KR100207720B1 - Optical pickup apparatus for recording and reproducing - Google Patents

Abstract

Disclosed is an optical pickup apparatus capable of recording, erasing and reproducing information on a recording medium.

The optical recording apparatus for recording and reproducing is provided on the optical path between the first and second light sources and the recording medium for generating and outputting light of different wavelengths, respectively, to focus the incident light on the recording medium. Disposed on the optical path between the lens and the first and second light sources and the objective lens to selectively transmit / reflect the incident light so that the light incident from the first and second light sources is directed toward the objective lens, thereby providing a path for the incident light. First optical path converting means for converting, second optical path converting means arranged on the optical path between the first optical path converting means and the objective lens to convert the advancing path of the incident light, reflected by the recording medium and the objective lens and And a photodetector for receiving the light emitted from the first light source via the second light path converting means, wherein the light emitted from the first and second light sources is used to record and erase information on the recording medium. At the time of reproduction of information Claim characterized by using the light emitted from the first light source.

Description

Optical pickup device for recording and playback

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus, and more particularly, to an optical pickup apparatus capable of recording and reproducing information on a recording medium.

In general, an optical pickup apparatus for both recording and reproducing is a device which records information on a recording medium or reproduces information recorded on the recording medium in a non-contact manner.

Since the optical pickup device for recording and reproducing is different from the optical power required at the time of recording and reproduction, the laser is used as a light source to generate a suitable output for recording, and the information is recorded on the recording medium by adjusting the amount of emitted light. Play back the information.

Thus, a conventional recording and reproducing optical pickup apparatus which can be used both at the time of recording and reproduction is shown in FIG.

As shown in the drawing, a conventional recording / reproducing optical pickup apparatus includes a light source 1 for generating and emitting light, a collimating lens 18 for converting divergent light emitted from the light source 1 into parallel light, and recording. An objective lens 12 converging incident light so that a light spot is formed on the recording surface of the medium 19, and a polarization beam splitter positioned on an optical path between the light source 1 and the objective lens 12 to convert the optical path 13, a photodetector 16 for detecting error signals and information signals, and a pair of prisms 15 for beam shaping disposed between the collimating lens 18 and the polarizing beam splitter 13; .

The light source 1 is provided with a semiconductor laser, and emits light of a high amount of light when recording information on the recording medium 19, and has a lower amount of light than when recording the information recorded on the recording medium 19. Eject. The objective lens 12 is disposed between the polarizing beam splitter 13 and the recording medium 19 to condense the light incident from the light source 1 to form an optical spot on the recording medium 19.

The polarizing beam splitter 13 transmits light incident from the light source 1 toward the recording medium 19, and reflects light incident from the objective lens 12 toward the photodetector 16. Do it. The photodetector 16 receives the light reflected from the recording surface of the recording medium 19 to detect an RF (Radio Frequency) information signal and an error signal.

In the conventional recording and reproducing optical pickup apparatus provided as described above, information is recorded on the recording surface of the recording medium 19 or the recording medium is controlled by controlling the amount of light so that light of different output is emitted from the light source 1 during recording and reproduction. The information recorded on the recording surface of (19) is reproduced.

In order to form an optical spot of intensity necessary for recording on the recording surface of the recording medium 19, the conventional recording / reproducing optical pickup apparatus as described above uses a semiconductor laser that emits high power to the light source 1, and the collie The collimating lens 18 having a large numerical aperture (NA), for example, approximately 0.3, is used as the mating lens 18 to make a parallel beam. At this time, the parallel beam formed by the collimating lens 18 has a different beam diameter in a direction parallel to and perpendicular to the focusing surface of the semiconductor laser due to the elliptical light emission of the semiconductor laser which is the light source 1. In this way, when the emitted light is elliptical, the optical medium is focused in an elliptical shape and the light loss is increased. In particular, this phenomenon is remarkable because the collimating lens 18 has a large numerical aperture. However, the beam shaping for correcting the beam shape is performed by the pair of prisms 15 to form an optical spot of intensity required for recording on the recording surface of the recording medium 19.

However, the above-described conventional recording and reproducing optical pickup apparatus uses a collimating lens 18 having a large numerical aperture, so that the collimating lens 18 is sensitive to tilt and difficult to install. Since the position of the optical axis changes each time it passes through the prism 15 used for beam shaping, optical alignment of the prism 15 is difficult.

In addition, there is a disadvantage in that an expensive semiconductor laser having a high output is used as the light source 1 in order to obtain the light output required for recording.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described disadvantages, and an object thereof is to provide a recording / reproducing optical pickup apparatus capable of recording, erasing, and reproducing information signals of a recording medium by improving its structure.

