Abstract:
The invention relates to a method and an apparatus for the detection of the body position, especially while sleeping. More particularly, the invention relates to how the main body positions during sleep can be derived from the distribution of the reflection of a projected IR light from a subject&#39;s body under a blanket. Additionally, the breathing signals can be analyzed to determine the body posture.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention relates to methods and apparatus for the detection of the body position, especially while sleeping. More particularly, the invention relates to how the main body positions during sleep can be derived from the distribution of the reflected IR light from the person&#39;s body under the blanket. Additionally, the breathing signal can be analyzed to determine the body posture. 
       BACKGROUND OF THE INVENTION 
       [0002]    Detection of the body position while sleeping enables improved unobtrusive monitoring. When an image sensor is used as an off-body motion sensor, motion detection or estimation is typically applied to measure the activity level and replace actigraphs. When e.g. two persons share the bed (65% of the adult US population sleep together with a partner or children) the movements can be easier discerned when the body position is known. Motion detection alone is not sufficient for the shared-bed scenario since the areas of motion cannot indicate sufficiently well which motion areas belong to which subject when the two subjects lie close to each other. Motion estimation, where motion vectors are computed per image block, help, but only in cases when the two subjects do not move similarly in the border area. The body position can indicate which movements are likely to belong to one subject and which movements belong to the other subject. 
         [0003]    Moreover, several other benefits regarding the body position information exist, particularly regarding sleep and health. These benefits are
       Enable more robust positional apnea detection: Obstructive sleep apnea (OSA) is the most common category of sleep-disordered breathing. In some patients with OSA, the severity of their apnea and sleep disturbance as measured by the Respiratory Disturbance Index (RDI) is twice as high or more when sleeping on their backs (the supine position) compared to sleeping on their sides (the lateral position). This is referred to as Positional Sleep Apnea (“PSA”). By contrast, patients with less or no change in their RDI related to sleeping position are said to have Nonpositional Sleep Apnea (“NSA”). A device designed based on the instant application may help treating patients diagnosed with PSA and increase their and their doctor&#39;s insight into the severity and possible progression of their disease. Many people suffering from OSA benefit from sleeping at a 30-degree elevation of the upper body or higher, as if in a recliner. This helps prevent the gravitational collapse of the airway. Lateral positions (sleeping on one&#39;s side), as opposed to supine positions (sleeping on the back) are also recommended as a treatment for sleep apnea. Indeed, the gravitational component is smaller in the lateral position than in the supine positions.   Coaching solutions: Body position may be included as a parameter and a user is coached/influenced to bias body positions leading to better sleep quality. The relationship between body position and sleep quality is recognized in the field of sleep research;   Poor sleepers spend longer on their backs with their head straight than good sleepers do;   People who sleep face downwards, on their stomach or on their side, weigh heavily on their jaws with static load, this incorrect position over years can cause symptoms such as migraine, trigeminal neuralgia, pain, hum, tension, and/or dizziness;   Sleep on one&#39;s side can ease the symptoms of apnea.       
 
