ScanImage's photostimulation module supports simultaneous multi-site stimulation by utilizing a phase-only SLM for wavefront shaping. Since the SLM update rate and the achievable scan angle of the SLM are limited, the SLM can be used in series with two galvanometer mirrors, which allow to scan the projected dots over the sample.
Setup
A detailed description of adding an SLM to the photostimulation path can be found in the following publication:
Nikolenko, V. et al. SLM Microscopy: Scanless two-photon imaging and photostimulation with spatial light modulators. Front. Neural Circuits 2, 5 (2008).
Registration
To ensure accurate targeting, the Galvo/Galvo path, the SLM path and additional imaging paths need to be aligned to each other. ScanImage includes an Alignment Tool for this purpose. After configuration, the SLM path will show up as a scanner for imaging in the configuration window.
Zero order diffraction
The diffraction efficiency of any SLM is typically below 100%. This means that a portion of the incident light remains undiffracted and contributes to the zero order diffraction spot in the image plane. Typically, this zero order diffraction spot is undesired. The most common techniques to mitigate this effect are
- Block the zero order spot in a conjugated image plane using a reflective dot on a window.
- Defocus the zero order spot to shift the energy outside the sample or at least outside the region of interest. The SLM can be used to compensate for the defocus during a photostimulation.
For the second solution, ScanImage allows to define a static offset in the GUI, which can be used to compensate for the defocus.
A: Telescope to demagnify the beam onto the X,Y-galvo mirrors
B: Scan lens and tube lens
C: Objective
A zero-order beam block can be added at the conjugated image plane in telescope A
For a more detailed schematic see
Nikolenko, V. et al. SLM Microscopy: Scanless two-photon imaging and photostimulation with spatial light modulators. Front. Neural Circuits 2, 5 (2008).
