An inkjet printer uses tiny dots of red, green, and blue ink to produce an image
ID: 1450633 • Letter: A
Question
An inkjet printer uses tiny dots of red, green, and blue ink to produce an image. Assume that the dot separation on the printed page is the same for all colors. At normal viewing distances, the eye does not resolve the individual dots, regardless of color, so that the image has a normal look. The wavelengths for red, green, and blue are red = 660 nm, green = 550 nm, and blue = 470 nm. The diameter of the pupil through which light enters the eye is 2.0 mm. For a viewing distance of 1.2 m, what is the maximum allowable dot separation?
Explanation / Answer
from Rayleigh criterion
theta = 1.22 Lambda /D = d/L
theta (red) = (1.22 * 660 *10^-9)/(2 *10^-3) = d/(1.2)
d red = 0.48 mm
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for green
from Rayleigh criterion
theta = 1.22 Lambda /D = d/L
theta (red) = (1.22 * 550 *10^-9)/(2 *10^-3) = d/(1.2)
d red = 0.402 mm
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fpr blue
from Rayleigh criterion
theta = 1.22 Lambda /D = d/L
theta (red) = (1.22 * 470 *10^-9)/(2 *10^-3) = d/(1.2)
d red = 0.344 mm