Color Image Sensor Array with On-Chip Crosstalk Test Patterns
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Solution Overview
Problem
Color image sensors suffer from crosstalk issues due to imperfect light blocking by color filters and optical, electrical, and scattering effects, leading to degradation of sensor spatial resolution and color fidelity.
Innovation Solution
Incorporating color-filter-based test patterns on the same integrated circuit as the color image sensor, these test patterns allow for the extraction of crosstalk parameters, which are then used in image signal processing to correct for pixel-to-pixel crosstalk, either on-chip or off-chip, using hardware or software.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If color filters are used to capture color image data, then color information can be collected, but crosstalk between neighboring pixels and colors occurs due to imperfect light blocking
Solution Approach 1:
Test patterns are incorporated into the sensor array during manufacturing to pre-characterize crosstalk parameters. This preliminary measurement enables subsequent correction algorithms to compensate for crosstalk effects, resolving the contradiction between capturing color information and maintaining color accuracy.
Solution Approach 2:
The system uses test pattern measurements to generate correction coefficients that are applied to correct color image data. This feedback loop compensates for crosstalk, maintaining color fidelity despite the presence of light scattering and imperfect filter blocking.
2Manufacturing precision
If color filters with small pitch are used to increase resolution, then spatial resolution improves, but optical diffraction and scattering increase causing more crosstalk
Solution Approach 1:
Test patterns are built into the sensor to pre-measure crosstalk characteristics at the actual small pitch dimensions. This enables correction algorithms to compensate for the increased diffraction and scattering effects that result from using small pitch filters.
Solution Approach 2:
Test patterns replicate the actual pixel structure and color filter arrangement at reduced scale. By copying the real sensor geometry, the test patterns accurately capture crosstalk behavior, enabling precise correction of high-resolution images.
3Measurement precision
If test patterns are added to the integrated circuit, then crosstalk parameters can be extracted for correction, but device complexity increases
Solution Approach 1:
Test patterns are merged with the color image sensor array on the same integrated circuit substrate. This integration allows crosstalk characterization to be performed using the same manufacturing process and pixel structure, minimizing additional complexity while enabling precise measurement.
Solution Approach 2:
The test patterns use the same color filter and pixel structures as the main sensor array, making the system multi-functional. The same hardware infrastructure serves both image capture and crosstalk characterization purposes, reducing overall 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
The method enhances color fidelity by accurately correcting for crosstalk, minimizing the impact of process variations and improving image quality in electronic devices like digital cameras.
Implementation Method 1
each covered by a respective color filter. For example, the color filters may be arranged in a Bayer pattern, having alternating red-green and green-blue rows. The red filters pass red light and ideally block blue and green light.
Implementation Method 2
Other sources of optical cross talk include light scattering and reflection at color filter array (CFA) and micro-lens boundaries, interconnect metal wires, and light diffraction due to the small size of each color filter pitch.
Implementation Method 3
Other sources of optical cross talk include light scattering and reflection at color filter array (CFA) and micro-lens boundaries, interconnect metal wires
Implementation Method 4
Additionally, there is electrical cross talk, caused by photo-carrier diffusion in the silicon substrate beneath pixels of different colors.
Data Source
AI summary
An integrated circuit comprises a semiconductor substrate and a color image sensor array on the substrate. The color image sensor array has a first configuration of color pixels for collecting color image data, and at least one crosstalk test pattern on the substrate proximate the color image sensor array. The crosstalk test pattern includes a plurality of color sensing pixels arranged for making color crosstalk measurements. The test pattern configuration is different from the first configuration.