Image Sharpness Based Range Sensing Using Pattern Projection

An image sharpness based range sensing method, purposed for measuring the thickness of relatively smooth and thin materials, is described. In this method, a camera is tilted at a nonorthogonal angle with respect to the surface measured. A change in the distance to the surface can be calculated on the basis of the change of focus location in the image formed. To homogenize image texture, a stripe pattern is projected to the surface and its effect on the measurement results is discussed. This method involves no modulation of lens parameters and the range estimation algorithm is simple. Thus fast operation, a quality needed in online measurements, could be achievable.