Note: Descriptions are shown in the official language in which they were submitted.
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Apparatus for duplicating long strips of film .
onto other strips of film is used particularly in
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.~ the motion picture industry as well as in other fields. : ~.
Photographic film used presently requires with
: plural chemical steps and critical processes develop- ~.
ment porcesses, must be processed under limiting
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;:: conditions and stored in darkness and is perishable.
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; It would be desirable if contact printing methods
- could be utilized electrophotographically to duplicate
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... images on a photographic film to an electro-
photographic film carrier or other medium. Improve-
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ments both economic and in quality could be effected but
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contact would have to be effected without erasing the
latent image. However it would be expected that the
charge defining a resultant latent image would be
- thought to be dissipated by direct contact with a
conventional film negative.
Accordingly, the invention provides a method of
duplicating developed images carried on a first
strip of film onto a transparent flexible second
strip of electrophotographic film which has a coating
l of a wholly inorganic oriented crystalline photo-
conductive material on an ohmic layer which is in turn
. 15 carried on a substrate, said method including the
steps of charging the coating of the electrophoto-
graphic film in darkness independently of the first
. strip, projecting a beam of radiant energy to the
strips to produce on the coating a latent image and
toning and optionally fixing the toned image in
i darkness independently of the first film strip: the
first and second film strips being moved into face
to face engagement after charging of the coating, the
beam being projected through both strips while same
are engaged and the film strips being separated before
. the latent image on the electrophotographic image is
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toned, optionally thereafter fixing the toned image
in the second strip or transferring the toned image
to strips of blank film.
Further the invention provides apparatus for
. 5 duplicating images on an elongate first film strip
onto an elongate second strip formed of electro-
photographic film, the apparatus including a supply
of first film strip having a succession of developed
images thereon and first means for transporting the
film to first take-up means, a supply of electro- :-
photographic film strip having a photoconductive
coating thereon and second means for transporting
the electrophotographic film to second take-up means,
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: means defining a darkened chamber, means for guiding
the both film strips into and thereafter out of the
chamber before same are directed to their respective
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: take-up means, a charging station in the chamber and
having means for charging the coating of the electro-
photographic film strip uniformly while same passes
. 20 said charging station, a projection station including
' means for projecting a beam of radiant energy through
both film strips while in said chamber, and a toning
station in the said chamber including means for.
toning the latent images produced on the electrophoto-
graphic film strip after passing through said projection
station; said first and second transporting means
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including means for bringing the strips of films both
into intimately engaged contact while in said chamber
and moving at the same rate and in the same direction
after the electrophotographic film strip has passed
the charging station, the film strips being in contact
while the beam passes therethrough, and said first
and second transporting means also including means
for separating the film strips after the projection
station and before the electrophotographic film
. 10 passes through said toning station and optionally,
.. a fixing station.
~ Additionally, the invention provides a contact
;~l film duplicator for duplicating the images of an
elongate strip of photographic film onto another
medium in a continuous process which comprises means
. for progressively bringing a limited area of an elongate
strip of imaged photographic film into face to face
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: engaged contact with identical area of an elongate
strip of electrophotographic film in a continuous
progression of such limited areas along the lengths
` of the respective films and including means for
maintaining the films in darkness at their contacting
areas, means for charging each said limited area of the
electrophotographic film in darkness before it is brought
into contact with its counter part area of the photo-
:. graphic film, means for projecting light through the
films from the side of the photographic film to produce
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a latent duplicate image of the limitea area of
the photographic film on the electrophotographic
film, means for moving the films apart immediately
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after they have been engaged and the latent image
has been formed, means for toning the latent image
in darkness after the films have moved apart, and
means for accumulating the electrophotographic f ilm
after the operation of the toning means.
The preferred embodiments of this invention will
10 now be described, by way of example, with reference-
to the drawings accompanying this specification in
which:
Figure 1 is a block diagram of apparatus
constructed in accordance with the invention, and
Figure 2 is a modified form of the invention.
The apparatus of the invention is illustrated in
Figures 1 and 2 diagrammatically. The film 10 which
` carries the images that are to be reproduced is
conventional silver halide photographic film provided
~0 at supply 14. The film 10 normally is perforated and
~;~ transported through the use of sprocket wheels such as
shown at 24 in order to prevent any contact with the
.` soft photographic emulsion. In transporting the film
10 through the apparatus, the emulsion side preferably
is arranged to face the coating side of the electrophoto-
~' graphic film. The take-up reel and mechanism for the
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photographic film is shown at 16. The film 10 can be
cinematographic, micro~ilm, microfiche, a series of
stills, etc.
