LED Line Lights in Line Scan Applications
In this post we will describe line scan applications; the reasons for selecting a line scan solution and explain some of the most important characteristics of LED Line lights for line scan applications.
What is a line scan application?
A line scan application is defined as a machine vision application that utilizes a one-dimensional (1D) line scan camera. Fundamentally, a line scan camera differs from an area scan camera in that it has a linear array of sensors as opposed to a two-dimensional (2D) matrix. A 2D image is obtained by the system’s 1D camera which is built up line by line as the target is in motion. In some applications, e.g. rail inspection, it is the motion of the camera that creates the 2D image but this type of system is much less prevalent in the manufacturing industry.
The most common type of line scan application is in web manufacturing of materials like paper, foil, film and high resolution imaging of larger discrete parts. These webs operate at very high speeds and often operate 24/7. Reliable, low maintenance LED Line lights play a vital part in maintaining the quality of output and avoiding downtime.
High Resolution Applications
For a given cost, line scan cameras have the potential to provide much higher resolution images than their area scan counterparts. For this reason, line scan is often the vision system of choice when high resolution defects need to be identified in products that are moving. An example of this type of application is in the solar industry, when silicon wafers are inspected for micro cracks and occlusions. The high resolution is achieved by the density of pixels across the 1D sensor (cross-web resolution) and the line rate at which the camera runs (down-web resolution). As line rates tend to be high frequency the result is short exposure times, which means line scan systems require more light than typical area scan systems.
Line scan technology can also be used in the imaging of cylindrical objects. Here, the target is rotating as the camera acquires the image lines. The resulting 2D image is inspected by the vision system. This type of system is commonly used in the food & beverage and pharmaceutical industries for critical applications such as final label inspection.
Line scan vision systems are also used in restricted spaces. In certain applications, particularly where vision systems are being retro-fitted onto existing web production lines, space constraints make the form factor of the illuminators critical.
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