# A Spatial 4-DOF Laser Collimation Measurement System
## 1 Introduction
\begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Method** & **Accurate** & **Vantage** & **Drawbacks** & **Costs** & **Measurement Stability** \\ \hline \multirow{4}{*}{interferences} & & & High environmental sensitivity to environmental conditions such as temperature, vibration and air movement & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. In addition, temperature and air pressure can also affect the results. & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. In addition, temperature and air pressure can also affect the results. & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. In addition, temperature and air pressure can also affect the results. & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. In addition, temperature and air pressure can also affect the results. & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. In addition, temperature and air pressure can also affect the results. & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. In addition, temperature and air pressure can also affect the results. & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. In addition, temperature and air pressure can also affect the results. & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. In addition, temperature and air pressure can also affect the results. & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. & & & If the optics have a small amount of displacement, distortion, or surface quality, this can affect the formation and stabilization of the interference fringes. & & & & & \\ \hline \multirow{4}{*}{diffraction} & & & & High demands on the optical system; analysis; suitable for high-resolution image analysis; suitable for observation of fine structures & & & The wavelength of the light source, the quality of the beam and the precision of the experimental setup are highly required. If these conditions are not met, the quality of the diffraction pattern will be affected. & & When the environmental factors (temperature, humidity, vibration, etc.) are better controlled, the stability is higher. The use of certain techniques and equipment, such as single-mode optical fiber, can effectively reduce the impact of temperature drift and obtain more stable results in a shorter period of time \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Optical measurement method performance comparison. ments of \(\pm 1\), repeatable distance measurements of 2.5 \(\upmu\)m, and angle measurements of 2.5 [20], but is easily affected by the environment. [PERSON] et al. proposed a laser net difference straightness interferometer for the simultaneous measurement of 6-DOF motion errors. Multiple degrees of freedom are measured using spacing changes and counting the interference fringes. This measurement method makes full use of the high-precision characteristics of laser interferometry, but the system is complex and the cost is high [21; 22].