Sources of Error in the Ranging of Photoelectric Range Finders
The ranging error of the photoelectric rangefinder is divided into two parts:
(1) Proportional error: The error is proportional to the length of the measured distance. It is mainly caused by frequency error, atmospheric refractive index error and vacuum light speed measurement error that bring errors to the distance measurement results. The impact of the light speed measurement error on the distance measurement value is negligible.
(2) Fixed error: The inherent error of the instrument, which has nothing to do with the length of the measured distance, including the calibration error of the zero point error, the alignment error between the instrument and the reflector, the phase measurement error, the amplitude and phase error, the phase non-uniformity error of the light emitting tube and period error. The periodic error mainly comes from the co-frequency interference of the photoelectric signal inside the instrument, and the size of the error occurs repeatedly based on the length of the precision ruler.
Among them, the proportion error, period error and zero point error are the main system errors of the photoelectric range finder.
According to a large amount of measured data, it is shown that due to factors such as phase non-uniformity of the instrument's light-emitting tube and receiving tube, as well as amplitude and phase errors, the instrument also has correction terms related to the distance in addition to frequency error and atmospheric refractive index error. It is customary to refer to the distance as the correction term. Correcting numbers related to length are collectively called multiplicative constants!. The correction number for the zero point error is called the additive constant. Systematic errors can be eliminated by applying corrections to the system error values obtained during calibration. Therefore, the verification of the system error of the photoelectric rangefinder mainly includes the following three items:
(1) Calibration of period error;
(2) Verification of addition constant;
(3) Test of multiplication constant.
