Telescope
Inventors
Assignees
NASA Langley Research Center • Montana State University Bozeman • University Corp for Atmospheric Research UCAR
Publication Number
US-11143748-B2
Publication Date
2021-10-12
Expiration Date
2036-04-27
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Abstract
A shared optics and telescope for transmitting a transmission beam and receiving a return signal is provided. The shared optics and telescope includes a pair of axicon lenses operable to shape the transmission beam into an annular beam having an outer diameter and an inner diameter, a secondary mirror operable to deflect the annular beam into a deflected annular transmission beam, and a primary mirror that includes an inner mirror portion and an outer mirror portion, the inner mirror portion operable to expand the deflected annular transmission beam, and the outer mirror portion operable to collect the return signal.
Core Innovation
The invention provides a shared optics and telescope system that utilizes a pair of axicon lenses to shape a transmission beam into an annular pattern with defined inner and outer diameters. This shaped annular beam is deflected by a secondary mirror to produce a deflected annular transmission beam. The primary mirror of the telescope features an inner mirror portion, which expands the deflected annular transmission beam, and an outer mirror portion, which is responsible for collecting the return signal.
This shared telescope system is designed for transmitting a transmission beam and receiving a return signal using the same optical structure. The approach addresses issues seen in previous LIDAR systems, such as poor efficiency due to light lost when the full primary mirror is illuminated and isolation problems between transmit and receive paths in systems using polarization switches. By efficiently shaping and expanding the transmitted beam and collecting the return signal separately, the system enhances performance by improving optical stability, providing better signal isolation, and allowing for eye-safe transmission.
The problem being solved by this invention is the need for a micropulse differential absorption LIDAR instrument capable of autonomous, long-term operation under varied atmospheric conditions like daytime, cloud cover, and rapidly changing environments. Existing technologies face challenges such as limited spatial and temporal resolution, inefficient beam expansion, inadequate signal isolation, and compliance with eye safety standards. The new shared optics and telescope design aims to overcome these limits, delivering improved duty cycle, mechanical and thermal stability, and enhanced measurement capability required for accurate weather forecasting and high-resolution water vapor profiling.
Claims Coverage
The patent contains two independent claims, each defining a key inventive feature related to the shared optics and telescope for transmitting and receiving optical signals in LIDAR systems.
Shared optics and telescope using paired axicon lenses and segmented primary mirror
A shared optics and telescope system comprises: - A pair of axicon lenses operable to shape a transmission beam into an annular beam with both an outer diameter and an inner diameter. - A secondary mirror designed to deflect this annular transmission beam into a deflected annular pattern. - A primary mirror with a single focal length, having an inner mirror portion configured to expand the deflected annular transmission beam and an outer mirror portion designed to collect the return signal from the target or medium. This configuration enables both transmit and receive functions in a single telescope assembly, with distinct optical paths managed by spatial separation on the primary mirror.
Method of transmitting and receiving using shared telescope with annular beam shaping
A method that includes the steps of: 1. Shaping a transmission beam into an annular pattern using a pair of axicon lenses. 2. Deflecting the annular transmission beam towards a primary mirror (with a single focal length) via a secondary mirror, creating a deflected annular transmission beam. 3. Expanding the deflected annular transmission beam with an inner mirror portion (and a telescope lens) of the primary mirror. 4. Collecting a return signal using an outer mirror portion of the primary mirror. This procedure enables efficient and isolated handling of transmit and receive optical signals through a single telescope apparatus.
In summary, the inventive features cover a shared telescope system utilizing axicon-based annular beam shaping and segmented mirror functions to efficiently transmit and receive optical signals for LIDAR applications, as well as the corresponding method implementing this optical path management.
Stated Advantages
The system provides substantially improved optical and mechanical stability, being a factor of 20 times more stable than prior coaxial telescope designs.
Efficient shaping and expansion of the transmission beam allows eye-safe operation while maximizing transmitted energy and conforming to applicable safety standards.
The design offers excellent isolation between transmitted and received signals by spatially separating transmit and receive optical paths on the primary mirror.
It eliminates the need for polarization transmit/receive switches, thereby reducing crosstalk and improving signal purity.
The architecture supports improved system duty cycle and robust operation over a greater range of atmospheric and lighting conditions, including daytime and cloudy weather.
Documented Applications
Used in micropulse differential absorption LIDAR (DIAL) instruments for measuring atmospheric water vapor and other molecular species.
Applicable in autonomous, long-term field operation of LIDAR systems for weather forecasting, climate studies, and mesoscale meteorological observations, including during daytime and under cloud cover.
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