Patient video monitoring systems and methods having detection algorithm recovery from changes in illumination
Inventors
Clark, Matthew Cameron • del Carpio, Derek
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Publication Number
US-10645346-B2
Publication Date
2020-05-05
Expiration Date
Abstract
Various embodiments concern video patient monitoring with detection zones. Various embodiments can comprise a camera, a user interface, and a computing system. The computing system can be configured to perform various steps based on reception of a frame from the camera, including: calculate a background luminance of the frame; monitor for a luminance change of a zone as compared to one or more previous frames, the luminance change indicative of patient motion in the zone; and compare the background luminance to an aggregate background luminance, the aggregate background luminance based on the plurality of frames. If the background luminance changed by more than a predetermined amount, then the aggregate background luminance can be set to the background luminance, luminance information of the previous frames can be disregarded, and motion detection can be disregarded.
Core Innovation
The invention provides a system for monitoring a patient in a patient area having one or more detection zones, using a camera that produces a chronological series of frames and a computing system that receives the frames. For each received frame, the computing system calculates a current background luminance of the current frame as compared to a plurality of previous frames, and calculates an aggregate background luminance based on a respective background luminance for each of the plurality of previous frames. The system further derives zone luminance for each zone using the current background luminance and luminance values of pixels within the zone.
For each detection zone, the system detects patient motion based on a change between the zone luminance and a previous zone luminance exceeding a zone threshold. The system compares the current background luminance of the current frame to the aggregate background luminance and uses that comparison to control whether motion detection is trusted. When the current background luminance changes relative to the aggregate background luminance by more than a predetermined amount, the system disregards previous zone luminance information and erases the background luminance associated with the plurality of previous frames from the aggregate background luminance.
After disregarding prior zone luminance and suppressing motion detection due to the background-change condition, the system sets the previous zone luminance to the zone luminance in subsequent detection so that monitoring can recover in subsequent frames. The system generates an alert with the user interface in response to detected patient motion for the case where the background luminance changes relative to the aggregate background luminance by less than the predetermined amount, while refraining from generating the alert when the background luminance changes by more than the predetermined amount.
Claims Coverage
The document includes three independent claims. Across these independent claims, the main inventive features include background luminance modeling from multiple prior frames, zone luminance computation, motion detection via zone-threshold comparison, and conditional disregard, erasure, or dampening of prior luminance history when background luminance changes beyond a predetermined amount.
Background luminance modeling from previous frames
Calculate a current background luminance of a current frame as compared to a plurality of previous frames of the chronological series; calculate an aggregate background luminance based on a respective background luminance for each of a plurality of previous frames of the chronological series; compare the current background luminance of the current frame to an aggregate background luminance.
Zone luminance computation from pixel luminance within detection zones
For each of one or more zones, calculate a zone luminance based at least in part on the current background luminance and each luminance value of each pixel within a plurality of pixels of the zone.
Motion detection based on zone luminance change exceeding a zone threshold
For each of one or more zones, detect patient motion based on a change between the zone luminance and a previous zone luminance of a previous frame exceeding a zone threshold.
Conditional disregard and erasure of prior luminance history when background changes exceed a predetermined amount
In response to the current background luminance changing relative to the aggregate background luminance by more than a predetermined amount, disregard the previous zone luminance of the previous frame when performing the detecting patient motion step, erase the background luminance associated with the plurality of previous frames from the aggregate background luminance, and set the previous zone luminance to the zone luminance in subsequent detection for patient motion.
Alert generation only when background change is below the predetermined amount
In response to patient motion being detected, generate an alert with the user interface in response to the current background luminance changing relative to the aggregate background luminance by less than the predetermined amount but refrain from generating the alert in response to the current background luminance changing relative to the aggregate background luminance by more than the predetermined amount.
Aggregate background update and motion suppression for subsequent monitoring
In response to the comparison determining that the current background luminance changed relative to the aggregate background luminance by more than a predetermined amount, set the aggregate background luminance to the current background luminance of the current frame in subsequent monitoring, dampen zone luminance information of the one or more frames for subsequent monitoring, disregard the zone luminance change as being indicative of patient motion, and monitor for the zone luminance change of each zone of the one or more zones of the next frame as compared to the current frame.
Erasing zone luminance and updating aggregate background to prevent referencing prior zone information
In response to the comparison determining that the current background luminance changed relative to the aggregate background luminance by more than a threshold amount, setting the aggregate background luminance to the current background luminance of the current frame, erasing zone luminance of the one or more frames so that the zone luminance of the one or more frames are not referenced in subsequent monitoring for a zone luminance change in one or more zones of a next frame indicative of patient motion, disregarding the zone luminance change as being indicative of patient motion, and monitoring for the zone luminance change of each zone of the one or more zones of the next frame as compared to the current frame.
Across the independent claims, patient motion detection in detection zones is driven by zone luminance changes computed from pixel luminance and background luminance modeled from multiple prior frames. When the current background luminance changes relative to an aggregate background by more than a predetermined or threshold amount, the claims require suppressing or disregarding motion indications and erasing, dampening, or otherwise preventing use of prior zone luminance history, while updating the background model so subsequent monitoring can proceed. Alert generation is conditioned to occur only when the background luminance change is less than the predetermined amount.
Stated Advantages
Prevents false alarms by disregarding patient motion detection when the current background luminance changes relative to the aggregate background luminance by more than a predetermined amount.
Allows recovery in subsequent frames by setting the previous zone luminance to the zone luminance in subsequent detection after the background-change condition.
Documented Applications
Patient video monitoring using a patient video monitoring system with detection zones, monitoring patient motion from chronological frames, and generating alerts at a monitoring station via a user interface.
Use in environments with illumination variability to reduce false alarms during patient video monitoring.
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