Patent Application
20070285751
The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
Hereinafter, an optical information processing apparatus according to an exemplary embodiment of the present invention will be described with reference to the attached drawings. The following optical information processing apparatus can be embodied as an optical information reproducing apparatus by excluding the structure of an optical detector, while the optical information processing apparatus can be embodied as an optical information recording apparatus by excluding the structure of a light modulator and partially modifying the structure of an optical system. Accordingly, in the following description, the optical information processing apparatus will be described without distinguishing the recording apparatus and the reproducing apparatus.
As shown in
The signal beam guiding optical system includes a split-beam half-wavelength plate 120 converting the P polarized beam passing through the source-beam polarizing beam splitter 110 into a S polarized beam and a shutter 130 disposed next to the split-beam half-wavelength plate 120. The shutter 130 is opened at the time of recording optical information and is closed at the time of reproducing optical information. A beam expander 140 is disposed next to the shutter 130. The beam expander 140 expands the S polarized beam to such a magnitude that optical information can be loaded to the S polarized beam, and includes a plurality of lens.
A signal beam reflecting member 150 is disposed next to the beam expander 140. In the exemplary embodiment of the invention, the signal beam reflecting member 150 is embodied as a polarizing beam splitter with a cubic shape, which transmits the P polarized beam and reflects the S polarized beam. However, the signal beam reflecting member 150 may be embodied as a different type of polarizing mirror which selectively transmits and reflects beams depending upon polarization components thereof.
A reflecting spatial light modulator 160 is disposed in the traveling path of the S polarized beam reflected by the signal-beam reflecting member 150. The reflecting spatial light modulator 160 may be embodied as a thin film transistor liquid crystal display device (TFT LCD), a super twisted nematic (STN) LCD, a ferroelectric LCD, a polymer dispersed (PD) LCD, or a plasma addressing (PA) LCD, which includes a reflecting mirror (not shown) and a wavelength plate (not shown) such as a half-wavelength plate changing the polarization direction. Alternatively, a digital micro mirror device (DMD) may be used along with a half-wavelength plate.
The S polarized beam entering the spatial light modulator 160 is loaded with optical information and then is converted into a P polarized beam, thereby serving as a signal beam. The signal beam travels to the signal beam reflecting member 150 and the signal beam reflecting member 150 transmits the signal beam. A pair of focusing lenses 170, and an aperture 180 and a signal-beam half-wavelength plate 190 interposed between the focusing lenses 170 are disposed next to the signal beam reflecting member 150. Accordingly, the polarization component of the signal beam is changed while passing through the signal-beam half-wavelength plate 190.
A reference beam reflecting member 520 is disposed next to the focusing lenses 170. The reference beam reflecting member 520 is described later. A first quarter-wavelength plate 210 is disposed next to the reference beam reflecting member 520. The first quarter-wavelength 210 converts the signal beam traveling toward an optical information storage medium 400 into an S circularly polarized beam. A signal-beam objective lens 220 is disposed next to the first quarter-wavelength plate 210. The signal-beam objective lens 220 performs Fourier transformation to a recording signal beam and the irradiates the transformed signal beam to the optical information storage medium 400.
On the other hand, a reference-beam guiding optical system is disposed in the traveling path of the reference beam reflected by the source-beam polarizing beam splitter 110. The reference-beam guiding optical system includes a reflecting mirror 300 reflecting the reference beam and a reference beam selecting member 310 selecting the traveling path of a recording reference beam and the traveling path of a reproducing reference beam.
The reference beam selecting member 310 includes a half-wavelength plate 311 converting the S polarized beam split and reflected by the source-beam polarizing beam splitter 110 into a P polarized beam at the time of recording optical information and maintaining the S polarized beam at the time of reproducing optical information. The reference beam selecting member 310 further includes an actuator 312 revolving the half-wavelength plate 311 to adjust the polarization direction and a reference-beam selecting polarizing beam splitter 313 reflecting the S polarized beam and transmitting P polarized beam. Accordingly, the recording reference beam and the reproducing reference beam have the traveling directions perpendicular to each other.
