The diopter unit is simply the inverse of the focal length in meters.
Thus a +2 diopter lens has a focal length of 500mm
You can combine lenses of different diopters arranged in contact - thus a -2 diopter lens plus a +4 diopter lens would give us the same 500mm focal length.
If a lens has surface radii of R1 and R2 and made of glass with an n refractive index the focal length, f, is defined below
R1 and R2 = surface radii (negative for convex lens surface)
ng = refractive index of the lens glass
f = focal length of lens
Depth of Field is the minimum to maximum distance in focus.
Contrast ratio is the difference between the brightest and darkest point in an image.
m = Magnification ratio or Power
hi = image height
ho = object height
Di = distance from lens to image
Do = distance from lens to object
C of the Triangle is the same as Radius.
The bottom has a calculation of the Spherometers leg from the radius.
This is an estimation because the voltage drop is close to the band gap of a forward biased diode.
l = wave length in nm
Eg = band-gap voltage
Thus those red LEDs with a 1.9V drop run about 652 nm. (GaAs0.6P0.4)
This appears derived from
Infrared 710nm and goes down to roughly 2000nm.
The visible range is considered to be roughly 400nm to 710nm.
390nm to 420 is Blue (or Violet),
530nm is green
600nm to 710nm is considered red.
Translated from French http://www.dg77.net/photo/tech/fast.htm https://translate.google.com/translate?sl=fr&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fwww.dg77.net%2Fphoto%2Ftech%2Ffast.htm&edit-text=
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