close

Вход

Забыли?

вход по аккаунту

?

код для вставки
NOV. 19, 1946.
|__ L. WEISGLASS
2,411,486
LIGHT MEASURING DEVICE FOR PHOTOGRAPHIC ENLARGERS
Filed Dec. 7, 1945
4 Sheets-Sheet 1
' T?
57.1
mimvro
' Lou/1L5 LlUe/isg
By Mai/141m
ATTORNEY
Nov. 19, 1946.
L. 1.. WEISGLASS
2,411,486
LIGHT MEASURING DEVICE FOR PHOTOGRAPHIC ENLARGERS
Filed D89. 7, 1945
4 Sheets-Sheet 2
140
8? Mm. Wm
ATTORNEY
Nov. 19, 1946.
L. 1.. WEISGLASS
2,411,436
LIGHT MEASURING DEVICE FOR PHOTOGRAPHIC ENLARGERS
Filed Dec. '7, 1945
370
w
579
r-??-
81
Mg. m
10
6
יי/
/ // / (/ , ,
.60
?%
-
?
?/
x25
?,0
// \@\
W;
4 Sheets-Sheet 3
/°?
6%
a
*4a (>14
"many, 52
l\
{I
? ie\'{
. ?mu?
M141?
711(0) (2L1? L
f / 4
.'g
3
it ?15.1 /
"'0
/low? L
0"0/
76
?
VII?!!! / "-'
f.
'
Y
.
75
,
82
7 81
70
\
0
77
9
71 \\
G
\\
?Pi f5
J
78
C) 74
1/
76
INVENTOR.
Louis L. l?יb'sglass
BY
ATTORNEY
Nov. 19, 1946.
|_. |_. WEISGLASS
2,411,486
LIGHT MEASURING DEVICE FOR PHOTOGRAPHIC ENLARGERS
Filed Dec. 7, 1945
*
.4 Sheets-Sheet 4
e
Q
0
Fig.7
115
J
M108?
Q
Q
8
Q
? 105
, Fig
113
"I /
/ /
?h?
Ill //
.
?a
/
llllllllllllllllllIlllllllll
11/1
l04._\
"113
V
j; 106
140
I
?
111x11} 111111311
}
Lou/is L. lag/£52255
_
- =
?Y M462 Wm
ATTORNEY
2,411,486
Patented Nov. 19, 1946
UNITED STATES PATENT OFFICE
2,411,486
.
LIGHT MEASURING DEVICE FOR PHOTO
GRAPHIC ENLARGERS
Louis L. Weisglass, New York, N. Y., assignor, by
mesne assignments, to Simmon Brothers, Inc.,
Long Island City, N. Y., a corporation of New
York
Application December 7, 1945, Serial No. 633,475
16 Claims.
(Cl. 8&-?23)
1
The object of this invention is a light measur
ing device which is particularly well adapted to
analyze the enlarged image of a photographic
negative as projected by a photographic enlarger.
tensity indicator associated therewith serves at
the same time to actuate the aforementioned
sensitivity control of the ?rst circuit in such a
way that the sensitivity of the photo-sensitivity
In order to secure more perfect prints from
photographic enlargers it is desirable to know
device is switched from one step to the next one
vary over an exceedingly wide range since they
depend upon many factors such as the dia
this device will be 1:1000. This is a very much
larger range than obtainable by means known
whenever the voltage control device completes
one operating cycle.
the light intensity of the brightest and of the
For example, if the voltage control device
darkest point or image element as it appears on
during
one operating cycle is changing the in
the easel of the enlarger. The solution of this
problem is dif?cult since the intensity thus pro 10 dicated light intensity in the proportion of
1:10 and, if the intensity control has three steps
duced is low, particularly for the dark points,
in the proportion of 1:10:100, the total range of
and because, furthermore, these densities may
phragm setting of the lens, the density of the
photographic negative, the magni?cation ratio
and the condition and supply voltage of the lamp
heretofore.
within the enlarger, each of these factors itself
A preferred form of a light measuring device
built according to this invention is illustrated in
the accompanying drawings, in which
produced.
enlarger;
Fig. 1 shows the general arrangement of the
being capable of wide variations. For this rea
son, no really satisfactory device has as yet been 20 device in connection with a typical photographic
?
Fig. 2 is the circuit diagram;
The general principle of a device to satisfy the
Fig. 3 illustrates a certain rotating switch used
aforesaid conditions is as follows: Two elec
in connection with the supply circuit of a photo
trical circuits are being used, the output voltage
of the ?rst circuit being controlled by a photo 25 electric cell forming part of the device;
Figs. 4, 5 and 6 show sectional views of the
sensitive device and the output voltage of the
container for the photo electric cell with the
second circuit being controlled by some suitable
built-in sensitivity control and in detail Fig. 4
manually operated voltage control device. The
represents a sectional view along the plane of
output voltages of both circuits are made to op
line 4?-4 in Fig. 5; Fig. 5 is a sectional view along
pose each other, and a balance indicator is pro
the plane of line 5--5 in Fig. 4; and Fig. 6 is
vided by means of which the operator can see
identical with Fig. 5 except that it shows the
when, as a consequence of his manipulation of
sensitivity control in a different position.
said voltage control device, the difference be
Figs. 7, 8 and 9 show the main control unit,
tween the two output voltages assumes a pre
certain parts having been omitted in the interest
determined value.
of clarity; Fig. 7 is a plan view of the main con
In order to obtain the necessary wide range,
trol unit with certain parts omitted for sake of
the following means are employed: The ?rst
clarity; Fig. 8 is a sectional view along the plane
circuit which contains the photo-sensitive ele
of line 8?8 in Fig. 9; and Fig. 9 is a sectional
ment is equipped with a sensitivity control which
view along the plane of line 9-9 in Fig. 8; and
provides several steps of sensitivity. The volt
Fig. 10 shows the resistance element of the
age control element of the second circuit is step
voltage control device.
