Hemispherical motion picture screen

[57] ABSTRACT

A hemispherical motion picture screen is provided with a spherical or arcuate lower extension, and the screen is comprised of a plurality of individual screen strips. The screen is in the form of a sphere which is truncated below the equator, the lower extension extending downwardly below the equator of the screen and being a continuation of the spherical shape so that dead zones in the projected image are eliminated. The spherical shape of the screen is provided by a plurality of frame units, each of which includes a plurality of generally horizontally disclosed screen strips. The screen strips are positioned in overlapping relationship with their disclosed faces directed downward.

Claims, 8 Drawing Figures

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PATENTED oct 3 1972

3.695,751

SHEET 1 OF 3

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PATENTED OCT 3 1972

3,695,751

SHEET 2 OF 3

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PATENTED OCT 3 1972

3,695,751

SHEET 3 OF 3

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3,695,751

HEMISPHERICAL MOTION PICTURE SCREEN

BACKGROUND OF THE INVENTION

This invention relates to a hemispherical screen for motion pictures.

Conventionally, screens for motion pictures were in the form of plane and consequently the images projected on such screens were planar and could not fully appeal to the audience. In an attempt to make the images look three-dimensional, a curved screen has been developed as used for “Cinerama.” However, it is ultimately desired to provide a three-dimensional screen which enables the audience to watch projected images all around and above.

SUMMARY OF THE INVENTION

The present invention provides a hemispherical screen for motion pictures which enables the audience to watch the projected images with the same feeling as when they stand on the ground and look up or around. The screen is not exactly in a hemispherical shape but in the form of a sphere which is truncated below the equator. When a person stands upright and looks at the front, the lower end of the view he commands is positioned some distance below the horizontal line at the level of the eyes. If the screen is exactly in the form of a hemisphere, the lower end of the screen is positioned on the horizontal line at the level of the eyes, with the result that the lower portion of the view is not covered by the screen. In the case where the screen is in the form of a sphere which is truncated below the equator the screen covers both the upper and lower ends of the view commanded by the person. Further if the lower extension of the screen is in the form of a cylinder which extends downward from the equator, there arise dead zones where no image is projected, whereas the extension which extends downward from the equator in the form of a sphere insures elimination of such dead zones. The spherical shape of the screen is provided by a plurality of frame units which are assembled together in series and each of which includes a plurality of inclined screen strips disposed horizontally in overlapping relationship with the disclosed faces thereof directed downward. This arrangement insures reproduction of clear images, eliminating diffused reflection of rays. In addition, the structure comprising frame units including screen strips facililates construction of the hemispherical screen.

The present invention will be described in greater detail with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in vertical section schematically showing an image projecting assembly provided with a hemispherical screen in accordance with this invention;

FIG. 2 is a sectional view taken along the line 2—2 in FIG. 1;

FIG. 3 is a fragmentary front view on an enlarged scale showing the screen of FIG. 1, part of the screen being broken away;

FIG. 4 is a sectional view taken along the line 4—4 in FIG. 3; '

FIG. 5 is a sectional view taken along the line 5—5 in FIG. 3;

FIG. 6 is a perspective view on an enlarged scale showing a frame unit in which the method for fixing screen strips is partly shown;

FIG. 7 is a schematic front view illustrating the theoretical ground that the dead zone can be eliminated by the hemispherical screen of this invention; and

FIG. 8 is a schematic bottom view of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, a screen 1 is in the form of a sphere which is truncated below the equator E and includes a spherical or arcuate lower extension la which extends continuously downward from the equator E. The hemispherical screen 1 is fixed to a domelike building 2 which surrounds the screen 1. Formed between the screen 1 and the building 2 is a space for disposing a number of sound systems (not shown) The aimular lower portion 2α of the building 2 is provided with suitable passages serving as entrance and exit (not shown) and five projection rooms 4 having projection windows 3 and equidistantly spaced apart. A motionpicture projector 5 of the horizontal film transport type is installed in each of the projection rooms 4, the projector 5 being equipped with an equidistance projection lens or three-dimensional image projection lens. The projector 5 is disposed at each comer of a regular pentagon and is so adjusted that its optical axis L passes through the center O of the sphere defined by the screen 1. Each division A of the screen 1 which is vertically divided into five is covered by each projector 5. The space surrounded by the annular lower portion 2α of the building 2 and positioned below the screen 1 provides a place for the spectators. In order to make it easy for the spectators to watch the images projected on the screen 1, the place for the spectators is defined by a circle S indicated in two-dotted chain line in FIG. 2 which is concentric with and slightly smaller in diameter than the circle defined by the lower peripheral end of the screen 1. In accordance with this embodiment, five films are simultaneously projected on the screen with five projectors, but the number of the projectors is not critical and may be varied as desired.

