Abstract
A new type of optical range sensing method is proposed. A conical light sheet is projected onto the surface of an object to be tested through an objective lens and a bright ring pattern is produced. The position of the objective lens is controlled so that the emanating point of the conical light sheet and the bright ring pattern on the object surface are satisfied imaging condition each other against the objective lens, that is, so that the bright ring pattern becomes a fine spot. The position of the objective lens, where the best imaging condition is satisfied, is detected and distance is calculated by using the imaging formula of the objective lens. The best imaging condition is detected by observing received light power from the image of the bright ring pattern through the objective lens and a pinhole which is placed on the observation plane. Higher detection sensitivity comparing to the ordinary method is expected by theoretical consideration.
A prototype of range sensor based on the proposed method is manufactured and experimental results support the theoretical analysis. The body size of the prototype, in which 2.0mW He-Ne gas laser is adopted as a light source, is 342mm (length)×130mm (width)×174mm (height) and its weight is 5kg. The size seems bigger for robot sensor, however, it is possible to miniaturize the range sensorbased on the proposed method by adopting laser diode as a light source.
