Present automated systems for counting and measunng marine plankton include flow cytometers and in situ plankton video recorders. Neither of these approaches are optimal for the microplankton cells which range in size from 20 to 200 pm and can be fewer than 104 1". We describe here an instrument designed for rapid counting, imaging and measuring of individual cells and particles in the microplankton size range from cultures and natural populations. It uses a unlque optical element to extend the depth of focus of the imaging lens, allowing a sample stream flow rate of 1 rnl min-'. The instrument stores a digital image of each particle along with real time fluorescence and size measurements. An interactive cytogram links a dot-plot of the size and fluorescence data to the stored cell images, allowing rapid characterization of populations. We have tested the system on live phytoplankton cultures and bead standards, proving the system counting and slzlng accuracy and precision. The system provides Images and size distributions for cultures or natural manne samples. It has been used successfully at sea to continuously monitor particles while underway. It may prove useful in s t u d~e s of plankton community structure, ocean optics and monitoring for harmful algal species.

When a confocal fluorescence microscope with a high-numerical-aperture oil-immersion objective is focused deep into an aqueous medium, aberrations result that degrade image quality. We have designed and fabricated a simple two-level binary phase mask that partially corrects these aberrations, improving axial resolution. We present the design and some confirming results.

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When a confocal fluorescence microscope with a high numerical aperture oil immersion objective is focused deep into an aqueous medium, aberrations result which weaken and blur the observed image. We have designed, fabricated and tested a two-level binary phase mask which partially corrects these aberrations, improving image brightness and resolution. A four-level mask was also designed, fabricated and tested with further brightness and resolution improvement. The mask designs and simulated and measured results are presented in this paper.

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009