lecture 8- magnification

magnification

The apparent enlargement of an object by an optical instrument.

resolution

The smallest distance between two points that will allow them to be perceived separately

• naked eye : 200 um

Declination angle:

angle that your eyes are inclined downward toward the work area is the declination angle

loupe lenses

• simple

• Compound (Galilean) - 2 lens one convex and one concave

• Prismatic (Kepler) - multiple convex lenses

simple loupe

• object is within focal length

• examples": monoculars, binoculars

compound loupes (Galilean)

• focal point is behind eye piece lens

• the longer -> more magnification but less light

• converging (convex) lens = the objective to magnify the image

• diverging (concave) lens = the eyepiece (closest to eye)

Prismatic (Kepler) loupes

• much heavier

• can go up to 10x magnification

2 types of loupe frames

TTL (Through-the-lens) and flip up

TTL frame

• custom-made

• closest to the eyes

• prescription possible

• mounted over eyes

• made of titanium

flip up frame

• off-the-shelf

• further away from eye

• prescription possible

• Adjustable

• can be shared

inter-pupillary distance

• typically IPD= 60 mm

• adjustable

working distance chart

more mag -> less working distance -> less diameter

depth of field

refers to the spatial depth over which the object being visualized is in sharp focus.

• higher mag -> more narrow/ shallow tip

highest magnification with optimal ergonomics is

microscrope

end magnification formula:

calculates the overall magnification of a system with multiple lenses

(tube focal distance/ lens focal distance) x mag changer factor x eyepiece factor