Abstract: An ellipsometer apparatus (10) has a measurement compensation feature. The ellipsometer (10) provides for relative lateral movement between a light source assembly (12) and a specimen holder (14) via a positioner assembly (16) to provide for more accurate measurements of a thin film layer (55) on a specimen member (50).

Abstract: A seal assembly for a rotating shaft includes an annular seal washer of flexible, fluid-impermeable material and capable of undergoing creep, i.e., slow movement or change in size while under stress. A helical garter spring encircles the washer and stresses it by biasing it radially inwardly. An annular housing of two interlocking members cooperate to enclose the spring and an O-ring which cooperates with the housing to resiliently clamp the washer to inhibit movement axially and circumferentially of the shaft, while accommodating radial creep under the urging of the spring. Inwardly struck tabs in the housing may engage the spring to inhibit circumferential movement thereof. In one embodiment, one of the housing members has circumferentially spaced-apart fingers adapted to be interleaved with the tabs of a fixture to facilitate assembly of the apparatus.