An optical measurement device comprising: an illumination and detection assembly (2502, 2504) disposed on a printed circuit board and comprising a light emitting diode, LED, configured to output light to a surface portion of a user for measurement and a photodetector configured to detect the output light reflected from said surface portion of the user as a signal, the printed circuit board further comprising an opening disposed between the LED and the photodetector; and a pressure detection assembly (2506, 2518) configured to detect an amount of pressure applied to the illumination and detection assembly (2502, 2504) by the user, the pressure detection assembly (2506, 2518) comprising a force sensor, the pressure detection assembly (2506, 2518) further comprising a force transmitting member (2506, 2508) including an opaque assembly piece and an opaque overhead portion, the opaque assembly piece extending through the opening in between the LED and the photodetector, so as to prevent light emitted by the LED from travelling directly to the photodetector, wherein the opaque overhead portion includes a first access hole for allowing light emitted from the LED to pass through and a second access hole for allowing reflected light to pass through to reach the photodetector, wherein the illumination and detection assembly (2502, 2504) and the pressure detection assembly (2506, 2518) are configured to communicate with a feedback unit that is configured to correlate a quality of the detected signal with the amount of applied pressure by: computing an area under waveforms of detected signals corresponding to a variety of applied pressure amounts, and determining an optimum pressure to correspond a largest computed area, from the variety of applied pressure amounts. an illumination and detection assembly (2502, 2504) disposed on a printed circuit board and comprising a light emitting diode, LED, configured to output light to a surface portion of a user for measurement and a photodetector configured to detect the output light reflected from said surface portion of the user as a signal, the printed circuit board further comprising an opening disposed between the LED and the photodetector; and a pressure detection assembly (2506, 2518) configured to detect an amount of pressure applied to the illumination and detection assembly (2502, 2504) by the user, the pressure detection assembly (2506, 2518) comprising a force sensor, the pressure detection assembly (2506, 2518) further comprising a force transmitting member (2506, 2508) including an opaque assembly piece and an opaque overhead portion, the opaque assembly piece extending through the opening in between the LED and the photodetector, so as to prevent light emitted by the LED from travelling directly to the photodetector, wherein the opaque overhead portion includes a first access hole for allowing light emitted from the LED to pass through and a second access hole for allowing reflected light to pass through to reach the photodetector, wherein the illumination and detection assembly (2502, 2504) and the pressure detection assembly (2506, 2518) are configured to communicate with a feedback unit that is configured to correlate a quality of the detected signal with the amount of applied pressure by: computing an area under waveforms of detected signals corresponding to a variety of applied pressure amounts, and determining an optimum pressure to correspond a largest computed area, from the variety of applied pressure amounts.