Effect of Stops PDF

OPHD 2604 Effect of Stops Chapter 7 Fundamentals of Optics, Fourth Edition by. Francis A. Jenkins and Harvey E. White. Copyright © 1976, 1957, 1950 13 March 2024 Importance of the effect of stops: To determine how much of the surface of a broad object can be seen through an optical system To determi...

OPHD 2604 Effect of Stops Chapter 7 Fundamentals of Optics, Fourth Edition by. Francis A. Jenkins and Harvey E. White. Copyright © 1976, 1957, 1950 13 March 2024 Importance of the effect of stops: To determine how much of the surface of a broad object can be seen through an optical system To determine the field of view Field of view: Figure 7I: E = the eye of the observer JK = window opening → FIELD STOP GH = observed field When someone looks through a window at a landscape, the field of view of the landscape is limited by the size of the window and the position of the observer When the eye moves closer to the window, the angular field (angle α) increases/widens, therefore INCREASING the FOV When you have a larger window opening, angle α will widen leading to an INCREASE in the FOV Field and Aperture Stops: Field and Aperture Stops: Figure 7A – a single lens with two stops forming the image of a distinct object Three bundles of parallel rays from three different points on the object are shown brought to a focus in the focal plane of the lens It can be seen that the stop closest to the lens limits the size of each bundle of rays, while the stop just in front of the focal plane limits the angle at which the incident bundle can get through to this plane Field and Aperture Stops: Stop closest to the lens = aperture stop Determines the amount of light that reaches any given point in the image Controls the brightness of the image Field and Aperture Stops: Stop closest to the focal plane = field stop Determine the extent of the object/field that will be represented in the image Entrance and Exit Pupils: Entrance and Exit Pupils: Figure 7B – a stop P’E’L’ is placed behind the lens → the stop is in the image space and limits the image rays The image of this real stop (as formed by the lens) is found to lie at the position PEL Since P’E’L’ is inside the focal plane, its image PEL lies in the object space and is virtual as well as erect = entrance pupil The real aperture P’E’L’ is called the aperture stop – if the aperture stop lies within the image space (as in figure 7B), it becomes = exit pupil Entrance and Exit Pupils: Entrance pupil: Definition: The entrance pupil is the image of the stop produced by all the lenses in front of the stop This is the pupil “seen” before refraction by the light bundle approaching the optical system Entrance and Exit Pupils: Exit pupil: Definition: The exit pupil is the image of the stop produced by all the lenses after the stop This is the pupil “seen” by the refracted light bundle when “looking back” Rear and Front Stop: REAR STOP: If the stop is behind the optical system (lens), the exit pupil is the aperture stop itself Rear and Front Stop: FRONT STOP: If the stop is in front of the optical system (lens), the entrance pupil is the aperture stop itself Chief and Marginal Rays: Any ray in the object space that passes through the center of the entrance pupil is called a chief ray After refraction, the chief ray will also pass through the center of the exit pupil The points E and E’ – where the chief ray crosses the axis – are known as the entrance-pupil-point and exit-pupil-point respectively END