Measurement optical system and photometric/colorimetric device

A measurement optical system comprising:

• in order from an object side,
• a first lens group including at least one lens and having a positive refractive power;
• a second lens group including at least one lens and having a positive refractive power;
• a first stop;
• and
• a third lens group including at least one lens and having a positive refractive power;
• wherein the measurement optical system further comprises a second stop disposed at least one of (i) in vicinity of a position of a focal point of the first lens group on an image side and (ii) in vicinity of a position conjugate with the focal point of the first lens group on the image side with respect to the second lens group and the third lens group, and
• wherein an absolute value of a lateral magnification of the first stop to a plane conjugate with the first stop with respect to the first lens group and the second lens group is 0.7 or less.