code: def min_depth_img(self, num_img=1):
          
          depths = self._read_depth_images(num_img)
  
          return Image.min_images(depths)
docs: Collect a series of depth images and return the min of the set.
  
          Parameters
          ----------
          num_img : int
              The number of consecutive frames to process.
  
          Returns
          -------
          :obj:`DepthImage`
              The min DepthImage collected from the frames.