Patent ID: 7106421

Claim:
In a monitoring apparatus having a detection area for use in a measurement operation, said monitoring apparatus being adapted to receive waves from said detection area and to output data for specifying at least a position of a target object in said detection area at least from the quantity of the received waves, a method of adjusting axial displacement of said detection area in a rolling direction, said method comprising the steps of: preparing a target, said target having a detection surface with a specified outer shape, a bright part with a higher reflectivity for waves and a dark part with a lower reflectivity than said higher reflectivity for waves being arranged over said detection surface in a specified pattern, wherein a waveform of wave quantity having a double-peaked shape corresponding to at least one selected from the group consisting of said pattern and said outer shape of said detection surface is obtained with respect to a standard position in a standard direction if said measurement operation is carried out in said standard direction by directing said detection area of said monitoring apparatus towards said detection surface; setting said target in front of said monitoring apparatus by matching a standard direction of said detection surface with an expected standard direction of said detection area; obtaining axial displacement of said detection area in said rolling direction by repeating said measurement operation at least twice by changing measurement position in a perpendicular direction which is perpendicular to said standard direction and by calculating each time a standard position of said detection surface in said standard direction from the waveform, and correcting said axial displacement by a correction step selected from the group consisting of adjusting an attachment angle of said monitoring apparatus and changing a parameter for setting said detection area.