Conventional levels can be employed to measure just one dimensional inclinations each time, and are frequently used to measure inclination, straightness and flatness. There are two disadvantages when such levels are used to measure two dimensional inclinations (such as flatness): (1) two measurement steps are needed to measure two orthogonal directions in flatness; and (2) the two directions cannot be perfectly perpendicular to each other because of setting errors. This paper describes the development of a novel optoelectronic level which employs a simple pendulum, reflection mirror, 2D PSD and laser diode. In this system, a laser light is projected onto reflection mirror 1 which is fixed on a simple pendulum, and mirror 1 reflects the light to mirror 2 which is fixed on a fixture, and mirror 2 reflects the light to the 2D PSD. Thus, the inclination measurement result can be obtained from the output of the PSD. This paper establishes a novel system and describes the complete experiment. The A-axis rotation angle from approximately -1.3 to 1.3 degrees can be measured with an accuracy of 2 arc sec, and the B-axis rotation angle from approximately -1.7 to 1.7 degrees can be measured with an accuracy of 3 arc sec.
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