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Патент USA US2130704

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Sept. 20, 1938.
Filed Dec. 16, 1936
, 2,130,704
Patented Sept. 20, 1938
2,130,704 I
Karl Platzwaldt, Gladbach-Rheydt, Germany
Application December 16, 1936, Serial No. 116,216
In Germany October 11, 1934
5 claims. (Cl. 88-24)
This invention relates to a projection screen
for exhibiting cinematograph pictures with a
spraying said particles on to the surface of the
screen, namely by passing the spray-gun apply
sound accompaniment said screen having pores
for the passage of sound, and aims at improving
5 such a screen in both the acoustical and the opti
cal respects.
Projection screens are already known in the
smooth material of which pores are formed for
the passage of sound. On the other hand, it
10 has also already been suggested that non-porous
projection screens should be provided with a
patterned surface, that is to say, a surface di
vided into raised polygons, which gives good re
sults from an optical point of view.
ing the adhesive over the screen at such an‘
angle to the latter that the portion of the back
ground material lying'in the center of the vari- 5
ous structural divisions of the front material is
protected against the sprayed liquid, in the di
rection of the spray, by the threads of the pat
tern-forming open mesh fabric, so that such por
tion of the background remains practically free 10
from refracting or re?ecting particles.
In this way a projection screen is produced
which, owing to the coating of ?ne particles of
The present invention provides a projection
crystal, presents the most favourable optical
properties obtainable, without loss of the acoustic l5
advantages afforded by the porosity. The re
screen advantageous for sound transmission, hav
fracting or re?ecting particles are deposited in
ing a raised patterned surface with one or more the individual structural cells approximately
pores at the base of each of its separate struc
over a surface sloping towards the porous back
tural divisions. In this way the projection screen ground, and thus form in each cell a kind of 20
20 is not only made permeable to sound, but the concave reflector. This increases the lateral
manner in which the sound passes through the diffusion of the light re?ected by the screen,
screen is facilitated and improved, since the and gives a diffuse, picture-softening light, and
structural divisions act as small horns for the also illuminates the corners of the screen which
sound-waves passing through the pores of the would otherwise be darker, thus providing a 25
25 screen and thus amplify and uniformly dis
practically uniformly bright picture. The pow
tribute such sound-waves. At the same time erful reflecting properties of this screen also make
the superiority of the patterned surface as com
it particularly suitable for color ?lms.
pared with a smooth screen, from an optical point
-The manufacture of the porous projection
of view, is in no way affected by the pores at screen of the present invention coated with re- 30
fracting or re?ecting particles presents no dif
30 the base of the structural divisions.
The favourable optical effect of the screen of ?culties,‘ inasmuch as by spraying at an angle
the present invention can be substantially in
it is possible to apply said particles in a simple
creased and improved by coating the screen sur
and yet reliable manner without stopping up the
face with ?ne, optically refracting or re?ecting pores in the screen and thus affecting the per- 35
35 particles for example so-called crystal particles. meability to sound of the latter, and also to ap
If such particles be applied to a plain sound ?lm portion exactly and distribute uniformly said
screen provided with pores, there is a danger particles on the surface of the screen. At the
of the particles stopping up and blocking the same time ?rm and lasting adherence of the
pores, at least to 'a large extent. This danger refracting or reflecting particles to the screen,
40 can be avoided or very substantially minimized
in accordance with the invention by applying
the crystal refracting or re?ecting particles to
a porous screen having a patterned surface.
In such a screen, consisting of a pattern-form
45 ing open mesh fabric and a porous screen back
ground, the refracting or re?ecting particles can,
moreover, be deposited solely on the front
meshed fabric and in the horns formed by the
meshes of the'front fabric and the background
50 material, while the pores in the background ma
terial are left free approximately in the center
of the individual structural divisions. This can
be achieved by a suitable method of spraying
the adhesive serving to secure the refracting or
55 re?ecting particles to the screen, and also of
even when the latter is bent, rolled or folded, is
The optical effect of a porous screen coated
with retracting or re?ecting particles and hav- 45
ing a patterned surface can be considerably en
hanced by the use of particles having a flat, pref
erably concave or convex, form.
In this way
great lateral diffusion of light and uniform dis
tribution of light illuminating the corners of the 50
picture is achieved, whilst the lining of the struc
tural cells in the form of concave re?ectors with
the pores in the background left unobstructed,
is considerably facilitated. In addition the pic
tures shown on the screen are given a very fa- 55
vourable relief e?ect and an almost real stereo
scopic illusion.
and at the same time form a'kind of small con
cave re?ector for the incident light rays.
Having now particularly described and ascer
l. Sound-permeable projection screen for pic;
ture and sound ?lms comprising two superposed
and inter-connected fabrics, one of said fabrics
fabric, can be used.‘
In order more clearly to understand the inven-_
tion, reference is made to the accompanying
drawing. which illustrates diagrammatically and
section, both on an enlarged scale.
The screen consists of the porous background I
are joined
example similar in shape to single or double con
vex or concave lenses. These refracting or re
?ecting particles 3 can consist of metal or glass
by rubber
solution, or by sewing. The double-ply screen
beads, particularly of crystal glass beads, chromi
um-plated glass beads or metal beads polished to
a high gloss.
nel-iike formations around said free center por
2. A screen according to claim 1, wherein the
light dispersing particles have a ?at globular
3. A screen according to claim 1 in which .the
light dispersive particles are light re?ective.
according to claim
fabric‘! and the background I, and leave unob
in the background which
i are approximately in
the center of the various
structural panels. They lie around these pores
on a surface arched towards the background I,
and thus form, as'it were, diminutive sound horns _mesh fabric, the pores of which
for the sound waves passing through these pores, sound transmission.
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