Axis — All you need.
A multifunctional smart pen: ruler, goniometer, planimetry tool, precise map pointer, and a limitless graphics tablet.
Read the paper on Zenodo
Abstract
Axis is a smart pen whose tip is always spatially defined. Wherever it moves, its relative coordinates are available in real time. It measures pressure and recognizes button clicks and rear eraser use. Axis acts as a digital ruler, goniometer, planimetry device, precise map pointer, and an unlimited graphics tablet. This page documents the concept, technical architecture, and target performance as a defensive, non-commercial publication to establish prior art.
Objectives
- Precision input on any plane (including monitors)
- 4-click workflow (homography + scale) for reliable metrics
- Rapid planimetry with DXF/SVG export
- Ergonomics (150 mm; Ø 10.9–11.3 mm; 19–22 g)
Tablet mode on monitor: absolute mapping with four-corner calibration.
System Architecture
Sensing & Electronics
• High-DPI optical-flow sensor near the tip
• 6-axis IMU
• Short-range ToF for hover and Z-offset
• Tip pressure sensor
• nRF5340 MCU (BLE 5.x), Li-Po 250–300 mAh, USB-C, haptics + mint LED ring
Firmware & Algorithms
• Four-click plane calibration (homography + scale)
• Compensation: tilt, temperature, tip-to-camera offset
• BLE GATT (pose, pressure, hover, quality) + low-latency USB
UX & Modes
• Planimetry: vertices, perimeters, areas; CAD export (DXF/SVG)
• Tablet mode: mapping on monitors, desks, whiteboards
• Hover 2–10 mm, ~1024 effective pressure levels
Technical illustration — modules, section and key dimensions.
Technical Specifications
| Form factor | 150 mm; Ø 10.9–11.3 mm (taper to 10.6 mm); 19–22 g |
|---|---|
| Materials | Matte PC-ABS; smoked PMMA IR window; subtle micro-texture grip |
| Sensors | IR global-shutter + speckle; near-tip optical-flow; 6DoF IMU; ToF; pressure |
| Electronics | nRF5340 BLE 5.x; 250–300 mAh Li-Po; USB-C; haptics + LED ring |
| Firmware | EKF/UKF 250–500 Hz; 4-click homography; tilt/temp/offset compensation |
| Performance targets | ≤ 0.7 mm RMS (A3); ≤ 1.2 mm RMS (A2 glass); latency < 15 ms BLE (< 8 ms USB); hover 2–10 mm; ~1024 pressure levels |
| Modes | Ruler; Goniometer; Planimetry (DXF/SVG); Tablet mode on monitors; Digital notebook |
| License | CC BY-NC 4.0 — non-commercial |
Gallery
Documentation
The concept and technical targets are published as a non-commercial defensive disclosure.
Notes
License: CC BY-NC 4.0 — non-commercial reuse with attribution.
Collaboration: we’re seeking partners in embedded, optics, firmware, and UX.