Line Scan Cameras vs Area Scan Cameras – Which Is Suitable For Your Applications?
When it comes to developing an inspection system, machine vision integrators are faced with apparently unlimited alternatives. The choice between line-scan and area-scan cameras is perhaps the most important. While both serve the same purpose, the methods by which images are captured are vastly different.
Industrial Camera Classification
What is a Line Scan Camera?
Line-scan cameras scan a single pixel row at a time with a sensor that moves in a linear motion over an object, or more often as the item passes beneath the sensor, to make images.
As a conveyor or web travels for inspection, a 2D image can be recreated line by line in software. This makes it perfect for applications needing micron-level measurements, such as document scanning, print inspection, web inspection of paper, aluminium, steel, or glass, and comprehensive inspections. Line-scan may also analyze circular bodies without generating distortion in perspective.
Another advantage of line-scan systems is their smaller footprint, which allows them to fit more easily into tight spaces, such as when a camera must peer through rollers on a conveyor to view the bottom of a part. Line-scan cameras also produce smear-free images of fast-moving objects without the need for strobing or redundant processing of frame overlaps.
What is an Area Scan Camera?
Area-scan cameras, on the other hand, are more versatile. They comprise a huge matrix of pixels that record a 2D image of a particular scene in one exposure cycle with horizontal and vertical elements, for example in 640 × 480 pixels, and are used in most machine vision systems.
A simple way to understand the difference is that an area scan camera takes a single photo of a square or rectangle at a time, whereas a line scan camera takes hundreds of 1D pictures in a sequence and combines them into a picture of the same 2D area.
Area-scan cameras are best suited for applications where the object is stationary, even if only for a short period of time. Only by capturing overlapping images can an area-scan camera capture continuous materials without interruption.
Image Scanning Method of Area Scan and Line Scan Camera
Area Scan and Line Scan Image Sensor
Area scan cameras take a 2D area in one shot. It’s the same way we usually use mobile phone camera or DLSR cameras.
Line Scan cameras take one line area in one single shot. A copier is an example of a device that uses a similar scanning method in everyday life. When you insert paper and start copying, the red light of the laser passes through and scans paper, and the scanned lines are collected to create a single 2D image. Line Scan cameras scan images in a similar way. As the target moves, the Line Scan camera capture the target image line by line. Then each like taken is collected to create a single 2D image.
Comparison of image capturing methods between Area Scan and Line Scan Cameras
Area Scan Camera and Line Scan Camera Usage Environment
The following conditions determined which cameras is suitable for your applications.
Moving Target
Line scan cameras are suitable for use in environment where the target is moving. Therefore, it is often in web inspection environment where objects are constantly being produced. Typical examples of web inspection include film inspection and paper inspection.
To use a Line Scan Camera, the target must be moving (or the target can be stationary, and the camera is moving). If Line Scan camera is preferred, a system must be built in which either the target or one of the cameras moves. It is more difficult to build a system than an area scan camera because the speed of the target (or camera), must precisely match the speed of the camera’s image taking.
The Inspection Area Is Wide
Line scan cameras are suitable for use in environments that inspect large areas. A typical example is glass inspection. The size of the 8th generation display panel glass is 2200 mm x 2500 mm. To capture glass with an area of more than 4m², you will need several cameras. Line scan cameras do not have any restrictions on the height of the area that can be photographed, so when using a line scan camera, images can be taken with a few number of cameras compared to an area scan cameras.
Comparison of Inspection Areas of Area Scan Camera and Line Scan Camera
As per above image example, 3 area scan cameras are required to capture the inspection area at once. With Line Scan cameras, one camera is sufficient.
The usage of line scan camera is most suitable where the target is moving, or the inspection area is wide.
VTDI Series – Vieworks Hybrid TDI Line Scan Sensor
Vieworks developed a hybrid TDI line scan sensor to improve TDI line scanning performance. The Hybrid TDI sensor, which uses CMOS technology to build a CCD pixel structure, allows for ultra-high-speed picture captures with up to 256 times better sensitivity. VTDI is the first TDI line scan sensor concept.
Learn more on Vieworks’s TDI Line Scan Sensor
VC Series – Vieworks High Speed CMOS Area Scan Cameras
VC series is a series of CMOS cameras for machine vision applications that offer high resolution up to 151 megapixels and high speed up to 337.6 fps.
Programmable camera makes it easier to update the firmware in machine vision fields. VC Series supports Camera Link and CoaXPress interfaces and provides both global shutter and rolling shutter.
Learn more on Vieworks’s Area Scan Cameras
Contact us to assist you with product support: