1. An optical navigation device comprising: a light source configured to emit illumination light; a sensor including an image sensor array configured to electronically capture frames of image data of a target surface using imaging light from the target surface, the imaging light from the target surface being produced in response to the illumination light emitted into the target surface, the frames of image data providing displacement information of the target surface relative to the optical navigation device; and an optically transparent flexible film extending at least partially over both the light source and image sensor array and further in direct contact with the light source, the flexible film having an upper surface and a lower surface, the flexible film being positioned relative to the image sensor array of the sensor such that the imaging light from the target surface is transmitted out of the lower surface of the flexible film onto the image sensor array of the sensor.