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Патент USA US2133138

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Oct. 11, 1938.
F_ HAMACHER
2,133,138
STROBOSCOPE
Filed May 4, 1936
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OSCILLATOR
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Inventor‘ -.
Fritz I-Iam acher, :‘
Patented Oct. 11, 1938
2,133,138
‘UNITED STATES PATENT OFFICE
2,133,138
STBOBOSCOPE
Fritz Hamacher, Spandau-Ruhleben, Germany,
assignor to General Electric Company, a corpo
ration of New York
Application May 4, 1936, Serial No. 77,880
In Germany May 24, 1935
13 Claims. (Cl. 88-14)
My invention relates to stroboscopes and concerns particularly such apparatus for viewing
very rapidly moving objects.
It is an object of my invention to provide means.
5 ‘for producing light ?ashes having a very high
order of frequency.
‘ Other and further objects and advantages will
become apparent as the description proceeds.
In accordance with my invention in itspre10 ferred form, I employ a cathode ray tube having
a ?uorescent screen and means for causing cathode rays to impinge on the ?uorescent screen in-
arrangement between them and the relative volt
age applied is such as to diverge the cathode rays
emanating from the cathode M.
‘ The tube is energized by a source of current l8
connected between the cathode l4 and the anode 5
It. Suitable means are provided for interrupt
ing the cathode rays intermittently in order to
cause intermittent energization of the ?uorescent
screen i3, thereby producing light ‘?ashes for
stroboscopic purposes. If desired, the interrup- 10
tion of the cathode rays may be produced by mak
ing the energizing current source la a source of
termittently with a high frequency. The tube is
so arranged that the ?uorescent screen projects
15 the light upon the rapidly moving object to be
alternating current.
I
In the arrangement of Fig. 1, I provide a volt
age divider I9 connected between the terminals 15
Viewed 0!‘ provides a luminous background for Silhouetting the moving object.
The invention Will be understood more readily
’ from the following detailed description When oon20 sidered in connection with the accompanying
drawing and those features of the invention which
are believed to be novel and patentable will be
pointed out in the claims appended hereto. In
the drawing, Fig. 1 is a schematic diagram repre25 senting one embodiment of my invention and
Fig. 2 is a schematic diagram representing a mOdification of the apparatus of Fig. 1. Like reference characters are utilized in the drawing to
of the current source l8 and connect the control
electrode IT to an intermediate point on the volt
age divider I9. The relative voltages of the elec
trodes l6 and I‘! are such as to spread the cathode
rays into a cone or a solid angle covering the 20
screen l3. Inasmuch as the ratio of the instan~
taneous voltages applied to the control electrode
and the anode l6 determines the focusing or de
gree of divergence of the cathode rays, it will be
apparent that the focusing of the rays and the 25
illuminated area of the ?uorescent screen I3 is
30
unchanged by the variations in instantaneous
value of the voltage of the source- i8.
It will be
designate like parts throughout.
understood that, when the instantaneous value
In the arrangement of Fig. 1. an electronic tube
II is employed having an evacuated envelope l2
to 15 microns may be desirable- The tube ll may
be similar to the known cathode ray tubes or to
Braun tubes but preferably the cathode I4 is of
relatively increased size and the other electrodes
are suitably arranged to produce alight source of
l'elatively large area at the fluorescent Screen '3
by having the cathode rays emerge in a divergent
of the voltage falls below zero, or, in fact, below
a given positive value, the emission of cathode
rays will be cut o? and the screen l3 will become
dark. The frequency of the light ?ashes produced
by the ?uorescent screen will, therefore, coincide
with the frequency of the alternating-current
source is,
The light produced by the ?uorescent screen 13
is caused to illuminate a, moving object which is
to be observed. Such a moving object may, for
example, be a rotating gear 20. If desired, the
brilliancy of the ?uorescent screen I 3 may be
diminished by ‘weakening the cathode rays and
the rotating gear 20 may be observed by arrang
ing the apparatus to bring the gear 20 between
the ?uorescent screen l3 and the observer’s eye
2|, thus silhouetting the gear 20 against the flu
orescent screen 13. When used for silhouetting,
the surface of the screen I3 is preferably of such
fan or cone-Shaped bundle Spread over substan-
area as to subtend as great an optical angle as
containing a fluorescent screen 13 at one end and
a cathode H at the other end fol‘ producing radiant energy. preferably cathode rays or electrons
35 impinging upon the Screen l3- The Cathode M
is preferably of the incandescent type having a
source of current l5 for heating the Cathode to
incandescence. If an incandescent cathode is
employedthe envelope may be evacuated to ap40 proximately 301 micron on the other hand
with a cold cathode air pressures as high as 5
r0 tially the entire surface of the screen l3. In addi, tion to the cathode I4, an anode I6 is provided
30
35
40
45
the moving object to be observed, such as the gear 50
20 or one of the teeth thereof.
