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Dec- 24, 1946-
s. c. CORONITI
PHOTOGRAPHIC APPARATUS
Filed July 28, 1943
2,413,218
2 Sheets-Sheet 2
56a
(6
41>".
47'
Jm ‘a 6I C
m@
a
m
Vm
BY
ATTORNEY
Patented Dec. 24, 1946
2,413,218
UNITED STATES
PATENT OFFICE‘
2,413,218
PHOTOGRAPHIC APPARATUS
Samuel C. Coroniti, Cambridge, Mass., assignor to
General Aniline & Film Corporation, New York,
N. Y., a’corporation of Delaware
Application July 28, 1943, Serial N0. 496,383
16 Claims.
1
This invention relates to photographic appa
ratus, and more particularly ,to electronic means
for controlling the exposure of a ?lm as a func
tion of the optical density of the ?lm.
In a continuous process for treating motion
picture ?lm, the latent image, produced on a ?lm
exposed in a camera, is developed into a silver
image, producing a negative transparency. In a
continuous process for ?nishing motion picture
(01. 95-75)
2
Fig. 3 is a simpli?ed electrical diagram of the
fundamental components of the control circuit.
Fig. 4 is a set of curves illustrating voltage rela
tions of the circuit of Fig. 3.
Fig. 5 is a vector diagram of the current and
voltages of the circuit of Fig. 3.
Generally speaking, in the present invention
a ?lm which has been exposed in a camera and
then developed, and bleached, is moved longi
?lm, the latent image produced by exposure of} 10 tudinally past an element e?ective to measure »
the ?lm in a camera, is ?rst subjected to devel
the optical density of the ?lm. After passing
opment such as would normally produce a nega
this element, the ?lm is moved past a variable
intensity light source. The optical density meas
the ?lm is bleached, that is, is so treated as to
uring element, through electronic means, con
remove the metallic silver formed by the ?rst 16 trols the intensity of the variable intensityllght
development. It is then reexposedthereby ren
source. A constant intensity light source may
dering the remaining silver bromide developable.
be provided to give a predetermined basic ex
That. positive latent image is developed, ?xed
posure to the ?lm which is additive to the ex-‘
and washed. Thus, by so-called reversal devel
posure given by the variable intensity light
opment, a positive image is formed on the orig 20 source. The provision of the constant intensity
tive transparency. Without ?xing that image,
inal ?lm.
.
'It is among the objects of this invention to
provide an improved photographic apparatus for
the continuous treatment of motion picture ?lm;
to provide photographic apparatus for control
ling a second exposure of a motion picture ?lm
as a function of the optical density of the ?lm
light source is not a necessary feature of the
vpresent invention. Such constant intensity light
may be provided by arranging the variable in
tensity light source to have a minimum or basic
85 intensity at all times, or may be provided by a
separate light source. Means are provided for
delaying the effect of the measuring element on
the variable intensity light source for a sumcient
period of time to permit the ?lm to travel from
30 a point adjacent the measuring element to a
after its ?rst development; to provide apparatus
for controlling the secondexposure of a motion
picture ?lm including an element for measuring
the optical density of the ?lm and electronic
point adjacent the variable intensity light source.
means cperatively associated with the element
The light measuring element controls the in
for varying the intensity of such second exposure
.tensity of the ?lm exposure through a novel elec
as a function of the optical density of the ?lm;
tronic control circuit.
to provide photographic apparatus including an 35 Referring to Fig. 1 of the drawings, the photo
element for measuring the optical density of film
graphic apparatus includes a light proof housing
passed thereover, electronic means controlled by
Ill subdivided by partitions HI and 52 into com
the element for varying the intensity of the sec
partments iii, ill and it. An intermediatewall
ond exposure of the ?lm and means for delaying
it of the housing iii is formed with three aper
the e?ect of the measuring element on the elec 40 tures l'l, it and it, each disposed centrally of
tronic means for a period of time sufficient to
one of the compartments it, ill and 55. Housing
permit the ?lm to travel from the measuring
it is formed with an extension 26 opposite the
. element to the point where it receives its second
compartment i3 and with an outer wall 22 spaced
exposure; and to provide an improved electronic
from the wall iii. Walls it and 22 form a tunnel
45
control circuit.
through which passes the ?lm 2t which is to be
These and other objects, advantages and fea
given a second exposure.
tures of the invention will be apparent from the
A relatively small constant voltage lamp 25
following description and accompanying draw
is mounted in housing l3. The light from lamp
‘ ings. In the drawings:
25 is directed by a mirror 23 through aperture
Fig. 1 is a vertical sectional view through one 50 ii upon a photoelectric cell 30 mounted in exten
form of apparatus embodying the principles of
the invention.
