You can purchase suitable blue filters at lamp or theatrical specialists, and the type known as half-blue is the best for general purposes.

Any suitable low-pass filter can be used including FIR, IIR and CIC filters.

A filter suitable for gas welding, for instance, should not be used for arc welding.

The use of respirators, fitted with suitable filters, is strongly recommended, where equipment cannot be isolated.

The more initiated can obtain a suitable filter for direct viewing such as aluminized mylar.

Similarly, the view holes corresponding to the green and blue images are covered by suitable filters.

Your best bet is to have a suitable filter installed in the oil line that connects the burner to the tank, to trap and keep the sediment from reaching the burner.

This requires an IR illuminator such as a spotlight with a suitable filter or an IR LED emitter.

Those who were rash enough to wander out into the day could, with the naked eye and a suitable filter, see most of the disc of the sun obscured by a single giant blemish.

A suitable filter at the output of the system can thus recover this small signal variation.