Focus Cell Translation Assembly for Thermal Expansion and Low Friction
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Solution Overview
Problem
Existing linear slide table/ball screw focus cell designs in optical systems are over-constrained, leading to increased friction, potential binding, and thermal expansion mismatches, which result in reduced responsiveness, repeatability, and accuracy due to runout tolerances and boresight drift over temperature ranges.
Innovation Solution
A relative translation system decouples the drive mechanism from structural support, using a translation assembly with fixed and movable translation members to accommodate thermal expansion and maintain preload, while the drive mechanism includes a bearing to compensate for misalignment and provide adjustable positioning to minimize friction and misalignment issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linear slide table with ball screw drive shaft is used to move the optical element, then the optical element can be translated relative to the optical sensor, but friction increases and binding occurs due to over-constraint
Solution Approach 1:
The translation guide portion is divided into a fixed translation member and a movable translation member, with the movable member supported by rollers. This segmentation allows the drive mechanism to translate the optical element while the rollers support the movable member, reducing friction and preventing binding by distributing the load across multiple contact points.
Solution Approach 2:
Rollers are introduced as intermediary elements between the movable translation member and the fixed translation member. These rollers reduce direct sliding friction by converting it to rolling friction, thereby maintaining responsiveness and repeatability while significantly reducing the friction and binding issues associated with direct contact sliding mechanisms.
2Manufacturing precision
If tight tolerances are incorporated to account for runout binding, then alignment accuracy improves, but manufacturing cost increases
Solution Approach 1:
The design changes the tolerance parameters by incorporating adjustable positioning features in the drive mechanism and translation guide portion. This allows for post-assembly adjustment to compensate for runout tolerances and thermal expansion, achieving high alignment accuracy without requiring extremely tight manufacturing tolerances, thereby reducing manufacturing costs.
Solution Approach 2:
The movable translation member is designed with adjustable positioning capabilities that allow dynamic compensation for runout binding and thermal expansion. This dynamic adjustment feature enables the system to maintain alignment accuracy under varying conditions without requiring overly precise static manufacturing tolerances.
3Stability of the object's composition
If oversized gaps are incorporated to account for thermal expansion, then thermal stability improves, but alignment accuracy decreases due to jitter
Solution Approach 1:
The movable translation member incorporates adjustable positioning features that allow dynamic compensation for thermal expansion. This enables the system to maintain stable alignment across temperature variations without requiring oversized fixed gaps, thereby avoiding alignment jitter while preserving thermal stability.
Solution Approach 2:
The design explicitly accounts for thermal expansion by incorporating adjustable positioning mechanisms that can compensate for dimensional changes due to temperature variations. This allows the system to maintain precise alignment despite thermal effects, eliminating the need for oversized gaps that would cause jitter.
4Strength
If the drive mechanism provides structural support, then structural stability improves, but misalignment and friction increase due to non-symmetric stiffness
Solution Approach 1:
The system is segmented into distinct functional components: the drive mechanism provides translation force, while the translation guide portion (with fixed and movable members and rollers) provides structural support and alignment. This separation allows each component to be optimized for its specific function, preventing misalignment and friction issues caused by non-symmetric stiffness in a combined structure.
Solution Approach 2:
The translation guide portion acts as an intermediary between the drive mechanism and the optical element, providing symmetric structural support and alignment. This intermediary structure ensures that the optical element remains properly aligned during translation while the drive mechanism focuses solely on providing the translation force.
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 solution enhances focus cell performance by maintaining responsiveness and repeatability, minimizing boresight drift and jitter, and allowing for consistent operation over temperature variations and high loads, while reducing manufacturing costs through relaxed tolerances.
Implementation Method 1
The movable translation member can be configured to maintain preload on the fixed and movable translation members and accommodate thermal expansion
Implementation Method 2
The drive mechanism can include a bearing to facilitate rotation of the drive shaft
Data Source
AI summary
A relative translation assembly operable with a drive mechanism. The relative translation assembly can have a fixed support member, a translatable member supported by the fixed support member, and a translation guide portion to facilitate translation of the translatable member relative to the fixed support member. The translation guide portion can have a fixed translation member and a movable translation member. The movable translation member can be configured to maintain preload on the fixed and movable translation members and accommodate thermal expansion. The drive mechanism can be configured to cause translation of the translatable member relative to the fixed support member.