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OPT3101: Simultaneous reflection from multiple media at different distances

Danilo A.
Mastermind 28680 points
Part Number: OPT3101

Hi Team,

Our customer would like to know whether or not the OPT3101 can handle simultaneous reflection from multiple media at different distances. For example when using this chip for finding the range of a transparent sheet of a glass, would the chip output both the distance of the glass and the object behind it?

Regards,

Danilo

  • 0
    TI__Mastermind 28680 points

    Hi Team,

    Additional inquiry from the customer, besides a sheet of glass, they would like to know how this chip would react to stable water surface. They would like to know if it can capture the reflection both from water surface and bottom of water. 

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Mastermind 25895 points

    Hi Danilo,

    OPT3101 is single pixel per channel and so will only output a single value. If there are multiple reflections then they will be averaged together. As such, OPT3101 does not work well for glass or water.

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    TI__Mastermind 28680 points

    Hi Alex,

    Thank you for the clarification. We have received a follow up question from the customer as follows.

    Thanks for the experiment. It is understandable that this solution could not works well for water or glass. But let me confirm one more question and this case would be closed. In case of two reflections are received, would the two reflections be averaged before receive, or it would receive two reflections and they both be averaged by filter? If they would be averaged by filter, could the filter be adjusted to get both reflection results? For example, the reflection from bottom is received and the result is 150cm, another reflection from water surface is received and the result is 130cm. Would they be averaged as a value between 130cm and 150cm, or there will be value switching from 130cm to 150cm?

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Mastermind 25895 points

    Hi Danilo,

    This seems to be talking about receiving two reflections at two different times due to them being different distance away (130 vs 150cm). Since OPT3101 is continuous time of flight it is not sending a pulse that can then be received and will switch in time. Rather the phase shift is computed between two continuous waveforms at the tx and rx. This will be an average corresponding to the phase of the two distances weighted by the strength of each signal.

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    TI__Mastermind 28680 points

    Hi Alex,

    We have received further questions from the customer.

    So, in the case where there are two different reflections from a single pulse of light,
    the incoming signal as perceived by the sensor will be one mixed signal of the two reflections.
    Is my understand correct?

    Also, regarding your previous replies, were your conclusions based on the working principle of OPT3101 alone?
    In other words, no actual experiment was conducted at TI for your conclusions. Is this correct?

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Mastermind 25895 points

    Hi Danilo,

    These types of questions are covered by the theory section of our system design doc https://www.ti.com/lit/ug/sbau305b/sbau305b.pdf

    This is covered by the operation of the device. It has also been confirmed in testing.

    Best,

    Alex