Description
Calculate diametral and radial clearance of a supplied lens blank.
Optical records distinguish sphere/cylinder powers, principal meridian axes, prism-base labels and eye-specific offset signs. A radial lens-blank margin is half its diametral margin under centered circular geometry. Local optical formulas and code labels do not perform refraction, verify fit or prescribe a lens.
Calculate diametral and radial clearance of a supplied lens blank.
When to use this tool
Use Lens Blank Edge Clearance Margin when you already have blankDiameter, requiredDiameter and need to calculate diametral and radial clearance of a supplied lens blank.
How to use the tool and how it works
- Enter blankDiameter, requiredDiameter. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read diametralMargin, radialMargin, fitsUnderInputs. Inspect fitsUnderInputs before interpreting the associated values.
Require nonnegative blank/required diameters; return blank-required, half that difference and blank>=required.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| blankDiameter | Blank Diameter | Required. Finite number; minimum 0. |
| requiredDiameter | Required Diameter | Required. Finite number; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| diametralMargin | Diametral Margin | Required. Finite number. |
| radialMargin | Half the diametral difference, assuming centered circular geometry. | Required. Finite number. |
| fitsUnderInputs | Fits Under Inputs | Required. Boolean. |
{
"input": {
"blankDiameter": 70,
"requiredDiameter": 64
},
"output": {
"diametralMargin": 6,
"radialMargin": 3,
"fitsUnderInputs": true
}
}Limitations and assumptions
- Assumes centered circular geometry; no decentration, shape, edging allowance, actual fit or safe lens design is checked.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Use the complete verified optical prescription and lens/frame geometry for a design or fit analysis. Preserve sphere-cylinder axis and eye-specific direction conventions; a meridian sum or centered circular clearance is only one part of that calculation.
References
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