Ophthalmic instrument having self-calibrating optical system

摘要

An objective refractor, having illumination and detection paths (1,15) intersecting at a beamsplitter (11) uses light normally lost during testing of an eye to self-calibrate for optical errors introduced during production of the instrument.For calibration, a path selector (13) blocks light transmitted by the beamsplitter (11) along a test path (30), while normally wasted light reflected by the beamsplitter (11) is reflected by a dispersing surface (14) to a detector (24) to determine the location of a carrier (50) at the condition of best focus. During normal testing of an eye, the path selector (13) is pivoted to block the normally wasted light from reflecting from the dispersing surface (14) to the detector (24).