The electrophotographic film 12 is supplied from
a suitable reel 18 and it can be transported by
sprocket wheels as well. However, the film 12 has an
abrasion-resistant surface so this is not mandatory.
Transport idlers are shown at 25,
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The film 12 is based upon a strip of transparent
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polyester resin substrate about .005 inch thick and
has an ohmic layer deposited on its surface ana well-
bonded thereto. The ohmic layer is made up of indium-
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~ tin oxide and is about 300 Angstroms thick and trans-
; parent. The ohmic layer has a coating of photo-
conductive material on its surface and hence the ohmic
layer can be described as sandwiched between the photo-
conductive coating and the substrate. The photoconductive
- coating is a sputter-desposited, wholly inorganic,
highly oriented crystalline material in which the
crystals are arranged parallel to one another and per-
pendicular to the plane of the substrate. The coating
is transparent to a degree whereby it absorbs between
15 and 30% of white light. It has a quantum efficiency
that is at least 100 times greater than those of known
photoconductive materials. It has high speed, a
resolution that is greater than known photographic film
and is panchromatic. It has an almost infinite surface
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resistivity due to the formation of a barrier layer
on the surface during the sputtering of the material.
When deposited it is electrically anisotropic in that
, its resistivity along the axes of the crystals, that
S is perpendicular to its surface, is very much less
than its surface resistivity. It can be charged with
a surface potential that gives a substantially greater
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field than known photoconductive materials and dis-
charges to zero by white light, with an almost infinite
intermediate grey scale.
~` The preferred coating material is cadmium sulfide
;, of extremely high purity. Zinc sulfide, arsenic
- trisulfide and mixtures of cadmium sulfide with zinc
sulfide have proauced excellent coatings. Different
~` l5 spectral characteristics result from different materials.
The film 12 passes through the apparatus with its
coating side facing the emulsion siae of the photographic
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film 10.
; The electrophotographic film 12 first is charged
~0 station 42, then brought into contact with the film 10
at a projection station 22 where light from the lamp 36
is projected by way of a simple collimator or the like,
designatea optics 38, through the engaged films The
charged coating of the film 12 is imaged to provide a
'5 latent image which moves to the toning station 46 where
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it is toned and thereafter fixed at a fixing station 54
by some means such as a heat lamp. Spray coating may be
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used. Where the toner used is self-fixing, the fixing
station 54 can be omitted. The film 12', now provided
` with the exact duplicate of the images on the photo-
; graphic film 10 is taken up on the t~ke-up reel 20.
The reproduced film 10' is taken up on the take-up
reel 16 and thereafter may be salvaged to recover
the silver therefrom.
The charged film 12 has the charges so strongly
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bound thereto because of the nature of the coating
; 10 that there is no loss of charge when the coating
~; contacts the film 10. Furthermore, there will be
little or no loss of the latent image when the films
separate after leaving the projection station 22,
; this being done at a lubricating station 40. The
material which is applied to the film is a liquid
hydrocarbon that is insulating in character and serves
several purposes. It wets the film 12 and causes intimate
adherence of the film 10 thereto during passage of
i the contacting films through the projecting station 22.
- 20 The coated surface of the film 12 preferably is lubricated
before being charged and passing through the projection
station 22, this being done at a lubricating station 40. ~
The material which is applied to the film is a liquid ~`
` hydrocarbon that is insulating in character and serves ~`
: ~5 several purposes. It wets the film 12 and causes
intimate adherence of the film 10 thereto during passage
of the contacting films through the projection station 22.
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~ It prevents any possibilit~ of scratching either
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film and is anti-static in that it prevents the
buildup of static charges by virtue of the coming
` together and separating of the films. Thus, there
is no wiping off of the latent image of the electro-
; photographic film after it has been formed by such
static charges. Additionally, it is optically better
;i than an intervening layer of air because its index
of refraction is less than that of air.
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In connection with the latter function of the
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liquid hydrocarbon, it should be understood that even -
' the most intimate mechanical contact between two film
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~, surfaces is bound to include a thin layer of air. The
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~ presence of hydrocarbon excludes air and substitutes
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,'~ 15 a microscopic film of material therefor which has
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better optical transmission properties than air because
diffusion, scattering and bending are decreased.
A preferred lubricating material is sold under
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the trademark Isopar G by the Exxon Company of Houston,
Texas. There is complete compatibility between the
lubricant and the toner at the toning station 46. The
lubricant is applied at a lubricating station 40 by
means of any suitable device, such as a fountain 41 with
transfer rolls, the last one of which contacts the
coating side of the film 12. Lubricant can be applied
by spraying at the point 40' after the film has been
chargedO
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, Adjustment of the film strips to move fairly
synchronously can be achieved by well-known means
such as the adjustable loops 24' and 25' or the like.
