Point to NotANumber blog for another idea how to create cone mirror.

design.md

@@ -64,14 +64,19 @@ keeps the focal plane of the laser exactly on the exposed surface.

![](./img/anim-cone-arc-scan.gif)

However, making custom mirrors in such a shape at home is not really feasible
(Someone who has access to a lathe: this would essentially be a 45° bevel
on the inside of a large diameter stainless steel pipe with a wall thickness
of about 2-3mm. Then mirror finish polishing this bevel. I don't have
access to a lathe though :/).
However, making custom mirrors in such a shape at home is not easy.

We want to build this machine with minimal accessible tools, so this
is a hurdle.
Possible ways:
 * With a lathe: this would essentially be a 45° bevel on the inside of a
   large diameter stainless steel pipe with a wall thickness of about 2-3mm.
   Then mirror finish polishing this bevel. Stainless steel or aluminum are
   both nicely polisheable, so these could be materials of choice.
 * [John M. suggests on his blog][NaN-cone-mirror] to build such a mirror using
   laser cut parts that, snapped together, defining the shape.

We want to build this machine with minimal accessible tools, so these techniques
have to be explored if they can be done with minimal tools. Till then, let's
see what else we can do.

#### Straight mirror line exposure
We can simplify and use a straight mirror to project downwards to get a line.
@@ -259,4 +264,5 @@ go inside the case.
[arc-project-vid]: https://youtu.be/8tyT4CI-1io
[ldgraphy-vid]: https://youtu.be/G9-JK2Nc7w0
[hardware]: ./hardware#cut-pattern
[f-theta-images]: https://www.google.com/images?q=f+theta+lens
[f-theta-images]: https://www.google.com/images?q=f+theta+lens
[NaN-cone-mirror]: http://notanumber.net/archives/228/circular-mirror-idea-laser-lithography