Image Quality Evaluation

Image quality evaluation plays an important role in the design of many Hewlett Packard products, including imaging peripherals such as digital cameras, scanners, printers and displays. This chapter describes some of the engineering tools my colleagues and I are developing at Hewlett Packard Laboratories to help us evaluate how our customers perceive the image quality of our products. The engineering tools we use to evaluate image quality can be grouped into three categories: device simulation, subjective evaluation and distortion metrics. Simulation tools enable us to test our understanding of devices, predict their output, and optimize their design. We use software simulators for image capture devices, such as scanners and digital cameras, and rendering devices, such as displays and printers, to determine how adjustments in device parameters affect subjective impressions of image quality. Simulators also enable us to investigate regions of design space that are difficult to build and prototype. In this chapter I briefly review the assumptions underlying our device simulations and give an example of how device simulation enables us to optimize the image quality of H P inkjet and electrophotographic printers. Since our customers are the final arbiter of image quality, we consider their subjective image quality judgements to be key to the success of our imaging product. We