.
Fig. 2 is a diagrammatic representation of the
apparatus shown in Fig. 1, and a control circuit
associated therewith.
sion 2!. The particular photoelectric cell illus
trated is responsive to farred and infrared rays,
and has a substantially linear response to such
. rays. A red light ?lter 213 is mounted in brackets
55 26 adjacent aperture ill and a matte base it is
2,413,218
inserted in aperture H. A variable voltage lamp I
to conductors 31. A substantially constant direct
35 is mounted in compartment/l4 and is adapted
current potential for the control circuit is sup- »
to give a variable intensity exposure to ?lm 28
plied by any suitable source of direct current. »
through aperture is. If desired a constant volt-.
agelamp to may be mounted in compartment
While a battery 50 has been indicated, it will be
understood that the direct current energy may
be obtained from alternating current source 88
through a suitable recti?er, with the use of ?lters
and‘ a voltage regulator. Positive terminal ‘5i of
direct current sourcetd is connected in series
with a voltage divider comprising ?xed re
sistances 52 and 53. From the Junction 55 oi
these resistances, a voltage is applied to anode
55 of photoelectric cell 30 through a resistor 58,
E5 to give a constant intensity exposure to ?lm
20 through aperture IS. The control of these
lamps will be described more fully hereinafter.
The ?lm 28 travels in the direction of the arrow
shown .in Fig. 1. The ?lm ?rst passes over a
roller 28 and then between walls It and 22. At
the opposite end of the housing, ‘?lm 2B is
threaded over a second roller 3|. The ?lm is
maintained in constant spaced relation with re
spect to light 25 and photoelectric cell 30 by
means of a guide bracket 32 which presses the
and a conductor 57.
'
Cathode 58 of photoelectric cell 38 is connected
by conductor iii to control grid 52 of a thermionic
?lm\against spaced rollers 38, 34 as the ?lm
ampli?er tube 60. For a purpose to be described,
passes aperture i1.
a condenser 63 and a resistance 85 are connected
'
‘
The operation of the apparatus and the con
to conductor Si in parallel with each other. The
trol mechanism thereof, will be more apparent 20 opposite ends of condenser 63 and resistor $13
from a consideration of Fig. 2. In this ?gure,
are connected by a conductor 55 to ground. A
the elements shown in Fig. 1 have been given the
suitable bias voltage for grid 62 of tube 58 isv
same reference characters.
Before passing
derived from the adjustable terminal 65 of re
through the apparatus of the invention, ?lm 20
sistor or potentiometer 51, connected by a con
will have been processed to a permanent or to
ductor 68 to positive terminal 5i of direct current
a bleached image before reaching the roll 28.
source 50, through conductor ‘i8. .
It then passes in front of aperture H at which
The anode-cathode circuit of the ampli?er tube
point light rays from lamp 25 pass through ?lter
58 is connected to the grid circuit of a grid con
2d and base 21 on to photoelectric cell 38.
trolled gaseous space discharge tube ‘i?, such as
Through the control circuit shown in Fig. 2, the 30 a thyratron tube. In a manner to be described,
operation of which will be described more fully.
ampli?er tube 6!] is e?ective in varying the phase
photoelectric cell 30 controls the intensity of
relation of the voltages applied to the grid and
illumination of variable intensity lamp 35. Thus,
plate, respectively, of discharge tube 15. A con
as ?lm 20 passes aperture IE, it receives an ex
ductor ‘I3 connects cathode ‘H of tube 60 to a
posure from lamp 35 which is a function of the
junction point 74. One ‘ terminal 16 of the
optical density of the ?lm as measured by photo
secondary ‘winding ‘ll of transformer 86 is con
electric cell 38. Generally, the intensity of the
nected to junction point 14 through a ?xed con
second exposure given by lamp 35 should be an
denser 88. Grid electrode 8| of tube 15 is con
inverse logarithmic function of the optical
nected to junction point 14 through a grid cur
density of the ?lm as measured by photoelectric 40 rent limiting resistor 82. The anode or plate 83
cell 30 for reasons apparent to those skilled in
of thermionic ampli?er 60 is connected to the
the art. The control circuit includes means for
opposite
terminal 84 of secondary winding Tl
delaying the response of lamp 35 to the measure
through
a
current limiting resistance 86.
ments of photoelectric cell 30 for a period of time
The cathode 81 of thyratron tube 15 is con
su?icient for a given point on the ?lm to move
nected to the mid point 88 of secondary winding
from aperture ll to aperture l8.
