A multichannel laser remote control system is described. The system is used in areas where radio frequency, acoustic, and hardware control systems are unsatisfactory or prohibited and where line of sight is unobstructed. A modulated continuous wave helium-neon laser is used as the transmitter and a 360 degree light collector serves as the antenna at the receiver

Burcher, E. E.

Rowland, C. W.

Sinclair, A. R.

English

NASA Technical Reports Server

NATIONAL AERONAUTICS AND SPACE ADMIN
WASHINGTON, D.C. 20546
(NASA-Case-LAR-10311-1) LASEfi
COMMUNICATION SYSTEM FOR CONTROLLING
REPLY TO „ SEVERAL FUNCTIONS AT A LOCATION REMOTE
ATTNOF: GP TO THE LASEfi Patent (NASA) 6 p Unclas
CSCL 20E 00/16 52671
TOs KSI/Scientific & Technical Information Division
Attention: Miss Winnie M. Morgan
FROMs GP/Office of Assistant General Counsel for
Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in STAR
In accordance with the procedures agreed upon by Code GP
and Code KSI, the attached NASA-owned U.S. Patent is being
forwarded for abstracting and announcement in NASA STAR.
The following information is provided:
U.S. Patent No. ; "^ X
Government or /
Corporate Employee : l/<S< GovV/eA rt'enr
Supplementary Corporate
Source (if applicable) ;
NASA patent Case No.
NOTE - If this patent covers an invention made by a corporate
employee of a NASA Contractor, the following is applicable:
Ves
 / .../ No f ~y£/
Pursuant to Section 305 (a) of the National Aeronautics and
Space Act, the name of the Administrator of NASA appears on
the first page of the patent; however, the name of the actual
inventor (author) appears at the heading of o^ S^^ w^ 1 of
the Specification, following the words H. ^ ^^ with ^Sf^ ct to
an invention of . „ , H
Elizabeth A. Carter
Enclosure
Copy of patent cited above
NASA
https://ntrs.nasa.gov/search.jsp?R=19730007809 2020-03-17T08:04:24+00:00Z
PATENTED JAM 91973
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INVENTORS
ERNEST E. BURGHER
CARROLL W. ROWLAND
BY ARCHIBALD R..SINCLAIR
< } £ _ _ / ? f /fTjS
ATTORNEYS
PATENTEDJAN 91973
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INVENTORS
ERNEST E. BURGHER
CARROLL W. ROWLAND
BY ARQHIBALJ? 8.S1NCLAIR
United States Patent 091
Burcher et al.
[in 3,710,122
[45] Jan. 9,1973
[54] LASER COMMUNICATION SYSTEM
FOR CONTROLLING SEVERAL
FUNCTIONS AT A LOCATION
REMOTE TO THE LASER
[75] Inventors: Ernest E. Burcher, Newport News,
Va. 23602; Carroll W. Rowland,
Archiblad R. Sinclair, Hampton,
Va. 23366
[73] Assignee: The United States of America as
represented by the Administrator of
the National Aeronautics and Space
Administration
[22] Filed: April 24, 1970
[ 2 1 ] Appl. No.: 31,702
[52] U.S.CI 250/199,340/171,350/293
[51] Int. Cl H04b 9/00, G02b 5/10
[58] Field of Search 250/199, 216, 227; 340/189,
340/171; 350/198, 199,293-295,296;
178/DIG. 15
[56] References Cited
UNITED STATES PATENTS
3,121,169 2/1964 Benton 250/199
3,226,557 12/1969 Goodman 350/198
3,551,676 12/1970 Runnels 350/198
3,551,682 12/1970 Kerhoas 250/227
3,562,540 2/1971 Hirsch 250/227
3,189,744 6/1965 Ogland 250/199
3,341,707 9/1967 Wingfield et al 250/199
3,471,833 10/1969 Whitaker 340/171
3,432,766 3/1969 Morantz 350/198 UX
3,379,887 4/1968 Stephany 250/199
3,503,061 3/1970 Bray ei ai 250/199
3,383,511 5/1968 Falser 350/199 UX
Primary Examiner—Robert L. Griffin
Assistant Examiner—Joseph A. Orsino, Jr.
Attorney— Howard J. Osborn, William H. King and
John R. Manning
[57] ABSTRACT
A multichannel laser remote control system for use in
areas where radio frequency, acoustic and hardwire
control systems are unsatisfactory or prohibited and
where line-of-sight is unobstructed. A modulated con-
tinuous wave He-Ne laser is used as the transmitter
and a unique 360° light collector serves as the antenna
at the receiver.
4 Claims, 4 Drawing Figures
,13
14-x
\
16 J
'I
OSCILLATOR
OSCILLATOR
OSCILLATOR
OSCILLATOR
20
21
7
MIXER
MODULATOR
POWER
SUPPLY
T
,37
TRACKER
LASER
,28 ,32
12
23
f
TUNED
CIRCUIT
r29
/t5.
38
^
r36
RETRO-
REFLECTOR
COLLECTOR
AND
DETECTOR -
—
-
RELAY
r"
TUNED
CIRCUIT
30^
