ELECTROSTRICTIVE SENSORS AND ACTUATORS

Abstract: A method of fabricating an electrostrictive heterogeneous bimorph for sensing and actuating which includes depositing a ZnO layer on a layer of Si3N4. The electrostrictive material is biased to a voltage to induce a strain. The resulting large amplitude of deflection exhibits quadratic dependence on the applied voltage.

Description: ELECTROSTRICTIVE SENSORS AND ACTUATORS Background of the Invention This invention relates generally to dielectric materials, and more particularly to a heterogeneous electrostrictive bimorph for actuating and sensing objects. Typically, electricity or electric polarity can result from the application of a mechanical pressure (i.e, stress) placed upon a piezoelectric material. A mechanical stress that is applied to a piezoelectric material generates an electric polarization (electric dipole moment per cubic meter) proportional to the stress, If the material is isolated, the polarization manifests itself as a voltage across the material. Conversely, application of a voltage between the material produces a mechanical distortion of the material. This reciprocal relationship is known as the piezoelectric effect. Thus, piezoelectric materials will expand or contract when positioned within an electric field. The expansion or contraction of piezoelectric materials depend upon the polarity of the applied electric field. A piezoelectric bimorph can be formed by securing a film of piezoelectric material to a flexible beam or by joining two piezoelectric materials together to form a composite cantilever beam. The beam has a free portion that can be deflected in a precise and predetermined manner as an electric field is applied. Generally, the beam is deflected in a perpendicular direction. Piezoelectric bimorph structures have a wide range of applications, such as in transducers, pumps, vibrating structures, computers, motors, etc. A heterogeneous piezoelectric bimorph is formed by depositing a single layer of piezoelectric material on a layer of non-piezoelectric material. The piezoelectric heterogeneous bimorphs undergoes deflection when an electric field is applied thereto. Typical piezoelectric heterogeneous bimorph use piezoelectric material such as PLZT, PZT, and PVF 2 . These bimorphs have been used in telephone receivers, thickness extensional mode resonators, PLFET accelero eters, resonant diaphragm pressure sensors, resonant force sensors, monolithic band¬ pass filters made of cantilevers, dampers in vibrational control of beams and regulators of vibration modes of rectangular plates to control sound radiation. Summary of the invention In accordance with a preferred embodiment of the present invention, there is provided an electrostrictive heterogeneous bimorph including a substrate layer and a dielectric layer deposited over the substrate layer. The electrostrictive layer exhibits the electrostrictive property that distinguishes itself from the piezoelectric property in that the deformation is proportional to the square of the electric field as opposed to the linear dependence of the deformation on the electric field of the piezoelectric material. The electrostrictive layer is biased at a voltage that induces a deflection of the bimorph. Note that a small change in the applied voltage causes a change in the deflection that is approximately linear with the applied voltage change so that the deflection of the beam can be characterized by the sum of both linear and quadratic components. Preferably, the substrate layer is silicon nitride and the dielectric layer is a chemical compound consisting of elements selected from Groups II and VI of the periodic table. A preferred material for the dielectric layer and the substrate layer is ZnO and Si 3 N 4 , respectively. The substrate layer and the dielectric layer can have a thickness ratio that approximates unity, however, this ratio can vary considerably depending upon the specific application and the material used in the bimorph structure. The heterogeneous bimorph has particular use in actuating and sensing fluids or objects. More specifically, the present invention, due its large deflection as a function of voltage, has use in deflecting light beams, such as in laser printers, range finders, laser scanners such as in bar code readers, or in fiber optic address systems. These systems can be controlled by a microprocessor and control circuitry some or all of which can be integrated monolithically on a single chip. The present invention further includes a preferred method of fabricating an electrostrictive heterogeneous bimorph comprising several steps. First, a sacrificial layer is deposited, then a