Tag Archives: Scanning

Alvarez lenses and other strangely shaped optical elements

In typical microscopes, lenses or mirrors are moved forth and back to change the position of their focus. Tunable lenses like the electro-tunable lens or the TAG lens, on the other hand, are deformed by an external force and thereby … Continue reading

Posted in Imaging, Microscopy | Tagged , , | Leave a comment

Springtime for two-photon microscopy

Today, the fields and forests around Basel are full of flowers that try to disseminate their pollen. Fixed pollen are, apart from sub-diffraction beads and the convallaria rhizome, one of the most commonly used test/reference samples for fluorescence microscopy. This … Continue reading

Posted in Imaging, Microscopy | Tagged , , , | Leave a comment

Can two-photon scanning be too fast?

The following back-of-the-envelope calculations do not lead to any useful result, but you might be interesting in reading through them if you want to get a better understanding of what happens during two-photon excitation microscopy. The basic idea of two-photon microscopy … Continue reading

Posted in Imaging, Microscopy | Tagged , , , , | 8 Comments

All-optical entirely passive laser scanning with MHz rates

Is it possible to let a laser beam scan over an angle without moving any mechanical parts to deflect the beam? It is. One strategy is to use a very short-pulsed laser beam: A short pulse width means a finite … Continue reading

Posted in Calcium Imaging, Imaging, Microscopy | Tagged , , | 1 Comment

Preamplifier bandwidth & two ways of counting photons

For two-photon point scanning microscopy, the excitation laser is typically pulsing at a repetition rate of 80 MHz, that is one pulse each 12.5 ns. To avoid aliasing, it was suggested to synchronize the sampling clock to laser pulses. For this, it is important … Continue reading

Posted in Calcium Imaging, Imaging, Microscopy | Tagged , , , | 9 Comments

Fast z-scanning using a voice coil motor

We just published a paper on fast remote z-scanning using a voice coil motor. For 2P calcium imaging. It’s a nice paper with some interesting technical details. The starting point was the remote z-scanning scheme used by Botcherby et al. (2012) from … Continue reading

Posted in Calcium Imaging, Imaging, Microscopy, Neuronal activity | Tagged , , , | 3 Comments

Modulating laser intensity on multiple timescales (x, y and z)

In point-scanning microscopy and especially when using resonant scanners, the intensity of the beam is typically modulated using a Pockels cell. For resonant scanning, the dwell time per micrometer is not constant along the scanned line, and one wants either to … Continue reading

Posted in Calcium Imaging, Imaging, Microscopy | Tagged , , , | Leave a comment