Oblon, Fisher, Spivak, McClelland & Maier
Optical axis displacement sensor
 A first convex lens, having a focal length f1 and a second convex lens, having a focal length f2, are arranged at an interval d (=f1+f2). A mirror is provided, on the optical axis, to reflect the laser beam from a laser thereby emitting parallel beams, through the first lens, onto the surface to be measured. The interval between the first lens and the surface is f1+z1. The interval between the second lens and the image point, at which the image of the surface is formed, is f2+z2. A position detector of this point, comprises a slit plate, a third convex lens, having a focal length f3, and a CCD line sensor. The interval between the slit plate and the sensor is l.sub.0. The second and third lenses are so arranged that the focal points coincide. The slit plate is provided perpendicular to the optical axis, immediately before the third lens, and a pin hole is opened at an interval d.sub.0 on either side of the optical axis. The line sensor is positioned in parallel with the slit plate. The position z2 of the image point is obtained from the interval x of the incident positions of the beams incident onto the sensor, through the two pin holes. EQU x={(f3.sup.2 +f3z2-l.sub.0 z2)d.sub.0 }/f3(f3+z2) The position z1 of the surface is obtained from the position z2 of the image point, per the formula: EQU z1=z2/(f2/f1).sup.2. 
Kohgakusha Engineering Co., Ltd. Okada Inc.
G G
G01B G01B
inventional inventional
Takashi
Miyoshi