Shutters

When only controlled with analog modulation, many laser sources do not reduce their emitted intensity to 0 watts. In such cases, residual illumination subjects the specimen to unnecessary irradiation between image acquisitions. Shutters overcome this by completely blocking the laser, albeit on a much slower timescale than direct modulation of the laser. With navigate, shutters automatically open at the start of acquisition and close upon finish.

Most shutters are controlled via a digital voltage. When the voltage is high (e.g., > 2.5 V), the shutter is open, and when the voltage is low (e.g., < 2.5 V), the shutter is closed.

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National Instruments (NI)

We can control these shutters using a digital output from a National Instruments (NI) data acquisition card.

Note

If the shutter opens and closes immediately upon starting an acquisition, try a different port for the digital I/O on the NI data acquisition card. Some NI devices (e.g.PCIe-6738) have port/sample size limitations. If the port/sample size is exceeded, the shutter will not open. For example, on our NI PCIe-6738 using port 0 for the shutter causes this issue, but switching the shutter to any port 1 channel fixed it. In comparison, for the NI PCIe-6259, using port 0 had no averse effects.

Configuration File

microscopes:
  microscope_name:
      shutter:
        hardware:
          type: NI
          channel: PXI6249/port0/line0
          min: 0.0
          max: 5.0

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Synthetic Shutter

If no shutter is present, one must configure the software to use a synthetic shutter.

Configuration File

microscopes:
  microscope_name:
      shutter:
        hardware:
          type: synthetic
          channel: PXI6249/port0/line0
          min: 0.0
          max: 5.0