Optical: systems and elements – Holographic system or element – For producing or reconstructing images from multiple holograms
Reexamination Certificate
2000-07-14
2001-12-11
Schuberg, Darren (Department: 2872)
Optical: systems and elements
Holographic system or element
For producing or reconstructing images from multiple holograms
C359S015000, C359S025000
Reexamination Certificate
active
06330087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hologram device and a method for producing a hologram and, in particular, to a screen hologram where a hologram is used for a screen and a method for producing such a screen hologram.
2. Description of Related Art
A screen hologram is known in the prior art. See, for example, Japanese Examined Patent Publication No. 52-12568. In such a screen hologram, a content of a display device is imaged on a transparent screen created under a principle of a hologram, so that a viewer can see the image, while allowing the viewer to see the background via the transparent screen. When the display device is not in use, the screen hologram acts only as a transparent plate.
Such a screen hologram is used, for example, for displaying a content such as an advertisement on a show window in a department store or an underground shopping mall and for displaying a necessary information at counter for a customer or a patient in a bank or hospital, while allowing a receptionist to identify the customer or patient. In the unused state, the screen hologram merely functions as a transparent plate, thereby preventing a view from being hindered by the hologram screen.
FIG. 52
shows a schematic arrangement of a display device using a transparent type of a screen hologram. At a rear side of the screen hologram
1
at a location above a screen hologram
1
, a device for projecting an image such as a projector
3
is arranged. Light
31
from the projector
3
is projected to the screen hologram
1
, so that an image is created on the screen hologram
1
. Llight
32
is thus emitted from the screen hologram
1
, so that a viewer on a front side of the hologram screen can see a displayed image on the screen hologram. Furthermore, a background light
33
passes through the hologram screen
1
without being hindered, which allows the viewer to see not only the displayed content but also the background
7
.
A modified arrangement is possible, where the projector
3
is arranged at the back side of the screen hologram
1
at a location below the hologram
1
.
As a further modified arrangement, in place of the transparent type of hologram
1
, the display device can employ a reflection type of screen hologram, which is per se, known. In such a reflection type, the projector is arranged on the front side of the hologram, so that a viewer on the front side of the hologram can see the displayed content.
Now, a system for producing a transparent type screen hologram will be explained with reference to
FIG. 53. A
reference numeral
110
denotes a laser light generator, from which a laser beam is emitted and is, at a beam splitter, divided into two beams
112
and
113
. The first divided beam
112
is directed to an object lens
122
, so that a diverted light is obtained, which is directed to an off-center concave mirror
114
, so that a parallel beam
115
is obtained. The parallel beam
115
is passed through a light diffusing body
116
constructed, for example, as frosted glass, so that a diffused light, as an object light
117
, is obtained. On the other hand, the second divided beam
113
is introduced into an object lens
121
to obtain a diverted light as a reference light
118
.
The object light
116
and the reference light
118
are directed to a photosensitive member
120
, so that light interference occurrs, whereby generating a light interference fringe which recorded on the photosensitive member
120
. In this case, the light diffusing body
116
as a hologram is recorded in the photosensitive member
120
. Thus, during regeneration process, the light diffusing body is re-generated, so that diffraction and diffusion of the re-generating light, at the hologram, occurrs. As a result, the hologram, from which the diffused light is emitted, functions as a screen.
FIG. 53
illustrates a method for the production of a screen hologram of a transparent type, where exposures to the object and reference lights are done on the same side of the photosensitive member
120
. In case of a reflection type screen hologram, exposures to the object and reference lights are done on the opposite sides of the photosensitive member
120
.
Furthermore, in the illustrated method, an arrangement of the optical system for an exposure is such that the laser beams, i.e., a reference light and an object light, are passed through the same horizontal plane, which allows the hologram of the desired size to be obtained by an execution of a single exposure process. This horizontal plane is, below, referred as an “exposure horizontal plane”.
However, when a hologram produced by the method as explained with reference to
FIG. 53
is used in an optical system for a regeneration as shown in
FIG. 54
, a projection of a white light to the hologram may cause, in a field of view of an observer, the upper part to have a blue color and the lower part to have a yellow or red color.
In order to overcome this problem, Japanese Examined Patent Publication No. 52-12568 proposes a multi-stage exposure method, where a series of exposures to a photo-sensitive member are done by using laser beams of red, green and blue color, respectively. As an alternative, exposures using laser beams of red, green and blue colors are done to separate photo sensitive members, which are, then, laminated.
However, these methods in the prior arts are defective in that three laser devices for laser beams of red, green and blue colors are necessary, which makes the system complicated.
Furthermore, the prior art method in
FIG. 53
is also defective in that a desired quality of a hologram cannot be obtained when a large size of a hologram is needed due to a limitation in the size of the diffusing body. The reason will be explained with reference to FIG.
54
. When a light from the projector
3
is projected to the screen hologram
1
for executing a re-generation of the screen hologram
1
, the projected light is subjected to a diffraction at the screen hologram
1
, so that a scattered light
11
having the same scattering property as that recorded in the hologram is obtained, which allows an observer to view an image on the screen hologram. In this case, a view range of the screen hologram is defined as an area in which an observer can view an image of a light diffusing body recorded in the photosensitive member. Thus, the size of a diffusing body recorded in the screen hologram
1
determines the view area of the screen hologram
1
.
Now, a determination of the size of the diffusing body for producing a screen hologram having a desired view area will now be explained with reference to FIG.
55
. In
FIG. 55
, a diffusing body is designated by a reference numeral
116
. In front of the diffusing body
116
, a photo-sensitive member
120
, having top and bottom ends
120
a
and
120
b,
is arranged at a distance L
1
. A viewer
5
is located in front of the photo-sensitive member
120
at a distance L
2
. A view range is defined by a reference numeral
125
having ends
125
a
and
125
b.
A size of the diffusing body
116
which is necessary for an exposure of the photo-sensitive element is a length A along a plane of the diffusing body
116
from a point where the line a connecting the lower end
125
b
of the view area
125
with the upper end
120
a
of the photo-sensitive member
120
intersects with the plane of the diffusing body
116
to a point where the line b connecting the upper end
125
a
of the view area
125
with the lower end
120
b
of the photo-sensitive member
120
intersects with the vertical plane of the diffusing body
116
.
The size of the diffusing body
116
is actually limited by a particular arrangement of the optical system, that is determined by the value of the distance L
1
between the photo-sensitive member
120
and the diffusing body
116
and a distance L
2
between the photo-sensitive member
120
and the location of the viewer
5
.
In short, the necessary size of the light diffusing body
116
for an exposure of the photo-sensitive element
120
is t
Hattori Hidekazu
Kanda Tomoyuki
Matsumoto Tooru
Nishii Katsuyoshi
Takada Kenichiro
Denso Corporation
Pillsbury & Winthrop LLP
Schuberg Darren
LandOfFree
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