Optical Triangulation & Standoff // Protocol STR-02
Standoff Resolution & Optical Triangulation Calculator
Calculate lateral X-Y optical resolution (µm/pixel), Z-axis depth sensitivity, triangulation base angles, and minimum resolvable feature limits.
450 mm
150mm (Macro inspection)500mm (Standard)1200mm (Large casting volume)
170 mm
12 MP
24°
12° (Deep slot accessibility)24° (Optimal metrology balance)40° (Maximum Z depth acuity)
Optical Resolution Output
Lateral In-Plane Pixel Resolution (X-Y)
42.5µm / px
0.0425 mm per sensor pixel element
Depth Z Resolution
11.5 µm
Phase-shifted subpixel
Nyquist Min Feature
85.0 µm
2-pixel feature limit
Raw Stereo Baseline:187 mm
Standoff to FOV Ratio:2.65 : 1
Raw Triangulation Z (Uninterpolated):95.5 µm
Triangulation Photogrammetry
The Physics of Stereo Optical Triangulation
1. Triangulation Angle vs. Cavity Occlusion
Depth resolution along the optical Z axis is inversely proportional to the tangent of the triangulation angle $\theta$:
ΔZ = ΔX_pixel / tan(θ)
Widening the angle $\theta$ from 15° to 30° dramatically enhances depth sensitivity. However, wider angles suffer from optical shadowing (occlusion) when inspecting deep slots, narrow bolt holes, or steep undercut shoulders.
2. Fringe Projection Sub-Pixel Phase Shifting
Structured light digitizers project sinusoidal gray-code fringe patterns across the component surface:
- Phase-Shift Interpolation: By shifting sine waves by $90^\circ$ across 4 to 8 camera exposures, algorithms calculate the fringe phase with an accuracy of $1/10$ to $1/25$ of a pixel.
- Surface Finish Impact: Highly reflective shiny chrome or translucent plastics scatter fringes, degrading phase clarity and multiplying effective measurement noise.