Digital Night Vision Binoculars

[Peter Sarf]

I have been given a pair of binoculars that are night vision. But I am wondering if they will work on railway trains ?.

I believe they pick up the infra reflections from the built in infra red torch. To me infra red means heat. The examples seem to indicate these are good for nightlife so I started wondering if they might not be any good for picking up a number painted on a sheet of metal.

I am not sure that I would find these useful often if at all. It is another set of bateries to keep an eye on and discover are flat when I need them !. My worst experience of binocular failure in the dark was using my conventional 16x50 at Crewe about 2002 from the farm field looking at the yard alongside the WCML. Roughly where the new road bridge is now. All I could see was the reflective strip along the 66s. I was blinded by that !. It is a very rare problem and I am not sure infra red would help.

The make and model etc are Bresser Digital Night Vision Bino 3x20. Art No. 96-77480.

They are not a massive magnification or object lens size - I have a basic pair of binoculars that are 16 x 50 which I assume is magnification of 16 times and an objective lens of 50mm. So these night vision binoculars are less than a quarter of the magnification (3x) and an objective lens under a half (20).

Any opinions, ideas or experience of these or similar anyone has for number spotting purposes would be gratefully received.

 

[Ediswan]

I have been given a pair of binoculars that are night vision. But I am wondering if they will work on railway trains ?.

I believe they pick up the infra reflections from the built in infra red torch. To me infra red means heat. The examples seem to indicate these are good for nightlife so I started wondering if they might not be any good for picking up a number painted on a sheet of metal.

For a start, they are not binoculars, there is one lens and one image. The more technical documentation says 'night vision device', but then the marketing department gets involved.

If they work as you suggest, which seems likely, it would depend on the relative 'brightness' of the painted number and its background at the (unspecified) wavelength of infra red light the light source and sensor work at. No reliable way to predict that.

 

[XAM2175]

To me infra red means heat. The examples seem to indicate these are good for nightlife so I started wondering if they might not be any good for picking up a number painted on a sheet of metal.

Infrared light does cause heating, yes, but that's not the principle that these devices will use. They use what's sometimes referred to as "near infrared", meaning that they work with wavelengths of IR light that are very close to 'ordinary' human-visible red light. It's the same as what "night vision" CCTV cameras use - they can pick up the accidental near-infrared illumination from normal light sources, but if this isn't enough they shine a near-infrared light (that's invisible to humans) on the scene and then the camera picks up the reflection. This might work for you if the trains you're observing are passing through lit-up areas and/or if the device has an effective visible-light intensifying function, but if not you probably won't get very far since the on-board illuminator won't reach as far as you'll be able to see.

On the other hand, "long-infrared" or "far infrared" light is the heat-carrying wavelengths used in thermal imaging. These cameras cost much more money, and are useless for reading numbers off locos as they're almost always the same temperature as the metal around them. It's a problem the police experience on the daily, as the numbers on top of their cars can't be read from a helicopter's thermal camera unless the numbers are applied using a special (and very expensive) type of foil material.