Ti. Plate 90 of tube 15 is connected by a con
After passing aperture i8, ‘?lm 20 may be
ductor 91 to one terminal of lamp 35. The op
given a constant predetermined basic exposure
posite terminal of lamp 35 is connected through
at aperture i9 from constant intensity lamp 80,
if desired. However, the lamp $0 is not necessary 50 conductor 92, ?xed resistance 93 and fuse M to
terminal 85 of secondary winding ‘H. For a pur
to the practice of the present invention. The
pose to be described, the screen grid electrode
?lm then passes over roller 3!, after which it is
95 of ampli?er tube 60 is connected through a
again developed, ?xed and washed to form a
limiting resistor 96 to plate 83, and a fixed re
positive image on the ?lm. Subsequent to such
sistor 9'! is connected across the output of ampli
treatment, the ?lm may be examined in any
?er 6G.
well known manner and is then ready for use in
The operation of the circuit illustrated in Fig.
a projector.
2 is effective to vary the illumination of lamp 35
~ Lamps 25, 35 and (ill are energized from a
in accordance with the amount of light falling
suitable source of alternating current 36 which
is connected to conductors 31 through a switch (ll) on photoelectric cell 30 from lamp 25 as ?lm 20
passes~aperture I1. It will be noted that the
38 and a fuse 4|. Lamp 25 is operated at a
voltage applied to grid electrode 8| of discharge
lesser voltage than lamps 35 and 40. It is there
tube ‘I5 is derived from junction point ‘I4.
fore connected to the secondary winding 42 of a
Junction point ‘H5 is the connecting point be
step-down transformer 43 connected to conduc
tween ampli?er tube 80 and condenser 80, which
tors 37. The energization of variable intensity
are thus connected in series with the secondary
lamp 35 is controlled by the electronic control
winding ‘ll of transformer 46. The internal re
circuit as will be presently described. Constant
sistance of ampli?er tube 80 is dependent upon
intensity lamp an is connected across conductors
the voltage applied to its grid electrode 62. Thus,
31 and has a variable resistor 44 in series there
with condenser 80 being relatively ?xed, varia
with, so that the predetermined basic intensity
tions in the voltage applied. to grid 62 will vary
of lamp 48 may be selected to give a desired
the internal resistance of ampli?er tube 80.
basic exposure to ?lm 20.
Alternating current'energy for the control cir
This, in turn, will vary the phase of the voltage
applied to grid 8| with respect to the voltage
cuit is derived from a transformer 46 having a
primary winding 4'! connected by conductors 48 75 applied to plate 98 of thyratron 15. The plate
5
2,418,218
voltage is derived from the same alternating cur
rentreference source as is the grid voltage.
The voltage across secondary winding 11 is the
vector sum of the voltages across ampli?er tube
60 and condenser 80. The input alternating volt
age between the grid and the cathode of thyratron
‘I5 is constant in magnitude as will be made
apparent hereinafter. However, the phase rela
tion of the grid to cathode voltage with respect to
the output voltage of tube 15 is controlled by the
condenser 80 and ampli?er tube'iill. By varying
the output of ampli?er 60, the phase relation of
6v
.
plished by a time delay circuit including con
denser B3 and resistance 64 which are connected
in parallel with the control grid 82 of ampli?er
tube 80 and photoelectric cell 30. By proper
selection of the relative sizes of condenser 63
and resistance 64, the proper time delay in the ‘
impression of the control signal from photoelec
tric cell 30 on the control grid 62 of tube 60 is
obtained.
.