dielectric material such as Si 3 N 4 is deposited. On top of this, a conductor is deposited on which the electrostrictive material is deposited. Next, a second electrical contact is provided over the electrostrictive material. Finally, a sacrificial layer underlying the structure is removed to form an electrostrictive bimorph actuator or sensor such as a cantilever beam. While the present invention will hereinafter be described in connection with a preferred embodiment and method of use, it will be understood that the particular electrostrictive heterogeneous bimorph embodying the invention is shown by way of illustration and it is not intended that the present invention be limited to this embodiment. Instead, it is intended to cover all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the present invention as defined by the appended claims. Brief Description of the Drawings Figure 1 is a top view of an electrostrictive heterogeneous bimorph made in accordance with the invention. Figure 2 is a cross-sectional view of the electrostrictive heterogeneous bimorph. Figures 3A-3G is an illustration of a fabrication sequence of the electrostrictive heterogeneous bimorph. Figure 4 is a graph of the deflection of the electrostrictive heterogeneous bimorph versus a DC voltage. Figure 5 is an illustration of an electrostrictive actuator for addressing optical fibers. Figure 6 is an illustration of an electrostrictive sensor used as a range finder to sense the position of an object. Figure 7 is an illustration of an electrostrictive actuator for deflecting a laser beam. Figure 8 is an illustration of an electrostrictive actuator used as an accelerometer. Figure 9 is a schematic illustration of a drive circuit used to operate the electrostrictive bimorph. Detailed Description of the Preferred Embodiment Top and cross sectional views of a preferred embodiment of an electrostrictive heterogeneous bimorph device of the present invention are shown in Figures 1 and 2, respectively, the device being designated generally by reference numeral 10. The bimorph structure includes a silicon substrate 12 and a layer of a dielectric material such as ZnO 14 formed over the silicon substrate 12 to provide a cantilever beam 10 that can be deflected at one end relative to the substrate. The dielectric material is not limited to ZnO and can include any chemical compound consisting of elements selected from Groups II and VI of the periodic table which exhibit electrostrictive behavior. Two electrodes 16 and 18 positioned on opposite sides of the ZnO layer 14 are used to apply an electric field to layer 14 causing the bimorph to deflect at one end. This system is referred to generally as the bending system 20. Contact pads 22 and 24 are used to electrically connect the electrodes 16 and 18, respectively, to a drive circuit including controller 39 that operates the bimorph. The drive circuit can be integrated into the semiconductor wafer or chip in which the bimorph has been formed. The bimorph can be positioned in a "moat" formed in or on substrate 12. The bimorph can also include a vibrating system 26 with separate electrodes 25 and 27 and contacts 32 and 34. The vibrating system 26 and a sensing system 36 with electrodes 28 and 30 can be used as a tactile sensor. The determination of the position of objects by the tactile sensor, is done as follows: the bean is deflected towards the test object by means of a slowly varying voltage across the bending raised, it is also sent into vibration electrode system. The vibration of the beam will enhance crispness of contact with the external object. When the sensing part of the beam hits the object, al electrical signal will be picked up by the sensing electrode system. Circuit 39 will process the signal and hold the bending voltage at its level. From the bending voltage, the position of the external object can be determined. The heterogeneous bimorph is formed in the manner illustrated in Figures 3A-G • The specific processing conditions and dimensions serve to illustrate the present method but can be varied depending upon the materials used and the desired device geometry. First, a (100) silicon wafer 40 is oxidized in dry oxygen at 1150°C to obtain 0.5 μm of masking oxide 42 (Figure 3A) . An array of windows 46 are patterned onto the silicon wafer using photolithography (Figure 3B) In this example, the windows are rectangular with dimensions of 3.11 mm by 0.96 mm. Silicon dioxide (Si0 2 ) inside the windows is then etched away in Buffered Oxide Etch (BOE) . A sacrificial layer 48 of Zinc Oxide (ZnO) of 1.0 μm thick is deposited onto the wafer by magnetron sputtering at a pressure of 4 x 10' 2 Torr. The sputtering