Patent ID: 7965390

Claim:
A system which automatically reduces change in alignment of angle and plane of incidence of a focused beam of electromagnetic radiation which is caused to impinge on a sample and which reflects therefrom, sequentially comprising: a source of beam of electromagnetic radiation; a focusing lens; a sample; and a detector; wherein said detector has dimensions less than is the spread of said focused beam at least one location distal to the location on said sample from which it is caused to reflect: such that in use said source of beam of electromagnetic radiation is caused to direct a beam of electromagnetic radiation through said focusing lens such that the resulting focused beam reflects from said sample in an expanding beam manner, and wherein said detector is positioned at a location to intercept less than the entire expanding reflected beam at the location of said detector; wherein the improvement is found in the positioning of the detector in said expanding beam which is reflected from said sample, such that the size of said detector is less that that of said expanding beam at the location whereat said detector is located; such that the effect of a change in the angle-of-incidence and/or plane-of-incidence of the incident beam onto said sample on detector output is reduced, as compared to the change that would occur if the entire reflected beam were intercepted by the detector.