Simple Goniometer Interface (SGI)

Simple Goniometer Interface (SGI) is a set of opensource software tools to be used as the user interface to contact angle goniometers, including dispensing control, image acquisition and data processing. The main components of SGI are written using python based on the PyQt5 and OpenCV suits.

Example GUI appearance

The appearance of SGI on a particular machine (hardware: MCA-3, KYOWA, OS: Windows) looks as image below, containing

• Main control panel
• Video preview windows of side and top cameras
• Worksheet for data acquisition

Compatible platform and hardware

The GUI part of SGI is platform-independent thanks to the PyQt5 framework. It can in principle to be used as controling interface to a variety of commercial and home-made contact angle goniometers, with proper modification of certain modules.

The current version of SGI is developed and tested on MCA-3 from Kyowa Interfaces Science Solutions Co. Ltd. For SGI to work on other hardwares, the following points are required:

• Video capturing device(s): have proper driver support on the desired OS, e.g. can be recognized by DirectShow on Windows or video4linux2 on linux. SGI uses VideoCapture module from OpenCV to handle the video preview and capture.
• Capture speed: video devices are recommended to be connected to bus lanes with high bandwidth (e.g. USB3). The theoretical upper bound of framerate is limited by the underlying library of OpenCV
• Dispenser control: most commercial droplet dispensers can be communicated using USB, serial port or GPIO. SGI provides abstract interface to the actual hardware code which can be further customized.

Functionalities

• Video preview and synchronization
• Scale bar visualization during preview
• Easy-to-modify camera configurations
• Synchronized image acquision on multiple cameras
• Dispenser control (hardware-dependent)
• Tablar result viewer
• Save and load result with formats compatible with commercial instruments (currently only FAMAS format)
• TODO Image post-processing
• TODO Droplet volume calculation

The idea

SGI was originally developed to add support for synchronized image capture on commercial contact angle goniometers, as such functionality was absent in the proprietary goniometer software. SGI also aims to provide a universal interface for contact angle goniometer devices with ability to

Hardware Setup

The following hardware components are required in combination with SGI.

• Long working distance optical lenses to be used for both side and top images (e.g. 12X zooming lens from Navitar)
• (Optional) Long working distance adaptor objectives (e.g. 2X ~ 10X Mitutoyo M Plan Apo objectives)
• Industrial cameras for image capturing (e.g. TIS USB3 cameras). If the camera used analog video output, analog to USB video converters are also needed.
• Programmable liquid dispenser. Ideally they can be communicated via usb / RS232 ports.

TODO Add scheme

Note: when mixing cameras / video capture cards from different manufactures, their drivers may cause confliction when capturing on the same bus line. A possible solution is to use an external SBM such as Raspberry Pi to isolate image capturing and stream the video via ethernet / firewire to the PC.

Installation

Dependencies

Hardware

• Suitable drivers for cameras / video capture cards
• Configure USB / serial ports connection to liquid dispenser

Software on control PC

• Python version >= 3.6
• pip and venv packages. By default these pacakges are shipped with official Python installer on Windows and macOS. On Linux you may need to install them by the name python3-pip and python3-venv with package managers such as apt or yum
• Commandline tools: git, ssh (if using SBM to isolate image capturing)

**(Optional) software on SBM (e.g. Raspberry Pi)

Ideally the SBM can run Unix-like system, minimal setup should contain:

• ssh service enable (for communication between control PC and SBM)
• motion (for video streaming)

Control PC part

The following steps assume using Unix sh

• Clone the git repo

git clone https://github.com/alchem0x2A/SGI.git; cd SGI

• Make virtualenv and install dependencies

python -m venv .venv; source .venv/bin/activate
pip install -r requirements.txt

• Modify config/cameras.json to configure cameras

(Optional) SBM part

Following example uses Raspberry pi with default user name pi and hostname raspberrypi

• Configure ssh to SBM by generating ssh-key

mkdir .ssh
ssh-keygen -f .ssh/id_rsa
ssh-copy-id -i .ssh/id_rsa pi@raspberrypi.local

• Now login to SBM using ssh:

ssh -i .ssh/id_rsa pi@raspberrypi.local

• Clone the git repo to ~/SGI. Edit the configuration ~/SGI/motion/motion.conf
• (Optional) disable the system-wide motion service

sudo service stop motion
sudo systemctl disable motion

Usage

Start program

Switch to the virtualenv and simply call the main.py script

source SGI/.venv/bin/activate
python main.py

Video capture

By default clicking the capture button dispenses the liquid droplet and catptures image.

Resizing video preview window

To reduce the video preview window size, double click the video frame. The window zooming loops between 1X, 0.75X and 0.5X times.

Change video preview scales

Horizontal and vertical scales are rendered real-time on the video frame, which can be changed by choosing different zooming factors for lens adaptor and microscope.