Abstract: An apparatus includes a first electromagnetic sensor configured to generate a first sensed signal based at least in part on detection of a first signal having a first wavelength. The apparatus includes a second electromagnetic sensor configured to generate a second sensed signal based at least in part on detection of a second signal having a second wavelength different from the first wavelength. The apparatus includes a processing circuit configured to generate a plethysmogram based at least in part on the first sensed signal and the second sensed signal. The apparatus may include a first emitter configured to emit an optical signal having the first wavelength. The apparatus may include a second emitter configured to emit a reference signal. The first wavelength may be a human-blood-sensitive and human-skin-penetrable wavelength and the second wavelength may be at least one of a human-blood-insensitive wavelength and a human-skin-impenetrable wavelength.

Abstract: According to one embodiment, a power-efficient, low noise photoplethysmographic (PPG) sensor module is provided herein comprising at least one light emitting diode (LED) and at least one photodetector. The LED is generally configured for emitting light, and is positioned on the PPG sensor module for transmitting the emitted light into biological tissue. The photodetector is generally configured for detecting a portion of the light that is transmitted by the LED into the biological tissue and reflected back to the photodetector. The photodetector is an elongated photodetector having a longer dimension that is at least 1.5 times larger than a shorter dimension of the elongated photodetector. By positioning the elongated photodetector on the PPG sensor module, such that the longer dimension is facing towards the first LED, the elongated photodetector is configured to collect substantially more of the reflected light, thereby increasing the signal-to-noise ratio of the detected signal.

Abstract: Ambient light sensing and proximity sensing is accomplished using pairs of stacked photodiodes. Each pair includes a shallow diode with a shallow junction depth that is more sensitive to light having a shorter wavelength and a deeper diode with a deeper junction depth more sensitive to light with longer wavelengths. Photodiodes receiving light passed through cyan, yellow, and magenta filters and light passed without a color filter are used to generate red, green, and blue information through a subtractive approach. The shallow diodes are used to generate lux values for ambient light and the deeper diodes are used for proximity sensing. One or more of the deep diodes may be used in correction to lux determinations of ambient light.

Abstract: An apparatus includes a first electromagnetic sensor configured to generate a first sensed signal based at least in part on detection of a first signal having a first wavelength. The apparatus includes a second electromagnetic sensor configured to generate a second sensed signal based at least in part on detection of a second signal having a second wavelength different from the first wavelength. The apparatus includes a processing circuit configured to generate a plethysmogram based at least in part on the first sensed signal and the second sensed signal. The apparatus may include a first emitter configured to emit an optical signal having the first wavelength. The apparatus may include a second emitter configured to emit a reference signal. The first wavelength may be a human-blood-sensitive and human-skin-penetrable wavelength and the second wavelength may be at least one of a human-blood-insensitive wavelength and a human-skin-impenetrable wavelength.

Abstract: Ambient light sensing and proximity sensing is accomplished using pairs of stacked photodiodes. Each pair includes a shallow diode with a shallow junction depth that is more sensitive to light having a shorter wavelength and a deeper diode with a deeper junction depth more sensitive to light with longer wavelengths. Photodiodes receiving light passed through cyan, yellow, and magenta filters and light passed without a color filter are used to generate red, green, and blue information through a subtractive approach. The shallow diodes are used to generate lux values for ambient light and the deeper diodes are used for proximity sensing. One or more of the deep diodes may be used in correction to lux determinations of ambient light.

Abstract: An ultraviolet radiation sensor includes an ultraviolet pass filter. A first photodiode senses light passing through the ultraviolet pass filter and provides an indication of ultraviolet light. A second photodiode provides an indication of infrared radiation. A correction circuit corrects the indication of ultraviolet light sensed by the first photodiode using the indication of infrared to account for infrared radiation that passes through the ultraviolet pass filter. Additional photodiodes may be used to correct for leakage current in the first and second photodiodes and stray infrared radiation that may affect the output of the first and second photodiodes.