edge thickness

[d_eyeguy]

Hi All

I am looking for the formula to calculate edge thickness of a finished and mounted lens. I don’t need it for my self as I have been an Optician for 19 years and can give the customer an educated guess with in 1>2 mm but I need it for some of my staff that have not been an Optician for long, I have asked them to look in there text books but I have not heard back from them so I guess it is up to me to find.

Thanks

Dean

[lensgrinder]

You can do this one of four ways. Go to Darryl Meister's web site and use the on-line tool. Download his Optical Analysis program.
You can use the Sag Approximation Formula:

Sag = ((d/2)² X D) / 2000(n-1)

where d is diameter in mm
D is power
n is index

Then
ET = Sag + Min. Center

Or you can use the Sag formula:
Sag_front = r - sqr root(r²-(d/2)²)
Sag_back = r - sqr root(r²-(d/2)²)

where r is the radius of curvature in Meters or millimeters
d is the diameter in Meters or millimeters
Note r and d need to be in the same unit, either in mm or M.

ET = Sag_back - Sag_front + Minimum Center

[ScottV]

Try here:

http://www.optiboard.com/forums/showthread.php?t=22742

Scott

[d_eyeguy]

You can do this one of four ways. Go to Darryl Meister's web site and use the on-line tool. Download his Optical Analysis program.
You can use the Sag Approximation Formula:

Sag = ((d/2)² X D) / 2000(n-1)

where d is diameter in mm
D is power
n is index

Then
ET = Sag + Min. Center

Or you can use the Sag formula:
Sag_front = r - sqr root(r²-(d/2)²)
Sag_back = r - sqr root(r²-(d/2)²)

where r is the radius of curvature in Meters or millimeters
d is the diameter in Meters or millimeters
Note r and d need to be in the same unit, either in mm or M.

ET = Sag_back - Sag_front + Minimum Center

Thanks for the information
all the best to you

[kwon0504]

Hi All

I am looking for the formula to calculate edge thickness of a finished and mounted lens. I don’t need it for my self as I have been an Optician for 19 years and can give the customer an educated guess with in 1>2 mm but I need it for some of my staff that have not been an Optician for long, I have asked them to look in there text books but I have not heard back from them so I guess it is up to me to find.

Thanks

Dean

If you want to calculate lens thickness with a calcultor, you can simply use this formula below, or you can download the Lens Thickness Calcualtor I developed.

Lens Thickness Formula
T=|(Y^2*F)/((n-1)*2000)|+ET or CT
Y=(|Frame PD-anatomical PD|+ED)/2
where, ET is Edge thickness of plus lens, CT is Center thickness of minus lens

Attached is my latest version of Lens Thickness Calculator.

Sung

[d_eyeguy]

THanks !

[wasan]

Thank you