-
RELAY
r34
TUNED
CIRCUIT
3,
-
RELAY
^35
TUNED
CIRCUIT
WIDE-BAND
FILTER
1
AMPLIFIER
RELAY
V26
-25
3,710,122
1 2
LASER COMMUNICATION SYSTEM FOR FIG. 4 is a schematic drawing of a unique 360° light
CONTROLLING SEVERAL FUNCTIONS AT A collector used in the invention.
LOCATION REMOTE TO THE LASER
DETAILED DESCRIPTION OF THE INVENTION
ORIGIN OF THE INVENTION
 5 _ . . ._ , . .Turning now to the specific embodiment of the m-
The invention described herein was made by em- vention selected for illustration in the drawings, the
ployees of the United States Government and may be number 11 designates a continuous wave He-Ne laser
manufactured and used by or for the Government for which is powered by a power supply 12. Oscillators 13,
governmental purposes without the payment of any 14, 15 and 16 generate frequencies /,, ft, f3 and /4,
royalties thereon or therefor. respectively, which are selectively applied to a mixer
BACKGROUND OF THE INVENTION " by ""^ f "' "^J ar'd;,1 The output of mixer17 is applied to a modulator 22 which modulates the
The invention relates generally to a remote control power supply 12 and hence modulates the beam 23
system and more specifically concerns a multichannel
 15 produced by laser 11. Consequently beam 23 has
laser remote control system that utilizes a unique 360° frequency fi in it if switch 18 is closed, it has frequency
light collector. /2 in it if switch 19 is closed, it has frequency/3 in it if
The development and testing of experimental switch 20 is closed and it has frequency/4 in it if switch
nuclear engines has demonstrated the need for 21 is closed. The portion of the invention in FIG. 1 just
mechanized removal of radioactive debris and waste 20 described constitutes the transmitter,
from the test site due to the radiation hazard. Existing The receiver consists essentially of a collector and
remotely controlled systems, none of which are entirely detector 25 the details of which are disclosed in FIG. 4.
satisfactory, are of three basic types; radio frequency, The output of collector and detector 25 is amplified by
acoustic and hardwire. Radio frequency systems pose a an amplifier 26 and then applied to a wide band filter
problem in that command signals interfere with engine 25 27. The output of filter 27 is applied to tuned circuits
control and monitoring devices; acoustic systems suffer 28, 29,30 and 31. If the output of filter 27 has frequen-
from range limitations and are sensitive to ambient cy/, in it, tuned circuit 28 produces a signal which ac-
noise levels; and hardwire systems are restricted by tuates a relay 32; if the output of the filter has a
cable movements. frequency ft in it tuned circuit 29 produces a signal
It is the primary purpose of the invention to use a 30 which actuates relay 33; if the output of the filter has a
laser in a remote control system to eliminate the disad- frequency /3 in it tuned circuit 30 produces signal
vantages of existing remote control systems. A unique which actuates a relay 34; and if the output of the filter
360° light collector is utilized in the system to increase has a frequency /4 in it tuned circuit 31 produces a
its efficiency. signal which actuates a relay 35. The circuitry used for
SUMMARY OF THE INVENTION CfCh °f tU"ed.?^J^l ™* '??? 3"5 **t
closed in detail in FIG. 3. Each of the relays 32-35
The laser remote control system that constitutes the which is controlled by one of the switches 18-21 at the
invention consists of a transmitter, a receiver, and an transmitter, is connected in an electrical circuit to con-
auto-tracker. The transmitter includes a laser and a ^ trol a predetermined function. For example, the four
plurality of different frequency oscillators for modulat- relays shown could be used to control two d.c. motors
ing the laser beam with one or all of the different in both the forward and backward directions,
frequencies. The receiver includes a unique light col- In the operation of this invention, if one desires to ac-
lector and a tuned circuit for each of the different tuate one of the relays, say relay 33, then all he has to
