Photonics Exam 1

Optical Axis

- An imaginary line that passes through the center of an optical system.

Object Focus

Location on the optical axis where a point source imaged through the lens or optical system will generate an image at infinity (parallel rays out)

Front Focal Plane

Plane normal to the optical axis that contains the object focus. Object points in this plane image at infinity. The distance from this plane to the vertex of the first optical element is the Front Focal Length.

Image Focus

The optical system will image a point source located at infinity on the optical axis to this point (parallel rays into the lens or optical system either converge to this point (real image) or appear to diverge from this point (virtual image).

Back Focal Plane

Plane normal to the optical axis that contains the image focus. Object points at infinity will image in this plane. The distance from this plane to the vertex of the last optical element is the Back Focal Length.

2nd Principal Plane

Plane where the projection of a parallel ray in object space intersects the same ray projected from image space. The ray in image space will pass through the Image Focus.

1st Principal Plane

Plane where the projection of a ray passing through the object focus in object space intersects the same ray projected from image space. The ray in image space will be a parallel ray.

EAective Focal Length

Distance from the Back Focal Plane to the 2nd Principal Plane or the distance from the Front Focal Plane to the 1st Principal Plane. They are the same.

Aperture stop

The optical element that limits the amount of light reaching the image.

Field Stop

The optical element the limits the angular breadth of an object that can be imaged

Entrance Pupil

Image of the aperture stop in object space ( space to left of first optical element )

Exit Pupil

Image of the aperture stop in image space ( space to right of last optical element )

Entrance Window

Image of the field stop in object space

Exit Window

Image of the field stop in image space

Paraxial Ray

Ray that starts on or intersects the optical axis at a small angle

Marginal Ray

Paraxial ray that passes through the edge of the aperture stop.

Parallel Ray

Ray that starts from the object ( typically at the extent ) and travels parallel to the optical axis.

Chief Ray

Ray that starts from the extent of the object and passes through the center of the aperture stop.

Angular Field of View

Angle between the pair of chief rays that that pass through the margin of the f ield stop measured at the entrance window. Outlines the cone of object space that can be imaged.

F-number

Measure of the light gathering ability of an optical system. Effective focal length divided by the diameter of the entrance pupil.

Depth of field

The range of object distances that are in focus in the image.

Optical or dioptric power

Measure of the ray bending ability of lens or optical system. The reciprocal of the effective focal length

Numerical aperture

Angle between the pair of the marginal rays from the object that pass through the margin of the aperture stop.