Figs. 3, 4 and 5 diagrammatically illustrate the
general principles underlying the electronic con
trol action of the present invention. The con
trol circuit in a simpli?ed form is illustrated in
. Fig.3. For reference, the points of differing po
is changed. The thyratron 15 is thus made to ?re . tential, such as the terminals of winding 11 of
at a point during each cycle of applied plate volt
‘ transformer 46, junction point 14 and mid-point
age when the instantaneous value of such input or
88 of winding 11 have been also designated with
grid voltage exceeds the critical ?ring value. The
the letters a, b, c and d, respectively. Variable
?ring oftube 15 is thus made dependent on the
intensity lamp 35 is represented by resistance
phase relation between its applied grid cathode, 20 Rp and the output eifect of ampli?er 60 by varia
or input voltage, and its applied plate to cathode,
ble resistance Rs. Also, the potential di?erences
or output voltage.
between the respective points have been desig- ,
The internal resistance of tube 60 is a function
nated Eda, Ebd, Ede and Eac.
' of the amount of light reaching photoelectric cell
In Fig. 4 are curves illustrating the operation
30. As the amount of light falling on cell 30 in 25 of the circuit through two cycles. The grid volt
creases, for instance, the current ?ow through
age Ede is represented by the broken line curve
grid resistor 56 increases. This increases the
G. The output voltage of tube 15 is represented
voltage drop across resistor 56, and thus varies
by the solid line curve P. In the instant illustra
the voltage applied to grid electrode 62 of am
tion, the grid voltage G lags the plate or output
pli?er tube 60. The internal resistance of tube
voltage P by a electrical degrees. The grid voltage
60 is thus made dependent on the amount of
G m'ust obtain a certain critical value k‘before tube
light reaching photoelectric cell 30. As men
‘l5 can become conductive or ?re. As shown in
tioned above, the output of tube 60, or corre
Fig. 4, the plate voltage obtained the positive po
spondingly its effective resistance as applied to
tential If at the time the grid attains its critical po
the input circuit of tube 15, varies the relative
tential k and tube 15 starts to ?re. Tube 75 con
phase relation between the input and output volt
tinues to ?re for the rest of the positive half cycle,
ages of thyratron tube 75. This in turn deter—
to point m. Tube 15 remains non-conducting until
mines during what portion of each cycle of ap
its plate voltage P reaches the value Z’f’, when
plied plate voltage tube 15 will be conductive.
the grid voltage G again reaches the magnitudek.
As lamp 35 is in series with the output of tube 15, 40 The tube 75 will again become conductive and re
its average intensity of illumination is accord
main conductive for the remaining half cycle to
ingly controlled as a function of the eiiective
point m’.
resistance of ampli?er tube 60. This action is
The conducting time Zn of, tube 15 may be made
. described in detail hereinafter with reference to
‘smaller or larger by varying the electrical phase
Figs. 3, 4 and 5.
displacement ¢ of the grid voltage G with respect
By selection of an ampli?er tube 60 with suit
to the plate voltage P. In Fig. 4, this would be ’
able characteristics, and by design of the param
represented by shifting curve G to the right or
eters of the circuits of tube 60, the response of
the left with respect to curve P. The maximum
lamp 35 to the control exerted by photoelectric
time for conduction of tube 15 is practically for
cell 30 may be made to bear any desired relation. 50 a complete half cycle or about 180". Thus, by
As stated above, in the present instance, the in
varying the phasedi?‘erence between the plate
tensity of illumination of lamp 35 is designed to
’ and grid voltages of tube 15, the amount of time
vary inversely, and as a logarithmic function of
during which tube 15 is conductive is correspond
the optical density of ?lm 20.
ingly varied.
'
The variation of the parameters of the circuits
Fig. 5 is a vector diagram of the relation of
of ampli?er 60 may be accomplished in any de
phase angle (1) and the grid and plate voltages
sired manner. In one practical embodiment of
Ede and Eda. The current I ?owing through the
the invention, a pentode of the type “6F6” has
resistance R; and condenser 86 here leads the
been used satisfactorily as ampli?er tube Kill. The
voltage Eba across transformer winding ‘H by an
design of the parametersof the circuits of tube 50 60 angle a. The voltage drop Eat, across resistance
is improved by the use of the screen grid resistor
RE is in phase with current I. The voltage Ecb
96 and shunt resistor 9? connected across the out
across condenser Bil lags 90° with respect to cur
put of tube Eli. In the described embodiment,
rent I. The vector sum of the voltages Esc'and
with the use of a red light ?lter 24, a red light
Ecb is equal to the total voltage Eba of the sec
responsive photoelectric, cell 30 having a linear 65 ondary ll of transformer Mi. This relation holds
response, and a pentode for ampli?er til, the cir
for all conditions. The vectors Bob and E210 make
cuit parameters necessary to produce proper cOn
a right angle with each other for all values of
trol of lamp 35 are e?ectively obtained in practice.