is done from a zinc target in a pure oxygen atmosphere at a power level of 600 W. The ZnO film outside the rectangular windows is etched away in a mixture of Phosphoric acid, Acetic acid and water (1:50:50) (Figure 3C) . A layer 49 of silicon nitride (Si 3 N 4 ) 1 μm thick is then sputtered onto the wafer from a (Si 3 N 4 ) target in a pure Ar atmosphere. A layer 50 of Chromium-Gold is evaporated on top of the silicon nitride (Si 3 N 4 ) to define the bottom electrodes (Figure 3D) . A 1 μ thick film 52 of ZnO is then sputtered and patterned on top of the bottom electrodes 50. The same parameters for the sputtering process are used as for the sacrificial ZnO 48. A second layer 54 of Chromium-Gold is evaporated onto the wafer to define the top electrodes (Figure 3E) . This step completes the construction of the critical components of the sensor. The device is now ready to be etched free. Photoresist 56 is spin-coated onto the wafer and patterned with a mask that exposes the necessary areas of the Si 3 N 4 that have to be etched in order to make the cantilever beam structure of the device (Figure 3F) . The Si 3 N 4 is etched in BOE until the sacrificial ZnO is reached. With the same photoresist still in position, the sacrificial ZnO underneath the Si 3 N 4 is etched in a mixture of Acetic acid, Phosphoric acid and water until the length of the cantilever beams is free from the Silicon substrate. The resulting structure is a piezoelectric heterogeneous bimorph having a cantilever beam that can be designed to curve upwards by proper mismatch of the coefficient of thermal expansion of the material in the beam. In this example, the bimorph has a length of about 3mm and can be deflected about 1mm as a biasing voltage is applied. Biasing the heterogeneous bimorph 10 with a DC voltage ranging from about -8.0 volts to about +8.0 volts across the electrode via the bonding pads causes the cantilever beam to undergo deflection. Also, the bimorph 10 will undergo deflection when an AC voltage is applied. The deflection of the free end of the bimorph is the measure of the difference between the position of the free end with voltage applied and the initial position at a zero input voltage. The maximum deflection that the bimorph of the present invention will undergo is about 1 mm, whereas the maximum deflection of a conventional piezoelectric heterogeneous bimorph having PZT material is about the same. Figure 4 shows a graph of the deflection of the heterogeneous bimorph versus the DC voltage applied to the bimorph. Hysteresis is present in Figure 4 as evidenced by the "Butterfly" shape of the curve. The deflection of the heterogeneous bimorph undergoes saturation at voltage magnitudes larger than 6V. This data was obtained by fabricating sensors having beam lengths of 2980 microns and 1688 microns and testing then under a probing station, which is equipped with a 3OX optical microscope and a reticle with a resolution of 33.3 μm per unit on the eye- piece. A DC voltage was applied across bender electrode areas via the bonding pads. In order to observe any hysteresis effects, the bending voltage was lowered first from 0V to -6.5V uni-directionally with small increments. From -6.5V, the voltage was raised uni-directionally back to 0V. From 0V, the voltage was increased to 6.5 V and then decreased back to OV. The position of the free tip of the sensor was read off from the reticle at various input voltages. The deflection of the free end due to an input voltage was obtained as the difference of the position of the free end from its initial position at zero input voltage. The quadratic behavior of the graph in Figure 4 indicates that the heterogeneous bimorph responds strongly to the voltage amplitudes, but does not respond to the polarity of the applied voltages. For example, the return paths of the heterogeneous bimorph have smaller downward deflections in the high electric field regions and larger upward deflections in the low electric field regions. The behavior of the biased heterogeneous bimorph can be explained by its constituent equations. The deflection of the bimorph due to an external voltage is given as δ(V)= 2i- V (i) where _. « (s.?) 2 ( p) « +4s_ , sf_Λ, i (A p ) 3+6 Si_*s__ (h βi ) -(Λ_) 2+ 4s * 1 s 1 p .--.(Λ fli ) 3 + ( s f 1 ) 2 ( Λ fii ) 4 s__" and sf_ are the elastic compliances of the Si 3 N 4 and ZnO respectively, h, ; and h. are the thickness of Si 3 N 4 and ZnO respectively, d is the piezoelectric constant of ZnO, and L is the length of the bender. For the heterogeneous bimorph of the present invention, assume that h„, h_, ε π *', s n p , L and d 31 have the following values: h. = 1.0 μ Sn" = 17.8 X 10- 12 m 2 /N S u p = 8 . 