Chapter 1
Nonimaging optical systems and
their uses
Irfan Ullah
Department of Information and Communication Engineering
Myongji university, Yongin, South Korea
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Introduction
 Image-forming system
 Capable of being used for imaging
 Nonimaging system
 Do not attempt to form an image of the source.
not spherical
surfaces
Nonimaging collectors
 Equilibirium temperature T of black body
T = 364°K or 90.85°C
• σ is the Stefan Boltzmann constant, 5.67 × 10-8Wm-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 cont’d..
 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
Concentration ratio
 Concentration ratio
• A plane entrance aperture of area
• A' plane exit aperture of area
 Concentration ratio of a linear concentrator
Is there any limit to the value of C?
Output dimensions
Perpendicular to the line
Concentration ratio cont’d..
 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
Source at infinity
Concentration ratio cont’d..
 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
Uses of concentrators
 Photomultipliers
 These detectors multiply the current produced by incident light by as
much as 100 million times
 Limited in size and volume (1 m3)
 Optics of visual receptors (retina)
Photomultiplier
Principle of Photomultiplier
Human eye
Uses of illuminators
 Filament
 Light emitting diode (LED)
 Emitting light into wide angular spread
 Problem: efficiently collimate to emit in a certain angular emitted region
Compact fluorescent lamp
LED with reflector
LED