editor's blog
Subscribe Now

More Selective Light Sensing

Smartphones and other similar devices have a number of sensors on them for different purposes. In particular, there are two light-oriented ones that work differently and accomplish different things.

One is an ambient light sensor; it helps decide how bright or dim to make the screen, or perhaps whether your keyboard needs some backlight.

The other is the proximity detector. It works in conjunction with a small IR LED; the sensor measures the reflections of light from that LED to decide whether the sensor is near… something. This is typically used to shut off the touchscreen when the phone is next to your ear so that your face doesn’t inadvertently trigger various strange, unwanted events while you think you’re just on a call (something evidently referred to as “cheeking”). The sensor isn’t always on – apparently in some phones it’s disabled in landscape mode, or perhaps it’s only enabled when a call is in session.

A bit of Googling makes it clear that people very often confuse and conflate these two sensors.

Maxim noted that ambient light sensors can typically be thrown off by large amounts of ambient UV and IR light. So they’ve integrated in an optical filter to reject invisible light. This gives the ambient light sensor (a fusion of two actual photodiodes plus the filter) a range roughly like that of the human eye.

They’ve also integrated a third photodiode on the same chip, tuned to respond to the IR light from the pulsed LED – which is external to the chip. They’ve filtered this as well to reject – of all things – DC IR light. That enables the sensor to respond to the IR pulse from the LED without being thrown off by a constant level of ambient IR light.

So what you end up with is their MAX44000 sensor, just announced. You can find more info in their release

 

Smartphones and other similar devices have a number of sensors on them for different purposes. In particular, there are two light-oriented ones that work differently and accomplish different things.

One is an ambient light sensor; it helps decide how bright or dim to make the screen, or perhaps whether your keyboard needs some backlight.

The other is the proximity detector. It works in conjunction with a small IR LED; the sensor measures the reflections of light from that LED to decide whether the sensor is near… something. This is typically used to shut off the touchscreen when the phone is next to your ear so that your face doesn’t inadvertently trigger various strange, unwanted events while you think you’re just on a call (something evidently referred to as “cheeking”). The sensor isn’t always on – apparently in some phones it’s disabled in landscape mode, or perhaps it’s only enabled when a call is in session.

A bit of Googling makes it clear that people very often confuse and conflate these two sensors.

Maxim noted that ambient light sensors can typically be thrown off by large amounts of ambient UV and IR light. So they’ve integrated in an optical filter to reject invisible light. This gives the ambient light sensor (a fusion of two actual photodiodes plus the filter) a range roughly like that of the human eye.

They’ve also integrated a third photodiode on the same chip, tuned to respond to the IR light from the pulsed LED – which is external to the chip. They’ve filtered this as well to reject – of all things – DC IR light. That enables the sensor to respond to the IR pulse from the LED without being thrown off by a constant level of ambient IR light.

So what you end up with is their MAX44000 sensor, just announced. You can find more info in their release

Leave a Reply

featured blogs
Apr 19, 2021
Cache coherency is not a new concept. Coherent architectures have existed for many generations of CPU and Interconnect designs. Verifying adherence to coherency rules in SoCs has always been one of... [[ Click on the title to access the full blog on the Cadence Community sit...
Apr 19, 2021
Samtec blog readers are used to hearing about high-performance design. However, we see an increase in intertest in power integrity (PI). PI grows more crucial with each design iteration, yet many engineers are just starting to understand PI. That raises an interesting questio...
Apr 15, 2021
Explore the history of FPGA prototyping in the SoC design/verification process and learn about HAPS-100, a new prototyping system for complex AI & HPC SoCs. The post Scaling FPGA-Based Prototyping to Meet Verification Demands of Complex SoCs appeared first on From Silic...
Apr 14, 2021
By Simon Favre If you're not using critical area analysis and design for manufacturing to… The post DFM: Still a really good thing to do! appeared first on Design with Calibre....

featured video

The Verification World We Know is About to be Revolutionized

Sponsored by Cadence Design Systems

Designs and software are growing in complexity. With verification, you need the right tool at the right time. Cadence® Palladium® Z2 emulation and Protium™ X2 prototyping dynamic duo address challenges of advanced applications from mobile to consumer and hyperscale computing. With a seamlessly integrated flow, unified debug, common interfaces, and testbench content across the systems, the dynamic duo offers rapid design migration and testing from emulation to prototyping. See them in action.

Click here for more information

featured paper

From Chips to Ships, Solve Them All With HFSS

Sponsored by Ansys

There are virtually no limits to the design challenges that can be solved with Ansys HFSS and the new HFSS Mesh Fusion technology! Check out this blog to know what the latest innovation in HFSS 2021 can do for you.

Click here to read the blog post

featured chalk talk

LED Lighting Solutions

Sponsored by Mouser Electronics and Amphenol ICC

LED lighting is revolutionizing lighting design. Engineers now need to consider a host of issues such as power consumption, spectrum, form factor, and reliability. In this episode of Chalk Talk, Amelia Dalton chats with Peter Swift from Amphenol ICC about the latest in LED lighting technology, and solutions for indoor and outdoor applications.

Click here for more about Amphenol Commercial Lighting Solutions ICC