4 Replies Latest reply on Jul 9, 2018 10:23 AM by rjo___

    Is it possible to get ~2mm accuracy when scanning a foot? (using two or three D435)

    ShacharWeis

      Hello all,

       

      I need to build a foot scanner and the client requires 2mm or less accuracy. I was thinking of using two or three D435 cameras. The user will be wearing a sock while scanning.

       

      Is this feasible?

       

      Thanks.

        • 1. Re: Is it possible to get ~2mm accuracy when scanning a foot? (using two or three D435)
          MartyG

          The first problem that you might have is that if the customer that is being scanned is wearing black or grey socks, the camera may have difficulty in seeing the foot because these dark colors absorb laser light so that area of the foot cannot be used in the image.  You might therefore end up with large areas of black on the image where the sock should be.

           

          Also, if you are scanning at very close range with a 400 Series camera then you may experience a loss of accuracy compared to if you were scanning further away.  This is because of the pixel scale that is used to enable these models to 'see' up to 65 meters (though depth scans are limited to 10 meters).  You can change the scale factor of the camera though for greater accuracy at very close range.

           

          Re: Problem aligning color to depth

          • 2. Re: Is it possible to get ~2mm accuracy when scanning a foot? (using two or three D435)
            ShacharWeis

            Good point about black socks. I'll take that up with the client.

             

            What distance would be optimal for getting best accuracy? Do you think that 2mm is possible?

             

            Thanks.

            • 3. Re: Is it possible to get ~2mm accuracy when scanning a foot? (using two or three D435)
              MartyG

              Under optimal conditions, the depth accuracy of the 400 Series is less than one percent of the distance from the object, so mm accuracy will depend on distance, and the aforementioned depth scale of the camera..  This is quoted in the documentation link below:

               

              Depth Resolution of Intel® RealSense™ Depth Camera D435 and Intel®...

               

              A user on the Librealsense forums said: "Here are a list of parameters that I found effective at manipulating depth resolution at close range.  I'm using the D415 camera and not the D435 so things might be slightly different.  In no particular order:"

               

              Exposure

              Gain

              Laser Power

              DS neighbor threshold

              Estimate mediam decrement

              score maximum threshold

              depth units

              disparity shift

              depth clamp max

              depth clamp min

              • 4. Re: Is it possible to get ~2mm accuracy when scanning a foot? (using two or three D435)
                rjo___

                There are going to be a lot of questions like this:)

                 

                The short answer should always be "yes, but..." 

                 

                For example, with feet at accuracy on the micron scale... not mm... microns:), no problem.

                 

                ... BUT to get that kind of accuracy you have to move the D4_ _ closer... which cuts down the field of view.   There is no problem getting the D400 series cameras closer than the spec... you just increase the disparity shift until you are happy.

                Applications are always going to be settings specific.  First one to the right specs for the right application wins the prize!!!

                 

                "What" you need to do with the data largely determines how you acquire it... you can do just about anything...

                But (right now) you have to be pretty stubborn and goal oriented:)  Study the updates... the RealSense team implements a lot of requests, but doesn't say much about them.

                 

                Regards,

                 

                Rich