An optical navigation device and method for performing optical navigation uses an optically transparent flexible film, which is positioned over a sensor that includes an image sensor array, to allow the image sensor array to receive imaging light from a target surface that is produced in response to illumination light emitted into the target surface from a light source. The imaging light from the target surface is received at the image sensor array of the sensor to capture frames of image data of the target surface. The frames of image data are then compared to estimate relative displacements between the target surface and the image sensor array.