Patent attributes
A skew mirror is an optical reflective device, such as a volume holographic optical element, whose reflective axis forms an angle (the skew angle) with the surface normal. A skew illuminator is a skew mirror that expands a narrow beam into a wide beam without changing the angular bandwidth of the illumination. Because the skew angle can form a relatively large angle with the surface normal (e.g., about 45), a skew illuminator can be fairly compact, making it suitable for directing light onto a spatial light modulator (SLM) in a small package. In some cases, the skew illuminator is formed as a waveguide, with a holographic layer sandwiched between a pair of substrates. A grating structure in the holographic core diffracts light out of the waveguide and, e.g., onto the active area of an SLM, which modulates the incident light and either transmits it or reflects it back through the waveguided skew illuminator.