1 X 10- 12 m 2 /N L = 2583 μm d 3 , = -5 . 12 X 10- ,2 m/V . Using these values, the deflection according to equation (1) becomes δ(V) =12 x 10 "6 V (2) Equation (2) is shown in Figure 4 as the dotted line intersecting the origin. The piezoelectric effect as represented by this line is not sufficient to explain the near symmetrical plot of Figure 4. A straight line through the data points in the left branch gives a slope value of 309 μm/V for a negative bias voltage of 4 volts. If a least-squares curve fit is performed to the data shown in Figure 4 with a quadratic polynomial V, the following coefficients are obtained: δ(V) =128.38_-10- 6 + 12.56 xlO -6 V-31.15xlO^V 2 From the curve fitting it is apparent that an electrostrictive effect is present. An electrostrictive effect has a quadratic relationship between the deflection of the bimorph to the electric field, such that the dielectric material always contracts regardless of the polarity of the field. Electrostriction is a form of elastic deformation or strain of a dielectric material that is induced by an electric field. The elastic strain is independent of reversal of the field direction. Electrostriction is a property of all dielectrics and is distinguishable from the piezoelectric effect in that a field-induced strain does not change sign upon field reversal. The bimorph 10 of the present invention exhibits both piezoelectric and electrostrictive behavior. However, the magnitude of the electrostrictive response is substantially greater than the piezoelectric response of the material employed. In the present invention, the silicon substrate layer and the piezoelectric layer have a thickness ratio approximating unity. A thickness ratio approximating two (2) results in a heterogeneous bimorph with optimal energy transfer characteristics, when the bimorph is used as a motor element. But a voltage applied to a bimorph having a thickness ratio of one half will have the greatest amount of deflection for the bimorph. The bimorph can also be fabricated using a semiconductor layer such as silicon. The fabrication of such systems is described extensively in U.S. Patent 5,049,775, the contents of which are incorporated herein by reference. Typically, the maximum amount of deflection for a silicon substrate layer having a thickness ranging from 1 μ to about 100 μ is about 1 mm. The heterogeneous bimorph of the present invention can be employed in a number of different applications because of its electrostrictive nature. For example, Figure 5 shows the heterogeneous bimorph 10 used as an actuator 58 for addressing and coupling a plurality of optical fibers 60. In this particular embodiment, the actuator 58 is coupled to a microprocessor 62 and a light source 64. The microprocessor controls the amount of biasing voltage applied to the electrostrictive heterogeneous bimorph, which in turn causes the actuator to move in small increments. In this particular application, the actuator 58 moves in a horizontal and vertical direction to address the plurality of optical fibers 60. Thus, the light source 64 is able to fully address each and every optical fiber 60. The actuator of the type described in Figures 1 and 2 can also be used to cool electronic equipment, mix liquids, pump a fluid, and control damping in vibrating structures. A discussion of how an electrostrictive bimorph actuator can perform mechanical work in the above application against various spring-type loads is provided in Smits, "The Effectiveness of a Piezoelectric Bimorph to Perform Mechanical Work Against Various Spring-Type Loads," Ferroelectrics. (1991), Volume 120, pages 241-252; and Smits et al., "The Effectiveness of a Piezoelectric Bimorph Actuator to Perform Mechanical Work Under Various Constant Loading Conditions," Ferroelectrics. (1991), Volume 119, pages 89-105. A system 10 used to address an optical fiber relative to an array of fibers 60 is illustrated in Figure 5. A light source 64 can be used to generate optical signals for transmission into the array where controller 62 including a microprocessor is used to control deflection of the beam 10 in two dimensions such that an optical fiber mounted an beam 10 can be switched between two positions 58 and 59 to align the mounted fiber with any fiber in the array 60. Figure 6 shows the heterogeneous bimorph embodied as a sensing device for determining the position of objects. For instance, this embodiment can be used in a camera for automated focusing or can be used generally as a range finding device to sense the position of an object. The range finding device 65 shown in Figure 6, comprises an object 66, a CCD detector 68, a microprocessor system 