'
less and adapted to adjust the output voltage
Like characters of reference denote similar
of said circuit from a minimum to a maximum
parts throughout the several views and the fol
value during one operating cycle, but can run
through this operating cycle repeatedly while 45
lowing speci?cation.
'
being moved by the operator in the same direc
tion. This voltage control device actuates
Fig. 1 shows the light measuring device as
applied to a typical enlarger. The enlarger con
mechanically an indicator which indicates, on
one continuous scale, light intensity values from
sists in a Well known manner of a baseboard,
an inclined upright column and a projector as
a minimum to a maximum value during one op
erating cycle, but this indicator can run through
assembly comprises a lamp housing with a lamp ?
its operating cycle only once while the voltage
control device runs through its operating cycle
several times at the same time. This voltage con
trol device, or more accurately, the light in
sembly sliding on the column.
The projector
and a condenser, means to support a photo
graphic negative underneath said condenser and
an enlarging lens in adjustable relationship in
front of said negative. The light measuring de
3
2,411,486
vice consists of two principal parts, a small hous
a condenser 54 through a rectifying tube 55, see
ing which contains the photosensitive device with
Fig. 2.
.
its sensitivity control and a larger housing which
This rectifying tube has in the usual manner
contains the other mechanical and electrical ele~
an anode and a hot cathode, and the heating
ments. These two principal parts are connected $71 circuit for said cathode may be supplied either
by a multiple conductor cable, and a second cable
by a separate transformer or, simply, by a few
equipped with a conventional plug permits the
turns of wire wound on the same core as the
device to be connected to any standard socket.
aforementioned primary and secondary coils.
I shall now describe the various component
Since these expedients are well known, the heat
parts which go into a device built according to 10 ing circuit has not been shown in the wiring
this invention.
Photosensitz've device and supply circuit
diagram. Since it is highly desirable to have
the voltage stabilized, i. e., made independent of
line voltage ?uctuations, I am using in a well
The photosensitive device may be of any suit 15 known manner a gas ?lled voltage regulating tube
in series with a suitable resistance 51, the two
able type and description of which numerous
terminals
of the tube 56 being connected to the
modi?cations are well known in the art. It
two brushes 45 and 46 respectively.
may, for example, be a photovoltaic cell of the
In operation, the two brushes 4| and 42 rotate
copper oxide or selenium type, or it may be any
continuously, driven by motor 50, and successively
of the various well known types of vacuum or 20
charge each of the condensers 22?30 to substan
gas ?lled cells which, of course, would have
tially the D. C. voltage impressed? upon stabilizing
to be used together with a suitable ampli?er sys
tube 56. The condensers are su?iciently large to
tem. In practice I prefer to use a tubeof the
suffer only a small voltage loss by the current
socalled electron-multiplier type together with a
drain through the multiplier tube during the time
supply circuit which has been disclosed in my 25
prior application No. 585,350. It will be under
stood that this is merely a preferred type of pho
tosensitive device and that my invention is not
necessarily restricted to its use. The photo sen
sitive electron-multiplier tube with the associ
ated supply circuit is represented by the left half
of the diagram shown in Fig. 2. The electron
multiplier tube l0 comprises an evacuated glass
vessel H and a number of electrodes mounted
therein. The ?rst electrode |2 has a photoemis
sive coating consisting in a well known manner of
a thin layer of potassium or a similar metal.
A number of other electrodes |3?-2| are also
mounted within that vessel. A voltage of ap
interval elapsing between subsequent revolutions
of the brushes 4| and 42. Light impinging upon
electrode l2 releases a small number of electrons?
which are accelerated by the voltage of condenser
22 and impinge upon electrode l3, there knocking
oif secondary electrons. The number of the sec
ondary electrons is larger than the number of
the primary electrons, and the ability of the tube
to ?multiply? electrons is based on this fact. The
secondary electrons emitted by plate l3, in turn,
impinge upon electrode l4 and knock off still more
electrons there, and this process is repeated at
each subsequent stage until a high ampli?cation
is obtained. The last condenser 30 is not directly
proximately 100 volt is impressed between two 40 connected to the last electrode 2| but a resistance
60 is interposed. This resistance is of the general
adjacent electrodes and starting with the photo
order
of approximately 1 megohm. For more de
sensitive electrode |2 each following electrode is
tailed description of this circuit I wish to refer
positive with respect to its predecessor. The last
to my co-pending application No. 585,350.
electrode 2| is then connected to a load device as
will be explained later.
Sensitivity control
The supply circuit necessary to provide the
necessary potential between adjacent electrodes
The sensitivity of the photosensitive circuit
may be designed in many conceivable ways and
merely as a preferred arrangement I am using
a circuit which has been disclosed in application
No. 585,350. This circuit? comprises a number of
condensers 22--30. The points intermediate two
condensers are connected to switch buttons
iii-40, which are circularly disposed on a plate
made from some suitable insulating material such
as Bakelite or hard rubber. In the center of this
switch button circle is a rotating shaft which
carries two brushes 4| and 42, which are respec
may be controlled in many conceivable ways, and
these methods may be either electrical or optical,
i. e., one may either change the electrical char
acteristics of the circuit by changing one or sev
eral of the circuit elements or one may change
the light admittance of the system while keep
ing the electrical characteristics constant.
