Image Sensor Background Light Removal via Segmented Pixel Design
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Solution Overview
Problem
Existing image sensing devices face challenges in effectively removing background light, which interferes with accurate depth sensing and image capture, particularly in CMOS image sensing devices where background light can saturate pixels and affect the quality of reflected light measurements.
Innovation Solution
The proposed image sensing device incorporates a compensation element that selectively supplies a compensation current to a floating diffusion node based on a compensation control signal, allowing for the removal of background light from the pixel signal, and includes a compensation controller to generate this signal based on previous frame period pixel signals, thereby correcting for saturation and isolating the background light removal circuit from the pixel region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a background light removal circuit is integrated within the pixel region, then background light can be removed, but the pixel pitch increases and device complexity increases
Solution Approach 1:
The image sensing device is divided into two distinct regions: a first region containing pixels for capturing reflected light, and a second region containing pixels for measuring background light. This segmentation allows the background light measurement function to be separated from the main pixel array, avoiding increase in pixel pitch while enabling background light removal through differential measurement between the two regions.
Solution Approach 2:
The background light measurement function is extracted from the main pixel array and implemented as a separate pixel region. The second pixel region is specifically dedicated to measuring background light, while the first pixel region captures the reflected light signal. This extraction eliminates the need to integrate background light removal circuitry within each pixel, maintaining compact pixel pitch.
2Object-affected harmful factors
If a background light removal circuit is integrated within the pixel region, then background light can be removed, but device complexity increases
Solution Approach 1:
The device is segmented into two functional regions: first pixels for reflected light detection and second pixels for background light detection. This segmentation simplifies the overall device architecture by avoiding the need for complex in-pixel background subtraction circuitry, achieving background light removal through spatial separation and differential signal processing.
Solution Approach 2:
The second pixel region serves multiple purposes: it measures background light levels and provides a reference signal for background subtraction. This multi-functional design eliminates the need for separate background light sensing circuits, reducing overall device complexity while maintaining effective background light removal capability.
3Measurement precision
If background light removal is implemented, then measurement precision improves, but device complexity increases due to additional control circuits
Solution Approach 1:
The device implements feedback-based background light removal where the second pixel region continuously measures background light levels and feeds this information back to the signal processing circuitry. The controller uses this feedback to dynamically adjust and subtract background light components from the first pixel signals, improving depth sensing accuracy without requiring complex real-time control circuits within each pixel.
Solution Approach 2:
The second pixel region performs preliminary measurement of background light levels before the main imaging operation. This preliminary action allows the system to pre-calculate background light compensation values, which are then applied during signal processing. This approach improves measurement precision by removing background light effects while avoiding complex real-time control circuits.
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 solution enables accurate removal of background light, minimizing saturation and improving the quality of depth information obtained, while keeping the background light removal circuit separate from the pixel area to maintain design simplicity and minimize pitch effects.
Implementation Method 1
a charge sensing element suitable for generating first charges, which correspond to incident light, based on a photo control signal
Data Source
AI summary
Disclosed are an image sensing device and an operating method thereof, and the image sensing device may include a charge sensing element suitable for generating first charges, which correspond to incident light, based on a photo control signal; a reset element suitable for resetting the charge sensing element based on a reset signal; a floating diffusion node suitable for accumulating the first charges; a compensation element suitable for selectively supplying a compensation current to the floating diffusion node based on a compensation control signal; and a selection element suitable for outputting a pixel signal, which corresponds to a voltage on the floating diffusion node, to a readout line based on a selection signal.