Huvitz CRK-1, Руководство по обслуживанию, Страница: 32 / 88

---------------------------------------------------------------------------------------------- Auto Ref/Keratometer CRK-1 31
3.5. Principles of Measurement
Measurement principle of refractometry
(1) Light beam from the ring source is incident on the examinee’s eye and refle
cted from it’s retina as in the Figure below.
(2) According to the refraction condition of the examinee’s eye, that is, if the ex
aminee’s eye is emmetropia, hyperopia or myopia, the reflected light from th
e retina is parallel to the optic axis of the eye, diverge or converge, respecti
vely.
(3) The light beam reflected from the examinee’s eye will be relayed by the len
s and mirror, divided by the prism with aperture and then imaged on the TV
camera as ring signal.
(4) From the Ellipsoidal Fitting of the size of ring signal captured by TV camera,
the values of SPH, CYL and AX of eye can be derived.