Light rays emanating from the primary focal point of an ellipsoidal mirror are focused from point F and converge at a secondary focal point A. (Example A)

  In an Ellipsoidal Reflector Spotlight (Leko) a gate and lenses are put in to manipulate the light beam. (Example B)

  Two Plano convex lenses are positioned past the secondary focal point to redirect and focus the beam of light. (Example C)

Example A

Example B

Example C

Ellipsoidal reflector

F

A

F

A

Ellipsoidal

Fresnel

A Fresnel lens is a type of compact lens originally developed by French physicist Augustin-Jean Fresnel for lighthouses. The design allows the construction of lenses of large aperture and short focal length without the mass and volume of material that would be required by a lens of conventional design. Wikipedia

    

How a spherical Fresnel lens collimates light                                1: Cross section of a spherical Fresnel lens

                                                                                                        2: Cross section of a conventional spherical

                                                                                                            plano-convex lens of equivalent power

Spot light (Follow spot)

Optics of an Altman 1000Q Followspot. Image self created from followspot undergoing repair for education purposes at the Summer Performing Arts Company and Red River High School in Grand Forks, ND. From left to right- Lamp, Reflector, Shutter/Iris assembly, Fixed lens, Adjustable lens. -JWGreen 20:55, 26 May 2007 (UTC)

Perhaps the best known brand of spotlight is the Super Trouper by Strong Entertainment Lighting, as made famous by the ABBA song of the same name.