Of course you can use any of the standard photogrammetric tecniques and programs. Even you can do it automatically using image correlation to find the paralax and hence the distance.
But I have a simpler and cheaper (and also accurate) solution: Put a transmiting coil in the object to be measured, about 1-2 cm diameter, 0.5 cm high (I don´t remember the frequency now, it is quite low but it doesn't matter). Lay a receiving antenna grid of vertical and horizontal wires, spaced about 1 cm, in a surface below the object. Scan the antennas noting the amplitudes an phases on the 4 or 6 horizontal and vertical wires surrounding the Tx coil in each moment . Calculate the position in real time (you obtain a precision of about 0.1 mm if the antenna surface is calibrated) Sound complicated? buy a digitizing tablet (used ones are really cheap). This is how these things works. Regards, Ignacio Cembreros Lux, James P wrote: > There's a fair amount of F/OSS software from JPL available to do this sort of > calibration. It's used to calibrate cameras used on Mars rovers, among other > things. The target pattern for calibration is a bunch of big circular dots on > a background. > > > On 11/23/08 7:56 PM, "Bruce Griffiths" <[EMAIL PROTECTED]> wrote: > > Tom Van Baak wrote: > >>> I need to determine the position of a instrument with a 1mm accuracy or >>> less. >>> The instrument is not connected to a mechanical device but is separate & >>> independent. >>> The surface which the instrument is positioned on is close to the size of a >>> 11"x11" square. >>> >>> >> 1 mm or better accuracy on a 300x300 mm surface can be >> obtained with a cheap webcam mounted above the surface >> and a little bit a creative software. >> >> /tvb >> >> > Dont forget to calibrate the camera distortion and ensure that this > doesnt over over time. > > i.e. lock the focus and ensure the camera position, tilt etc with > respect to the reference surface do not vary. > > Bruce > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