the angle oz. Hence the locus of point e for all
One other criterion is taken into consideration
values of on from zero to 90° will be a semi-circle
in the operation of the illustrated apparatus. It
with ?xed vector Eba as diameter.
takes a small interval of time for a given point
The voltage between grid 8i and the cathode
on ?lm 2m to move from aperture ll to adjacent
ill of tube 15 is represented by the vector Ede
aperture E8. The imposition of the control sig
which is a radius of such circle. Since the volt
nal from photoelectric cell 30 on the control cir
ages Ebd and Eda are one-half of Eba,‘ the magni
cuit is delayed for this interval. This is accom 75 tude of vector Ede is equal to that of Eta and
the input or grid voltage of discharge tube 15
with respect to the output or plate voltage thereof
2,413,218
8
cell; means for directing an image bearing photo
Eda. Vector Ede is thus constant in magnitude
for all such values of 0:.
graphic ?lm, which has been exposed, partially
Movement of vector
Ede in either a clockwise or a counterclockwise
direction will vary the relative magnitudes of the
vectors Ebc and Eca, and likewise, the phase angle
¢ between the plate voltage Eda and grid voltage
Ede. It will be apparent that either the voltage
.
developed, and bleached, successively past said
photoelectric cell and said variable intensity light
source; a light system for directing a beam of
light through'said ?lm upon said photoelectric
across the condenser 80 or that across the re
cell; a grid-‘controlled discharge device control
ling the energization of said variable intensity
sistance R; can be varied from Zero to the re
light source; a reference source of alternating
spective full v2 ues' of the transformer secondary 10 current; circuit means for applying a voltage
from said source to the plate of said‘ device;
voltage Em; and the phase angle ¢ thus varied
means, including a- capacitance and grid-con
from 0° to 180°.
‘
trolled electronic means in parallel circuit rela
Referring again to Fig. 3, either resistance B;
tion with said capacitance, for applying a volt
may be held constant and condenser 80 varied,
or vice versa, to vary the, phase relation es of the 15 age from said source to the grid of said device;
circuit means connecting the control grid of said
grid or ‘input voltage of tube 15 with respect to
electronic means to said photoelectric cell; and
the plate or output voltage thereof. As pointed
means for delaying the action of said photo
out in connection with Fig. 4, this correspond
electric cell on said electronic means in-accord
ingly varies the time interval during which tube
15 is conductive. In practice, ‘either resistance 20 ance with the spacing between said photoelectric
cell and said light source.
3. Apparatus'for use in a photographic process
comprising a photoelectric cell; a variable inten
sity light source spaced from said photoelectric
80 is held constant, and resistance Hg is elec
tronically varied by ampli?er tube 60. In turn, .25 cell; means for directing an image bearing photo
Hg or condenser 80, or both, may be varied man
ually, mechanically, electronically or automati
cally. In the illustrated embodiment condenser
tube 603 is herein automatically controlled by
photoelectric cell 38.
Variations in the conductivity or internal re
sistance of ampli?er tube 60 as controlled by the
graphic ?lm, which has been exposed, partially
developed, and bleached, successively past said
photoelectric cell and said variable intensity light
source; a light system for directing a beam of
amount of light reaching photoelectric cell 30, 30 light through said ?lm upon said photoelectric
cell; a grid-controlled discharge device control
will vary the ‘phase relationship a of the voltage
ling the energization of said variable intensity
applied to grid ill of tube 15 with respect to the
light
source; a reference source of alternating
voltage applied to plate 99 thereof.v
current; circuit means for applying a voltage
The control circuit including the time delay
from said source to the plate of said device;
means, including a capacitance and grid-con
trolled electronic means in parallel circuit rela_
an, and the load comprising lamp 35, is of gen
tion with said capacitance, for applying a voltage
eral application. That is, it may be used other
from said source to the grid of said device; cir
wise than in the speci?c case illustrated in the
drawings. Likewise, the control of photoelectric 40 cuit means connecting the control grid of said
electronic means to said photoelectric cell; and
cell 30 on variable intensity lamp 35 can be exer
means, including a resistance and a capacitance
cised through a control circuit different from that
connected in parallel circuit relation with each
illustrated, through the use of suitable equivalent
circuit comprising condenser 63 and resistance .
