In some cases, it is desired to also make the front surface appear dark from outside (e.g., for aesthetic reasons). An ALS chip is located below the cover, to sense the ambient light level outside the device. Consider the case where a light transparent cover of a portable electronic device is to have a relatively smooth or uniform front surface, without any physical openings therein. Although relatively small, such IR leakage may still be too much for an ALS in the following situation. In practice of course, the IR cut filter is not ideal in that there still is an appreciable amount of IR content that will pass through the filter and be detected by the sensor. To help alleviate this problem, an IR blocking filter (IR cut filter) can be placed in front of the sensor, to thereby lessen the sensitivity of the sensor's output to IR content. ![]() That is because incandescent lamp lighting has fairly high IR content compared to, for example, fluorescent lamp lighting, and the sensor cannot distinguish between lighting conditions where IR dominates and those where visible dominates. For example, a CMOS-based ALS device would likely indicate that its ambient environment is "brighter" when lit by an incandescent lamp compared to a fluorescent lamp. This creates a problem under some artificial lighting environments. The response of many typical CMOS light sensor structures (e.g., CMOS photodiodes) is dominated by infrared (IR) content, rather than visible content. These IC devices are for the most part manufactured in accordance with a complementary metal oxide semiconductor (CMOS) fabrication process technology. Most recently, advanced, consumer grade, ALS integrated circuit (IC) devices have been developed that have a built-in solid state light sensor together with associated analog and digital circuitry that provide, in real-time, a fairly accurate measurement of the ambient visible light that is incident upon the IC device. The ALS can be used for applications such as automatically managing the brightness of a display screen for better legibility or for conserving battery energy (depending upon the current ambient light level). This is called an ambient light sensor function (or ALS). ![]() Such devices have integrated in them a function that can provide (in real-time) an indication of the current level of visible light in the immediate environment outside the device. Portable electronic devices, such as multi-function smart phones, digital media players, and dedicated digital cameras and navigation devices, have display screens that can be used under various lighting environments. Being that we've never covered this patent before, we present you with a full overview of Apple's invention. Granted Patent Number One: Light Sensing Device having a Color Sensor and a Clear Sensor for Infrared RejectionĪpple has received a Granted Patent that relates to portable electronic devices like the iPhone that have an integrated ambient light sensor (ALS).
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