On the other hand, a first rotating mirror 320 is disposed in the traveling path of the recording reference beam passing through the reference beam selecting member 310. The first rotating mirror 320 is disposed in a line coaxial with the traveling line of the signal beam and at a position opposite to the traveling position of the signal beam about the optical information storage medium 400. The first rotating mirror 320 reflects the recording reference beam at a plurality of multiplexing angles R1, R2, . . . , Rn-1, and Rn (where n is the number of angular multiplexing operations). A first guide lens 330 guiding the multiplexed reference beam and a reference-beam objective lens 340 performing a Fourier transformation process to the reference beam passing through the first guide lens 330 are disposed next to the first rotating mirror 320. A second quarter-wavelength plate 350 is disposed between the first guide lens 330 and the reference-beam objective lens 340.
Accordingly, the recording reference beam passing through the second quarter-wavelength plate 350 is converted into the S circularly polarized beam and then enters the optical information storage medium 400. That is, the signal beam and the reference beam are coaxial with each other and enter the optical information storage medium 400 in the opposite directions with the same polarization component, thereby recording the optical information.
On the other hand, a second rotating mirror 500 and a second guide lens 510 are disposed in the traveling path of the reproducing reference beam reflected by the reference beam selecting member 310. The second rotating mirror 500 is disposed so as to reflect the reference beam in the traveling direction of the signal beam. The second rotating mirror 500 reflects the reference beam at a plurality of multiplexing angles R1, R2, . . . , Rn-1, and Rn (where n is the number of angular multiplexing operations). The reference beam reflecting member 520 is disposed in the traveling path of the signal beam which the recording reference beam reflected by the second rotating mirror 500 enters. The first quarter-wavelength plate 210 and the signal-beam objective lens 220 are sequentially disposed in the traveling path of the reference beam reflected by the reference beam reflecting member 520.
In the exemplary embodiment of the invention, the reference beam reflecting member 520 is embodied as a cubic-shaped polarizing beam splitter transmitting a P polarized beam and reflecting an S polarized beam. However, the reference beam reflecting member 520 may be embodied as a different type of polarizing mirror selectively transmitting and reflecting polarized beams depending upon polarization components thereof. Accordingly, the reference beam reflecting member 520 reflects the reference beam, which is the S polarized beam, toward the optical information storage medium 400 at a right angle.
On the other hand, an optical information detector 600 detecting a reproduced signal beam, which is a phase-conjugation-wave beam emitted from the optical information storage medium 400 in the opposite direction of the incident direction of the recording signal beam and in the coaxial line with the incident line of the recording signal beam, is disposed at the position perpendicular to the spatial light modulator 160 about the signal beam reflecting member 150. The optical information detector 600 may be a charge-coupled device (CCD), a complementary metal-oxide semiconductor (CMOS) device, or an optical element capable of detecting a beam.
Hereinafter, optical information recording and reproducing methods in the optical information processing apparatus according to the exemplary embodiment of the invention will be described.
An optical information recording method according to an exemplary embodiment of the invention is now described.
As shown in
The recording signal beam passing through the signal beam reflecting member 150, the focusing lens 170, the signal-beam half-wavelength plate 190, the aperture 180, the focusing lens, and the reference beam reflecting member 520. The recording signal beam is converted into an S circularly polarized beam by the first quarter-wavelength plate 210. Subsequently, the signal beam is subjected to the Fourier transform process by the signal-beam objective lens 220 and then is incident on the optical information storage medium 400.
On the other hand, the recording reference beam which is the P polarized beam passing through the reference beam selecting member 310 is reflected at a predetermined reflection angle by the first rotating mirror 320. The recording reference beam reflected by the first rotating mirror 310 enters the optical information storage medium 400 through the first guide lens 330, the second quarter-wavelength plate 350, and the reference-beam objective lens 340. At this time, the recording reference beam is converted into the S circularly polarized beam by the second quarter-wavelength plate 350 and then enters the optical information storage medium 400 in the opposite direction of the incident direction of the recording signal beam and with the same polarization component as the recording signal beam.
At the time of recording the optical information by means of angular multiplexing, the incident angle of the recording reference beam is multiplexed by multiplexing the first rotating mirror 320 at a plurality of predetermined angles R1, R2, . . . , Rn-1, and Rn (where n is the number of angular multiplexing operations). Then, all the multiplexed reference beams are scanned at the multiplexing angles set by the first guide lens 330 and the reference-beam objective lens 340 and then is incident on the optical information storage medium 400, as described above.
