Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2001-07-23
2003-02-04
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S366000
Reexamination Certificate
active
06515403
ABSTRACT:
TECHNICAL FIELD
The present invention relates to path length control apparatus (PLC) for optical devices and in particular to a co-fired piezoelectric transducer that can be used in a PLC for a ring laser gyroscope and method of making the same.
BACKGROUND OF THE INVENTION
A ring laser gyroscope (RLG) is commonly used to measure the angular rotation of an object, such as an aircraft. Such a gyroscope has two counter-rotating laser light beams that move within a closed loop optical path or “ring” with the aid of successive reflections from multiple mirrors. The closed path is defined by an optical cavity that is interior to a gyroscope frame or “block.” In one type of RLG, the block includes planar top and bottom surfaces that are bordered by six planar sides that form a hexagon-shaped perimeter. Three planar non-adjacent sides of the block form the mirror mounting surfaces for three mirrors at the comers of the optical path, which is triangular in shape.
Operationally, upon rotation of the RLG about its input axis (which is perpendicular to and at the center of the planar top and bottom surfaces of the block), the effective path length of each counter-rotating laser light beam changes and a frequency differential is produced between the beams that is nominally proportional to angular rotation. This differential is then optically detected and measured by signal processing electronics to determine the angular rotation of the vehicle. To maximize the signal out of the RLG, the path length of the counter-rotating laser light beams within the cavity must be adjusted. Thus, RLGs typically include a path length control apparatus (PLC), the purpose of which is to control the path length for the counter-rotating laser light beams for maximum signal.
One such known PLC
10
for a block
12
of a RLG
14
is illustrated in
FIGS. 1-2
. The PLC
10
includes a piezoelectric transducer (PZT)
16
which is secured to a mirror
18
via an epoxy-based adhesive
20
. The epoxy adhesive
20
completely covers the interface (defined by a lower surface
22
of the PZT
16
and an upper surface
24
of the mirror
18
) between the PZT
16
and the mirror
18
. The mirror
18
is secured to a mirror mounting surface
26
of the optical block
12
. The mirror
18
communicates with laser bores
32
(only partially shown) of an optical cavity
34
(only partially shown) of the block
12
. The bores
32
partially form a portion of the closed loop optical path
38
defined by the optical cavity
34
. As seen in
FIG. 1
, the mirror
18
reflects counter-rotating laser light beams
40
at its respective corner of the closed loop optical path
38
.
Conventional PZT
16
(perhaps shown best in
FIG. 2
) is defined by a pair of piezoelectric elements
42
and
44
. A conductive tab
45
is sandwiched between the elements
42
and
44
, which are bonded to the conductive tab
45
by thin layers of conductive epoxy. Opposite polarity conductive tabs
41
and
43
are adhered to the outer major surfaces of elements
42
and
44
, respectively, also by thin layers of conductive epoxy. The opposite polarity leads
47
and
49
extend from the positive conductive tabs
41
and
43
, respectively. Another lead
48
extends from the negative conductive tab
45
. As shown in
FIG. 1
, the opposite polarity leads
47
and
49
are electrically connected to form a single lead
46
, and the leads
46
and
48
extend from the PZT
16
and are connected to terminals
50
and
52
of a wireboard element
54
. Leads
58
and
59
extend from the terminals
50
and
52
, respectively, of the wireboard element
54
and are coupled to a regulated voltage source (not shown) which is in turn coupled to a detector (not shown) which monitors the intensity of the light beams
40
. The PZT
16
takes an applied voltage delivered by the regulated voltage source, in response to a signal provided by the detector, and turns this voltage into small but precisely controlled mechanical movement. This mechanical movement of the PZT
16
affects translational movement (as represented by double-headed arrow
60
) of the mirror
18
, and thereby controls the laser light beam path length.
SUMMARY OF THE INVENTION
The present invention is a multi-layer PZT fabricated as a multi-layer ceramic assembly. The multi-layer PZT of the present invention has contacts, which are electrically connected to other layers within the multi-layer PZT, formed directly on the top layer of the PZT, and the regulated voltage source can be coupled directly to the PZT at the top layer contacts. The present invention is a multi-layer piezoelectric transducer that can be used as a path length control apparatus of an optical device. The multi-layer piezoelectric transducer includes a plurality of ceramic layers so as to form a stack, wherein each ceramic layer has first and second opposing surfaces. The plurality of ceramic layers includes a top layer at a first end of the stack having a top conductive pattern formed on the first surface thereof. The top conductive pattern includes a negative contact and a positive contact. The plurality of ceramic layers also includes at least one poled ceramic layer having a conductive pattern formed on the first surface thereof. The plurality of ceramic layers include additional poled ceramic layers having alternating conductive patterns formed on the first surface thereof.
REFERENCES:
patent: 3281613 (1966-10-01), Hatschek
patent: 3390287 (1968-06-01), Sonderegger
patent: 3474268 (1969-10-01), Rudnick
patent: 4523121 (1985-06-01), Takahashi et al.
patent: 4742264 (1988-05-01), Ogawa
patent: 4759107 (1988-07-01), Ogawa et al.
patent: 5153477 (1992-10-01), Jomura et al.
patent: 5438232 (1995-08-01), Inoue et al.
patent: 6121718 (2000-09-01), Mohr, III
patent: 6414418 (2002-07-01), Heinz et al.
Mortenson Douglas P.
Schober Christina M.
Sittler Daniel L.
Bremer Dennis C.
Budd Mark O.
Honeywell International , Inc.
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