Lens Terminology

Question 0

BACK

FOCUS

Answer 0

Distance from the vertex of the rear surface of a lens to the focal plane

Question 1

EFFECTIVE FOCAL LENGTH

EFL

Answer 1

The EFL of a system is the distance from the second principle point to the focal point when the lens is focused at infinity

Question 2

OPTICAL

AXIS

Answer 2

The imaginary line joining the centers of the curvatures of the elements of an optical system

Question 3

ON

AXIS

Answer 3

Used when referring to the center of an image produced by a lens system

Question 4

ABERRATION

Answer 4

Departure from the ideal imagery- used to define residual errors of an optically corrected lens system

Question 5

PARAXIAL

RAY

Answer 5

Rays closest to the axis

Question 6

MARGINAL RAY

Answer 6

A ray the originates that the object point on the axis and goes to the edge of the defining aperture. From there, gets focused back to the axis

Question 7

CHIEF RAY

Answer 7

(Principal ray) originates at object point at the edge of field of view, goes to center of defining aperture then crosses the axis, then continues to edge of image field

Question 8

DISPERSION

Answer 8

(Think prism) when refractive index of glass varies with color or wavelength

Question 9

REFRACTION

Answer 9

Direction of ray changes when passing through different mediums

Question 10

ANGLE OF VIEW

Answer 10

Area of a scene expressed as an angle

Question 11

FIELD OF VIEW

Answer 11

The linear area of a scene that is reproduced by a lens