1. Ophthalmic Optical Instruments I
Telescopes and Microscopes
C. I. OPHTMALMOMETER, CHICAGO ILLINOIS ca 1899

2. TELESCOPES

3. Astronomical (Keplerian) Telescope
Image is Inverted
objective
eyepiece Fe Fo fe fo
M = - fe fo
Virtual image at 25 cm

4. Astronomical Telescope
objective
eyepiece Fe Fo fe fo
Virtual image at infinity D

5. Galilean Telescope plus lens fp fp negative lens fp fp’s coincide
final telescope
parallel rays

7. Viewing Through a Galilean Telescope
parallel
rays
emmetropic
eye
object
iImage
UPRIGHT OBJECT APPEARS UPRIGHT D
GTT 04

8. MICROSCOPES

9. ANGULAR MAGNIFICATION
Apparent size of object depends on angle it subtends at eye.

10. ANGULAR MAGNIFICATION
On average, an object cannot be closer than 25 cm from the eye to be seen clearly.
Average distance of most distinct vision

11. cm
(cm)

12. BASIC MICROSCOPE
magnifier
real image magnification

13. MICROSCOPE MAGNIFICATION25 M = 2 f Im Im 25 M = = M X 1 Ob Ob f
total

14. n a a D NA = sin n OBJECTIVES w.d. EXAMPLE a = 14 n = 1.00 (air)
Numerical Aperture (NA)
Light gathering ability
Resolution a n a
NA = sin n
EXAMPLE a D
= 14
n =
1.00 (air)
w.d.
NA = 1.00 x sin(14 )
NA = 0.24

15. OBJECTIVES
N.A. Examples

16. parallel rays from eyepiece
EYEPIECES (OCULARS)
Huygens
Ramsden
parallel rays from eyepiece
Real image
Real image
converging rays from objective D

17. REAL MICROSCOPE

18. EXPERIMENT 4
Basic Microscope
iris diaphragm
real image on card
onion skin f
Produce real image of onion skin on card.
Mark distance of real image on base.

19. EXPERIMENT 4--CONTINUED
View real image with magnifier (“eyepiece”)
real image plane f
Adjust iris diaphragm. How does image change? Im 25
What is the total magnification? = M X Ob f
total

20. Slit-lamp Biomicroscope

21. The slit-lamp biomicroscope begins with a microscope….
Eyepiece
Objective
Specimen

22. ….change specimen, objective & eyepiece
….turned on its side
….change specimen, objective & eyepiece
Huygens eyepiece
objective
subject
image plane
…….fundamental slit-lamp biomicroscope

23. Galilean telescope to change mag
Build in magnification change without changing working distance
working distance
fobj
Galilean telescope to change mag
no image in image plane

24. Galilean telescope to change mag
Build in magnification change without changing working distance
working distance
fobj
Galilean telescope to change mag
no image in image plane D

25. astronomical telescope
…..add lens to form image in eyepiece image plane
astronomical telescope D

26. Porro* prism 2 right-angle prisms 1800 image rotation
reduce length of telescope
displace image horizontally
Porro -Abbe
*Ignazio Porro – Italian optical instrument maker

27. Slit-lamp with folded optical path

28. D

29. binocular slit-lamp viewing system

30. Operating Microscope

31. Operating microscope optics are very similar to those of the slit-lamp.

33. binocular
astronomical telescopes
Change magnification without changing working distance
magnification change: Galilean telescopes
prism
objective lens

34. Specular Microscope specular == “mirror-like”
Endothelial cells posterior surfaces flat & adjacent to aqueous
Difference in index of refraction gives specular reflection
Useful in seeing corneal endothelial cells

35. Specular Microscope D halogen lamp condenser slit dipping cone lens M
objective
Ramsden eyepiece
film or CCD D

36. endothelium {
slit image
specular reflections and stray light

37. Typical image of endothelium from specular microscope

38. Confocal Principle Red cell in thick sample imaged by lens
Blue cell, nearer to surface, imaged at different point
Pinhole in image plane passes all light from blue cell
Pinhole blocks most of light from red cell
Based on Webb, RH, Rep Prog Phys 59:427

39. Confocal Principle
Point source CONFOCAL with blue cell & pinhole selectively illuminates blue cell
Confocal point source gives less light to red cell, and most is blocked by pinhole
Beam splitter makes confocal microscope epitaxial
Based on Webb, RH, Rep Prog Phys 59:427

40. Confocal Optical Systems:
Pinhole allows light from small volume in sample. Other stray light blocked.
Confocal point source confines light to small volume in sample.
Rejects stray light
Allows Z-axis “sectioning”

41. Confocal systems can improve imaging
Standard specular microscope
Confocal specular microscope

42. Koester’s confocal microscope

43. M M Koester’s Confocal scanning microscope CCD camera lamp
confocal slit
slit
rotating mirror
Koester’s Confocal scanning microscope
objective
specimen

45. Other Scanning Methods and Confocal Microscopes
Tandem Scanning Confocal Microscope
Scanned (laser) Spot Confocal Microscope
Scanned Slit Confocal Microscope

46. Tandem Scanning Confocal Microscopeq r
Uses Nipkow disk
Paul Nipkow ( )
Studied with Helmholtz
Invented disk in 1883
Used for telegraphing pictures
Later used in 1st television
r = a + bq
Sets of holes in plate
Holes on Archimedes spirals D

48. Petran Tandem Confocal Scanning Microscope
Very light inefficient
Petran Tandem Confocal Scanning Microscope

49. TCSM for imaging cornea

51. X-Y mirror confocal laser scanning

52. Confocal slit scanning

53. 3-D reconstruction from confocal images
d fiber from subepithelial plexus
Guthoff et al. Cornea 24:608

54. Commercial Confocal Scanning Corneal Microscopes
Heidelberg HRT II*-Rostock attachment
Nidek Confoscan
Topcon SP-2000p
*also scans retina