Try Black Tape...
Another approach to this problem could be the judicious use of black tape on the bottom of sensor window, so that the short critters (dogs & cats) can't be seen, but the tall ones can be seen.
It worked on my neighbors garage light, which blinded me any time I went out into my back yard. We put the tape on the side of the sensor so that IR movement in my backyard is not seen, but IR movement in his yard is seen.
-AC_Hacker
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