Light Deflection Unit Rotor Frame Mass Optimization
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Solution Overview
Problem
Existing light deflection units in optical scanning apparatuses generate excessive fluid dynamic noise due to multiple balance weights, leading to increased noise frequencies and fatigue risks in rotary members, particularly when initial imbalances are high and require multiple balance corrections.
Innovation Solution
A light deflection unit design featuring a rotor frame made of a metal plate with a mass less than 3 grams and optimized thickness to minimize stress amplitude below the fatigue limit, allowing for a single balance correction to effectively reduce dynamic imbalance and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If balance weights are provided to multiple portions to correct dynamic imbalance, then the imbalance correction effectiveness is improved, but the fluid dynamic noise increases due to multiple noise sources
Solution Approach 1:
The balance correction function is segmented into two independent corrections: first correction using a balance weight on the rotor frame, and second correction using a balance weight on the rotary polygon mirror. This segmentation allows each correction to target specific imbalance components, improving overall correction effectiveness while limiting the number of balance weights that generate noise simultaneously.
Solution Approach 2:
The balance correction is implemented in periodic stages: first correction applied to the rotor frame, then second correction applied to the rotary polygon mirror at 180° opposite phase. This periodic approach distributes the correction process over time and different rotational phases, preventing cumulative noise from multiple concurrently operating balance weights.
2Object-generated harmful factors
If the rotor frame mass is reduced to minimize balance weight requirements, then the fluid dynamic noise is reduced, but the structural strength may be compromised
Solution Approach 1:
The rotor frame mass is optimized to a specific parameter range (0.5g to 3g) that simultaneously satisfies noise reduction requirements and structural strength requirements. This parameter optimization allows the thin plate structure to be sufficiently light to minimize balance weight mass and associated fluid dynamic noise, while remaining strong enough to withstand operational stresses.
Solution Approach 2:
The rotor frame is constructed from a thin metal plate (0.01mm to 0.5mm thickness) that provides sufficient structural strength despite minimal mass. The use of metal material with high strength-to-weight ratio enables the rotor frame to maintain structural integrity while keeping mass below 3g, thereby reducing the mass of balance weights and associated fluid dynamic noise.
3Reliability
If multiple balance corrections are performed to reduce initial imbalance, then the dynamic imbalance is reduced, but the frequency of balance weight applications increases leading to more noise
Solution Approach 1:
The balance correction process is segmented into two distinct correction stages targeting different components: first correction on the rotor frame addresses imbalances in the support structure, while second correction on the rotary polygon mirror addresses imbalances in the rotating element. This segmentation achieves comprehensive imbalance reduction in fewer steps compared to multiple corrections on a single component.
Solution Approach 2:
The first balance correction is applied preliminarily to the rotor frame before the second correction on the rotary polygon mirror. This preliminary action stabilizes the support structure first, creating a stable baseline that enables the second correction to more effectively address remaining imbalances, thereby reducing the total number of correction iterations needed.
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 reduces the frequency of balance weight applications, minimizes fluid dynamic noise, and prevents fatigue fracture, ensuring accurate and precise balance corrections while shortening the rise time of the optical scanning apparatus.
Implementation Method 1
When the rotary member provided with the balance weight as described above rotates, air strikes on the balance weight to generate fluid dynamic noise.
Implementation Method 2
a rotary polygon mirror configured to rotate together with the rotor frame and deflect a light beam emitted from a light source
Data Source
AI summary
The light deflection unit including a rotary member having a rotor frame formed of a plate of a metal, and a rotary polygon mirror configured to rotate together with the rotor frame and deflect a light beam emitted from a light source, in which a mass of the rotor frame is largest among masses of a plurality of members forming the rotary member, the mass of the rotor frame is smaller than 3 g, and a thickness of the plate of metal is set within a range in which a stress amplitude of a portion of the rotor frame on which a largest stress is exerted during rotation of the rotor member becomes smaller than a fatigue limit of the metal.