We design and develop linear scanning systems that perfectly fit fot the acquisition and analysis of surfaces. The linear scan differs from the standard camera acquisition (matrix sensor) by the fact that each single frame is made up by only one “line”. In the figure beside it is possible to notice the difference between a matrix and linear sensor and the way they work.
1.a Matrix Camera
1.b Linear Camera
The linear acquisition is suitable for the acquisition of not singularized objects that move at a constant speed on a conveyor belt or roller conveyor.
A linear scanning system is reccomended for the analysis in the production of objects and materials with a relevant length in which it is important to reach a high level of details. Indeed, a line scan image is the result of a composition of many consecutive frames that define the rows of the final image. Through this method the height of the image is not limited by the size of the image sensor and the final image do not suffer from lens distorsion along the height. Despite the width resolution being limited by the sensor dimension, the height depends by the travel speed of the object (coveyor speed) and the acquisition frame rate of the camera. Some Linear Scan cameras can reach a speed up to 80KHz this implies that if the object movement was of 800 mm/sec we would obtain a resolution of 0.01 mm/px!
Among the different case of applcation a linear camera is almost essential in the following: coil unrolling, analysis during sheet metal production, inspection of wood-knots on wood board, etc…
Linear Scan Examples
The image above has been acquired by a linear camera. It is possible to notice how the background is steady and repeats horizontally whereas the tram that moves at a constant speed appears well-proportioned.
Another example of line-scan acquisition is illustrated by the photo-finish. In this case we can see how the limbs of the athlets appears distorted since they undergo stronger accelerations compared to the rest of the body. This example highlights the fact that a scan-line image is a spatio-temporal rapresentation.
The image of the door was acquired through 6 neighbouring line-scan cameras and their images were compose togheter. The original image had a resolution of 30 Megapixels with a resolution of 0.2mm per pixel.