WW2 Japanese light illumitor??? What is it?

[wentzele]

I have an aluminum flashlight looking object which was in my fathers home after he died. He worked on aircraft intstruments and had several Japanese instruments in his collection.
This item is probably used in WW2 aircraft but to this day have never found any information about it.

It has a black lens on it which cannot see through. This is no bulb in it but has a bayonet type socket where the bulb would go. Overall it is a little more then 6 inches long and the tube diameter is about 1 inch.

There is a slide switch with Japanese writing which I only assume is ON and Off.
There is no place for batteries and appears that a cable would have come off the back end with a connector where it would probably get power to operate.

My suspicions are that it would recharge the radium glow dials on the instrument panel for night missions without having a light shinning in the cockpit but that is only a guess. I think the lens is an ultraviolet filter.

Would love to know about it.

Thanks for any information you might be able to provide.