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I need a sensor to measure the distance between itself and an object (which is my finger). What is a good sensor that can accurately measure such distance within about less than half a meter?

I think it would be an infrared sensor or an ultrasonic sensor.

Also I need it to sweep as much horizontal distance as possible. I need to stack them beside each other to cover a plane.

Edit: The horizontal distance is about 30 cm. Also note that it shouldn't be too expensive and the quality needed can be "not so perfect" it's okay. Assume it's for an experiment.

My question is mainly about what type of sensor should I look for

...if a finger is too small for most sensors, then it's okay to replace it with a bigger object so that the sensor can detect it.

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    \$\begingroup\$ Most IR and ultrasound sensors that I know of will probably not deal very well with having to detect "a finger". Its too small of an object at half a meter. Did you actually mean that or it was a figure of speech? Also, how much is "as much horizontal distance as possible"? Have you considered using a LIDAR in the orientation you desire? \$\endgroup\$ – Wesley Lee Nov 29 '16 at 17:21
  • \$\begingroup\$ Also take a look into Leap Motion. Not sure if will go up to 50cm but it tracks fingers very well if compared to IR/ultra-sound. p.s.: also flagging for being off-topic since its a product recommendation question. \$\endgroup\$ – Wesley Lee Nov 29 '16 at 17:22
  • \$\begingroup\$ @WesleyLee not a figure of speech. about the horizontal distance I think it should be about 30cm. as for IR & ultrasonic; I don't know what type of sensor I should pick. That's exactly what the question is about. We need a sensor for the stated requirements. I'm just mentioning some advice I got. \$\endgroup\$ – Mina Michael Nov 29 '16 at 20:06
  • \$\begingroup\$ This isn't a design service, and product searches are discouraged. Why? Because we all have access to google. electronics.stackexchange.com/help/how-to-ask \$\endgroup\$ – Voltage Spike Nov 30 '16 at 0:06
  • \$\begingroup\$ answer: friend studied image processing for MS degree. In that work, he computed the behavior of OFFSET photodiodes. That offset causes a useful hint to the distance-measuring math. I verified this, using only 1inch of offset, and taking the LOG of voltages using diodes. At 6", using materials as differently reflective as white paper and dark-blue washcloth, the difference between the diode voltages remained constant. Topo? two photodiodes, reverse-biased, into 2 forward biased small-signal diodes. \$\endgroup\$ – analogsystemsrf Feb 26 '17 at 21:19
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If you're talking about a finger, and you need distance and not position, you might try a capacitive proximity sensor, like that used in a Theremin.

See the pdf at http://www.cypress.com/file/95206/download for some background

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  • \$\begingroup\$ Does a proximity sensor give the distance or just the presence of an object in the field? We need the distance \$\endgroup\$ – Mina Michael Nov 29 '16 at 20:17
  • \$\begingroup\$ You can infer the distance from capacitance. So if the finger is closer capacitance change will be more significant. Theres a problem however that you can't tell a very large object that is far away from a small object that is close with a single sensor though. \$\endgroup\$ – Wesley Lee Nov 29 '16 at 20:32
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You could try with 2 wired capacitance sensor like shown in the picture. With 2 wired sensor you can adjust the sensors's detection range. How? With resistor; as you are changing the value of resistor also changes the detection range - to some point in a space. As you get closer or further, the inner capacitance changes and with that the voltage drop on sensor. That's why you connect your output stage in parallel.

*Just watch out that you don't connect too small (at least 1kOhm-depends on sensors current capabilities) resistor or your sensor gets short-circuited!

enter image description here

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