Optically stimulated electron emission apparatus
Inventors
Assignees
National Aeronautics and Space Administration NASA • Analytical Mechanics Associates Inc
Publication Number
US-11218111-B2
Publication Date
2022-01-04
Expiration Date
2038-04-25
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Abstract
An apparatus for inspecting a surface includes a housing and a probe. The housing includes a light source to direct light along a longitudinal axis and a shutter to selectively allow light to pass through to the probe. The probe includes a body portion and a head portion. The head portion of the probe includes a collector to detect photoelectrons emitted from the surface in response to light from the light source impinging on the surface. A proximal portion of the head portion moves relative to a distal portion of the head portion to allow for variations in angle relative to the surface.
Core Innovation
The invention describes an optically stimulated electron emission (OSEE) apparatus and methods for inspecting surfaces by directing ultraviolet light from a light source onto a test surface and detecting a current of photoelectrons generated by the light. The apparatus includes a housing containing the light source and a shutter to control light passage, and a probe with a body portion and a head portion. The probe's body defines a passageway for light from the source to travel through. The head portion includes a collector configured to detect photoelectrons emitted from the surface in response to the light impinging on it.
The probe's head portion is uniquely designed with a proximal portion and a distal portion, wherein the distal head portion, which includes the photoelectron collector, can move relative to the proximal portion to accommodate variations in angle and position with respect to the surface. This movement can involve axial displacement or angular adjustment facilitated by a gimbal apparatus, gimbal fasteners, and resilient members, allowing the collector to stay parallel to the surface for repeatable and accurate measurements. The apparatus also includes mechanisms such as a shutter that opens only when the probe head is engaged with the surface, enhancing measurement reliability.
The invention addresses the problem of conventional OSEE sensors having relatively large probe tip sizes (e.g., about 2×2.5 inches) that limit usage in confined or restrictive environments. Smaller probe tips under 1 inch in diameter and interchangeable probe designs with customized form factors improve access to tight spaces and allow for better handling. Furthermore, fixed probe tips in conventional apparatus do not accommodate minor hand movements or misalignments, which can cause inconsistent readings. The movable head portion in this invention allows for self-righting and precise alignment, mitigating shaking or misalignment for more reliable surface contamination assessments.
Claims Coverage
The patent includes multiple independent claims covering a probe for collecting optically stimulated electron emissions and apparatuses incorporating such probes with various inventive features.
Probe with a movable distal head portion
The probe comprises a body portion defining a passageway for light and a head portion including a proximal head portion coupled to the body and a distal head portion movably coupled to the proximal head portion. The distal head portion is configured to move relative to the proximal head portion and includes a collector configured to detect photoelectrons emitted from the surface in response to light impinging on it.
Apparatus housing with light source and shutter controlling light passage
An apparatus for inspecting surfaces includes a housing defining an interior cavity extending along a longitudinal axis, with a light source directing light along the axis and a shutter positioned away from the light source to selectively allow light passage. The light passes along the probe's body passageway when the shutter is open.
Engageable head portion with shutter control linked to engagement state
The probe's head portion is configurable between an engaged position in contact with the surface and a disengaged position away from the surface. The shutter is configured to open only when the head portion is engaged and is restricted from opening when disengaged, ensuring light transmission and measurement occur only during proper alignment.
Gimbal apparatus for relative movement between head portions
The head portion includes a gimbal apparatus extending between the proximal and distal head portions, comprising gimbal fasteners and resilient members that allow the distal head portion to move relative to the proximal head portion. The gimbal apparatus can maintain the collector parallel to the surface and provide biasing for proper alignment.
Grid and ground circuit boards adjacent collector surfaces for signal transmission
The collector defines a first surface facing the surface and a second surface facing the light source. Adjacent to these surfaces are a grid circuit board electrically coupled to the collector and a ground circuit board, enabling transmission of sensed signals generated by photoelectrons to housing electronics.
Small diameter probe passageway for light travel
The inner diameter of the body portion's passageway is less than 1 inch, enabling smaller cross-sectional profile probes suitable for tight or restricted environments.
The claims collectively cover a probe featuring a movable distal head portion with a photoelectron collector, integrated into an apparatus with a housing containing a light source and shutter, wherein the shutter operation depends on probe engagement with the surface. The incorporation of a gimbal apparatus for alignment, the electrical configuration for signal transmission, and the small diameter probe passageway are key inventive features enabling accurate, reliable, and versatile surface contamination inspection.
Stated Advantages
The smaller probe tip allows inspection in tight or restrictive environments where larger probe tips cannot fit.
The movable head portion provides self-righting and alignment with the test surface, resulting in accurate and consistent readings.
Interchangeable probes with different form factors enhance customization for various sensing applications and facilitate servicing or cleaning.
The gimbal apparatus dampens operator-induced movement during manual operation, improving measurement reliability.
The shutter control linked to probe engagement prevents measurement errors by only allowing light passage when the probe is properly positioned.
The apparatus reduces overall size and increases maneuverability by placing electronics and purge gas supply outside of the handheld sensor unit.
Documented Applications
Inspecting surfaces such as carbon fiber surfaces sealed to prevent fiber protrusions, detecting contaminants like extraneous seal material or silicone.
Quality inspection of surfaces by detecting surface contamination based on the number of photoelectrons emitted in response to ultraviolet light exposure.
Use in environments requiring small probe sizes and precise sensor tip positioning, including manual operation or robotic integration for automated surface inspection.
Replacement or interchange of probe tips with varying shapes and sizes to adapt the apparatus for different geometries and application constraints.
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