1. Types of rangefinder errors
The infrared rangefinder has the advantages of high degree of automation, fast ranging speed and high precision. However, if the instrument is used improperly or poorly maintained, instrument performance may change prematurely, resulting in a loss of accuracy. The aging of electronic components is also an important reason for the decline of instrument accuracy and the change of instrument additive constants. In order to grasp the performance indicators of each instrument, use the instrument reasonably, and measure high-quality data, it is necessary to conduct comprehensive tests on the instrument regularly.
There are many types of ranging errors, including aiming errors, amplitude and phase errors, misalignment errors, period errors, errors due to signal-to-noise ratio, etc. There are occasional errors and system errors. Although the aiming error is accidental, there is also a certain regularity. A good surveyor should master the performance of the instrument he owns so that he can use the instrument to observe within the smallest error range of the instrument.
2. Rangefinder aiming error
The aiming error refers to the inconsistency of the distance measurement results when the rangefinder emits the beam at different positions, that is, the error of the uneven spatial phase of the light-emitting tube or the modulator, mainly caused by gallium arsenide (GaAs), which is the phase difference of the beam emitted by the LED. caused evenly. The beam emitted by gallium arsenide, ideally, has the same phase on a curved surface equidistant from the light-emitting tube within the beam range. Again, the distance measured anywhere on the beam is the same, but it's not. The phase of each point on the curved surface at the same distance from the light-emitting tube is different, and the phase with the same phase is an irregular curved surface, resulting in different results when using beams at different positions to measure the distance. The difference between the two lies in the uneven phase caused by aiming error.
3. Rangefinder calibration
It can be seen from the iso-phase curve and iso-intensity curve that the aiming error distribution is more uniform, but in order to better improve the observation accuracy, when aiming at the prism, aim at the part with the smallest error - the optimal area. In order to reduce the aiming error, on the one hand, it is necessary to improve the manufacturing process of the modulator or the light-emitting tube to improve the uniformity of its spatial phase. However, this method has a great influence on the measurement of the instrument, and cannot eliminate the influence of phase unevenness. Considering that the deflection of the aiming relief is caused by the aiming error of the telescope and the non-parallel between the transmitting and receiving optical axes and the collimation axis of the telescope, the former is accidental and the latter is systematic. Therefore, when using the instrument, the three-axis parallelism should be checked and corrected frequently to find the best observation area to improve the observation accuracy.
