A new imaging technique called Wavefront Coding. allows real-time imaging of three-dimensional structures over a very large depth. Wavefront Coding. systems combine aspheric optics and signal processing to achieve depth of fields ten or more times greater than that possible with traditional imaging systems. Understanding the relationships between traditional and modern imaging system design through Wavefront Coding. is very challenging. In high performance imaging systems nearly all aspects of the system that could reduce image quality are carefully controlled. Modifying the optics and using signal processing can increase the amount of image information that can be recorded by microscopes. For a number of applications this increase in information can allow a single image to be used where a number of images taken at different object planes had been used before. Having very large depth of field and real-time imaging capability means that very deep structures such as surface micromachined MEMS can be clearly imaged with one image, greatly simplifying defect and failure analysis.