Optical: systems and elements – Holographic system or element – Hardware for producing a hologram
Reexamination Certificate
1999-06-29
2001-07-17
Schuberg, Darren (Department: 2872)
Optical: systems and elements
Holographic system or element
Hardware for producing a hologram
C359S001000, C359S023000
Reexamination Certificate
active
06262819
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a hologram-image recording apparatus and method for producing holographic stereogram which is capable of producing a three-dimensional rendition of either a photograph or an image produced by a computer.
A holographic stereogram is produced by imaging two pictures of a single object obtained by sequentially photographing the object from different observing points. These two pictures are sequentially exposed and recorded on one hologram recording medium as a collection of oblong or dot shaped elements. A user can identify a two-dimensional image, including an aggregate of image information of a portion of the hologram, when the user looks at the holographic stereogram through one eye from a certain position. When the user looks at the holographic stereogram from another position, the user can see a two-dimensional image, including an aggregate of image information of another portion of the hologram. Therefore, when the user looks at the holographic stereogram with both eyes, the parallax between the two eyes causes the recorded hologram to be observed as a three-dimensional image.
Such a holographic stereogram can be produced by a holographic stereogram producing apparatus
100
shown in
FIG. 12
(A). Holographic stereogram producing apparatus
100
includes a laser-beam source
101
for emitting a single wavelength laser beam L
10
exhibiting excellent coherency, and a partial reflecting mirror
102
for splitting laser beam L
10
into an object laser beam L
11
and a reference laser beam L
12
. Optical elements
103
to
107
comprise an optical system for acting upon object laser beam L
11
, and a transmissive LCD display unit
108
is also provided for further acting upon object laser beam L
11
. Optical elements
109
to
111
comprise an optical system for acting upon reference laser beam L
12
. Finally, an electromotive stage
113
is provided for holding a hologram recording medium
112
upon which object laser beam L
11
and reference laser beam L
12
converge, and for moving hologram recording medium
112
as required.
The optical system for acting upon object laser beam L
11
includes the following optical elements sequentially disposed along the optical axis of the path of object laser beam L
11
. A total reflection mirror
103
is first provided for changing the direction of beam L
11
. Beam L
11
then passes through a first cylindrical lens
104
that diffuses beam L
11
in a one dimensional direction. A collimator lens
105
receives beam L
11
and forms beam L
11
into a plurality of parallel laser beams. A projecting lens
106
and a second cylindrical lens
107
are also provided for guiding beam L
11
to hologram recording medium
112
. Display unit
108
is disposed along the light path of beam L
11
, and comprises a transmission type liquid crystal panel disposed between the collimator lens
105
and the projecting lens
106
. Image data output from an image processing portion (not shown) is displayed on the display unit
108
.
The optical system for acting upon reference laser beam L
12
includes the following optical elements sequentially disposed along the optical axis of the path of reference laser beam L
12
. A cylindrical lens
109
is first provided for diffusing beam L
12
in a one dimensional direction. Beam L
12
then passes to a collimator lens
110
that forms diffused beam L
12
into a plurality of parallel laser beams. A total reflection mirror
111
for changing the transmission direction of reference laser beam L
12
to arrive at hologram recording medium
112
is also provided.
Hologram recording medium
112
comprises, for example, a photosensitive film. As shown in
FIG. 12
(B) as well as FIG.
12
(A), medium
112
is held by an electromotive stage
113
. When electromotive stage
113
is moved, medium
112
is intermittently moved as desired in a direction indicated by an arrow b.
During operation, laser beam L
10
is emitted from laser-beam source
101
and is incident on half mirror
102
, as shown in FIG.
12
(A). Half mirror
102
splits laser beam L
10
into object laser beam L
11
and reference laser beam L
12
. Object laser beam L
11
is incident on display unit
108
through first cylindrical lens
104
and collimator lens
105
. When object laser beam L
11
passes through display unit
108
, object laser beam L
11
is image-modulated in accordance with to an image displayed on display unit
108
. Modulated object laser beam L
11
is incident on recording medium
112
after passing through projecting lens
106
and second cylindrical lens
107
. Reference laser beam L
12
is incident on recording medium
112
through the optical system composed of cylindrical lens
109
, collimator lens
110
and total reflection mirror
111
. Interference fringes generated between the reference beam and the modulated object beam are sequentially recorded in the form of oblong or dot shapes on recording medium
112
. These recorded interference fringes form the hologram.
Vibrations exerted on the hologram recording medium
112
disposed in the exposing and recording portion P
100
when each hologram is exposed and recorded may have an adverse influence on the produced holographic stereogram. That is, the holographic stereogram producing apparatus
100
may encounter this problem when small vibrations on the order of the wavelength of the laser beam L
10
are exerted on the recording medium
112
. As a result of such problem, the state of interference fringes which are sequentially exposed and recorded on the recording medium
112
may become instable and a portion of the hologram which are exposed and recorded may encounter a phenomenon wherein the diffraction efficiency and brightness deteriorate. If greater vibrations are exerted on the holographic stereogram producing apparatus
100
, the exposing and recording of the hologram on the recording medium
112
may not be able to be performed.
When a portion of the hologram have been exposed and recorded on the recording medium
112
wherein the diffraction efficiency is unsatisfactorily low due to the influence of vibrations or the like, such portion of the hologram may be in a dark state upon performing a reproducing operation. Accordingly, in such situation, uniformity of the images deteriorates.
As a result, the holographic stereogram producing apparatus
100
is generally provided with a vibration isolator for isolating external vibrations and quickly attenuating exerted vibrations so as to enable an element hologram to be stably exposed and recorded on the recording medium
112
. The vibration isolator may include an air damper or springs appropriately disposed between a substrate on which the laser-beam source
101
and the optical elements of the optical system have been mounted and the case of the apparatus. Such vibration isolator may effectively prevent external vibrations.
Additionally, the holographic stereogram producing apparatus
100
should prevent vibrations of the recording medium
112
which may be exerted by a guide means and a moving means for holding and moving the recording medium
112
. The guide means and the moving means should secure the recording medium
112
so as to prevent small vibrations which may correspond to the wavelength of the laser beam L
10
during exposing and recording of the hologram on the recording medium
112
which is performed in the exposing and recording portion P
100
. When the exposing and recording of the hologram on the recording medium
112
has been completed, the guide means and the moving means may quickly move the recording medium
112
. When the recording medium
112
which has been moved for a predetermined distance is stopped, vibrations may be created which should be quickly damped or attenuated.
However, in the holographic stereogram producing apparatus
100
, it may take approximately two seconds for vibrations created due to the movement and stopping of the recording medium
112
to be attenuated after the recording medium
112
has been stopped. Therefore, the hologra
Shirakura Akira
Suzuki Hirotsugu
Frommer William S.
Frommer Lawrence & Haug LLP.
Schuberg Darren
Smid Dennis M.
Sony Corporation
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