Chapter 1 Nonimaging optical systems and their uses Irfan Ullah Department of Information and Communication Engineering Myongji university, Yongin, South Korea Copyright © solarlits.com

 Image-forming system  Capable of being used for imaging  Nonimaging system  Do not attempt to form an image of the source. Introduction not spherical surfaces

 Equilibirium temperature T of black body σ is the Stefan Boltzmann constant, 5.67 × Wm -2 °K -4 S is the radiation power density, approximately 1KWm -2  For generating electric power, increase S by a factor C  Focus the image of sun with an image forming system  How large a value of C is theoretically possible?  Can the theoretical maximum concentration be achieved in practice? Nonimaging collectors T = 364°K or 90.85°C

 Nonimaging (anidolic, meaning “without image”)  F-number N is given by f is the focal length D is the diameter of the entrance pupil (effective aperture)  Nonimaging concentrators are more efficient than image forming systems Nonimaging collectors cont’d..

 Concentration ratio A plane entrance aperture of area A' plane exit aperture of area  Concentration ratio of a linear concentrator Concentration ratio Output dimensions Perpendicular to the line Is there any limit to the value of C?

 Theoretical maximum concentration in a rotational concentrator is Condition: rays emerge at all angles up to π/2 from the normal to the exit face  For a linear concentrator Concentration ratio cont’d.. Source at infinity

 Can actual concentrators be designed with the theoretically best performance?  Can all reflecting surfaces have 100% reflectivity?  Can all refracting surfaces have perfectly antireflective coating?  Can all shapes be made exactly right?  Yes, 2D concentrators can be designed.  Also 3D concentrators, if consider refractive index or infinity thin surfaces properly  And also rotational symmetric concentrators.  Other approach is to use complex design, or by using materials which are not possible in practice Concentration ratio cont’d..

 Photomultipliers  These detectors multiply the current produced by incident light by as much as 100 million times  Limited in size and volume (1 m 3 )  Optics of visual receptors (retina) Uses of concentrators PhotomultiplierPrinciple of PhotomultiplierHuman eye

 Filament  Light emitting diode (LED)  Emitting light into wide angular spread  Problem: efficiently collimate to emit in a certain angular emitted region Uses of illuminators Compact fluorescent lamp LED LED with reflector