Image Sensor Package Frame for Thermal Focus Compensation
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Solution Overview
Problem
In imaging devices used in vehicles, focus shifts due to thermal expansion of constituent members, leading to a decrease in resolution, which existing fixed-focus types struggle to effectively mitigate.
Innovation Solution
An imaging device design featuring a package frame with a larger coefficient of linear expansion than the lens holder, including a wall portion extending perpendicular to the wiring substrate, with a gap between the frame and the image sensor package, and the lens holder's wall portion facing the package frame, allowing the distance between the image sensor and lens to remain constant or change with temperature sensitivity to compensate for thermal effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed-focus type imaging device is used to reduce cost and simplify structure, then device complexity is reduced, but focus shift occurs due to thermal expansion causing resolution decrease
Solution Approach 1:
The patent applies thermal expansion by selecting materials with different coefficients of linear expansion for the lens holder and image sensor package. The lens holder uses a material with a larger coefficient of linear expansion than the image sensor package, causing the lens holder to expand more with temperature increase. This expansion moves the lens unit away from the image sensor, compensating for the focus shift that would otherwise occur due to thermal expansion of the entire device. This principle directly resolves the contradiction by using controlled thermal expansion to maintain focus and resolution while keeping the device structure simple and fixed-focus.
2Measurement precision
If the configuration size is increased to accommodate higher pixel count, then imaging quality is improved, but thermal expansion of constituent members increases causing greater focus shift
Solution Approach 1:
The patent addresses thermal expansion issues in high-pixel-count devices by implementing a differential expansion mechanism. The lens holder is designed with a material having a larger coefficient of linear expansion than the image sensor package, creating a controlled expansion differential. When temperature increases, the lens holder expands more than the image sensor package, causing the lens unit to move away from the sensor in a controlled manner that compensates for focus shift. This allows the device to maintain high imaging quality with increased pixel count while counteracting the adverse effects of thermal expansion through material selection and structural design.
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 design effectively curbs the reduction in resolution caused by temperature changes, maintaining image quality by offsetting thermal expansion effects and compensating for lens unit characteristic changes.
Implementation Method 1
the package frame includes a material having a larger coefficient of linear expansion than a material of the lens holder
Data Source
AI summary
An imaging device that includes a wiring substrate, an image sensor package mounted on the wiring substrate, a package frame attached to a light receiving surface side of the image sensor package, and a lens holder arranged to cover the package frame and holding a lens unit so that the lens unit faces the light receiving surface of the image sensor package. The package frame includes a material having a larger coefficient of linear expansion than a material of the lens holder, and includes a wall portion that extends in a direction perpendicular to the wiring substrate toward the wiring substrate. A gap is provided between the wall portion of the package frame and the image sensor package, and between an end of the wall portion of the package frame and the wiring substrate. The lens holder includes a wall portion facing the wall portion of the package frame. An end of the wall portion of the lens holder is fixed to the end of the wall portion of the package frame while being separated from the wiring substrate.