On [another recent question](https://photo.stackexchange.com/q/99290/5007) I noted that it's theoretically possible to take "short-range" pictures that have the perspective as if they were taken at a distance, by means of a system of mirrors:

> 
> To be fair, a "lens" could in principle create distance greater than any external dimension of the lens if it's actually a system of mirrors and lenses by bouncing light rays back and forth multiple times
> 
> 
> 

with another user noting:

> 
> But only if the first *refractive* surface (or curved reflective surface), as opposed to flat *reflective* surfaces, is placed at the other end of all of those mirrors
> 
> 
> 

Is there any commercially-available lens+mirror assembly to achieve such an effect? If not, are there any write-ups/tutorials on assembling something practical?

Here's an awful ASCII-art diagram of a possible design (shown as cross-section):

```
-------------------------------------------------------------\
/-----------------------------------------------------------\|
|/----------------------------------------------------------++---
|\----------------------------------------------------------/|
\------------------------------------------------------------/

```

where horizontal and vertical strokes indicate path of light inside the enclosure and diagonal ones are mirrors at 45-degree angles, with light entering from the top-left and exiting (to refractive lens stage) on the right. As drawn, it should add an effective 5x the length of the "lens" to the distance to the subject; to be of practical benefit it probably needs to be fairly long and/or have a few more loops but I didn't want the ASCII art to get any more unwieldy.