Invention:
Existing corner cube reflectors introduce unwanted polarization change to incident light. This invention provides a solution to remove this polarization change and thereby reduces polarization dependent loss and improves the performance of the reflector. This solution can be applied to both mirror-based and prism-based corner cube reflectors. This invention also includes a method to design and manufacture a corner cube reflector to precisely control the change of polarization using a compensation filter and/or coating. The polarization compensation filter is made of at least one layer of patterned birefringent material. In some embodiment, the filter is used to preserve the polarization of the incoming light, such that the polarization of the reflected light is the same as the incoming light for a range of angle of entry. In other embodiments, the filter is used to change the polarization of the incoming light to a predefined polarization, such that the polarization of the reflected light is equal to the predefined polarization for a range of angle of entry.
Background:
Corner cube reflector is used extensively in many optical systems to redirect an incoming beam of light back toward its incoming direction. One advantage of the corner cube reflector is that it can reflect light at a range of angle of entry, making it an indispensable optical component for alignment. Another advantage is its small compact size, which can be tiled in an array to cover large areas. Applications of corner cube reflector include spectroscopy, road sign, free space optical communication, positioning, land survey, laser cavity, distance or time-of-flight measurement, interferometry, navigation, and precision alignment. A corner cube reflector is made of three intersecting and perpendicular flat reflectors. There are generally two types: one made of three flat mirrors, and one made of three-sided glass prism. In both types, light is reflected by each surface three times, either by the mirrors or by total internal reflection (TIR) at the glass-air interfaces. One disadvantage of the corner cube reflector is the change of polarization state after the reflections which is caused by the reflections of light and by the change of its direction of propagation. The latter change component is geometric in nature. Both change components depend on the location and angle of entry. Generally, reflector made of metal-coated mirror has smaller polarization change than reflector made of glass prism. For applications where the preservation of the polarization state is critical, a corner cube reflector that does not change the polarization state of the incoming light is needed.
Applications:
- Spectroscopy
- Sensors
- Any applications that use reflected light
Advantages:
- More accurate
- Higher performance
- No polarization loss
