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Патент USA US2406982

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Sept. 3, 1946.
v. K. ZWORYKIN ET AL
23406382
ELECTRONIC VIBRATION DETECTING-APPARATUS
Filed June 20‘, 1942
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Patented Sept. 3, 1946
2,406,982
UNITED STATES PATENT‘ OFFICE
2,406,982
ELECTRONIC VIBRATION DETECTING
APPARATUS
Vladimir K. Zworykin, Philadelphia, Pa, and
James Hillier, Cranbury, N. JL, assignors to‘
Radio Corporation of America, a corporationof
Delaware
ApplicationJuneZO, 1942; Seri'alNo. 447,864
9 Claims. (Cl. 1.77—-351)
1
This invention relates generally to vibration
2
vide a new and improved means for detecting
detecting apparatus and particularly to vibra
vibrations of extremely small amplitude.
tion detection apparatus which utilizes. an elec—
tron probe of extremely small cross sectional area
which is-interrupted by a sharply de?ned mask
ing. element responsive to the source of‘ vibra
tions under observation.
otherobj-ect of the invention is to provide‘ a new
and improved means for detecting vibrations of
An
extremely small‘ amplitude in which the detection
apparatus is substantially independent of thefre
quency characteristics of the vibrations. Another
object is to provide a new’ and improved means
for detecting vibrations in a body, in which means
dimensions of the elements of the. apparatus. 10 an electron probe of small cross-sectional area
Suchv apparatus limitations have in most cases
is interrupted by a movable’ element having a
prevented the measurementof vibrations of am
sharply de?ned edge responsive to the source‘ of
plitude less than of the order of a micron- Since
vibrations, and in which means‘ sec0ndary~elec
by utilizing. the teachings of the electron micro
tron responsive means is located in proximity to
scope art, it is now possible to provide an electron '
the point of’ impingement of the electron beam
beam or probe having a. cross sectional area of
on the movable element. Still another object
the order of I00 angstrom units, extremely sensi
of‘ the invention is to provide a new and improved
tive vibration detection apparatus may be con
vibration detecting means, as described‘ hereto
structed in. which such a concentrated. electron‘
fore, which includes means for generating‘, in
beam is interrupted by a sensitive element con 20 dicating, and. recording‘ electric currents derived
nected' to the. source of vibrations.
from. the secondary‘ electrons emitted by the mov
The instant invention includes a conventional
able element‘ in response to the vibrations under
electron gun. and electron focusing lenses of
observation.
either the electrostatic or electromagnetic types,
The invention will be" described by reference to
Heretofore, the sensitivity of vibration detec
tion apparatus has been. limited by the phyiscal
enclosed within arelatively heavy evacuated con
tainer suitably supported to effectively insulate
the unit. from the source of vibrations. The par
the accompanying drawing in. which Figure I is
a schematic diagram of one embodiment thereof;
and Figure 2 is a view partly in section of a
modi?cation of" a portion of the device shown in
Figure 1. Similar reference numerals are ap
ticular arrangement of the component elements
of the electron. beam generating and. focusing
elements may be as hereinafter described, or 30 plied to similar elements throughout the draw
may- be of thev generalv type described by Manfred
mg.
Von Ardenne in U- S. Patent 2,257,174, granted
Referring. to Fig. l- of the drawing, a heavy
October 7., 1.941, for an Electronic-optical. device.
evacuated casing l is supported on a suitable
Asensitively balanced; and pivoted movable: ele
frame 2 by means of‘ a plurality of expansion
ment is supported by the heavy casing, and is
springs 3,, to provide a substantially vibration
arranged for contact with the source of vibra
proof'mo'un-ting for the casing I. Within the cas
tions. Through a suitable. S-ylphon. vacuum-tight
ing, an electron sourced. is connected't'o a source
of high. negative potential; derived from any suit
enclosed.
connection,
within
onetheend-vacuum
of the chamber:
movable in
element
the path
able power source 26. An anode 5, which in
of the ?nely concentrated electron probe, in such ~10 cludes a suitable aperture, and which is-at- ground
a. manner that the electron beam falls upon a
potential with respect. to the electron source 4-,
sharply de?ned edge of the movable- element. In
accelerates and. concentrates the electrons emit
a preferred arrangement the sharply de?ned-edge
tedlfromthe electron source into a. suitable beam.
of the movable element is highly secondary
A series of electron. lenses. 6,‘! and. 8, of the gen
electron emissive, and suitable secondary-electron
eral type utilized in electron microscopes, focuses
responsive apparatus is associated therewith. for
the electron beam passing through the aperture
indicating the interruption of the electron beam
in the anode 5 into‘ an. electron beam or probe
in response to the vibrations under observation.
having extremely small; cross-sectional area- It
The particular arrangement ofthe component
shouldv be. understood thatv the lenses 6,, 1- and 8
elements of the secondary-electron. responsive ap bi) may‘ be-of either the electro-magnetic or electro
paratus may be of. any type. well known- in. the art,
static types, and‘ may be‘ of the type employed in
or as described in. the. copending application. of
the electron: microscope art.
