An optical coherence microscope (OCM) has been designed and constructed to acquire 3-dimensional images of highly scattering biological tissue. Volume-rendering software is used to enhance 3-D visualization of the data sets. Lateral resolution of the OCM is 5 µm (FWHM), and the depth resolution is 10 µm (FWHM) in tissue. The design trade-offs for a 3-D OCM are discussed, and the fundamental photon noise limitation is measured and compared with theory. A rotating 3-D image of a frog embryo is presented to illustrate the capabilities of the instrument.

The lifetime of the atomic cesium 5(2)D(5/2) state was measured with time-correlated single-photon counting spectroscopy. Ground-state cesium atoms were excited with a diode laser by use of an electric quadrupole transition. Analysis of the exponential decay of the cascade photons from the 6(2)P(3/2) state yields a 5(2)D(5/2) lifetime of 1225(12) ns.

Fast phase modulation has been achieved in a Michelson interferometer by attaching a lightweight reference mirror to a piezoelectric stack and driving the stack at a resonance frequency of about 125 kHz. The electrical behavior of the piezo stack and the mechanical properties of the piezo-mirror arrangement are described. A displacement amplitude at resonance of about 350 nm was achieved using a standard function generator. Phase drift in the interferometer and piezo wobble were readily circumvented. This approach to phase modulation is less expensive by a factor of roughly 50 than one based on an electro-optic effect.

A simple setup for measuring the amount of potassium in foods is described. A 3-in. NaI detector is used to measure samples that are 3000 cm 3 in size. With moderate shielding, the potassium content can be measured down to a detection limit of a few parts per 10 000.

We have previously described an inexpensive method for modulating the interferometer of an en-face scanning, focus-tracking, three-dimensional optical coherence microscope (OCM). In this OCM design, a reference mirror is mounted on a piezoelectric stack driven at a resonance frequency of about 100 kHz. We perform a partial discrete Fourier transform of the digitally sampled output fringe signal. In the original design, we obtained the amplitude of the backscattered light by summing the powers in the fundamental ͑1 ͒ and first harmonic ͑2 ͒ of the modulation frequency. We used the particular piezoamplitude that eliminates the effects of interferometer phase drift. However, as the reference mirror was stepped to scan at different sample depths, variations in the back-coupled reference power added noise to the fringe signal at the fundamental piezodriving frequency. We report here a technique to eliminate the effects of this piezowobble by using instead the sum of the 2 and 3 powers as a measure of the backscattered light intensity. Images acquired before and after this improvement are presented to illustrate the enhancement to image quality deep within the sample.