LaserPointer Mouse Control - Hackathon Project

A collection of experimental approaches to use a colored laser pointer as a mouse input device on macOS.

The Challenge

Create a laser-pointer-controlled mouse for a MacBook without external hardware (ideally), exploiting unconventional sensing methods.

Three Strategies

Strategy 1: Ambient Light Sensor Computational Imaging

Uses the MacBook's built-in ambient light sensor combined with display rastering patterns to detect laser position through single-pixel imaging techniques (inspired by MIT research on ALS privacy threats).

Strategy 2: FaceTime Camera Reflection Detection

Uses the built-in webcam to detect the laser dot on the screen through reflections or a small mirror placed to view the screen.

Strategy 3: External Photodiode Array (DIY Hardware)

A simple Arduino-based photodiode frame that uses trilateration to locate the laser position - most reliable but requires hardware.

Setup

python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt

Research Findings

Why the Original Idea (LED Pixels as Sensors) Won't Work Directly

• MacBook displays are LCD with LED backlighting, not LED pixels
• LCD pixels modulate transmitted light using liquid crystals, not LEDs
• The backlight LEDs are behind the display panel and not individually addressable
• No known API exposes individual LED voltage readings

What DOES Work

1. Ambient Light Sensor: MacBooks have an ALS (AppleLMUController) that reads ambient brightness. MIT researchers demonstrated computational imaging using ALS + known display patterns.

2. LED Reverse Photovoltaic Effect: LEDs CAN sense light (~2V photovoltaic voltage when illuminated). Arduino projects exist that use this. Could be exploited with external LED arrays.

3. Webcam Detection: Well-established technique using OpenCV to track laser dots in camera feed.

File Structure

• strategy1_als_imaging.py - Ambient Light Sensor approach
• strategy2_webcam_detect.py - FaceTime camera reflection approach
• strategy3_arduino_photodiode/ - Hardware approach (Arduino code + Python interface)
• utils/ - Shared utilities for mouse control

Requirements

• macOS (tested on Apple Silicon)
• Python 3.9+
• For Strategy 2: Camera permissions
• For Strategy 3: Arduino + photodiodes