Marc D. Mermelstein

Spectral and radiometric calibration of midwave and longwave infrared cameras

Accurate spectral and radiometric calibrations of IR cameras are needed to interpret infrared imagery properly, to monitor camera performance over time, and to evaluate new imaging radiometers. In this paper, the physical basis for calibrating IR cameras is derived from first principles, and a laboratory setup used to perform both radiometric and spectral calibrations is described. The calibration procedures used with this setup are then demonstrated on a midwave IR focal plane array camera, a midwave IR scanned camera, and a longwave IR scanned camera. The system spectral response and radiometric response of each camera is given and analyzed. An error analysis of approximating a cameras spectral response by an equivalent top-hat responsivity is also given.

Rayleigh scattering optical frequency correlation in a single-mode optical fiber

The bichromatic optical frequency correlation function for Rayleigh backscattering from a pulse of laser light propagating along a single-mode optical fiber has been calculated and measured. It is shown that the optical correlation frequency, Dnu(c) , is equal to the reciprocal of pulse width T(w) . These results are important for the development of wavelength diversity techniques for the reduction of coherent Rayleigh noise in distributed Rayleigh backscattering single-mode optical fiber sensors.

Fiber-optic atmospheric turbulence sensor.

A novel dual-air-gap fiber-optic Mach - Zehnder interferometer is proposed for the direct measurement of the atmospheric optical turbulence structure constant C(n)(2). The shot-noise-limited minimum detectable structure constant is estimated to be 4.5 x 10(-20) m(-2/3), which is more than 2 orders of magnitude below a typical value of 10(-17) m(-2/3) for weak turbulence. This sensor is suitable for the measurement of atmospheric turbulence over land and ocean surfaces.

Single-mode optical fiber goniometer

A two-element single-mode optical fiber goniometer that uses graded-index microlens receivers is presented that measures the angular orientation of a remote laser. The goniometer exhibits a sensitivity of 1.0 V/mrad and a calculated shot-noise-limited angular resolution of 1.0 nrad/ radicalHz.

1 x 2 fiber-optic heterodyne array for laser Doppler velocimetry and angular orientation measurements.

A 1 x 2 single-mode fiber-optic heterodyne array is presented that simultaneously measures the radial and angular Doppler velocities of a target. This heterodyne array also provides an amplitude-dependent error signal suitable for angular tracking.

Infrared solar glint clutter on the ocean surface

A closed-form expression is developed for the infrared solar glint clutter radiance generated by the nearhorizon ocean surface. The clutter radiance is calculated as a function of water temperature, wind speed, wind direction, and solar position and agrees well with midwave infrared imagery measurements.

MIDWAVE AND LONG-WAVE INFRARED RADIANCE AND CLUTTER AT THE OCEAN-SKY HORIZON

A statistical analysis is presented for the mean and the clutter radiance emitted by the ocean surface near the horizon and in the absence of direct solar illumination. The calculated midwave and long-wave radiances are given as functions of the environmental and optical parameters and agree with experimentally measured radiance profiles to within 20%. A simple expression for the calculated radiance as a function of wind speed and look direction is obtained by linearizing the radiance as a function of the wave slope.