A light diffusion sheet usable, for example, in backlight units, includes a transparent substrate layer, and a light diffusion layer overlaid on a front face of the substrate layer. The control scheme and system utilizes sensory information measured local to the prosthesis to automatically adjust stance and swing phase knee resistances to a particular wearer under a wide variety of locomotory activities. Preferably, the backlight is an OLED device and the 2D3D mode switching is achieved by selectively energising all or a subset of parallel control electrodes of the OLED device.