Why are IR-Leds switched with Relay?

[Rapido]

I had various cams now (Hootoo, Amcest, Blink). Every time the IR-Leds are activated on any of them I hear a "click", indicating that the leds are switched by means of a relay.
Why is that and why don't they switch silently with a semiconductor?

 

[wittaj]

That is not a relay for the LEDs, that is the IR cut filter moving.

If there was no IR cut filter, you would have a pink image during the day. This shows a halfway stuck IR filter.

 

[Rapido]

Ahh, interesting. Thank you.
Fastes answer ever.

 

[TonyR]

Ahh, interesting. Thank you.
Fastes answer ever.

And a great answer, too.
And here's more on that story about the why's of IR light and the filter:

Night vision is provided by infrared LED's (IR) that a photo-sensitive sensor turns on at night. A mechanical IR cut filter is lowered during the day over the camera's image sensor to filter out IR; IR entering the camera's image sensor is only desirable at night so that's when the IR cut filter is removed, allowing IR light to enter the camera's image sensor. When the cam is first powered up you can hear the mechanical movement of that filter "click" as part of it's boot-up cycle. You can also hear it when it gets dark enough to turn on the IR LED's and remove the IR cut filter.​