Overview
In the FemtoSmart Resonant microscope, Femtonics combines high-speed and high-sensitivity imaging of living tissues by using a fast resonant scanner. Resonant-scanner-based raster scanning acquires images of the entire field-of-view ~5 times faster than galvanometric-based scanning: it is therefore the most appropriate choice for imaging the entire field-of-view at high frame rate.
Uninterrupted high-speed imaging
The resonant scanner consists of a fast oscillating mirror for x-axis deflection and a galvanometric mirror for y-axis sweep. Thanks to the 8 kHz oscillating speed of the fast x mirror, the microscope is capable of gathering images at 31 frames per second for hours.
The velocity of the resonant scanner is non-linear: the speed is different in the center and at the edges of the frame. In the microscope, Pockels cell limits the scanning range to that portion where the scanning velocity is near linear, avoiding photobleaching/photodamage at the two sides of the image. Scan electronics performs dynamic pixel dwelling for data linearization and to cancel out image distortion.
FemtoSmart Resonant scans with high velocity thereby distributing excitation to a larger area resulting in decreased photodamage. This idea, called LOTOS method (Varga et al, PNAS (2011), Chen et al, Nature (2012)) involves imaging at high frame rates at lower excitation energy per pixel. As a result, the microscope allows imaging even small dendritic segments within the brain of behaving animals, e.g. to record individual calcium transients processing whisker stimulation.
The shortest possible optical path allows enhanced photon collection efficiency thanks to our patented travelling detector system
Using the highest sensitivity GaAsP photomultipliers (quantum efficiency less than 40%), which are optimized for scattered photons
Carefully chosen high quality filtersets
The fast XY-scanning, combined with fast Z-movement, ensures near real-time measurement of a 3D volume. In frame by frame Z ramping mode, the fast objective positioner (a piezo objective positioner or Liquid lens objective kit) takes a step between each plane, and as result, parallel planes are scanned. In continuous Z ramping mode the fast objective positioner steps between each scanline, and as a result, slightly tilted planes are scanned. This scanning mode enables faster volume scanning rates for volumetric physiology imaging.
3D volume scanning about neuronal activity in V1 region of the mouse brain