We have simulated the effects of the number of bits and the sampling rate of a digitizer on the performance of lifetime measurements. We found that the number of bits of a digitizer is important to obtain certain accuracy in lifetime measurement. There exists a certain critical sampling frequency of a digitizer required to separate a certain lifetime differences in a double exponentially decaying intensity profile. We did these simulations by using Monte Carlo simulations with least-square curve fitting algorithms.
Angles of polygon scanners have been measured by using rotary encoders, autocollimators or indexing tables. These methods produce precise angle values but require removal of polygon mirror from its motor. For resolving this inconvenience, we introduce a simple angle measurement method by measuring timing jitters of a scanned beam in the time-domain with a high-speed detector and a digitizer while a polygon scanner is rotating at its full speed. Our setup includes a 635 nm wavelength semiconductor laser, a high-speed photodiode, two lenses, and a high-speed digitizer. A polygon scanner with 12 facets were tested with a rotating frequency of near 350 Hz. To detect the signal of the photodiode, we used a high speed digitizer which has a sampling rate of 2Gs/s with 256MB on-board memory. We obtained repeated pulsed sequential photodiode signals for 12 mirror facets of the scanner. Angle variations and their jitters for 12 scanner mirror facets were successfully calculated from measured data. We have repeated same experiments with a photomultiplier tube and compared results with those measured by a photodiode.