Canadian Patents Database / Patent 1341533 Summary

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(12) Patent: (11) CA 1341533
(21) Application Number: 235137
(54) English Title: MULTIPLE SPECTRAL BAND OPTO-MECHANICAL MODULATOR
(54) French Title: MODULATEUR OPTICOMECANIQUE A BANDES SPECTRALES MULTIPLES
(52) Canadian Patent Classification (CPC):
  • 88/121
(51) International Patent Classification (IPC):
  • G02B 26/00 (2006.01)
  • G02B 26/08 (2006.01)
(72) Inventors :
  • CLANCY, THOMAS M. (United States of America)
  • RUBIN, EUGENE S. (United States of America)
(73) Owners :
  • BAE SYSTEMS INFORMATION AND ELECTRONIC SYSTEMS INTEGRATION, INC. (United States of America)
(71) Applicants :
  • SANDERS ASSOCIATES, INC. (United States of America)
(74) Agent: GOWLING WLG (CANADA) LLP
(74) Associate agent:
(45) Issued: 2007-07-03
(22) Filed Date: 1975-09-10
(30) Availability of licence: N/A
(30) Language of filing: English

English Abstract




A multiple spectral band opto-mechanical modulator
for obtaining simultaneous but independent modulation of
an extended IR source in two distinct wavelength bands
comprises in one embodiment a first rotating filter wheel
having alternating radial segments of transparent and
short wavepass filter material, a second rotating filter
wheel having alternating radial segments of transparent
and long wavepass filter material, a stationary wheel
having alternating radial transparent and opaque segments
positioned intermediate the first and second rotating
wheels and means for rotating said first and second filter
wheels at predetermined frequencies.


French Abstract

Un modulateur optomécanique à bande spectrale multiple pour obtenir une modulation simultanée, mais indépendante d'une source de rayonnement étendue sur deux bandes de longueurs d'onde distinctes comprend, dans une forme de réalisation, une première roue de filtre rotative dotée de segments radiaux en matériau de passe d'onde courte et transparent, une seconde roue de filtre rotative dotée de segments radiaux alternés de matériau filtrant de passe d'onde longue et transparent, une roue fixe ayant en alternance des segments transparents et opaques radiaux disposés entre les première et seconde roues rotatives et des moyens pour faire tourner lesdits premier et second porte-filtres à des fréquences prédéterminées.


Note: Claims are shown in the official language in which they were submitted.



We Claim:


1. A multiple spectral band opto-mechanical modulator for obtaining
simultaneous but independent modulation of radiation in at least first and
second distinct wavelength bands, comprising:

first modulating means for passing energy in said first band
essentially unmodulated and for providing substantial modulation of
energy in said second band; and

second modulating means receptive to the output of said first
modulating means for passing said modulated energy in said second
band substantially unchanged and for providing substantial modulation
of energy in said first band.

2. Apparatus as recited in Claim 1 wherein said first modulating
means includes:

a first rotating wheel having alternating first and second radial
segments, said first radial segments being substantially transparent to
energy in said first and second bands, said second radial segments being
substantially transparent to energy in said first band and substantially
opaque to energy in said second band;

means for rotating said first wheel at a first predetermined
frequency; and

a stationary wheel positioned adjacent said first rotating wheel
having alternating first and second radial segments, said first segments
being substantially transparent to energy in said first and second bands,
said second segments being substantially opaque to energy in said first
and second bands.






(C) 3. Apparatus as recited in Claim 2 wherein said second modulating
means includes:

a second rotating wheel having alternating first and second radial
segments, said first radial segments being substantially transparent to
energy in said first and second bands, said second radial segments being
substantially transparent to energy in said second band and substantially
opaque to energy in said first band,

said second rotating wheel being positioned adjacent said stationary
wheel; and

means for rotating said second wheel at a second predetermined
frequency.

4. Apparatus as recited in Claim 3 wherein said first rotating
wheel comprises a transparent material having a first filter material
thereon to form said second radial segments.

5. Apparatus as recited in Claim 4 wherein said second rotating
wheel comprises a transparent material having a second filter material
thereon to form said second radial segments.

6. Apparatus as recited in Claim 5 wherein said transparent material
is selected from the group consisting of:

quartz;
glass; and
sapphire.



