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OPT8241-CDK-EVM: Max distance believable?

James May
Prodigy 40 points

Part Number: OPT8241-CDK-EVM

With the 3DToF system estimator, I am able to get 100m max distance using say 50-80MHz modulation frequency, and DeAlias not enabled. 500mm depth resolution. Yes, it requires lots of light as expected. I don't understand how the chip is able to resolve distances this far unambiguously without dealiasing. Can you explain?

  • 0
    TI__Expert 3495 points

    Hi James,

    System estimator tool is mostly a power calculator, telling you the power needed to detect object placed at a given distance within some given tolerance.  But your point is well taken--the tools output should take into account the c/(2*f) theoretical limitation.  Notice that there is only one frequency setting in the tool, not two.  If de-aliasing is enabled, to estimate power, use highest frequency of the two, and use f = GCD(f1, f2) for frequency.

    -Larry

  • 0 in reply to Larry Li
    Prodigy 40 points

    Hi Larry,

    Thanks for the reply. It makes more sense now, but in light of your answer, I have more questions:

    1. When I check the Dealias enable box, power goes up by ~50%. Since the tool doesn't know the second frequency, is this figure correct, or is this figure based on some hidden assumption?
    2. Since the tool allows a max setting of 100m, can you confirm the chip supports a frequency pair that will allow this, such as 50MHz and 51MHz or 80MHz and 81MHz?
    3. Can the two frequencies be chosen arbitrarily? The data sheets don't seem to specify this.

    Assuming a lot of light, I am still not confident my project requirements of 50m to 100m range can be met with this chipset. Can you confirm?

    James

  • 0 in reply to James May
    TI__Expert 3495 points

    James,

    1. When I check the Dealias enable box, power goes up by ~50%. Since the tool doesn't know the second frequency, is this figure correct, or is this figure based on some hidden assumption?

    >> To compute power consumption, use average of f1 and f2.  To compute accuracy, use f2 (higher frequency of the two).

    1. Since the tool allows a max setting of 100m, can you confirm the chip supports a frequency pair that will allow this, such as 50MHz and 51MHz or 80MHz and 81MHz?
    2. Can the two frequencies be chosen arbitrarily? The data sheets don't seem to specify this.

    >> The two frequencies cannot be chosen arbitrarily.  See attached spread sheet--it is a tool for doing that.    In particular row highlighted in green is one you can use to get to 100m, theoretically.  However, 100m requires lots lots of power, so there will be other practical limitations that come into play.

    DealiasCalc_v2.xlsx