Optical Scanning Lens Layout for Thermal Focus Stability
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Solution Overview
Problem
The optical scanning apparatus experiences focus position shifts due to ambient temperature changes and local temperature increases from the motor, leading to variations in beam spot diameter and reduced imaging quality.
Innovation Solution
The apparatus includes a resin-made coupling lens with a diffractive optical element to compensate for focus position shifts, and a partition enclosing the polygon mirror and motor to prevent dust contamination, with resin-made first scanning lenses to manage local temperature increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the first scanning lens is positioned close to the polygon mirror to enclose the space, then the polygon mirror is protected from dust contamination, but the local temperature around the first scanning lens increases due to motor heat, causing focus position shifting
Solution Approach 1:
The patent applies parameter changes by introducing a temperature compensation value based on the detected temperature of the first scanning lens. The focus position correction amount is calculated by multiplying a predetermined coefficient with the temperature compensation value, thereby dynamically adjusting the focus position to compensate for thermal effects and maintain imaging precision despite temperature variations.
Solution Approach 2:
The patent implements a feedback mechanism where a temperature detector continuously monitors the temperature of the first scanning lens, and the controller uses this temperature information to calculate and apply a focus position correction. This closed-loop feedback system ensures that focus position shifts caused by thermal effects are automatically compensated in real-time.
2Object-affected harmful factors
If the partition encloses the polygon mirror and motor, then dust contamination is prevented, but heat from the motor cannot dissipate, causing local temperature increase
Solution Approach 1:
The patent converts the harmful thermal effect into a useful measurement parameter. By detecting the temperature increase caused by motor operation and using it to calculate focus position compensation, the system transforms the thermal problem into a basis for maintaining imaging precision through active thermal compensation.
3Temperature
If ambient temperature changes occur, then focus position shifts due to thermal expansion, but imaging quality must be maintained
Solution Approach 1:
The patent uses parameter changes by adjusting the focus position based on detected temperature variations. The controller calculates a temperature compensation value proportional to the temperature change and applies a correction amount to the focus position, enabling the system to adapt to ambient temperature changes while maintaining stable focus and imaging quality.
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 effectively reduces focus position shifts and beam spot diameter variations, maintaining imaging quality across varying temperatures and preventing polygon mirror taint.
Implementation Method 1
The coupling lens is made of resin and has a diffractive optical element on at least one surface thereof. The coupling lens is configured to convert light emitted from the semiconductor laser into a beam.
Implementation Method 2
The optical scanning system is configured to focus the beam deflected by the polygon mirror on an imaging plane. The optical scanning system includes a first scanning lens made of resin.
Data Source
AI summary
An optical scanning apparatus includes a semiconductor laser, a coupling lens, a polygon mirror, a motor, an optical scanning system including a first scanning lens with an optical surface, a housing, a cover, and a partition with an opening closed with the first scanning lens. Shifting amounts of a focus position of a beam with respect to a reference imaging plane in a main scanning direction are in relations ΔA<0 and ΔA<ΔB<ΔC, where ΔA mm and ΔB mm are shifting amounts when the semiconductor laser, the coupling lens, and the optical scanning system are at a normal ambient temperature and at an upper-limit ambient temperature, respectively, and ΔC mm is a shifting amount when the semiconductor laser and the coupling lens are at the normal ambient temperature and the first scanning lens is at a first temperature.