Ocular surface interferometry (OSI) devices, systems, and methods are disclosed for measuring a tear film layer thickness (TFLT) of the ocular tear film, including lipid layer thickness (LLT) and/or aqueous layer thickness (ALT). A measured TFLT can be used to diagnosis dry eye syndrome (DES). In certain disclosed embodiments, a multi-wavelength light source can be controlled to illuminate the ocular tear film. Light emitted from the multi-wavelength light source undergoes optical wave interference interactions in the tear film. An imaging device can be focused on the lipid layer of the tear film to capture optical wave interference interactions of specularly reflected light from the tear film combined with a background signal(s) in a first image. The imaging device can also be focused on the lipid layer of the tear film to capture a second image containing the background signal(s) present in the first image.
