Optical system for facilitating plant growth

Abstract

Optical system for facilitating plant growth is provided. The optical system can produce a light beam having a full width at half-maximum (FWHM) angle of greater than 120 degrees in one or more transverse directions, wherein the transverse direction is perpendicular to the optical axis of the light beam.

What is claimed is: 
     
         1 . An optical system for facilitating plant growth, the optical system comprising:
 one or more light sources operable to produce a light beam having a full width at half-maximum (FWHM) angle of at least one hundred twenty degrees (120°) in a first transverse direction and a FWHM angle of less than one hundred twenty degrees (120°) in a second transverse direction substantially perpendicular to the first transverse direction.   
     
     
         2 . The optical system of  claim 1 , wherein the FWHM angle is between one hundred twenty degrees (120°) and one hundred sixty degrees (160°) in the first transverse direction. 
     
     
         3 . The optical system of  claim 1 , wherein the one or more light sources are operable to illuminate one or more plants in a lateral direction, with the first transverse direction along one or more lateral sides of the one or more plants. 
     
     
         4 . The optical system of  claim 3 , wherein the one or more light sources are operable to illuminate the one or more plants obliquely vertically, with an angle between an optical axis and a horizontal plane being greater than ten degrees (10°). 
     
     
         5 . The optical system of  claim 1 , wherein an optical power density in a light spot illuminated by the light beam on a projection surface at a distance from the one or more light sources is substantially uniform. 
     
     
         6 . The optical system of  claim 5 , wherein the projection surface is a surface of a conical body or a plane. 
     
     
         7 . The optical system of  claim 1 , wherein an average optical power density in an intermediate region in a light spot illuminated by the one or more light sources is equal to or less than average optical power density in a first region, wherein the first region is an annular region surrounding the intermediate region in the light spot. 
     
     
         8 . The optical system of  claim 7 , wherein in the first transverse direction and/or the second transverse direction, the light intensity of light increases from the optical axis to the periphery. 
     
     
         9 . The optical system of  claim 8 , wherein in the first transverse direction and/or the second transverse direction, light intensity distribution of the light beam I(θ) is substantially equal to I 0 /cos 3 (θ), where I 0  is the light intensity of the light at the optical axis and I (θ) is the light intensity of the light beam having an angle θ relative to the optical axis. 
     
     
         10 . The optical system of  claim 8 , wherein average optical power density in the intermediate region is a global minimum in the light spot. 
     
     
         11 . The optical system of  claim 1 , wherein a light spot illuminated by the light beam on a projection plane comprises two or more illuminated areas, wherein each of the two or more illuminated areas illuminate one plant. 
     
     
         12 . The optical system of  claim 11 , wherein a light intensity distribution for each of the two or more illuminated areas has a trough and two crests located on opposing sides of the trough in at least one transverse direction, wherein the trough is located at a longitudinal direction having an angle θ with respect to the optical axis. 
     
     
         13 . The optical system of  claim 12 , wherein one crest of the two crests is located at a longitudinal direction having an angle α of about seventy-five degrees with respect to an optical axis, and the other crest of the two crests is located at a longitudinal direction having an angle β of about fifteen degrees with respect to the optical axis. 
     
     
         14 . The optical system of  claim 13 , wherein an average optical power density in a gap area between two adjacent illuminated areas is less than a minimum optical power density in the illuminated areas. 
     
     
         15 . The optical system of  claim 1 , wherein the one or more light sources includes a first LED array and a second LED array, an optical axis of the first LED array and an optical axis of the second LED array are in different directions. 
     
     
         16 . The optical system of  claim 15 , wherein the optical axis of the first LED array and the optical axis of the second LED array form an angle between twenty degrees (20°) and one hundred twenty degrees (120°). 
     
     
         17 . The optical system of  claim 15 , wherein the optical axis of the first LED array and the optical axis of the second LED array form an angle γ relative to the optical axis of the one or more light sources. 
     
     
         18 . The optical system of  claim 17 , wherein the angle γ ranges from ten degrees (10°) to sixty degrees (60°). 
     
     
         19 . The optical system of  claim 1 , wherein the light beam has spectra including blue wavelengths and red wavelengths. 
     
     
         20 . The optical system of  claim 1 , wherein the one or more light sources comprises at least one light source of the one or more light sources operable to emit a light beam having different wavelengths, and the at least one light source operable to emit a light beam having different wavelengths are controllable individually.