Confused about the time delay between IMU and Camera!

[Mohammad Hussein Yoosefian]

Hello guys, hope you are doing well!

It's quite a while I am using Kalibr, but I couldn't figure out what should I do to reduce the time shift between the IMU and the camera. I am using Python to collect data and by threading, I ensure that the IMU and camera start collecting data almost simultaneously. I plot the data timestamps using rqt-plot and everything seems correct. However, when I run Kalibr, it gives me a 6.2 (s) of time shift between IMU and camera! Do you know what should I consider? I use Respberry Pi V2 (records at 20Hz) and MPU9250 (records at 200Hz).

Thanks in advance!