Optical system having refracting surface and reflecting surface, and image capturing apparatus and projection apparatus including the same

An optical system comprising:

• a first optical element including a first reflecting region having a convex shape toward an enlargement side;
• a second optical element having a reduction-side surface having a convex shape toward the enlargement side;
• and
• a third optical element having an enlargement-side surface having a convex shape toward the enlargement side,
• wherein the reduction-side surface of the second optical element or the enlargement-side surface of the third optical element includes a second reflecting region,
• wherein the third optical element includes a refracting region having positive power,
• wherein light from the enlargement side proceeds to a reduction side sequentially via a refracting region of the first optical element, the second reflecting region, the first reflecting region, a refracting region of the second optical element, and the refracting region of the third optical element, and
• wherein the following conditional expression is satisfied:
• 2.0≤R1/L1≤5.5
• where a radius of curvature of a closest refracting surface, that is closest to the first optical element among refracting surfaces located on the reduction side of the first optical element, is R1, and a distance between the closest refracting surface and an optical surface including the second reflecting region is L1.

An optical system comprising:

• a first optical element including a first reflecting region having a convex shape toward an enlargement side;
• a second optical element having a reduction-side surface having a convex shape toward the enlargement side;
• and
• a third optical element having an enlargement-side surface having a convex shape toward the enlargement side
• wherein the reduction-side surface of the second optical element or the enlargement-side surface of the third optical element includes a second reflecting region,
• wherein the third optical element includes a refracting region having positive power,
• wherein light from the enlargement side proceeds to a reduction side sequentially via a refracting region of the first optical element, the second reflecting region, the first reflecting region, a refracting region of the second optical element, and the refracting region of the third optical element,
• wherein the second reflecting region includes a reflecting portion configured to reflect a part of the light, and a light-blocking portion configured to block a part of the light, and
• wherein a diameter of the reflecting portion in a first direction perpendicular to an optical axis is larger than a diameter of the reflecting portion in a second direction perpendicular to the optical axis and the first direction, and the first reflecting region is located on one side with respect to the optical axis in the second direction.