         [0009]    Complex solutions involving human models and pose recognition exist for detecting the body position of the sleeping person with a camera. They are, however, computationally more complex and only work with a thin blanket where the outline of the person is well visible. Further, such methods do not work for all major body positions (e.g. the distinction between on the stomach and on the back cannot be made). 
         [0010]    US20070118054 discloses a method and a system for monitoring vital signs for the prediction and treatment of physiological ailments. In this patent application only the changes in the posture of the body are considered and are estimated from physiological signals. Methods and systems for monitoring vital signs for the prediction and treatment of physiological ailments are provided. The methods and systems disclosed may be applied to the monitoring of a broad range of physiological ailments or “episodes,” including, but not limited to, asthma, hypoglycemia, coughing, edema, sleep apnea, labor, and REM sleep stages. The methods employ sensors, for example, non-contact sensors, adapted to detect vital signs, such as heart rate or respiration rate, to produce signals that can be analyzed for trends, deviations, or for comparison to prior conditions or criteria. The sensors may be positioned whereby the subject need not be viewed by a health care provider. Some methods and systems employ the use of “scores” based upon a combination of sensed vital signs or based upon a comparison of the vital signs to standard criteria. 
         [0011]    WO2009/083017 discloses a movement detector for detecting the movement of a breathing activity. To enhance a movement detector for detecting the movement of a body breathing or heartbeat activity comprising a Doppler sensor with a microwave oscillator and at least one mixer in such a manner, that the detector is on the one hand efficient and safe with respect to a baby breathing or heartbeat detection and on the other hand a low cost solution, the sensor is performed as a sensor unit with a volume less than 100 cm and a sending energy lower than 10 mW. 
         [0012]    U.S. Pat. No. 5,914,660 discloses a position monitor and alarm apparatus for reducing the possibility of sudden infant death syndrome. A device for reducing the possibility of sudden infant death syndrome (SIDS) as disclosed comprises a position-indicating device effectively coupled to a signal-producing circuit and attached to the clothing of the infant. The position indicating device provides signals, varying in response to prone and other positions assumed by the infant during sleep, allowing an associated alarm device to be activated in response to the infant&#39;s assuming a SIDS-dangerous prone or side-position. In one embodiment, the position of the infant can be determined by an optical sensor interacting with a reflective or other marker adhered to the infant. Gravity or pressure switches may also be used to provide position-responsive signals. A signal generated upon assumption of the SIDS-dangerous prone or side-positions is transmitted to a remote receiver located proximate the infant&#39;s care-giver whereupon an alarm is generated to indicate the need to reposition the infant. A constant low-level or intermitted maintenance signal can be produced to assure the continued and proper operation of the apparatus. An additional awakening alarm can be produced near the sleeping infant to further reduce the likelihood of a SIDS event. 
         [0013]    US2010/0262026 discloses a method for the detection of the sleep position. The method as disclosed in US2010/0262026 uses ECG sensors at fixed positions, not fixed to the patient. The ECG signals recorded from the sensors are used to detect body position, using the variation of ECG potential over the surface of the body. The results may be processed by measuring artifacts related to the angle between the sensors and the heart, in particular the polarity of the QRS complex. The sensors may be fixed on the upper surface of a bed and used to monitor the sleep position. 
       SUMMARY OF THE INVENTION 
       [0014]    It is therefore the object of the invention to provide a method as well as a device enabling a contactless detection of a body&#39;s posture, especially while sleeping. 
         [0015]    With respect to the method, this object is achieved by a method for the detection of the posture of a body, especially while sleeping, the method comprising the steps of:
   providing a bedding;   projection of a pattern of electromagnetic radiation at least on a part of said bedding;   detection of the reflection of the projected pattern caused by a body laying on said bedding;   comparing the reflection pattern with reflection pattern representing typical body postures.   
 