62, electrostrictive heterogeneous bimorphs 10 having reflective surfaces 69 and controllers 70. In this particular embodiment, the image of the object 66 (i.e., a tree) is incident on the reflectors 69 of the electrostrictive bimorphs 10, which in turn, reflect two separate images onto the CCD detector 68. The microprocessor system 62 controls the movement of the electrostrictive bimorphs by supplying a specified biasing voltage through controller 70 to the electrostrictive material. The biasing voltage causes the electrostrictive material to bend which causes the images of object 66 to be detected at different positions on the CCD 68. Also, the microprocessor system can be programmed with an autocorrelation function which provides the necessary biasing voltage to deflect the electrostrictive bimorphs so that the respective images from both bimorphs converge towards each other until one image is produced on the CCD. As the deflection necessary to obtain full correlation between the reflected images is proportional to the distance between the imaged object 66 and a reference position or plane, the position of the object can be accurately determined. Figure 7 shows the heterogeneous bimorph 10 embodied in a system for deflecting a beam of light. In particular, this system is used for a laser printer or alternatively can be used as a bar code reader. Figure 7 shows the system for deflecting light embodied in a laser printer. The system 71 includes a light source 78 (preferably a laser) and controller 80, a heterogeneous bimorph 10 with a reflector 83 having a reflective surface for deflecting the light from the source 78, a charged surface 72 for receiving the light reflected from the bimorph, a mechanical driver 74 for moving the charged surface, and a microprocessor 62 for controlling the above elements. In this particular embodiment, the light source 78 irradiates the bimorph with a beam of light, the incident light is reflected onto the charged surface 72 to turn respective pixels. The movement of the heterogeneous bimorph causes the light to be deflected across the charged surface 72. Thus, the deflecting heterogeneous bimorph 10 acts as a pixel writer. Still another embodiment utilizing the heterogeneous bimorph 10 is illustrated in Figure 8. More specifically, the heterogeneous bimorph 10 is used as a accelerometer 84 for measuring vibration. The accelerometer 84 includes a proof mass 86 for providing a reference weight, a frame 88 for supporting the mass 86 and the electrostrictive material 10. A first electrical signal is applied to the bimorph which causes it to deflect towards an object to be measured. A detector connected to the heterogeneous bimorph detects the amount of vibration of the mass 86 that is suspended from the frame 88 on a stationary support. Figure 9 shows a circuit for driving the electrostrictive heterogeneous bimorph 10 to the necessary biasing voltage to actuate or sense movement of panel or mass 99. In particular, the circuit 89 includes diodes 90, 92 connected in parallel to the drain 95 of a field effect transistor 98 and diodes 94,96 connected in parallel to the source 97 of the field effect transistor. In this particular configuration, the diodes 90,92,94 and 96 ensure that the transistor is quickly biased to the necessary voltage. Thus, this circuit can quickly drive the bimorph to a bias voltage in the range of 0 to 8 volts. While the invention has been particularly shown and described in conjunction with a preferred embodiment thereof, it will be understood that many alternatives, modifications, and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims,

Claims: CLAIMS 1. A method of using an electrostrictive device, comprising: providing an electrostrictive material secured to a substrate; providing electrical contacts at different regions of the electrostrictive material to provide a device such that an electric field can be applied across the material; and biasing the electrostrictive material to a voltage to initiate deflection thereof, the biased electrostrictive material having a deflection that is quadratically dependent upon the biasing voltage. 2. The method of Claim 1, wherein the electrostrictive material is a chemical compound consisting of elements selected from Groups II and IV of the periodic table. 3. The method of Claim 2 wherein the electrostrictive layer is ZnO. 4. The method of Claim l wherein the substrate is a semiconductor material. 5. The method of Claim 1 wherein the voltage is biased in the range of 0 to 8 volts. 6. The method of Claim 1 wherein the voltage is biased with an alternating electrical signal in the range of 1-8 volts. 