Optical: systems and elements – Holographic system or element – Hardware for producing a hologram
Reexamination Certificate
1999-06-28
2002-09-10
Henry, Jon (Department: 2872)
Optical: systems and elements
Holographic system or element
Hardware for producing a hologram
C359S003000, C359S022000, C359S030000
Reexamination Certificate
active
06449067
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a cartridge for holding a hologram-image recording medium. The cartridge is mounted on a hologram-image recording apparatus for producing holographic stereogram. The holographic stereogram 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. 17
(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
the 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.
17
(B) as well as FIG.
17
(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
incident on half mirror
102
, as shown in FIG.
17
(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 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. Hologram recording medium
3
is structured as shown in
FIG. 15
, and is used for recording the hologram. Hologram recording medium
3
is a so-called film coating type recording medium incorporating a film base
4
in the form of a tape on which a photopolymer layer
5
composed of photopolymerization-type photopolymers is formed. The photopolymer layer
5
is then coated with a cover sheet
6
.
Referring next to FIGS.
16
(A)-
16
(C), the principle of exposing and recording a hologram on hologram recording medium
3
will be described. Photopolymerization-type photopolymers composing the photopolymer layer
5
of hologram recording medium include monomers M initially regularly dispersed among matrix polymers, as shown in
FIG. 16
(A). When the photopolymerization-type photopolymers are irradiated with a laser beam LA having power of approximately 10 mJ/cm2 to 400 mJ/cm2, monomers M are polymerized into polymers in the exposed portion, as shown in FIG.
16
(B). As the polymerization of the photopolymerization-type photopolymers proceeds, the refractive index between the exposed portions and the non-exposed portions is modulated in accordance with the resulting nonuniformity of the concentration of monomers M caused from movement of monomers M upon exposure. Thereafter, the surface of the photopolymerization-type photopolymers is irradiated with ultraviolet rays or visible light LB having power of about 1000 mJ/cm2 so that polymerization of the monomers M is completed and the position of the monomers are fixed as shown in FIG.
16
(
c
). The refractive index of the photopolymerization-type photopolymers which constitute the photopolymer layer
5
has therefore been changed by the incident laser beam LA. In this manner, interference fringes generated between an object laser beam and a reference laser beam are exposed and recorded on the hologram recording medium
3
.
The holographic stereogram producing apparatus
100
depicted in FIGS.
17
(A) and
17
(B) uses a recording medium such as hologram recording medium
3
of FIG.
15
. One of the benefits of such a recording medium is that no special developing process is required after the exposing process has been performed. Thus, the structure of holographic stereogram producing apparatus
100
can be simplified because a developing unit and so forth can be omitted. Moreover, a holographic stereogram can quickly be produced.
Because hologram recording medium
3
incorporates the photopolymer layer
5
constituted by the photopolymerization-type photopolymers, exposure of the recording medium to light has a detrimental effect on the recording medium, and may sensitize the recording medium. Therefore, hologram recording medium
3
must be loaded into the holographic stereogram producing apparatus
100
in the dark. Complicated handling must be performed to insure that light does not reach the recording medium during loading. Moreover, holographic stereogram producing apparatus
100
Shirakura Akira
Suzuki Hirotsugu
Frommer William S.
Frommer & Lawrence & Haug LLP
Henry Jon
Kessler Grodon
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