US 11,928,846 B2
Presence and absence detection
Daniel Lindstedt, Lund (SE); Maria Zevgren Sundberg, Gothenburg (SE); Annie Thorburn, Ellos (SE); and Maciej Walesiak, Warsaw (PL)
Assigned to ESSITY HYGIENE AND HEALTH AKTIEBOLAG, Gothenburg (SE)
Appl. No. 17/056,084
Filed by Essity Hygiene and Health Aktiebolag, Gothenburg (SE)
PCT Filed May 18, 2018, PCT No. PCT/EP2018/063102
§ 371(c)(1), (2) Date Nov. 17, 2020,
PCT Pub. No. WO2019/219206, PCT Pub. Date Nov. 21, 2019.
Prior Publication US 2021/0209790 A1, Jul. 8, 2021
Int. Cl. G06V 10/143 (2022.01); G01J 1/42 (2006.01); G06T 7/73 (2017.01); G06V 20/52 (2022.01)
CPC G06V 10/143 (2022.01) [G01J 1/42 (2013.01); G06T 7/73 (2017.01); G06V 20/52 (2022.01); G06T 2207/20024 (2013.01); G06T 2207/30196 (2013.01); G06T 2207/30232 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A method for detecting presence and absence of a creature, the method comprising:
receiving an input signal from a radiation sensor;
applying a first low-pass filter to the input signal with a first time constant and generating a first filter output;
applying a second low-pass filter to the received input signal with a second time constant and generating a second filter output;
determining a presence of a creature by comparing a slope of the first filter output to a predetermined value;
setting a first threshold based on the second filter output;
decreasing the second time constant and thereafter waiting until the second filter output becomes equal to the first filter output within a predetermined tolerance;
increasing the second time constant;
calculating a difference between the first threshold and the second filter output;
adjusting the first threshold based on the second filter output; and
determining an absence when the first filter output falls below the first threshold.