#PHASE SHIFT HOW TO#

Otherwise, you should calibrate the gamma value using gamma_correction.py and correct sinusoidal patterns in advance. The sine and cosine functions both have periods, but what is the period The period moves from one point to the. Amplitude indicates the movement of values from the centerline of the graph to the peak (top) and the trough.

#PHASE SHIFT HOW TO#

Thus, if your devices are gamma adjustable, set their gamma value to 1.0. How to Calculate the Phase Shift Amplitude. However, most of imaging and display devices transform their input values based on their gamma value (in general, display : 2.2, camera : 1/2.2). The phase-shifting method requires that the input value to the display and the output value from the camera are linear. Global position is computed using the phase, phase difference and graycode coordinate complementarily.īefore generate patterns, you should calibrate the gamma values of your display-camera system.Compute coordinate of the corresponding display pixel.The average of decoded coordinates of neighbouring pixels is set with the kernel size.Mask is computed by dilating and eroding with user-defined kernel size 2*filter_size+1.Interpolation is required for pixels on the border of graycode patterns.Decode and interpolate the graycode coordinate on the GC map.Compute the phase difference (it is not a simple subtraction between unwrapped values).įor each camera pixels, the coordinate of corresponding display pixel are estimated by the following process. The periods of these patterns are defined as follows with user-defined parameter step. Implementation in this repositoryĪlthough there are some derivative methods, I implemented the 3-step phase-shifting method which is the simplest one.Īlso, to obtain the global position of each cycles, I combined graycode patterns and two sets of sinusoidal patterns whose frequencies are different. The main advantage of phase-shifting method is that theoretically can estimate the corresponding display pixels at subpixel accuracy. The phase-shifting method computes these correspondences by unwrapping a phase map from some images which capture displayed sinusoidal patterns. These methods provide algorithms to measure the correspondences from the camera pixels to the display pixels.

The phase-shifting method, also called fringe patterns or sinusoidal patterns, is a kind of structured light pattern used for display-camera systems. This repository provides an implementation of robust 3-step phase-shifting method combined with the graycode patterns.

Phase shift