Optical characterization of curved displays

Among the new display trends of the past few years, so-called curved displays have been particularly successful. Their curvature opens up a multitude of new possibilities in terms of design and application. Whether an instrument panel is perceived as pleasant, is still legible in sunlight or switches fast enough in cold winter temperatures, are parameters for individual assessment. A further quality factor is the stability of the perceived image content. For example, it is perceived as unpleasant when contrast and color change with the direction of viewing.

The 7-axis goniometer (DMS 904) expands the DMS series portfolio of goniometers to include a display measurement system that is specially geared to the above measurement tasks. Its generously dimensioned interior has space for displays with a length of up to 1.8m. The measuring head, equipped with a measuring microscope, coupled to a spectrometer and/or a photometer for angle-dependent measurements can be moved along a 1.5m long axis in X-direction. Movement in Z-direction of the display takes place over an XYZ measuring table on which the display is mounted. By combining the two axes, the curved shape of the display can be traversed while maintaining the same distance between the measuring microscope and display measurement plane. This enables all measurements necessary for the characterization of a display (switching times, EOC, flicker, angular scans, reflection measurements) to be taken at any given point along the longitudinal axis on the display.

A further challenge is the characterization of long, curved displays with the above XZ movement concept under temperature. For this purpose, a new temperature chamber (HCS-7) was developed that ensures display temperature control between -40°C and +105°C and permits an additional XZ movement. Display with a length of up to 1.6m can be fit in the new chamber.