OPT3101: Distance calculation

Nic

Part Number: OPT3101

Team,

I am reading below document for TOF distance calculation.

http://www.ti.com/lit/wp/sloa190b/sloa190b.pdf

However, I found that the distance calculated from eq.1 and eq.2/3 is different. From my understanding, they should be the same since the plot in figure.2 is the same.

Take Q1=10, Q2=90, Q3=60, Q4=40 as example. (From figure 2, we can get Q4=(Q1+Q2)/2-Q1, Q3=(Q1+Q2)/2+Q1, ∆t=1/f)

Use eq1, a=Q2/(Q1+Q2)=90/(10+90)=0.9

Use eq2, b=/2pi= arctan[(60-40)/(90-10)] /(2*3.14) =2.23

I don't understand why a doesn't equal b. Could you let me know the reason? Thanks.

Regards,

Zhihong

over 5 years ago

0 Praveen Aroul over 5 years ago

TI__Mastermind 49956 points

Hi Zhihong,

Welcome to TI E2E forum!

Thank you for evaluating the OPT3101.

We will look at your questions related to the TOF distance calculation and get back to you early next week.

0 Alex Bhandari-Young over 5 years ago in reply to Praveen Aroul

TI__Mastermind 25895 points

Hi Zhihong,

This document is for 3D time of flight. For OPT3101 please refer to this link for documentation.

https://e2e.ti.com/support/sensors/f/1023/p/815766/3019009#3019009

System design doc has the most theory on technology.

Best,

Alex

0 Nic over 5 years ago in reply to Alex Bhandari-Young

Prodigy 80 points

HI Alex,

Yes, it is for 3D TOF. But no matter it is 3D or 1D, the basic theory is the same. I do think that they used the same theory to calculate the distance. Just wondering why the 2-Quad and 4-Quad calculated result is different.

Regards,

Zhihong

0 Karthik Rajagopal over 5 years ago in reply to Nic

TI__Prodigy 330 points

Zhihong,

These are completely different systems (2 Quad and 4 Quad). You cannot relate the two and expect the same results. The 2 Quad system would yield a phase result based the ratio of the signal collected on the quads and the relative ratio between the two. In case of the 4 quad system the arctan function as listed in the document would yield the phase result. The arctan function here assumes that one of the modulation or illumination waveforms is sinusoidal. Hence both methods cannot be compared apples to apples.

thanks

Karthik

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OPT3101: Distance calculation