In order to create a light sheet, DSLM version scans a beam over the axis using a galvanometric mirror. This mirror changes its deflection angle depending on the voltage applied. However Micromanager does not provide a straightforward way to control galvo devices. We have design a solution using an Arduino board (AB1) modifying both, the Micromanager Device Adaptor for Arduino and the Micromanager firmware loaded on the Arduino board. Instead of the original Micromanager Device Adaptor, the modified one sends two words (16 bits) one containing the amplitude information and the other one the frequency codified in a 12 bits base. The Arduino firmware reads those values, calculates the corresponding triangular wave and then sends the 12 bits of each point in the triangular wave using the modified “analogOut” function in a continuous loop through a 12 bit DAC chip (MCP4921) to the galvanometric mirror (GM). A defined delay between these points controls the wave frequency. In order to exit the loop to stop the galvos or modify the triangular wave parameters an external signal is needed. This signal will be connected from pin12 on the AB2 (that controls the sample rotation) to pin2 on AB1.
Schemes
Circuits
Software
For installation upload this file on the Arduino memory.
Micromanager Device Adaptor for Galvos
For installation copy mmgr_dal_Arduino_UIC. dll file on the Micromanager folder.
During hardware configuration load the device Arduino_UIC.
Arduino provides signals between 0 and 5 V, however galvos are optimally designed to oscillate around the 0 V with positive and negative voltages.
To obtain this behaviour we implemented the shield circuit shown in the figure. This circuit is based in an OP07 operational amplifier which is used as an offset regulator. The amplification of the input signal can also be controlled, by changing R1 and R2.
In that way we are able to obtain triangular waves with amplitudes up to ±7.5V and frequencies up to 300 Hz for 200 points and 500 Hz for 100 points.
Images