CAPD Pixel Array IR Drop Noise Reduction
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Solution Overview
Problem
Current image sensing devices face challenges in accurately measuring distances due to noise caused by IR drops, which affect the consistency and accuracy of pixel signals, especially in CAPD pixel arrays used in Time of Flight (ToF) methods.
Innovation Solution
The implementation of CAPD pixels with controlled pixel resistance, where the distance and structure of electrical contact taps and photo-electric conversion areas are optimized to minimize IR drops, ensuring uniform pixel signal intensity across the array by varying the resistance and structure based on the distance from the demodulation driver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the pixel array is extended to increase the number of pixels, then the coverage area is improved, but the IR drop noise increases due to longer signal line distances from the demodulation driver
Solution Approach 1:
The pixel array is divided into multiple regions (first region, second region, third region) with different pixel resistance characteristics. This segmentation allows each region to be optimized independently for its distance from the demodulation driver, reducing IR drop noise while maintaining large coverage area.
Solution Approach 2:
Different regions of the pixel array are assigned different pixel resistance values based on their location. Pixels closer to the demodulation driver have lower resistance, while pixels farther away have higher resistance. This local quality variation compensates for IR drop effects in different areas of the extended pixel array.
2Ease of manufacture
If all pixels are designed with uniform structure, then the manufacturing process is simplified, but the pixel signal intensity becomes non-uniform due to varying distances from the demodulation driver
Solution Approach 1:
The patent implements local quality by varying pixel resistance based on spatial position. Pixels in different regions (first, second, third regions) have different resistance characteristics tailored to their distance from the demodulation driver, ensuring uniform signal intensity across the entire array despite structural variations.
Solution Approach 2:
The pixel resistance parameter is changed according to the pixel's position in the array. By adjusting this electrical parameter based on location, the patent compensates for IR drop effects and achieves uniform signal intensity without requiring complete structural uniformity across all pixels.
3Manufacturing precision
If the distance between electrical contact taps is increased to reduce resistance, then the pixel resistance is improved, but the photocharge capture area is reduced
Solution Approach 1:
The patent applies local quality by setting different pixel resistance values for different regions of the array. Pixels in regions farther from the demodulation driver have higher resistance to compensate for IR drop, while pixels closer to the driver have lower resistance. This allows each pixel to optimize its resistance independently based on location.
Solution Approach 2:
The patent changes the resistance parameter of individual pixels based on their spatial position. By adjusting this electrical characteristic according to location, the system achieves uniform signal intensity across the array without requiring all pixels to have identical dimensions or photoelectric conversion areas.
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 effectively reduces noise from IR drops, leading to more accurate and consistent distance measurements by maintaining uniform pixel signal intensity, thereby enhancing the precision of distance calculations in image sensing devices.
Implementation Method 1
capture photocharges generated by light reflected from an object and incident on the image sensing pixel array and migrating by the current
Data Source
AI summary
An image sensing device for measuring a distance between the image sensing device and a target object is disclosed. The image sensing device may include a plurality of image sensing pixels formed in a substrate, each image sensing pixel including a first electrical contact tap and a second electrical contact tap structured to generate a current in the substrate and capture photocharges generated by light reflected from an object and incident on the image sensing pixel array and migrating by the current to measure a distance to the object by performing demodulation operations based on the photocharges, and a demodulation driver coupled to the image sensing pixel array to apply, to the first electrical contact tap and the second electrical contact tap, a first demodulation control signal and a second demodulation control signal for generating the current, respectively.