Experimental investigations of the scanning functions of galvanometer-based scanners with applications in OCT

Abstract

We analyze the three most common profiles of scanning functions for galvanometer-based scanners (GSs): the sawtooth, triangular and sinusoidal functions. They are determined experimentally with regard to the scan parameters of the input signal (i.e., frequency and amplitude). We study the differences of the output function of the GS measured as the positional error of the oscillatory mirror from the ideal function given by the input signal of the device. The limits in achieving the different types of scanning functions in terms of duty cycle and linearity are determined experimentally for the possible range of scan parameters. Of particular importance are the preservation of an imposed duty cycle and profile for the sawtooth function, the quantification of the linearity for the sinusoidal function, and the effective duty cycle for the triangular, as well as for the other functions. The range of scan amplitudes for which the stability of the oscillatory regime of the galvo mirror is stable for different frequencies is also highlighted. While the use of the device in certain scanning regimes is studied, certain rules of thumb are deduced to make the best out of the galvoscanner. Finally, the three types of scanning functions are tested with a Fourier domain optical coherence tomography (FD OCT) setup and the conclusions of the study are demonstrated in an imaging application by correlating the determined limits of the scanning regimes with the requirements of OCT.

Surface imaging of metallic material fractures using optical coherence tomography

“…DC2 feeds a balance detection receiver (Thorlabs, Newton, NJ, model PDB460C). 20% of the SS power is launched toward the object arm via lens L1 (focal length 15 mm), which collimates the beam toward a pair of scanners XYSH (Cambridge Technology, Bedford, Massachusetts, model 6115), followed by an interface optics made from a scan lens, L2 (50 mm focal length) [17]. The power to the sample S is 2.2 mW.…”

Building an optomechatronics group in a young university in Western Romania

“…We have investigated them theoretically at first [21][22][23], and demonstrated [23] that the optimal scanning functions to be used is not linear plus sinusoidal, as pointed out previously in the literature [19], but linear plus parabolic -to produce the maximum possible duty cycle [23]. Experimental studies were also performed, for OCT applications, determining the optimal use of GSs in such systems [24]. These hot topics are followed by other studies, especially with PG students (Section 4).…”

“…The research on which we obtained the rules-of-thumb for the optimal input functions of 1D GSs in OCT setups continues. We have so far demonstrated, in collaboration with the ODALab, UoRochester, NY [24] that the most artifact-free OCT images are obtained with triangular scanning, but further investigations are necessary to apply these aspects in OCT, as demonstrated by other groups that applied these aspects [55]. OCT applications, on which we are currently working on, are focused on dentistry (materials for dental works and prosthesis, investigations of soft and hard tissues) [56] -in collaboration with the School of Dentistry, Victor Babes University of Medicine and Pharmacy Timisoara -and on endoscopy and colonoscopy -in collaboration with the Departments of GastroEnterology and Hystopathology, Arad County University Clinical Hospital.…”

All-reflective multiphoton microscope

“…The ray fan aberrations (less than ± 0.2mr) of different wavelengths overlap each other due to the reflective design of the system. A triangular function is used to drive the galvo scanners to reduce the artifacts caused by high-speed movement of the mirrors at large scanning angles [28]. …”