Either expedient is possible, but it is slightly
advantageous to change the sensitivity by opti
cal means since in this manner the adjustment
of the photosensitive circuit need not be changed.
tively connected to slip rings 43 and 44. These
The sensitivity may be controlled by optical
slip rings, in turn, are in contact with brushes 45 60 means in many ways, and the simplest is to
and 46. This rotating switch is again shown in
change the size of the light admitting aperture.
Fig. 3. As can be seen the two brushes 4| and
This method is quite justi?able under the circum
42 together with the slip rings are mounted on
stances since low intensities will have to be meas
a shaft 41 which must be made from insulating
ured usually with high magni?cation ratios of
material and which also carries a gear 48, which, 65 the enlarger and vice versa.
. in turn, is in mesh with a smaller gear 49, which
Merely as a preferred method I am showing
is driven by the small electric motor 50. The two
a way to control the sensitivity of the device in
brushes 45 and 46 are conductively connected to
three steps by changing the size of the aperture
a suitable source of direct current, brush 45
through which light is admitted to the photo
being connected to the positive and brush 46 to 70 sensitive device. This is done by means of a
the negative pole. This source of D. C. may be
pivoted vane '10 which may rotate on a pivot 1|
of any convenient design and merely for the
and which has three apertures ?I2, 13 and 14.
sake of completeness I am showing a transformer
This vane must be made from opaque material
with an iron core 5|, a primary coil 52 and a
such as aluminum. Two small pieces of iron 15
secondary coil 53. This secondary coil charges 75 and 16 are fastened to this vane andtwo sole
2,411,486
5
cell In is supported by a multiple conductor
I85. The contact spring I84 slides on a metallic '
ring I88. The entire device is mounted by means
of studs I81 on the top panel I88 of the control
box I89. This control box contains in reality
all the electrical elements shown in the wiring
diagram of Fig. 2 with the exception of the mul
tiplying tube I8 and the sensitivity control, as de
socket 88 in a well known manner. This socket
scribed, which are contained in housing 82 as ex
noids 11 and 18 are provided. A spring 19 serves
to keep the vane in its center position as long as
none of the solenoids is energized.
This arrangement is shown schematically in
Fig. 2 and can be seen in detail in its actual pro
portions in Figs. 4, 5 and 6. The photoelectric
plained above. It will be understood that the
is fastened to a bracket 8I which is, in turn, sup
ported within a housing 82. This housing is 10 disposition of these various circuit elements with
in box I89 is of no particular importance and
adapted to be placed on the enlarger easel in a
most of them have, therefore, not been shown in
manner shown in Fig. 1. It has an aperture 83
Figs. 7, 8 and 9. It will be understood that con
through which light may fall upon the tube I8
tact 91 really travels in a circle, as shown in Fig.
or, more particularly, upon its photoemissive
electrode I2. Between aperture 83 and the tube 15 9, and that in the diagram in Fig. 2 its motion is
shown as along a straight line merely as a sche
I8 is the vane 18 with its three apertures. As .
matic simpli?cation.
can be noted in Fig. 5, the spring 19 which tends
The most important part of the voltage con
to keep the vane in its center position is merely a
tiol de'. ice is the resistance element 96 which is
piece of stiff steel wire or the like. Therefore,
ordinarily, i. e., when none of the two solenoids 20 shown again in Fig. 10. It is desirable to have
the scale on which the light intensities can be
is energized, vane 18 will assume the position
read divided in logarithmic progression and it is,
shown in Fig. 5, i. e., aperture 13' will be imme
therefore, necessary to devise a resistance ele
diately underneath and in register with the ap
ment which will have a logarithmic attenuation.
erture 88 in the housing 82 and the light admit
? tance of the photo tube will, therefore, be gov
erned by the diameter of aperture 13. In Fig. 6
25 This is done by winding resistance wire on a ?at
strip of ?exible insulating material such as ?bre
or Bakelite or the like, of trapezoidal shape, as
the same arrangement is shown with the solenoid
shown in Fig. 10. Obviously, the mere trapezoidal
18 energized. Obviously, solenoid 18 attracts the
shape alone will not give really logarithmic at
iron piece 16 thereby rotating vane 18 in such a
way that the small aperture 12 is now underneath 30 tenuation, and I am, therefore, in addition to
using this shape, winding the wire with a variable
and in register with aperture 83 of housing 82.
pitch, i. e., on the left side of Fig. 10, where the
The force of ?magnet 18 must, of course, be
trapezoid is high, the wire is wound very closely,
stronger than the force of spring or steel wire 19.
but the distance between adjacent convolutions is
If the other solenoid 11 is energized the condi
tions will, of course, be reversed, and aperture 14
increasing, until at the right end of Fig. 10, where
the trapezoid is low, the distance between two
will now be in register with the housing aper
adjacent wires is relatively large. After the re
ture 83. Apertures 12 and 13 must be smaller
sistance element has been wound in this manner
than the aperture 83. Aperture 14 may be small
and the wire has been ?xed to the insulating strip
er than aperture 83 in which case the light ad
mittance is controlled by the diameter of aper 40 by suitable means, it is bent into a circular shape
and ?xed to the cylindrical supporting part I88.
