This film was a turn of the century 1900s time frame color film. It was a movie not a TV show. British I think. It was about the invention of a projector / lamp that would show creatures that were invisible floating in mid air. The creatures were snake like. The longer the projector was on the more aggressive the creatures became and eventually would have crossed over to our dimension. I can't remember the film and cant find any images on Google. May be a Lovecraft type film
That sounds like The Asphyx (1972).
The main character is a Victorian photogapher. He uses some sort of blue light when taking photographs. When photographing criminals about to be executed, the light appears to trap a creature next to the subject. He discovers that when the creature is trapped like this, the person being executed (hung) does not die. He finds a way to trap the creature and so make himself immortal. His attempts to do the same for his family are not so successful.
You may be thinking of the 1986 movie From Beyond, :
A group of scientists have developed the Resonator, a machine which allows whoever is within range to see beyond normal perceptible reality. But when the experiment succeeds, they are immediately attacked by terrible life forms.
It's very loosely inspired by the H.P. Lovecraft short story of the same name.