1 / 17

Optical systems: Magnifier, microscope, telescope & binoculars

Optical systems: Magnifier, microscope, telescope & binoculars . Hecht 5.7 Wednesday October 9, 2002. Hand Magnifier. What is the angular magnification of the image for an object at the near point or at ∞?. With thin lens. H,H’. h”. θ ’. F. s o. h M ’. l. f. s’. L.

saxon
Download Presentation

Optical systems: Magnifier, microscope, telescope & binoculars

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Optical systems:Magnifier, microscope, telescope & binoculars Hecht 5.7 Wednesday October 9, 2002

  2. Hand Magnifier What is the angular magnification of the image for an object at the near point or at ∞? With thin lens H,H’ h” θ’ F so hM’ l f s’ L

  3. Compound Microscope x’ L Fe Fo Fo Fe Recall xx’ = fo2 x x’ ≈ L Wish to have intermediate image (h’) just inside the focus of the eyepiece x = fo2/L s’ ≈ fo + L s = x + fo

  4. Compound Microscope L Fe h h’ Fo Fo Fe h” • Recall: The magnification of an image formed • at the near point is • at infinity

  5. Compound microscope Total magnification (Image at infinity) (Image at near point)

  6. Compound Microscope In most microscopes, L ~ 16 - 17 cm Objective Eyepiece (image at ∞) 10 X, 20 X, 40 X etc fe = 2.5 cm 10X  Me = 10 40X  fo = 0.4 cm Overall magnification M = 40X10 = 400

  7. Compound Microscope L A.S. Fe Fo Fo Fe EnP ExP Where should the eye be located to view the image? • Optimum viewing – • Place eye near ExP (moving eye away decreases illumination and F.O.V.) • Ensure that exit pupil ~ same size as eye pupil!

  8. Compound Microscope L A.S. Fe Fo Fo Fe EnP ExP Chief Ray Marginal ray

  9. Numerical Aperture Measure of light gathering power N. A. = n sin α Lens Air Oil αg αg’ αo αa Cover Glass ng O

  10. Numerical Aperture If cover glass in air If cover glass immersed in oil (no = 1.516) – between glass and oil there is essentially no refraction since ng = 1.5 Increases the light gathering power by about 1.5 (N.A. roughly analogous to f# of a lens)

  11. Numerical Aperture In optical fibres Cladding n2 Core n1 θc θ no αmax Cladding n2 N.A. = nosinαmax= n1sin θ = n1sin (90o - θc) = n1cos θc This is a measure of the maximum cone of light accepted

  12. Viewing distant objects, e.g. stars star h θ feye Image size on retina h = feyeθ

  13. Telescope Objective Eyepiece fo fe hT=feyeθ’ θ’ θ h’ θ’ h” s’

  14. Telescope Show (magnification of the telescope) (diameter of the exit pupil)

  15. The Hubble Space Telescope 0.3 m secondary mirror 2.4 m primary mirror

  16. Binoculars Two telescopes side-by-side Prisms used to erect images Objective Eyepiece

  17. Binoculars “6 X 30” Angular Magnification (M) Diameter of objective lens, Do (mm) Exit pupil = 5 mm, a good match to the normal pupil diameter For night viewing, a rating of 7 X 50 is better: i.e. ~ 7 mm

More Related