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grodius

TI OPT8241 Time of flight QVGA 3D sensor

8 posts in this topic

This is a quite exciting new sensor. The development kit is prohibitively expensive and the chip driver is 256BGA, but at around $50 for the raw sensor capable of 150 fps of 320x240 with distance, this is cool.

 

Time of flight pulses out light/IR and counts the sub nanoseconds it takes to bounce back.

 

The specs are pretty impressive for an early model.

 

http://www.ti.com/product/OPT8241

 

Ideally I would prefer the device and driver chip were paired on a board, but hopefully these will be popular and warrant more integrated solutions.

chicken, bluehash and pine like this

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I'd never heard of ToF arrays. Really interesting way to create a 3d camera.

 

Here's the application diagram from the datasheet.

post-274-0-08711800-1463992176_thumb.png

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The 2nd generation Kinect that shipped with the Xbox One uses time of flight to calculate depth. There's a nice summary of the method here: http://www.gamasutra.com/blogs/DanielLau/20131127/205820/The_Science_Behind_Kinects_or_Kinect_10_versus_20.php. It also explains the structured light system used in the original Kinect and compares the pros and cons of each system.
 
Regarding the sensor and controller being separate chips, I think that may be unlikely to change. The sensor is made using a "chip on glass" process which I suspect isn't ideal for the controller. Also, keeping the controller off the sensor die avoids any problems with it heating the sensor (which would increase the noise level).
 
EDIT: About 30 seconds after posting this I found the OPT8320, which does integrate the controller and framebuffer memory into a single CoG package. That one's only 80x60 pixels, however.

chicken and greeeg like this

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80x60 at 1000fps sounds cool. I wonder what one could do with these... Ping Pong robot?

 

The package is BGA, but only one row around the edge with 0.45mm pitch. Should be doable with regular PCBs from OSHPark et al.

spirilis likes this

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The package is BGA, but only one row around the edge with 0.45mm pitch. Should be doable with regular PCBs from OSHPark et al.

 

For the Sensor yes. But it requires a secondary co-processor (OPT9221) a 256NFBGA. Which requires a 144MHz DDR2 memory interface. The datasheet recommends a minimum 6 layer PCB.

 

Still do-able if you really wanted to. But does kinda push it outside of a weekend project territory. :P

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The package is BGA, but only one row around the edge with 0.45mm pitch. Should be doable with regular PCBs from OSHPark et al.

 

Then comes the really tricky bit, optical alignment... the lens assembly needs to be centred over the sensor array (which is not centred within the package).

 

Also I just noticed in the datasheet that the mounting isn't just at the BGA pads. You're expected to use a non-conductive underfill to thermally bond the bulk of the package to a copper pour for heatsinking and stabilisation.

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It's more complex, but not too far removed from the Tindie for the ADNS-9800 laser mouse. Some bright enterprising spark might put together a hyper breakout. I'm mainly pleased that the early models are already very fast and high res.

 

I personally really wish micromouse competitions forced the pros to use ONLY visual recognition and/or new tech. Micromouse comps are over-ripe slotcars now where sensor development and experimentation might be fun.

 

It's worth just thinking about devices like these. I like the thought that you might only need one array receiver and maybe multiple light sources in sequence to triangulate or for redundancy/data improvement.

tripwire likes this

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