frequencies. When the light beam from the laser is
 45 do is close switch 19 at the transmitter. This applies
modulated with a particular frequency, the correspond- frequency /2 to mixer 17 whose output is applied to
ing tuned circuit produces a signal which actuates a modulator 22 which modulates the power supply 12
switch causing the function associated with this par- with the frequency/2. Hence, beam 23 of laser 11 has a
ticular frequency to be performed. The autotracker in- frequency component /2 contained in it. When the
eludes a reflector at the receiver, close to the collector 50 beam 23 is received by collector and detector 25, an
for reflecting part of the laser beam back to the trans- electrical signal is produced which has a frequency /2
mitter, and a tracker at the transmitter responsive to contained in it. This signal is amplified and passes
the reflected laser beam for keeping the laser pointed through the wide band filter 27 to tuned circuit 29. The
in the direction of the collector. resulting increased voltage caused by tuned circuit 29
The unique light collector used in this invention con- 55 actuates relay 33.
sists essentially of a conical reflecting surface having a To keep laser 11 pointed in the direction of collector
parabolic curvature. Light from a complete 360° in a and detector 25 an auto-tracker consisting of a retro-
plane striking the conical surface is reflected to a point reflector 36 and a tracker 37 is used. Retro-reflector 36
where it is sensed by a photodetector. is mounted in close proximity with collector and detec-
BRIEF DESCRIPTION OF THE DRAWINGS " tOr 2S f"d rfects ^ of the ««JSy in beam " back
to tracker 37. Apparatus suitable for use as tracker 37
FIG. 1 is a block diagram of a preferred embodiment is shown in block diagram form in FIG. 2. Tracker 37
of the invention; along with laser 11 are mounted on a turntable 39
FIG. 2 is a block diagram of the auto-tracker used in which is free to rotate about an axis 40. The portion of
the invention; beam 23 that is reflected is shown as beam 38 in FIG. 1.
FIG. 3 is a schematic diagram of a tuned circuit and This beam passes through an interference filter 41 and
function relay used at the receiver of the invention; and a lens 42 to a beam-splitting prism 43. Prism 43 splits
3,710,122
beam 38 into two beams one of which is reflected by
prism 44 and detected by photomultiplier tube 45 and
the other of which is reflected by a prism 46 and de-
tected by a photomultiplier 47. Photomultiplier tubes
45 and 47 produce signals proportional to the beams
reflected by prism 43. These signals are amplified by
amplifiers 48 and 49, filtered by filters 50 and 51, and
rectified by rectifiers 52 and 53. The outputs of the two
rectifiers are applied to a null circuit 54, the output of
which is amplified by amplifier 55 and applied to a
motor driver 56 to drive motor 57. If prism 43 splits
beam 38 into two equal beams then the null circuit 54
produces zero output and consequently motor 57 is not
affected. However, if the beams produced by prism 43
are unequal, null circuit 54 produces an output which is
applied to motor 57 to cause it to rotate turntable 39
about its axis 40 until the beams produced by beam
splitting prism 43 are equal. Inasmuch as laser 37 is
mounted on turntable 39, it also rotates with the turnta-
ble until the two beams are equal. Consequently beam
23 is always directed toward collector and detector 25.
A schematic diagram of circuitry suitable for either
of the tuned circuits and relays in FIG. 1 is shown in
FIG. 3. The output of the filter is applied to a capacitor
60 and an inductor 61 connected in series. The sizes of
these two components are such that the circuit
becomes resonant at a desired frequency and produces
a large voltage at the junction of the two components.
This voltage is rectified by a diode 62, a resistor 63 and
a capacitor 64 and then applied to the base of a field-ef-
fects transistor 65. The field-effect transistor 65 is
