Algorithms for sensor chip alignment to blind datums

The sensor element of an imaging system should be mounted into its housing in such a way that the scene can be prop­ erly focused onto the sensor element’s focal plane over the active area. Operational imaging requirements are forcing increasingly smaller tolerances on sensor alignment, and manufacturing systems must improve alignment capability to keep pace. Imaging system designs include reference datums that provide the basis for manu­ facturing alignment of optical components in each subassembly. De­ sign constraints for alignment of the sensor element into the camera housing typically include x ,y , z, clocking, and parallelism specifica­ tions. Measurement of z and parallelism positioning is often prob­ lematic, since the relevant reference datum features are often be­ neath the mounting platform and are obscured to the measurement system. General algorithms for determining sensor chip alignment when datum features are inaccessible to the measurement system are described. Precharacterization measurements of datum sur­ faces are used to determine datum locations during alignment mea­ surement. The algorithms are useful for active manufacturing align­ ment as well as postmounting alignment measurement. The algorithms are successfully implemented for ultraprecision, active manufacturing alignment, and postalignment measurement of IR im­ aging systems. © 2006 SPIE and IS&T. �DOI: 10.1117/1.2234326