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VL53L1X is a Time of Flight sensor, it measures distance via pulsed laser or so I understand. But upon reading its specs it has a field of view of max 27 degrees which is quite confusing for me. I thought it uses laser should only read objects that are relatively straight ahead, it is even has a wider field of view than some ultrasonic sensor.

Does this mean that I can get the angle of the location of the object? It would be great if that were the case or I can only get the distance and I won't be able to identify where in the 27 degrees is the object.

This line:

The VL53L1X also features a programmable region of interest (ROI), so the full field of view can be reduced or divided into multiple zones

I don't understand what this line implies

I was planning to buy 3 of them so I can arrange them in a straight line and be able to track an object.

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  • \$\begingroup\$ did you read the whole web page that you linked in ypur post? \$\endgroup\$
    – jsotola
    Commented Jan 23, 2020 at 20:17
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    \$\begingroup\$ Interestingly, coherent light is part of the definition of a laser but a collimated beam is not. Coherency just makes it easy to produce a collimated beam. Gas lasers need optics (mirrors) to work and these also collimates the beam for us but it need not be so as is the case with diode lasers. In fact, with diode lasers the beam angle is often different horizontally and vertically by ~2 times. Extra optics are required to collimate the beam on laser diodes and every laser pointer you see has them so it's easy to forget lasers don't always mean collimation. \$\endgroup\$
    – DKNguyen
    Commented Jan 23, 2020 at 20:21
  • \$\begingroup\$ @DKNguyen i apologize i still dont get the principles how this sensor work. I have read what coherent and collimated light means, but i am having trouble connecting the dots. The link mentioned 265 detection elements So if the light coming out the sensor is coherent and not so collimated meaning the light will spread out a little bit and whatever it hits gets reflected back to the sensor. So this implies that the correct assumption is my second one ?? what does the zones do ? \$\endgroup\$
    – Jake quin
    Commented Jan 23, 2020 at 20:53
  • \$\begingroup\$ @jsotola i think i did , but i dont think i fully understand what i have read \$\endgroup\$
    – Jake quin
    Commented Jan 23, 2020 at 20:54
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    \$\begingroup\$ @Jakequin Yes, the beam spreads out. The total beam is 27 degrees but can be subdivided up into little pizza slices so you can tell where something is more precisely than if it was just a single 27 degree cone. It means that if you set the sensor far enough away perpendicular to the motion of the object's straight line of travel, and you KNOW it only moves in a straight line, you can track the position of the object with just one sensor. \$\endgroup\$
    – DKNguyen
    Commented Jan 23, 2020 at 20:59

2 Answers 2

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All lasers put out a fairly wide "cone" of light. If you want a narrow beam, you have to put a lens on the end of your laser. Usually the manufacturers provide this automatically. If you want the natural beam, you have to ask for a laser which doesn't have any built-in lens. (Laser light is monochromatic point-source light. It need not be collimated/parallel light.)

As far as I can determine, the above simple facts are never taught in any grade-school science book, where instead they insist that lasers always put out parallel beams. (No, HeNe lasers don't. They have "confocal" cavities, with sphere-wave output. Neither do diode lasers, with their tiny cavities and wide-diffracted beams. Both have a lens, otherwise the natural laser beam would be spreading.) But in the above type of sensor, its IR diode-laser is probably being spread out even wider than its naturally-wide, cone-shaped beam.

Look at the ST corp datasheet PDF. Basically, this sensor has a 256-pixel camera inside it, ultrahigh-speed pixels. Its microprocessor can disable all but a certain number of them. This lets you program the "view" which the device actually sees, with 4X4 (16 pixel) minimum, and 16x16 (256 pixel) maximum.

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The sensor has a programmable region of interest (ROI) that can be used to set the direction of the beam to some degree.

I don't know if it works. I have only used the sensor for normal distance measurements. The readings you get from the sensor is quite accurate if configured correctly. It becomes even better if you add a special cover glass.

You don't get an angle to the object. Only the distance and a measure for how strong the received signal is and how much ambient light is present.

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  • \$\begingroup\$ If you dont mind i ask may i know what type of cover glass is that? i dont think i will be using it but it is good to know. So can i assuming that if the signal is not very strong then the object must not be directly ahead of the sensor? \$\endgroup\$
    – Jake quin
    Commented Jan 23, 2020 at 21:00
  • \$\begingroup\$ @Jakequin It is a special glass with a slot between the the transmitter and receiver. It prevents crosstalk between the two. It is manufactured by a company called Hornix Optical Technology. They have different cover glass models for the ST optical ranging sensors. \$\endgroup\$
    – Peter Karlsen
    Commented Jan 24, 2020 at 6:50

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