A Zoom Lens Design MethodDave Shafer1)Start with the simplest possible monochromatic design,usinglow-order aspherics and appropriate vignetting2)Optimize until pretty good performance is reached3)Replace aspheric lenses,one at a time,with spherical doublets4)Achromatize moving groups,then achromatize fixed lenses5)Complete optimizationFocal length8 mm-30 mm (minimumrange)Sensor2/3“HDF-number 2.8,constant over the zoom rangeZoom designMechanical constraintsoverall length 160 mmexample specsback focal distance 20 mmnumber of zoom movements:2WavelengthVISDistortion<3%Polychromatic MTF at 40 LP/mm >75%on-axisLet's look atRelative illumination 5.5 mm >35%some relevantFocus RangeInfinity to 250 mm with separate focusinggroupdesignsCompact ZoomExample 3:n p n pDesignedby Zeiss45.450MPositions:1-3sca1e:0.55Dodoc,'Toward the global optimum in zoom lens design',SPIE 8488Disadvantage:Very large variator group (green),3 movements