Camera which measures distance?

  • #1
clm222
Hi all,

I'm having trouble finding something online which isn't a very complicated device, but I don't know if it has a specific name, which would help me in a google search.

I have a motor in an MBE which moves the sample, and I need a camera which can read to a computer what the distance is from the lens to whatever it sees, which is the arm attached to this motor. So I guess it might need a laser since it only needs to see the spot directly in front of the camera. The needed distance is only about 5ft or under.

Is there a name for these devices? I've tried several search terms and have found nothing. It only needs to be accurate to about 5mm or so.

Thanks.
 
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Answers and Replies

  • #2
berkeman
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I have a mortar in an MBE
What's a mortar? And and MBE?

Can you Upload a picture of your setup, or a drawing? The auto-focus information from your camera may be all that you need, if it can be read out...
 
  • #3
clm222
What's a mortar? And and MBE?

Can you Upload a picture of your setup, or a drawing? The auto-focus information from your camera may be all that you need, if it can be read out...

Sorry I meant "motor" not "mortar", and MBE stands for Molecular Beam Epitaxy, which is a process to grow lattices. The MBE machine has a vacuum chamber, where one end of the chamber builds the lattice, but the other end of the chamber examines the lattice.

In this attached image is a rough sketch of the setup, where the sample is inside the MBE, attached to an arm which is moved left or right by the attached motor. I want a device (labelled in the sketch) to measures the distance X between the device (which is static and adjacent to the MBE) and the arm backboard (which moves left or right with the arm).
 

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    mbe drawing.png
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  • #4
berkeman
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I'm not seeing an attachment yet... :smile:
 
  • #5
clm222
I'm not seeing an attachment yet... :smile:
sorry, I just attached it after I'd replied
 
  • #6
berkeman
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I'm not quite understanding the setup, but could you mount a 45-degree mirror on the arm and run a ruler parallel to the arm? The camera would be able to read the numbers on the ruler in the reflection on the mirror.
 
  • #7
berkeman
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Guess you would have to write the numbers on the ruler in mirror image format... :smile:
 
  • #8
clm222
Guess you would have to write the numbers on the ruler in mirror image format... :smile:
Well we're wanting to hook up the device directly to the computer. The motor is run through LabView, and we want LabView to be able to read a number from the device in order to give instructions to the motor. Like just a device which measures the distance from it to whatever it's looking at, and can feed that value to LabView.
 
  • #9
clm222
I'm just not sure what those are called, but once I get a name I can google it
 
  • #10
berkeman
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Do you have a software package that can read numbers on the camera? Does the camera need to read anything else, or it is just used for sensing the position?

If you can't read numbers with the camera, can you count the number of lines passed or something?
 
  • #11
berkeman
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Also, your drawing shows part of the arm sticking out of the MBE vacuum chamber? Can you just put a linear encoder on that part of the arm to tell what the change in position inside the chamber is? What kind of vacuum feedthrough is used with the arm?
 
  • #12
rbelli1
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What accuracy and repeatability do you need?

BoB
 
  • #13
728
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It does depend on the accuracy you want but we have used the Kinect camera from the Xbox for many of these sort of jobs. From memory if you look at the raw data you can get 1mm sort of accuracy from them.
 
  • #14
clm222
Do you have a software package that can read numbers on the camera? Does the camera need to read anything else, or it is just used for sensing the position?

If you can't read numbers with the camera, can you count the number of lines passed or something?

I'll ask the postdoc I work under about the linear encoding (in your other comment), and I'm not sure how the software will work out, but ideally the camera will just return a real number of an integer or natural. The motor is old, and cannot take a single move command else it breaks, so we need to send it many commands to move a small distance many times. I want to wright a code that sends the move command, then reads the number from the camera, checks to see if it's within a certain difference of the desired position, then either stops commanding the motor to move, or continues to order the motor to move. I'll ask my postdoc about the specifications. Thanks for the help so far!
 
  • #15
clm222
As for accuracy and repeatability, it needs to be within about ~1cm or less
 
  • #16
728
169
As for accuracy and repeatability, it needs to be within about ~1cm or less

I think the Kinect can probably do this with its standard software which gives a colour map for distance, but it will do down to millimetres if you analyse the raw data and there are software bits and pieces to do that.
 
  • #17
rbelli1
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A simple one pulse per rotation would do as long as one rotation is less than a few mm. Some options are reed switch, opto interrupter, or even a micro-switch if the rotation speed is small. You will need to have some way to reorient to absolute on powerup.

BoB
 
  • #20
russ_watters
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  • #22
russ_watters
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Yikes, buyer beware. :nb) That sounded interesting, so I followed the link. At the bottom of the page is the following customer feedback comment.
Oops...well they do offer the laser distance meter too.
 

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