| 摘要 |
A tacheometer utilizes a gallium arsenide laser diode in a phase shifting distance encoder, a sinusoidal interpolator in a phase shifting shaft angle encoder, a mercury pool in a phase shifting two axis off-level encoder, a shared phase to digital decoder and a digital processor, to measure angles and distances corrected for off-level, speed of light variations, refraction and the earth's curvature. A reflecting telescope is coupled to the shaft angle encoder and is incorporated in both the phase shifting distance encoder and the alignment system. The reflecting telescope has a doublet objective lens with an embedded secondary reflective surface facing a primary mangin mirror. A biconcave element of the doublet objective lens also functions as a corrector for the secondary reflective surface. A compact objective lens system is thus realized, having minimal interference between the corrector for the secondary reflective surface and the optical path through the doublet objective lens. |
