Imaging optical system, image projection apparatus, and imaging apparatus
AssigneeCanon Kabushiki Kaisha
InventorMakoto Takahashi
Life of this patent
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Abstract
An imaging optical system includes, in order from an enlargement conjugate side, a front unit, a diaphragm, and a rear unit. The front unit includes, in order from the enlargement conjugate side, a first lens having a negative refracting power, a second lens having at least one aspherical surface and a meniscus shape with a negative refracting power, and a third lens having an aspherical surface on the enlargement conjugate side and a negative refractive power. The second lens has a positive refractive power at a periphery, and a surface in which the periphery and a center have curvatures with different signs. The third lens has a concave surface on the enlargement conjugate side. A predetermined condition is satisfied.
Claims8
An imaging optical system comprising;
- in order from an enlargement conjugate side,
- a front unit;
- a diaphragm;
- and
- a rear unit,
- wherein the front unit includes, in order from the enlargement conjugate side, a first lens having a negative refracting power, a second lens having at least one aspherical surface and a meniscus shape with a negative refracting power, and a third lens having an aspherical concave surface on the enlargement conjugate side and a negative refractive power,
- wherein the second lens has a positive refractive power at a periphery, and a surface in which the periphery and a center have curvatures with different signs each other, and
- wherein the following conditional expression is satisfied:
- 0.5r≤rk≤0.75r
- where rk is a distance from an optical axis to a position corresponding to an arbitrary extreme value on the surface of the second lens in which the periphery and a center have curvatures with different signs each other, in a direction orthogonal to the optical axis, and r is a lens radius.
An image projection apparatus comprising an imaging optical system, an image display element, and a light guiding optical system for guiding light from the image display element to the imaging optical system,
- wherein the imaging optical system includes, in order from an enlargement conjugate side, a front unit, a diaphragm, and a rear unit,
- wherein the front unit includes, in order from the enlargement conjugate side, a first lens having a negative refracting power, a second lens having at least one aspherical surface and a meniscus shape with a negative refracting power, and a third lens having an aspherical concave surface on the enlargement conjugate side and a negative refractive power,
- wherein the second lens has a positive refractive power at a periphery, and a surface in which the periphery and a center have curvatures with different signs each other, and
- wherein the following conditional expression is satisfied:
- 0.5r≤rk≤0.75r
- where rk is a distance from an optical axis to a position corresponding to an arbitrary extreme value on the surface of the second lens in which the periphery and a center have curvatures with different signs each other, in a direction orthogonal to the optical axis, and r is a lens radius.
An imaging apparatus comprising:
- an imaging optical system;
- and
- an image sensor configured to receive light formed by the imaging optical system,
- wherein the imaging optical system includes, in order from an enlargement conjugate side, a front unit, a diaphragm, and a rear unit,
- wherein the front unit includes, in order from the enlargement conjugate side, a first lens having a negative refracting power, a second lens having at least one aspherical surface and a meniscus shape with a negative refracting power, and a third lens having an aspherical concave surface on the enlargement conjugate side and a negative refractive power,
- wherein the second lens has a positive refractive power at a periphery, and a surface in which the periphery and a center have curvatures with different signs each other, and
- wherein the following conditional expression is satisfied:
- 0.5r≤rk≤0.75r
- where rk is a distance from an optical axis to a position corresponding to an arbitrary extreme value on the surface of the second lens in which the periphery and a center have curvatures with different signs each other, in a direction orthogonal to the optical axis, and r is a lens radius.
Dependencies are inferred from the claim text.