Huvitz HRK-9000A, Руководство по обслуживанию

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---------------------------------------------------------------------------------------------- Auto Ref/Keratometer HRK-9000A 23
3-5. Principles of Measurement
3-5-1. Measurement principle of refractometry
(1) Light beam from the source is incident on the examinee
’s eye and reflected from
it
’s retina as in the Figure below.
(2) According to the refraction condition of the examinee
’s eye, that is, if the
examinee
’s eye is emmetropia, hyperopia or myopia, the reflected light from the
retina is parallel to the optic axis of the eye, diverge or converge, respectively,.
(3) The light beam reflected from the examinee
’s eye will be relayed by the lens and
mirror, divided by the prism with aperture and then imaged on the TV camera as
lens array bright spots.
(4) From the Ellipsoidal Fitting of the coordinates of lens array bright spots captured
by TV camera, the values of SPH, CYL and AX of eye can be derived.