Common　projection　optics　use　Köhler　illumination　to　achieve　a　required　lighting.　These　systems　always　prevent　the　realization　of　a　compact　optical　configuration　along　with　a　high　lumen　output.　Based　on　conventional　Köhler　illumination,　a　modified　Köhler　illumination　system　for　LED-based　projection　display　is　presented　in　this　paper,　which　can　significantly　reduce　the　system　volume　while　allowing　for　adequate　and　homogeneous　illumination.　Equipped　with　the　proposed　system,　a　pocket-sized　CF-LCoS　projector　with　a　physical　dimension　of　27.4　mm　×　19.4　mm　×　9.6　mm　is　designed,　simulated　and　analyzed.　Compared　to　conventional　approaches,　this　design　could　offer　an　average　43%　volume　reduction　with　acceptable　tolerance.　To　the　best　of　our　knowledge,　the　screen　uniformity　of　90.2%　and　the　light　efficiency　of　56.5%　are　competitive　as　compared　with　those　of　the　currently　commercialized　pocket-sized　CF-LCoS　projectors.　©　2014　Elsevier　B.V.　All　rights　reserved.