7. The method of Claim 1 wherein the substrate and the electrostrictive material have a thickness ratio approximating unity. 8. The method of Claim 1, wherein the substrate and the electrostrictive materials have a thickness ratio that is optimized for energy transfer. 9. The method of Claim 7 wherein the substrate layer has a thickness ranging from about 1 μ to about 100 μ. 10. The method of Claim 1 wherein the electrostrictive material has a length of about 1-5 mm long. 11. A method for using an electrostrictive device for actuating an object comprising: providing an electrostrictive element having electrical contacts at different regions of the electrostrictive element such that an electric field can be applied across the element; positioning the element adjacent to an object to be actuated; and applying an electric field to the electrostrictive element, the electric field having a voltage material between the contact, the voltage having a magnitude such that the element deflects in one direction regardless of the polarity of the electric field to move the object. 12. The method of Claim 11 wherein the electrostrictive material comprises a chemical compound consisting of elements selected from Groups II and IV of the periodic table. 13. The method of Claim 12 wherein the electrostrictive material comprises ZnO. 14. The method of Claim 11 wherein the element is secured to a silicon substrate having a layer of silicon nitride thereon. 15. The method of Claim 11 wherein the voltage is in the range of 0 to 8 volts. 16. The method of Claim 12 wherein the voltage is AC biased in the range of 0 to 8 volts. 17. The method of Claim 11 wherein the electrostrictive element comprises a bimorph having two materials which have a thickness ratio approximating unity. 18. The method of Claim 17 wherein the thickness ratio is optimized for energy transfer. 19. The method of Claim 14 wherein the silicon substrate has a thickness ranging from about 1 μ to about 100 20. The method of Claim 11 further comprising deflecting the electrostrictive element towards the object. 21. A method of using an electrostrictive element for sensing an object or medium comprising: providing an electrostrictive element; providing electrical contacts at different regions of the electrostrictive element to provide a device such that an electric field can be applied across the element; positioning the electrostrictive element adjacent to the object or medium to be sensed; and biasing the electrostrictive element to a voltage to initiate deflection thereof, the biased electrostrictive element having deflection that is independent of the field polarity. 22. The method of Claim 21 wherein the electrostrictive bimorph is a chemical compound consisting of elements selected from Groups II and VI of the periodic table. 23. A method of Claim 22 wherein the electrostrictive bimorph comprises ZnO. 24. The method of Claim 21 wherein the silicon substrate layer comprises Si 3 N 4 . 25. The method of Claim 21 further comprising deflecting the electrostrictive bimorph towards the object. 26. The method of Claim 21 further comprising vibrating the electrostrictive bimorph to enhance contact with the object. 27. The method of Claim 26 further comprising generating an electrical signal representative of a position of the object. 28. The method of Claim 27 further comprising processing the electrical signal to determine the position of the object. 29. An electrostrictive sensor comprising: a first region of electrostrictive material positioned between a first pair of electrodes on a deflectable member; a second region of electrostrictive or piezoelectric material positioned between a second pair of electrodes on the deflectable member; and an electrical circuit connected to the first pair of electrodes such that a first electrical signal can be applied across the first region of material to cause a deflection of the member, the circuit also being connected to the second pair of electrodes such that an alternating electrical signal can induce a vibration of the deflectable member. 30. The sensor of Claim 29 further comprising a control circuit wherein the first electrical signal is modified to actuate an object or medium in response to a sensor signal generated by the electrical circuit in response to contact between the deflectable member and the object or medium. 31. The sensor of Claim 29 wherein the electrostrictive material comprises ZnO. 32. The sensor of Claim 29 wherein the deflectable member is formed on or over a semiconductor material. 