chessboard pattern data from IR sensor MLX90640
So I opened an issue in the official github API library repo. And @LBuydens at Github pointed out the lack of power decoupling capacitors could be a reason leading to this striped pattern. Then I read the data sheet again, and found this paragraph at the very end:


  Power supply decoupling capacitor is needed as with most integrated circuits. MLX90640Bxx is a mixed-signal device with
  sensors, small signal analog part, digital part and I/O circuitry. In order to keep the noise low power supply switching noise
  needs to be decoupled. High noise from external circuitry can also affect noise performance of the device. In many
  applications a 100nF SMD plus 1μF ceramic capacitors close to the Vdd and Vss pins would be a good choice. It should be
  noted that not only the trace to the Vdd pin needs to be short, but also the one to the Vss pin. Using MLX90640Bxx with
  short pins improves the effect of the power supply decoupling. 


With the help of our hardware engineer adding these two capacitors, I finally got a normal frame. Though small temperature difference still exists (likely &lt; 0.5 degrees), it can be ignored.