Journal de recherche en optique et photonique

A Novel Library for the Correction of a GalvoScanner’s Non-Linearity at High Frequencies

Mohammad RN Avanaki

Galvo-scanner is a two dimensional beam steering system essentially employed in microscopic imaging modalities. The advent of microscopy in tumor diagnosis and functional imaging of the organs and cells is apparently promising as it can unravel the intricate dynamics of the biological processes at microscopic level in real time. For instantaneous measurement of pigment (melanin) concentration and monitoring the fractional changes in oxygen hemoglobin saturation, the microscopic imaging system must be very rapid in terms of scanning and data acquisition. However the images obtained from such systems were found to be distorted. In an attempt to make the high speed imaging system efficient, we conducted an in-depth study on the problem, its causes and formulated an optimal solution. We studied and analyzed the behavior of a Galvo Scanner (GS) at different scan frequencies. A triangular signal is usually employed to drive the GS. Conventionally, the GS’s mirrors move in accordance with the input control signal at low scan frequencies (less than 100 Hz) but as we advance to higher scan frequencies (more than 700 Hz), GS fails to obey the input due to the inherent mechanical inertia of the mirrors. This scrambles the distance between the microstructures being imaged, thus leading to distortions in the images obtained. Therefore we propose a novel library of (purposely) distorted ramp signal to deal with this problem. The rationale behind this idea is to provide the GS enough voltage to overcome the inertia so that the resultant movement is a linear ramp. The results obtained showed a significant improvement in the behavior of the scanners in the terms of spectral width of the FWHM of the output signal.