ture 14, or aperture 14 may be larger than ap
The tip of contact 91 must, of course, be so wide
erture 83 in which case the light admittance is
that even at the low end of resistance element 98
controlled by the diameter of aperture 83. The
it never loses contact with at least one wire.
circuit which controls the two solenoids 11 and
45
The length of the resistance element 95 and
18 will be described later.
the diameter of the supporting part I88 must be
Voltage control device and supply circuit
matched in such a way that the two ends of 96
meet each other when said resistance element is
The voltage control device and the supply cir
wrapped around the supporting part I88. This is
cuit are shown on the right half of the wiring 50 important since it is necessary that ?the spring
diagram, Fig. 2. A D. C. voltage is supplied in
91, when rotated by turning shaft I82, never loses
the usual manner, 1. e., a transformer secondary
contact with at least one wire of the resistance
90 charges a condenser 9| through rectifying tube
element 98. In this manner, it will be possible
92. The secondary 98 may be part of a separate
to rotate this voltage control device several times,
transformer or, preferably, it may be wound on 55 i. e., make it run through its operating cycle re
the same core as the aforementioned coils 52 and
peatedly, while turning knob I85 always in the
53. The heating circuit for the hot cathode of
same direction. The purpose of this arrangement
the rectifying tube has again been omitted from
will be explained later.
the wiring diagram in the interest of clarity.
The condenser 9| is again connected to a gas 60
Light intensity indicator
?lled voltage regulating tube 93 which is in se?
The light intensity indicator is merely an ele
ries with a suitable resistance 95. Parallel to
ment which is mechanically connected to the volt
the voltage regulating tube 93 is a load circuit
age control device just described and which is
formed by a ?xed resistor 95, a resistor 96 with
a movable contact 91 and another ?xed resistor 65 adapted to run through its operating cycle once
while the voltage control element runs through
98, all three resistors connected in series. The
its operating cycle several times. The simplest
resistor 96 with the sliding contact 91 constitutes
mechanical connection consists of a pair of gears,
the repeatedly mentioned voltage control device
a relatively small gear being connected to the
of this circuit.
The mechanical construction of this voltage 70 shaft of the voltage :control device and a larger
gear being part of the light intensity indicator.
control device can be seen in Figs. 8 and 9. Its
A gear rack may be used instead of the large gear
principal parts are the cylindrical supporting
body I88, the resistance element 96, the rotatable
shaft I82, carrying the two contact springs 91 and
since a gear rack is merely a gear with an in
?nitely large diameter. A scale is carried by the
I84 and being equipped with an insulated knob 75 indicator cooperating with a ?xed mark and indi
7
2,411,486
eating light intensity values from a minimum to
a maximum value.
An arrangement of this type is shown in Figs. 7,
8 and 9. The small gear H0 is attached to the
shaft I02 01' the voltage control device, and this
gear is in mesh with a gear rack III. This gear
rack has a slot I I2 which engages two guide pins
crating cycle, i. e., one revolution, of the voltage
control element equals the change in circuit con
ditions due to the shift from one step of sensi
tivity control to the next one. The most con
venient arrangement is to provide a range of 1:10
for one revolution or one operating cycle of the
voltage control device and to make the area of
?3 fastened to the top I08 of the container I09.
the three apertures of the sensitivity control in
Scale H4 is fastened to the gear rack III, and
the proportion of 1:10:100 thereby providing a
this scale is visible through a slot I I5 in top panel 10 total range of 111000 for the whole device. Suit
I08, see Fig. 7.
A ?xed mark IIS on this top
able dimensions for the apertures in the pivoted
panel cooperates with scale I I4. It will be under
vane are, for example, .250", .079" and .025"
stood that this arrangement could be reversed,
diameter.
i. e., the mark could be attached to the gear rack
Balance indicator
H0, and the scale could be ?xedly attached to 15
the top panel I08. As shown in the drawings, the
It was explained above that I provide two cir
voltage control element makes three revolutions
cuits,
the output voltage of the first being con
while the light intensity indicator runs through
trolled by a photosensitive device and the output
the entire length of its scale once, and the light
voltage of the second by a manually controlled
intensity indicator comprises three decade divi 20 voltage
regulating device. The two output volt
sions of logarithmically progressing scales.
ages are made to oppose each other, and an in
dicator is provided by means of which the opera
tor can see when the difference of the two output
As seen on the left side of wiring diagram, Fig.
voltages assumes a predetermined value. This
2, the two solenoids TI and ?I8 are controlled by 25 balance indicator may be of any convenient de?
two normally open switches I20 and I2I. These
sign and, for example, a sensitive galvanometer
switches are physically arranged as shown in Fig.
will serve quite well. In this case, of course, it
9. The switches shown are of the so-called micro
would be most logical to adjust the two voltages
switch type, but it will be understood that any
until they are equal to each other or until their
other type may be equally applicable for this 30 di?erence becomes zero. Merely as a preferred
purpose. The switches are actuated by a cam
device I am using a gas ?lled thyratron tube I39
abutment I22 which is attached to gear rack I I I.
in series with a load device which indicates when
Switch circuit for sensitivity control
In the position shown in Fig. 9, switch I20 is de
pressed and its circuit closed, whereas switch I2I
is open. Consequently, solenoid ?I8 will attract
the iron piece ?I6 fastened to weight ?I0, and the
small aperture ?I2 will now control the light ad
mittance to the photoelectric cell. If the oper
ator turns knob I05 and thereby gear IIO, the
gear rack III will move to the right, Fig. 8, and,
after one revolution of gear IIO, the cam abut
ment I22 will no longer depress switch I20. In
this position, i. e., during the second revolution
of gear II 0, the cam abutment I22 will assume a
position between the two switches I20 and I2I,
leaving both of them open. As a result, neither
of the solenoids ?II or 18 will be energized, and
vane "I0 will assume the position shown in Figs.
