term 2 optiks Flashcards
(10 cards)
Define the chief ray
The off axis ray which by definition passes through the centre of the aperture stop of an optical system
Define the field stop
A field stop is the aperture that limits the image size - determined by the angle between the optical axis..and the stop
Define the marginal ray
Will be directed to the edge if the entrance pupil, yet post refraction will pass through the point of the edge of the aperture stop (borderline)
Define apparent magnification
How clear the image seems to be in the eye of the examiner - ratio of the image size used with a magnifier vs the object directly when viewed at 250mm, unaided magnifier..
Define diffraction
At the edge of an aperture stop, wavefront is caused to be distorted as it emerges from it
What is the result of a large aperture stop on diffraction
Limited diffraction, as there is only a small proportion at the edge of the aperture whereby the diffraction occurs
Define point spread function
The phenomenon, taking into account real optical world whereby even in the absence of aberrations, due to the finite size of apertures, a small amount of diffraction will occur. Hence, it is defined as the optical image taking into account the level of diffraction present
Entrance Pupil (E):
Image of the aperture stop seen from the entrance of the system, formed by optical elements in front of the stop.
Exit Pupil (E′)
Image of the aperture stop seen from the exit of the system, formed by optical elements behind the stop.
Rayleigh criterion
Rayleigh criterion, two points are just resolvable when the first minimum of one Airy disk overlaps the peak of the other. The minimum angular separation equals the radius of the first dark ring in the Airy pattern.
