Straightness of motion is measured by using an optic called a Wollaston prism and a chevron-shaped mirror. The Wollaston separates the laser beam into two components at a fixed angle. The mirror surfaces intercept the beams at right angles. During displacement, any straightness deviation will cause one beam to shorten and the other to lengthen. The resultant phase change can be converted to a straightness measurement according to the relationship of the mirror angle.

Straightness of motion is measured by using an optic called a Wollaston prism and a chevron-shaped mirror. The Wollaston separates the laser beam into two components at a fixed angle. The mirror surfaces intercept the beams at right angles. During displacement, any straightness deviation will cause one beam to shorten and the other to lengthen. The resultant phase change can be converted to a straightness measurement according to the relationship of the mirror angle
由 Wollaston 棱镜和V形镜组成的光学系统，可用来测量物体移动轨迹的直线度。
Wollaston 棱镜将一束激光分解成有固定夹角的两个光束，这两束光分别垂直穿过V形镜的两个镜面。在位移过程中，物体移动轨迹的任何直线度偏差都会引起一个光束变短，而另一光束变长。依照这个状态变化和V形镜角度的关系，两束光的变化可被转换成直线度测量结果。