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I have an issue to solve. I'm going to measure an object that looks like this.

My question is if the sensor VCNL4040 have a very wide spread light or very "laser-like" light that concentrates everything in a small area? Because I have walls that I don't want to measure at.

enter image description here

VCNL4040 using an IR-led that consumes 200mA Datasheet: https://www.vishay.com/docs/84274/vcnl4040.pdf

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    \$\begingroup\$ Consult the Vishay publication Designing the VCNL4040 Into an Application \$\endgroup\$
    – ErikR
    Commented May 25, 2021 at 12:05
  • \$\begingroup\$ @ErikR Thank you! \$\endgroup\$
    – euraad
    Commented May 25, 2021 at 12:25
  • \$\begingroup\$ Datasheet (oddly) doesn't show the IR sensor spatial response or say how closely it relates to the ALS spatial response (fig 8) : if I had to guess, I'd use the same graph. Which means the spatial response is dominated by the IR LED response (fig 10) as long as you can keep ambient IR down. \$\endgroup\$
    – user16324
    Commented May 25, 2021 at 12:29

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It is obviously a wide angle detector (Lamertian 160 deg) with no lens, so if 2m reflection is the limit from a large white board, you must create an aperture and lens if you need to go further and block stray reflections. But 1st you must define the range of target and reflectivity for IR and same for non-target.

So define geometry and optical parameters in order to design reflective signal and noise ratio. There are better ways if needed.

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  • \$\begingroup\$ In this case, I'm only going to measure between 0-200mm \$\endgroup\$
    – euraad
    Commented May 25, 2021 at 14:03
  • \$\begingroup\$ Do you recommend it? The sensor. \$\endgroup\$
    – euraad
    Commented May 25, 2021 at 14:04
  • \$\begingroup\$ No. No answer is possible without design specs. Or until you answer my questions with exactly what you are trying to measure and what you measure as an error. \$\endgroup\$
    – D.A.S.
    Commented May 25, 2021 at 14:16
  • \$\begingroup\$ Well, I'm trying to measure a distance, but I don't care about the unit. As long I get repeatability and accuracy, that's good enough. I'm trying to measure a solid square profile about 20x20mm. The profile is about 100mm long too. \$\endgroup\$
    – euraad
    Commented May 25, 2021 at 15:17
  • \$\begingroup\$ Sorry but you have said nothing about reflectivity and stray reflectivity geometry and any other stray light 20x20 mm at 100m length is about 7% of the emitted cone area. Do a proper design spec in your question. \$\endgroup\$
    – D.A.S.
    Commented May 25, 2021 at 15:50

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