11



(U) 7. Apparatus as recited in Claim 1 further including:

third modulating means coupled to said second modulating means
for superimposing modulation on energy in one of said bands.

(C) 8. Apparatus as recited in Claim 7 wherein said third modulating
means includes:

a rotating wheel having first and second radial segments, said
first radial segments being substantially transparent to energy in said
first and second bands, said second radial segments being substantially
transparent to energy in one of said bands and substantially opaque to
energy in said other band; and

means for rotating said wheel at a predetermined frequency.

(C) 9. Apparatus as recited in Claim 7 wherein said third modulating
means includes:

a rotating vane modulator having vanes substantially transparent to
energy in one of said bands and substantially opaque to energy in the other
of said bands; and

means for driving said vane modulator.

(C) 10. Apparatus as recited in Claim 1 wherein said first modulating
means includes:

a first plurality of vanes mounted for rotation about a like first
plurality of parallel axes disposed in substantially a single first plane,
each
axis separated from adjacent axes by a distance comparable to the width of
said vanes, said vanes being substantially transparent to energy in said
first band and substantially opaque to energy in said second band; and

means for driving said first plurality of vanes.



12



(C) 11. Apparatus as recited in Claim 10 wherein said second modulating
means includes:

a second plurality of vanes mounted for rotation about a like

second plurality of parallel axes disposed in substantially a single second
plane, each axis separated from adjacent axes by a distance comparable
to the width of said vanes, said vanes being substantially transparent to
energy in said second band and substantially opaque to energy in said first
band; and

means for driving said second plurality of vanes.

(C) 12. A multiple band mechanical modulator for obtaining simultaneous
modulation of radiation in at least first and second distinct wavelength
bands, comprising:

first and second filter wheels each including a plurality of first
and second groupings of radial segments;

said first groupings of radial segments having alternating first and
second radial segments, said first radial segments being substantially

opaque to energy in said first and second bands, said second radial segments
bei
being substantially transparent to radiation in said first band and sub-

stantially opaque to energy in said second band;

said second groupings of radial segments having alternating third and
fourth radial segments, said third radial segments being substantially
transparent to radiation in said second band and substantially opaque to
energy in said first band, said fourth radial segments being substantially
transparent to energy in said first and second bands, and

means for rotating one of said filter wheels.



13

Note: Descriptions are shown in the official language in which they were submitted.


3:i 41 5 3 3

MULTIPLE SPECTRAL BAND OPTO-MECHANICAL MODULATOR
Background of the Invention

Prior to the present invention modulation of a large
aperture radiation source was achieved by placing in front
of such source a rotating and stationary wheel of

alternating opaque and transparent radial segments. In
this arrangement all wavelengths are modulated with the
same temporal waveform. For certain applications it is
necessary to modulate a single radiation source to provide

simultaneously distinct outputs in different spectral
regions and at different pulse repetition frequencies.
Summary of the Invention

Accordingly, it is ari object of this invention to
provide a new and novel mechanical modulator.

It is another object of this invention to provide a
mechanical modulator to obtain simultaneously but
independently radiation iri distinct spectral regions at
different pulse repetitiori frequencies.

Briefly, in one embodiment a mechanical modulator
which provides

-1-


' .. _ .~ . .. _ >~
simultaneously two distinct signals in two spectral regions at different
pulse repetition frequencies includes three wheels: a first filter wheel
rotating at a first velocity having first and second alternating radial seg-
ments, said first segments being transparent at both spectral regions and

said second segments being transparent at the shorter of the two spectral 5
regions and opaque at the longer; a second filter wheel rotating at a second
velocity having first and second alternating radial segments, said first
segments being transparent at both spectral regions and said second

segments being transparent at the longer of the two spectral regions and

opaque at the shorter; and a third wheel which is stationary, also having 10
first and second alternating radial segments, said first segments being
transparent at both spectral regions and said second segments being opaque

at both spectral regions. This third wheel is arranged intermediate the
first and second filter wheels. When the rotating filter wheels are spun

past the stationary wheel modulation is obtained in that spectral region 15
where the segments are opaque; the first nilter wheel modulates the longer
wavelengths and vice versa.

