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
Oct 27, 2020
As we continue this blog series, we'€™re going to keep looking at System Design and Verification Online Training courses. In Part 1 , we went over Verilog language and application, Xcelium simulator,... [[ Click on the title to access the full blog on the Cadence Community...
Oct 27, 2020
Back in January 2020, we rolled out a new experience for component data for our discrete wire products. This update has been very well received. In that blog post, we promised some version 2 updates that would better organize the new data. With this post, we’re happy to...
Oct 26, 2020
Do you have a gadget or gizmo that uses sensors in an ingenious or frivolous way? If so, claim your 15 minutes of fame at the virtual Sensors Innovation Fall Week event....
Oct 23, 2020
[From the last episode: We noted that some inventions, like in-memory compute, aren'€™t intuitive, being driven instead by the math.] We have one more addition to add to our in-memory compute system. Remember that, when we use a regular memory, what goes in is an address '...

featured video

Demo: Inuitive NU4000 SoC with ARC EV Processor Running SLAM and CNN

Sponsored by Synopsys

See Inuitive’s NU4000 3D imaging and vision processor in action. The SoC supports high-quality 3D depth processor engine, SLAM accelerators, computer vision, and deep learning by integrating Synopsys ARC EV processor. In this demo, the NU4000 demonstrates simultaneous 3D sensing, SLAM and CNN functionality by mapping out its environment and localizing the sensor while identifying the objects within it. For more information, visit inuitive-tech.com.

Click here for more information about DesignWare ARC EV Processors for Embedded Vision

featured paper

Overcoming PPA and Productivity Challenges of New Age ICs with Mixed Placement Innovation

Sponsored by Cadence Design Systems

With the increase in the number of on-chip storage elements, it has become extremely time consuming to come up with an optimized floorplan using manual methods, directly impacting tapeout schedules and power, performance, and area (PPA). In this white paper, learn how a breakthrough technology addresses design productivity along with design quality improvements for macro-dominated designs. Download white paper.

Click here to download the whitepaper

Featured Chalk Talk

Evaluation and Development Kits

Sponsored by Samtec

With signal integrity becoming increasingly challenging in today’s designs, interconnect is taking on a key role. In order to see how a particular interconnect solution will perform in our design, we really need hands-on evaluation of the technology. In this episode of Chalk Talk, Amelia Dalton chats with Matthew Burns of Samtec about evaluation and development kits for high-speed interconnect solutions.

More information about Samtec Evaluation and Development Kits