Fig. 1. Spot displacement in process of free falling of falling object under different conditions. (a) Falling object rotation; (b) non-perpendicular incident light

Fig. 2. Schematic diagram of device

Fig. 3. Fitting results of single free-falling experiment. (a) Fitting image of results of single experiment; (b) single fitting residual

Fig. 4. Distribution of rotational angular velocity of falling object falling 18 times under leveled state

Fig. 5. Distribution of rotational angular velocity of falling object falling 18 times after adjusting vertical state of vacuum cavity. (a) Adjustment 1; (b) adjustment 2; (c) adjustment 3

Fig. 6. Falling object and its supporting structure. (a) Ideal positioning of falling object; (b) possible positioning of falling object after assembly