Wafer-Level Pinhole Camera Module Using Mask Transfer
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Solution Overview
Problem
Existing camera modules face challenges with in-plane non-uniformity in lens characteristics, high production costs, misalignment issues, and difficulty in achieving high-resolution images due to precision limitations in lens and pinhole formation, particularly in pinhole cameras and apodization filter processing.
Innovation Solution
A wafer-level pinhole camera module is developed by applying a light-blocking resin on an inexpensive cover glass, forming a pinhole aperture using a mask transfer technique, and creating a hemispherical or Fresnel-shaped lens with high precision alignment, eliminating the need for expensive lens wafers and improving optical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a lens wafer is molded and bonded to an imaging element wafer, then the camera module can be manufactured at wafer level, but the production cost increases significantly
Solution Approach 1:
The patent replaces expensive molded lens wafers with inexpensive pinhole structures formed directly on the imaging element wafer using simple photolithography and etching processes. The pinhole acts as a disposable optical element that can be integrated into the wafer fabrication process without requiring separate lens molding and bonding steps, thereby dramatically reducing production cost while maintaining wafer-level manufacturing efficiency
Solution Approach 2:
The patent extracts the lens function from the traditional lens wafer and replaces it with a pinhole aperture formed on the imaging element wafer itself. This eliminates the need for separate lens manufacturing, molding, and bonding processes, reducing both cost and process complexity while preserving wafer-level integration benefits
2Ease of manufacture
If a pinhole camera structure is used, then the production cost is reduced, but misalignment occurs between the pinhole and imaging element due to mechanical positioning limitations
Solution Approach 1:
The patent merges the pinhole formation process with the imaging element fabrication process by forming the pinhole aperture directly on the imaging element wafer using photolithography and etching. This integration ensures that the pinhole and imaging element are manufactured together with the same precision, eliminating misalignment issues that occur with mechanical positioning of separate components
Solution Approach 2:
The patent performs preliminary alignment by forming the pinhole aperture at the correct position on the imaging element wafer during the wafer fabrication process itself, before dicing into individual chips. This preliminary positioning ensures precise alignment is built into the structure from the beginning, avoiding the need for post-assembly mechanical alignment
3Manufacturing precision
If the pinhole opening is enlarged to improve manufacturing precision, then the production becomes easier, but the image resolution deteriorates
Solution Approach 1:
The patent changes the parameter of pinhole size to an optimized small dimension that can be precisely controlled through photolithography and etching processes. By using modern semiconductor fabrication techniques, the patent achieves high manufacturing precision for small pinhole openings (on the order of micrometers), thereby maintaining both ease of manufacture and high image resolution simultaneously
4Measurement precision
If an apodization filter is added to reduce false resolution, then the image quality improves, but the device complexity and processing difficulty increase significantly
Solution Approach 1:
The patent applies local quality by creating a tapered or graded structure at the pinhole aperture itself, where the opening size varies gradually from the center outward. This local modification of the pinhole geometry provides apodization functionality directly at the aperture, reducing false resolution without requiring a separate filter component, thereby improving image quality while minimizing device complexity
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 approach enables the production of inexpensive camera modules with precise pinhole formation and improved optical alignment, reducing stray light and enhancing image quality while lowering production costs and precision requirements.
Implementation Method 1
a light-blocking resin 5 is applied on a surface of an inexpensive cover glass 4
Implementation Method 2
a microlens 2 is formed over pixels of a photosensitive portion
Data Source
Figure 1(A)(a)~2(A)(d)
Figure 2(B)(e)~4
Figure 5(a)~7(d)
AI summary
A solid state imaging device for a wafer-level pinhole camera module is provided by using a mask transfer technique to form, with a high degree of precision, pinhole openings in a light-shielding material formed upon cover glass covering the surfaces of imaging elements for wafer-level camera modules, and then dicing. Also provided is a manufacturing method therefor. Further provided is a compound-eye camera system in which a plurality of pinhole openings are formed. It is also possible to impart an apodization effect by changing the cross-sectional shape of the opening in the light-shielding material to a tapered shape to thereby change the transmission characteristics thereof.