Nicolet iS50 Aperture Size and Sample Image Size (Beam Diameter)
Issue
What is the image size (IR beam diameter) for a specific aperture size of the Nicolet iS50?
Environment
Nicolet iS50
Resolution
The table below presents the sample focus size (beam diameter) for the minimum to maximum aperture percentages.
| Aperture % | Aperture diameter (mm) | Sample focus diameter (mm) |
| 6.25% (min) | 1.75 | 1.97 |
| 10% | 2.21 | 2.5 |
| 20% | 3.13 | 3.54 |
| 50% | 4.95 | 5.59 |
| 100% | 7 | 7.91 |
| 150% | 8.57 | 9.69 |
| 230% (max) | 10.62 | 11.99 |
Analysis
When totally closed, the aperture still has an hole of 1.75 mm in diameter.
Per optical definition, 7.0 mm in diameter of iris is 100%. By ratio, a 1.75 mm diameter hole is 6.25%, or 1.75/7.0.
By trial and error, it was determined that 7 mm iris amount to step count of 1007. This count shall linearly map to the square root of aperture setting (square root of area of the iris) from 100% to 6.25%, i.e.,
Step count = 1007 * [sqrt(n%) - sqrt(6.25%)] / [sqrt(100%) - sqrt(6.25%)]
Step count = 1007 * [sqrt(n%) - 2.5] / 7.5
Step count = 134.27 * sqrt(n%) - 335.67
It is also determined that the step count for a fully-opened iris is 1700. This would amount to 230%. The above equation satisfies aperture settings from 6.25% to 230%.
Attached to this article is an Excel spreadsheet that can be used to calculate the Aperture setting or Iris Size.
Attachment(s)
| File | Last Modified |
|---|---|
| iS50 Aperture-Iris Size Calculator.xlsx | October 09, 2024 |