1 / 39

Outline

Outline. Focus Photo-transduction Sensitivity / resolution trade-off Measuring the optical quality of the eye Linear systems analysis. Focus - the lens equation. Accommodation - bringing objects into focus. Focused on. Focused on. Some numbers. Refractive power of cornea 43 diopters

gaerwn
Download Presentation

Outline

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. Outline • Focus • Photo-transduction • Sensitivity / resolution trade-off • Measuring the optical quality of the eye • Linear systems analysis

  2. Focus - the lens equation

  3. Accommodation - bringing objects into focus Focused on Focused on

  4. Some numbers • Refractive power of cornea • 43 diopters • Refractive power of lens • 17 - 25 diopters • Other eyes • Diving ducks - 80 diopter accommodation range • Anableps - two pairs of eyes with different focusing power

  5. Accommodation errors(focus problems) • Myopia • Near-sightedness • Emmetropia • Far-sightedness

  6. Accomodation errors(focus problems) • Myopia • Near-sightedness • Emmetropia • Far-sightedness • Presbyopia • Hardening of lense with age (cannot accommodate to near objects)

  7. Depth of Field (DOF) • DOF = range of depths at which objects are “reasonably” in focus • E.g., at which blur is less than some threshold limit. • How can one increase one’s depth of field?

  8. Transduction in the retina

  9. Isomerized (bleached) photopigment retinal opsin

  10. Sensitivity / resolution trade-off • Increase sensitivity => decrease resolution • Increase resolution => decrease sensitivity

  11. Sensitivity / resolution trade-off • Increase sensitivity => decrease resolution • Increase resolution => decrease sensitivity • One example - changing pupil size Increased spatial resolution Shrink pupil Decreased sensitivity

  12. Other examples

  13. Other examples • Wavelength • Time • Wavelength

  14. Duplicity Theory: Two receptor systems • Cones • Encode wavelength information • High resolution image coding in fovea • Low sensitivity • Rods • High sensitivity • Concentrated in periphery • Lower resolution coding in periphery

  15. Part 2 of solution to sensitivity / resolution trade-off • Foveal coding • One-to-one connections from cone receptors to bipolar cells and from bipolar cells to ganglion cells • Peripheral coding (neural pooling) • Many-to-one connections from receptors to bipolar cells Periphery Fovea Receptors Bipolar cells

  16. General solution to sensitivity / resolution trade-off • Place high resolution / low sensitivity system in fovea • Place high sensitivity / low resolution system in periphery • Use eye movements to obtain high resolution images of peripheral objects

  17. Measuring the resolution of the eye • The point spread function • Spatial frequency analysis - the modulation transfer function

  18. Measuring the resolution of the eye • The point spread function • Spatial frequency analysis - the modulation transfer function

  19. Visual angle

  20. Point spread

  21. Point spread function

More Related