Multispectral imager

An apparatus, comprising:

• an objective element providing a field of view;
• a tube lens, the tube lens being configured to receive light transmitted through the objective element, the tube lens being further configured to transmit light including spatially offset spectral channels through a convergent image space;
• a dichroic element within the convergent image space, the dichroic element being configured to reflect light of at least one light channel within the convergent image space while transmitting light of at least one other light channel within the convergent image space, the dichroic element being further configured to induce an astigmatism in the light transmitted through the dichroic element;
• and
• a compensating element, the compensating element being configured to induce a second astigmatism in the light transmitted through the dichroic element, the second astigmatism being configured to offset the first astigmatism.

A method comprising:

• transmitting light from a tube lens through a dichroic element, the transmitted light including a first color channel, a second color channel, a third color channel, and a fourth color channel, the first and second color channels being spatially offset from the third and fourth color channels at a plane of incidence on the dichroic element;
• transmitting light of the first and third color channels through the dichroic element, the dichroic element inducing a first astigmatism in the first and third color channels;
• reflecting light of the second and fourth color channels, the light of the second and fourth color channels being reflected by the dichroic element;
• transmitting light of the first and third color channels from the dichroic element through a compensating element, the compensating element inducing a second astigmatism in the first and third color channels, the second astigmatism offsetting the first astigmatism;
• receiving light of the first and third color channels from the compensating element at a camera assembly;
• and
• receiving light of the second and fourth color channels from the dichroic element at the camera assembly.