1 is a view schematically showing an optical arrangement of a conventional recording and reproducing optical pickup apparatus;

2 is a view schematically showing an optical arrangement of an optical pickup apparatus for recording and reproducing according to an embodiment of the present invention;

3 is a schematic view showing an optical arrangement of a recording / reproducing optical pickup apparatus according to another embodiment of the present invention.

Explanation of symbols for main parts of the drawings

19 ... Recording medium 100a, 200a ... First light source

100b, 200b ... second light source 120 ... objective lens

130a ... first optical path changing means 130b ... second optical path converting means

180, 280 ... collimating lens 190 ... cylindrical lens

195 Wavelength 250 Prism

270 ... beam shaping means

In order to achieve the above object, the recording and reproducing optical pickup apparatus according to the present invention comprises: first and second light sources for generating and emitting light having different wavelengths; An objective lens disposed on an optical path between the first and second light sources and a recording medium to focus incident light on the recording medium; Disposed on the optical path between the first and second light sources and the objective lens to selectively transmit / reflect the incident light so that the light incident from the first and second light sources is directed toward the objective lens, thereby First optical path converting means for converting; Second optical path converting means disposed on an optical path between the first optical path converting means and the objective lens to convert a traveling path of incident light; And a photodetector that is reflected from the recording medium and receives the light emitted from the first light source via the objective lens and the second optical path converting means. The light emitted from the first and second light sources is used, and the light emitted from the first light source is used to reproduce the information.

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

2 is a view schematically showing an optical arrangement of an optical pickup apparatus for recording and reproducing according to an embodiment of the present invention.

As shown, the recording and reproducing optical pickup apparatus records incident light so that light spots are formed on the first and second light sources 100a and 100b and the recording medium 19, respectively. The objective lens 120 focusing on the medium 19, the first and second optical path changing means 130a and 130b for converting the traveling path of the incident light, and a part of the light reflected from the recording medium 19 are received. It is configured to include a photodetector 160. The objective lens 120 includes the objective lens 120 optimized for the emitted light of the first light source 100a.

The first light source 100a includes a semiconductor laser that emits light of approximately 650 nm wavelength, and the second light source 100b includes a semiconductor laser that emits light of approximately 780 nm wavelength. In this case, it is preferable that the first and second light sources 100a and 100b employ a semiconductor laser that emits high power, for example, about 20 mW.

The first light path converting means 130a transmits the light emitted from the first light source 100a and reflects the light emitted from the first light source 100b, thereby allowing the first and second light sources 100a ( 100b) selectively transmits / reflects incident light so that the incident light is directed toward the objective lens 120, thereby converting the traveling path of the incident light. The first optical path converting means 130a preferably includes a polarizing beam splitter having a mirror surface 132a. When the polarization beam splitter is provided as the first optical path converting means 130a, the mirror surface 132a transmits light emitted from the first light source 100a, for example, light having a p-polarized light and transmits the second light. Light emitted from the light source 100b, for example, light having a polarization state of s-wave is preferably coated to reflect.

The second optical path converting means 130b preferably includes a polarizing beam splitter having a mirror surface 132b that selectively transmits / reflects a specific wavelength according to a polarization component. In this case, the mirror surface 132b may be coated to transmit light incident from the first and second light sources 100a and 100b and selectively transmit and reflect light incident from the recording medium 19. . That is, the light emitted from the first light source 100a transmits one polarized light, eg, p-polarized light, and another polarized light, for example, reflects light of the s-polarized light, and the light emitted from the second light source 100b is polarized. Permeation regardless of the ingredients. Therefore, the light emitted from the first light source 100a is used when reproducing the information signal of the recording medium 19 and when detecting the focus and tracking error signals. When the amount of light received by the photodetector 160 is measured, a change in the amount of light emitted from the first light source 100a and a change in the amount of light can be known. Thus, when the amount of light emitted from the first light source 100a is properly adjusted, Information can be reproduced, recorded and erased.

