Patent ID: 6455838
Filing Date: 2002-09-24
Classification: B82Y,G01Q,Y10S

Abstract:
In an atomic force microscope containing an optical beam deflection sensing device, having a light source providing an incident beam, a lens for focusing the incident beam to a spot on a selected reflective object and an optical detector for receiving the beam when reflected from the reflective object, said detector generating a signal against background noise, the improvement whereby the sensitivity of the optical beam deflection sensing device is increased, comprising providing at least one of the following features:(a) a plurality of movable, removable, or interchangeable lenses in the path of the incident beam for adjusting the size of the incident beam spot, whereby to produce different size focused spots for a selected reflective object; (b) control means in the path of the incident beam for adjusting the power, size or shape of the incident beam spot including a mask inserted in the path of the incident beam having adjacent regions through which the beam is transmitted, said adjacent regions having either different optical transmission characteristics or different shapes; (c) means for viewing the spot and the reflective object, means for moving the reflective object, and spot position control means based on imaging the reflective object and the spot through the viewing means for moving the incident beam spot with movement of the reflective object whereby to maintain the position of the spot on the reflective object; and (d) control means for increasing the signal to noise ratio of the optical detector, in which the optical detector has an array of three or more segments generating signals with gains adjusted based on evaluation of one or more segment signals, and summing means for adding the signals from said three or more segments to detect a change of position or shape of the spot as the reflected beam traverses said three or more segments.