Scanners with Risley Prisms: Modelling with Mechanical Design Programs

Abstract

Opto-mechanical scanners with Risley prisms (double optical wedges) are one of the most used scanning systems for applications that range from micromechanical endoscope probes to large optics for satellite positioning. The paper presents an exact modelling of the scan patterns produced using such systems, in a dedicated program for mechanical design-CATIA V5R20. This approach utilizes the characteristic parameters of scanners with Risley prisms: the ratio of the rotation velocities of the two wedges M = x 2 /x 1 and the ratio of their apex k = h 2 /h 1 . The advantages of this method with regard to analytical solutions and with regard to approximate methods are pointed out. The similarities of this exact modelling of this type of scanners with the theory of mechanisms are highlighted. An experimental part validates the theoretical results. Driving solutions at the precision level required by these devices are presented.

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

“…This study belongs to our research direction on Risley prisms devices [28], in particular scanners [3,19], to characterize their scan patterns [31,32] and to develop constructive solutions [36] that are appropriate for a variety of applications, including for miniaturized scanning devices for OCT endoscopy [43].…”

“…We have previously modelled the exact scan patterns of scanners with Risley prisms [31,32], and analysed them with regard to the fundamental parameters introduced by Marshall [11]. We are currently working on different optomechatronic constructive and control solutions of this type of scanner for different diameters of the prisms [36].…”

“…The most used type of such devices are with two rotational prisms, although variants with three prisms or with two achromatic doublets [30] have also been developed and studied. The two rotational Risley prisms scanners have been studied analitycally [13][14][15] and by modelling approximately [11] or exactly [31,32] their scan patterns. FEA (Finite Element Analysis) has been performed [33] for large diameter prisms -as used in special applications like laser positioning of satellites.…”