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1. WO2009075476 - APPAREIL POUR ENREGISTRER/REPRODUIRE DES INFORMATIONS HOLOGRAPHIQUES

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

Claims
[1] A holographic information recording and/or reproducing apparatus comprising: a light source to emit light;
a polarization forming optical system to form a polarized signal beam and a
polarized reference beam from the light emitted from the light source, wherein
the polarized signal beam and the polarized reference beam are orthogonal to
each other and incident on a holographic information storage medium through an identical surface;
a focusing optical system to focus the polarized signal beam and the polarized
reference beam onto the holographic information storage medium so as to record information by an interference pattern; and
an adjustment optical system to set the focal positions of the polarized signal
beam and the polarized reference beam, and to adjust a difference between a path of the polarized signal beam and a path of the polarized reference beam;
wherein the adjustment optical system comprises:
a first adjustment member to set the focal positions of the polarized signal beam and the polarized reference beam emitted on the holographic information storage medium;
a second adjustment member to adjust the path difference between the polarized signal beam and the polarized reference beam; and
a polarization separation device to separate the polarized signal beam and the
polarized reference beam, which are incident from a first optical system, into two paths based on the beams' polarization so as to direct the polarized signal beam
to the first adjustment member and the polarized reference beam to the second
adjustment member.
[2] The apparatus of claim 1, wherein the first adjustment member is a
2-dimensional (2D) tilt mirror to adjust the reflection angle of an incident beam in two dimensions.
[3] The apparatus of claim 2, wherein the second adjustment member is a translation mirror to adjust the optical path length of the incident beam.
[4] The apparatus of claim 1, wherein the first adjustment member is a one- dimensional (ID) tilt mirror to adjust the reflection angle of an incident beam.

[5] The apparatus of claim 4, wherein the second adjustment member is a translation and a ID tilt mirror to adjust the optical path length of the incident beam and to adjust the reflection angle of the incident beam in a direction different from that of the first adjustment member.
[6] The apparatus of claim 1, wherein the adjustment optical system further comprises:
a first quarter wave plate arranged between the polarization separation device
and the first adjustment member; and
a second quarter wave plate arranged between the polarization separation device and the second adjustment member; wherein
the polarization separation device is a polarization beam splitter.
[7] The apparatus of claim 6, wherein the polarized signal beam is incident on the
first adjustment member and the polarized reference beam is incident on the
second adjustment member.
[8] The apparatus of claim 1, wherein the polarized signal beam is incident on the
first adjustment member and the polarized reference beam is incident on the
second adjustment member.
[9] The apparatus of claim 1, wherein the holographic information storage medium
comprises:
a recording layer; and
a reflection layer;
wherein the focusing optical system causes the polarized signal beam to pass
through the recording layer of the holographic information storage medium,
reflect off the reflection layer, and condense in the recording layer, and causes
the polarized reference beam to be condensed in the recording layer without
passing through the recording layer or reflecting off the reflection layer.
[10] The apparatus of claim 9, wherein the polarized light forming optical system
comprises an active polarization changing device to convert the polarization of a beam emitted from the light source during a recording mode so as to include a
first beam and a second beam having orthogonal polarizations, and to transmit
the beam emitted from the first light source without changing polarization during a reproduction mode.
[11] The apparatus of claim 10, wherein the polarized light forming optical system
separates the optical paths of the polarized signal beam and the polarized
reference beam, transmits the polarized signal beam and the polarized reference beam, and combines the optical paths so as to cause the polarized signal beam
and the polarized reference beam to be incident on the adjustment optical system.

