How can I coordinate a TTL microscope shutter with a camera for long-exposure time-lapse imaging?

Question

I’m setting up an inverted microscope for long-term cell imaging. The planned light path is: halogen light source → TTL-triggerable electronic shutter → specimen → objective → camera. We need to capture one image every 10–15 minutes, with exposures around 1 minute.

The electronic shutter and camera may come from different vendors, so I’m trying to find a simple way to synchronize them. Ideally, when the external shutter opens, the camera starts a 1-minute exposure, then the shutter closes afterward.

Is there an elegant, low-cost way to coordinate this? For example, could a microcontroller trigger both the microscope shutter and the camera in sequence? Would bulb mode and a remote shutter input be the right approach?

user44829 · Answer

Using an Arduino or similar, you can trigger the external shutter or you could switch the light source with a relay. If the light source runs directly from mains, you should leave the latter part for an expert. So far it is unclear why you need that external shutter.

After you started the light for the specimen, the Arduino can start the exposure with the camera. You can use the external camera trigger of the camera for this. The camera should be set to bulb mode. That way you can control the exposure time with the Arduino. The cables for the external trigger come in various forms, depending on camera brand and type. Usually you need to make a contact between two wires to start the exposure and interrupt the contact to stop the exposure. Use an optocoupler, controlled by the Arduino, to switch the wires together. The different pinouts for the shutter release connectors of various cameras can be found here.

This way everything is controlled by one system and you don't need to sense whether the light is already active before you start the exposure. Repeating this procedure automatically every 10 to 15 minutes can also be controlled by the Arduino.

As you have a long exposure time, this will increase the noise of the image as the sensor get's warmer. I would recommend getting a camera which features dark frame substraction. After a camera with this feature finished a long exposure it will take another exposure of same exposure length with it's internal shutter closed. The noise found in this dark frame is then substracted from the actual image, improving image quality.

How can I coordinate a TTL microscope shutter with a camera for long-exposure time-lapse imaging?

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