2 and 5, where the center hole ?I3 controls the
light admittance. If the operator continues to
turn knob I05, cam abutment I22 will move fur
ther to the right, Fig. 8, and eventually, i. e., at
the beginning of the third revolution of knob I05,
will depress switch I2I. This will close the cir
cuit for solenoid ?II which will now attract iron
the thyratron becomes current conducting.
A
thyratron is a gas ?lled tube which has a hot
cathode, a grid and an anode. A bias voltage is
impressed between the cathode and the grid and,
depending upon whether this bias voltage makes
the grid su?iciently negative with respect to the
cathode or not, the thyratron becomes current
conducting. The load device which must be in
serted in the plate circuit of the thyratron in
order to indicate whether current flows through
the thyratron may again be of any suitable type,
and again a galvanometer or milliamperemeter
may be used. Again, merely as a preferred de
vice, I am using a small glow lamp I40 ?lled with
neon or some other suitable gas. This lamp
lights up as soon as the thyratron becomes cur
rent conducting, i. e., as soon as the grid voltage
is not su?iciently negative with respect to the
cathode. Usually this cut off bias is of the order
of two volts, i. e., as long as the grid is more than
two volts negative with respect to the cathode,
no current will ?ow from the anode to the cathode
.of the tube I39, but as soon as the grid voltage
becomes more positive than -2 volts the tube will
piece 15 thereby rotating vane ?I0 until the large
aperture 14 is in register with the aperture 83
become current conducting and the glow lamp
of the photocell housing 82, Fig. 4. It will be
will light up.
clear that during the ?rst revolution, 1. e., while
Referring to the vcircuit diagram in Fig. 2, it
the smallest hole ?I2 controls the light admittance 60 can be seen that the output voltage of the ?rst
of the device, the sensitivity of the photocell will
photosensitive circuit is impressed upon resist
be smallest or the indications of the light in
ance 60, and the output of the second circuit is
tensity indicator largest. During the second
impressed upon the series connected resistors 95,
revolution of the voltage control device, the light
96 and 98. Of this last mentioned voltage that
admittance will be controlled by the medium sized 65 portion between the sliding contact 91 and the
hole ?I3, making the sensitivity of the device
negative end of resistance 96 plus the voltage
higher than during the ?rst revolution and, con
across resistance 98 opposes the voltage across
sequently, the indicating light intensity of the
resistance 60. In other words, the resistance 08,
scale lower. During the third revolution the
part of the resistance 96 and the resistance 60
largest hole ?I4 will be in control of the light ad 70 are connected in series and constitute the grid
mittance to the photoelectric cell, which will
circuit of the thyratron. The voltage across re
make the light admittance for the sensitivity of
sistance 60 tends to impress a negative voltage
the device largest and, consequently, the scale
on the grid, whereas the voltage across resistance
values of the indicator smallest. The change in
98 plus part of resistance 96 tends to impress a
circuit conditions which occurs during one op 75 positive voltage across said grid with respect to
a,411,4se
.
10
Under a maximum measurable light condition
we would haveth'e following conditions:
the cathode of the thyratron. As long as the
voltage across 60 is more than two volts larger
than the voltage across 98 plus part of 98 the
thyratron will not conduct current, but as soon
as this di?erence is less than two volts, the grid
-
Volts
Voltage across resistance 60 ___________ __
-50
Voltage across part of resistance 96 in grid
circuit, contact 91 in its lowest position,
will not be su?iciently negative with respect to
Fig. 2 _____________________________ __ +45
the cathode and current will begin to flow which
+3
Voltage across resistance 98 ___________ __
immediately can be seen by the fact that the
neon lamp I40 lights up. In series with neon
Total grid bias _________________ .._
?2
lamp I40 is a resistance I4I ?which is merely a 10
current limiting device. The plate circuit of
Obviously, for intermediate light intensities,
the thyratron with the neon tube could be ener
an intermediate position oFcontact 9'! would be
gized by any suitable source of alternating cur
capable of restoring the same condition, i. e.,
rent, and merely as a convenience I am using
the secondary coil 90 which already constitutes 15 adjust the grid of the thyratron to -2 volts.
The borderline? condition of the neon lamp? I40
a convenient source of alternating current. It
is quite easily 'found since there is a narrow
is well known that alternating current is neces
range in which it is neither consistently on nor
sary for the plate circuit of a thyratron since
consistently off, but ?ickers in more or less regu
otherwise the plate current will continue to ?ow
?
even after the removal of a positive grid voltage. 20 lar intervals of time.
