The method presented in this work also addresses the common problem of crosstalk in aligning displacement interferometry systems. Traditionally, two different sensors (and setups) have been used to measure lateral (straightness) and angular (cosine) errors separately. Approaching the errors separately can lead to significant crosstalk that may adversely affect one or both measurements. For example, as an optical beam passes through a planar surface, the output beam is laterally shifted due to refraction as a function of plate thickness, refractive index, and the rotation angle. If the intention of passing the optical beam is to measure lateral errors, and angular errors are not simultaneously addressed, then a slight angular error can appear as a lateral error. Fitzsimons et al. address this by simultaneously measuring both angular and lateral errors. This is especially useful because their ideal alignment target is the centers of both quadrant detectors. For a fixed artifact, there is only one solution where that alignment is achieved, minimizing the chance for crosstalk between angular and lateral errors. Even errors due to wavefront distortion in their beamsplitter and folding mirrors are essentially unique to that particular artifact, meaning that if this artifact is used for multiple optical beams, then all beams would be aligned with the same artifact errors, making those errors effectively common mode between optical beams to within the accuracy of the artifact.
The authors have presented an alignment artifact that enables simultaneous calibration of lateral and angular alignment errors in beam pointing with a high fidelity, reducing their contribution to overall target positioning uncertainty, which is critical for many applications.
You must log in to add comments.