what is front vertex?

[The Revolution]

can someone please help figure out front vertex?

D1= +10.75
D2= -5.50
T= 6mm
n=1.60

what is the front vertex power of this lens anyone

[tmorse]

can someone please help figure out front vertex?

D1= +10.75
D2= -5.50
T= 6mm
n=1.60
what is the front vertex power of this lens anyone

You just need to memorize your front and back vertex power formulas.

Front Vertex Power (Fv) = ___D2________ + D1
1-t/n(D2)

with the thickness t required in meters. Think opposites... For Front Vertex Power start with back surface D2, and the for Back Vertex Power (Fv')... start with front surface D1


Back Vertex Power (Fv') = ____D1_______ + D2
1-t/n(D1)

again with t in meters (6mm = 0.006m)

Now simply plug in the numbers and work it out.

[tmorse]

You just need to memorize your front and back vertex power formulas.

Front Vertex Power (Fv) = ___D2________ + D1
1-t/n(D2)

with the thickness t required in meters. Think opposites... For Front Vertex Power start with back surface D2, and the for Back Vertex Power (Fv')... start with front surface D1


Back Vertex Power (Fv') = ____D1_______ + D2
1-t/n(D1)

again with t in meters (6mm = 0.006m)

Now simply plug in the numbers and work it out.

Not coming out right... move the denominator 1-t/n(D2) under the D2
Also move the 1/t/n(D1) under the D1

Will someone who knows how to move these demoninators properly, kindly help him out?

[MakeOptics]

Use Swaines step along method, it's does not require memorization of formulas but a step by step work through of common principles taught in basic optical courses.

D1= +10.75
D2= -5.50
T= 6mm
n=1.60

First the assumption is that the vergence entering the lens is 0.00 or optical infinity so refraction at the first surface (back surface) would be

Power after entering the back surface of the lens = 0.00 + -5.50 = -5.50

Next a ray of light is going to travel through the material itself where no refraction occurs but you lose the distance that the ray travels through the material from the focal length, so convert the power entering the lens into the focal length and subtract the thickness.

focal length = 1.6 / -5.50 = -0.291m or -291mm

Now subtract the 6mm from the focal length for the travel to the front surface.

focal length at front surface = -291mm - 6mm = -2.97mm or -0.297m

Now convert the focal length back into the refractive power at the front surface interface.

Power at front surface = 1.6 / -0.297 = -5.39D

Now compute the refractive power at the front vertex.

Front vertex power = -5.39 + 10.75 = 5.36D

These steps are combinations of simple steps that lead to the correct answer composed of simple, diopter to focal length formula, focal length to diopter, and simple refraction at a surface. This step by step procedure will give a person more intuition in what is going on then using some over complex to memorize formula. If one wants to create the formula it's pretty simple take all these steps and combine them and simplify to get the proper formula's.

[tmorse]

can someone please help figure out front vertex?

D1= +10.75
D2= -5.50
T= 6mm
n=1.60

what is the front vertex power of this lens anyone

D2
Fv = ----------------- + D1
1-t/n(D2)

D1
Fv’= ---------------- + D2
1-t/n(D1)

[tmorse]

Sorry, The Revolution. But I still can't get these formulas to properly orient.

And of course Phil's way is easier and also correct, if you understand vergence.

[MakeOptics]

D2
Fv = ----------------- + D1
1-t/n(D2)

D1
Fv’= ---------------- + D2
1-t/n(D1)

The moderator on this forum has latex formatting enabled. Quick google search and look into the FAQ on the forum for more info on proper formatting.

[tmorse]

Many thanks!

[MakeOptics]

Many thanks!

No prob, check out this link it'll give you a good idea how to format an equation in a post. LaTex is used in a few editors to allow proper formatting of text and especially in mathematics since making a computer output a properly formatted formula can be tricky.

http://www.optiboard.com/forums/misc...o=bbcode#latex

[tmorse]

Many thanks!

PhiTrace,
And thanks again