The fingertip oximeter, widely used for measuring the oxyhemoglobin and pulse, employs a non-invasive measurement technology. 
The fingertip oximeter runs in such a way that it determines the oxyhemoglobins number and pulse rate by measuring the absorption rate for a selected wavelength of light wave.  In particular, a beam of light from a photoelectric light emitter is arranged to pass through the organism tissue of the user, and is converted to an electrical signal after being detected by a light receiver.  Thereby, an oxygen saturation level (i.e. SpO2) of arterial blood flowing through the finger of the user is obtained and presented on a display of the oximeter. 
In the prior art, however, the user can observe a measurement result in only one direction.  When observing the result, the user has to bend his/her finger to properly observe the displayed information if it is not easy to read.  But bending the finger may lead to partial occlusion of arterial blood capillary so that the strength of pulse will decrease and the strength of signal is weakened.  As a result, the precision of measurement falls.