Non-contact Temperature Sensing for Rotating Risley Prisms
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Solution Overview
Problem
Measuring the temperatures of rotatable elements, such as those in a Risley prism assembly, in near-real time is challenging due to space constraints and the impracticality of attaching temperature sensors, which often require slip rings that increase size and introduce mechanical jitter.
Innovation Solution
A non-contact temperature measurement system using IR emissive patches and reflective surfaces to emit and reflect black body IR radiation, allowing temperature sensing without increasing the apparatus diameter, utilizing IR sensors positioned axially behind the elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors and slip rings are attached to rotatable elements, then temperature measurement capability is improved, but device size and mechanical jitter increase
Solution Approach 1:
The temperature measurement function is extracted from the rotating element and placed on the stationary housing. The IR sensor and reflective surface are fixed to the housing, while only the passive IR emissive patch rotates with the element. This separation eliminates the need for slip rings and reduces device complexity.
Solution Approach 2:
An IR reflective surface acts as an intermediary to redirect IR radiation from the rotating emissive patch to the stationary IR sensor. This mediator enables temperature measurement without direct line-of-sight alignment between the sensor and rotating element, solving the measurement capability problem while maintaining device compactness.
2Measurement precision
If temperature sensors and slip rings are attached to rotatable elements, then temperature measurement capability is improved, but mechanical jitter increases
Solution Approach 1:
The active temperature measurement components (IR sensor, reflective surface) are extracted from the rotating assembly and fixed to the stationary housing. Only the passive IR emissive patch rotates with the element, eliminating slip rings and associated mechanical jitter while preserving temperature measurement capability.
Solution Approach 2:
The mechanical contact-based temperature sensing approach is replaced with a non-contact optical measurement system using IR radiation. This substitution eliminates mechanical jitter caused by slip rings and direct sensor attachment to rotating elements.
3Ease of operation
If IR sensors are positioned to directly face rotating elements, then temperature measurement is simplified, but apparatus diameter must increase
Solution Approach 1:
The IR reflective surface is positioned at an angle (e.g., 45 degrees) to redirect IR radiation from the rotating element into the axial direction toward the sensor. This dimensional redirection allows the sensor to be positioned axially behind the element rather than radially outward, maintaining compact apparatus diameter while enabling temperature measurement.
Solution Approach 2:
The angled IR reflective surface serves as a mediator that changes the direction of IR radiation propagation. It redirects radiation from the rotating element at an angle to align with the axially positioned sensor, simplifying the measurement geometry without increasing apparatus diameter.
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
Enables near-real-time temperature monitoring of rotatable elements with minimal space impact, avoiding the need for slip rings and reducing mechanical jitter.
Implementation Method 1
a first IR emissive patch applied to a radially outward facing surface of the first rotatable element, the first IR emissive patch being configured to emit first black body IR radiation radially outward from the first rotatable element
Data Source
AI summary
An apparatus for non-contacting measurement of the temperatures of rotatable elements, such as prism elements of a Risley prism assembly, includes IR emissive patches applied to radially outward facing surfaces of the rotatable elements, reflective surfaces configured to axially reflect black body IR radiation emitted by the patches, IR sensors located behind the rotatable elements and configured to sense the reflected black body radiation, and a controller configured to receive data from the IR sensors and determine therefrom the temperatures of the rotatable elements. In embodiments, none of the IR sensors extends radially beyond a housing of the rotatable elements, and in some embodiments the IR sensors do not extend radially beyond a diameter of a largest of the rotatable elements. The apparatus can further include patches oriented axially rearward and associated IR sensors.