Abstract: A pattern is formed on an optical device, where the optical device includes a plurality of pixel elements. Each pixel element has a stack of layers that includes a colour control layer and a brightness control layer superposed over each other. For each of one or more of the pixel elements: energy is deposited into the colour control layer to change an effect of the colour control layer on the colour of light, and energy is deposited into the brightness control layer to change an effect of the brightness control layer on the intensity of light.

Abstract: Display apparatuses are disclosed. In one arrangement, a display apparatus comprises a plurality of pixel units. Each pixel unit comprises: an optically switchable element; a heater operable to apply heating to the optically switchable element and thereby change an optical property of the optically switchable element; and a drive unit for driving the heater in response to a drive signal. The drive unit is provided within a first layer. The optically switchable elements and heaters of the plurality of pixel units are separated from the first layer by at least a portion of a second layer. An average thermal conductivity of the second layer is lower than an average thermal conductivity of the first layer.