A device comprising: an optical element having an interior including a rigid, optically transparent material; a first surface of the optical element, the first surface including a region with an optically transparent surface for capturing images through the optical element; a second surface of the optical element opposing the first surface; a center axis of the optical element passing through the first surface and the second surface; a layer of optically transparent elastomer disposed on the second surface and attached to the second surface, a first side of the layer adjacent to the second surface of the optical element having a second index of refraction matched to a first index of refraction of the second surface, and a second side of the layer opposing the second surface of the optical element having an optical coating with a predetermined reflectance; and characterized in that it further comprises: a sidewall around the interior of the optical element between the first surface to the second surface, the sidewall including one or more light shaping features configured to control an illumination of the second surface through the sidewall; and a mechanical key on an exterior of the optical element for enforcing a predetermined position of the optical element within a fixture of an imaging system, the mechanical key including at least one radially asymmetric feature about the center axis for enforcing a unique rotational orientation of the optical element within the fixture of the imaging system. an optical element having an interior including a rigid, optically transparent material; a first surface of the optical element, the first surface including a region with an optically transparent surface for capturing images through the optical element; a second surface of the optical element opposing the first surface; a center axis of the optical element passing through the first surface and the second surface; a layer of optically transparent elastomer disposed on the second surface and attached to the second surface, a first side of the layer adjacent to the second surface of the optical element having a second index of refraction matched to a first index of refraction of the second surface, and a second side of the layer opposing the second surface of the optical element having an optical coating with a predetermined reflectance; and characterized in that it further comprises: a sidewall around the interior of the optical element between the first surface to the second surface, the sidewall including one or more light shaping features configured to control an illumination of the second surface through the sidewall; and a mechanical key on an exterior of the optical element for enforcing a predetermined position of the optical element within a fixture of an imaging system, the mechanical key including at least one radially asymmetric feature about the center axis for enforcing a unique rotational orientation of the optical element within the fixture of the imaging system. of optically transparent elastomer disposed on the second surface and attached to the second surface, a first side of the layer adjacent to the second surface of the optical element having a second index of refraction matched to a first index of refraction of the second surface, and a second side of the layer opposing the second surface of the optical element having an optical coating with a predetermined reflectance; and characterized in that it further comprises: a sidewall around the interior of the optical element between the first surface to the second surface, the sidewall including one or more light shaping features configured to control an illumination of the second surface through the sidewall; and a mechanical key on an exterior of the optical element for enforcing a predetermined position of the optical element within a fixture of an imaging system, the mechanical key including at least one radially asymmetric feature about the center axis for enforcing a unique rotational orientation of the optical element within the fixture of the imaging system. a sidewall around the interior of the optical element between the first surface to the second surface, the sidewall including one or more light shaping features configured to control an illumination of the second surface through the sidewall; and a mechanical key on an exterior of the optical element for enforcing a predetermined position of the optical element within a fixture of an imaging system, the mechanical key including at least one radially asymmetric feature about the center axis for enforcing a unique rotational orientation of the optical element within the fixture of the imaging system.