Abstract: Undesirable light leakage is reduced in a mixed-reality head-mounted display device using an out-coupling diffractive optical element in a waveguide combiner that is implemented using a surface relief grating (SRG) having a gradient refractive index. The SRG has gratings with modulated depth in which shallower gratings have a lower refractive index and deeper gratings have a higher refractive index. The lower efficiency of the shallower gratings reduces forward-propagating virtual image light leaking into the real-world environment of the HMD device while simultaneously enabling light to propagate to the deeper gratings to thereby improve virtual image uniformity over the entirety of eyebox of the combiner.

Abstract: The invention relates to an arrangement in an apparatus for analyzing, on the basis of radiation absorption properties, one or more gas component included in a gaseous medium from an origin, like exhaled air from a person. The apparatus comprises a radiation source (10); a measuring chamber (8) provided with radiation transmissive windows (7a, 7b) for receiving a gas mixture (6) from at least the gaseous medium (G1); a first detector (1), which receives the radiation passed through the gas mixture; and between the radiation source and the detector a first optical interference filter (3), which has a first radiation transmission wavelength band and which is tiltable (P) relative to the passing radiation (R) beam.