Lens Thickness Calculator Optiboard

Lens Thickness Formula:

\[ t = \frac{(n - 1) \times (\frac{1}{R_1} - \frac{1}{R_2}) \times d^2}{8} \]

Refractive Index (n):

Radius of Curvature 1 (R₁):

Radius of Curvature 2 (R₂):

Lens Diameter (d):

Lens Thickness (t):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is a Lens Thickness Calculator?

Definition: This calculator estimates the center thickness of a lens based on refractive index, radii of curvature, and lens diameter.

Purpose: It helps opticians and optical engineers determine the appropriate thickness for lenses in eyeglasses and optical instruments.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ t = \frac{(n - 1) \times (\frac{1}{R_1} - \frac{1}{R_2}) \times d^2}{8} \]

Where:

\( t \) — Lens thickness (meters)
\( n \) — Refractive index (dimensionless)
\( R_1, R_2 \) — Radii of curvature (meters)
\( d \) — Lens diameter (meters)

Explanation: The formula calculates the sagittal depth difference between the two lens surfaces at the center.

3. Importance of Lens Thickness Calculation

Details: Proper thickness calculation ensures optical performance, comfort, and safety of eyewear while minimizing material usage.

4. Using the Calculator

Tips: Enter the refractive index (default 1.5 for CR-39 plastic), both radii of curvature (use positive for convex, negative for concave), and lens diameter.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical refractive index for eyeglass lenses?
A: Common materials range from 1.5 (CR-39) to 1.74 (high-index plastic), with glass around 1.52.

Q2: How do I determine the radii of curvature?
A: These are typically specified in the lens prescription (base curve) or can be measured with a lens clock.

Q3: Why does diameter affect thickness?
A: Larger diameters mean greater sagittal depth difference between the lens surfaces at the edges.

Q4: What if one surface is flat?
A: Use a very large number (e.g., 9999) for the flat surface's radius to approximate infinity.

Q5: Does this account for edge thickness?
A: No, this calculates center thickness. Edge thickness depends on lens power and form.