and preferably also a control electrode II. In
It will be understood that, in viewing moving
‘ the arrangement of Fig. 1, the anode l6 and the objects stroboscopically, the object may be made
control electrode I‘! are in the form of perforated to appear to stand still or to move very slowly by
55 disks, diaphragms or cylinders and the spacial ._ illuminating it with light ?ashes having the same 55
2,138,138
- frequency or a frequency nearly the same as that
of the speed of revolution, speed of vibration, or
in the case of gears and similar objects with re
peated similar parts such as spokes or teeth the
angular speed divided by the number of spokes,
teeth, or other repeated parts. In order to adapt
the apparatus for observation of parts moving at
different speeds, it is desirable to employ means
for varying the frequency of the light ?ashes.
10 For this purpose a suitable variable frequency al
ternating current source may be employed at I 8,
e. g. a variable frequency vacuum tube oscillator
such as illustrated in Fig. 2.
Although I have found that satisfactory results
15 may be obtained by utilizing an alternating cur
rent energizing source to produce the interrup
tions in the illumination of the ?uorescent screen,
it will be understood that my invention is not
limited to this precise arrangement. My inven
20 tion obviously includes other means for inter
rupting the energization of the ?uorescent screen,
such as means for causing cathode rays to sweep
across the ?uorescent screen or around a target
protecting the screen, or means for interrupting
25 the voltage applied to a control electrode.
For example, in the arrangement of Fig. 2, I
have shown a cathode ray tube ll having a cath
ode I4 and an anode “3 corresponding to the
cathode and anode of the apparatus of Fig. 1 but
30 energized by a direct-current source 22. The
tube of Fig. 2 has two auxiliary electrodes which
might be termed “control electrodes", one of
which, the electrode 23, serves as a focusing elec
trode for controlling the focusing of the cathode
35 rays and is connected to an intermediate tap
of the direct-current source 22, and the other
of which, in the form of a grid 24, is arranged to
cut off the cathode rays in the usual manner by
interposing a negative electrostatic ?eld. The
40 control electrode 24 may be utilized to produce
intermittent illumination of the ?uorescent
screen [3 by connecting a variable frequency al
ternating-current source 25 between the cathode
l4 and the control electrode 24.
45
Cathode rays
will be caused to impinge upon the ?uorescent
screen l3 with a frequency corresponding to the
frequency of the variable frequency source 25
since, whenever the voltage of this source be
comes negative, the cathode rays will be cut oil‘.
50 Inasmuch as stroboscopes employing cathode ray
energized ?uorescent screens are of particular
value for observing extremely high frequency
phenomena for the reason that cathode rays lend
themselves to control at considerably higher fre
55 quencies than the frequencies of light ?ashes
which have hitherto been available in stroboscop
ic apparatus, I prefer to provide a source of high
frequency, such as a vacuum tube oscillator, for
energizing the control electrode 24.
Some por
60 tion of the vacuum tube oscillator circuits, such
as an inductance or a condenser 26 may be made
variable, and may be provided with a control
handle extending from the casing of the oscilla
tor 25 or with other suitable means to permit
65 varying the frequency of the light ?ashes illumi
nating the moving object 20.
If desired, instead of actually interrupting cath
ode rays for the purpose of producing light ?ashes
from the ?uorescent screen I3, I may cause the
cathode rays to sweep across the ?uorescent
screen I3. For example, by adding electromag
netic beam control means, such as a coil, or elec
trostatic beam control means, such as a pair of
de?ecting plates 21, energized by a suitable source
75 of alternating current 28, I may cause the beam
to sweep back and forth across the ?uorescent
screen l3. Preferably, in this form, of the inven
tion, the cathode l4 and the electrodes 23 and 24
are so shaped as to produce a flat beam in the
form of a sheet of cathode rays in a plane per
pendicular to the plane of the paper as seen in
Fig. 2. The beam is thus fan shaped with the
cathode rays spread across the solid angle which
is subtended by the screen 13. By employing a
fast ?uorescent screen, such as one comprising 10
calcium tungstate, the illumination of the screen
will persist for a very short period of time after
the cathode ray beam has passed across the
screen and will be darkened in the interval be
tween successive sweeps of the beam across the 15
?uorescent screen l3.
If desired the sweep plates 2'! may be so ar
ranged in relation to the other electrodes that
the cathode rays are swept beyond the ?uorescent
screen to insure intermittent cessation of illumi 20
nation, or one or more targets 29 may be provided
in one or more portions of the tube to inter
cept the cathode rays during a portion of each
successive sweep.
