OP - Ergonomics of Optical Design - Week 9 Flashcards
What happens to depth of field (Diopters) as you increase pupil size?
Decreases. You are more sensitive to blur when moving the viewed object in depth when you have a larger pupil
Conversely, if you have a small pupil it acts like a pinhole and your depth of field increases
What’s the minimum eye relief you want for an optical instrument? And why
12mm
Eyelashes tend to be 9mm
Entrance pupil inside eye is distance of 3mm
9 + 3 = 12mm
Want to match exit pupil of previous system with entrance pupil of your eye
Define eye relief
= the distance from the last surface of the optical instrument to the exit pupil
Minimum eye relief if person wearing glasses?
About 21mm
Downside of a field lens?
Whilst a field lens increases field of view, it also reduces the eye relief.
Therefore you have to keep bringing your eye closer to match
Which instruments don’t have an intrinsic exit pupil, and what is the actual exit pupil used here?
Simple magnification
Galilean telescope
Direct opthalmoscope
Observer’s own pupil acts as exit pupil for the instrument
And the closer the eye to the instrument, the larger the field of view
Will increasing pupil size increase size of point source eg stars
NO
However it will increase in brightness, making it easier to see
So telescopes DONT make stars bigger. Just brighter
Important consideration for binocular system focusing
Need to account for anisometropia (different refractive error in each eye) by have each side adjustable in focus
How can you avoid needing separate adjustments of focus in each eye for binoculars?
Increase the eye relief of the system so that people can just wear their glasses while looking through it
Should two tubes in a binocular system be parallel or converging? If the object is at infinity?
What about for near objects?
Tubes parallel (if object at infinity - e.g binoculars)
Tubes converging (for near objects – e.g slit lamp)