         [0020]    The term bedding as used in this context should be understood as any kind of device enabling a subject to rest his or her body, e.g., a bed, a mattress, a deck-chair, or any other kind of lie down area, while the term subject refers to human or animal. 
         [0021]    The phrase electromagnetic radiation refers to light at the visible wavelength, e.g. about 380 nm to about 780 nm, as well as electromagnetic radiation at a wavelength outside the range visible to the unaided human eye, e.g., IR-radiation at a wavelength within a range of about 780 nm to about 1 mm. 
         [0022]    By comparison of a reflection pattern with reflection patterns representing typical body postures, the position of a body while sleeping can be determined in a contactless way without disturbing the subject monitored in during his or her sleep. The projection of the pattern facilitates the comparison of the detected reflection pattern with patterns representing typical body postures. The distribution of the reflected light is used to determine the body position. When the person lies flat in bed (e.g. in the prone, royal, Cyclops, Waterwings positions, see  FIG. 1 ), the reflected intensity is more evenly distributed from the top to the lower part of the body whereas on the side, the reflected intensity is clearly higher around the middle and top (see  FIG. 2  for examples) for the given light projector. 
         [0023]    According to a preferred embodiment of the invention, for comparing the reflected pattern with the pattern representing typical body postures the person&#39;s body is virtually segmented into 6 major parts: Upper body left and right, middle part left and right, bottom part left and right, of which the sum of the present intensity is computed. Heuristics can be derived based on the location of the light projector. Basically, the reflected light has a higher intensity the smaller the distance between the light projector and the object since the light is reflected back quicker. 
         [0024]    When the person lies flat, either on the belly or on the back, the distribution of the light is hardly altered by a person in bed compared to only the blanket pulled over the bed. However, when the person turns to one side, the upper and middle part of the body change the reflectance in the corresponding area (to larger or lower depending on from where the light is shining and which parts become occluded, due to e.g., legs pulled up, one side of the body blocking other side of the bed). This can be used to derive heuristics to determine the body position of a sleeping person. 
         [0025]    According to a preferred embodiment of the invention, as the light source for the projection of the pattern a laser is used. The use of a laser as a light source enables a sharp projection of a pattern. Preferably, the laser operates at a wavelength which is outside the range that is visible to, or harmful for, the human eye, e.g., in the IR-wavelength range. Preferably, an IR-laser is used that operates at a wavelength of 808 nm to 1064 nm. The energy of the laser used as light source is preferably low enough to ensure avoidance of eye damage caused by laser radiation. Especially preferred, an IR-LED-laser is used as a light source. 
         [0026]    In a further preferred embodiment of the invention, the projection of the pattern on said bedding is performed in an intermittent and/or modulated way. The projection may be performed e.g. once a minute, once every 10 second, or once a second, etc. Performing the projection of the pattern in an intermittent way can reduce discomfort caused by a permanent projection of the pattern. In another embodiment, the projection is modulated in its intensity. By doing so, discomfort caused by the projection can be reduced, too. 
         [0027]    In another embodiment the projection is modulated in its frequency. This may reduce interferences caused by other light sources, e.g., night lights etc. Frequency modulation may be performed by using at least two different projectors, like e.g. two IR-LED-lasers emitting at different frequencies, e.g. 808 nm and 1064 nm. The at least two different projectors may project in an alternating way. 
         [0028]    The detection of the reflection can be performed by video analysis of the pattern projected on the bedding. In a preferred embodiment of the invention, a CCD-sensor is used for the detection the reflection of the pattern. In an even more preferred embodiment of the invention, a low resolution sensor array is used for the detection of the reflection of the pattern. A low resolution sensor in this concern refers to sensors having a resolution of e.g., 125 cpi to 1375 cpi, preferably about 500 cpi, as are used in optical mouse sensors. Due to the reduced information needed for the detection of the body posture, the higher resolution image from a camera is not needed. By using low resolution sensors, the amount of data to be processed can be reduced, while also the privacy of the sleeping person can be preserved since the low resolution image disables identification of the person lying on the bedding. 
         [0029]    According to another embodiment of the invention, additional information is used to determine the body posture more accurately. In an embodiment of the invention, acoustical information and/or information on the breathing amplitude is used to increase the accuracy of the body posture determination. When a flat body position is detected on the basis of the reflected pattern, to distinguish on the back from on the belly, the respiration analysis output can be included. The breathing characteristics extracted from a video signal are different when the person lies on the belly compared to when the person lies on the back. When the person lies on the back, the chest is free to move into open space without any large barrier blocking its movement. However, when the person is on the belly, the chest movement goes into the mattress and the amplitude perceived by the video is reduced. Empirically, 25% higher breathing amplitude is measured when a subject is on his back than on his stomach. The decline in the breathing amplitude towards the end of the ‘back’ sequence is assumed due to the more relaxed state of the subject with more shallow breathing (reduced air flow and chest expansion). When the side position is detected on the basis of the reflected pattern, the body orientation can be robustly determined by including audio signals from the two microphones on the right and left side of the head of the sleeping subject. The microphone with the larger breathing amplitude indicates the orientation of the head. 
         [0030]    According to an embodiment of the invention, acoustical information is retrieved via at least two microphones positioned on both sides of the bedding. To detect the left/right position by means of the microphones, the following approach is used. After performance of a noise-reduction of each of the two microphones (one on the left side, one on the right side) by commonly known techniques, the breathing-events can be detected. This detection is done as shown in the following Algorithm 1, where input samples [k] are processed with k as the sample-index. 
         [0000]    
       
         
               
             
               
             
           
               
                   
               
               
                 Algorithm 1 Event detection 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Initialize k nonzero  = 0 
               
               
                 for k =              ∞ do 
               
               
                  if |x[k]| &gt; ε then 
               
               
                   Δk = k − k nonzero    
               
               
                   if Δk &gt; Δk low  and Δk &lt; Δk high  then 
               
               
                    event detection at sample index k 
               
               
                   end if 
               
               
                   k nonzero  = k 
               
               
                  end if 
               
               
                 end for 
               
               
                   
               
               
                             indicates data missing or illegible when filed 
               
             
          
         
       
