Characterizing the reflectivity of handheld display devices

Area of Science:

• Medical Physics
• Display Technology
• Image Quality Assessment

Background:

• Increasing use of handheld and tablet devices for medical image viewing necessitates standardized reflectivity measurement methods.
• Current methods, like the American Association of Physicists in Medicine Task Group 18 (TG18), may not adequately address the unique characteristics of smaller display devices.

Purpose of the Study:

• To characterize diffuse reflections for handheld display devices (mobile phones, tablets) using modified TG18 methods.
• To assess the impact of back surface conditions and masking on diffuse reflectance coefficient measurements.

Main Methods:

• Modified the TG18 diffuse reflectance coefficient measurement protocol.
• Measured seven handheld devices and three workstation displays, varying back panel conditions and mask sizes.
• Recorded illuminance and reflected luminance to calculate diffuse reflectance coefficients.

Main Results:

• Diffuse reflectance coefficients for handhelds were lower without a back panel and increased as mask size decreased.
• Workstation displays showed higher coefficients without masks compared to masked conditions.
• Both luminance and illuminance increased with decreasing mask size, but not proportionally.

Conclusions:

• The TG18 method is sensitive to illumination conditions and back panel variations, especially for smaller handheld displays.
• Diffuse reflection coefficients can vary significantly (up to 20%) based on mask size and back surface.
• The TG18 method requires refinement, including specifying the back panel, for consistent medical display comparisons across device types.