| In recent years,with the emergence of unmanned combat platforms,unmanned aerial vehicles and portable equipment for individual soldiers,the miniaturized,handheld long-range laser rangefinders have highlighted broad application prospects.At present,the mainstream route of long-range laser rangefinders is to use pulsed laser ranging methods.On the one hand,due to the long detection distance,long-range laser rangefinders require high-power lasers as the light source,which raises high reqirements of the sensitivity and dynamic range of the detection system,it is difficult to miniaturize the system.On the other hand,when the total energy of pulsed laser ranging is low,although the pulse can be compressed to increase the peak power of the laser and increase the ranging range of the system,the ranging precision of this ranging method is generally not well.Due to these two contradictions,the general pulsed laser ranging system is difficult to miniaturize in order to improve the ranging precision of the system,so there are few handheld pulsed laser ranging systems.In the context of the application of handheld or wearable devices,the volume and weight of laser rangefinders are restricted.The size of the optical and mechanical structure,including system parameters such as aperture and field of view,are basically within a certain range,and cannot be improved by increasing the aperture of the telescope.For the detection capability of the system,only high-power lasers can be used as the light source to increase the peak power of the transmitted pulse.With the development of laser technology,all-solid-state lasers with small size,light weight,high beam quality and eye-safe wavelength bands are used as the emission source of handheld remote laser rangefinders.Consumption of embedded systems has become the technical key to the development of handheld high-precision remote laser rangefinders.This article mainly focuses on the technical requirements of a handheld,high-precision remote laser rangefinder,and proposes a hardware and software system design scheme for a handheld remote laser rangefinder.First of all,the hardware system includes a laser transmitter module,a laser receiver module,and a main controller module.The solid-state laser drive circuit for power boost and constant current source output is designed and implemented on a small-sized PCB board,and the drive current is controlled at 8-10A,the time is maintained at 1.8ms-2.3ms,which realizes the stable driving of the solid-state laser;designed by the APD bias voltage control circuit,transimpedance amplifier,high-pass filter,differential amplifier,current feedback amplifier and differential output comparison The hardware circuit of the laser receiving module composed of a low-cost,small-size and narrow-bandwidth circuit realizes the automatic gain adjustment and small-signal amplification of the laser echo,and achieves high-precision under the condition of a certain expansion of the echo pulse.Time identification:The low-cost STM32 single-chip microcomputer with ARM architecture is used as the main controller module to realize the control of the whole system.Combined with the TDC time digital conversion chip,a high-precision time measurement module is designed,and the timing precision reaches 45ps.Second,the embedded software system is based on Real-time Operating System(RTOS)design and adopts a multi-tasking method to make the system have the characteristics of fast response,zero interruption delay and low power consumption.Finally,the algorithm of walking error compensation is researched.The study found that in a larger range,even if the detection circuit saturates the short-distance echo,the walking error still corresponds to the pulse width of the laser echo.The echo pulse width and the walking error can be simulated and combined curve compensates for the error.Based on this model,an effective method of compensating walking error is proposed.Realizing the precise timing of flight(TOF)and effectively improving the system’s ranging precision.In this paper,the software and hardware system of the handheld laser rangefinder has been developed and a lot of tests have been carried out.The test results show that the range of the handheld rangefinder can reach 2km,the range precision is±20cm,the hardware quality of the system is 106g,and the size is 10×7×3.5cm~3,which can be applied to miniaturized platforms and wearable devices to achieve long-distance and high-precision ranging capabilities. |
