Polygon mirror scanners in biomedical imaging: a review

Abstract

We review briefly the different applications of polygonal mirror (PM) scanning heads in biomedical imaging, with a focus on Optical Coherence Tomography (OCT). This overview of biomedical optical systems that employ PMs include: (i) TD (Time Domain) OCT setups, where PM may be utilized for generating the modulation function of the system without separate translation stages; (ii) FD (Fourier Domain) OCT delay line systems, with PM arrays; (iii) broadband laser sources scanned in frequency, for SS (Swept Source) OCT, with the PM placed in various optical configurations; (iv) OCM (Optical Coherence Microscopy) system with double PMs; (v) 2D PM plus galvanometer-based scanner (GS) for fast lateral scanning (not only in OCT, but also in confocal microscopy). We discuss SSs, for which the various PMbased setups used are compared, in their evolution -from on-axis to off-axis polygons -and in the race to obtain higher scan speeds to achieve real-time in vivo medical imaging. The parameters, advantages and drawbacks of these different configurations are pointed out. A necessary comparison is also made with the much faster Fabry-Perot (FP) based SSs. Our approach on PM-based broadband laser sources scanned in frequency, based on a simple off-axis polygon configuration, is also presented. Some of its characteristic mathematical functions are inferred and evaluated.

Laser scanners: from industrial to biomedical applications

“…While these have been initially applied for industrial dimensional on-line systems [5][6][7], a similar setup can be applied -as well as the analysis developed [15,16] for SSs with off-axis PMs and telescopes. Other interesting setups are also using PMs in biomedical imaging (in OCT, but also in other applications, such as confocal or multiphoton microscopy), as we have reviewed in [18]: telescope-less SSs (in Littrow or Littman configurations [47]), scanning delay lines for FD OCT [43], 2D scanning systems with PM plus GS, and setups with double PMs, prismatic [48] or pyramidal [49]. …”

“…(1) reflective: with rotational single mirrors -monogons [1,2,6]) or polygonal mirrors (PMs) [5,[11][12][13][14][15][16][17][18] -or with oscillatory mirrors (with adjustable scan frequencies -galvanometer-based scanners (GSs) [19][20][21][22][23][24][25][26][27][28][29][30][31][32] or with higher but fixed frequencies -resonant -the latter including MEMS (Micro-Electro-Mechanical Systems);…”

Mathematical model of a galvanometer-based scanner: simulations and experiments

“…Their characteristics (advantages and drawbacks) make each of them suitable, by example for biomedical imaging, for specific setups [15]. Thus, some of them can be more widely used, while others, by example the polygon mirror scanners have a very clear niche [16], especially for fast uni-directional scanning, as in laser sources scanned in frequency for Swept Source OCT [6,17], in scanning delay line Fourier Domain (FD) OCT [18] or in 2-D scanners (in combination with a galvoscanner) [18].…”

Risley prisms scanners with different configurations: a multi-parametric analysis

“…The most utilized are galvanometer-based [4], with polygonal mirrors of different types [5][6][7], electro-or acousto-optical [8]. 2-D scanners are obtained with combinations of such devices or with other, different configurations, including with refractive elements, such as prisms [9][10][11][12][13][14][15] or lenses [2].…”