Calibrating image quality measurement
FEBRUARY 16, 2009--From cell phone cameras to camcorders, digital imaging is ubiquitous in people's lives.
FEBRUARY 16, 2009--From cell phone cameras to camcorders, digital imaging is ubiquitous in people's lives. Despite the proliferation of consumer options, there are still no standardized objective metrics to quantify the overall performance of these systems. Several International Standards Organization (ISO) standards have quantified different aspects of performance, such as veiling glare, optoelectronic conversion functions, resolution, noise, and exposure. While these are useful technical specifications, they do not offer a way to combine all of the measurements to predict overall quality.
To overcome this problem, Elaine Jin and Brian Keelan of Aptina Imaging (San Jose, CA, USA; www.aptina.com) has developed a softcopy ruler method that enables the calibrated visual assessment of image quality. The method consists of three parts: a set of ruler images developed to meet the requirements set by ISO 20462, a software tool that displays the ruler and test pictures and collects observer responses, and a specified viewing environment.
The construction of the ruler images requires quantifying the MTF of the entire imaging chain, and manipulation of its shape using digital filtering to agree with the reference shape as defined in ISO 20462, Part 3. This process permits her to estimate the absolute quality using the standard quality scale (SQS) defined in the standard. For more information, go to: http://spie.org/x31563.xml?ArticleID=x31563