Transmission type screen apparatus

A transmission type projection multi-screen apparatus includes a frame, a plurality of transmission type screen units closely arranged in the frame thereby to form a multi-screen, a plurality of projectors at the rear of the screen units for projecting lights of a picture image to the screen units, respectively, and means fixed to the frame for supporting the screen units. The supporting means is placed substantially in a dead angle of the lights.

BACKGROUND OF THE INVENTION 
This invention relates to a transmission type projection screen apparatus 
and relates in particular to a multi-screen apparatus in which plural 
transmission screen units are closely arranged in horizontal and/or 
vertical directions in combination with plural projectors so as to 
constitute a large projection screen system. 
FIG. 7 shows a conventional transmission type projection screen having a 
circular Fresnel lens 11a and a lenticular lens 12a at its opposite sides, 
which are made essentially of a transparent synthetic resin such as 
acrylic resin, vinyl chloride resin, styrene, resin, polycarbonate resin, 
acrylonitrile-styrene copolymerized resin or the like as one body. Since 
relative positions of the lenses 11a, 12a can be precisely maintained, 
such a projection screen has been used in practice. However, it is 
difficult to manufacture a large size screen. 
FIG. 8 shows another conventional projection screen composed of two sheets 
such as a combination of a Fresnel lens sheet 11b and a lenticular lens 
sheet 12b which are separately made of one of the above-stated synthetic 
resins and adhered to each other. Since a broad Fresnel lens sheet cannot 
be manufactured, it cannot be practically used in case of a large screen. 
It has been recently proposed to produce a large multi-screen apparatus 
composed of many small transmission screen units which are supported by an 
aluminum sash frame and plural supports. However, the supports appear as 
relatively wide seams on the multi-screen, which reduces commercial 
values. 
SUMMARY OF THE INVENTION 
The object of this invention is to provide a transmission type projection 
multi-screen apparatus which can have a large and/or broad riding 
projection surface on which only minor seams appear. 
According to this invention, there is provided a transmission type 
projection multi-screen apparatus comprising a frame, a plurality of 
transmission type screen units closely arranged in the frame thereby 
forming a multi-screen, a plurality of projectors at the rear of the 
screen units for projecting lights of a picture image to the screen units, 
respectively, and means fixed to the frame for supporting the screen 
units, the supporting means being placed substantially in a dead angle of 
the lights.

DESCRIPTION OF THE EMBODIMENTS 
Referring now to FIGS. 1 and 2, two transmission type screen units A.sub.1, 
A.sub.2 are closely arranged in a horizontal row so as to form a flat 
projection surface. Two projectors L.sub.1, L.sub.2 are positioned at the 
rear of the screen units A.sub.1, A.sub.2 and project partial lights of a 
picture image to the screen units A.sub.1, A.sub.2, respectively. The 
screen units A.sub.1, A.sub.2 each have a width W. A projection distance P 
is a distance between projection lenses O.sub.1, O.sub.3 of the projectors 
L.sub.1, L.sub.2 and points O.sub.2, O.sub.4 of the screen units A.sub.1, 
A.sub.2. A viewing distance D is a distance between the points O.sub.2, 
O.sub.4 of the screen units A.sub.1, A.sub.2 and typical points AU of 
viewers who are in front of the screen units A.sub.1, A.sub.2. 
Assuming that a line passing the points O.sub.2, O.sub.4 intersects a front 
surface of the screen units A.sub.1, A.sub.2 at points C.sub.0, C.sub.1, 
C.sub.2, which point C.sub.0 is common to the screen units A.sub.1, 
A.sub.2, the points C.sub.1, C.sub.0, C.sub.2 are in a horizontal line 
Y.sub.1 -Y.sub.2 passing each horizontal center of the screen units 
A.sub.1, A.sub.2 while a line X.sub.1 -X.sub.2 is a vertical line along a 
seam formed between the screen units A.sub.1, A.sub.2. A line Z.sub.1 
-Z.sub.2 passes the point C.sub.0 and is at a right angle to both the line 
X.sub.1 -X.sub.2 and the line Y.sub.1 -Y.sub.2. Each projection light 
bundle angle of the projection lenses O.sub.1, O.sub.3 is 2x. Each viewing 
angle of the viewers is 2y. The angle O.sub.1 C.sub.0 Z.sub.1 is x. The 
angle O.sub.3 C.sub.0 Z.sub.1 is x. Therefore, a dead angle of the 
projection lights from the projectors L.sub.1, L.sub.2 is 2x at a joint 
portion of the screen units A.sub.1, A.sub.2. The angle AU C.sub.0 Z.sub.2 
is y. 
In view of the foregoing, a support Ta of a triangular section having a tip 
angle of 2x or less is placed whithin a V-shaped space formed between the 
adjacent screen units A.sub.1, A.sub.2 corresponding to the dead angle 2x 
for supporting the adjacent screen units A.sub.1, A.sub.2 whereby the 
support Ta cannot be easily seen from the viewers. 
