Optical system for projection and projection-type display apparatus

An optical system for projection that is telecentric on a reduction side,

• wherein a correction lens group substantially consisting of a part of lens groups in the optical system for projection is configured to move in the direction of an optical axis to correct a shift in a focal position caused by a change in temperature, and
• wherein the following conditional formulas (1), (2) and (3) are satisfied:
• 0.5<|ΔBf/(fw/100)|<5.0 (1);
• and
• |(ΔAt×fw)/(ΔBf×Imφ)|<0.12 (2);
• |D/fpr|<0.50 (3),
• where
• ΔBf:
• a movement amount of a reduction-side focal position when the correction lens group has been moved by fw/100,
• fw:
• a focal length of an entire system,
• ΔAt:
• a variation amount of a tangential component of astigmatism at a maximum angle of view when the correction lens group has been moved by fw/100,
• Imφ:
• the diameter of a maximum effective image circle on the reduction side,
• D:
• a distance on the optical axis from a magnification-side focal position of a combined optical system of the correction lens group through a most reduction-side lens in the entire system to a most magnification-side lens surface in the correction lens group, and
• fpr:
• a focal length of the combined optical system of the correction lens group through the most reduction-side lens in the entire system, and
• wherein ΔBf, fw, ΔAt, D and fpr are values at a wide angle end when the optical system for projection is a variable magnification optical system.