在 tikz 中绘制一个循环弯曲路径

Question

我正在绘制一个涉及让路径绕行的光学实验。

使用 PSTricks 可以实现这一点，但我还没有找到使用 TikZ 实现这一点的方法。

我目前拥有的：

• 分束器和镜子采用相对节点定位。
• 只需定义节点的路径即可连接激光器。

到目前为止，我已经尝试了循环库（只能循环回到节点本身，就像状态图一样）、设置弯曲（不会转一整圈，只会稍微弯曲）、使用线圈装饰（到目前为止最好，但很丑，在纸上看起来不太好看）。

有没有人能给我一个可以帮我做这个事情的库？

编辑：我采纳了已接受的答案并做了一些调整。请注意，结束角度设置为垂直。

\documentclass[tikz]{standalone}

\usetikzlibrary{
    positioning,
    arrows,
    decorations.markings,
    hobby
}
\colorlet{maroon}{red!80!black}

\tikzstyle{beamsplitter} = [
    fill=gray,
    fill opacity=0.3,
]

\tikzstyle{left-hand-mirror} = [
    draw,
    postaction=decorate, 
    decoration={
        markings,
        mark=between positions 0.015 and 0.98 step 0.1072 with {\draw (0,0)--(60:3pt);}
    }
]   

\tikzstyle{laser} = [
    draw=maroon,
    line cap=round,
]

\tikzstyle{laserarrow} = [
    line cap=round,
    draw=maroon,
    decoration={markings,mark=at position 0.55 with{\arrow[rotate=-20,maroon]{latex'}}},
    postaction={decorate},
    mark options={color=maroon}
]

\begin{document}

\begin{tikzpicture}[use Hobby shortcut]
    \node (source) {};  

    \node[right=1cm of source] (splitter) {}; 

    \node[above=1 cm of splitter] (mirror) {};
    \node[right=5mm of splitter] (combiner) {};
    \node[right=5mm of mirror] (end) {};

    \path[laser] (source.east) -- (splitter.center);

    \path[laser] (mirror.center) -- (end.center) {};

    \path[laser] (splitter.center) -- (combiner.center);

% Create a node to the left of the midway between the splitter and mirror
    \path (splitter) -- (mirror.center) node[midway,left]
    (midway) {};

% Create a node to the left of the above node
    \node [left = 5mm of midway] (midway-left) {};

% Create the loop
    \draw [laserarrow]
    ([out angle=90, in angle=-90]splitter.center) .. (midway) .. (midway-left) 
    .. (midway) .. (mirror.center);

    \path[left-hand-mirror] (mirror.south west) --
    (mirror.north east) ;

    \draw[beamsplitter] (splitter.north west) rectangle (splitter.south east);
    \draw (splitter.north east) -- (splitter.south west);
\end{tikzpicture}

\end{document}

这将创建以下输出：

我仍需要修复箭头定位，但我正在努力。

Answer 1

可能的解决方案：

\documentclass[tikz,border=10pt,png]{standalone}
\usetikzlibrary{backgrounds,calc,decorations.markings,hobby}
\pgfdeclarelayer{foreground}
\pgfsetlayers{main,foreground}
\colorlet{maroon}{red!80!black}

\begin{document}
\begin{tikzpicture}[use Hobby shortcut]
%\draw[help lines] (-1,-1) grid (4,3);

\draw[thick,maroon] (0,0) -- (2.75,0);

\begin{pgfonlayer}{foreground}% to avoid:
% http://tex.stackexchange.com/q/156613/13304
\node[thick,inner sep=5pt,fill,draw,fill opacity=0.2](n) at (2,0){};
\draw[thick,
  shorten <=\pgflinewidth, 
  shorten >=\pgflinewidth
 ]
 (n.south west)--(n.north east);
\end{pgfonlayer}

\draw[thick,maroon, 
 postaction=decorate, 
 decoration={markings,mark= at position 0.44 with 
  {\arrow[rotate=-12]{stealth};}}
 ] 
 (2,0) .. (1.75,1) .. (1.6,1.25) .. (1,1) .. 
 (1.6,0.75)..([tension=-2]2,2)--(2.75,2);

\draw[thick] (2,2)--($(2,2)!0.25!(1,1)$)coordinate(a)
(2,2)--($(2,2)!0.25!(3,3)$) coordinate(b);

\path[ 
 postaction=decorate, 
 decoration={markings,mark=between positions 0 and 1 step 4pt
  with {\draw[thick] (0,0)--(70:3pt);}}
 ]
 (a)--(b);

\end{tikzpicture}
\end{document}

结果：