a sensor die that lowers the lens requirements by the use of a variable thickness distribution over the sensor die . the sensing portion of the sensor die has a different number of layers than the non - sensing portion of the sensor die . by reducing the thickness of each layer and / or eliminating one or more unnecessary layers in the sensing portion , the thickness of the sensing portion is reduced to lower the amount of stray light and allow an increase in chief ray angle as well as a decrease in the f - number of the imaging system coupled to the sensor die without compromising the image quality of the sensor die . also , the thickness reduction provides the design engineers with extra allowance in handling the chief ray angle and f - number for a given lens requirements .