(U) If desired, additional modulating wheels or other types of modulators
may be used to superimpose modulation on the outputs from the afore-

mentioned modulator. 20
Brief Description of the Drawings

(U) The above-mentioned and other features and objects of this invention
will become more apparent by reference to the following description taken
in conjunction with the accompanying drawings, in which:

(U) FIG. 1 is a sketch of a three wheel rnodulator of utility in the practice
25
of the present invention;

2-
~I


4 5 3 3

(U) FIG. 2 is a sketch illustrating the passbands of the.filters employed
in the modulator of FIG. 2; -

(U) FIG. 3 is a sketch showing the output from the modulator of FIG. 1
at two different spectral bands;

(U) FIG. 4 is a sketch of another embodiment of a rnultiband niodulator 5
of utility in the practice of the present invention;

(U) Fig. 5A is a sketch of a modification of the modulator of Fig.l;
Fig. 5B is a sketch illustrating a typical output of the
modulator of Fig. 5A;
(U) FIG. 6 is a pictorial representation illustrating a means for supporting
and driving the modulator of FIG. 1; and

(U) FIGS. 7A-7C are sketches illustrating an alternative modulator re- 10
quiring only two wheels.

Description of Preferred Embodiments

(C) Referring now to FIG. 1, there is illustrated thereby a first embodi-

ment of a mechanical modulator which provides simultaneously but independe t
modulation of a radiation source in two distinct spectral wavelength bands 15
and'1 The modulator comprises three wheels 10, 12 and 14

having substantially identical segments thereon. Wheels 10 and 14 are
rotating filter wheels while wheel 12 is a stationary wheel. For clarity
and purposes of illustration, the means for rotating filter wheels 10 and 14

are for holding the wheels in a fixed relationship to each other are not 20
shown in this FIG. (see FIG. 6). The wheels are normally znaintained

next to a source of radiation (not shown). The wheels are spaced as close
to each other as physically practical in order to minimize waveguiding
effects and direct radiation at large field angles. The radiation 16 impinges

on filter wheel 14 first in this embodiment, however, in alternate e:nbodi- 25
rnents the arrangement could be reversed with wheel 10 positioned adjacent

tize source of radiation.

(C) Filter wheel 14 is made up of alternate radial segments 18 and 20.
5eo:nents 18 are transparent to both spectral wavelength bands of interest.

3 - ~


13 4 1 - 33

Segments 20 have a transmission characteristic substan-
tially as shown in diagram A of FIG. 2, that is, over the
band shown as AA1 substantial amounts of radiation will
pass through these segments while radiation of longer

wavelengths will be blocked thereby.

Filter wheel 14 is made of a material which will pass
the desired bands. Quartz, glass, sapphire, or silicon,
for example, could be used depending on the bands of
interest. The segments 20 are constructed by a deposition

of filter material on one side of the filter wheel 14.
Such filter material will have the transmission
characteristics as shown in diagram A of FIG. 2. The
filter materials can be evaporated on by a vacuum
deposition process. Dielectric multilayer interference

type filters have been deposited on a substrate with
success.

Filter wheel 12 is made up of alternate radial
segments 22 and 24. Segmerits 22 are transparent to both
spectral wavelength bands of interest and segments 24 are

opaque thereto. Preferably filter wheel 12 is a metal disc
having slots 22 therein. Wheel 12 is preferably plated on
the side facing the energy source to reflect energy so
that the wheel will absorb as little energy as possible.
The other side of wheel 12 is blackened to improve the

emissivity of the material and, thus, minimize blade
heating.

When filter wheel 14 is rotated with respect to
stationary wheel 12, there is provided a modulation of the
incident radiation 16. All energy in the A1,1 band goes
through the filter segments 20 essentially unmodulated as,
of course, does that through the transparent sections 18.
Actually, the energy in the AX1 band exiting the stationary
wheel will have some slight ripple, perhaps 10% or 15%
thereon due to the difference in transmissibility between
the filter segments 20 and the clear segments 18, since
the filter segments 18 are not as transparent as segments
20 in the band DA1.

The energy in the A1~2 band as shown in diagram B of
FIG. 2 is essentially blocked by the filter sections 20 of
wheel 14, while energy in

-4-


1 4153 this band passes through the trardsparent sections 18. Thus, in
conjunction

with stationary wheel 12 there is prav?ded substantially 100% modulation of
the energy in the Z;'',,-, band. T'his modulated signal essentially passes
through wheel 10 undisturbed, as will be described hereinafter, to pruvide

a signal substantially as shown in waveform A of FIG. 3. 5
(C) Filter wheel 10 is made up of alternate radial segments 26 and 28.

