Nidge
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United Kingdom
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Seven Posted at 829 19:00
Mmmh, I thought that the Rayleigh Criterion is not for eyesight, but for optical instruments.
May have to recheck on this.
The human eye can be considered an optical instrument, albeit a poor one which relies on the processing power of the brain to form a coherent image.
The description below is taken. from wikilectures.eu
Regards
Nidge.
The Angular Resolution of Human Eye
The angular resolution or spatial resolution of an optical system can be estimated by Rayleigh's Criterion.
When two point sources are resolved from each other, they are separated by at least the radius of the airy disk. When Θ = 1.22 (λ/D) rad ,
where Θ is the angular resolution, λ is the wavelength of light and D is the diameter of the eye. Remember that 360 degrees = 2π radians.
The eye pupil diameter changes during day and night, whereas the day the pupil size is between 3 mm to 4 mm and at night it is from 5 mm to 9 mm. In addition, the optimal sensitivity of the human eye is approximately 0.55 μm (Vband). So according to Rayleigh's Criterion, we can calculate the spatial resolution of human eye. Lets say that at day time the pupil size is 3 mm and the optimal sensitivity is 0.55 μm, we can apply the rule.
Θ = 1.22(λ/D)rad
=1.22(0.55 μm/3 mm)rad(180 deg/π rad)(1 mm/103 μm)
= 0.0128 deg(3600”/1 deg)
= 50” (day)
Moreover, at night the pupil diameter increases to 9 mm to increase the observation, we can do the same calculation to find the angular resolution of the eye at night.

