Our microscope system uses a special-purpose optical element (called a cubic phase plate or CPP) to uniformly "code" the information from all planes throughout the specimen volume onto a single CCD camera image. Specimen-independent digital processing is then used to "decode" this raw image. In effect, the coded raw image is blurred by a special type of aberration which produces an image that is nearly independent of focus. The system then uses a fast, non- iterative, digital filtering algorithm to remove this special blur so that a large volume of the specimen image appears sharply focused all at once. That is, an extended depth-of-focus (EDF) image is produced. Recent work predicts that this wavefront coding and decoding (digital filtering) technique will not reduce the lateral resolution of the microscope. The only trade-off is a modest reduction in signal-to- noise ratio as compared to conventional microscopes.

Diagram of EDF Optical/Digital System:




Cubic Phase Plate:


Conventional Lens vs Cubic Phase Plate (CPP) Ray Traces:




Ray traces of 3 spatially-separated points in an EDF system:




Focus Invariance - Point Spread and Modulation Transfer Functions: