Abstract: A gradient of gravity is defined by a change in the optical path length required to maintain equality in optical path lengths of two beam arms which direct light beams to impinge upon and reflect from two freefalling test masses.

Abstract: A gravity value is measured using two light beams which each reflect from both a freefall test mass and a stationary reference test mass which is inertially supported by a long period isolation device. The optical path lengths of the light beams change equally and oppositely in response to gravity and equally in response to disturbances, resulting in cancellation of the undesirable effects of the disturbances by common mode rejection and in a desirable increase in the number of gravity induced measurement fringes, when the two light beams are combined interferometrically.

Abstract: A double pendulum gravimeter accurately measures gravity by transferring aligned mode energy between suspension points of the pendulums to establish equal arcs of oscillation of the pendulums and by sensing oscillation characteristics to establish an accurate gravity value including a correction factor which depends on the arc of oscillation, while absorbing adverse mode energy.

Abstract: Incident differently-polarized light beams are separately directed and combined by one or two corner cube structures, each having one or two walls formed as a beam splitter. One incident light beam is passed, while the other incident light beam is reflected.

Abstract: A double pendulum gravimeter accurately measures gravity by transferring aligned mode energy between suspension points of the pendulums to establish equal arcs of oscillation of the pendulums and by sensing oscillation characteristics to establish an accurate gravity value including a correction factor which depends on the arc of oscillation, while absorbing adverse mode energy.

Abstract: A gravity gradient is measured interferometrically from two polarized light beams having mutually different polarization planes which reflect from opposite surfaces of two freefalling test masses. The two polarized light beams project along matched coincident beam paths and divert from the coincident paths to interact with the freefalling test masses. An enhanced level of common mode rejection of adverse influences arises from traversing the coincident beam paths.

Abstract: A gradient of gravity is defined by a change in the optical path length required to maintain equality in optical path lengths of two beam arms which direct light beams to impinge upon and reflect from two freefalling test masses.

Abstract: A gravity gradient is measured interferometrically from two light beams which each reflect from both of two freefalling test masses. The light beams project in beam arms which remain equal in length as the two test masses freefall except for different effects of gravity on each test mass and any initial relative velocity difference imparted to the test masses. The optical path length of the beam arms also change equally and oppositely during freefall, to amplify the interferometric effect by four times. A high level of common mode rejection eliminates many spurious influences.

Abstract: A test mass used for light beam interferometric gravity characteristic measurement has a center of mass located equidistant and colinear with optical center points of two oppositely reflecting retroreflectors. Rotation of the test mass about its center of mass during freefall changes the path length of the oppositely reflected light beams by equal amounts, thereby achieving common mode cancellation of the effects of test mass rotation when the two reflected light beams are interferometrically combined.

Abstract: A gravity value is measured using two light beams which each reflect from both a freefall test mass and a stationary reference test mass which is inertially supported by a long period isolation device. The optical path lengths of the light beams change equally and oppositely in response to gravity and equally in response to disturbances, resulting in cancellation of the undesirable effects of the disturbances by common mode rejection and in a desirable increase in the number of gravity induced measurement fringes, when the two light beams are combined interferometrically.

Abstract: A gravity gradient is measured interferometrically from two polarized light beams having mutually different polarization planes which reflect from opposite surfaces of two freefalling test masses. The two polarized light beams project along matched coincident beam paths and divert from the coincident paths to interact with the freefalling test masses. An enhanced level of common mode rejection of adverse influences arises from traversing the coincident beam paths.

Abstract: Incident differently-polarized light beams are separately directed and combined by one or two corner cube structures, each having one or two walls formed as a beam splitter. One incident light beam is passed, while the other incident light beam is reflected.

Abstract: A gravity gradient is measured interferometrically from two light beams which each reflect from both of two freefalling test masses. The light beams project in beam arms which remain equal in length as the two test masses freefall except for different effects of gravity on each test mass and any initial relative velocity difference imparted to the test masses. The optical path length of the beam arms also change equally and oppositely during freefall, to amplify the interferometric effect by four times. A high level of common mode rejection eliminates many spurious influences.

Abstract: A test mass used for light beam interferometric gravity characteristic measurement has a center of mass located equidistant and colinear with optical center points of two oppositely reflecting retroreflectors. Rotation of the test mass about its center of mass during freefall changes the path length of the oppositely reflected light beams by equal amounts, thereby achieving common mode cancellation of the effects of test mass rotation when the two reflected light beams are interferometrically combined.

Abstract: A differential gradient of gravity is directly measured from the interferometric combination of two light beams which reflect from pairs of three freefalling test masses. Optical path lengths of two beam arms change relative to one another because of differential gradient of gravity effects the test masses differently simultaneous freefall. The relatively large background of gravity and the gradient of gravity are eliminated from the measurement while simultaneously achieving a high level of common mode rejection of other spurious influences.

Abstract: A gravity survey is conducted by obtaining relative gravity measurements from a plurality of survey points using a relative gravimeter, obtaining absolute gravity measurements from a subset of a lesser plurality of the survey points designated as combination survey points, determining a correction factor related to any difference between the relative and absolute gravity measurements at each of the combination survey points, and correcting the relative gravity measurements made at the survey points which are not combination survey points using the correction factor. The absolute and corrected relative gravity measurements at the survey points constitute the gravity survey.

Abstract: A gravity survey is conducted by obtaining relative gravity measurements from a plurality of survey points using a relative gravimeter, obtaining absolute gravity measurements from a subset of a lesser plurality of the survey points designated as combination survey points, determining a correction factor related to any difference between the relative and absolute gravity measurements at each of the combination survey points, and correcting the relative gravity measurements made at the survey points which are not combination survey points using the correction factor. The absolute and corrected relative gravity measurements at the survey points constitute the gravity survey.

Abstract: The present invention provides devices and methods for reducing or eliminating sources of systematic errors in the measurement of absolute gravity or gravity field gradients; specifically, an improved test mass for an interferometer is disclosed that reduces the influence of nearby electromagnetic fields on a freefalling test mass.

Abstract: Gravity information for a gravity survey is obtained by using an array of relative gravimeters whose relative gravity measurement signals have been calibrated by using an absolute gravimeter to approximate absolute gravity measurements. The absolute gravimeter is moved periodically to the location of each relative gravimeter to measure absolute gravity. The absolute and relative gravity measurements for each relative gravimeter form an error signal which is used to calibrate each relative gravimeter.

Abstract: An adjustable orthodontic bracket assembly includes a plurality of brackets. Each bracket is attachable to a front face of a tooth such that the bracket is positionable in series relation to one or more other of the brackets. Each bracket is continuously adjustable in at least three planes and, preferably, in six planes of motion without a need to replace any parts thereof. The adjustment of each bracket in one of the planes of motion can be accomplished without affecting the adjustment of the bracket in any of the other planes of motion. Specifically, each bracket is capable of adjustment in at least three and, preferably, all of vertical, lateral and mesio/distal translational planes of motion and tip, torque and circular rotational planes of motion. Also, the assembly includes an arch wire extending between and retained on the brackets.