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TECH FOCUS POSITIONING EQUIPMENT


Moving on the


micro scale Part of the development of advanced endoscopes is scaling down the components that position the micro-optics inside of them


Latest product releases


T


he miniaturisation of positioning components such as piezomotors and drivers will


be crucial for the medical market going forwards, as minimally invasive surgical tools such as endoscopes become more prevalent. These were the opinions on the exhibition floor at the Bios trade show for biophotonics and biomedical optics, which took place before Photonics West in San Francisco on 27 and 28 January. The team at Electro Optics were told by engineers at Physique Instrumente (PI) that, whereas the positioning technology for microscopy stages is quite well established, the challenge is moving optics at a micro scale, for example in an endoscope. Minimally invasive procedures enabled


by endoscopes not only reduce discomfort for patients, but help to reduce the strain on healthcare providers by saving time and resources. With the evolution of microelectronics and compact imaging sensors, small cameras can now be integrated into the endoscope tip (chip- on-the-tip), improving image quality. However, traditional chip-on-the-tip endoscopes use fixed focus optics, which are only able to provide optimum display for one object distance. If the object is at a different distance, the image loses focus. By integrating an actuator between the optics and the image processing chip, it could be possible to achieve variable focusing and the whole abdomen, or objects with variable distances, can be displayed in sharp focus. The potential installation space with diameters of no


more than 10mm is very small. Miniature piezo motors’ direct-drive eliminates converting rotation into linear motion, removing the need for gears and other mechanical components that can wear and reduce reliability. Piezo motors are small, lightweight, and consume minimal energy, and can hold a position without consuming power. A number of different piezo motor principles are feasible – mini-rod inertia piezo motor, ultrasonic piezo ceramic motor, flexure-type inertia motor and ratchet-type piezo motor – and all provide the precision for focus and zoom control in endoscopy. In addition to piezoelectric motors, traditional electromagnetic linear motors (voice coils) can also be used.


“By integrating an actuator between the optics and image processing chip, variable focusing could be possible ”


Voice coil actuators are related to


the transducers used in loudspeakers. They can be manufactured with small dimensions and provide motion ranges in the millimetre to centimetre range, contributing to a higher image quality and depth of focus in the next generation of chip-on-the-tip endoscopes. Compact piezo XY scanners can be


used for two-photon endoscopy, which allows live tissue to be imaged at greater depths. Recently, a 2mm-diameter spiral fibre scanner was used for eye imaging, which provides lateral and axial resolution as low as 1.5µm.


Light sheet microscopy Selective plane illumination microscopy (SPIM), a type of light-sheet microscopy, is a cell-friendly method for imaging live specimens as it only illuminates the region of the sample that is being captured, minimising phototoxicity and photobleaching.


The diSPIM is a flexible and


easy-to-use implementation of SPIM that allows for dual views of the sample while mounted on an inverted microscope, co-developed by the lab of Hari Shroff at the US National Institute of Biomedical Imaging and Bioengineering and Applied Scientific Instrumentation (ASI). ASI offers all of the necessary hardware to implement the diSPIM. The company manufactures the optomechanical elements, including the motorised stages, 2D galvos for creating and moving the light sheet, and the piezo objective movers. Objectives, lasers, and cameras are required to complete the system; users can procure these other items themselves, use the services of various system integrators selling the diSPIM, or purchase them via ASI.


32 Electro Optics March 2018 @electrooptics | www.electrooptics.com


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