| 摘要 |
<p>An infra-red sensing device (10) has a glass panel (22) transparent to infra-red radiation, an infra-red radiation source (18) at one side of the element for directing infra-red radiation on a path through the panel (22) and an infra-red detector (20) at said one side, positioned to detect infra-red radiation passing from the infra-red radiation source (18) through the panel (22) and reflected by an object at the other side of the panel (22) back through the panel (22) to the infra-red detector (20). The infra-red radiation source (18) and the infra-red detector (20) are arranged such that there is defined a sensing volume (24) within which an object must be positioned to enable detection of infra-red radiation by the infra-red detector (20). The detection zone is positioned at the other side of the panel (22) but so as to be at least predominately away from a surface of the panel (22) at the opposite side of the panel (22) from the infra-red detector (20).</p> |
