Method of visible light and fluorescence imaging with reduced chromatic aberration

A method to collect in-focus images from an endoscopic optical device operable with white light and fluoresced light outside the visible band comprising the steps of

• providing a visible light illuminating means;
• providing an excitation light illuminating means;
• providing an objective lens to collect a visible light spectrum image light and a fluorescence light spectrum image light;
• providing a plurality of relay lenses;
• providing an elongated shaft comprising a distal end and a proximal end, and containing the objective lens, and, proximally to the objective lens, the relay lenses;
• providing a chromatic adjustment assembly positioned proximally to a most proximal relay lens, wherein the chromatic adjustment assembly comprises a first beam splitter and a second beamsplitter;
• providing an image sensor positioned at an image plane;
• collecting a visible light image comprising the steps of:
• illuminating an image scene with the visible illuminating means;
• collecting visible image light in a spectrum comprising wavelengths between 400-700 nm from the illuminated image scene with the objective lens;
• relaying the collected visible image light toward the chromatic adjustment system;
• splitting, with the first beam splitter, the collected visible image light into a first image light spectrum and a second image light spectrum, where the first image light spectrum is different from the second image light spectrum;
• directing the first image light along a first optical path;
• directing the second image light along a second optical path, different from the first optical path;
• recombining, with the second beam splitter, the first image light and the second image light;
• and
• collecting, with the image sensor, a visible light image from the first image light and the second image light, where both first and second image lights are focused substantially onto the image plane;
• and
• collecting a fluorescence imaging image comprising the steps of:
• illuminating an image scene with the excitation illuminating means;
• collecting fluorescence image light from the illuminated image scene with the objective lens;
• relaying the collected fluorescence image light toward the chromatic adjustment system;
• directing, by the first beamsplitter, the fluorescence image light along the second optical path;
• directing, by the second beamsplitter, the fluorescence image light toward the image sensor;
• and
• collecting, with the image sensor, a fluorescence imaging image from the fluorescence image light, and wherein the fluorescence image light is focused substantially onto the image plane.