| The trigger signal produced by the infrared laser trigger is the starting signal of the shadow photography station.The stability of the infrared laser trigger during long-term operation is very important.Once a false trigger signal occurs,the photography station will not be able to accurately capture the projectile flight image of the station,which will seriously affect the ballistic performance analysis and processing.Therefore,it is extremely important to study the instability mechanism of the infrared laser trigger and improve the long-term stability of the infrared laser trigger.Based on the analysis of the system structure and working principle of the reflective infrared laser trigger,the power stability of the infrared laser light source is the key factor for the stable operation of the reflective infrared trigger through experimental research,and the power stability of the infrared laser light source is directly determined by the output of its driving constant current source and temperature parameter.Therefore,an adaptive constant current source and temperature control system has been designed to ensure that the infrared laser works in a stable working current region 200～400m A higher than the threshold current,so that the infrared trigger can work stably and reliably.According to the temperature characteristics of the threshold current of the infrared laser,the relationship between the threshold current and the temperature of the infrared laser has been derived and calculated combined with a priori formula.According to the calculation results,an adaptive constant current source has been designed.In the temperature range of 0～30℃,the adaptive constant current source outputs three different currents at three different temperature stages,in order to make the infrared laser work in a stable area.Due to the temperature effect of the sampling resistor of the constant current source,its output current will decrease as the internal environment temperature of the Infrared trigger device rises.To solve this problem,it has proposed to use a low temperature coefficient resistor to reduce the impact of temperature changes on the output current,so that the relative change of the output current of the constant current source is less than 1%.When the ambient temperature is higher than 30℃,a higher output current of the constant current source is required to ensure the stable operation of the infrared laser,which will reduce the sensitivity of the infrared trigger,so the best operating temperature range of the infrared trigger is 0～30 ℃.In order to improve the long-term working stability of the system,it is necessary to control the temperature of the infrared trigger.This paper has designed a temperature control system with STM32 chip as the core.When the temperature is lower than 0℃,the PTC thermistor is used for heating control,and when the temperature is higher than 30℃,the temperature is cooled by the heat dissipation system in order to control the overall internal ambient temperature of the infrared trigger and increase the operating temperature range of the system.The improved reflective infrared laser trigger with a temperature control system and an adaptive constant current source was used for more than a month of power-on operation test.When the temperature is lower than 0℃,the temperature can be raised by PTC thermistor heating.When the temperature is 0～30℃,the output power of the infrared laser is adjusted by the adaptive constant current source.When the temperature is higher than 30℃,the temperature control system cooperates with the adaptive constant current source to adjust,during which the temperature of the infrared laser was kept in the range of 0～30℃,the output current of the constant current source also remained stable,the trigger did not trigger by mistake,and it worked normally.This research solves the problem of the stability of the infrared trigger,and lays a good foundation for the outdoor expansion of shadow camera stations,which has important engineering value. |
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