Abstract: Packaging for a can containing ground roasted coffee packed under atmospheric pressure and having a flexible peel-off lid which is vented to allow the escape of a buildup of carbon dioxide gases. A spacing structure prevents the vent valve in the lid from being closed by contact with the plastic overcap. The spacing structure may include bosses on the overcap which engage the vent valve or a pocket in the overcap which allows the flexible lid to reach a maximum height without engaging the overcap. A permanently opened passageway may be provided between the plastic overcap and the rim of the can to further facilitate the escape of carbon dioxide.

Abstract: An optical waveguide (1) has a grating structure (2) in which gratings of different orders are superimposed. When first and second order gratings are superimposed, input light is partially reflected by the first order component and partially coupled out of the waveguide by the second order component. The second order component can also be used to couple external light into the waveguide (1). The grating structure (2) has applications to free space couplers, optical sensors, and suppression of ripples in dispersion compensators.