Chip-Scale Star Tracker Using Photonic Waveguides
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Solution Overview
Problem
Traditional star trackers are large and bulky due to the need for a substantial optical aperture, making them unsuitable for applications where size and weight minimization is desirable.
Innovation Solution
A chip-scale star tracker using a wafer-based structure with a lightguide and broadband filter-aperture to capture and analyze starlight, eliminating the need for a large telescope by coupling starlight into a planar lightguide and using interferometry for angle determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a large optical aperture is used to achieve sufficient light collection and imaging performance, then imaging performance is improved, but the size and weight of the star tracker increases
Solution Approach 1:
The patent replaces traditional mechanical optical systems (telescopes, lenses, mirrors) with a photonic integrated circuit that uses waveguides and photonic crystals to guide and filter light. This substitution of mechanical optics with photonic circuitry enables the star tracker to achieve sufficient light collection and imaging performance without the large aperture requirements of conventional systems, thereby reducing size and weight while maintaining measurement precision
Solution Approach 2:
The patent transitions from three-dimensional optical paths in traditional telescopes to two-dimensional planar waveguide structures. By confining light propagation to planar waveguides and using vertical layering of photonic crystal structures, the system achieves optical functionality in a thin, compact form factor, effectively moving the optical interaction to another dimension and eliminating the need for large physical apertures
2Use of energy by moving object
If a large optical aperture and substantial focal length are used, then light collection capability is improved, but the physical length of the telescope increases
Solution Approach 1:
The patent replaces the long mechanical telescope tube and focal length requirement with photonic waveguides that can guide light over extended effective optical paths within a compact planar structure. The waveguides enable light to traverse longer distances in a controlled manner without requiring proportional physical length, allowing sufficient light collection capability to be achieved in a short physical package
Solution Approach 2:
The patent embeds multiple optical functions (light guiding, filtering, focusing) within nested layers of the photonic integrated circuit. The photonic crystal structures are vertically stacked and integrated within the waveguide layers, creating a compact nested architecture that performs multiple optical functions simultaneously without requiring extended physical length, thereby maintaining light collection capability while minimizing the telescope's physical dimension
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a compact, wafer-thin star tracker that maintains high imaging performance while reducing the size and weight of the system, achieving accurate angle determination of stars with improved angular resolution.
Implementation Method 1
a wafer-based structures, providing a system that has a large light collection aperture on a wafer-thin substrate... the chip-scale star tracker captures plane-wave starlight propagating in free space with a wafer-thin angle-sensitive broadband filter-aperture
Implementation Method 2
directs the light into a lightguide structure for readout
Implementation Method 3
the star tracker further comprises an interferometer selectively coupled to a pair of the plurality of output optical apertures and configured to determine a phase difference between the starlight propagated via the lightguide to each of the pair of the plurality of output optical apertures
Implementation Method 4
the coupling system comprises a broadband grating coupler patterned on the surface of the lightguide... a mode of propagation of the starlight in the lightguide is at least partially determined by an angle of incidence of the starlight on the coupling system
Data Source
AI summary
A chip scale star tracker that couples starlight into a lightguide such that the angle of incidence partially determines the mode of propagation of the starlight in the lightguide. A baffle system integrated with the lightguide prevents propagation of light incident from a predetermined range of angles.