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Comment by raldi | Hacker News Reader

"Specifically, the hidden camera [...] reflects the incoming laser pulses at a higher intensity than its surroundings due to an effect called lens-sensor retro-reflection. This occurs when almost all light energy impacting an object is reflected directly back to the source"

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Given this, can you just hold up a flashlight right next to your head and look around the room for bright spots?

This is actually one of the recommended methods if you have no other options. It's not particularly good otherwise because of the limited visibility cone of the hidden camera reflections. From experience, the flashlight often tends to occlude the reflections you want to see, or the user isn't in the right place to see the reflections (near the flashlight).

That's exactly how detection tools work today.

Here is a random one:

https://www.lexuma.com/products/lexuma-xscan-portable-hidden...

Likely. Headlamps are well known tools for collecting spiders at night, when positioned just right they will reflect off the spider's eyes as you move your head around. It's an amazing thing to see spiders everywhere.

For peace of mind that sounds like the worst tool to use.

Started looking for hidden cameras, ended cowering in fear from the thousands of eyes in the closet.

The ones smart enough to remain unseen are the ones you should worry about.

Just try to remember the spiders protect you from the other bugs.

Same with house centipedes!

hOUSE rIVER mONSTERS?

Anyone????

House Atredies?

I sense the Emperor behind it.

No thanks. I'll take my army of friendly neighborhood geckos instead.

Thanks for giving me nightmares.

Can vouch for this having heard the theory and tried the "torch at eye-level" method and been able to zero-in on small spiders from a distance of about 5m.

It's quite amazingly effective, especially the first time, when you're not really convinced.

It is the standard way of detecting concealed lenses.

Random google result:

https://www.pimall.com/nais/startfinder.html

That was actually pretty interesting. Here is a video of the device in use: https://www.youtube.com/watch?v=1x3aDW8ghaY

I am not sure if it is worth the price, but it's cheaper than a top of the line smartphone with a time-of-flight sensor

Agreed, and a very valid point that these off the shelf detectors are pretty cheap compared to ToF smartphones. There are a number of unfavourable things about the detectors though:

- No automated detection, so lots of human subjectiveness on whether a bright spot should be investigated

- Background lighting can be an issue, so the view through the detector can be filled with bright reflections

- When I tried this for longer than 30 seconds, there's really some eye strain involved

The idea is that the smartphone has more than this one purpose, and the detection system can improve with software updates, whereas you get what you see with the detector and nothing more.

The light returns pretty directly to the source which is why most devices designed to use that detection method have the illuminators around an eyepiece so there's less distance between the illuminators and your eye.

I remember we were spotting alligators at the Amazon river with flashlight and their eyes reflections :-)

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