     
         [0031]    The threshold Δklow and Δkhigh are adjusted as the minimum and maximum amount of samples that can occur between two breathing events. For example, one can adjust these two parameters as Fs and 6 Fs, with Fs being the sample-rate of the signalx[k]. The sample frequency may vary in a range of between 10 kHz and 100 kHz, preferably between 22 kHz and 96 kHz. Most preferred Fs=22050 Hz. 
         [0032]    According to another embodiment of the invention, the orientation of the light source for the pattern projection as well as of the sensor/camera for the determination of the reflection is consider when detecting the body posture. Heuristics are derived for the main orientations of the camera/sensor and the light source with regard to the bedding (e.g., on top, from the bottom side of the bed, from the left side of bed, or from the right side of bed). Automatically, the corresponding heuristics are applied when the user inputs the estimated location of the camera/sensor and the light source with regard to the bed in a one-time installation of a system capable to perform the inventive method. 
         [0033]    According to another embodiment of the invention, movement information which is available due to simultaneous actigraphy processing are used to render a more robust detection due to indications of position changes and relocation of grid segments on the subject&#39;s body. 
         [0034]    In another aspect, the invention relates to an apparatus for the detection of postures of a body on a bedding, the apparatus comprising:
   A projector for the projection of a pattern of electromagnetic waves on said bedding;   A detector for the detection of the reflection of the pattern projected by said projector;   A data processing means connected to the detector, said data processing means being capable to compare actual reflection detected by the detector with stored reflection patterns representing typical body postures.   
 
