在基本的开普勒望远系统光路中, 放置了两块与光轴成45°角的镀膜平板玻璃, 一块能反射中心波长1550nm的红外光, 同时透射可见区和中心波长1310nm的近红外区;另一块能反射中心波长1310nm的红外光, 透射可见区。增加了控制光光路和信号光光路, 节省了光路元件。分析了平板玻璃对可见光路的影响, 通过改变平板玻璃的厚度, 使得轴上偏差在允许的范围内。测定了信号光通过望远镜筒和镀膜反射镜片的功率损耗, 分别得到了1.31%和2.90%的损耗比。测量了信号光的透射率随角度的变化关系。经过多次试验, 三光路共轴望远系统已成功用于远距离红外光控音频监测。

In the basic Kepler telescope system, two pieces of coated glass are placed into the optical path at a 45°angle with optical axis. One can reflect infrared light at the wavelength of 1550nm, while it transmits the visible and controlling infrared light with central wavelength at 1310nm; the other can reflect the controlling infrared light with central wavelength at 1310nm, while it transmits the visible light. By incorporating the controlling light and signal light paths, the system becomes simple and practical. Cost is reduced. The impact of the plate glass for visible light path is analyzed, and the path deviation falls within allowed error range by changing the thickness of the plate glass. Power loss of the signal light passing through some optical components is measured, the loss ratios for the telescope tube and plate glass measured at laboratory are 1.31% and 2.90% respectively. Transmission coefficient of signal light is deter-mined. Three optical path coaxial telescope system is successfully used in long-distance infrared control audio frequency monitor after many tests.