Background

At the Scandinavian Microsurgery Academy in Gothenburg we train both pre-clinical personal and clinically active surgeons in microsurgery (for more information see http://microsurgery.se ). We constantly try to improve the training curriculum within a limited budget. One important part of the training is to give the participants continuous feedback and instructions while they work under the microscope. In order to do so the instructors need to see what the participants are doing. Traditionally this was done using a side-tube or an extra set of oculars . Both side-tubes and extra set of oculars are expensive and you can only see the work by one student at the time. Another option is to use a camera mounted in a phototube showing the work field on a screen. This allows you to follow several students at the same time. If the system have some means to output the feed you can also use the system as an instruction microscope for the entire group. Buying commercially available video systems is expensive and the microscopes also need to have a phototube.

We have tested a cheaper system based on a modified Logitech c920 camera (mounted in a new house with a c-mount, http://lukse.lt/uzrasai/2013-07-modifying-logitech-c920-to-for-cs-lenses/) in combination with Samsung 10” tablet and the CameraFi app, this combination cost around 600 EUR which is low compared to side-tube and commercially available camera system

With this system it is possible to view live full screen video, save images or video and cast (via Chrome cast) the live feed to the teaching screen in the front of the room. The downside is that in order to run the camera for a full day the tablet needs to be connected to the power adapter since the camera drains the battery. The solution is to use a Simulcharge OTG-adapter that allow you to charge the tablet at the same time as some other peripheral is connected but there are compatibility problems and it does not work without problems.

Possible improvement

• A system that is powered separately and more stable

• A cheaper system

• A more powerful system with more functions

Hardware Raspberry pi

We investigated the possibility to use a Raspberry pi computer and Camera V2 to meet the criteria above. 

The Raspberry pi Camera V2 needs a case with a c-mount in order for it to be used on a standard phototube. With special adapters it can also be used on a side-tube or in an ocular tube  

As part of this project three adapters were developed (for c-mount, ocular and side-tube) in two different versions, one for use with the standard flat cable (https://www.adafruit.com/product/1731) and one for HDMI cable in combination with the Pi Camera HDMI Cable Extension  (https://www.tindie.com/products/freto/pi-camera-hdmi-cable-extension/). All six adapters can be downloaded in STL format.  

The Raspberry pi need an external screen and can be connected to a HDMI or VGA compatible screen. In order to be able to avoid using a keyboard and mouse we used a Sundfounder 10” screen (https://www.sunfounder.com/10-1-touch-screen.html, http://wiki.sunfounder.cc/index.php?title=10.1_Inch_Touch_Screen_for_Raspberry_Pi) and in order to be able to mount the screen on a stand at the workstations a case for the screen and attached Raspberry Pi  was designed, this can also be downloaded in STL format

Software - microVIEW program

The video feed from the camera can be activated using a simple command line command but it does not give you any control of the camera settings or option for saving still images or video.  

The software that we use is written by Bill Williams (https://github.com/Billwilliams1952) and allow us to (not a complete list of functions):

• • View life video in different resolution settings without lagging

  • Adjust the camera settings

  • Change the saving location for images, video and time laps photos/video

  • Save still images

  • Save video

  • Create time laps video/photos

  • Stream the live feed over the internet

  • Annotate the video/images with date and time information

  • Change the interface language

•  

The finished setup

Below are pictures of the finished setups for all three adapters and the Sounfounder screen mounted in the 3D printed casing