33. A system for deflecting a beam of light emitted from an energy source, comprising: an electrostrictive material for deflecting the beam of light emitted from the energy source,, the electrostrictive material including a first region of electrostrictive material positioned between a first pair of electrodes on a deflectable member, a second region of electrostrictive or piezoelectric material positioned between a second pair of electrodes on the deflectable member, a reflective surface positioned over the first and second regions of electrostrictive material, and an electrical circuit connected to the first pair of electrodes such that a first electrical signal can be applied across the first region of material to cause a deflection of the member, the circuit also being connected to the second pair of electrodes such that an alternating electrical signal can induce a vibration of the deflectable member; a charged surface for receiving the beam of light deflected from the electrostrictive material; and a microprocessor for controlling the energy source, the electrostrictive material, and the charged surface. 34. A system according to Claim 33, wherein the electrostrictive material comprises ZnO. 35. A system according to Claim 33, wherein the deflectable member is formed on or over a semiconductor material. 36. A method for deflecting a beam of light emitted from an energy source, comprising: positioning an electrostrictive material having a reflective surface in between the beam of light; biasing the electrostrictive element to a predetermined voltage to initiate deflection; and deflecting the beam of light onto a charged surface. 37. A device for sensing the position of an object, comprising: a first electrostrictive material and a second electrostrictive material spaced apart at a predetermined distance for receiving a reflected image of the object, the first and second electrostrictive materials each having a reflective surface for reflecting the reflected image therefrom; an image detector receiving the reflected images from both first and second electrostrictive material, the detector having a first and a second reference image formed thereon; a biasing source coupled to the first electrostrictive material and the second electrostrictive material for supplying bias voltage thereto, the bias voltage generating deflection in the first and second electrostrictive materials and moving the first and second reference images on the image detector; and an image correlator coupled to the image detector for generating one image from the first and second reference images based on an autocorrelation function. 38. A method for sensing the position of an object, comprising the steps of: positioning a first and second electrostrictive material each having a reflective surface separated apart from each other a predetermined distance for receiving a reflected image of the object; biasing the first and second electrostrictive materials to a predetermined voltage for initiating movement thereof; detecting the images reflected from both first and second electrostrictive materials wherein a first and second reference image are generated; and correlating the first and second reference image into one distinct image. 39. A device for addressing a plurality of optical fibers, comprising: a light source for emitting a beam of light to each of the plurality of optical fibers; an electrostrictive actuator coupled to the light source to address each of the plurality of optical fibers; and a biasing source coupled to the electrostrictive actuator for supplying a bias voltage thereto. 40. A method for addressing a plurality of optical fibers, comprising the step of: providing a light source for emitting a beam of light; coupling an electrostrictive actuator to the light source; and addressing each of the plurality of optical fibers with a beam of light from the light source, the light.source moving in a predetermined manner. 41. An accelerometer for measuring vibration of an object, comprising: a proof mass for providing a reference to the object; a frame for supporting the object and the proof mass, the proof mass and object being separated at a predetermined distance; and an electrostrictive material positioned between the proof mass and the object for initiating vibration of the proof mass and the object. 42. A method for measuring vibration of an object, comprising the steps of: positioning a proof mass relative to the object; connecting the object and the proof mass to a frame; providing an electrostrictive material between the proof mass and the object for initiating vibration thereto; and measuring the vibration of the object.

Inventors: SMITS JOHANNES G, SMITS, JOHANNES, G.
Applicants: UNIV BOSTON, TRUSTEES OF BOSTON UNIVERSITY
Application year: 1993
Main classification: H01L41
IPC codes: H01L29, H01L41