Provided is a projection lens, including: a plurality of moving lens units that move on an optical axis for zooming; and a plurality of plastic lenses containing plastic, in which when a focal distance of an i-th positive lens from a predetermined plane side of N positive lenses of the plurality of plastic lenses is given by fpi, a focal distance of a j-th negative lens from the predetermined plane side of M negative lenses of the plurality of plastic lenses is given by fnj, and fp and fn are defined by.times. ##EQU00001## .times. ##EQU00001.2## (N and M each are a natural number, that is, an integer equal to or larger than 1), -0.56

 
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> Focus detecting apparatus

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