Vision need not be limited to the visible, and some creative thinking might reveal new opportunities.
by Andy Wilson
editor
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My brother Dave believes education is everything. So it’s only natural that with his third-class honors degree in device physics from Warwick University (Coventry, UK; www.warwick.ac.uk), he wants something better for his kids. He has decided that Cambridge University (Cambridge, UK; www.cam.ac.uk) is the place his daughter should attend. She has already attained straight A+s in the sciences, languages, music, and art. So, with great enthusiasm my brother set off with his daughter to view the campus, the colleges, and the chapels to find out what it takes to enter this hallowed place of learning.
After arriving, Dave was introduced to a second-year student whose task it was to escort them around the halls. But he only had one thought in mind. What did it take to enter? They were told that being allowed to study there included passing a verbal exam attended by a number of professors. But what were the questions Dave wanted to know.
“They only asked me one,” Dave’s escort informed him. “Imagine,” said the student, “you are sitting in front of a desk. On the desk is an invisible box. Inside the invisible box is an object that’s also invisible. Your task is to find out what the object is.”
Dave was flummoxed. Obviously this was an impossible task. Or so he thought. But the professors had thought “outside the box” in a manner obvious to those involved in image processing and machine vision.
The word “invisible”-an obvious allusion to a term used two centuries ago-was the key. Strike the first box with something unseen by human vision-audio, IR, UV, x-rays, or some other “invisible” wavelength of radiation. Penetrate the first box and perform a similar task on the second. After a number of trials, the object will be revealed.
But the question reveals more than the answer. Those in education often teach by rote from textbooks written years ago. Their job is to “educate” but not explore the mind of the student. Luckily, professors at Cambridge University seem to be different. By thinking “outside the invisible box” they bring more than a linear, blinkered logic to education. They bring a process that involves abstraction of thought and ideas that may appear more like science fiction than science.
Visible light has been used for more than 30 years to inspect and analyze products in machine-vision systems. For more than a century, x-rays have been used to diagnose the human condition. Infrared systems are now in use in a number of industrial process-monitoring applications. And, as engineers explore these new wavelengths, they are finding new applications. Terahertz imaging, for example, is now becoming the wavelength de jour in security applications.
Yet, until recently, those in the machine-vision industry have limited their focus, concentrating on capturing, processing, and displaying images visible to the human eye. Multispectral analysis has been limited to expensive military applications, in which each wavelength can provide invaluable information about a potential threat. Things are changing, however, as systems developers are thinking more outside the invisible box.
With semiconductor geometries shrinking daily, CCD and camera vendors are developing devices that capture data in the UV spectrum, allowing smaller IC features to be understood. For printed-circuit-board analysis, machine-vision vendors are exploring the benefits of x-ray, IR, and visible radiation to examine the integrity, performance characteristics, and positions of components on circuit boards.
Combining imaging data from multiple modalities, such systems will increase both product reliability and inspection throughput. But it’s not just a matter of applying different wavelengths to discover the contents of invisible boxes. It may also involve combining such modalities with novel mathematical theories, abstract reasoning, and biological and chemical analysis-something of which the folks at Cambridge are only too aware.
