PSYC 380 Lecture 1: Visual Acuity
28 Feb 2017
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Focal length (f)- the distance between lens and image plane for a distant stimulus. Changes depending where the images come to a point on the retina. Focal length from the lens to retina is 0. 017m or 17mm. D = 1/f = 1/0. 017 = 59 d = refractive power of your eye. The (cid:862)effe(cid:272)ti(cid:448)e fo(cid:272)al le(cid:374)gth(cid:863) of a 2-lens system is related to the focal lengths of the individual lenses according to: (cid:2869)=(cid:2869)(cid:3117)+(cid:2869)(cid:3118) = (cid:2869)+(cid:2870: posterior nodal distance (pnd): focal length of the eye (applies to multi-lens systems) Nodal point- the point through which rats pass without being bended. Optical power (in diopter): the inverse of focal length, d = 1/f. Diopters- a measure of the refractive (optical) power of a lens; d = 1/f where f is its focal length in meters. Visual angle (a)- the angle covered by an object determines the size of its image on the retina.
