空间液晶双折射滤光器精密温度控制技术研究

Research on Precision Temperature Control Technology for Deep-space Liquid Crystal Birefringent Filter

液晶型双折射滤光器采用低压驱动器件、移除旋转电机等技术使滤光器的光、机、电结构大大简化,成为深空太阳磁场观测任务中的首选技术方案.滤光器中光学元件的折射率对温度变化非常敏感,为了确保滤光器的透过带在0.1Å范围内稳定,满足太阳磁场、速度场测量的高灵敏度要求,需要保证滤光器光学腔体内的温度稳定在±0.005℃以内.由于可供选择的宇航级模数转换器(Analog-to-Digital Converter,ADC)分辨率较低,直接使用无法满足高精度测量的要求,将测温区间分段并设计使用多级放大、低通滤波电路和宇航级ADC的方案,实现了-20-100℃的大范围温度信号采集和38-46℃目标温度段内0.0002℃的高分辨率温度采集;再以热电制冷器(ThermoElectric Cooler,TEC)作为热控元件,使用增量式PI(Proportional Integral)控制算法,实现了精密温度控制,在真空试验中,系统温控精度优于±0.005℃.上述研究工作不但能够为地面液晶双折射滤光器提供精密温度控制系统,而且也为深空太阳磁场、速度场测量提供了一种可行的技术方案.

The liquid crystal birefringent filter has become the preferred technology option for deep space magnetic field exploration missions due to the use of low-voltage actuators,removal of rotary motors,and other technical features,which greatly simplify the filter’s opto-mechanical structure.The refractive index of optical elements in filters is very sensitive to temperature changes.In order to ensure that the passband of the filter remains stable within a range of 0.1Å,and meet the high sensitivity requirements for space magnetic field observation,it is necessary to achieve a temperature stability accuracy of±0.005℃ within the optical cavity of the filter.Due to the low resolution of the available astronaut-grade Analog-toDigital Converter(ADC),which are unable to meet the requirements for high-precision measurements if used directly,in this paper,we segmented the temperature range and designed the scheme of multi-stage amplification,low-pass filter circuit and space grade ADC to realize a wide range of temperature signal acquisition from−20℃ to 100℃ and a high resolution temperature acquisition of 0.0002℃ within the target temperature range of 38℃ to 46℃.Then,the thermoelectric cooler(TEC)was used as the thermal control element with incremental PI(Proportional Integral)control algorithm,which realizes the precision temperature control,and the system temperature control accuracy was better than±0.005℃ in the vacuum test.The above work can not only provide a precise temperature control system for groundbased liquid crystal birefringence filters,but also provide a feasible technical solution for deep space solar magnetic field and velocity field measurements.