In FIGS. 3 and 4, two transmission type screen units A.sub.1, A.sub.4 are 
closely arranged in a vertical row so as to form a flat projection 
surface. Two projectors L.sub.3, L.sub.4 are placed at the rear of the 
screen units A.sub.1, A.sub.2 and project partical lights of a picture 
image to the screen units A.sub.3, A.sub.4, respectively. The screen units 
A.sub.3, A.sub.4 each has a height H. A projection distance P is a 
distance between projection lenses O.sub.11, O.sub.12 of the projectors 
L.sub.3, L.sub.4 and points O.sub.12, O.sub.14 of the screen units 
A.sub.3, A.sub.4. A viewing distance D is a distance between the points 
O.sub.12, O.sub.14 of the screen units A.sub.3, A.sub.4 and typical points 
AU of viewers who are in front of the screen units A.sub.3, A.sub.4. 
Assuming that a line passing the points O.sub.12, O.sub.14 intersects each 
front surface of the screen units A.sub.3, A.sub.4 at points C.sub.10, 
C.sub.11, C.sub.12, which point C.sub.0 is common to the screen units 
A.sub.3, A.sub.4, the points C.sub.11, C.sub.10, C.sub.12 are in a line 
X.sub.11 -X.sub.12 passing each vertical center of the screen units 
A.sub.3, A.sub.4 while a line Y.sub.11 -Y.sub.12 is a horizontal line 
along a seam formed between the adjacent screen units A.sub.3, A.sub.4. A 
line Z.sub.11 -Z.sub.12 passes the point C.sub.10 and is at a right angle 
to both the line X.sub.11 -X.sub.12 and the line Y.sub.11 -Y.sub.12. 
Each projecton light bundle angle of the projectors L.sub.3, L.sub.4 is 2x 
while a viewing angle of the viewers is 2y. The angle O.sub.11 C.sub.10 
Z.sub.11 is x, and the angle O.sub.13 C.sub.10 Z.sub.11 is x. Thus, a dead 
angle of the projection lights from the projectors L.sub.3, L.sub.4 is 2x 
at a joint portion of the screen units A.sub.3, A.sub.4. The angle AU 
C.sub.10 Z.sub.12 is y. 
In view of the foregoing, a support Tb of a triangular section having a tip 
angle of 2x or less is placed whithin the dead angle 2x for supporting the 
screen units A.sub.3, A.sub.4 whereby the support Tb cannot be easily seen 
from the viewers. 
In FIG. 5, two transmission type screen units A.sub.1, A.sub.2 are closely 
arranged along a horizontal imagined circle at the same distance D from a 
typical viewer AU in front of the screen units A.sub.1, A.sub.2 and so as 
to form a bent projection surface. Two projectors L.sub.1, L.sub.2 project 
partial lights of a picture image to the screen units A.sub.1, A.sub.2, 
respectively, with a projection distance P. Assuming that a half of a 
projection light bundle angle from the projectors L.sub.1, L.sub.2 is x 
and a half of a viewing angle from the viewer is y, a dead angle of the 
lights from the projectors L.sub.1, L.sub.2 is 2(x+y) at a joint portion 
of the screen units A.sub.1, A.sub.2. 
Thus, a support Tc of a triangular section having a tip angle of 2(x+y) or 
less is placed whithin the dead angle 2(x+y) for supporting the screen 
units A.sub.1, A.sub.2 whereby the support Tc cannot be easily seen from 
the viewer. 
Although not shown in the drawings, two screen units A.sub.1, A.sub.2 can 
be arranged along a vertical circle or in a height direction at the same 
distance from a viewer as in the embodiment of FIG. 5. 
Referring again to FIGS. 1 and 2, the dead angle of the projection lights 
will be explained. 
Assuming that the screen units A.sub.1, A.sub.2 each have a height H of 900 
mm and a width W of 1,800 mm, a diagonal line thereof has a length of 
about 2,000 mm. Usually, the projection distance P is selected to be equal 
to the length of the diagonal line, that is, about 2,000 mm. According to 
the following equation, 
EQU tan x=W/2P=1,800/(2.times.2,000) 
X is about 24 degrees. In this case, the dead angle is about 48 degrees so 
that the support Ta can have a large tip angle so as to provide a high 
structural strength. The same can be said of the embodiments of FIGS. 3 to 
5. 
In the embodiments of FIGS. 1 to 5, the supports Ta, Tb or Tc can be 
composed of two halves each having a tip angle of x or (x+y). 
FIGS. 6A and 6B show a further embodiment of this invention essentially 
corresponding to the embodiment of FIGS. 1 and 2. Two transmission type 
screen units A.sub.1, A.sub.2 are closely joined at their side edges and 
supported by a support 10 and a frame 11 which are joined by two U-shaped 
connectors 12. The support 10 is a triangular post placed whithin a dead 
angle (2x) of projection lights from two projectors (not shown) placed at 
the rear of the screen units A.sub.1, A.sub.2. 