B4, ampli?er tube 63, discharge tube 15, condenser
electronic means.
.
other and with said photoelectric cell and the grid
It should therefore be understood that while a 4. of said electronic means, for delaying the action
of said photoelectric cell on said electronic means
speci?c embodiment of the invention has been
for the time interval necessary for a reference
shown and described, to illustrate how the princi
ples of the invention may be applied, the inven
tion is not limited thereto, but may be otherwise
embodied without departing from the principles
thereof.
I claim:
'
7
1. Apparatus for use in a photographic process
comprising a photoelectric cell; a variable in
tensity light source spaced from said photoelec
tric cell; means for directing an image bearing
photographic ?lm, which has been exposed, par
tially developed, and bleached, successively past
said photoelectric cell'and said variable intensity
point on said ?lm to travel from a point opposite
said photoelectric cell to a point opposite said
variable intensity light source.
'4. In a device for photographic printing;.means
for scanning a ?lm including a light source and a
photo-responsive element, a variable source of
_ radiation for effecting an exposure and means for
progressing ?lm past the said scanning means
and source of radiation, and means'for varying
the intensity of the source of radiation as a
function of the amount of light-falling on the
photo-responsive element which includes in cir
light source; a light system for directing a beam 60 cuit with said element, a discharge tube the out
put of which is in series with said variable source
of light through said ?lm upon said photoelectric
of radiation, a current supply for said tube, a
cell; a grid-controlled discharge device control
ling the energization of said variable intensity
light source; a reference source of alternating
current; circuit means for applying a voltage
from said source to the plate of said device;
means, including a capacitance and grid-con
capacitance in series with the voltage input of
said discharge tube, and an electronically variable
resistor effective for changing the phase angle
between the input and output voltages of said
discharge tube.
'
5. In a device for photographic printing, means
for scanning a ?lm including a light source and
tion with said capacitance, for applying a voltage
from said source to the grid of said device; and 70 a photo-responsive element, a variable source of
radiation for effecting an exposure and means
circuit means connecting the control grid of said
for progressing ?lm past the said ‘scanning means
electronic means to said photoelectric cell.
and source of radiation, and means for varying
2. Apparatus for use in a photographic process the intensity of the source of radiation as a func
comprising a photoelectric cell; a variable inten
sity light source spaced from said photoelectric 75 tion of the amount of light falling on the photo
, trolled electronic means in parallel circuit rela
2,418,218
9
responsive element which includes in circuitwith
said element, a discharge tube the output of '
which is in series with said variable source of
radiation, a current supply for said tube, a capaci
tance in series with the voltage input of said
discharge tube, and a resistor comprising a therm- '
ionic ampli?er e?ective for changing the phase
angle between the input and output voltages of
' said discharge tube.
-
10
'
tion of the amount oi light falling on the photo
responsive element which includes in circuit with
said element, a discharge tube, a current supply
for said tube, means for varying the output of
said tube including a capacitance and a thermi
' onic ampli?er, and other means forming a part
of said circuit and including a capacitance and
a resistance in parallel with said circuit by which
> the effect of changes in output current from said
6. In a device for photographic printing, means '10 photo-responsive element upon said thermionic
for scanning a ?lm including a light source and.
a photo-responsive element, a variable source of
ampli?er and on the output of said discharge tube
is delayed so that said changes shall become ef
fective only after a reference point on the ?lm
has'moved from the scanning point to the vari
radiation for e?ectlng an exposure and means
for progressing ?lm past the said scanning means
and source of radiation, and meansfor varying 15 able source of radiation.
the intensity of the source of radiation as a func
tion 01 the amount of light falling on the photo
.
10. In a ‘ device for photographic printing,
means for scanning a ?lm including a light source
and a photo-responsive element, a variable source
of radiation for e?'ecting an exposure and means
responsive element which includes'in circuit with
said element, a discharge tube the output of
which is in series with said variable source of 20 for progressing ?lm past the said scanning means
radiation, a current supply for said tube, a ca
and source of radiation, and means for varying
pacitance in series with the voltage input of said
the intensity of the source of radiation as a 'func_
discharge tube, and a resistor comprising a ther-,
tion of the amount of light falling on the photo
mionic ampli?er effective for changing the phase
responsive' element which includes in circuit with
angle between the input and output voltages of 25 said element, a discharge tube having a control
said discharge tube, said thermionic ampli?er
grid, a current supply for said tube, electronical
having a control grid, said grid having its poten
ly functioning means by which the output of said
tial varied in accordance with changes in current
tube is varied, saidmeans including a capacitance
?owing from the cathode of said photo-respon
' and a thermionic ampli?er tube having a control
sive element.
