Camera testing using reverse projection

A modulation transfer function or spatial frequency response testing computer system, comprising:

• an input interface;
• and
• an image processor configured to:
• via the input interface, receive a digital test image captured by an imaging system, the digital test image having a plurality of pixels;
• determine a region of interest in the digital test image;
• fit a boundary delineation to a boundary between a first segment and a second segment of the region of interest;
• generate a plurality of accumulation cells running along an accumulation line, the plurality of accumulation cells collectively comprising a one-dimensional accumulation array;
• for each of the plurality of accumulation cells, generate a projection ray extending through the accumulation cell and through the region of interest;
• load each accumulation cell of the one-dimensional accumulation array with an accumulated pixel value, the accumulated pixel value being based on pixel values sampled from each of a plurality of sampling locations along the projection ray;
• and
• derive the modulation transfer function or the spatial frequency response of the imaging system from the one-dimensional accumulation array.

A computer-implemented method for computing a modulation transfer function or a spatial frequency response of an imaging system, the method comprising:

• on a computing device, generating a plurality of accumulation cells running along an accumulation line perpendicular to a boundary delineation, the boundary delineation dividing a first segment of a digital test image captured by the imaging system from a second segment of the digital test image, and the plurality of accumulation cells collectively comprising a one-dimensional accumulation array;
• for each of the plurality of accumulation cells, generating a projection ray extending through the accumulation cell and through the digital test image, each projection ray being parallel to the boundary delineation;
• loading each accumulation cell of the one-dimensional accumulation array with an accumulated pixel value, the accumulated pixel value being based on pixel values sampled from each of a plurality of sampling locations equally spaced along the projection ray;
• and
• deriving the modulation transfer function or the spatial frequency response of the imaging system from the one-dimensional accumulation array.