I have herein shown and particularly described 25
certain embodiments of my invention and cer
tain methods of operation embraced therein for
the purpose of explaining its principle and show
ing its application but it will be obvious to those
skilled in the art that many modi?cations and 30
variations are possible and I aim, therefore, to
cover all such modi?cations and variations as fall
within the scope of my invention which is de?ned
in the appended claims.
What I claim as new and desire to secure by
Letters Patent of the United Statesis:
1. In a silhouetting stroboscope, the combina
tion of a cathode ray tube having a ?uorescent
screen, and means within the tube for producing
cathode rays, spreading them across a solid angle
covering the screen and producing impingement 40
of said rays upon said screen intermittently at
high frequency to form high frequency light
?ashes each extending over the area of said
screen.
2. In a stroboscope for viewing rapidly moving 45
objects, the combination of a cathode ray tube
with a ?uorescent screen for providing light,
means for generating a divergent cone of cathode
rays impinging on said screen and substantially
covering it to cause it to produce light, and means 50
for interrupting at a high frequency the impinge
ment of cathode rays on said screen to cause the
light thereof to occur in high-frequency ?ashes.
3. In a stroboscope for viewing rapidly moving
objects, the combination of an electronic tube
with a ?uorescent screen for providing light,
means within the tube for directing radiant ener
gy against said ?uorescent screen and spreading
said radiant energy across substantially the en
tire surface ofv the screen to cause it to produce
light over its area, and means for interrupting at
a high frequency the impingement of radiant en
ergy on said screen to cause the light thereof to
' occur in high-frequency ?ashes.
4. In a stroboscope for viewing rapidly moving
objects, the combination of an electronic tube
with a device for converting radiant energy into
light, means Within the tube for directing a di
vergent cone of radiant energy against said de 70
vice with the base of said cone substantially
covering said device to cause it to produce light,
and means for interrupting at a high frequency
the impingement of radiant energy on said device
75
3.
2,183,188
to cause the light thereof to occur in high-fre
quency ?ashes.
5. In a stroboscope for viewing rapidly moving
objects, the combination of an evacuated dis
charge tube containing a light-generating sur
face, and means also contained within the tube
for simultaneously energizing substantially the
entire area of said light generator with interrup
tions at high frequency.
10
6. In a stroboscope for viewing rapidly moving
objects, the combination of a cathode ray tube
with a ?uorescent screen for producing light,
means for generating a fan~shaped bundle of
cathode rays impinging on said screen and
extending across its width to cause it to produce
a line of light, and means for ‘sweeping said cath
ode ray bundle transversely to itself across said
screen beyond an edge thereof at high frequency
to illuminate the entire screen and leave it dark
20 alternately thus causing the. light thereof to occur
in high-frequency ?ashes.
7. In a stroboscope for viewing rapidly moving
objects, the combination of a cathode ray tube
with a ?uorescent screen for providing light,
means for generating a divergent cone of cathode
with a ?uorescent screen for’ providing light, an
anode. a cathode and a beam cut-off control elec-'
trode, a source of high-tension current connected
between said anode and cathode, and a source of
high-frequency alternating current connected be
tween said cathode and control electrode.
10. In a stroboscope for viewing rapidly moving
objects, the combination of a cathode ray tube
with a ?uorescent screen for providing light, an
anode, a cathode and a control electrode, a volt 10
age divider, and a source of alternating current
of high frequency connected to said anode and
cathode and to said voltage divider, said control
electrode being connected to an intermediate
part of said voltage divider.
11. In a stroboscope for viewing rapidly moving
objects, the combination of a_ cathode ray tube
with a ?uorescent screen for providing light, an
anode and a cathode, a source of variable fre
quency alternating current directly connected be 20
tween said electrodes, and means for varying the
frequencythereof.
‘
12. In a stroboscope for viewing rapidly moving
objects, the combination of a cathode ray tube
having a ?uorescent screen, means within the 25
rays impinging on said screen and substantially
covering it to cause it toproduce light. and means
for interrupting said cathode rays at a high fre
high frequency impingement of said beam on said
quency.
screen.
_
,
8. Ina stroboscope for viewing rapidly moving
objects, the combination of a cathode ray tube
with a ?uorescent screen for providing light,
an anode and a cathode, and a source of high
frequency alternating current directly connected
between’ said electrodes.
9. In a stroboscope for viewing rapidly moving
objects, the combination of a cathode ray tube
15
tube for producing'a cathode ray beam extending
across said screen and means for interrupting at
13. In a stroboscope arrangement for viewing 30
rapidly moving objects, an evacuated discharge
tube having a light generating surface, means
contained within the tube for energizing inter
mittently at high frequency substantially the en
tire surface of said light generator simultane-' 35
ously.
mrrz HAMACHER.
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