The above numerical example shows, that the
circuit controlled by the voltage control element
Operation
is so adjusted that the voltage across resistance
96 is 10 times as large as the voltage across re
The operation of the device can now be well
understood. Housing 82 with the photocell and 25 sistance 98 plus the minimum grid bias of thyra
tron I39, and that the photo electric circuit is
the sensitivity control is placed on the easel of
the enlarger in the manner shown in Fig. 1, and
the operator selects an image element which he
wants to analyze, shifting the housing 82 into
so adjusted that the maximum voltage across re
comes smaller or, in electrical terms, Fig. 2, con?
as he starts a new revolution, however, one of
_ the contacts I28 or i2I changes its condition,
1. e., if one of the contacts was depressed, it now
ceases to be depressed and vice versa. This im
sistance 60 equals the voltage across resistance 96
plus the voltage across resistance 98 plus the
such a position that the image element is re- ? 30 minimum grid bias, and that the minimum volt
age across 60 equals the voltage across 98 plus
ceived by the aperture 83. Depending upon the
light intensity of this particular element and
said grid bias.
Up to now, I have assumed that the borderline
upon the position in which knob I05 and scale
condition of the neon lamp may be obtained by
M0 happen to be, the neon lamp I40 may or may
not light up. If the neon tube lights up, it indi 35 merely adjusting contact 91. ?I have also ex
plained that this adjustment would change the
cates that current passes the thyratron or, in
indicated light intensity in the proportion of
other words, the grid of the thyratron is not suf
?ciently negative with respect to the thyratron
1:10 and it is, therefore, possible that merely
cathode. This again means that the voltage
adjusting this contact, from its lowest position
in Fig. 2 to its highest position, will not be suf
across resistance 60 is smaller than the minimum
grid bias plus the voltage across resistance 98
?cient to reach the borderline position of the
and part of resistance 96. In order to restore
neon lamp. In this case the operator continues
the balance the operator now turns knob E05 in
to turn knob 505 thereby starting another revo
such a way that the indicated light intensity be
lution of the sliding contact 9?, Fig. 9. As soon
tact 9'! will move upwardly. This will'decrease
that part of the voltage across resistance 98
which is in the grid circuit until eventually, when
the grid voltage becomes su?iciently negative,
mediately changes the size of the light admit
no more current passes thyratron I39 and'glow
ting aperture and, therefore, the sensitivity of
50
lamp M0, which now no longer lights up.
the photoelectric circuit. The slidable resist
This situation can best be explained by a sim
ance will now travel through-another revolution
pli?ed numerical example. We shall assume
that the critical grid bias of the thyratron is
-2 volts. The resistance 96 is adjusted in such
a way that a voltage of 45 volts is built up be
tween its positive and its negative end, and the
voltage across resistance 98 is 3 volts. The light
sensitive circuit is adjusted in such a way that
the minimum measurable light for a given aper
ture size or sensitivity causes a voltage of 5 volts
to be impressed on resistance 60, and that the
maximum measurable light with the same aper
ture causes a voltage of 50 volts across resistance
or operating cycle, again changing the indicated
light intensity of the proportion of 1:10, but,
55
since the aperture has been changed, the device
?now measures light intensities in the next lower
decade. The operator will then continue to turn
knob I05 in such a way that the indicated light
values decreases, but he will work with the next
larger aperture which will make the circuit 10
times as sensitive until eventually a position is
reached in which the neon lamp is in the border
line condition, i. e., just on the verge of lighting
up or not lighting up which is indicated by a
60. In other words, a range of 1:10 for each of
or less regular ?icker.
the three apertures. Under a minimum light 65 more
If
for
any image element which the operator
condition the grid voltage of the thyratron can
wants to analyze the neon light fails to light
be computed as follows:
up, it would indicate a condition opposite to the
Volts
one described in the above example, and the
Voltage across resistance 60 ___________ __
?5
70 operator would then have to turn knob I05 in the
Voltage across part of resistance 96 in grid
opposite direction thereby increasing the indi
circuit, contact 91 in its uppermost po
sition, Fig. 2 _______________________ __
Voltage across resistance 98 ___________ __
0
+3
Total grid bias _________________ __
?2
cated light values of scale H4, until again a
position is reached where the neon lamp is
neither consistently? on nor consistently o?, but
75 ?ickers, The operation of the device is con
9,411,408
11
12
venient, quick and quite accurate within limits
which are perfectly acceptable for photographic
cuit comprising a condenser battery, ?a rotary
.
v
purposes.
It is obvious? that many modi?cations may be
made in the instrumentalities disclosed without
departing from the principles of the invention,
as de?ned in the appendedclaims.
switch, and a source of direct current,? said bat
tery consisting of series connected condensers,
the number of condensers being one less than
the number of electrodes of said photosensitive
tube, said switch comprising a number of sta
tionary, insulated, and circularly disposed switch
What I claim as new, is:
buttons, said number being equal to the num
1. A light measuring device for photographic
ber of said tube electrodes, and a rotatably sup
enlargers comprising a, ?rst circuit, a photo 10 ported assembly comprising two insulated con
sensitive device controlling said ?rst circuit, said
tact brushes and two insulated slip rings, one
circuit including a sensitivity control with sev
contact brush connected to one and the other
eral steps of sensitivity, a second circuit, a manu
ally controlled, substantially stepless, voltage
contact brush to the other of said slip rings, ?