Segments 28 are transparent to both spectral wavelength bands of interest.
Segments 26 have a transmission characteristic substantially as shown in
diagram B of FIG. 2, that is, over the band substantial arnounts of

radiation will pass through the segments 26 and shorter wavelengths will 10
be blocked thereby.

(U) Like filter wheel 14, filter wheel 10 is also made of a material which
will pass both the desired bands, and again the segments 26 are constructed
by deposition of filter materials to provide the desired transmission

characteristics. 15
(C) Thel energy, which is essentially unmodulated by filter wheel 14,

as described above, except for a slight ripple thereon, is modulated
by the filter wheel 10 in conjunction with wheel 12. The energy
passes through the clear segments 28 while it is blocked by the filter

segments 26, thus providing a signal substantially as shown in waveform B 20
of FIG. 3.

(C) Although filter wheels have been shown in the embodiment previously
described to obtain sirnultaneous amplitude modulation of a radiation source
in two distinct spectral wavelength bands, this is only the preferred

method of deriving this result. FIG. 4 illustrates an alternative arrange- 25
ment.

I


13 41 53~

Radiation from a source 30 is directed to a modulator
32 which comprises individual rotating vane type
modulators 34 and 36 driven by motors 35 and 37, respec-
tively. These rotating varle modulators are well known,

however, in this embodiment the individual vanes 38 and 40
are constructed of materials which filter the radiation
from the source 30 in a predetermined manner. For example,
the vanes are constructed of quartz with a filter material
deposited thereon. In the embodiment shown, modulator 34
includes vanes 38 having a transmission characteristic
substantially as shown by diagram A of FIG. 2, and
modulator 36 includes vanes 40 having a transmission
characteristic substantially as shown by diagram B of FIG. 2.
Two distinct signals are provided by this arrangement
in the manner previously described since the rotating
vanes are substantially equivalent to the rotating and
stationary wheel combinations previously described. When
vanes 38 are orientated vertically, only LA1 radiation will
pass through the vanes, and when vanes 38 are rotated

horizontally all radiatiorl will pass through. Therefore,
the modulator 34 provides radiation output of the type
shown in waveform A of FIG. 3, although more rectangular
in shape. Similarly, modulator 36 provides modulation of
the type shown in waveform B of FIG. 3, although, again,

more rectangular in shape.
As mentioned previously, further superimposed
modulation on either or both fundamental signals shown in
FIG. 3 can be achieved by providing additional modulating
members. This is illustrated in FIG. 5A where the output
of radiation source 30 is directed to a modulation system
comprising wheels 10, 12, 14 as previously described, as
well as a further wheel 42. Wheel 42 is constructed in the
same manner as wheels 10 and 14, and is used to further
amplitude modulate one of the signals shown in FIG. 3 and

preferably, that of the wheel which is the closer.
-6-


~341 53)4~

For exa...e:e, if it is desired to modulate the signal shown in waveform B
of FIG. 3, then wheel 42 would have transmission characteristics similar
to wheel 10.

(C) It is obvious that wheel 42 could be replaced by a vane type modulator

as shown in FIG. 4 and that various combinations of rotating vane and filter 5
wheel modulators can be employed in the manner taught herein.

(C) FIG. 6 illustrates a reduction to practice of the multiple band mechan-
ical modulator of FIG, 1. Stationary wheel 12 is mounted in a housing 50
using screws 52. The rotating -wheels 10 and 14 are mounted on rings 54

and arranged on either side of stationary wheel 12. For clarity purposes, 10
only one side of housing 50 is shown with wheel 10 arranged thereon. Wheel

14 is arranged similarly on the reverse side of the housing.

(C) Wheel 10 is arranged in position on the housing by having the shoulder of
ring 54 arranged in guide rollers 56, 58 and a spring loaded friction drive

wheel 60. Constant pressure is maintained on the wheel 10 by a lever 62. 15
The friction drive wheel 60 receives rotational energy from a motor 64

through a wheel on its shaft which is not shown in the Figure. Wheel 14

on the reverse side of the housing likewise receives power from a motor 66.
(C) A magnetic pickoff 70 is arranged proxiinate the wheel 10 to act as a

chopping frequency mcnitor. The magnetic pickoff operates in conjunction 20
with at least one or rnore of screws 72 which is magnetic.