~ The average density of the images on the film 10
- ~ can be detected by means of the lamp 28 and photocell
26 to provide a signal on the line 56 that can be
compared with a signal from a reference source 64
appearing on the line 62 in the differential amplifier
60 to control the charging of the film 12. The output
0 of the amplifier 60 appears at 66 and varies the output -
of the charge voltage control circuit 68 which is applied
through delay circuit 74 to the charging apparatus,
'~ which can be a corona or similar device. The power
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supply for the charge voltage control circuit is shown
at 70. The delay 74 is to give the image of the film
10 whose density is being measured sufficient time to
~; reach the projection station 22, if necessary.
, The film 12 has a sensitivity which varies in
accordance with its surface potential. The alternative
to utilizing a reference signal is the use of a signal
derived from a measurement of the surface potential of
the charged film. Thus, the density of the image on
the photographic film 10 is measured and compared with
the surface potential of the film 12. When the potential
~5 on the film rises to a value which produces a signal out
of the circuit 49 on the line 51 which has been pre- `
determined to represent the ideal sensitivity of the film 12
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for the particular lighting conditions of the lamp
, 36 to produce the density measured for the particular
image, the charging stops. This form of the invention
is a circuit different from that which uses a reference
signal, but the circuitry block diagram readily is
represented by moving the arm of the switch Sw 1 to the
~ contact of the line 51.
,~ The charging station 42, projection station 22
and the toning station 46 of Figure 1 are enclosed
`~ 10 all in a suitable housing indicated by the broken line
80 to maintain those elements involved in darkness.
The film strips 10 and 12 can be moved intermittently
or continuously.
There is considerably more information on exposed
~15 photographic film than can be derived from ordinary -
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~ viewing, printing or projecting of the same. Computers
`' and other sophisticated apparatus can synthesize this
information by techni~ues which are not involved here.
The invention herein does, however, derive ~uality
. !0 information from the film and automatically produces
a better ~uality duplicate than the original film.
This is done by the measurement of density and relation
of this information to image enhancement by controlling
the charge as explained above. This is effected because
~5 of the variable sensitivity of the electrophotographic
film 12.
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The electrophotographic film 12 as used
preferably is one in which there is a coating of
inorganic material and most minerals have characteristic
colors in crystalline form. For example, the color
of caamium sulfide is a light yellow. If a duplicate
film 12' is made directly on the film coating by
fixing the toned image, the making of prints from this
film 12' does not pose any problems. If, on the other
hand it is to be projected, the background will be
~;; l0 yellow unless filters or film treatment are used.
Furthermore, economical as this film 12 is, it is not
as economical as clear base film of some polyester.
As illustrated in Figure 2, the toned image can
be transferred in Figure 2, the toned image can be
L5 transferred to a strip of clear base film and the
; electrophotographic film cleaned and reused over and
over. Such apparatus of Figure 2 is auite similar to
that up to the toning station 46 where, instead of
; passing to the fixing station, the film 12' carrying
~0 the toned image passes to a transfer station 84 where
the image is transferred to a strip 13 of clear base
film that is stripped off a clear base film supply 82.
The transfer station 84 is located in the darkened
enclosure 80 and comprises a pair of pressure rollers
'5 86 and 88 which bring the strips 13 and 12' into the
nip of the rollers. The toner is picked up from the
film 12' and passes to the fixing station 54 and there- -
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after is accumulated onto a take-up reel 90.
; Obviously, the toner should not be of the self-
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` fixing type, or if it is, the process of drying
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~ should not take place until after transfer.
i 5 As for the film 12', after the toned image has
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, been transferred, the film is cleaned in any suitable
manner at the cleaning station 92. It could for example,
be sprayed and/or rinsed by the same hydrocarbon used
to lubricate the film at 40. This would dissolve
whatever toner remained. There could be squeegee -
means, brushes to brush off dried toner, etc. A
brilliant lamp could be used to discharge any
remaining electrical charge on the coating. In any
event, after cleaning, the film 12 is no different
from the film which is shown being stripped off the
supply reel 18 in Figure 1 and hence can be used again.
Since the electrophotographic film described above does
- not become electrostatically fatigued, it can be reused
as many times as its coating mechanically can withstand
the wear thereon.
After economy, one of the benefits of transferring
- to blank film is that the toner, being made of carbon
and resin particles, is inexpensive, certainly a lot
cheaper than the silver halide emulsions of photographic
; 25 film.
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