In this way, the signal beam and the reference beam are incident on the optical information storage medium 400 in the coaxial line, in the opposite directions, and with the same polarization component, thereby recording the optical information loaded into the signal beam in the optical information storage medium 400. Accordingly, since it is not necessary to spatially separate the signal beam and the reference beam in one objective lens at the time of recording the optical information, it is not necessary to use an objective lens having a large numerical aperture (NA). Since it is not necessary to irradiate the reference beam in the limited width between a lens and the optical information storage medium 400, the multiplexing range of incident angle is much widened. This means that the angle for angular multiplexing can be variously varied and the gap between the multiplexing angles can be increased. Accordingly, by multiplexing the reference beam at a variety of angles, it is possible to enhance the multiplexing density of optical information and to increase the gap between the multiplexing angles. As a result, a selection range for a null position for recording can be widened.
Next, an optical information reproducing method will be described.
As shown in
Accordingly, only the reference beam which is the S polarized beam split by the source-beam polarizing beam splitter 110 travels ahead. When the reference beam reaches the reference beam selecting member 310, the half-wavelength plate 311 of the reference beam selecting member 310 maintains the polarization component of the reference beam. Accordingly, the reproducing reference beam is reflected toward the second rotating mirror 500 by the reference-beam selecting polarizing beam splitter 313.
The second rotating mirror 500 reflects the reproducing reference beam at a predetermined angle. The reproducing reference beam reflected by the second rotating mirror 500 is guided to the reference beam reflecting member 520 through the second guide lens 510. The reference beam reflecting member 520 reflects the reproducing reference beam at a right angle.
The reproducing reference beam reflected by the reference beam reflecting member 520 is converted into the S circularly polarized beam by the first quarter-wavelength plate 210 and then the reproducing reference beam which is a phase-conjugation wave of the recording reference beam is incident on the optical information storage medium 400 through the objective lens 220.
On the other hand, at the time of reproducing optical information, by multiplexing the second rotating mirror 500 at the angles set at the time of recording optical information, the incident angle of the reproducing reference beam is multiplexed into a plurality-of multiplexing angles R1, R2, . . . , Rn-1, and Rn (where n is the number of angular multiplexing operations). The multiplexed reference beams are scanned by the second guide lens 510 and the reference-beam reflecting member 520 and then is incident on the optical information storage medium 400 at the multiplexing angles.
The optical information recorded in the optical information storage medium 400 generates a reproduced signal beam, which is a phase-conjugation wave of the recording signal beam, in the coaxial line with the recording signal beam and in the opposite direction of the traveling direction of the recording signal beam in response to by the incident reproducing reference beams at the time of reproducing the optical information. The reproduced signal beam which is a phase-conjugation wave is an S circularly polarized beam. Accordingly, the reproduced signal beam is converted into the P polarized beam by the first quarter-wavelength plate 210, passes through the reference beam reflecting member 520, and is converted again into the S polarized beam by the focusing lens 170 and the signal-beam half-wavelength plate 190. Accordingly, the reproducing signal beam is reflected by the signal beam reflecting member 150 and is detected by the optical information detector 510.
When the optical information is reproduced in this way, the reproducing reference beam is in the coaxial line with the reproduced signal beam and the opposite direction of the traveling direction of the reproduced signal beam. Accordingly, noises due to the scattering of the reference beams are little detected by the optical information detector 510. Therefore, it is possible to enhance the signal-to-noise ratio of the optical information and thus improving the reproducing efficiency of the optical information. Since the reproduced signal beam is the phase-conjugation wave of the recording signal beam, it is possible to use an objective lens with a small numerical aperture.
The optical information processing apparatus according to the exemplary embodiment of the invention can be put into practice in various forms by those skilled in the art by partially modifying the structure or the methods. If the modified examples include the essential elements of the invention, they should be considered as being included in the technical scope of the invention.
In the optical information processing apparatus and the optical information recording and reproducing methods according to the invention, since the signal beam and the reference beam are incident on the optical information storage medium in the coaxial line with each other and in the opposite directions, it is not necessary to spatially separate the signal beam and the reference beam in one lens. Since the reproduced signal beam is the phase-conjugation wave of the recording signal beam, it is not necessary to use an objective lens with a large numerical aperture, thereby reducing the manufacturing cost for the optical information processing apparatus. In addition, by multiplexing the reference beam at a variety of angles, it is possible to enhance the multiplexing density of the optical information. In addition, at the time of reproducing the optical information, noises due to the scattering of the reference beam are little detected by the optical information detector, thereby further enhancing the reproducing efficiency of the optical information. Moreover, it is possible to simplify and miniaturize the entire optical information processing system.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0051123 | Jun 2006 | KR | national |
