The laser maze is the ultimate movie-themed security system, which protects valuable artifacts with a web of laser beams that would-be-thieves must stealthily duck, weave, crawl, and jump through without touching any beams and setting off the alarm. In real life, laser mazes don’t make the best home security systems, but they are a lot of fun to build, and even more fun to play with.

CAUTION: Laser light is intense and can damage your eyes. Remove highly reflective surfaces such as mirrors that may redirect laser light into someone’s eyes unexpectedly. Be sure to only use laser powers of 5mW or less to reduce the chance of eye damage in case of accidental eye exposure.

THE BASIC LASER MAZE

Building a basic laser maze is fairly simple: You’ll only need PVC pipe and connectors, “constant on switch” laser pointers, modeling clay, and a fog machine. Cut the PVC pipe into groups of equal length anywhere between about 2–3½ feet and connect them to form a large cage-like structure (Figure  ) that you can walk through (6½ feet high, 5 feet wide, and 10 feet long is a good start). Mount the laser pointers on the sides of the PVC pipe structure with modeling clay, direct them into the center space at different angles, and turn them on. Finally, turn the lights off and pulse on the fog machine to make the laser beams appear bright and beautiful.

For best results, go with the higher quality laser pointers with a “constant on switch” that are designed for extended use. Any color laser pointer works, but green has the brightest effect.

LASER DETECTION

A fun add-on to your laser maze is a detection system that sounds an alarm or flashes a light when someone blocks one of the beams. Mount a photoresistor on the opposite side of the structure from each laser pointer. Wire each photoresistor into a voltage divider circuit and connect it to one of the analog inputs of an Arduino board. When the laser shines on the photoresistor, its resistance is low, but as soon as the beam is blocked, the resistance jumps up, and the voltage to the Arduino pin increases. Program the Arduino to detect this voltage jump and trigger an alarm.

MOVING LASER BEAMS

A moving laser maze creates a whole new experience. Attach each laser pointer to a motor mounted on the PVC pipe structure.

Program each motor to rotate back and forth at different speeds (5–10 seconds per cycle works best) and over various angles to make endless possibilities of changing laser obstacles. You may want to 3D print mounts and custom boxes to keep everything organized.

For detection, mount a large semi-transparent sheet opposite the laser pointers, so each laser makes a moving dot on the sheet.

Set up a camera outside the maze so it can see the entire sheet. You can build a computer vision (CV)program to count the moving dots viewed by the camera, in order to detect when a laser has been blocked.

For CV beginners, scikit-image is a good package to start with for Python, and OpenCV works with multiple programming languages.