chosen because it does not load the tuned circuit.
When a voltage is applied to the base of transistor 65, it
becomes conductive and a voltage is produced across a
relay coil 66 which actuates a relay switch 67 to control
the desired function.
A schematic diagram of the collector and detector
25 in FIG. 1 is shown in FIG. 4. The collector is
designated by the numeral 70 and the detector, which
is a photodetector, is designated by the numeral 71.
Collector 70 consists of a polished conical surface 72.
This surface conforms to the surface formed by rotat-
ing segment 73-74 of a parabola 75 about an axis 76.
Axis 76 passes through the focus 77 of parabola 75 and
is perpendicular to parabolic axis 78. The sensing pan
of photodetector 71 is placed at the focal point 77.
Hence all light 79 striking surface 72 from any
direction in a plane parallel to parabolic axis 78 will be
reflected to focal point 77 where it is detected by
photodetector 71.
The advantages of this invention are numerous.
Since the invention operates at optical wavelengths, it
is immune to RF frequency and in turn cannot interfere
20
with RF systems. There is no physical connection
between transmitter and receiver thus eliminating any
possibility of the equipment at the receiver becoming
entangled in its own wires. The unique light collector of
5 this invention provides a uniform sensitivity over a 360°
field of view and focuses all light collected to a point.
The method of demodulating the command signals per-
mits use of a single simple amplifier for multiple com-
mand channels.
10 What is claimed as new and desired to be secured by
Letter Patent of the United States is:
1. A remote control system comprising: a laser for
producing a laser beam; means for producing a plurali-
ty of different frequencies; means for modulating said
j
 5 laser beam with selected ones of said different frequen-
cies; light collector means at a remote location relative
to said laser for collecting light in said light beam from
360° in a plane and focusing it on a point; said light col-
lector means comprises a polished surface that con-
forms to a surface obtained by rotating a segment of
one leg of a parabola about an axis through the focus of
the parabola and perpendicular to the parabolic axis
wherein every point on said segment is a distance from
said focus equal to or greater than the distance along
25 said perpendicular axis from said focus to a point on
said parabola whereby all incident light on said surface
from a complete 360° in plane parallel to said parabolic
axis is brought to a common focus at the focus of said
parabola; means for producing an electrical signal in-
30 dicative of the light at said point; a separate switch as-
sociated with each of said plurality of different frequen-
cies; and means responsive to said electrical signal for
actuating each of said separate switches whose as-
sociated frequency is contained in said electrical signal
35 whereby said plurality of switches can be controlled at
said remote location by said modulating means.
2. A light collector comprising a polished surface
that conforms to a surface obtained by rotating a seg-
ment of one leg of a parabola about an axis through the
4Q focus of the parabola and perpendicular to the parabol-
ic axis wherein every point on said segment is a
distance from said focus equal to or greater than the
distance along said perpendicular axis from said focus
to a point on said parabola whereby all incident light on
45 said surface from a complete 360° in a plane parallel to
said parabolic axis is brought to a common focus at the
focus of said parabola.
3. A light collector according to claim 2 wherein said
surface is a conical surface.
5Q 4. A light collector according to claim 2 including a
photodetector for producing an electrical signal pro-
portional to the light focused by said light collector.
55
60
65


Laser communication system for controlling several functions at a location remote to the laser

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