In embodiments of optical arrangements of a working distance sensor in a
fundus camera that can improve the determination of a correct working
distance as well as the transverse positioning of the camera a number of
near infrared light sources are arranged to project a number of near
infrared illumination beams into the visible light illumination path of
the fundus camera and a live view of the retina under near infrared
illumination is captured and displayed on a monitor. These embodiments of
optical arrangements and associated methods will enable an operator to
directly determine if there is any undesirable flare or other artifact
appearing within a designated region on the infrared retina view as a
result of a wrong alignment of the fundus camera with respect to the eye
in terms of not only the working distance but also the horizontal and
vertical positions. Pattern recognition algorithms can be used to further
enhance the positioning sensitivity of the working distance sensor. An
additional iris alignment sensor can be added to achieve a coarse
alignment and also function as a measure to determine if the dilation of
the iris size is sufficient for different mode of fundus imaging.