         [0038]    According to a preferred embodiment of the invention with respect to the apparatus, the apparatus comprises at least one microphone connected to a data processing means. Even more preferred, the apparatus comprises at least two microphones, located on each side of the bedding. 
         [0039]    In a preferred embodiment, the projector comprises a light emitting diode (LED) as an electromagnetic wave source, preferably a LED-laser emitting in the IR-range of the electromagnetic spectrum. In another preferred embodiment of the invention, the electromagnetic wave source is capable to emit in an intermitted and/or intensity modulated way. 
         [0040]    According to another embodiment of the invention, the data processing means is connected to actuators capable to stimulate a subject to change his or her body posture. The actuators may be integrated in e.g. a pillow, a blanket, a t-shirt etc. In another embodiment, the actuator may be capable to amend the bedding, e.g. by lifting portions of the bedding. 
         [0041]    In another embodiment, the data processing means is connected to an environment controlling means, e.g., an air condition controller, a heating installation controller, a room-light controller or the like. 
         [0042]    In particular, the invention also relates to a system that measures Obtrusive Sleep Apnea (OSA) events, e.g., by measuring breathing by means of a camera or a microphone, a system that measures sleep quality or sleep depth, an output unit for outputting information regarding the determined sleep positions over the night, e.g., how long has the subject slept on the back or on the side. 
         [0043]    In another aspect, the invention further relates to the use of a method and/or device as described above for the detection of physical health conditions related to the body posture during sleep, or for controlling the environmental situation in or around a bedding in dependence of the body posture. For example, the method and/or apparatus can be used for baby-pose detection to reduce SIDS, i.e., detection whether the baby is on the back or belly or side. Further, it can be used as a bed sores alarm system, i.e. detection of how long a person has been in the same position, and sounding an alarm when it is time to change the body position to reduce or prevent bed sores, or as a coaching system that uses the body position itself or the amount of body position shifting for sleep quality evaluation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]    These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. 
           [0045]    In the drawings: 
           [0046]      FIG. 1  shows the most common body postures for sleep (Dunkell, Samuel, “Sleep Positions,” 1977); 
           [0047]      FIG. 2  shows the pattern reflection caused by different body postures at different resolution; 
           [0048]      FIG. 3  shows a schematic illustration of the body posture detection according to an embodiment of the invention; 
           [0049]      FIG. 4  shows the intensity distribution comparison of the reflection between different body postures with a light projector mounted on a wall at the lower end of the bedding; 
           [0050]      FIG. 5  shows the intensity distribution comparison of the reflection between different body postures with a light projector mounted on the ceiling above the head of a subject on the bedding; 
           [0051]      FIG. 6  shows the intensity distribution comparison of the reflection between different body postures with a light projector mounted on the left lower side of the bedding; 
           [0052]      FIG. 7  shows the breathing amplitude comparison when lying on the back versus lying on the belly; 
           [0053]      FIG. 8  shows cumulative audio events over a full-night recording of a subject; 
           [0054]      FIG. 9  shows a left/right posture estimation over a full night; 
           [0055]      FIG. 10  shows integrated actuators usable in combination with the inventive method; 
           [0056]      FIG. 11  shows a bed lifting device usable in combination with the inventive method. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0057]    While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope. 
         [0058]      FIG. 1  shows the most common body postures for sleep. Shown are the Prone, the Semi-Fetal, the Full Fetal, the Flamingo, the Sandwich, the Royal, the Cyclops, and the Water-Wings body posture. The Prone posture is lying face down with the arms extended over the head and the legs stretched out with the feet somewhat apart. The Semi-Fetal position is lying on the side with the knees drawn partway up. The Full Fetal position is lying in a folded position that obscures the face. The legs are flexed at the knees and the knees are drawn up. The Flamingo position is lying on the side with one leg straight out while the other leg is bent at the knee and flexed at a sharp angle. The Sandwich position is lying on the side with the legs placed precisely on top on one another, the thigh, knee and angle of the leg parallel to that of the other. The Royal posture is lying flat on the back. The Cyclops posture is lying flat on the back with one hand covering the eyes. In the Water-Wings posture the head rests in the palms of the hands with the elbows extended on either side. 
         [0059]      FIG. 2  shows a pattern reflection caused by different body postures at different resolution. In row 1 and 2 body postures are shown where the higher intensities of reflection in the middle segments are visible. These are the postures when the subject lies on the side. In row 3 images of a high and low resolution are compared. The low resolution image is sufficient for discriminating side from flat lying postures. Another possibility is to analyze the reflected light segments indicating the orientation of the legs as shown in  FIG. 2 . From the leg orientation, the head orientation can be directly obtained. 
         [0060]      FIG. 3  shows an illustration of the body posture detection according to an embodiment of the invention. In a video signal captured from a camera the distribution of the reflected light is detected. For discriminating similar reflection pattern of flat and side postures, the audio signal coming from two microphones on either side of the bedding are taken in consideration. Further, for discriminating a back from a belly posture the breathing amplitude is taken into consideration. By analyzing the distribution of the light reflectance, the flat or side body position can be identified. When a side body position is detected, the orientation of the face can be either determined by an additional audio signal and/or by the reflected intensity distribution in the lower leg area. Adding another modality renders the system more robust. When only information on the flat or side position is needed, the images can be captured with a low resolution optical sensor, e.g. an optical mouse sensor, e.g. with a resolution of 19×19. Due to the reduced information needed by the algorithm, the higher resolution image from a camera is not needed. This is especially relevant to preserve the privacy of the sleeping person (see third row in  FIG. 2 ). When the flat body position is detected, the breathing amplitude provides an indication on whether the subject is on the belly or on the back since the chest movement is more prominent when the sleeping subject is on his/her back. Heuristics can be derived for the main orientations of the camera/sensor and the light source(s) with regard to the bed (e.g., on the top, from the bottom side of the bed, from the left side of the bed, and/or from the right side of the bed). Automatically, the corresponding heuristics can be applied when the user inputs the estimated location of the camera/sensor and light source(s) with regard to the bed in a one-time installation. 
         [0061]      FIGS. 4 to 6  show the intensity distribution comparison of the reflection between different body postures for light projector positions. In the Figs. the reflection is segmented into six areas, top left/right, middle left/right, and bottom left/right, however, the reflection can be segmented into as low as two segments. For some postures, a smaller number of segments is sufficient to determine body posture. It can also be envisioned to segment the reflection into a larger number than six segments. Additionally, the grids do not need to be rectangular in order to determine a subject&#39;s body posture while sleeping. In  FIGS. 4 to 6  each posture gives a specific distribution of reflection between these six segments. The distribution varies with the position of the light projector and/or the sensor/camera detecting the reflection. The following heuristics are derived for three light source locations in the bedroom (the light source is always positioned higher than the bed). As a dividing line, the “threshold” is chosen as the mean of the whole intensity curve within one segment. This could also have been done differently; it serves only as an approximate indication so that high-low intensities can be distinguished. The x-axis coding reflects flat royal (on back, FR), flat prone (on belly, FP), side right (SR), side left (SL). In total, 71 body positions with 4 different test subjects were measured. A classification accuracy of 96% correct detections and 4% false detections is achieved. 
         [0062]    Bottom (foot part, see  FIG. 4 ):
       At least 1 middle segment high: Side   Both middle segments low: Flat   1 middle segment low, 1 middle segment close to thresh: If 1 bottom segment high: Side, else Flat       
 