When the polarizing beam splitter is provided as the second optical path converting means 130b as described above, the polarization state of the incident light is changed on the optical path between the second optical path converting means 130b and the objective lens 120. It is preferable to further include the wave plate 195. In this case, the wavelength plate 195 preferably includes a quarter wave plate with respect to the wavelength of the first light source 100a. The optical axis of the wave plate 195 is provided to form an angle of approximately 45 degrees with the linear polarization direction of the light emitted from the first light source 100a and transmitted through the second light path converting means 130b. In this case, the light emitted from the first light source 100a and passing through the second light path converting means 130b, for example, light having a p-polarized light has a fast axis in the p-line polarization direction. 45 degrees relative to the left circularly polarized light while penetrating the wavelength plate 195 and reflected by the recording medium 19 to the left circularly polarized light. The polarization state is changed to light having a s-wave while transmitting again through the wavelength plate 195, and is reflected by the mirror surface 132b of the second optical path converting means 130b to face the photodetector 160. In this case, since the light emitted from the second light source 100b is transmitted on the mirror surface 132b of the second light path conversion means 130b, regardless of the polarization state, the light reflected from the recording medium 19 is reflected. The light transmits the second light path conversion means 130b so that the light emitted from the second light source 100b does not come toward the photodetector 160.

On the other hand, in the recording and playback optical pickup apparatus according to the present embodiment, a collie converting the divergent light incident between the first and second light sources 100a and 100b and the second light path converting means 130b into parallel light. It is preferable to further include a mating lens 180. Here, the collimating lens 180 includes a collimating lens having a small numerical aperture, for example, approximately 0.1.

차광 등으로 회절 투과시키는 그레이팅(미도시)를 더 구비할 수 있다.In addition, a cylindrical lens 190 may be further provided on the optical path between the second optical path converting means 130b and the photodetector 160 to detect a focus error signal. In order to detect the tracking error signal by the 3-beam method, incident light is 0-order light between the first light source 100a and the first light path converting means 130a.

A grating (not shown) for diffraction transmission through light shielding or the like may be further provided.

The optical reproducing apparatus for both recording and reproducing according to the embodiment of the present invention provided as described above drives the optical output of the first light source 100a to be suitable for reproducing when the information of the recording medium 19 is reproduced. At this time, the second light path converting means 130b directs the light reflected from the recording medium 19 of the light emitted from the first light source 100a to the photodetector 160, thereby detecting the information signal and the error signal. It becomes possible.

In addition, when information is recorded on the recording medium 19, the second light source 100b is driven to output light, and the light output of the first light source 100a is driven to be suitable for recording. In this case, some of the light emitted from the first light source 100a is reflected by the recording medium 19 and then reflected by the second light path converting means 130b so that it is received by the photodetector 160. Can be adjusted to suit the recording. At this time, in order to prevent the detection signal of the photodetector 160 from saturation, an optical filter 197 for adjusting the light transmittance on the optical path between the photodetector 160 and the second optical path converting means 130b is used. It may be further provided. Since the optical filter 197 for controlling the light transmittance is known jointly, a detailed description thereof will be omitted.

When the information recorded on the recording surface of the recording medium 19 is erased, the output of the second light source 100b is left as it is, and the light output of the first light source 100a is reduced by about half. In this case, the light output of the second light source 100b provides a bias necessary for erasing.

Therefore, the recording / reproducing optical pickup apparatus according to the embodiment of the present invention as described above uses an optical spot for recording and erasing light spots using the two light sources 100a and 100b. In this case, since the information signal is reproduced using only the first light source 100a at the time of reproduction, the recording and / or reproduction can be performed by using this recording / reproducing optical pickup device.

3 is a view schematically showing an optical arrangement of an optical pickup apparatus for both recording and reproducing according to another embodiment of the present invention. Here, the same reference numerals as the reference numerals of FIG. 2 serve the same function, and thus detailed description thereof will be omitted.

As shown in FIG. 3, the recording and reproducing optical pickup apparatus includes incident light such that light spots are formed on the first and second light sources 200a and 200b and the recording medium 19 which generate and emit light having different wavelengths, respectively. First and second optical paths arranged on the optical path between the objective lens 120 for focusing the light and the first and second light sources 200a and 200b and the objective lens 120 to convert the propagation path of the incident light. An optical path between the converting means 130a and 130b, between the first light source 200a and the first light path converting means 130a, and between the second light source 200b and the first light path converting means 130a. A beam shaping means 270 disposed on and correcting the shape of the beam, and a photo detector 160 for receiving a part of the light reflected from the recording medium 19.

The first light source 200a preferably includes a semiconductor laser that emits light having a wavelength of about 650 nm. In addition, the second light source 200b preferably includes a semiconductor laser that emits light having a wavelength of about 780 nm. In this case, the first and second light sources 200a and 200b employ semiconductor lasers that emit light of about 10 mW.