(C) Arranged on the other side of the shafts of motor 64, 66 are a pair of
corresponding tachometers which in a rate servo arrangement permit
controlled speeds of the wheels 10 and 14 to produce a desired output

frequency. 25
(C) Referring now to FIGS. 7A-7C, there is illustrated thereby another
embodiment of a multiple spectral band opto-mechanical modulator. This

,
i) -7-


4 1 5 3 a

embodiment requires two filter wheels and no third wheel. Two identical
filter wheels 80 and 82 are used to provide simultaneously two distinct
amplitude modulators in two distinct wavelength bands. The filter wheels 80
and 82 are positioned so as to receive radiation 84. Wheel 82 is a rotating

wheel while wheel 80 is a stationary wheel. 5
(C) The wheels 80, 82 are shown in detail ir. FIG. 7A and include alter-

nating first and second groupings of radial segments 86 and 88. Only one
each of said groupings are illustrated; however, the wheel is completely
filled with said alternating groupings. Groupings 86 comprise alternate

radial segments 90 and 92. 10
(C) Segments )0 are substantially opaque to both spectral bands of

interest and A' ). Segments 92 have a transmission characteristic
..~.
substantially as shown in diagram A of FIG. 2, that is, over the band
shown as LAI il , substantial amounts of radiation will pass through these

segments while radiation of larger wavelengths will be blocked thereby. 15
(C) Groupings 88 comprise alternate radial segments 93 and 94. Segments

33 have a transmission charact.e:-istic substantially as shown in diagram B
of FIG. 2, that is over the banci shown as substantial amounts of
radiation will pass through these segments while radiation of shorter

wavelengths will be b'ocked thereby. Segments 94 are transparent to both 20
spectral bands of interest ( f1 and ZS .h, ).

(C) In this arrangement no third wheel is required and two outputs are
obtained as shown in FIG. 7C. The only drawback to this arrangement is
that the frequencies of the two signals a and b are not completely in-

dependent of each other as in the earlier described embodiments. As in 25
the manner of FIG. 5A additional means may be employed to further

modulate one of the signals.

-8_


~3 3

(U) Although the modulators have been described in conjunction with a
radiation source, it is obvious that they could also be used to modulate
a signal into the detector of a receiver. Thus, it is to be understood

that the embodirrients shown are illustrative only and that many variations

and modification.s may be made without departing from the principles of 5
the invention herein disclosed and defined by the appended claims.

! -~-

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Admin Status

Title Date
Forecasted Issue Date 2007-07-03
(22) Filed 1975-09-10
(45) Issued 2007-07-03
Lapsed 2015-07-03

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Filing $0.00 1975-09-10
Maintenance Fee - Patent - Old Act 2 2009-07-03 $100.00 2009-06-17
Maintenance Fee - Patent - Old Act 3 2010-07-05 $100.00 2010-06-17
Maintenance Fee - Patent - Old Act 4 2011-07-04 $100.00 2011-06-17
Maintenance Fee - Patent - Old Act 5 2012-07-03 $200.00 2012-06-18
Maintenance Fee - Patent - Old Act 6 2013-07-03 $200.00 2013-06-17
Current owners on record shown in alphabetical order.
Current Owners on Record
BAE SYSTEMS INFORMATION AND ELECTRONIC SYSTEMS INTEGRATION, INC.
Past owners on record shown in alphabetical order.
Past Owners on Record
CLANCY, THOMAS M.
LOCKHEED CORPORATION
LOCKHEED MARTIN CORPORATION
LOCKHEED SANDERS, INC.
RUBIN, EUGENE S.
SANDERS ASSOCIATES, INC.
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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Document
Description
Date
(yyyy-mm-dd)
Number of pages Size of Image (KB)
Description 2007-07-03 9 377
Cover Page 2007-07-03 1 15
Drawings 2007-07-03 5 100
Claims 2007-07-03 4 154
Abstract 2007-07-03 1 19
Examiner Requisition 1977-12-28 2 90
Prosecution Correspondence 1978-05-31 1 41
Prosecution Correspondence 2007-03-13 2 61
Office Letter 1975-09-10 1 24