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Патент USA US2117737

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May 17, 1938.
E. MAY
2,1 17,737
ILLUMINATING MEANS FOR PROJECTION APPARATUS
Filed June '2, 1936
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INVENTOR
Patented May 17, 1938
2,117,737
UNITED STATES PATENT OFFICE.
2,117,737
ILLUMINATING MEANS FOR PROJECTION
APPARATUS
Erwin May, Wetzlar, Germany, assignor to Ernst
Leitz, G. m. b. IL, Wetzlar, Germany
Application June 2, 1936, Serial No. 83,007
‘
In Germany July 15, 1935
3 Claims.
The object of this invention is to provide certain
improvements in the illuminating means for pro
jection apparatus embodying an arrangement in
cluding the use of electric ?lament lamps where
5 by the image of the ?laments is formed in the
plane of the picture instead of in the objective as
is the case in prior'disclosures. In the art it is
known that the image of the source of light in
projection apparatus may be formed in the plane
of the picture if arc lamps are used. But where
?lament lamps are used it has hitherto not been
(01. 88-24)
window 13 as will be understood.
jecting objective and IS the screen.
I4 is the .pro
It indicates
a rotating shutter if such is used.
_ Rays from the lamp ?laments striking the ring
formed mirror 8 will be re?ected back and form 5
offset images of the ?lament'threads in the plane
of the ?lament as indicated by small dotted
circles, the re?ected images of the ?lament
threads being interposed between the ?lament
threads themselves to provide an enlarged light 10
source in the plane of the ?lament. The rays
from the light source or lighted area thus formed
?laments in the plane of the picture because the are in turn re?ected by the hollowmirror 6 in the
?laments do not form an evenly lighted surface, - plane of the ?lm or picture [2. Because of the
l5 or area. Hence, in prior disclosures, the image
fact that the. hollow mirror 6 has a more or less 15
, possible or practical to form the image of the
of the ?lament is formed in the objective although
?nely grained, not smooth, re?ecting surface ‘I,
~ such an arrangement does not provide the best
thejmages of the ?laments and of the displaced
re?ected images of the ?laments are re?ected in
possible illumination for projection purposes, it
being. known, that maximum illumination is ob
- 20 tained only if the image of the light is formed in
the plane of the picture to be projected;
the plane of the ?lm or picture [2 in a manner to
completely blend and diffuse the separate ele- 20
ments of the source of light so that an even uni~
paratus for utilizing the full illuminating power of
form illumination of the picture and ?lm is ob
tained and the individual images of the several
the light source from an electric ?lament lamp by
illuminating elements disappear.
The object of the invention is to provide an ap
25 forming the image thereof in the plane of the pic
ture. Accordingly the invention is embodied in an
arrangement or construction including an electric
?lament lamp the light of which is re?ected by a
hollow mirror having a slightly grained surface
so providing diffused or blurred re?ection of the ?la
ment. ' In addition, the invention includes the use
If desired, a condensing lens ii may be inter- 25
posed between the lamp and the ?lm, the lens
having such a focal length and being so propor
tioned and placed that it forms an image by re
fraction of the two adjacent ?lament threads
such as 3 and 4 into the plane of the ?lm in such 30
a manner that the re?ected images thereof lie at
of a ring formed mirror for producing a laterally
displaced re?ected image of the ?lament in its
own plane whereby a diffused or spreading light
35 is obtained in the light source itself. A further
object of the invention is to provide a condensing
lens in front of the ?lament so arranged that
the light rays of two adjacent ?laments are
the edges of the ?lm i2 and thus illuminate the
side portions of ‘the ?lm to compensate for the
speci?cally directed toward the edges of .the ?eld
prevent themjrom being noticed in the picture.
4c of the picture to compensate gforv a weakening or
lessening of the light strength at the edges of the
picture and whereby even uniform light is pro
vided.
'
The invention is illustrated diagrammatically
' in the accompanying drawing in which an elec
tric lamp i is provided with a number of ?la
ments. In the present instance and by way of an
example there are four separate threads in the
?lament marked i, 3, ii and 5. ii is a hollow re
?ecting mirror having a slightly grained re?ect
ing surface ii. a is a ring formed mirror the axis
9 of which is slightly offset from the optical axis
it of the system. H is a condensing lens placed
between the lamp i and the picture, slide or ?lm
55 it which is placed or exposed through a ?lm
usual decrease or diminution in the illumination
of the side portions which otherwise takes place 35
or occurs. The condensing lens may have a
grained surface as at i8 whereby to cause a
blurred re?ection of the two ?lament threads to
However, even without such grained surface of 40
the condenser, the image of the two separately re
?ected ?laments practically disappears in the re
?ected light from the hollow mirror.
With an arrangement or system as herein dis
closed a re?ected offset image of the ?lament of 45
the lamp‘is formed in the plane of the ?lm and.
the entire area of the ?eld of view of the pic
ture is uniformly illuminated under ‘utilization of
the full illuminating strength of the source of
light.
It is understood of course that the term 50 '
?lm is used to indicate a picture or illustration
to be projected.
I claim:—-
‘
1. An apparatus for illuminating a_?lm or pic
ture to be projected upon a screen comprising an /
2
2,117,737
incandescent lamp having a plurality of sepa
rated parallel ?lament threads in a single plane,
so related with respect to the lane of the ?la
ment and offset with respect to he optical axis of V
a spherical re?ector to one side of the lamp be
tween the latter and the screen having its focus
so related with respect to the plane of the ?la
the apparatus that it forms o?set images of the
?lament threads between the latter in the plane
ment and offset with respect to the optical axis
of the apparatus that it forms offset images of
the ?lament threads between the latter in the
side of the lamp having a?nely waved irregular
re?ecting surface for re?ecting the illumination
emanating from the ?lament and from there
of the ?lament, a concave mirror on the opposite
plane of the ?lament, a concave mirror on the - ?ected o?fset images of the ?lament threads upon
10 opposite side of the lamp having a ?nely waved
irregular re?ecting surface for re?ecting the il
lumination emanating from the ?lament and
_ from the re?ected offset images of the ?lament
threads upon the ?lm, the focus of the said re
16 ?ecting mirror being so related with respect to
the ?lm that a diffused blended image of the ?la
ment and of the re?ected images of the ?lament
threads is formed in the plane of the ?lm.
the ?lm, the focus of the said‘ re?ecting mirror
being so related with respectto the ?lm that a
diffused blended image of the ?lament and of the
re?ected images of the ?lament threads is formed
in'the plane of the ?lm, a condensing lens be
tween the lamp and the ?lm a predetermined
distance from the lamp whereby to cause the
images of two adjacent ?lament threads in said
lamp to be formed in the plane of the ?lm at the
side portions thereof, one ?lament thread image
at each side.
3. An apparatus according tocIaim 2 in which
2. An apparatus for illuminating a ?lm or pic
ture to be projected upon a screen comprising an
incandescent lamp having a plurality of separated
parallel ?lament threads in a single plane, a the condensing lens has at least one ?nely waved
spherical re?ector to one side of the lamp be
irregular lens surface.
tween the latter and the screen having its focus
ERWIN MAY.
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