means to rotate said assembly continuously dur
control device controlling said second circuit, a 15 ing the operation of the device, said contact
rbrushes being so disposed as- to contact during
light intensity indicator mechanically associated
with said voltage control device, means? to make
the output voltages of both circuits oppose each
other, and means to indicate when the difference
their rotation two adjacent switch buttons, re
spectively, and two, stationary contacts cooper
ating with said rotating slip rings, the first ter
of said two voltages, as a consequence of said 20 minal of the ?rst condenser being connected to
voltage control device being actuated by the
the ?rst tube electrode and to the ?rst switch
operator, assumes a predetermined value, said
button, the second terminal of the ?rst con
voltage control device adapted to change, in one
operating cycle, the output voltage oi said second
denser being connected to the ?rst terminal of
the second condenser and to the second tube elec
circuit from a minimum to a maximum value, 25 trode and to the second switch button, the sec
ond terminal of the second condenser being con
but adapted to run repeatedly through said oper-?
nected to the ?rst terminal of the third con
ating cycle while being actuated in ?the same
denser and to the third tube electrode and to the
direction, said light intensity indicator adapted
third switch button, and subsequent condenser
to indicate on one continuous scale, in one oper
ating cycle, light intensities from a minimum to 30 terminals, tube electrodes and switch buttons
connected in like manner, the second terminal of
' a maximumvalue, but adapted to run only once
the last condenser being connected to the last
through its operating cycle while being actuated
switch button, a load resistor inserted between
in the same direction, and means to actuate said
sensitivity control of the ?rst circuit automati 35 said last condenser terminal and the last tube
electrode, "said source of direct current supplying
cally by said voltage control device of the second
a voltage substantially as high as that required
circuit, said sensitivity control always advancing
between
two adjacent tube electrodes, and being
one step when said voltage control device com~
connected to the aforementioned two stationary
pletes one operating cycle.
'
2. A light measuring device according to claim 40 contacts cooperating with said two slip rings.
4. In a light measuring device according to
1, said photosensitive device being a tube of the
claim 1, a housing for said photosensitive de
electron multiplier type comprising an evacuated
vice, said housing having an aperture, and said
glass vessel, a plurality of electrodes within the
sensitivity control including means to adjust the
vessel, the ?rst of said electrodes having a photo
size 01 said aperture.
emissive coating and the other electrodes adapt
5. In a light measuring device according to
ed to emit secondary electrons, and a supply
claim 1, a housing for said photosensitive device,
circuit adapted to impress a suitable voltage
said housing having an aperture in its top wall,
between each pair of two successive electrodes,
said sensitivity control including a pivoted opaque
whereby the ?rst photoemissive electrode, upon
vane with a plurality of apertures of diilferent
exposure to light, emits relatively few electrons? 50 sizes, said vane being disposed between said top
which strike the second electrode causing there
wall and said photosensitive device, at the most
the emission of a larger number of secondary
one of the apertures in said vane being larger
electrons which in turn strike the third electrode
than the aperture in said housing, and means
causing there the emission of a still larger num
to rotate said vane thereby bringing selectively
ber of electrons, this being repeated at each sub
one of the apertures of said vane into register
sequent state until a high degree of ampli?cation
with the aperture in said housing.
is obtained thereby.
6. In a light measuring device according to
3. A ?light measuring device according to _ claim 1, a housing for said photosensitive device,
claim 1, said photosensitive device being a tube
said housing having an aperture in its top wall,
of the electron multiplier type comprising an 60 said sensitivity control including a pivoted
evacuated glass vessel, a plurality of electrodes
opaque vane with a plurality of apertures of dif
within the vessel, the ?rst of said electrodes hav
ferent sizes, said vane being disposed between
ing a photoemissive coating and the other elec
said top wall and said photosensitive device, at
trodes adapted to emit secondary electrons, and v the most one of the apertures in said vane being
a supply circuit adapted to impress a suitable
larger than? the aperture in said housing, and
voltage between each pair of two successive elec- ?
trodes, whereby the ?rst photoemissive electrode,
electro-magnetic means to rotate said vane
thereby bringing selectively one of the apertures
upon exposure to light, emits relatively few elec
of said vane into register with the aperture in
trons which strike the second electrode causing
said housing.
there'the emission of a larger number of sec 70
7. In a light measuring device according to
ondary electrons which, in turn, strike the third
claim 1, a housing for said photosensitive device,
- electrode causing there'the emission of a still
said housing having an aperture in its top wall,
larger number of ?electrons, this being repeated
said sensitivity control including a pivoted
at each subsequent stage until a high degree of
opaque vane with a plurality of apertures of dif
ampli?cation is obtained thereby. said supply Q11? 75 ferent sizes. said vane being disposed between
2,411,486
13
14
electro-magnetic means to rotate said vane there
said wire is being wound thereon, but being bent
into a circular shape thereafter and being held
in said shape during operation.
13. A light measuring device according to
by bringing selectively one of the apertures of
said vane into register with the aperture in said
housing, the supply circuit for said electro
tating several times and disposed in the center of
said top wall and said photosensitive device, at
the most one of the apertures in said vane being
larger than the aperture in said housing, and
claim 1, said voltage control device comprising a
ring shaped resistor and a shaft? capable of ro
magnetic means including switching means as
said ring, equipped with a contact in current con
opaque vane with three differently sized aper
a ?xed mark.
9. In a light measuring device according to
claim 1, a housing for said photosensitive device,
said housing having an aperture in its top wall,
said sensitivity control including a pivoted opaque
vane with three di?erently sized apertures, said
vane being ?disposed between said top wall and
said photosensitive device, at least two of the
apertures, in said vane being smaller than the
aperture in said housing, a spring normally keep
ing said vane in a position where the aperture
in the middle is in register with the aperture in
said housing, and two electro-magnets, adapted
to be energized one at a time and to bring, against
the sensitivity control of said ?rst circuit.
