Fast scanning finds new inspection applications

14 April 2023

Technology advances including Artificial Intelligence (AI) and faster microprocessors are conspiring to make line-scan camera technology a compelling option in a host of new application areas.

Beyond the printing industry, the use of line-scanning has, traditionally been limited – in the electronics industry line-scan cameras are deployed for inspecting printed circuit boards, and in food processing, they can be found on nut sorting lines, scanning product flows as they cascade in a curtain past the camera. 

Essentially, they are used in scenarios where a moving, continuous material needs to be analysed for faults or defects. 

Area-scan -v- line-scan 
Area-scan cameras capture the data for an entire image in one go and the dimensions of the resulting image correspond to the number of pixels on the sensor. Line-scan cameras use a single row of light-sensitive pixels to constantly scan moving objects at a high frequency, capturing lots of ‘slices’ of an image which it then combines to construct the final image.  

Because of this, area-scan cameras are not so well suited to very fast web-based applications but are easier to install and use than line-scan cameras, making them ideal for straightforward machine vision tasks.

The complexity of implementing line-scan cameras can also be off-putting. Although capable of higher speed processing, line-scan cameras are more complicated and costly to install, mainly because the line rate of the camera must be synchronised to the speed of the object being detected. 

Advances in Image Signal Processors (ISPs) are now facilitating higher quality and faster processing of 3D images in more demanding environmental and lighting conditions. This enables the cameras to detect more critical detail and capture higher resolution images. 

For example, a 16K line-scan camera is now capable of detecting minute defects in PCB, EV battery, semiconductor, print and film inspection applications.

At the same time, system designers are harnessing Graphics Processing Units (GPUs) from the gaming industry for image processing. This PC graphics hardware can reduce algorithm and data processing time and enables the use of AI-powered analysis.

This helps improve pattern matching capabilities and accelerates inspection performance. The combination of advanced image sensor technology and AI is enabling line-scan cameras to infer increasingly complex insights from the vast amounts of vision data they capture.

Sophisticated sensor technology has also provided solutions to the problem of adjusting the line rate to match the speed of the material under inspection, enabling accurate, meaningful 3D analysis of the image at high frequencies using software algorithms. 

An AI-powered line scanning system is being used to inspect burgers for visual abnormalities and defects. The bespoke system ensures that every burger is visually perfect.
The camera system checks that each frozen burger is the correct shape and size, shows no signs of discolouration, freezer burn or ice crystal formation and is free from visual abnormalities such as large lumps of fat. 

A line-scan camera was specified for this application because the inspection needs to take place while the frozen burgers are being transported to a robotic pick & place packing system on a fast-moving conveyor belt. An area-scan camera would not be able to perform the required imaging at this high speed. The line-scanning system is able to locate, inspect and measure the burgers in real time. 

Further, an area-scan camera would only able to image the surface that faces upwards, not the underside of the burger. With the line-scan system, the burgers are passed over a very narrow gap between two conveyors and two cameras – one above and one below the conveyor – build up a 3D image of the complete burger as it passes over the gap.

This is only the start of what is possible when AI is combined with fast scanning technology, but it demonstrates how AI-enabled line scanning systems are breaking new ground in inspection speed, accuracy and repeatability.

Paul Wilson is Managing Director at Scorpion Vision.

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