[12] The apparatus of claim 11, wherein the polarized light forming optical system
comprises:
a first optical path changer to separate the beam emitted from the light source
into the first beam and the second beam;
a second optical path changer arranged at a location where the first and second
beams separated by the first optical path changer intersect, to separate an incident beam according to the polarization of the beam;
a first mirror and a second mirror to bend optical paths of the first beam and the second beam separated by the first optical path changer so that the first and
second beams intersect and are incident on the second optical path changer;
a first half wave plate and a second half wave plate arranged on one of the paths of the first and second beams at sides of the second optical path changer so as to convert one linearly polarized beam into the other polarized state, so that the first and second beams is transmitted from the second optical path changer in an
identical polarization state; and
an optical path combining unit to combine the paths of the first and second
beams transmitted from the second optical path changer;
wherein one of the first and second beams is the polarized signal beam and the
other of the first and second beams is the polarized reference beam.
[13] The apparatus of claim 12, wherein the optical path combining unit comprises: a third optical path changer to unconditionally reflect a beam incident from the
second optical path changer;
a third mirror to bend the path of one beam of the first and second beams so as to make the first and second beams intersect, the one beam not being directed to the third optical path changer from the second optical path changer; and
a fourth optical path changer to combine the paths of the first and second beams having different polarizations, wherein the first and second beams are incident
and are intersecting each other by the third optical path changer and the third
mirror.
[14] The apparatus of claim 12, wherein one of the first and second half wave plates, on which the first or second beam incident on the second optical path changer
from the first optical path changer is incident after passing through the second
optical path changer, is an active wave plate operated to pass incident light
without polarization change while the apparatus is operating in a reproduction
mode.
[15] The apparatus of claim 11, wherein the focusing optical system comprises an
objective lens.
[16] The apparatus of claim 15, wherein the focusing optical system further comprises a focus-changeable lens unit to vary the position of the focuses of the polarized
signal beam and the polarized reference beam in the depth direction of the
holographic information storage medium.
[17] The apparatus of claim 16, wherein:
the focus-changeable lens unit comprises a first focus-changeable lens unit and a second focus -changeable lens unit arranged along paths of the polarized signal beam and the polarized reference beam, respectively, and
each of the polarized signal beam and the polarized reference beam travels
separately.
[18] The apparatus of claim 15, further comprising:
a wave plate to convert a polarization of an incident beam between the objective lens and the adjustment optical system; and
a photodetector to receive a reproduction beam reproduced from the holographic information storage medium while the apparatus is in a reproduction mode.
[19] The apparatus of claim 9, wherein the polarized signal beam is incident on the
first adjustment member and the polarized reference beam is incident on the
second adjustment member.
[20] The apparatus of claim 1, further comprising a servo optical system to record
and/or reproduce servo information onto/from the holographic information
storage medium.
[21] An adjustment optical system of a holographic recording and/or reproducing
apparatus, the adjustment optical system comprising:
a first adjustment member to set focal positions of a signal beam and a reference beam emitted onto a holographic information storage medium;
a second adjustment member to adjust a path difference between the signal beam and the reference beam so as to compensate for a path difference between the
signal beam and the reference beam; and
a polarization separation device to separate the signal beam and the reference
beam into a first path for the signal beam and a second path for the reference
beam based on a polarization of the signal beam and the reference beam, so as to direct the signal beam to the first adjustment member and the reference beam to the second adjustment member.
[22] The adjustment optical system of claim 21, further comprising:
a first quarter wave plate arranged between the polarization separation device
and the first adjustment member; and
a second quarter wave plate arranged between the polarization separation device and the second adjustment member.
[23] The adjustment optical system of claim 21, wherein the polarization separation device is a polarization beam splitter.
[24] The adjustment optical system of claim 21, wherein the first adjustment member is a one-dimensional (ID) tilt mirror to adjust a reflection angle of an incident beam.
[25] The adjustment optical system of claim 21, wherein the second adjustment
member is a translation/ ID tilt mirror to adjust a length of an optical path of an incident beam and to adjust a reflection angle of the incident beam in a direction different than that of the first adjustment member.
[26] A polarized light forming optical system of a holographic recording and/or reproducing apparatus, the polarized light forming optical system comprising:
a first polarization changing device to change light emitted from a light source
into a first polarized beam and a second polarized beam orthogonal to the first
polarized beam;
a first optical path changer to separate the first polarized beam and the second
polarized beam;
a first mirror to bend a path of the first polarized beam and a second mirror to
bend a path of the second polarized beam so as to cause the first polarized beam
to intersect the second polarized beam at a second optical path changer;
a first half wave plate and a second half wave plate arranged on one of the paths of the first polarized beam and the second polarized beam and arranged at
different sides of the second optical path changer, to convert the first polarized
beam or the second polarized beam into another polarized state so as to cause the first polarized beam and the second polarized beam to be transmitted from the
second optical path changer in an identical polarization state; and
an optical path combining unit to combine the paths of the first polarized beam
and the second polarized beam after the first polarized beam and the second
polarized beam are transmitted from the second optical path changer;
wherein one of the first polarized beam and the second polarized beam is a signal beam and the other of the first polarized beam and the second polarized beam is a reference beam.
[27] The polarized light forming optical system of claim 26, wherein one of the first half wave plate and the second half wave plate is an active wave plate to pass
incident light without changing a polarization of the light when the holographic
recording and/or reproducing apparatus is operating in a reproduction mode to
reproduce data from a holographic information storage medium.
[28] A holographic recording and/or reproducing apparatus, comprising:
a first light source;
a polarization forming optical system to form a polarized reference beam and a
polarized signal beam having orthogonal polarizations from light emitted by the first light source; a focusing optical system to focus the polarized reference beam and the polarized signal beam on an identical surface of a holographic information storage medium so as to record information via an interference pattern; and
an adjustment optical system to adjust a path difference between the polarized reference beam and the polarized signal beam so as to compensate for the path
difference between the signal beam and the reference beam.
[29] The holographic recording and/or reproducing apparatus of claim 28, further
comprising a servo optical system to record and/or reproduce servo information onto/from the holographic information storage medium.
[30] The holographic recording and/or reproducing apparatus of claim 29, wherein the servo optical system comprises:
a second light source to emit a P-polarized beam;
an optical path changer to transmit the P-polarized beam and to reflect an S- polarized beam; and
a focus-changeable lens unit to vary a focus position of a servo beam in the
holographic information storage medium.
[31] The holographic recording and/or reproducing apparatus of claim 30, wherein the servo optical system further comprises:
a diffraction grating arranged between the second light source and the optical
path changer to diffract the P-polarized beam so as to enable servo error signal detection.