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3D image acquisition

Philip Ashmore
Prodigy 150 points
Other Parts Discussed in Thread: ONET1151M, ONET8501T, ONET8501V, ONET1101L

Hi there.

I'm exploring the use of the "11.35-Gbps Differential Modulator Driver with Output Waveform Shaping" http://www.ti.com/product/onet1151m

with the "11.3 Gbps Limiting Transimpedance Amplifier With RSSI" http://focus.ti.com/docs/prod/folders/print/onet8501t.html

The idea is to use rotating mirrors to raster scan a scene and use a beam splitter to work out time-of-flight for each point in the scene.

I'm hoping for a 60 scans per second of 1920x1080 distance measurements in the 5mm-5cm distance range, which I plan to convert into a full HD video stream, with the red, green and blue components combined to produce a 24 bit distance matrix for the scene.

By knowing the mirror angles and the pixel location I can work out the time of flight between the mirrors and determine the round trip time for each pixel independent of its location.

Then I'll use the corrected image to generate a 3D representation of the scene as a point cloud and develop some algorithms to reconstruct the original scene.

Is there an application note for the above devices together, such as a schematic or video, with the part numbers of the emitter/detector + associated circuitry - something I can work off.

Can anyone see any glaring problems with this approach?

Regards,

Philip Ashmore

  • 0
    TI__Expert 8915 points

    Philip,

    This application is quite different from the standards based specifications (10G Ethernet, SONET, Fibre Channel)  for which the parts were designed for. We do not have the experience to comment on the use of the devices for such an application.

    However, if the distance if fairly small, you may consider using the ONET8501V VCSEL driver or ONET1101L DFB laser driver instead of the ONET1151M. The ONET1151M is a Mach Zehnder modulator driver for 40 to 80 km applications over fiber. I would think that you would want to directly modulate the laser, not use an externally modulated laser. Recommended schematics for the laser drivers and TIA are provided in the datasheets and should be used as a guideline.

    There are many possible sources for the lasers and detectors, some being Cyoptics, Renesas, JDSU, Finisar, Mitsubishi, Sumitomo, Optowell and Truelight. I think you first need to decide if you will implement the system using 850nm VCSELs or 1310nm FP/DFB lasers.

    Regards,

    Alex.

  • 0 in reply to Alex Davidson
    Prodigy 150 points

    I'm new to the field so bear with me.

    If I understand correctly, the devices mentioned are like serial ports and what goes over the line includes synchronization bits.

    I originally thought you'd need circuitry to drive the emitter/ condition the detector output but these devices also handle the protocol layer.

    That being the case, you're right - I need something simpler.

    Tracking down VCSEL or DFb samples is proving difficult.

    Hasn't anyone tried using fibre-comms tech for distance measurement?

    Regards,

    Philip Ashmore

  • 0 in reply to Philip Ashmore
    TI__Expert 8915 points

    Philip,

    Using standard fiber communications products for distance measurements is not new but the requirements may be quite differnet. I think for distance measurements, the rise time from the laser is important for accuracy and fairly large currents may be needed if the reflected signal is not strong. In your case the distance is quite short so you may not require a large optical power.

    I found some useful background information here:

    http://herkules.oulu.fi/isbn9514269667/html/c305.html

    Also, we just provide the drivers for the lasers and the transimpedance amplifiers for the photodiodes. We do not design the optical system itself.

    Regards,

    Alex.

  • 0 in reply to Alex Davidson
    Prodigy 150 points

    Thanks for your help!

    That link is certainly food for thought.

    Regards,

    Philip