Camera Focus Sensor Actuator Thermal Drift Compensation
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Solution Overview
Problem
Camera systems face challenges in maintaining the image sensor within the depth of focus of the lens due to thermal expansion and contraction, especially in automotive applications where temperature fluctuations cause the image sensor to drift in and out of focus, leading to out-of-focus images and increased solder stress.
Innovation Solution
An optical system with a position sensor using a magnet and magnetic field sensor to control an actuator, adjusting the position of the image sensor along the optical axis to maintain focus, and utilizing a ceramic PCB for thermal management and a laminate-based PCB for connector robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the image sensor is fixed on a rigid substrate, then structural stability is improved, but thermal expansion causes the image sensor to drift out of focus
Solution Approach 1:
The patent introduces an actuator that dynamically adjusts the position of the image sensor along the optical axis in response to temperature changes. The actuator converts electrical signals into mechanical displacement, enabling real-time compensation for thermal expansion and contraction, thus maintaining focus precision while the overall structure remains stable.
Solution Approach 2:
The system changes the physical parameter of image sensor position based on temperature conditions. A temperature sensor detects thermal changes, and a controller adjusts the actuator to modify the image sensor's axial position accordingly, compensating for thermal expansion effects and maintaining manufacturing precision under varying thermal conditions.
2Manufacturing precision
If an actuator is added to adjust image sensor position, then focus maintenance is improved, but device complexity increases
Solution Approach 1:
The actuator serves multiple functions: it adjusts the image sensor position for focus maintenance, and its position sensor provides feedback for control systems. This multi-functionality reduces the need for separate components, thereby mitigating the increase in device complexity while maintaining focus precision.
Solution Approach 2:
The system incorporates a position sensor that provides real-time feedback on the image sensor's axial position to a controller. This feedback mechanism enables closed-loop control, allowing the system to automatically maintain focus precision without requiring complex manual adjustment mechanisms, thus balancing precision with manageable system complexity.
3Temperature
If a ceramic PCB is used for thermal management, then heat dissipation is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent employs a ceramic PCB substrate that combines the thermal management benefits of ceramic materials with the electrical connectivity of PCB technology. The ceramic material provides high thermal conductivity for effective heat dissipation from the image sensor, while the PCB structure maintains ease of electrical interconnections. This composite approach balances thermal performance with manufacturing feasibility.
4Manufacturing precision
If the image sensor position is continuously adjusted, then focus maintenance is improved, but mechanical stress on solder joints increases
Solution Approach 1:
The system performs preliminary positioning adjustments during manufacturing and calibration phases to establish optimal initial positions. The actuator is designed with pre-set travel limits and controlled adjustment ranges that prevent excessive movement, thereby maintaining focus precision while avoiding movements that would generate damaging mechanical stress on solder joints during normal operation.
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 system effectively maintains the image sensor within the depth of focus across varying temperatures, reducing warpage and solder stress, and allows for efficient heat dissipation and connector durability.
Implementation Method 1
The position sensor may include a magnet and a magnetic field sensor. The magnetic field sensor may be configured to generate magnetic field data indicating a position of the substrate relative to the lens holder.
Implementation Method 2
an actuator connecting the lens holder to the substrate, and a position sensor coupled to the substrate and the lens holder
Data Source
AI summary
An apparatus includes a lens assembly that includes at least one lens that defines an optical axis, a lens holder coupled to the lens assembly, a substrate, an image sensor disposed on the substrate, and an actuator coupled between the lens holder and the substrate and configured to adjust a position of the substrate relative to the lens assembly to reposition the image sensor along the optical axis. The apparatus also includes a position sensor that includes a magnet and a magnetic field sensor. The position sensor is coupled to the substrate and the lens holder. The magnetic field sensor is configured to generate magnetic field data indicating a position of the substrate relative to the lens holder. The apparatus additionally includes circuitry configured to control the actuator based on the magnetic field data to place the image sensor within a depth of focus of the lens assembly.