James Hillier, Serial. No. 445,181’, ?ledi May 30-,
A. bracket. 9 is connected to the evacuated cas
1942,.describedhereinafter.
ing I. through- a-hinge' member In. A‘ movable
" Among the objects of the invention are to pro
lever element I l is pivoted at the extremity of the
2,406,982
3
bracket 9.
The lever element II includes a con
4
electron probe. For most e?icient operating a
carefully prepared contacting surface 25 should
tact element for contact with the source of vibra
be provided for the vibrating body I4 at the point
tions. A Sylphon vacuum-tight connection I2 is
of contact with the movable lever element I I. It
sealed to the remaining arm of the lever member
should further be understood that additional me
I I to permit movement of the lever member with
chanical modi?cations may be provided in the
in the evacuated casing I. The extremity I3 of
structure of the lever or contact element, and for
the lever member II within the casing I, ter
locating and adjusting accurately the position of
minates in a knife edge preferably having sub
the casing I and the movable element II with
stantial secondary-electron emission character
istics. This knife edge is normally disposed in 10 respect to the vibrating body I4 without departing
from the spirit and scope of the invention.
the path of the ?nely concentrated electron probe
in such a manner that vibrations transmitted, for
example, from a body I4 through the lever mem
ber I I will cause interruption of the electron beam
or probe by the knife edge I3 at the frequency
of the vibrations. The lever member should
preferably be made as small and light as possible,
in order to provide satisfactory operation for
vibrations of below the desired maximum fre
quency. For the purpose of adjusting the initial
position of the knife edge I3 in the path of the
electron probe, a screw type adjustment I5 may
be provided for the hinge bracket 9 and another
screw type adjustment I6 may be provided for
adjusting the position of the Sylphon I2 sealed
to the lever element I I.
In the path of the ?nely focused electron beam
is a ?uorescent screen I'I, having an aperture It
to permit the electron probe to penetrate the
screen to the knife edge I3 of the movable ele
ment II. Secondary electrons emitted from the
knife edge I3 are attracted to the ?uorescent
screen II, which is at a potential more positive
Fig. 2 is similar to Fig. 1 with the exceptions
that a solid ?uorescent screen 28 is used instead
of the apertured screen ll of Fig. 1, the accelerat
ing screen 21 is omitted and the knife edge I3 of
the movable elever element II interrupts the elec
tron probe at a point between the third lens 8 and
the solid ?uorescent screen 28. Accordingly the
solid ?uorescent screen is responsive to the pri
mary electrons of the electron probe which are
not interrupted by the movable element knife
edge I3. Otherwise the operation and construc
tion is similar to that of the device of Fig. 1.
We claim as our invention:
1. An electronic device for detecting vibration
in a body, said device including a relatively heavy
evacuated envelope enclosing means for generat
ing an electron beam, and means for deriving
from said beam an electron probe of small cross
sectional area, a movable element having a sharp
ly de?ned edge enclosed within said envelope re~
sponsive to said vibration of said body, means for
focusing 'said electron probe at said edge of said
element, and means including electron responsive
than the electron source 4 and the grounded cas
ing I, due to a positive potential applied to a 35 means enclosed within said envelope responsive to
said movement of said edge of said element for
screen 2‘! surrounding the ?uorescent screen. Im
deriving an electric current of amplitude propor
pingement of electrons on the ?uorescent screen
tional to a function of said movement.
I‘! produces ?uorescence thereof which is imaged
2. An electronic device for detecting vibration
by an optical lens I9 sealed in a suitable window
in a body, said device including a heavy evacu
in the evacuated casing I, upon a light sensitive
able container, vibration insulating means for
device 20 supported in proximity to ‘the lens. The
supporting said container in proximity to said
light sensitive device 20 may be either a photo
body, means for generating an electron beam and
electric cell or an electron multiplier of any suit
means for deriving from said beam an electron
able type well known in the art. The output of
the light sensitive device 20 is connected to the 4-5 probe of small cross-sectional area, a movable
element having a sharply-de?ned secondary elec
input of an amplifier 2I designed to amplify effi
tron emissive edge enclosed within said container
ciently the frequencies to be observed. The out
responsive to said vibration of said body, means
put of the ampli?er 2| is connected, through a
for focusing said electron probe at said edge of
switch 22, to either a cathode ray oscilloscope 23
or a recorder 24. It should be understood that 50 said element, means for collecting secondary elec
trons from said edge of said element and a, ?uo
the characteristics of the indicator 23 and the re
rescent screen enclosed within said container,
corder 24 may be suited to the particular type of
means for applying said secondary electrons to
indication or recording desired, and that the par
said screen to produce ?uorescence thereof, and
ticular apparatus may be of any type well known
light responsive means for deriving an electric
in the art.
