Detecting motion for a multifunction sensor device

Tangible computer readable storage device having computer readable software embodied thereon for programming at least one processor to perform a method for detecting motion in a 3-D depth camera, the method comprising:

• obtaining time points of acceleration readings for x-, y- and z-axes from a three-axis accelerometer in the 3-D depth camera, and for each time point:
• obtaining short and long term running averages of the acceleration readings in each axis of the x-, y- and z-axes, where, and for at least one axis of the x-, y- and z-axes:
• the short term running average of the acceleration readings is taken over a number N1 of the time points as 1/N1Σt=i−N1+1t=iA(t), where A(t) represents samples of the acceleration readings along the at least one axis of the x-, y- and z-axes at the time point, t represents the time point, the long term running average of the acceleration readings is taken over a number N2 of the time points as 1/N2Σt=i−N2+1t=iA(t), and 1.3×N1<N2<1.7×N1;
• based on the short and long term running averages of the acceleration readings:
• obtaining short and long term change in pitch values of the 3-D depth camera, and short and long term change in roll values of the 3-D depth camera;
• obtaining differences between the short and long term change in pitch values;
• obtaining absolute values of the differences between the short and long term change in pitch values;
• obtaining differences between the short and long term change in roll values;
• obtaining absolute values of the differences between the short and long term change in roll values;
• determining if a threshold is exceeded by at least one of:
• (a) the absolute values of the differences between the short and long term change in pitch values and (b) the absolute values of the differences between the short and long term change in roll values;
• and
• providing an indication that movement of the 3-D depth camera is detected when the threshold is exceeded.

A motion capture system, comprising:

• a 3-D depth camera having a field of view, and comprising at least one three-axis accelerometer, the at least one three-axis accelerometer provides acceleration readings for x-, y- and z-axes at time points;
• a display;
• one or more processors associated with the 3-D depth camera, the one or more processors execute instructions to track movement of a user in the field of view and to provide a signal to the display to display images based on the tracked movement;
• and
• wherein the one or more processors:
• (a) to detect movement of the 3-D depth camera, obtain short and long term running averages from the at least one three-axis accelerometer, determine differences between the short and long term running averages, and obtain a sum based on the differences, and compare the sum to a threshold level, where the short term running averages are taken over a number N1 of the time points as 1/N1Σt=i−N1+1t=iAx(t), 1/N1Σt=i−N1+1t=iAy(t) and 1/N1Σt=i−N1+1t=iAz(t) for the x-, y- and z-axes, respectively, where Ax(t), Ay(t) and Az(t) represent samples of the acceleration readings for the x-, y- and z-axes, respectively, t represents the time points, and the long term running averages are taken over a number N2 of the time points as 1/N2Σt=i−N2+1t=iAx(t), 1/N2Σt=i−N2+1t=iAy(t) and 1/N2Σt=i−N2+1t=iAz(t), for the x-, y- and z-axes, respectively, and 1.3×N1<N2<1.7×N1, and (b) temporarily suspend the tracking of the movement of the user in response to an indication that the movement of the 3-D depth camera is detected.