_
30 grid and plate, the output of said ampli?er tube
7. In a device for photographic printing, means
at said plate being connected with both the cur
for scanning a ?lm including a light source and
rent supply and the variable source of radiation,
a photo-responsive element, a variable source of
the control grid of said tube being connected to
radiation for effecting an exposure and means
the cathode of the photo-responsive element, the
for progressing ?lm past the said scanning means 35 circuit through said variable source of radiation
and source of radiation, and means for varying " being completed by a connection to the anode of
the intensity of the source of radiation as a func
the discharge tube.
tion of the amount of light falling on the photo
11. In a device for photographic printing,
responsive element which includes in circuit with
means for scanning a ?lm including a light source
said element, a discharge tube the output of 40 and a photo-responsive element, a variable source
which is in series with said variable source of
radiation, a current supply for said tube, a con
of radiation for effecting an exposure and means
‘for progressing ?lm past the said scanning means
and source of radiation, and means for varying
trol grid therefor, and a thermionic ampli?er
connected to the cathode of the photo-respon
the intensity of the source of radiation as a func
sive element and by which the phase relationship 45 tion of the amount oi‘ light falling on the photo
between the output Voltage of said discharge tube
responsive element which includes in circuit with
and the grid voltage supplied thereto may be
said element, a discharge tube having a control
varied.
grid and an anode, a current supply for said tube,
8. In a device for photographic printing, means an electronically functioning means by which the
for scanning a ?lm including a light source and 50 output of said tube is varied and by which the
a photo-responsive element, a variable source of
effect of changes initiated at the photo-respon
radiation for effecting an exposure and means for
sive element is delayed, including a capacitance
progressing ?lm past the said scanning means
between the current supply and the control grid
' and source of radiation, and means for varying
of the discharge tube, a thermionic ampli?er
the intensity of the source of radiation as a func 65 tube having a control grid and a plate, means
tion of the amount of light falling on the photo
connecting said control grid to the cathode of
responsive element which includes in circuit with
said photo-responsive element, means connect
said element, a discharge tube, a current supply
ing the plate of said tube to the variable source
for said tube, and a thermionic ampli?er con
of radiation and the current supply, said con
nected to the cathode of the photo-responsive 60 nection to the source of radiation having its cir
element and by which the output of said tube is
cuit completed through to the anode of the dis
varied, and other means forming a part of said
charge tube, and a capacitance and resistance
circuit for delaying the e?ect of changes in out
connected in parallel to the circuit between the
put‘ current fromthe photo-responsive element
cathode of the photo-responsive element and the
upon the output of the discharge tube so that 65 control grid of the thermionic tube.
said changes shall become eiiective only after a
12. Mechanism as de?ned in claim 11 further
reference point on the ?lm has moved from the
characterized by an additional and normally in
scanning point to the variable source of radiation.
variable source of radiation.
_
9. In a device for photographic printing, means
13, Mechanism as de?ned in claim 11 further
for scanning a ?lm including a light source and a 70 characterized by an addition Within the circuit
photo-responsive element, a variable source of ra-' - which includes a battery, a connection there
diation for effecting an exposure and means for
from through a resistance to the'anode of said
progressing ?lm past the said scanning means
photo-responsive element, a voltage divider con
and source of radiation, and means for varying
nected to a ground line from that part of the
the intensity of the source of radiation as afunc 75 circuit formed by the capacitance and resistance
1
2,413,218
ii
in parallel and by which the effect of changes
initiated at the photo-responsive element are de
layed.
1 l4. Mechanism as de?ned in claim 11 in which
the thermionic ampli?er tube has a screen grid
and a connection leading therefrom through a
resistance to the output of the plate of said tube.
15. Mechanism as de?ned in claim 11_ in which
12
current supplied to the control grid of the dis
charge tube is limited by a resistor.
16. Mechanism as de?ned in claim 11 in which
a biasing voltage for the control grid of the
thermionic ampli?er tube is supplied through a
variable resistor.
SéMUEL C. CORONITI.
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