Referring to FIG. 3 to 6, the spherical form of the screen 1 is provided by a number of frame units 6 which are joined together one after another vertically and horizontally, and held by support frames 7 secured to the inner wall of the building 2, the adjacent frame units 6 being inclined inward at a predetermined obtuse angle. As shown in FIG. 6, the frame unit 6 is constructed of vertical members 9 spaced apart in parallel by a given distance and having sawteeth 8 and horizontal members 10 and 11 disposed at the upper and lower ends and intermediate portions of the vertical members 9. The opposite ends of each of the horizontal members 10 and 11 are fitted into L - shaped cutouts 12 and llshaped cutouts 13 formed in the outer side of the vertical members 9 at the opposite ends and intermediate portions respectively and fixed with adhesive. The inclined faces of the sawteeth 8 of the vertical members 9 are directed downward and a screen strip 14 extends across the sawteeth 8 of the opposite vertical members 9. The opposite ends of the screen strip 14 are secured to the outer side faces of the vertical members 9 by

3,695,751 means of staples 15. The screen strips 14 are disposed in overlapping relationship with each other in the manner of Persian blinds, the screen 1 thus being composed of a great number of horizontally extending screen strips 14. More specifically, the screen 1 is 5 2,000 m² in total area and is made up of 190,000 screen strips 14, each 60cm in length and 4 cm in width. The material for the frame unit 6 may be wood, synthetic resin or metal, the most preferable being wood. The screen strip 14 may be made of a fabric, preferably a 'θ fabric woven of nylon yams. To apply the screen strips to the frame units 6, the strips are provided with moisture beforehand to allow them to expand sufficiently and the wet strips are then fixed to the frame units 6 while being kept taut and dried. The horizontal ¹⁵screen strips 14 fixed to one frame unit 6 are inclined relative to the frame unit 6, with the disclosed faces directed downward, and all of the screen strips 14 are disposed in parallel. In order to obtain clear images free 20 from diffused reflection of rays, the angle of the screen strips on each of the frame units 6 relative to the image projecting rays as each frame unit 6 is secured to the domelike building 2 is critical. This angle is so determined that all of the rays reflected by all the screen 25 strips 14 on the frame units 6 enter the circle S which defines the aforementioned place for the spectators.

For elimination of the dead zones, the lower extension la of the screen 1 must not be cylindrical but spherical as already described. The theoretical ground 30 for providing such structure is illustrated in FIGS. 7 and 8. Suppose the screen 1 is provided with a spherical extension la as shown in the solid line and a cylindrical extension lb as shown in the dotted line. The radius r' of the circle defined by the lower peripheral end of the 35 spherical extension la of the screen 1 is given by the equation r' = r cos Θ wherein r is the radius of the hemispherical screen 1, ⁴⁰namely the radius of the cylindrical extension lb, and Θ is the angle defined by a horizontal line H which passes through the center O of the sphere forming the screen 1 and by a line OX connecting the center O to the lower end X of the screen 1.

The difference d between the radius r of the cylindrical extension lb and the radius r' of the lower end of the spherical extension la is given by d=r-r'. ⁵⁰

In the present embodiment, r = 15m, and Θ — 20°, hence the above equation gives d ~ 0.9 m.

Assuming that one projector 5 covers an angle of 2 θ', the angle θ' which produces a dead zone is given by . .,, r sin 0' tan θ=—;-------r(l+cos θ'-- J

The width d' of the dead zone is defined by d' = dxtan0'.

In the case where five projectors are used for the hemispherical screen of .the present embodiment, θ' = 36 , so that the calculation based on the above equation shows that a dead zone having a width of 0.3 m is produced bn one section of the cylindrical extension lb which is covered by one projector. The same dead zone is also produced on the adjacent section of the screen. As a result, a dead zone having a width of 0.6m occurs at the boundary of the adjacent two sections of the screen.