Resolution of human eye

Angular resolution which is also called as spatial resolution, describes the ability of any device that form as image such as the eye and telescopes, to distinguish small details of an object. The eye which is an organ acts as an instrument in the human optical system.

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 (V-band). 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.