Steps to reproduce:

1. use the latest version of texlive
2. in a tikz environment, use a lens
3. on the lens, set draw focal points to any value (does not matter)

What happens:
I get this error message:

! Package pgfkeys Error: I do not know the key '/tikz/cross out' and I am going
 to ignore it. Perhaps you misspelled it.

What should happen:
Compile without issues.

Additional info:
According to the pgfmanual.pdf (texdoc tikz), /tikz/cross out does not exist as it is not mentioned anywhere.

Version info:
pdflatex.exe --version
pdfTeX 3.14159265-2.6-1.40.18 (TeX Live 2017/W32TeX)
kpathsea version 6.2.3
Copyright 2017 Han The Thanh (pdfTeX) et al.
There is NO warranty. Redistribution of this software is
covered by the terms of both the pdfTeX copyright and
the Lesser GNU General Public License.
For more information about these matters, see the file
named COPYING and the pdfTeX source.
Primary author of pdfTeX: Han The Thanh (pdfTeX) et al.
Compiled with libpng 1.6.29; using libpng 1.6.29
Compiled with zlib 1.2.11; using zlib 1.2.11
Compiled with xpdf version 3.04

tikz-optics: 43466 (0.2.3)
pgf: 44231 (3.0.1a)

Currently, one has to use quite some math to intersect light rays (paths) with lenses or to make them stop at e.g. a sensor. It would be nice to have basic raytracing features such as starting light at a given position + angle and tikz-optics would propagate the ray accordingly.

version: 0.2.3

minimal reproducible code:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{optics}
\begin{document}
\begin{tikzpicture}[use optics]
    \node[concave mirror, draw mirror focus] {};
\end{tikzpicture}
\end{document}

generates error:

Package pgfkeys: I do not know the key '/tikz/cross out' and I am going to ignore it. Perhaps you misspelled it.

And it will be fixed by adding \usetikzlibrary{shapes}, so I suggest to change

Can I send a pull request an become a contributor? 😄

Steps to reproduce:

1. use the latest version of texlive
2. in a tikz environment, use several tikz-optics nodes together with basic tikz nodes.
3. set "scale=.5" or some other scale in tikzpicture options such as

\begin{tikzpicture}[use optics, scale=.5]
    …
\end{tikzpicture}

What happens:
"scale" scales distances and pure tikz nodes such as path or rectangle, but it does not "object height", "slit height", focal length distances, "generic lamp", …

What should happen:
tikz-optics nodes should be scaled accordingly.

Version info:
pdflatex.exe --version
pdfTeX 3.14159265-2.6-1.40.18 (TeX Live 2017/W32TeX)
kpathsea version 6.2.3
Copyright 2017 Han The Thanh (pdfTeX) et al.
There is NO warranty. Redistribution of this software is
covered by the terms of both the pdfTeX copyright and
the Lesser GNU General Public License.
For more information about these matters, see the file
named COPYING and the pdfTeX source.
Primary author of pdfTeX: Han The Thanh (pdfTeX) et al.
Compiled with libpng 1.6.29; using libpng 1.6.29
Compiled with zlib 1.2.11; using zlib 1.2.11
Compiled with xpdf version 3.04

tikz-optics: 43466 (0.2.3)
pgf: 44231 (3.0.1a)

Could you support balanced photodetector, or senser with mupltiple pature?

I know you say in the manual that these things are under development/likely to change, but at the moment they do not appear to work at all with an up-to-date TeX Live 2016 (TikZ 3.0.1a, tikz-optics v0.2.2).

For example,

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{optics}
\begin{document}
\begin{tikzpicture}[use optics]
\draw[->-={at=0.25}] (0,0) -- (1, 0);
\end{tikzpicture}
\end{document}

throws

! Undefined control sequence.
\pgfkeys@code #1\pgfeov ->\letcs 
                                 \reserved {pgfk@\pgfkeyscurrentpath /unknow...
l.9 \draw[->-={at=0.25}]
                         (0,0) -- (1, 0);
?

and with

\begin{tikzpicture}[use optics]
\draw[put arrow={at=0.25}] (0,0) -- (1, 0);
\end{tikzpicture}

(or \draw [->-] (0,0) -- (1, 0);) I get

! Package pgfkeys Error: I do not know the key '/pgf/decoration/\pgfkeyscurrent
name ' and I am going to ignore it. Perhaps you misspelled it.

See the pgfkeys package documentation for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.9 \draw[put arrow={at=0.25}] (0,0) -- (1, 0);
                                               
? 

Hi!

I noticed a collection of messages in the log file:
Missing character: There is no ; in font nullfont!
I'm using tikz-optics v. 0.2.3

Here is a MWE.

\usepackage{tikz}
\usetikzlibrary{optics}

\begin{document}
	\begin{tikzpicture}[use optics]
	  	\draw[->] (-3,0) -- (3,0) node[anchor=north] {Axe optique};
	  	\node[thick,lens,object height=2cm] (L1) at (0,0) {};
	  	\draw (0,0) node[anchor=south west] {O};
	  	\draw[->-={at=.25},->-={at=.75}]  (-2.8, 1) -- (2.8,-1);
	  	\draw[->>-={at=.25},->>-={at=.75}] (-1.5,-1) -- (1.5, 1);
	  \end{tikzpicture}\vspace{-.8\baselineskip}\\
\end{document}

Thanks for this very useful package!

Is there a possibility of having the slanted line joined to the vertical line at the ends of the vertical mirror? Same request for curved mirrors as well.

Currently, focal points have to be drawn on both sides or not at all. It would be nice to have them drawn on one side only.