Non-prismatic optical liquid level sensing assembly

Opto-electronic means for distinguishing between the presence of liquid and the vapor above the liquid adjacent a window in a container wall, the liquid having changeable levels;

• said window having a planar outer face and a substantially parallel planar inner face in contact with the liquid or vapor,
• opto-electronic means comprising a construction having an active face adjacent the window planar outer face, a light source having a position and an axis of light emission, said axis being directed toward the active face of the opto-electronic means and through the window outer face to the window inner face, the light from the source being reflected from the window inner face in greater and lesser amounts in response to the presence of vapor or liquid adjacent the window inner face,
• said opto-electronic means further including light detector means for electrically responding to the amount of light reflected from the window inner face reaching the detector, the detector means having an axis of and a cone of light sensitivity directed toward the active face of the opto-electronic means and through the window outer face to the window inner face, and electronic means subject to the light detector means for responding to electrical changes in the light detector means resulting from changes in light reflected from the window inner face, whereby the presence of liquid or vapor on the window inner face surface is opto-electrically determined.