3 Measurement Principle
1) Measurement of eye refraction
A measurement pattern for measurement of eye refraction is projected to an eyeground
to be measured.
The projected pattern changes its size depending on the eye’s refractive power. The
reflected light of this eyeground image is led to the sensor through the measurement
system. The detected data is stored in the frame memory and conducted pattern
analysis by image processing to calculate values of S,C, and A.
Cornea Eyeground
Projected light
Hyperopia
Myopia
Eye to be measured
Projected patterns on the sensor
Rough refractive power (temporary measurement) is calculated by the first
measurement and auto fogging operation and focusing operation of eyeground images
are started based on the data. Then, the actual measurement is started and the
refractive power of the eye to be measured is calculated and displayed.
2) Measurement of corneal curvature radius
A ring-shaped measurement pattern in projected onto a cornea of an eye to be
measured.
The pattern projected on the cornea varies its size depending on the corneal curvature
radius. The projected light is led to the sensor through the cornea measurement
system. The detected data is stored in the frame memory and conducted pattern
analysis by image processing to calculate values of R1, R2, and A.
Cornea
Corneal curvature
radius : small
Corneal curvature
radius : large
Projected light
Eye to be measured
Projected patterns on the sensor
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