The quality of a printed image can have as much to do with microscopic dot sizes and shapes as the type of hardware, software analysis tools and paper being used.
Recent hardware innovations have greatly increased the volume of images that can be handled in a given time frame, which may magnify the problems of running a production site while maintaining an inadequately tuned system, said Dr. Patricia Bresnahan, recognition engineer at Scan-Optics Inc. in Manchester, Conn.
Bresnahan recently authored a research paper, High-Volume Image Quality Assessment Systems: Tuning Performance With An Interactive Data Visualization Tool, which evaluated the growing need for performance tuning and analysis software tools in the high-volume image quality assessment community.
“The systems are getting more complex, and in order to get them working properly there are more and more parameters that have to be set,” she said. “And the impact of changing any one parameter can impact the performance.”
The study tested the use of technical image processing algorithms, which the company labelled the Scan-Optics Threshold Tuning Tool, to accurately measure image quality.
“How do you know if a line is solid or broken, how do you know if an image is blurry or crisp?” Bresnahan said.
ScanOptics is assessing the inclusion of such a tool in its future products as a more accurate and highly visual means of measuring system performance. This would be especially helpful when companies are trying to decide whether or not to purchase a product, she said.
“We were first going to show good images and bad images so customers could measure difference. But then the problem got to be that no one could decide what was good and what was bad.” An appropriate tool could help users draw a line between the two, she said.
Speed and high volume are not the only factors affecting image quality, said Michael Moore, product marketing manager at Tektronix Inc. in Wilsonville, Ore.
“Even the best inkjets will be affected by the paper that you print on. To a lesser extent, lasers printers are also affected by the paper used. Also, lasers are attempting to shape dots out of toner particles – if you look at a microscopic level, you can see a difference between the dot shape,” Moore said.
Tektronix recently came out with an alternative to these systems, the Phaser 840, which uses solid sticks of colour instead of inkjets or toner. These provide more consistent quality because the ink does not sink into the paper, Moore said.
“With solid ink, we can keep the (dot) shape a very consistent round dot. That’s the microscopic level, so who cares? Well, when you do subtle blends or gradients, you will tend to get some form of banding or demarcation (using an inkjet or laser printer),” he said.
To address accuracy, the product also uses a single, permanent print head for all the colours.
“So the calibration between the cyan, magenta yellow and black is set precisely at the factory, and it won’t change. That is a huge advantage because your registration between colours is going to be exact.”
Don Donoahue, executive director of the Canadian Information and Image Management Society (CIIMS) in Oakville, Ont., said quality assessment for images should be as individual as the organizations themselves.
“It has to be customized, because no two companies have the same type of documentation or want to capture the same type of information.”
Donoahue pointed out that many images these days are electronic, and may never see paper form. In fact, the federal government is currently rewriting the standard for microfilm and images as documentary evidence, largely due to new technologies such as electronic commerce and digital signatures, he said.
But despite these changes, making a hard copy printout is still the best way to determine if the image will be useable, he continued.
“A lot of people will take a scanned image and run it through an OCR (optical character recognition) package into the computer, without making sure that the quality of the images that they have captured are good enough to be able to be recognized by their software,” he explained.
“The whole technique in imaging is if you can print back from your record and get a satisfactory print, then you basically have a good quality image. If you don’t print back and you don’t test it out, you are really not sure that what you captured is all there.”
