Imaging optical system, image projection apparatus using the same, and image projection system

An image projection apparatus comprising:

• a holding part configured to hold an imaging optical system;
• a light source;
• an optical modulator;
• and
• a light guide optical system configured to guide light from the light source to the optical modulator and to guide light from the optical modulator to the imaging optical system,
• wherein the imaging optical system includes a plurality of lens units including
• a first lens unit having negative refractive power,
• a second lens unit having positive refractive power,
• a third lens unit having negative refractive power,
• a fourth lens unit,
• a fifth lens unit,
• a sixth lens unit, and
• a seventh lens unit which are sequentially arranged from an enlargement conjugate side toward a reduction conjugate side,
• the lens units are configured such that an interval between adjacent lens units changes during zooming from a wide-angle end toward a telephoto end,
• the first lens unit includes at least one negative lens, and at least one positive lens arranged closer to the reduction conjugate side than the at least one negative lens,
• the third lens unit is movable from the enlargement conjugate side toward the reduction conjugate side for the zooming, and
• meets the following equation assuming a refractive index of a lens included in the third lens unit at nb3n:
• 1.72≤nb3n≤1.95.

An image projection apparatus comprising:

• an imaging optical system;
• a light source;
• an optical modulator;
• and
• a light guide optical system configured to guide light from the light source to the optical modulator and to guide light from the optical modulator to the imaging optical system,
• wherein the imaging optical system includes a plurality of lens units including
• a first lens unit having negative refractive power,
• a second lens unit having positive refractive power,
• a third lens unit having negative refractive power,
• a fourth lens unit,
• a fifth lens unit,
• a sixth lens unit, and
• a seventh lens unit which are sequentially arranged from an enlargement conjugate side toward a reduction conjugate side,
• the lens units are configured such that an interval between adjacent lens units changes during zooming from a wide-angle end toward a telephoto end,
• the first lens unit includes at least one negative lens, and at least one positive lens arranged closer to the reduction conjugate side than the at least one negative lens,
• the third lens unit is movable from the enlargement conjugate side toward the reduction conjugate side for the zooming, and
• meets the following equation assuming a refractive index of a lens included in the third lens unit at nb3n:
• 1.72≤nb3n≤1.95.

An image projection system comprising:

• an image projection apparatus;
• and
• a control part configured to control the image projection apparatus,
• wherein the image projection apparatus includes
• an imaging optical system,
• a light source,
• an optical modulator, and
• a light guide optical system configured to guide light from the light source to the optical modulator and to guide light from the optical modulator to the imaging optical system,
• the imaging optical system includes a plurality of lens units including
• a first lens unit having negative refractive power,
• a second lens unit having positive refractive power,
• a third lens unit having negative refractive power,
• a fourth lens unit,
• a fifth lens unit,
• a sixth lens unit, and
• a seventh lens unit which are sequentially arranged from an enlargement conjugate side toward a reduction conjugate side,
• the lens units are configured such that an interval between adjacent lens units changes during zooming from a wide-angle end toward a telephoto end,
• the first lens unit includes at least one negative lens, and at least one positive lens arranged closer to the reduction conjugate side than the at least one negative lens,
• the third lens unit is movable from the enlargement conjugate side toward the reduction conjugate side for the zooming, and
• meets the following equation assuming a refractive index of a lens included in the third lens unit at nb3n:
• 1.72≤nb3n≤1.95.