Project brief

Active markers (IR LEDs behind diffusers) typically offer a stronger and more controllable signal than passive retroreflective markers in optical motion capture, but their design involves trade-offs across geometry, optics, and electronics. The marker's shape and diffuser thickness affect how uniformly it appears across viewing angles; the LED count and arrangement affect intensity; and the housing must mount reliably to either single points or rigid multi-marker boards used to estimate orientation. This project investigates these trade-offs and should produce both the singular and multi-marker units to be used in the MSc developed mocap system.

Intended project outputs

• Develop and characterise resin-printed marker housings across varying geometries and locking mechanisms
• Design a compact, self-contained PCB and power architecture for the IR LEDs.
• Produce two mounting configurations: a single-marker mount (with adjustable height options) and a rigid board hosting multiple markers.
• Investigate how marker placement on the rigid board (coplanar vs. non-coplanar, varying spacing) affects orientation estimation.
• Measure marker intensity as a function of viewing angle and quantify diffusion uniformity across different shapes and wall thicknesses. Use the results to determine how many IR LEDs are needed inside each diffuser geometry.
• Verify that prototype markers are reliably detected (intensity + centroid stability) by the OpenMV cameras across the 3–5 m operating range.

Scope:

Mechanical:

• Resin print spherical and hemispherical diffusers across a range of diameters and wall thicknesses.
• Design and test mechanical locking mechanisms between the diffuser and its mount: bayonet mount, threaded interface, twist-snap.
• Characterise print tolerances and clearances needed for reliable assembly across the chosen locking mechanisms.
• Investigate the effect of print orientation on surface finish, optical uniformity, and mechanical fit.
• Design the two mount configurations: a single-marker mount (with adjustable height options) and a rigid board hosting multiple markers.
• Design the platform-mounting interface**:** how the assembly attaches to an arbitrary host platform as a drop-in unit.
• Investigate rigid-board geometry: coplanar vs. non-coplanar marker arrangements, and the effect of inter-marker spacing on orientation resolution.

Electrical:

• Design a compact PCB integrating the IR LEDs and supporting electronics, subject to the self-contained constraint above.