source near an input port of a radiation guide so that the radiation from the radiation source enters the input port and so that the radiation source is positionally adjustable toward and away from the input port parallel to the direction and supplying radiation through the radiation guide from the input port to an output port thereof application_number US 82372510 A description fig1 is a diagrammatic perspective view of an apparatus that is a polychromatic light emitting diode led light source assembly 10 embodying aspects of the invention fig2 is a diagrammatic sectional side view taken along line 2 2 in fig1 fig3 is a diagrammatic sectional top view taken along line 3 3 in fig1 fig4 is a diagrammatic perspective view of a radiation guide or light pipe 16 that is a component of the assembly 10 of fig1 with reference to fig2 and 4 the light pipe 16 includes a horizontally extending main tube 17 having four walls and a rectangular cross sectional shape the main tube 17 has a central opening with a rectangular cross sectional shape at one end of the main tube 17 the central opening serves as an outlet port 19 of the light pipe 16 the opposite end of the main tube 17 is closed by an inclined end wall 18 three spaced tubular chimneys 22 23 and 24 each extend upwardly from a top wall of the main tube 17 the chimneys 22 24 each have four walls arranged to form the frustrum of a four sided pyramid thus the chimneys 22 24 each have.