Indicator lamps

Claim 1

An indicator lamp comprising: (a) tubular housing means having an open end and a closed end; (b) an LED light source disposed within said tubular housing means at a position remote from said open end thereof; (c) diffusing screen means disposed within said tubular housing immediately in front of said light source and remote from said open end of said tubular housing means so as to restrict the lamp emission angle; (d) a transparent lens of neutral density glass disposed in front of said open end of the tubular housing means and in a plane perpendicular to the longitudinal axis of the tubular housing means; (e) an infra-red suppressing, thin film interference filter formed on the side of said lens means closest to said light source; (f) the internal surface of said tubular housing means between the position of said light source and said open end being blackened in order to eliminate spurious internal reflection and to collimate the light emitted by the light source such that it is incident substantially normally at the infra-red filter; and (g) the lens having a transmission ratio which is less than 40% in order to attenuate ambient light which enters the front of the lens and is reflected out again by the infra-red light.