Advanced Imaging


Advanced Imaging Magazine

Updated: January 12th, 2011 10:01 AM CDT

Going Digital in Machine Vision

What are the key factors to consider when choosing a digital camera and frame grabber?
Figure 1
Figure 1: With a lower resolution, the images of bottle caps acquired would appear as seen here. Notice that a cluster of relatively lighter pixels compared to the dark background represents each cap. In this image, it is possible to discern that there are 24 bottle caps contained within the case, but little else.
Figure 2
Figure 2: Choosing a camera with a higher resolution, such as 640 x 480, which is commonly available, will yield a much-improved image that could be used to acquire more detail within the image as shown here. Note the detail that is not visible in Figure 1.

By Manuel Romero, DALSA

Machine vision requirements for better performance and higher resolution continue driving developers to incorporate digital cameras into their solutions. This trend will likely accelerate as the price and performance of digital cameras improves.

Assuming a digital imaging solution is required, here are some of the key factors to consider when choosing a digital camera.

Why use A Digital Camera?

Analog cameras continue to be the dominant choice in most machine vision applications for several reasons: huge installed base; mature technology with well-known standards; performance is often adequate for the application; and inexpensive, readily available cabling.

Until recently, there were several significant disadvantages to using a digital camera. They typically were higher priced than similarly performing analog models and, in addition to being expensive and bulky, digital camera cabling often was not easily interchangeable between different types of cameras and frame grabbers. However, with the introduction of the Camera Linkô and GigE Vision standards, digital camera cabling issues have largely been eliminated, while their performance continues to steadily improve, in many cases far exceeding that of any analog camera.

So why use a digital camera? They can deliver higher data rates, higher resolution and higher bit depths than analog cameras. Digital transmission also is inherently less susceptible to noise than analog, a key consideration for plant environments.

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