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. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Electronics/Computers category.
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:
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Refer to MSC-22906-1, volume and number of this NASA Tech Briefs issue, and the page number.