         [0066]    Top (on ceiling above upper body, see  FIG. 5 :
       At least 1 middle segment low: Side   Both middle segments high: Flat   1 middle segment close to thresh: If at least 1 top segment high: Side, else Flat Bottom left, see  FIG. 6 :   At least 1 top segment high: Side   Both top segments low: Flat   1 top segment low, 1 top segment close to thresh: If 1 middle segment high: Side, else Flat       
 
         [0073]      FIG. 7  shows the breathing amplitude comparison when lying on the back versus lying on the belly. When a flat body position is detected on the basis of the reflected pattern, to distinguish “on the back” from “on the belly,” the respiration analysis output can be included. The breathing characteristics extracted from a video signal are different when the person lies on the belly compared to when the person lies on the back. When the person lies on the back the chest is free to move into open space without any large barrier blocking its movement. However, when the person is on the belly, the chest movement goes into the mattress and the amplitude perceived by the video is reduced. Empirically, a 25% higher breathing amplitude is measured when a subject is on his back. The decline in the breathing amplitude towards the end of the ‘back’ sequence is assumed due to the more relaxed state of the subject with more shallow breathing (reduced air flow and chest expansion). 
         [0074]      FIG. 8  shows cumulative audio events over a full-night recording of a subject. In this plot, one can see that for each microphone there are around 5000 event detections. Clearly, it can be seen that between 400 and 500 minutes, the posture is mainly toward the left microphone. In order to more clearly detect if the breathing person lies toward the left or the right microphone, one will look at the number of detected events in an epoch of 1 minute. First, a quality measure can be computed as follows: 
         [0000]    
       
         
           
             
               
                 # 
                  
                 
                     
                 
                  
                 
                   events 
                    
                   
                     ( 
                     
                       mic 
                       left 
                     
                     ) 
                   
                 
               
               - 
               
                 # 
                  
                 
                   event 
                    
                   
                     ( 
                     
                       mic 
                        
                       _ 
                        
                       right 
                     
                     ) 
                   
                 
               
             
             25 
           
         
       
     
         [0075]    The division by 25 is chosen as one may assume that roughly 25 breaths are maximally possible during 1 minute. This measure is depicted for a full-night recording in  FIG. 9 . A low-pass filtering of this measure was performed to smooth the data. Finally, the low-pass filtered signal is compared with the mean level in order to detect the posture. As one can see, the posture between 400 and 500 minutes is mainly pointed toward the left microphone, 1 represents a left side posture, −1 represents a right side posture. 
       EXAMPLE 1 
     Alleviation of Obtrusive Sleep Apnea (OSA) 
       [0076]    In this embodiment, it is proposed a positional sleep apnea apparatus for monitoring the sleep position of a person, in an unobtrusive manner, comprising:
   hardware: a camera that makes use of reflected light, and a microphone;   software/algorithms: for detecting the sleep position (lateral or supine), based on the images of the camera and the microphone output. Said algorithms can also include the amount of time the person is on the back or side, and the changes over the night, etc.   
 
         [0079]    If OSA events are detected, the output unit can also relate these events (and the number of occurrences of the event) to the sleep positions during the night. For example: 
         [0080]    Number of OSA events in supine position: 20 
         [0081]    Number of OSA events in lateral position: 1. 
         [0082]    This can be depicted visually in a graph or using text or other modality. If sleep quality or sleep depth is determined, the output unit can also relate the sleep quality or depth to the OSA events and to the body position during sleep. For example, in the lateral position, the subject&#39;s sleep quality was 30% higher than in supine position due to less OSA events. This can also be depicted visually in a graph or using text or other modality. 
         [0083]    The device can also comprise one or both of the following: an actuator to help subjects who sleep on their backs to move to sleep on their side. This can be done using tactile stimulation by, e.g., a bed that automatically lifts up or down, vibrations in the bed, a t-shirt, mattress, or pillow. The system can also behave smarter by detecting the location of a subject in bed in order to trigger certain actuators for optimum and effective turning stimulation as shown in  FIG. 10  and  FIG. 11 . For example, the subject can be stimulated to change the body posture to one in which less OSA events occur, like e.g. the lateral body posture.