Abstract: A circular, transparent pipe device for optically counting and measuring objects carried with a fluid within the pipe by means of light beams exiting through the wall of the pipe. The outer radius of the pipe equals or nearly equals the product of the inner radius of the pipe (1) and the ratio of the light refraction index of the fluid within the pipe to the light refraction index of the medium surrounding the pipe. A camera or other apparatus is located at a camera point at a mean distance from the pipe between distal and proximal points of intersection of light beams hitting the internal wall of the pipe to sense the light beams.