Title of Invention	AN OPTOELECTRONIC APPARATUS FOR STATIC AND DYNAMIC MEASUREMENTS
Abstract	The invention relates to an optoelectronic apparatus for satic and dynamic measurements. It consists of a laser source on a rigid base with oprical elements such as mirrors,beam splitters,beam expanders,image capturing means and a computer for measuring displacement and slope by interferometry

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The invention relates to an optoelectronic apparatus for static and dynamic measurements. The apparatus according to the invention may be used for non-destructive measurements under both static and dynamic loadings. It also measures slope, which is mainly used for static loading. For displacement measurements light from a laser beam is split into a reference beam and an object beam. The reference beam is attenuated and passed through plurarility of mirrors to have path length equal to the path length of the object beam when the object is under no load. The object beam is expanded and made to illuminate the object. The reflected light from the object is passed through a prism and lens assembly, reflected light from the object beam and the reference beam a-e recombined on a wedge beam splitter located before an image capturing means connected to a computer to obtain displacement measurements under loaded conditions by interferometry. For slope measurement the reference beam is blocked. The object beam is expanded and made to illuminate the object. The reflected light from the object is passed through an assembly of a prism and mutually perpendicular mirrors and recombined after passing through the lens assembly on the wedge beam splitter located before the image capturing means connected to the computer for measuring slope by interferametry. The image capturing means preferably comprises a camera and an image-grabbing card connected to a computer. The image capturing means may be a web camera connected to a computer. The image-grabbing card may also have real time capabilities. An actuator connected to the computer is attached to the object during dynamic measurements. The invention provides an optoelectronic apparatus for static and dynamic measurements comprising a laser mounted on a rigid base, a reflecting mirror to reflect the laser beam from the laser to a beam splitter for splitting the laser beam into a reference beam and an object beam a beam exp^der to expand the object beam and illuminate an object on which measurement is to be carried out, a prism for directing the reflected beam from the object to a wedge beam splitter through a lens assembly, a neutral density filter and plurality of mirrors located in the path of the reference beam from the beam splitter to attenuate and match the path length of the reference beam with the path length of the object beam and direct it to the wedge beam splitter a tiltable mirror located at a distance from the side of the prism opposite to the side receiving the reflected light from the object with the plane of the mirror perpendicular to the axis of the reflected beam from the object, a fixed mirror with the plane of the mirror perpendicular to that of the tillable mirror and located at a distance from the side adjacent to the side of the prism receiving the reflected light from the object, a removable screen located between the beam spliter and the neutral density filter and another removable screen located between the prism and the titlable mirror, an image capturing means located with its axis parallel to the axis of the reflected beam from the object directed to the wedge beam splitter a computer connected to the out put of said image capturing means for interferometric measurements of displacement and slope and an actuator connected to the computer for vibrating the object during dynamic measurements. The optoelectronic apparatus for static and dynamic measurements will be described with reference to the only figure shown in the accompanying drawing. Laser beam from a laser (LA) is reflected on mirror (Mi) and split into two beams reference beam (BR) and object beam (BO), by a beam splitter (BS1). A removable screen (S1) provided for blocking the reference beam is kept out of the path of reference beam (BR) during the displacement measurement. The reference beam (BR) passes through a neutral density filter (NDF) for attenuation and passed through a set of mirrors (M2 to Mg) for matching the path length with the object beam (BO). The reference beam (BR) with corrected path length is passed through a beam expander (BEX2) to a wedge beam splitter (BS2) kept before an image capaturing means (C). The object beam (BO) from the beam splitter (BS1) is passed through a beam expander (BEX1) to illuminate the object (0) and the reflected beam from the object (0) passes through a prism (P) directing the reflected beam from the object to a lens assembly (L) provided for focusing the object (0). The reflected beam from the object is directed to the image capturing means through the beam splitter (BSj) resulting