Two-dimensional positioning apparatus and method for measuring laser light from the apparatus

A two-dimensional positioning apparatus for positioning an object in a two dimensional direction, said apparatus comprising:

• a platen comprising teeth formed at fixed spacings along X and Y axes;
• a slider comprising two X-axis motors, two X-axis positioning sensors, a Y-axis motor, and a Y-axis position sensor, said slider being loaded with said object and disposed above said platen;
• a converter for producing signals for detecting X-axis position of a center point of said slider and a yaw angle θ of said slider according to position detector signals from said two X-axis position sensors;
• an Xθ controller for feedback controlling movement of said slider in X-axis and θ-axis directions separately according to signals converted by said converter;
• a command converting circuit for converting control output of said controller to propulsion commands to be supplied to said two X-axis motors;
• a Y-axis controller for receiving a position detection signal from said Y-axis position sensor, and for feedback controlling Y-axis direction according to said position detection signal;
• levitating means for levitating said slider so that said slider is disposed above said platen;
• wherein
• said Y-axis motor is mounted on said slider to move said slider in a Y-axis direction;
• wherein
• said two X-axis motors are mounted symmetrically around said center point of said slider to move said slider in an X-axis direction;
• wherein
• said Y-axis position sensor detects a Y-axis position of said slider;
• wherein
• said two X-axis position sensors are mounted on said two X-axis motors, respectively, to detect respective X-axis positions of said slider;
• wherein
• said command converting circuit receives position detection signals from said two X-axis position sensors and produces a signal for detecting an X-axis position of said center point of said slider according to a sum of said position detection signals, and produces a signal for detecting yaw angle θ of said slider according to a difference between said position detection signals;
• and wherein
• said control outputs converted by said command converting circuit are x-axis and θ-axis propulsion commands;
• and further comprising:
• a limiter for restricting X-axis limits of a propulsion command Ir0 to Imax−|Irθ|, wherein Imax is the maximum value of the propulsion command and Irθ is θ-axis propulsion command, and thereby restricting limits of propulsion command Ir0 according to magnitude of θ-axis propulsion command Irθ.