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What should I take into account when choosing a camera for my imaging system?

Posted by Benny Koene on Fri, Aug 5, 2016

Cameras can be found in various types and configurations. But which camera will fit your application best? In this blog we will discuss some of the more important choices that have to be made when choosing “the best” camera for your measurement and inspection system.

Resolution and frame rate

The resolution and frame rate are often dictated by your measurement methodology. It is thus important to analyze your requirements for those two properties at the start of your search for a suitable camera. For the resolution you have to answer the questions how large your field of view has to be and how small the smallest features are that you need to be able to distinguish. By answering both questions you get the amount of pixels that you require for your application.

The frame rate is often dictated by your application as well. For example, if you have a conveyor belt that transports the goods to be inspected at a specific speed, then the camera has to be able to follow this throughput level.

Mechanical construction and reliability

Another consideration is in which environment the camera will have to work. Which temperatures will it have to endure? Are there vibrations that have to be taken into account? How many hours does the camera need to work without maintenance? These environmental conditions determine if you will need a rugged camera or not and if it is worth to investigate in a camera with a more robust mechanical construction.

Furthermore, the mechanical interface determines how well a lens will be centered on your sensor. Sometimes a lens can be connected directly on the mechanical housing of the camera while in other cases a lens mount has to be installed first. In both situations the alignment of the sensor with respect to the housing determines how well the lens will be centered with respect to the sensor. A misaligned lens might result in a lower quality image, i.e. blurring.

Interface

The choice of the interface is important in multiple ways. First, the interface determines the amount of data per second that can be sent to the processing host computer. The resolution and the frame rate will give you the amount of data per second that needs to be processed, and some interfaces might already turn out to be not useable due to their low bandwidth. However for high speed large data streams there are still several options to choose from like Camera Link, CoaXPress and USB3 vision.

The second important aspect of an interface is how you as the operator communicate and control the camera. It thus influences your way of working. Camera Link is a serial communication protocol standard where you have to type commands to control the camera. Both, USB3 vision, as well as CoaXPress use the GenICam standard with which you can use scripting files but you can also use a graphical user interface to control the camera. A graphical user interface often increases the user friendliness and ease of use. Some manufacturers have a GenICam implementation for Camera Link as well.

The third interface aspect that is of importance is the requirement of a frame grabber or not. USB3 vision does not require a frame grabber while CoaXPress and Camera Link both require a frame grabber. Notice that often the requirement of a frame grabber offers advantages instead of that it is a disadvantage. As the frame grabber takes care of the image data handling, the host computer resources can be used for other purposes. Furthermore a frame grabber is specially designed for image processing purposes and, especially for multi-camera solutions, will give you much more and simpler control over camera timing and triggering.

For more information about choosing the right interface read our e-paper:

Camera interface overview and comparison ePaper

Or our previous blogs:

Which digital video interface is best for global security systems?

Before coaxpress was the risky solution now it is the lowest risk machine vision interface option

Image Quality

If you have decided on above choices, the chances are big that there are still several camera manufacturers that offer cameras that meet your specifications. To make a final decision about the manufacturer the best approach is to compare on image quality. Ask the manufacturers for an evaluation camera and test how the camera performs in terms of image quality in your application. In a next blog we will offer you more information on how to compare image quality.

Topics: Vision System Optimization, Interface Technology

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