Sensor for determining body parameters during exercise

#1. Field of the Invention

#The current invention relates to an exercise device for monitoring body parameters of a wearer during exercise. The invention also relates to sensor for determining sensor signals from which body parameters can be derived and to a method of determining body parameters during exercise.

#2. Background Information

#An exemplary form of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

#FIG. 1 is a schematic illustration of prior art operation of a heartbeat sensor/pulse oximeter,

#FIG. 2 is a graphical illustration of the heartbeat signal with motion noise for a prior art earphone sensor,

#Aspects of the invention will now be illustrated as practiced in a first embodiment of a personal exercise device comprising an earphone sensor for listening to audio files and also for detecting body parameters; such as heartbeat, SpO2 and temperature; during exercise, a signal processing means for resolving sensor information into heartbeat and other body parameters and a workout assistance means for providing feedback of body parameters, exercise instructions and entertainment functions such as, but not limited to, music, video, game, e-book, photo, etc. However, this is not intended to limit the scope of functionality or use of the invention. In a most basic embodiment of the invention the exercise device comprises simply an earpiece sensor and signal processing means for detecting heartbeat for feedback to the user or transmission to another device such as an exercise machine or exercise monitoring equipment. The earphones of the invention include several mechanical design characteristics that ameliorate movement inaccuracies inherent in ear sensors known hitherto. It is not essential to the invention that all such preferred mechanical design characteristics be included in all embodiments of the invention.

#FIG. 3 shows the block diagram of a personal exercise device. A pair of earphones 1 that can be worn by the user is connected to a portable base unit 2 by a cable 3 having conductor means 4, 5 for carrying both audio signals and body parameter sensor signals. The portable base unit 2 has a microprocessor 8, audio module 6 for providing audio signals to the earphones, a sensor module 7 for communicating with the earphone sensors and a user interface/display module 9 for interaction with the user. In one exercise mode the exercise device determines heartbeat of the user and then controls the playback of audio content in accordance with changes in the heartbeat. The heartbeat is also recorded for future reference and for comparing against targeted training level, etc. The earphones 1 may also include an IR thermometer or small thermistor embedded in the earphones 50 for determining body temperature. The bases unit and or earphones 50 may also include an accelerometer/G-sensor for detecting steps from running or walking motion. The earphones may also include a microphone for picking up ambient sound signal and the user could enable or disable or adjusting the ratio of the mixing of ambient sound with content playing back at will. This is necessary because of the mechanical structure for the ear buds blocks a significant part of ambient sound from reaching the user. The earphone mechanical design is illustrated in FIGS. 4 through 10. FIG. 4 schematically illustrates the sensor arrangement of the earphones. Signal emitter 21, 22, 23 and detector 24, 24, 26 devices are located around the circumferential periphery 27 of the earphone. The emitter and detector devices may be either Red or Infared (IR) or both for detecting heartbeat and optionally SpO2. The ear piece is of a type commonly known as an ear bud 50 which has a substantially cylindrical shape for insertion within the outer ear canal of the wearer. In the preferred embodiment the emitters and detectors are grouped in pairs 21-24, 22-25, 23-26 located 120 degrees apart about the circumferential periphery 27 of the ear bud 50. The dashed lines 30, 31, 32 show the path of the IR signals through the soft tissue surrounding the internal wall of the ear canal. A first signal 31 from emitter 21 is detected by detector 25, a second signal 32 from emitter 22 is detected by detector 26 and a third signal 33 from emitter 23 is detected by detector 24. The main signal noise is due to radial motion of the ear bud 50 in the x, y plane within the ear cannel because these movement changes the distance between the sensor and the ear canal wall, which affects the transmitted and receive signal. By using the physical construction where the IR sensors are installed in several circular symmetric locations the effect due to motion in the x, y plane can be approximated as a linear effect on the amplitude of the received signal. It should be noted that the invention has the optimal performance when the IR sensors are installed symmetrically but this should not be a limitation of the invention.

#Some of the signal emitted from the emitters 21, 22, 23 will be reflected from the skin surface of the ear canal. The amount of the IR signals 31, 32, 33 that is reflected from the skin also varies substantially with the aforementioned x, y plane movement of the ear bud 50 within the ear canal. The reflected light is detected by the detectors and must be allowed for in later processing to determine heartbeat and other body parameters from the detected signals. The amount of referred light that is detected by the detectors can be ameliorated by locating the emitters and detectors within recess channels 35, 36, 37 below the outer peripheral surface 28 of the ear bud 50. The recess channels 35, 36, 37 can comprise air or optical glass mediums and form a narrow angle wave guide for IR signals emitted from the emitters or entering the detectors. These wave guide channels 35, 36, 37 produces a narrow angle beam to direct the light in such a way to allow the maximum amount signal by increasing the signal path of the light up and into deeper tissue before the light reflects and is captured by the detector. They also limiting large fluctuation in DC single picked up by detectors.