in interference with the reference beam (BR). During the displacement measurement, screen (S2) is located between the prism (P) and mirror (M7) to block mirror (M7). The image capturing means ( C) and the associated computer (PC) provides the measure of displacement. For slope measurement the laser beam from the laser (LA) is reflected on mirror (M1) and is passed through the beam splitter (BS1) and beam expander (BEX1) to illuminate the object (O). During this measurement, screen (S1) is kept in the path of the reference beam (BR) from the beam splitter (BS1) to block the reference beam and screen (S2) between the prism (P) and mirror (M7) is removed from the plath of the reflected beam from the object (0). The reflected beam from the object is sheared by the assembly of the prism (P) and the two mutually perpendicular mirrors (M7 and Mg) The mirror (M7) is tiltable and tilting this mirror will produce sheared images which is captured by the image capturing means (C) for measuring slope by interferometry with the aid of the computer (PC). The image capturing means (C ) is preferably a charge coupled device (CD) camera associated with an image grabbing card (IGC). The image grabing card may be with real time capabilities or a multimedia IGC with non realtime capabilities. The image capturing means (C) may also be a web camera. An actuator (A) connected to the computer (PC) provides excitation to the object during dynamic measurements. the apparatus according to the invention can be used for highly sensitive, whole field, real time, contactless measurement of displacement and slope. Some of the applications of the optoelectronic apparatus according to the invention are given below. 1. Displacement and slope measurement for static loads such as mechanical load, thermal load and pressure load. 2. Material property measurements such as Young's modulus, Poisson s ratio and coefficient of thermal expansion. 3. Non-destructive evaluation of aerospace and industrial compenents for a detection of debonds, delamination, minute cracks etc. 4. Modal analysis of vibrating objects by determining natural frequencies and mode shapes. We claim: 1. An optoelectronic apparatus for static and dynamic measurements comprising a laser (LA) mounted on a rigid base, a reflecting mirror (M1) to reflect the laser beam from the laser to a beam splitter (BS1) for splitting the laser beam into a reference beam (BR) and an object beam (BO), a beam expander (BEXi) to expand the object beam and Illuminate an object (0) on which measurement is to be carried out, a prism (P) for directing the reflected beam from the object (0) to a wedge beam splitter (BSA) through a lens assembly (L), a neutral density filter (NDF) and plurality of mirrors (M2 to M6) located in the path of the reference beam (BR) from the beam splitter (BSi) to attenuate and match the path length of the reference beam (BR) with the path length of the object beam (BO) and direct it to the wedge beam splitter (BS2) a tiltable mirror (M7) located at a distance from side of the prism (P) opposite to the side receiving the reflected light from the object with the plane of the mirror perpendicular to the axis of the reflected beam from the object, a fixed mirror (Mg) with the plane of the mirror perpendicular to that of the tiltable mirror (My) and located at a distance from the side adjacent to the side of the prism receiving the reflected light from the object (0), a removable screen (Si) located between the beam splitter (BSi) and the neutral density filter (NDF) and another removable screen (S2) located behveen the prism (P) and the tiltable mirror (My), an image capturing means (C) located with its axis parallel to the axis of the reflected beam from the object directed to the wedge beam splitter (BS2) a computer (PC) connected to the out put of said image capturing means (C) for interferometric measurements of displacement and slope and an actuator (A) connected to the computer (PC) for vibrating the object (O) during dynamic measurements. 2. The apparatus as claimed in claim 1 wherein the image capturing means (C) is a camera associated with an image-grabbing card. 3. The apparatus as claim ed in claim 2 wherein the camera is a charge coupled device camera and the image-grabbing card is an image grabbing card with real time capabilities or a multimedia image-grabbing card with non real time capabilities. 4. The apparatus as claimed in claim 1 where in the image capturing means (C) is a web camera. 5. The apparatus as claimed in claim 1 wherein the actuator (A) is a speaker, a shaker or a piezo-electric element. Dated this 24 day of April 2001

Documents:

337-mas-2001-abstract.pdf

337-mas-2001-claims duplicate.pdf

337-mas-2001-claims original.pdf

337-mas-2001-correspondance others.pdf

337-mas-2001-correspondance po.pdf

337-mas-2001-description complete duplicate.pdf

337-mas-2001-description complete original.pdf

337-mas-2001-drawings.pdf

337-mas-2001-form 1.pdf

337-mas-2001-form 19.pdf

337-mas-2001-form 26.pdf

337-mas-2001-form 3.pdf