Motion‐free endoscopic system for brain imaging at variable focal depth using liquid crystal lenses

Abstract

We present a motion-free system for microendoscopic imaging of biological tissues at variable focal depths. Fixed gradient index and electrically tunable liquid crystal lenses (TLCL) were used to build the imaging optical probe. The design of the TLCL enables polarization-independent and relatively low-voltage operation, significantly improving the energy efficiency of the system. A focal shift of approximately 74 ± 3 µm could be achieved by electrically controlling the TLCL using the driving frequency at a constant voltage. The potential of the system was tested by imaging neurons and spines in thick adult mouse brain sections and in vivo, in the adult mouse brain at different focal planes. Our results indicate that the developed system may enable depth-variable imaging of morpho-functional properties of neural circuitries in freely moving animals and can be used to investigate the functioning of these circuitries under normal and pathological conditions.

Focus-tunable microscope for imaging small neuronal processes in freely moving animals

“…Liquid crystal optical devices have numerous advantages such as low electrical power consumption, high optical power, low weight and small size (Galstian, 2013). Although this technology has been successfully introduced in a variety of consumer electronic products (e.g., DVD readers, webcams, mobile phones), its integration in neuroscience imaging applications has been limited to the macroscopic system (Bagramyan et al, 2017). We have designed and built (Figure 1D) a small (5 mm × 5 mm × 0.5 mm), lightweight (≈ 0.1 g), low power consumption (≈ μW) TLCL that is perfectly suited for miniaturized neuroimaging systems (Ghosh et al, 2011).…”

Technologies for depth scanning in miniature optical imaging systems [Invited]

“…Therefore, microlenses-based depth scanning technologies have been highly favored in this field. Focus-tunable endomicroscopes have been developed by employing electrically tunable LC lens [ 119 ] and fluid-containing polymer lens [ 120 ]. The first fiber coupled 2P miniscope that was capable of axial-scanning has been reported by Ozbay et al for imaging in a freely-behaving mouse [ 121 ], where a commercially available electrowetting microlens was integrated into the system, enabling not only axial shifting (a 180-µm axial scanning) but also tilting of the focal plane at a 1.3 to 2.5-Hz frame acquisition rate.…”

Focus-tunable microscope for imaging small neuronal processes in freely moving animals

“…Liquid crystal optical devices have numerous advantages such as low electrical power consumption, high optical power, low weight and small size (Galstian, 2013). Although this technology has been successfully introduced in a variety of consumer electronic products (e.g., DVD readers, webcams, mobile phones), its integration in neuroscience imaging applications has been limited to the macroscopic system (Bagramyan et al, 2017). We have designed and built (Figure 1D) a small (5 mm x 5 mm x 0.5 mm), lightweight (≈ 0.1 g), low power consumption (≈ μW) TLCL that is perfectly suited for miniaturized neuroimaging systems (Ghosh et al, 2011).…”