A display unit has first and second substrates, a liquid crystal display, an organic electroluminescent display, a reflector and a plurality of common electrodes. The apparatus reduces shield-to-shield spacing. Such measurements may provide a background andor sensitivity measurement for use in processing sensor data and may be used to trigger events such as digital filtering of data or suspending display of data. The column slats are formed from U-shaped column strips configured such that a left side of the U-shape forms a left-hand side of each array element in a column and a right side of the U forms an opposing right-hand side.