Abstract: A method of monitoring particle beam current in an ion implanter in which the ion beam is analyzed to separate it into a separate sub-beam for each ion charge state. At least one sub-beam, having a charge state different from the desired charge state, is intercepted, and the current of the intercepted sub-beam is measured. This current is useful as an estimate of the current of the desired sub-beam which is used for the implantation.

Abstract: This invention is directed to an electro-optical apparatus for determining the position of an opaque surface without contact with the surface. It includes a light beam system which projects a well defined beam having a rectangular cross-section, obliquely onto the surface such that any movement of the surface in the perpendicular direction will result in a displacement of the illuminated area on the surface, and a detector which converts this displacement into a proportional light intensity. The detector has a field stop with an aperture of specific shape onto which the illuminated area is imaged such that only a portion of the image will pass through the aperture depending on the displacement of the illuminated area. A photosensitive device is used to measure the light intensity passing through the aperture.