Patent ID: 6457359
Filing Date: 2002-10-01
Classification: G01N

Abstract:
An apparatus for measuring stress in a membrane of a specimen, the apparatus comprising:a vibration-applying device situated a distance from the membrane and configured to apply a vibration stimulus comprising sound waves to the membrane, the vibration stimulus causing the membrane to experience a vibrational stress; and a detector situated and configured to measure the stress, the detector comprising a light source situated and configured to irradiate a region of the membrane with light such that at least a portion of the light is reflected from the membrane, a light receiver situated and configured to receive the light reflected from the irradiated region of the membrane and produce a corresponding output signal, and a computer connected to the light receiver and configured to determine, from the output signal, a vibration spectrum for the irradiated region and to determine, from the vibration spectrum, a measure of a stress characteristic of the region of the membrane.