The beam shaping means 270 includes a collimating lens 280 for converting each of the divergent light emitted from the first and second light sources 200a and 200b into parallel light, and the collimating lens 280 and the first beam. It is configured to include a pair of prism 250 disposed between the optical path conversion means 130a to correct the beam shape of parallel light. Since the light shaped by the beam shaping means 270 has a circular beam shape and parallel light, the shaped light is focused by the objective lens 120 to form a light spot having a strong intensity on the recording medium 19. As described above, even if the light output of the first and second light sources 200a and 200b is approximately 10 mW, an optical spot of intensity required for recording and erasing can be obtained.

Meanwhile, a cylindrical lens 190 is further provided on the optical path between the second optical path converting means 130b and the photodetector 160 to enable detection of a focus error signal. A grating (not shown) may be further provided between the first light source 200a and the first light path converting means 130a to detect the error signal.

The optical pickup apparatus for both recording and reproducing according to another embodiment of the present invention, as described above, can form an optical spot having the intensity required for recording on the recording medium 19 by the beam shaping means 270, thereby recording the information signal. In addition to erasing, the information signal can be reproduced using the first light source 200a. Here, since the functions of the first and second light sources 200a and 200b are the same as those of the first and second light sources 100a and 100b described with reference to FIG. 2, detailed descriptions thereof will be omitted.

Since the optical pickup apparatus for both recording and reproducing according to the embodiment of the present invention as described above uses two light sources, the intensity required for recording and erasing on the recording medium even without using a beam shaping optical system and using a collimating lens having a small numerical aperture Since light spots emitting light can be formed, information can be recorded and erased. In addition, since the collimating lens having a small numerical aperture is used as described above, the collimating lens is less sensitive to tilt, and thus the collimating lens can be easily installed.

In addition, the optical pickup apparatus for both recording and reproducing according to another embodiment of the present invention as described above uses two inexpensive light sources instead of a high output light source by correcting a beam shape to provide an intensity required for recording and erasing on a recording medium. Since an inner light spot can be formed, an inexpensive recording / reproducing optical pickup apparatus can be constructed.

Claims (12)

First and second light sources each generating and emitting light having a different wavelength; An objective lens disposed on an optical path between the first and second light sources and a recording medium to focus incident light on the recording medium; Disposed on the optical path between the first and second light sources and the objective lens to selectively transmit / reflect the incident light so that the light incident from the first and second light sources is directed toward the objective lens, thereby First optical path converting means for converting; Second optical path converting means disposed on an optical path between the first optical path converting means and the objective lens to convert a traveling path of incident light; And a photodetector that is reflected from the recording medium and receives light emitted from the first light source via the objective lens and the second optical path converting means. Optical pickup using the light emitted from the first and second light sources when recording and erasing information on the recording medium, and using the light emitted from the first light source when reproducing information. Device. The optical pickup apparatus of claim 1, wherein the first light source is a semiconductor laser that emits light having a wavelength of approximately 650 nm, and the second light source is a semiconductor laser that emits light having a wavelength of approximately 780 nm. 3. The optical recording apparatus as claimed in claim 1 or 2, wherein the light output of at least one of the first and second light sources is approximately 20 mW. The optical pickup apparatus as claimed in claim 1, wherein the first optical path converting means is a polarizing beam splitter having a mirror surface that transmits one polarization component of incident light and reflects the other polarization component. The mirror surface of claim 1, wherein the second light path converting means selectively transmits / reflects the light emitted from the first light source according to the polarization direction and transmits the light emitted from the second light source. It is a polarizing beam splitter having a recording and playback combined optical pickup device. The optical pickup apparatus according to claim 1, further comprising a wave plate disposed on an optical path between the second optical path converting means and the objective lens to convert a polarization state of incident light. 7. An optical pickup apparatus as both recording and reproduction according to claim 6, wherein the wave plate is a half wave plate with respect to the wavelength of light emitted from the first light source. The collimating lens of claim 1, further comprising a collimating lens disposed on an optical path between the first optical path converting means and the second optical path converting means to convert incident divergent light into parallel light. Optical pickup device for recording and playback. The optical pickup apparatus of claim 1, further comprising a cylindrical lens disposed on an optical path between the second optical path converting means and the photodetector to cause astigmatism. The optical pickup apparatus as claimed in claim 1 or 2, wherein the light output of at least one of the first and second light sources is approximately 10 mW. 11. The optical pickup apparatus of claim 10, further comprising beam shaping means for correcting a shape of a beam on an optical path between the first and second light sources and the first optical path converting means. 12. The apparatus of claim 11, wherein the beam shaping means is disposed on an optical path between the first and second light sources and the first optical path converting means to convert divergent light incident from the first and second light sources toward parallel light. Collimating lenses; And a pair of prisms arranged on the optical path between the collimating lens and the first optical path converting means for correcting the beam shape of the incident light.

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