Optical: systems and elements – Holographic system or element – Hardware for producing a hologram
Reexamination Certificate
2000-03-06
2003-09-09
Chang, Audrey (Department: 2872)
Optical: systems and elements
Holographic system or element
Hardware for producing a hologram
C359S023000, C359S030000
Reexamination Certificate
active
06618175
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a holographic stereogram preparation apparatus capable of three-dimensionally recognizing an actually picked-up image, a computer-generated image, and the like.
A holographic stereogram is prepared as follows. An object is sequentially picked up from different observation points to obtain a number of images. These images, which are used as original images, are recorded sequentially as hologram elements in the form of strips or dots onto a piece of hologram recording medium. When a user looks at this holographic stereogram with only one eye from a certain position, the user discriminates a two-dimensional image as an aggregate of image information of a part of each hologram element. When the user looks at the holographic stereogram from another position shifted from the above-mentioned position, the user discriminates another two-dimensional image as an aggregate of image information of another part of each hologram element. Accordingly, when a user looks at a holographic stereogram with both eyes, a recorded image is recognized as a three-dimensional image.
In general, a holographic stereogram as described above is prepared by a holographic stereogram preparation apparatus
100
as shown in FIG.
1
. The holographic stereogram preparation apparatus
100
comprises a laser light source
101
which emits a laser beam L
10
having a single wavelength and excellent coherence, a half-mirror
102
which spectrally divides the laser beam L
10
, into an objective laser beam L
11
and a reference laser beam L
12
, optical parts
103
to
107
and a display device
108
which construct an optical system for the objective laser beam L
11
, optical parts
109
to
111
which construct an optical system for the reference laser beam L
12
, a hologram recording medium
112
onto which the objective laser beam L
11
and the reference laser beam L
12
are converged, and the like.
The optical system for the objective laser beam L
11
specifically comprises a total-reflection mirror
103
, a first cylindrical lens
104
which diffuses the objective laserbeam L
11
in a one-dimensional direction, a collimator lens
105
which parallelizes the diffused objective laser beam L
11
, a projective lens
106
, a second cylindrical lens
107
which guides the objective laser beam L
11
to the hologram recording medium
112
, all arranged orderly along the optical axis from the input side. The display device
108
is constructed by a transmissible liquid crystal panel and is provided between the collimator lens
105
and the projective lens
106
. An image based on image data outputted from an image processing section not shown is displayed on the display device
108
.
The optical system for the reference laser beam L
12
specifically comprises a cylindrical lens
109
which diffuses the reference laser beam L
12
in a one-dimensional direction, a collimator lens
110
which parallelizes the diffused reference laser beam L
12
, and a total-reflection mirror
111
which reflects the reference laser beam L
12
to guide this beam to the hologram recording medium
112
. The hologram recording medium
112
, for example, is made of a photosensitive film and is fed from a feed reel
113
. Also, this medium is intermittently fed in accordance with an image displayed on the display device
108
, by a feed mechanism omitted from the figure, and is then wound on a wind reel
114
.
The laser beam L
10
is emitted from the laser light source
101
and enters into the half-mirror
102
. This beam is spectrally divided into an objective laser beam L
11
and a reference laser beam L
12
by the half-mirror
102
. The objective laser beam L
11
is let into the display device
108
by the cylindrical lens
104
and the collimator lens
105
, and is subjected to image-modulation in accordance with the image displayed when the beam passes through the display device
108
. The objective laser beam L
11
thus subjected to image-modulation is let into the hologram recording medium
112
through the projective lens
106
and the cylindrical lens
107
. Also, the reference laser beam L
12
is let into the hologram recording medium
112
through the optical system consisting of the cylindrical lens
109
, the collimator lens
110
, and the total-reflection mirror
111
.
Accordingly, a video displayed on the display device
108
is sequentially exposed and recorded in the form of strips or dots taking interference fringes caused by interference between the objective laser beam L
11
subjected to image-modulation and the reference laser beam L
12
as hologram elements.
Meanwhile, the holographic stereogram preparation apparatus
100
as described above has a problem that the holographic stereogram is affected if a vibration or the like is applied when each hologram element is exposed and recorded onto the hologram recording medium
112
. Specifically, in the holographic stereograin preparation apparatus
100
, the state of the interference fringe exposed and recorded becomes unstable, resulting in a phenomenon that the diffraction efficiency or the brightness is lowered at a part of the hologram element recorded and formed, even when a vibration equivalent to the wavelength of the laser beam L or so is applied. Also, if a much greater vibration or the like is applied in the holographic stereogram preparation apparatus
100
, there appears a problem that hologram elements are not recorded or formed at all on the hologram recording medium
112
.
If a holographic stereogram is recorded with a partial hologram element thereof recorded at a low diffraction efficiency as described above, only the hologram element becomes dark when the holographic stereogram is reproduced, and hence, the uniformness of the image is deteriorated.
Therefore, the holographic stereogram preparation apparatus
100
is additionally provided with an antivibration device which restricts a vibration or the like applied from outside and which quickly damps the applied vibration, in order that stabilized hologram elements are exposed and recorded onto the hologram recording medium
112
. The antivibration device is constructed by an air damper a spring, or the like appropriately provided between a substrate mounting respective optical components forming the laser light source
101
and the optical system described above and the apparatus casing.
Meanwhile, in the holographic stereogram preparation apparatus
100
, for example, a semniconductor excitation YAG laser, an air-cooled argon gas laser, an air-cooled krypton laser or the like is used as the laser light source
101
. In the holographic stereogram preparation apparatus
100
, since a laser head section of the laser device described above has a high temperature and makes bad influences on optical components and the like, an air-cooling device is additionally provided to perform cooling. The cooling device cools the laser head section, the heat sink member, and the like of the laser device by ventilation using a cooling fan. Accordingly, it is effective that the cooling device is provided at a position close to the laser device.
However, since the cooling fan of the cooling device rotates and operates during recording of hologram elements onto the hologram recording medium
112
, the holographic stereogram preparation apparatus
100
becomes a vibration source so that the holographic stereogram preparation apparatus
100
is kept vibrated. Consequently, the holographic stereogram preparation apparatus
100
has a problem that the anti-vibration apparatus effectively operates with respect to a vibration and the like which are applied from outside but it is difficult to prepare a holographic stereogram with high precision due to influences from a vibration generated by an internal cooling device.
BRIEF SUMMARY OF THE INVENTION
The present invention, hence, has been proposed to provide a holographic stereogram which solves problems of the conventional holographic stereogram preparation apparatus as described above, carries out efficient cooling for its la
Chang Audrey
Kananen, Esq. Ronald P.
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