Monday, June 02, 2014

Rumor: ST Supplies SPAD-based ToF Autofocus for LG G3 Smartphone

The newly announced LG G3 smartphone features an intriguing piece "Laser Auto Focus measures the distance to the subject using laser technology. Laser Auto Focus allows for improved focusing speed and object detection in low-light situations." I was told that this AF utilizes STM's SPAD-based ToF range finder. A similar SPAD device is also used in a low-end Bosch laser distance measurer PLR15.

If true, the SPAD ToF technology finds its way to more and more mass market devices: first to ST proximity sensor, then to Bosch distance meter, and now to LG G3 flagship smartphone.


  1. SPAD+ToF in a phone -- awesome! Nice work ST (if true)!

  2. When I read "laser auto focus" and see the picture of the product, my guess would be that they simple project an infra-red laser point in parallel to the optical axis of the lens. The closer the object, the more off-center the point will be in the image. I guess the precision will be more than enough for smart phone usage (i.e. quite high depth of field). (Beside above, I have no knowledge about the product, maybe it is really TOF...)

  3. On the ST website you may find the preliminary datasheet of VL6180, aTime-of-Flight (ToF) proximity sensor based on VCSEL. The working range is just 50cm but it is enough to adjust the focus in the near field.

  4. The VL6180 does not allow multi-point AF, which seems to be the case on some videos. I think that it relies on a trinagulation principle with a laser projector equipped with a beam splitter (diffractive optical element for instance) in order to generate multiple laser beams. The position of each laser spot within the captured images helps to determine the right focus for each region of interest. Such active AF principle is insensitive to motion blur, low contrasted scenes, low lighting and it is very fast. Only 2 or 3 frames are required to find the best focus against tens of frames for a regular passive AF. This is already used in professional cameras aimed to quick data capture (patent WO2008027316).

  5. And another approach for focusing:

    Under 7/23 statement:
    "Imaging, Bi-CMOS, ASIC and Silicon Photonics (IBP)
    Started volume shipments of the time-of-flight proximity sensor for the widely acclaimed LG G3 smartphone that began its global rollout from the second quarter of 2014."


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