Stress sensor

Details Stress sensor Stress sensor

1986-08-07

1988-12-06

Rosenberger, Richard A.

Optics: measuring and testing

Material strain analysis

With polarized light

356367, 73800, 73850, G01B 1118

Patent

active

047892366

ABSTRACT:
Mechanical stress applied to a crystal (10) by a procedure for forming a bond (13) between an electrical connector (12) and a metallized surface (11) of the crystal (10) is measured to obtain a quantitative indication of the quality of the bond (13). A beam of optical radiation generated by an illuminator (21) is divided by a first beamsplitter (22) into a first component and a second component. The power of the first component is measured by a first detector (23). The second component is circularly polarized by a circular polarizer (24), collimated by an imaging lens (25), and directed as an incident beam along an optical path through the crystal (10) to the metallized surface (11) in the vicinity of the bond (13). The metallized surface (11) reflects the incident beam back along the same optical path as a return beam. Mechanical stress applied to the crystal (10) by the bonding procedure produces birefringence in the crystal (10), which changes the polarization of the incident and return beams from circular to elliptical in passing through the crystal (10). The circular polarizer (24) functions as an analyzer with respect to the return beam, and transmits only a linearly polarized component of the return beam. A portion of the linearly polarized component of the return beam is transmitted through the first beamsplitter (22) to a second beamsplitter (26), which reflects a further portion thereof to a second detector (29), and which transmits another portion thereof to a video camera tube (27). The second detector (29) measures the power of the linearly polarized component of the return beam. A ratiometer (30) compares the power of the linearly polarized component of the return beam with the power of the first component of the beam generated by the illuminator 21, and produces a numerical value that provides a quantitative measure of the strength of the bond (13).

REFERENCES:
patent: 3034344 (1962-05-01), Zandman et al.
patent: 3101609 (1963-08-01), Redner
patent: 3902805 (1975-09-01), Redner
patent: 4570173 (1986-02-01), Anthony et al.
patent: 4585348 (1986-04-01), Chastang
patent: 4629323 (1986-12-01), Matsumoto

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