projected by the two wavelength light source 1 is incident on the prism 3 to be reflected and transmitted, and the linearly polarized beam reflected and transmitted through the prism 3 is transmitted through the polarization converter 4 while being circularly polarized. Is converted to.

The circularly polarized beam converted while passing through the polarization converter 4 is focused at one point of the optical disk 6 while passing through the objective lens 5.

Then, the light beam hitting the signal track of the optical disc 6 and reflected is incident on the sensor lens 7 through the same path, and astigmatism for detecting the focus error is generated in the sensor lens 7.

The light beam passing through the sensor lens 7 is focused at one point of the photodetector 8, the photodetector 8 converts RF, focus error detection, tracking adjustment and information into an electrical signal, The electrical signal thus converted is demodulated and reproduced into the original signal by a control circuit (not shown).

Now, the operation and effect of the present invention thus constructed will be described.

According to the present invention, two light beams having different wavelengths projected from the semiconductor chips 1a and 1b of the two-wavelength light source 1 are reflected through the inclined surface of the mirror 2 so that the width difference between the optical axes is 10 占 퐉 or less. Since the light detector 8 is reached through the light path, the positions of the light beams on the light detector 8 appear almost the same as shown in FIG. 4.

Distance between optical axes of the light beam PD Balance 5㎛ below 10 10 μm 20% or less

Referring to Table 1 in which the experimental result data are displayed, when the degree of PD balance of the light beam emitted from one of the semiconductor chips 1a is set to 0%, the other semiconductor chip 1b emits light. The light amount skewness of the light beams was found to be 10% or less when the width difference between the optical axes was 5 µm, and 20% or less when the thickness was 10 µm.

At this time, the light amount bias of the light beam is as Equation 1 below with reference to FIG. 4.

As described above, since the two light beams having different wavelengths are focused at almost one point of the photodetector 8, a pattern of 10 divisions is separately used to use the two-wavelength light source 1 as described in the prior art. There is no need to develop an optical detector having a light detector. Since a photodetector 8 having a commonly used six-segment pattern can be used, development costs and parts costs can be reduced, thereby lowering the overall cost of the optical pickup device and developing a low-cost optical pickup device. It becomes possible.

In addition, compared to a conventional optical pickup apparatus having two light sources having different wavelengths, the present invention uses a single light source, which simplifies the assembly process of the optical pickup. Will rise.

As described above, the present invention does not need to develop and produce a photodetector having a 10-dividing pattern because two light beams projected from a two-wavelength light source form at one point in close proximity when they are formed on the photodetector. Since it is possible to use a photodetector having a six-segment pattern, the development cost and parts cost can be reduced, so that an inexpensive optical pickup device can be developed.

Claims (2)

Two semiconductor chips for projecting light beams having different wavelengths are installed so that light emitting points face each other at predetermined intervals, and mirrors having inclined surfaces that are symmetrical to each other are provided between the two semiconductor chips to emit light from each semiconductor chip. A two-wavelength light source for reflecting the light beam to be reflected in a direction perpendicular to the surface on which the semiconductor chip is installed; A prism for reflecting and transmitting the light beam projected from the two wavelength light source, A polarization converter for converting the linearly polarized beam reflected and transmitted through the prism into a circularly polarized beam; An objective lens for condensing the incident circularly polarized beam at one point of the optical disk, And a photo detector for detecting a light beam reflected by the signal track of the optical disk and converting the reflected light beam into an electrical signal. The optical pickup apparatus of claim 1, wherein the inclined plane angle of the mirror is formed such that a distance between optical axes is 10 µm or less when the light beams emitted from the respective semiconductor chips are reflected from the inclined plane.