An active distance measuring apparatus comprises a projector for projecting modulated light to an object, a photo-sensor for sensing the modulated light reflected by the object to produce a pair of alternating current signals in accordance with a distance to the object, and a signal processor for producing a distance signal in accordance with the pair of alternating current signals. The signal processor includes a detector means for detecting a voltage corresponding to each of the pair of alternating current signals a plurality of times and adding the results of such detection and repeating such detection and addition a plurality of times and a calculation for calculating the distance signal based on the output of the detector.
This disclosure is directed to apparatus for measuring height of a surface of liquid in a container utilizing a light source and camera pair disposed above the liquid surface in a predetermined spatial relationship to each other and the container. The light source illuminates the liquid surface with a light pattern and the camera captures the area image of the light pattern in a form of discrete picture elements (pixels) that are processed in an image processor to determine the height of liquid in the container. In another embodiment, the pixels of the area image are further processed to determine attitude of the liquid surface so that the processor may determine the quantity of liquid in the container based on the determined height and attitude of the liquid surface and container geometry data stored in a memory thereof. In yet another embodiment, a plurality of light source/camera pairs are disposed above the liquid surface, each pair operates by capturing an area image of the light pattern on a portion of the liquid surface illuminated by its light source. The pixels of the area image of each pair are processed in the image processor to determine the heights of the corresponding liquid surface portions. In still another embodiment, a plurality of cameras are disposed above the liquid surface to observe at least one light pattern at different viewing angles. Each camera captures an area image of the at least one light pattern and the pixels of such area images are processed in the image processor to determine at least one height for the liquid surface in the container. In this embodiment, the image processor may include an algorithm for combining together the pixels of the various area images of the plurality of cameras to determine the at least one liquid surface height.