FIGS. 6C and 6D show a joint portion of a further embodiment of this 
invention. Two transmission type rectangular screen units A.sub.1, A.sub.2 
are closely arranged at their side edges and supported by two supports 
10-1, 10-2 and plural holder plates 13a, 13b which are fixedly joined to 
each other by screws 14. The holder plates 13a, 13b are also fixed to the 
opposite side edges of the screen units A.sub.1, A.sub.2, respectively, by 
means of the screws 14. In other words, the screen unit A.sub.1 is fixed 
to the support 10-1 by means of the holder plates 13a while the screen 
unit A.sub.2 is fixed to the support 10-2 by means of the holder plates 
13b. Those supports 10-1, 10-2 are fastened by a bolt 16 set through each 
hole 15 of the supports 10-1, 10-2. In such a fastened condition, the 
holder plates 13a, 13b are positioned one after the other along the side 
edges of the screen units A.sub.1, A.sub.2. As shown in FIG. 6D, the 
supports 10-1, 10-2 and a majority of the holder plates 13a, 13b are 
positioned within the dead angle 2x of the projection lights from 
projectors (not shown) placed at the rear of the screen units A.sub.1, 
A.sub.2 as in the embodiment of FIGS. 1 and 2. Merely each front end 
surface of the holder plates 13a, 13b appears on a multi-screen projection 
surface. A thickness of the front end of the holder plates 13a, 13b can be 
limited to several millimeters. 
FIG. 6E shows another embodiment of this invention which is similar to the 
embodiment of FIGS. 6C and 6D except for the construction of the screen 
units A.sub.1, A.sub.2. In FIG. 6E, the screen units A.sub.1, A.sub.2 are 
composed of lenticular lenses A.sub.1 -R, A.sub.2 -R joined directly to 
each other at their side edge and Fresnel lenses A.sub.1 -F, A.sub.2 -F 
joined indirectly through the holder plates 13a, 13b whereby the front 
ends of the holder plates 13a, 13b do not appear on a multi-screen 
projection surface. In other words, the holder plates 13a, 13b are 
inserted in a narrow groove of a channel shape forme in the adjacent 
Fresnel lenses. The supports 10-1, 10-2 and the holder plates 13a, 13b are 
completely positioned within the dead angle 2x of projection lights from 
projectors (not shown) placed at the rear of the screen units. 
The supports 10-1, 10-2 and their related members shown in FIGS. 6A to 6E 
can be also applied to the embodiments of FIGS. 3 to 5 as well as any 
other multi-screen apparatus such as a large multi-screen apparatus which 
is, for example, composed of 9 screen units supported by plural supports 
of a lattice form in a rectangular frame. 
The supports may be solid or hollow in any desired shape and made of 
aluminum or steel. They are to be joined to each other and also to the 
frame by adhesives, welding or any other fixing means. 
It is preferable that the width of a seam formed between the adjacent 
screen units A.sub.1 and A.sub.2, A.sub.3 and A.sub.4 is limited to 
resolving powers of viewers' eyes. In general, the visual angle of such 
resolving powers is 0.00029. For example, resolving powers can be shown 
with respect to distances between viewers' eyes and a mutli-screen as 
follows: 
______________________________________ 
Distance (mm) Resolving Power (mm) 
______________________________________ 
250 0.07 
500 0.15 
1,000 0.3 
2,000 0.6 
5,000 1.2 
10,000 2.4 
20,000 5.0 
______________________________________ 
Accordingly, even if the supports and their related elements appear on the 
multi-screen projection surface, they do not obstruct the view in case the 
width of them is less than a resolving power. 
A broad multi-screen apparatus having a total width of 18,000 mm will be 
explained as an example. Ten screen units each having a width of 1,800 mm 
are closely arranged along an imagined circle having a radius equal to the 
viewing distance D as in FIG. 5. Ten projectors as set at the rear of the 
ten screen units, respectively. 
The projection lenses of the projectors and a typical viewer are positioned 
in a conjugate relation to each other by the field lenses (Fresnel lenses) 
of the screen units. Thus, the viewer is in front of all screen units. 
Each projection light bundle is uniformly distributed in a lateral 
direction by each directional lenticular lenses of the screen units. An 
image formed by each projection lenses of the projectors functions as a 
secondary light source and is distributed by the corresponding lenticular 
lens thereof in a predetermined manner. It takes place through the whole 
width of the broad multi-screen. 
Plural screen units can be closely arranged along a circle having a radius 
larger than that of FIG. 5. 
According to this invention, means for supporting the screen units do not 
obstruct the view because the supporting means is placed substantially 
within a dead angle of projection lights from the projectors. Viewers in 
front of the screen units apparently see only very minor seams between the 
adjacent screen units. Therefore, commercial values of a multi-screen 
apparatus according to this invention are remarkable, particularly in the 
case of movie-like pictures including quick motion pictures.