Measuring transitional and rotational movements.

Measuring movement is essential in many experiments. Although measuring a transitional movement is rather easy, rotational and random movement are challenging! One the other hand, measuring with laser is expensive and sensitive. However, by using a simple camera it is possible to track shapes and colors. This has been used in many industries specially for car accident test. 

To measure a rotating object around a shaft, i used a camera to capture images of an indicator with four circles:

    

The image processing is done in Matlab software. The code starts to find the smallest circle first and saves the location as the shaft center. Then draws a line to other circles and finally measures the rotation by simple trigonometry.  processed image

A sample processed image


It is also possible to track colors in Matlab. The following movie shows tracking of the red rectangle for measuring the deflection of device. Here the blue text shows the deflection in mm:

 

Needles to say, calibration is necessary in this method and it should be done every time the camera (reference point) moves. 

The Matlab code for tracking circles can be downloaded from here.