An instrument for measuring the lifetime of luminescence (fluorescence or phosphorescence) includes a digital signal processor (DSP) as the primary means of control, generation of excitation signals, and analysis of response signals. In contrast, prior luminescencelifetime- measuring instruments have utilized primarily analog circuitry to perform these functions. Such instruments are typically used as optical chemical sensors.
Like the prior instruments, the present
instrument is based on the principle of
illuminating a specimen with sinusoidally
varying light to excite sinusoidally varying
luminescence and measuring either the
phase shift (ϕ) between the luminescence
oscillations and the excitation signal
at a specified frequency (f) or the frequency
that results in a specified fixed
phase shift (typically, 90°. The fluorescence
lifetime (τ) is then calculated using
τ = tan ϕ/(2πf). The primary limitation of
prior analog instruments was lack of
reconfigurability: it was necessary to
rewire components to change operating
modes for different specimens. In contrast,
the DSP hardware in the present
instrument makes it possible to switch
among a variety of operating modes by
making changes in software only.
This work was done by J. D. S. Danielson
of PhotoSense LLC for Johnson Space Center.
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paper) at www.techbriefs.com/tsp under the
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
PO Box 20687
Boulder, CO 80308-3687
Refer to MSC-22906-1, volume and number of this NASA Tech Briefs issue, and the page number.