An optical inclination sensor is provided having at least one reflective surface and at least two separate optical fibers having ends spaced from a reflective surface. As the reflective surface tilts with respect to a pre-determined reference position the gap lengths between the fiber ends and the reflective surface change and the differences in these gap lengths is used to calculate an angle of inclination with respect to a reference position. The optical inclination sensor can include at least one mass attached to a housing and moveable with respect to the housing as the mass and housing are rotated about one or more axes. Optical strain sensors are disposed a various locations between the mass and housing so that as the mass moves with respect to the housing, each one of the optical strain sensors are placed in compression or tension. The housing can be a generally u-shaped housing having two arms and a base section with the mass disposed within the housing. Alternatively, the housing includes a first beam, and the mass is a second beam arranged generally orthogonal to the first beam and pivotally attached thereto. The optical strain sensors are disposed between the first beam and the second beam. The optical strain sensors are placed in tension or compression as the second beam pivots with respect to the first beam.
The present invention provides the stress detection method for force sensor device with multiple axis sensor device and force sensor device employing this method, whose installation angle is arbitrary. The stress detection method includes, first and second force sensors whose detection axes are orthogonal to each other. When the detection axis of first force sensor forms angle .theta. with direction of detected stress Ax, and the stress component of direction perpendicular to direction of the detected stress Ax is Az, output Apx of the axis direction of first force sensor is found as Apx=.alpha..sub.x (Ax.times.cos .theta.+Az.times.sin .theta.), and output Apz of the axis direction of the second force sensor is found as Apz=.alpha..sub.z (Ax.times.sin .theta.+Az.times.cos .theta.), and, when .alpha..sub.x and .alpha..sub.z are detection sensitivity coefficients of first and second force sensors respectively, the detection sensitivity coefficient .alpha..sub.z of second force sensor is set as .alpha..sub.z=.alpha..sub.x tan .theta., and the detected stress Ax is found as Ax=(Apx-Apz)/.alpha..sub.x(cos .theta.-tan .theta..times.sin .theta.).
