On the trail of the drop shape
Contact angle measurement with high-resolution USB 3.0 industrial camera
This is why they use USB 3.0 cameras from IDS in their video-based drop shape analyzer systems. Up to 200 frames per second at a resolution of 1200 x 800 pixels enable wetting processes to be captured without interruption and then precisely analyzed.
For example, the surface tension of liquids is of interest in cleaning processes, or in printing, painting, or coating; these processes can be optimized by exerting a targeted influence on the surface tension. Meanwhile, contact angle measurement is a measure of the wettability of a solid that is prepared for contact with a liquid. This wettability can also be deliberately influenced; depending on the requirement it can be improved (e.g. for preparing a paint) or reduced (e.g. if liquids should roll off better).
The fundamental functioning of these systems can be explained in relatively simple terms: A drop is dispensed onto a solid surface (sessile drop) or is at the tip of a needle (pendant drop). A camera is used to capture an image of the drop, which is transferred to image analysis software. A gray-scale analysis of the image is used to perform an initial contour detection. The second step is to fit a geometrical model describing the drop shape to the contour. This enables the contact angle to be determined, as it is given by the angle between the calculated drop shape function and the contact surface, the projection of which in the drop image is referred to as the base line.
It has an integrated memory and is consistently designed for the latest generation of high-performance CMOS sensors. These include the 2.3 megapixel IMX174 sensor from Sony, which delivers pin sharp pictures even at high frame rates. A sensor element with analog memory effectively prevents focal plane distortions by simultaneous reading of all pixel signals. It also supports a dual frame output mode with various exposure times.
In the KRÜSS drop shape analyzers, the cameras generally capture the wetting processes at up to 200 frames per second at a resolution of 1200 x 800 pixels. Depending on the measuring task, the videos can be anywhere between a millisecond and several hours long. "To investigate very fast processes, such as wetting of absorbent materials, a frame rate of up to 2000 frames per second can be achieved by reducing the image size to 90 x 60 pixels, and the data obtained still leads to reliable analyses," says Carsten Scheithauer, highlighting the possibilities provided by the USB 3 uEye CP camera from IDS. "All frames from the videos are used, as with our method the contact angle is continuously determined.“
The USB 3.0 interface transfers the huge volume of image information at high speed and without losses to the KRÜSS ADVANCE software, where the drop shape analysis is carried out fully automatically. This guarantees objective measured data unaffected by user interventions. When presenting the results, the software assigns the corresponding drop image to each measured value and displays it.
The benefits to OEM customers like KRÜSS are two-fold. Firstly, the camera can be very quickly and easily integrated into the system. Secondly, it works with all models and interfaces. This means that changes, e.g. the model, can be made at any time with no problems. The application does not have to be reprogrammed, only the camera-specific parameters have to be adjusted. This IDS driver philosophy is future-proof, just like the USB 3.0 interface. OEM customers such as KRÜSS can rely on the fact they will remain a standard on the PC in the long term, as universal availability, plug & play convenience, and high data rates are advantages that will ensure the interface's continuing success in the future and provide a basis for further development.
USB 3 uEye CP - Incredibly fast, incredibly reliable, incredible sensors
KRÜSS is a specialist in interfacial chemistry and the world's leading supplier of measuring instruments for surface and interfacial tension. Customers of the high-precision product solutions and scientific advice are above all research and development laboratories.