US 12,748,290 B2Granted

Imaging optical system comprising three mirrors

AssigneeOffice National d'Etudes et de Recherches Aerospatiales

InventorsLouis Duveau, Guillaume Druart

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Abstract

An imaging optical system including three mirrors has a configuration adapted to block stray rays which could otherwise reach an image sensor of the system, while permitting large fields, high apertures, and good system compactness. The system may also incorporate two entrance baffles which are arranged one on either side of an optical entrance of the system. Functions of the two entrance baffles may be limited to intercepting rays originating from fields which are angularly distant from the entrance field useful to each captured image. The two entrance baffles can thus have reduced lengths upstream, so that the system has a small size.

Claims13

Dependent claims

An imaging optical system comprising three mirrors, including:

a primary mirror,
a secondary mirror, and
a tertiary mirror
which are adapted and arranged so that light rays originating from a scene located in an entrance field of the system are reflected first by the primary mirror, then by the secondary mirror, and then by the tertiary mirror, to form an image of the scene in a focal plane of the system,
a light ray which originates from the scene and which contributes to forming the image being thus divided into:
an initial segment upstream of the primary mirror,
a first intermediate ray segment between the primary mirror and the secondary mirror,
a second intermediate ray segment between the secondary mirror and the tertiary mirror, and
a terminal ray segment between the tertiary mirror and the focal plane,
and, in the imaging optical system:
the primary and secondary mirrors are oriented so that the second intermediate segment of a parabasal ray of the system intersects the initial segment of said parabasal ray, and
the secondary and tertiary mirrors are oriented so that the terminal segment of the parabasal ray is at least partially located at a lateral side of the secondary mirror which is opposite to another side of the secondary mirror on the side of which the primary mirror is located, so that the terminal segment of the parabasal ray does not intersect the first intermediate segment of said parabasal ray,
an image sensor arranged so that a photosensitive surface of said image sensor is superimposed on the focal plane, the photosensitive surface extending from an upstream boundary to a downstream boundary, the upstream and downstream boundaries of the photosensitive surface of the image sensor being defined in relation to respective projections of said upstream and downstream boundaries onto the initial segment of the parabasal ray and in relation to the direction of propagation of the parabasal ray in said initial segment of the parabasal ray,
an upstream boundary of the photosensitive surface being the point on the photosensitive surface located furthest along a direction opposite to the propagation direction of the initial segment of the parabasal ray,
an upstream edge of the primary mirror being the point on the primary mirror located furthest along the direction opposite to the propagation direction of the initial segment of the parabasal ray,
an upstream edge of the secondary mirror being the point on the secondary mirror located furthest along the direction opposite to the propagation direction of the initial segment of the parabasal ray,
the secondary and tertiary mirrors are oriented so that the upstream boundary of the photosensitive surface of the image sensor is offset along the propagation direction of the initial segment of the parabasal ray relative to a straight line which connects the upstream edge of the primary mirror to:
the upstream edge of the secondary mirror, or
an upstream edge of a screen which surrounds the secondary mirror, and
the upstream edge of the screen being the point on the screen located furthest along the direction opposite to the propagation direction of the initial segment of the parabasal ray
so that:
the secondary mirror or
the screen which surrounds said secondary mirror intercepts stray rays which would otherwise propagate in a straight line directly from the primary mirror to the photosensitive surface of the image sensor.

20 more elements

Dependencies are inferred from the claim text.

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Abstract

An imaging optical system comprising three mirrors, including:

a primary mirror,
a secondary mirror, and
a tertiary mirror
which are adapted and arranged so that light rays originating from a scene located in an entrance field of the system are reflected first by the primary mirror, then by the secondary mirror, and then by the tertiary mirror, to form an image of the scene in a focal plane of the system,
a light ray which originates from the scene and which contributes to forming the image being thus divided into:
an initial segment upstream of the primary mirror,
a first intermediate ray segment between the primary mirror and the secondary mirror,
a second intermediate ray segment between the secondary mirror and the tertiary mirror, and
a terminal ray segment between the tertiary mirror and the focal plane,
and, in the imaging optical system:
the primary and secondary mirrors are oriented so that the second intermediate segment of a parabasal ray of the system intersects the initial segment of said parabasal ray, and
the secondary and tertiary mirrors are oriented so that the terminal segment of the parabasal ray is at least partially located at a lateral side of the secondary mirror which is opposite to another side of the secondary mirror on the side of which the primary mirror is located, so that the terminal segment of the parabasal ray does not intersect the first intermediate segment of said parabasal ray,
an image sensor arranged so that a photosensitive surface of said image sensor is superimposed on the focal plane, the photosensitive surface extending from an upstream boundary to a downstream boundary, the upstream and downstream boundaries of the photosensitive surface of the image sensor being defined in relation to respective projections of said upstream and downstream boundaries onto the initial segment of the parabasal ray and in relation to the direction of propagation of the parabasal ray in said initial segment of the parabasal ray,
an upstream boundary of the photosensitive surface being the point on the photosensitive surface located furthest along a direction opposite to the propagation direction of the initial segment of the parabasal ray,
an upstream edge of the primary mirror being the point on the primary mirror located furthest along the direction opposite to the propagation direction of the initial segment of the parabasal ray,
an upstream edge of the secondary mirror being the point on the secondary mirror located furthest along the direction opposite to the propagation direction of the initial segment of the parabasal ray,
the secondary and tertiary mirrors are oriented so that the upstream boundary of the photosensitive surface of the image sensor is offset along the propagation direction of the initial segment of the parabasal ray relative to a straight line which connects the upstream edge of the primary mirror to:
the upstream edge of the secondary mirror, or
an upstream edge of a screen which surrounds the secondary mirror, and
the upstream edge of the screen being the point on the screen located furthest along the direction opposite to the propagation direction of the initial segment of the parabasal ray
so that:
the secondary mirror or
the screen which surrounds said secondary mirror intercepts stray rays which would otherwise propagate in a straight line directly from the primary mirror to the photosensitive surface of the image sensor.

20 more elements