Laser Gyrometer Mirror Positioning via Temperature Lookup
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Solution Overview
Problem
Current laser gyrometers face long convergence times and hysteresis issues during startup due to thermal expansion and contraction, leading to suboptimal gain utilization and mode jumping, especially in three-axis systems where mirror positioning is complex and non-reproducible.
Innovation Solution
A method for initializing the positioning of movable mirrors in a three-axis laser gyrometer involves scanning without intensity measurement to reduce hysteresis, using a table of optimal mirror positions based on temperature values, and adjusting mirror positions to maintain maximum intensity through a servo control mechanism, allowing continuous tracking of thermal changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If successive offsets are applied to the mobile mirror to converge towards maximum intensity, then the gain utilization is improved, but the convergence time becomes excessively long
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the optimal mirror position for each temperature value in a lookup table before operation. During startup, the system simply retrieves the pre-determined optimal position based on the current temperature, eliminating the need for time-consuming successive offsets and intensity measurements during actual operation.
Solution Approach 2:
The patent replaces the mechanical iterative adjustment process (successive offsets with intensity measurements) with a computational approach using a lookup table. The system substitutes physical trial-and-error adjustment with direct retrieval of pre-computed optimal positions based on temperature.
2Measurement precision
If the mirror is returned to a previous offset value after scanning, then hysteresis effects cause the maximum to shift, but repeating the convergence process increases time loss
Solution Approach 1:
The patent performs the convergence process in advance during system calibration, storing the results in a lookup table. This preliminary action captures the optimal positions accounting for all hysteresis effects, so no additional convergence time is needed during actual operation - the system directly retrieves the pre-determined optimal position.
Solution Approach 2:
The patent creates a copy of the optimal mirror positions for different temperature conditions in the form of a lookup table. This copy allows the system to quickly retrieve pre-determined optimal positions without repeating the time-consuming convergence process, while still accounting for hysteresis effects that were captured during table generation.
3Loss of time
If temperature compensation is implemented using a lookup table, then startup time is reduced, but the system complexity increases due to additional control mechanisms
Solution Approach 1:
The patent replaces complex real-time iterative control mechanisms with a simple lookup table approach. The system substitutes mechanical trial-and-error adjustment with direct table lookup based on temperature sensing, significantly reducing startup time while keeping the control mechanism relatively simple.
Solution Approach 2:
The patent introduces a lookup table as an intermediary between temperature sensing and mirror positioning. This intermediary pre-computes the optimal positions, allowing the system to quickly translate temperature readings into appropriate mirror positions without complex real-time calculations or iterative adjustments.
4Reliability
If the cavity length is not adapted at startup, then the laser gain is not fully utilized, but thermal expansion and contraction cause continuous length variations
Solution Approach 1:
The patent implements feedback by continuously monitoring the temperature and using this information to retrieve the appropriate optimal mirror position from the lookup table. This closed-loop approach ensures the cavity length remains adapted to thermal variations, maintaining full laser gain utilization despite temperature changes.
Solution Approach 2:
The patent changes the mirror position parameter based on temperature variations. By retrieving temperature-dependent optimal positions from the lookup table and applying them to the mirror control, the system adapts the cavity length to compensate for thermal expansion and contraction, maintaining optimal gain utilization.
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
This approach significantly reduces startup time by minimizing hysteresis and mode jumping, ensuring consistent maximum gain utilization across all cavities and improving the reliability and speed of convergence.
Implementation Method 1
When the cavity is rotated at a speed Ω, the beams see, through the Sagnac effect, their optical frequencies deviate by an amount proportional to Ω.
Implementation Method 2
depending on the thermal phenomena of expansion and contraction undergone by the gyrometer between two power-ups, the length L varies
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
The invention relates to a method for positioning three translatable mirrors in a device that comprises three laser cavities arranged in a ring. Each of the three laser cavities includes an optical amplification medium that can be excited in order to generate light waves. Each of the three laser cavities also includes an optical cavity formed by a set of mirrors including two of the translatable mirrors, the length of said optical cavity depending on the position of the two translatable mirrors, wherein said two translatable mirrors can be moved within position ranges imparting to the optical cavity lengths at which the amplification medium generates at least one laser wave. Each of the three translatable mirrors is used in the formation of two of the three optical cavities. The method comprises the phase of prepositioning the three mirrors at an initial triplet of predetermined respective positions. The method also comprises the phase of simultaneously moving in translation the three mirrors within ranges having a same amplitude that is lower than or equal to the intermode of the optical cavity having the highest intermode, in order to ensure that each of the optical cavities has a length for which the amplification medium provides a maximum gain. The intensities of the laser waves flowing respectively through each of the optical cavities are measured for each triplet of positions assumed by the mirrors. The method also comprises the phase of determining, from the three triplets of mirror positions that respectively allowed each of the three cavities to provide a maximum intensity, the length of each of the three cavities at which said cavity provides a maximum intensity. The method further includes the phase of determining a single final triplet of mirror positions for simultaneously imparting to the three lengths at which they provide a maximum intensity. The method finally comprises the phase of positioning the mirrors according to the final position triplet. The invention can be used in positioning and navigation.