Figure 1

Speckle reduction characteristics of a chiral nematic LC device (E7 + 2.5 wt% BDH1281, pitch 517 nm) when subjected to different amplitudes of a square-wave electric field at a frequency of 40 Hz (a) Optical polarising microscope images of the LC device (the 20 μm-diameter spacer beads can be seen in all images, although they are most obvious for the image recorded at E = 10 Vµm⁻¹). Scale bars are 500 µm. (b) Corresponding images of the speckle pattern formed on a white screen after the beam from a He–Ne laser has passed through the LC device. The same electric field is applied as those used in (a). Images were captured by the CCD camera with a 50 ms exposure time and normalized by the average intensity. (c) Plots of the intensity distribution of the central line of pixels across the width of each image of the speckle pattern presented in (b). All measurements were carried out at 25 °C using a 20 µm-thick device.