Optical system, image projection apparatus, and imaging apparatus

An optical system having a reduction conjugate point on a reduction side and a magnification conjugate point on a magnification side, the optical system comprising:

• a base optical system having a plurality of lenses rotationally symmetric with respect to an optical axis and an aperture stop;
• and
• an attachment optical system disposed closer to a magnification side than the base optical system, including a reflection surface group, wherein
• in a case where the attachment optical system is a first attachment optical system including a first reflection surface group, and having a first optical characteristic, a vertical distance from the optical axis to the magnification conjugate point in a vertical direction to the magnification conjugate point perpendicular to the optical axis is set to a first shift amount, and
• in a case where the attachment optical system is a second attachment optical system including a second reflection surface group, and having a second optical characteristic different from the first optical characteristic, the vertical distance is set to a second shift amount different from the first shift amount.

An optical system having a reduction conjugate point on a reduction side and a magnification conjugate point on a magnification side, the optical system comprising:

• a base optical system having a plurality of lenses rotationally symmetric with respect to an optical axis and an aperture stop, wherein
• the base optical system is configured to allow either a first attachment optical system or a second optical system to be attached at a position closer to a magnification side than the base optical system,
• the first attachment optical system includes a first reflection surface group, and has a first optical characteristic,
• the second attachment optical system includes a second reflection surface group, and has a second optical characteristic different from the first optical characteristic,
• in a case where the first attachment optical system is attached to the base optical system, a vertical distance from the optical axis to the magnification conjugate point in a vertical direction to the magnification conjugate point perpendicular to the optical axis is set to a first shift amount, and
• in a case where the second attachment optical system is attached to the base optical system, the vertical distance is set to a second shift amount different from the first shift amount.