A ray of light (1 Viewer)

. Freeview Channel 9 now.

Inspector Montalbano 4/4.

The inspector sees a bright light, which I think comes from the reflection of the Sun in a flat mirror.

But he finds a Japanese, probably 10×50 Porro prism 1960s? Blue coated binocular in the hayloft.

I think this episode is based on the Ray of light coming from the binocular.

Is this possible? Could a flat surface or another surface in the binocular produce such a ray of light?

Technically speaking, a single ray (a photon-sized path with single-file photons)
wouldn't be detected with an eye (heh....not enough rays!)

But assuming the meaning was a "reflected beam of light", sure...
The sun would only be reflected %5 by a coated lens, and that would
spread out, but that's still a decent amount of light. The spreading
(off the curved surface) actually makes it much more likely to be seen
without needing a perfect angle.

Actually, the Armed Forces use lens flash suppresors in binoculars often
to prevent the enemy from seeing the odd flash.
To wit:
http://www.bhphotovideo.com/c/produ...LASH_Anti_Reflection_Device.html/prm/alsVwDtl

Add suspicious deer to the list of enemies, too.
...and people being spied on.
Hunters sometimes put a 'kill-flash' on their gunsight.

. The bright patch of light on the inspector's face was about 3" x 2"or about 7 cm x 5 cm rectangular.
The hayloft was about 20 m, maybe slightly more, from the inspector.
So the patch of light on the inspector's face was clearly produced by a small hand mirror just a few feet from the inspector. This was a silly thing to do, and the inspector flinched when the sun's image hit his eyes, and actually dangerous for his eyes.

If there was a flat hand mirror in the hayloft, say 20 m away, then this would produce a circular image of the Sun on the inspector's face, and it would be about 20 cm across. So clearly this wasn't the case.

But, yes, a glint from the binocular may have been visible. I don't think I've ever seen glints from binoculars.
Perhaps some of the people on the birdforum have seen this.

I did see an extremely bright glint of light perhaps 10° above the horizon. This was repeated several times.
I estimated it as magnitude -15 or even magnitude -18, say about 50 or 100 times brighter than the full moon.
Luckily, I managed to take several photographs and I was able to see that it was an aircraft, perhaps a Boeing 737 or similar type, tens of miles away.
. The glint was coming from the rudder, which is quite large on these aircraft. I'm told that they are mainly flat surfaces. The reasons for the repeated glints was likely because the autopilot was on. This makes repeated corrections to the control surfaces, which is probably why there were so many repeatable glints. The aircraft was heading more or less towards me. The glints even in daylight were uncomfortably bright and more or less point sources to the unaided eyes, although the camera managed to resolve them.

I've seen numerous glints from aircraft, either from the body or the windows. Also one sees them from car windows and bodies. Also from hubcaps and door handles et cetera.

So it would seem that the inspector may have seen the glint from the binocular but not as shown on the television.

Yup...you called it right.
From binoculars would be a big dim pancake, and from a
mirror at 20m would be a picture of the sun.

Binocular 'glint' would be a lot like car window glint for sure.