Automated Paint Quality Inspection Using Camera Modules

Paint quality inspection is an important step in assessing the quality of manufactured goods. It is mostly used in the production of automotive, heavy machinery, special tools, etc. It is critical in these industries since the quality of the paint has a great role in deciding the life of the product.

This process was once carried out with the help of manual inspectors who would check the quality by looking at the painted surface using the naked eye (or sometimes with the help of magnifiers). However, this method came with limitations such as the following:

Manual inspection was time consuming and labor-intensive, and hence reduced the total throughput of the manufacturing process.
It was prone to errors as humans at times might miss tiny details or defects.

This made it necessary to automate the process – which is only possible using embedded vision and machine vision cameras. This is because paint quality inspection can only be done by analyzing the painted surface visually to spot coating issues like orange peel and pinholes.

In this article, let’s learn how automated paint quality scanners leverage camera modules to accurately examine painted surfaces for defects and quality issues.

Automated Vision Booths for Paint Quality Inspection

Given below are the key advantages of the system:

In addition to avoiding artifacts during image capture, being static also helps the system to reduce wear and tear, which in turn increases the life of the embedded vision system.
They can be interfaced with robotic and automated repair and refinishing systems for fixing the issues identified during quality inspection.

An advanced paint quality scanner is capable of inspecting multi-colored objects with high levels of accuracy.

Role of Cameras in Enabling Paint Quality Scanning

Embedded vision and machine vision have helped automate various processes in the industrial and commercial sectors. Among the many use cases, a few notable ones are:

Obstacle detection and autonomous navigation
Object recognition
Smart surveillance
Intelligent traffic management

Apart from these, quality inspection is another key area transformed by embedded vision that has found applications in multiple sectors of the industrial space – from pre-production inspection to in-process inspection and final inspection.

Paint Quality Inspection is a type of in-process inspection where quality checks are carried out before the final product is assembled. Here, cameras act as the ‘eyes’ of the paint quality scanner.

For example, consider a paint quality scanner used to automatically scan cars in a factory. In this scenario, embedded cameras capture the images and videos of the cars as they pass through the vision booth (remember the analogy of security baggage systems?). This data is then analyzed using specialized software to identify painting and coating issues. Sophisticated paint quality scanning systems are also capable of auto-teaching themselves to identify new colors.

What Types of Cameras are Used in Paint Quality Scanning?

In embedded vision, a one-size-fits-all all approach never works. This essentially means that every vision system might need a different type of camera depending on the end application requirements. A warehouse robot could use a global shutter camera while a service robot can perform its tasks with a rolling shutter camera.

This applies to paint quality scanning too. At the same time, while there could be minor differences in the types of cameras desired in different paint quality scanners, there are a few common things you need to keep in mind while choosing one.

Here, let’s have a look at them in detail.

Resolution and frame rate

In the past, paint quality scanning cameras came with a maximum resolution of 4 to 5MP. This was because of the limited bandwidth of the host processor. To retain a high frame rate (say 30 fps and above) in order to capture moving objects on the assembly line without blurring, the resolution had to be sacrificed.

However, modern-day host processors come with superior performance compared to their older generations. With advanced industrial PCs and embedded processors, it is possible to achieve a resolution of 4K even at a frame rate of more than 60 fps.

Owing to higher quality requirements, many product engineers today prefer high-resolution cameras (8MP or above) for paint quality scanning systems.

Shutter type

Is global shutter required in paint quality scanners?

Well, that depends on the speed at which the items on the conveyor belt or assembly line are moving. In most cases, a rolling shutter camera with a high frame rate is sufficient.

Interface

The choice of interface will primarily depend on the host processor you use. If you are using an x86-based system like an industrial PC, USB will be a great option – given its bandwidth and ease of integration.

On the other hand, if you are using an ARM-based processor, a high-bandwidth interface like FPD-Link or GMSL is a better choice.

High dynamic range

If the production setting has varying light conditions, a high dynamic range camera might be needed. Given that most production facilities have controlled lighting, an ordinary camera should be sufficient. But make sure to evaluate your environment before you take a call.

Color accuracy

It goes without saying that in a paint quality scanner, the ability of the camera to detect colors is of paramount importance. Variation in color is used as one of the parameters to detect defects in painted objects.

The quality of the ISP (Image Signal Processor) in the camera system is one of the factors that determines the color accuracy of a camera. A best practice is to start the evaluation with the default ISP that comes with the camera. You can consider using an external ISP in case you are unable to perform the required tuning using the default ISP.

TechNexion: High-performing Cameras for Industrial Applications

TechNexion develops embedded camera solutions for industrial, commercial, medical, and retail applications. An experience of more than two decades in the embedded systems space has helped us gain the technical know-how of how world-class embedded systems are built. Now with the rise of AI, we are more aware than ever of the importance of embedded vision in building a better world.

To meet the increasing demand of an Industry 4.0-driven world, we have designed specialized cameras for industrial applications such as paint quality inspection, factory automation, robotics, etc. Our cameras come with features such as high resolution, global shutter & rolling shutter, low light sensitivity, unmatched NIR sensitivity, and more. Learn more about our embedded vision solutions here.