Abstract: Apparatus for optical assessment of a sample includes a radiation source, adapted to generate a beam of coherent radiation, and traveling lens optics, adapted to focus the beam so as to generate first and second spots on a surface of the sample and to scan the spots together over the surface. The distance between the first and second spots is responsive to a pitch of a repetitive pattern of the sample. Collection optics are positioned to collect the radiation scattered from the first and second spots and to focus the collected radiation so as to generate an interference pattern. A detector detects a change in the interference pattern.

Abstract: A system for inspecting a specimen, such as a semiconductor wafer that uses a laser light source for providing a beam of light. The beam is applied to a traveling lens acousto-optic device having an active region and responsive to an RF input signal to selectively generate plural traveling lenses in the active region. The traveling lens acousto-optic device is operative to receive the light beam and generate plural flying spot beams, at the respective focus of each of the generated traveling lenses. A light detector unit, having a plurality of detector sections, each detector section having a plurality of light detectors and at least one multi-stage storage device operative to receive in parallel an input from the plurality of light detectors, is used to generate useable scan data. Information stored in each of the storage devices is serially read out concurrently from the multiple stages.

Abstract: Method and apparatus to enable detection of a position of an article, and thereby enable maintenance of a desired position thereof. The apparatus includes an illumination unit, focusing optics and a focus detection unit, the focusing optics serving to direct incident light toward the article and directing light returned from an illuminated elongated region on the article toward the focus detection unit. The focus detection unit includes an optical system that collects the returned light passed through the focusing optics and creates at least two images in the form of at least two interference patterns, respectively, on the sensing surface of a detector. The first interference pattern is created by interference of light components of the collected light that propagated within a first periphery region of an optical axis of the focusing optics and light components of the collected light that propagated within a paraxial region of the optical axis.

Abstract: Scanning method and apparatus for maintaining a desired position of an article are presented. The apparatus comprises an illumination unit, a focusing optics and a focus detection unit. The illumination unit generates an incident light beam for illuminating an elongated region of the article and producing light returned from the illuminated region. The focusing optics focuses the incident beam onto a focal plane and collects at least a portion of the returned light. The focus detection unit comprises an imaging optics and a detector having a sensing surface responsive to light impinging thereon for generating data representative thereof. The imaging optics is capable of forming first and second images on the sensing surface. The first and second images are formed by first and second spatially separated substantially identical light components of the collected returned light, respectively, which propagate symmetrically relative to an optical axis of the focusing optics.