Comparison of structured illumination patterns for positioning: interference and dimming



Self-location of devices with a photodetector within an illuminated area can be realised if the illumination comprises a temporal sequence of rapidly displayed illumination patterns. These illumination patterns can be realised by projecting an array of visible light emitting diodes onto the tracking area. We compare 4 different illumination pattern sequences that can be used for this purpose, referred to as sequence A, B, C, and D, respectively. All of these sequences use differential signalling, i.e. the illumination patterns can be grouped in pairs of patterns that are the inverse of each other. For each pattern pair, we experimentally measured the differential signal to noise ratio (SNR) at a certain position. Earlier experimental data obtained with these four sequences can be found in the related dataset Here, we add to this existing data set with data that demonstrates dimming capability and further data on the effect of interference.

File dimming.txt contains an experimental demonstration of dimming. The first column is the time in milliseconds, the second column is the detector signal at 100% illumination level, and the third column is the detector signal at illumination dimmed to 25% using pulse width modulation. Sequence A was used for this measurement.

Files profile_i.txt, profile_ii.txt, and profile_iii.txt contain emission profiles of one LED pixel projected at 40 cm distance. The first column is the lateral position in millimeters, the second column is the corresponding angular position in milliradians, and the thrird column is the normalized optical intensity at that position.
File position_i.txt represents an ideal case without cross-talk and interference.
File position_ii.txt is experimentally measured under focussed projection.
File poition_iii.txt is experementally measured when the projection optics were deliberately moved out of focus.

File interference_A.txt is the experimentally measured differential SNR for sequence A corresponding to the above emission profiles. The first column is the pattern pair number, the second column is the SNR corresponding to profile_ii.txt, and the third column is the SNR corresponding to profile_iii.txt.
File interference_D.txt is the same but for sequence D.
Date made available22 Jun 2018
PublisherUniversity of Strathclyde

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