Laser receiving circuit for phase-based laser rangefinders

Abstract

The invention provides a laser receiving circuit for phase-based laser rangefinders, comprising a trans-impedance amplifier and high-frequency amplifier module, a mixer and intermediate-frequency amplifier module and a band-pass filter module, which are connected in sequence. The trans-impedance amplifier and high-frequency amplifier module comprises an APD (Avalanche Photo Diode) used especially as a photoelectric sensor, and a trans-impedance amplifier and a high-frequency amplifier used for amplifying an electrical signal converted from an optical signal received by the APD. The mixer and intermediate-frequency amplifier module comprises a double-balanced mixer used for mixing a measurement signal and a local oscillation signal, and an intermediate-frequency amplifier circuit. The band-pass filter module finally outputs a range-finding signal in the form of sine wave voltage of which the center frequency is 14.0625 KHz. The laser receiving circuit can effectively overcome the disadvantages brought about by the fact that an APD is used both as a sensor and as a mixer in the prior art, and the overall noise is greatly reduced compared with the prior art. The circuit performance is more stable, the measurement accuracy is higher, and the ranging distance of phase-based laser rangefinders is increased effectively.

Description

technical field [0001] The invention relates to a phase type laser range finder, in particular to a laser receiving circuit for the phase type laser range finder. Background technique [0002] The working principle of the phase laser rangefinder is to use the frequency of the radio band to modulate the amplitude of the laser beam and measure the phase delay caused by the modulated light going back and forth to the survey line once, and then convert the phase delay represented by the modulated light according to the wavelength of the modulated light. distance. The laser emitting drive circuit and the laser receiving circuit are important components of the laser range finder, and their performance directly affects the performance indicators of the laser range finder such as the measuring distance, ranging accuracy, working sensitivity, and working stability. [0003] At present, the laser receiving circuit used in the common phase laser range finder usually uses APD tube (ava...

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Problems solved by technology

[0003] At present, the laser receiving circuit used in the common phase laser range finder usually uses APD tube (avalanche diode) as the sensor for receiving the laser signal and the mixer for receiving the signal. Its advantage is that the structure of the entire laser receiving circuit is relatively Simple, but its existing problems are: because the APD tube is usually used as a device specially used for photoelectric sensors, it is not suitable for use as a mixer; the laser receiving circuit used in the existing phase laser range finder uses the APD The tube is used both as an optical signal sensor and as a mixer. For phase laser rangefinders with different measuring frequency frequencies, the difference in mixing gain is obvious; For the laser rangefinder, the mixing voltage is only about 3V; for the low-frequency phase laser rangefinder with a frequency of 450KHz, the mixing voltage needs to be 30V. When the mixing voltage is relatively high, the interference to the circuit is relatively large. , which improves the overall noise level of the system and reduces the working stability of the circuit; especially for the measurement range of more than 200 meters, it affects the measurement accuracy

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