Imaging optical system for forming high-definition image and image projection apparatus having the same

An image projection apparatus comprising:

• an image display element configured to form an original image;
• and
• an imaging optical system,
• wherein the imaging optical system includes, in order from an enlargement conjugate side to a reduction conjugate side, a first lens unit having a negative refractive power configured not to move for zooming from a wide-angle end to a telephoto end, and a plurality of lens units configured to move so that a space between lens units adjacent to each other changes during the zooming,
• wherein the first lens unit includes, in order from the enlargement conjugate side to the reduction conjugate side, a first lens subunit having a negative refractive power, a second lens subunit having a negative refractive power, and a third lens subunit having a positive refractive power,
• wherein the first lens subunit is configured not to move for focusing from an infinity to a close range,
• wherein both the second lens subunit and the third lens subunit are configured to move, during the focusing from the infinity to the close range, from the enlargement conjugate side to the reduction conjugate side while a space between the second lens subunit and the third lens subunit is narrowed, and
• wherein the imaging optical system is configured to project the original image formed by the image display element.