current proportional to a function of said ?uo
The electron focusing lenses are adjusted to
rescence.
provide an electron beam of the smallest possible
3. A device of the type described in claim 2 in
cross-sectional area at the point of impingement
cluding current indicating means, and means for
of the electron beam with the knife edge I3 of the
movable element I I. If the casing I is supported 60 applying said derived current to said indicating
means.
in proximity to the vibrating body I 4, the bracket
9 is adjusted by the adjusting device I5, and the
movable element II is adjusted by the adjusting
device I6, so that the knife edge I3 just inter
4. A device of the type described in claim 2 in
cluding current recording means, and means for
applying said derived current to said recording
sects the electron beam when no vibrations are
means.
' 5. An electronic device for detecting vibration
transmitted to the movable lever element I I.
in a body, said device including a heavy evacuable
Since the sensitive movable lever element pro
container, vibration insulating means for sup
vides a leverage of several times, it is apparent
porting said container in proximity to said body,
that the most minute vibrations applied to the
lever element II will completely interrupt the 70 means for generating an electron beam and
means enclosed within said container for deriv
electron beam at the frequency of the vibrations
ing from said beam an electron probe of small
from the source I4. It should be understood,
cross-sectional area, a movable element having a
however, that a lever type vibration transmitting
sharply-de?ned secondary electron emissive edge
element is not essential, and that any other sensi
enclosed within said container responsive to said
tive means may be provided for interrupting the
5
2,406,982
6
vibration of said body, means for focusing. said
electron probe at said edge of said element, means
for collecting secondary electrons from said edge
of magnitude proportional to a function of said
movement.
8. An electronic device for detecting vibration
of said element, a ?uorescent screen enclosed
in a body, said device including an evacuated en
velope enclosing means for generating an elec
within said container, means for applying said
secondary electrons to said screen to produce ?u
orescence thereof, and light responsive means in—
cluding a photo-electric device and an ampli?er
connected to said photoelectric device for deriv
tron beam, a movable element responsive to vi
bration of said body, said element having a
sharply-de?ned movable edge enclosed within
said envelope, means for focusing said beam to
ing an electric current proportional to a function 10 provide an electron probe of small cross-sectional
of said fluorescence.
6. An electronic device for detecting vibration
in a body, said device including an evacuated
envelope enclosing means for generating an elec
tron beam, a movable element responsive to vi
bration of said body, said element having a
area impinging upon said edge of said movable
element, means for collecting secondary elec
trons from said edge of said element in response
to said impingement of said electron probe there
on, and means including secondary electron re
sponsive means enclosed within said envelope re
sharply-de?ned movable edge enclosed Within
sponsive to said movement of said edge of said
said envelope, means for focusing said beam to
element for deriving an electric current of mag
provide an electron probe of small cross-sectional
nitude proportional to a function of said move
area impinging upon said edge of said movable
ment.
,
element, and means including electron responsive
9. An electronic device for detecting vibration
means enclosed within said envelope responsive
in a body, said device including an evacuated en
to said movement of said edge of said element for
velope enclosing means for generating an elec
deriving an electric current of magnitude pro
tron beam, a movable element responsive to vi
portional to a function of said movement.
25 bration of said body, said element having a
'7. An electronic device for detecting vibration
sharply-de?ned movable edge enclosed Within
in a body, said device including an evacuated en
said envelope, means for focusing said beam to
velope enclosing means for generating an elec
provide an electron probe of small cross-sectional
tron beam, a movable element responsive to vi
area impinging upon said edge of said movable
bration of said body, said element having a 30 element and providing secondary electron emis
sharply~de?ned movable edge enclosed Within
sion therefrom, a ?uorescent screen enclosed
said envelope, means for focusing said beam to
within said envelope, and means for applying
provide an electron probe of small cross—sectional
said secondary electrons to said ?uorescent screen
area impinging upon said edge of said movable
to provide ?uorescence thereof proportional to
element, and means including electron respon 35 a function of said movement of said edge of said
sive means enclosed within said envelope respon
element.
sive to electrons of said probe passing said edge
of said element for deriving an electric current
VLADIMIR K. ZWORYKIN.
JAMES I-IILLIER.
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