2021-07-20 (Tu) 24EngLaserGrid Concepts

Remember that movie where the daring [thief/con artist/heister/acrobat] has to break into a fortified [museum/vault/HQ/office], and there's a room with all these laser beams moving in a complicated sequence? Hollywood did a good job of exciting imaginations about physical security systems, but they didn't describe a feasible approach. Are the lasers sensing distance? Are they looking for a broken beam? There are numerous problems with any direction, and that doesn't touch on why anyone would use visible light.

Despite the inherent "Hollywood" in these scenes, the thrill of dodging moving lasers in a virtual tripwire/minefield is exciting. Not to mention it can transform an empty room into a jungle gym with configurable obstacles.

I wanted to recreate the laser grid room that would sound an alert when I break a beam. I recorded the milestones in my brainstorming and forgot a dozen mid-iterations.

My first hope was to buy visible-light distance sensors. Sadly, these don't seem to exist. If they were available, they would have to scan the room and make a 3D map each time they started, or someone repositioned them.
Concept 1, visible light distance sensors

Time-of-flight distance sensors are common, but they all use infrared beams. I could attach a visible laser to them, which should be close enough, but it would still be prone to errors if the sensor got jostled.
Concept 2, IR distance sensors with parallel visible lasers

Instead of distance sensors, I thought about using a camera to track the laser dots and alert me if they jumped position or disappeared. I assume there is some capable machine vision, but I don't have experience in this field, so it was a big maybe.
Concept 3, visible light and webcam

I mentally replaced the central camera with a linear CMOS sensor connected to each laser. A configuration like this would be the visible-light sensor I dreamt of in the first place, but this comes back to the same problem of an overly sensitive device.
Concept 4, linear CMOS sensor and visible laser

Long ago, I read that Wii remotes use IR point tracking. There is a camera in the nose of each unit that reports the X and Y coordinates of the four brightest points, which is why candles are a suitable substitute for the monitor bar. I could put one of them next to four infrared lasers and track the movements. If one of the points didn't match where it was supposed to be, I could assume someone got in the way of the beam.
Concept 5, IR positioning camera a parallel visible lasers

Every concept I'd written so far involved complicated tracking and mapping. I didn't need to know where an "intruder" was, just that a beam was interrupted. If I pointed a tracking camera at the wall from the ceiling and counted the dots, no matter where they were, I should know when someone blocked one. Since I would be counting the infrared points, I can use any color for my visible laser and keep it close to parallel with an IR laser. A system like this would be easy to fool, but for an exercise room, it should be fun. Now I need to shop for fog machines.
Concept 6, IR positioning camera counting dots

The rest of the posts for this project have been arranged by date.
First time here?

Completed projects from year 1
Completed projects from year 2
Completed projects from year 3
Completed projects from year 4
Completed projects from year 5
Completed projects from year 6
Completed projects from year 7

Disclaimer for http://24hourengineer.blogspot.com and 24HourEngineer.com

This disclaimer must be intact and whole. This disclaimer must be included if a project is distributed.

All information on this blog, or linked by this blog, is not to be taken as advice or solicitation. Anyone attempting to replicate, in whole or in part, is responsible for the outcome and procedure. Any loss of functionality, money, property, or similar, is the responsibility of those involved in the replication.

All digital communication regarding the email address 24hourengineer@gmail.com becomes the intellectual property of Brian McEvoy. Any information contained within these messages may be distributed or retained at the discretion of Brian McEvoy. Any email sent to this address, or any email account owned by  Brian McEvoy, cannot be used to claim property or assets.

Comments to the blog may be utilized or erased at the discretion of the owner. No one posting may claim property or assets based on their post.

This blog, including pictures and text, is copyright to Brian McEvoy.