VV5351 optical mouse sensor from IntelliMouse Optical 1.1A under reflected darkfield illumination. This sensor often gets incorrectly referred to as an 'MLT04' online due to the markings on top of the package - MLT being a country code referring to ST's assembly plant in Kirkop, Malta. The correct part number (VV5351) is found on the reverse side of the package.
VV5351 ST logo markings.
VV5351 part number markings. Die shows VV5351B but package markings showed VV5351A, most likely the package tooling wasn't updated to save costs.