The infrared rangefinder's design
The infrared rangefinder is mainly composed of a modulated light emitting unit, a receiving unit, a phase measuring unit, a counting and displaying unit, a logic control unit and a power converter. The light source is usually gallium arsenide (GaAs) semiconductor light emitting diode. When a considerable current passes through the P-N junction of the GaAs diode, the P-N junction will emit near-infrared light with a wavelength of 0.72 μm and 0.94 μm, which is due to the electron-hole recombination in the doped GaAs semiconductor. , the excess energy is released in the form of photons. Moreover, the emitted light intensity will vary with the injection current. Therefore, if it is used as the light source of the rangefinder, the amplitude modulation of the emitted light intensity can be directly performed by changing the magnitude of the feed current, that is, this semiconductor light-emitting device has the dual functions of "radiation" and "modulation".
The infrared photodetection conversion device used to receive modulated light is usually a silicon photodiode or an avalanche photodiode, and these devices have a "photovoltage effect". When extraneous light shines on its P-N junction, because the effect of photoelectric energy conversion can produce a potential difference at P-N two poles, its magnitude will follow.
Technical indicators and functions of photoelectric range finder
The maximum range of the short-range infrared photoelectric range finder is 2 500m, and the distance measurement accuracy can reach ± (3mm+2×10-6×D) (where D is the measured distance); the minimum reading is 1 mm; the instrument is equipped with automatic The light intensity adjustment device can also manually adjust the light intensity when measuring in complex environments; the temperature, air pressure and prism constant can be input to automatically correct the result; the vertical angle can be input to automatically calculate the horizontal distance and height difference; the distance can be preset Carry out alignment stakeout; if you input the station coordinates and elevation, it can automatically calculate the coordinates and elevation of the observation point. The distance measurement method includes normal measurement and tracking measurement. The normal measurement takes 3s, and the average value of several measurements can be displayed; the tracking measurement takes 0.8s, and the distance measurement is automatically repeated at regular intervals.
