Quality of service scheduling scheme for a broadband wireless access system

摘要

A portable optical magnifying device (1), for observing specimens within a specimen-vessel having a transparent flat wall, comprises an eyepiece (4) and an objective (3), a light-path being defined therebetween. The device (1) includes a spacer (7) arranged at least partly around the objective (3) and which is adapted in use to seat the device (1) against the flat wall of the specimen vessel with the objective (3) closely adjacent but spaced therefrom, and with its optical axis normal thereto. The device (1) further includes means (9) for releasably attaching the device (1) to the flat wall, with the space (7) bearing against the flat wall of the specimen vessel. Attachment is achieved by evacuation of the space between objective lens, spacer and flat wall.