How can I prevent microwave radiation absorption by a camera lens/electronics inside the microwave (behind the shield)?

Question

Let's say I put in an endoscope like camera with the lens at the inside edge of the box and the wire behind metal sheet. Here's a mockup:

Possible idea: The lens is behind a holes but the hole is directly in front of lens. The lens would be facing inwards to the center from the edge of the cube. This does not seem sufficient as the radiation is being reflected off the walls so it's fairly random. Is there anyway to make it microwave safe for recording while microwave operates?

I watched some microwave tear down videos and it seems like (on a surface level view) most of the electronics are safely just hidden behind a wall. That to me suggests the heat build up isn't too high or the electronics are designed to be heat resistant. In this case the lens/camera is exposed to the radiation..

If you have any ideas/thoughts on how the lens/electronics of the camera can be protected from microwave radiation while having full view of the plate, I would appreciate hearing them.

The thought driving the question is: Would an endoscope like camera be safe from microwave radiation/energy behind the inside microwave box?

Answer 1

This is a very dangerous idea. Your questions and your diagram show the potential for you or someone to get badly hurt.

The only safe way is to place the camera outside the unmodified microwave oven. Make a hood to screen out ambient light. Buy a microwave with a black coloured screen instead of a white one. But don't go modifying the microwave.

Some more detail if you are not convinced:

1. Your diagram shows the camera poking through a hole. Don't do this! A quarter wave, or 3 cm of wire, will form an effective antenna and transfer most of the power of the microwave, to the cable! This will not just damage the camera and the phone/computer, it could injure you if you're holding it, or standing very close.

2. You will notice that there's a gap between the punched metal window and the clear plastic window. This is because there are evanescent waves extending about one hole diameter, out of each hole. The plastic stops you getting too close. Don't put the camera touching the surface of the metal.

3. Microwave ovens are full of dangerous voltages. What happens when your glue comes loose or a child trips on the USB cable and it falls and touches the high voltage terminals inside? The whole phone or computer could be charged to a dangerous voltage, you could kill yourself (Darwin award) or someone else (manslaughter). Don't go adding wires to the inside of a microwave oven.

4. Metal doesn't magically shield the camera from microwaves. It needs to be continuously welded or cleaned and bolted down with an RF gasket. You can't make a shielded box for the camera, inside the cavity, without some way of welding it to the wall of the oven.

If you are looking for a way to design an oven with a camera port, for manufacture (after full safety testing) then there are ways of doing it safely. The 12 cm waves cannot pass through a waveguide smaller than cutoff so you could install a port or tube, perhaps 40 mm diameter and 150 mm long down which the camera could safely peer. There are ways of making the hole larger, even bigger than a wavelength, using specially designed chokes. These are used for conveyor belts running through microwave ovens for continuous cooking.

Answer 2

Don't place the camera in the chamber. Place it outside with other oven electronics and let it peek through one of those holes in the wall.

But I would say keep an open heart towards burnt cameras. You may roast up one or two cameras before finding the way that works.

Answer 3

Microwaves can't pass through the holes. The holes in the metal walls of the microwave oven are intentionally made small enough that the microwaves cannot pass through them.

Arrange your camera so that it looks into the oven through one of the holes. It should be fine.

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Be careful when you take the microwave oven apart. There are capacitors in there that are charged up to several thousand volts. They can hold a charge even when the oven is turned off and disconnected from the outlet.

Avoid putting your camera near the high voltage parts. If your camera is too close, it might get zapped by high voltage.