Optical system for a LED signal and wayside LED signal
An optical system ( 100 ) for a light emitting diode (LED) signal includes a plurality of light emitting diodes (LEDs) ( 12, 14 ), a plurality of optical lenses ( 20, 40, 60, 80 ) for diverging and collimating light generated by the plurality of LEDs ( 12, 14 ), wherein the plurality of LEDs ( 12, 14 ) and the plurality of optical lenses ( 20, 40, 60, 80 ) are sequentially arranged in an axial direction, and wherein the plurality of optical lenses ( 20, 40, 60, 80 ) are configured such that by altering an axial position of one of the optical lenses ( 20, 40, 60, 80 ) from a first defined axial position to a second defined axial position, a final angular light distribution of the optical system ( 100 ) is variable.
1. An optical system for a light emitting diode (LED) signal comprising:
a plurality of light emitting diodes (LEDs),
a plurality of optical lenses for diverging and collimating light generated by the plurality of LEDs, wherein the plurality of optical lenses comprises a first lens, a second lens, a third lens and a fourth lens,
wherein the plurality of LEDs and the plurality of optical lenses are sequentially arranged in an axial direction, and
wherein the plurality of optical lenses are configured such that by altering an axial position of one of the optical lenses from a first defined axial position to a second defined axial position, a final angular light distribution of the optical system is variable,
wherein the fourth lens collimates the light and provides the final angular light distribution,
wherein the fourth lens comprises an array of multiple identical convex lenslets, each lenslet comprising a curved surface oriented towards the plurality of LEDs and a flat surface oriented towards an output of the fourth lens.
2. The optical system as claimed in claim 1 ,
wherein the first defined axial position corresponds to a first final angular light distribution of the optical system, the first final angular light distribution corresponding to a short range (SR) application of a LED signal.
3. The optical system as claimed in claim 1 ,
wherein the second defined axial position corresponds to a second final angular light distribution which is different from the first final angular light distribution, the second final angular light distribution corresponding to a long range (LR) application of a LED signal.
4. The optical system as claimed in claim 1 ,
wherein the first lens is positioned after the plurality of LEDs in an axial direction, the first lens collimating light generated by the plurality of LEDs.
5. The optical system as claimed in claim 4 ,
wherein the first lens comprises an assembly of individual lenses, a number of the individual lenses corresponding to a number of the plurality of LEDs.
6. The optical system as claimed in claim 1 ,
wherein the second lens is positioned after the first lens in the axial direction, the second lens diverging the light with an essential homogenous illuminance.
7. The optical system as claimed in claim 6 ,
wherein the second lens is configured as a doubled sided aspheric lens.
8. The optical system as claimed in claim 1 ,
wherein the third lens is positioned after the second lens in the axial direction, the third lens collimating the light.
9. The optical system as claimed in claim 8 ,
wherein an axial position of the third lens is alterable from a first defined axial position to a second defined axial position, thereby varying the final angular light distribution of the optical system.
10. The optical system as claimed in claim 8 ,
wherein the third lens is configured as Fresnel lens.
11. The optical system as claimed in claim 1 ,
wherein the multiple identical lenslets each comprise a cutout.
12. The optical system as claimed in claim 1 ,
wherein the fourth lens comprises an array of identical first lenslets or second lenslets for providing the first or second final angular light distributions of the optical system.
13. The optical system as claimed in claim 12 ,
wherein the first lenslets or the second lenslets are arranged on a plate such that interspaces are provided between the individual first lenslets or second lenslets.
14. The optical system as claimed in claim 1 ,
wherein the plurality of LEDs, the first lens and the second lens are mounted to a common printed circuit board.
15. A wayside LED signal comprising:
a plurality of light emitting diodes (LEDs);
a plurality of optical lenses for diverging and collimating light generated by the plurality of LEDs, wherein the plurality of optical lenses comprises a first lens, a second lens, a third lens and a fourth lens,
wherein the plurality of LEDs and the plurality of optical lenses are sequentially arranged in an axial direction, and
wherein the plurality of optical lenses are configured such that by altering an axial position of one of the optical lenses from a first defined axial position to a second defined axial position, a final angular light distribution of the optical system is variable,
wherein the fourth lens collimates the light and provides the final angular light distribution,
wherein the fourth lens comprises an array of multiple identical convex lenslets, each lenslet comprising a curved surface oriented towards the plurality of LEDs and a flat surface oriented towards an output of the fourth lens.
16. The wayside LED signal as claimed in claim 15 , wherein the plurality of LEDs and at least one of the plurality of optical lenses are mounted to a common printed circuit board.
17. The wayside LED signal as claimed in claim 15 , wherein at least one of the plurality of optical lenses is interchangeably mounted to the LED signal.
18. The wayside LED signal as claimed in claim 15 , wherein at least one of the plurality of optical lenses comprises an array of identical first lenslets or second lenslets for providing the final angular light distributions of the optical system.