Light guide

A light guide system comprising a light guide and a collimating lens for collimating light coming from the light guide, the light guide comprising a transparent element made of transparent material having refractive index greater than unity and the transparent element comprising:

• a first end comprising a place for a light source,
• a second end opposite the first end,
• an outer surface between the first and second ends, and
• an interior channel free from the transparent material and extending from the first end to the second end,
• wherein the interior channel comprises a first portion beginning from the first end and a second portion extending to the second end, the first portion being shaped to guide at least part of light falling to a wall of the first portion into the transparent material and towards the outer surface, and the outer surface being shaped to provide total reflection for reflecting the at least part of the light towards the second end, and wherein the second portion is at least as long as the first portion, and the second portion is shaped so that:
• W/L≧W1/L1, when L≧L1,
• where L is a distance from the first end, W is a width of the interior channel at the distance L from the first end, L1 is a length of the first portion, and W1 is a width of the first portion at a distance of L1 from the first end, and
• wherein the wall of the first portion of the interior channel defines a truncated cone.

An illuminator device comprising at least one light guide and at least one light source, each light guide comprising a transparent element made of transparent material having refractive index greater than unity and the transparent element comprising:

• a first end comprising a place for the light source,
• a second end opposite the first end,
• an outer surface between the first and second ends, and
• an interior channel free from the transparent material and extending from the first end to the second end,
• wherein the interior channel comprises a first portion beginning from the first end and a second portion extending to the second end, the first portion being shaped to guide at least part of light falling to a wall of the first portion into the transparent material and towards the outer surface, and the outer surface being shaped to provide total reflection for reflecting the at least part of the light towards the second end, and wherein the second portion is at least as long as the first portion, and the second portion is shaped so that:
• W/L≧W1/L1, when L≧L1,
• where L is a distance from the first end, W is a width of the interior channel at the distance L from the first end, L1 is a length of the first portion, and W1 is a width of the first portion at a distance of L1 from the first end, and
• wherein the wall of the first portion of the interior channel defines a truncated cone.

A mold having a form suitable for manufacturing, by mold casting, a transparent element of a light guide, wherein the transparent element comprises:

• a first end comprising a place for a light source,
• a second end opposite the first end,
• an outer surface between the first and second ends, and
• an interior channel free from the transparent material and extending from the first end to the second end,
• wherein the interior channel comprises a first portion beginning from the first end and a second portion extending to the second end, the first portion being shaped to guide at least part of light falling to a wall of the first portion into the transparent material and towards the outer surface, and the outer surface being shaped to provide total reflection for reflecting the at least part of the light towards the second end, and wherein the second portion is at least as long as the first portion, and the second portion is shaped so that:
• W/L≧W1/L1, when L≧L1,
• where L is a distance from the first end, W is a width of the interior channel at the distance L from the first end, L1 is a length of the first portion, and W1 is a width of the first portion at a distance of L1 from the first end, and
• wherein the wall of the first portion of the interior channel defines a truncated cone.