15. A light measuring device according to claim
respectively, is in register with the aperture in
said housing, said two electro-magnets being
rent, said rheostat serving as said voltage control
connected to supply circuits including switches,
difference assumes a predetermined value com
contact being in current conducting relation
ship with said resistor, said resistor comprising
a strip of flexible insulating sheet material of
positive end of said resistor connected to the posi
tive pole of said current source, said second cir
ducting relationship with said resistor, and with
sociated with said voltage control device.
8. In a light measuring device according to 10 a gear, said gear being in mesh with a larger gear
capable of performing at the most one full revo
claim 1, a housing for said photosensitive device,
lution and carrying one continuous scale indica
said housing having an aperture in its top wall,
tive of light intensity values and cooperating with
said sensitivity control including a pivoted
14. A light measuring device according to claim
tures, said vane being disposed between said top 15
1, said voltage control device comprising a ring
wall and said photosensitive device, at least two
shaped resistor and a shaft capable of rotating
of the apertures in said vane being smaller than
several times and disposed in the center of said
the aperture in said housing, a spring normally
ring, equipped with a contact in current conduct
keeping said vane in a position where the aper
ture in the middle is in register with the aper 20 ing relationship with said resistor, and with a
gear, said gear being in mesh with a larger gear
ture in said housing, and two electro-magnets
capable of performing at the most one full revo
adapted to be energized one at a time and to
lution and carrying one continuous scale indica
bring, against the force of said spring, the vane
tive of light intensity values and cooperating with
into a position where one of its two other aper
a ?xed mark, said larger gear also being opera
tures is in register with the aperture in said
tively connected to switching means controlling
housing.
1, said ?rst circuit comprising a source of direct
current, a photocell with a photoemissive cath
ode and an anode, and a ?xed resistor, the nega
tive pole of said current source connected to said
photocell cathode, said photocell anode connected
to the negative end of said ?xed resistor, and the
positive end of said resistor connected , to the
positive pole of said current source, said second
circuit comprising asecond source of direct cur
rent and a rheostat with a resistor and a sliding
contact, the positive end of the resistor connected
the force of said spring, the vane into a position 40 to the positive and the negative end of the resistor
to the negative pole of said second source of cur
where one or the other of its two other apertures,
device, said means to indicate when the voltage
prising a source of alternating current, a load
and means associated with said voltage control
device, and a gas ?lled thyratron tube with a hot
device to actuate said switches.
cathode, a grid and an anode, the grid of the
10. A light measuring device according to claim
thyratron connected to the negative end of the
1, said voltage control device comprising a ring
?xed resistor of the ?rst circuit, the positive end
shaped resistor and a shaft with a rotatable con
tact disposed in the center of said ring and ca 50 of said resistor connected to the sliding contact
of said rheostat of the second circuit, and the
pable of performing more than one revolution,
negative end of said rheostat connected to the
said contact being in current conducting rela
cathode of the thyratron, the anode of said thy
tionship with said resistor.
ratron connected to one side of the load device,
11. ,A light measuring device according to claim
the other side of said load device connected to
1, said voltage-control device comprising a ring
one side of said source of alternating current, and
shaped resistor and a shaft with a rotatable con
the other side of said source connected to the
tact disposed in the center of said ring shaped
thyratron cathode, said load device adapted to
resistor and capable of performing more than
indicate when said thyratron becomes current
one revolution, said contact being in current con
ducting relationship with said resistor, said re 60 conductive.
16. A light measuring device according to claim
sistor being so dimensioned that a substantially
1, said ?rst circuit comprising a source of direct
logarithmic attenuation is being obtained.
current, a photocell with a photoemissive cathode
12. A light measuring device according to claim
and an anode, and a ?xed resistor, the negative
1, said voltage control device comprising a ring
pole of said current source connected to said
shaped resistor and a shaft with a rotatable con
photocell cathode, said photocell anode connected
tact disposed in the center of said ring and capa
to the negative end of said ?xed resistor, and the
ble of performing more than one revolution, said
trapezoidal shape and a large number of convo
lutions of resistance wire wound thereon, these
convolutions being close together at the high end
of said trapezoidal strip and relatively widely
spaced at the low end, said strip being flat while
cuit comprising a second source of direct cur
rent and a rheostat with a resistor and a sliding
contact, the positive end of the resistor connected
to the positive and the negative end of the resistor
to the negative pole of said second source of cur
rent, said rheostat serving as said voltage control
15
2,411,480
16
device, said means to indicate when the voltage
cathode of the thyratron, the anode of said thy
diii'erence assumes a predetermined value com
prising a source of alternating current, a gas
ratron connected to one side 01' said gas ?lled
glow lamp, the other side oi! said glow lamp con
nected to one side of said source of alternating
current, and the other side of said source con
filled glow lamp, and a gas ?lled thyratron tube
with a hot cathode, a grid and an anode, the grid
of the thyratron connected to the negative end
of the ?xed resistor of the ?rst circuit, the posi
tive end of said resistor connected to the sliding
contact of said rheostat of the second circuit, and
the negative end of said rheostat connected to the "10
nected to the thyratron cathode, said glow lamp
adapted to indicate when said thyratron becomes
current conductive.
LOUIS L. WEISGLASS.
Документ
Категория
Без категории
Просмотров
0
Размер файла
1 408 Кб
Теги
1/--страниц
Пожаловаться на содержимое документа