When you think about a line scan camera, probably the first thing that comes to mind are those strange-looking photo finish images we have all seen when watching the Olympics or other important races where the photo finish often is the determining factor for selecting the winner of a sprint or other fast race.
Yes, line scan cameras have been used for capturing significant moments in sports where no other camera or person can see exactly who has crossed the finish line first, especially when the difference between the runners or other athletes can be measured only in milliseconds or millimeters.
But there are other significant uses for these small yet highly efficient cameras.
Line scan cameras and machine vision systems for quality and process control
Machine vision systems for inspection and control featuring line scan cameras allow for highly efficient process control, automatic inspection, and robot guidance in various industries.
Line scan cameras are often used for machine vision systems to inspect and control industries and processes that involve fast-moving actions, processes, and objects.
Some of the most common uses of machine vision inspection and control systems featuring line scan cameras include the production of continuous webs or sheets of textile, glass, metal, wood, paper, and others. These productions usually consist of fast-moving conveyor lines. The product’s quality control is complicated to perform without the aid of this modern technology because detects are not visible to the naked eye, and more importantly, they cannot be seen without the production process being stopped.
With the help of a line scan camera, which is properly synchronized with the other elements of the machine vision system, this control can be performed automatically and continuously without stopping the conveyor line.
Another beneficial implementation of line scan cameras is to sort fast-moving or free-falling objects in the postal service or the food or pharmaceutical industry.
Line scan cameras are also indispensable for document scanning and print inspection of fast-moving conveyor lines,
They can be used to control the processes in industries where molten glass or metal cannot be inspected in any other way because the process cannot be stopped without the product being damaged.
How do line scan cameras work?
A line-scan camera typically has just one line of light-sensitive pixels, capturing just one line of an image at a time. But it is a very high-speed camera, so it can grab multiple consecutive bars or slices of the fast-moving object so that the machine vision system’s software can stitch them together to create a whole and very detailed image of the object being monitored.
This may sound quite simple, but such a machine vision system is quite complex and consists of various essential elements interconnected with reliable connections and working in perfect synchronization to produce such non-distorted and exact images.
Linear motion encoders measure the conveyor line’s speed to determine the frame rate and the number of lines the camera needs to capture per second or minute. They also detect when the line speeds up or slows down to adjust the line scan camera’s acquisition rate with speed.
When rotating objects such as pill bottles or other things are being inspected, a rotary motion encoder is used to determine the exact start and finish of a full rotation of each object and thus determine the acquisition rate of the line scan camera.
When the conveyor line carries separate products, trigger impulses determine the camera’s frame rate by the exact moment and place where the object begins and when and where it ends.
Frame grabber cards are also crucial parts of a machine vision system. They synchronize the sensors of the cameras with the light sensitivity. This is very important due to the fluctuating light of most fast-moving productions.
In the end, special software is used for automatically “stitching together” the separate slices of each frame and for creating the full image of the product or other object being monitored.
Why are line scan cameras useful for fast object monitoring and inspection systems?
Line scan cameras are typically tiny, so they can be placed in very compact or tight spaces where no other form of monitoring and control can be implemented.
They are also less expensive and are much more efficient than human quality control.
Plus, with a well-synchronized machine vision system, there is no need to stop the production process from performing detailed quality control of the products. This is a huge plus for many industries where production cannot stop; each production line causes big losses.
Line scan cameras provide much more detailed control of the products’ quality and can capture images of defects that are often impossible to spot by the naked eye.
Overall, these automatic quality and process control systems save huge amounts of time and money for different industries, and line scan cameras are often the centerpieces.
Production owners install line scan cameras with two or more pixel lines (TDI line scan cameras). These capture multiple images of a single line, which are then put together for a more precise and brighter picture of the moving object.
There are also color line scan cameras and line scan camera systems that can take 3D images of moving objects.
In other words, line scan cameras are indispensable for automatizing control and monitoring of several productions and industries.
