Interlaced Image Sensor for Object Detection with Reduced Illumination Noise
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Solution Overview
Problem
Conventional 3D motion capture systems face performance degradation due to low contrast between objects and background, leading to latency issues in distinguishing foreground from background, especially when background objects are close to the object of interest, resulting in reduced signal-to-noise ratio and noise introduction from image shift during processing.
Innovation Solution
Implementing an interlaced mode operation for image sensors, where only half the number of image lines are read out at a time, reducing integration time and noise, allowing for simultaneous capture and comparison of images under different illuminations to enhance noise removal and maintain high frame rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional image sensors read out all lines sequentially, then complete image data is obtained, but integration time increases causing latency and allowing noise to accumulate
Solution Approach 1:
The image sensor array is divided into multiple sets of alternating lines (first set and second set). Each set is read out separately during different exposure periods, allowing the integration time for each set to be reduced while maintaining complete image data coverage through sequential reading of segmented line groups.
Solution Approach 2:
The sensor controller is configured to read out the first set of lines during a first exposure period and then read out the second set of lines during a second exposure period. This preliminary sequential reading allows the sensor to maintain high frame rates by preparing data in advance without requiring all lines to be read simultaneously, thereby reducing overall integration time latency.
2Measurement precision
If narrowband illumination is used to enhance object discrimination, then object-background contrast improves, but signal-to-noise ratio decreases when background objects are close to the object of interest
Solution Approach 1:
The image sensor divides the pixel array into alternating line sets that are read out separately. This segmentation allows the system to process different portions of the image simultaneously under different illumination conditions, improving the ability to distinguish objects from background while maintaining sufficient signal-to-noise ratio through parallel processing of multiple line sets.
Solution Approach 2:
The patent introduces a temporal dimension to the line reading process, where different line sets are read during different time periods. This allows the system to effectively process multiple spatial regions simultaneously, improving object discrimination capability without being limited by the signal-to-noise ratio issues that would occur if all lines were read simultaneously under a single illumination condition.
3Reliability
If two successive images are captured under different illuminations for noise removal, then noise is reduced, but latency increases due to the time required to obtain and process both images
Solution Approach 1:
Instead of capturing two complete successive images, the sensor segments the pixel array into alternating line sets and reads them out during different exposure periods. This allows noise reduction processing to begin immediately as lines are read, eliminating the latency associated with waiting for two complete images to be captured and processed sequentially.
Solution Approach 2:
The sensor controller continuously reads out different line sets during overlapping exposure periods, maintaining continuous useful action. The first set of lines is read during a first exposure while the second set is read during a second exposure that overlaps with the readout of the first set, ensuring continuous progress on noise reduction without idle waiting time.
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 significantly reduces latency and noise, enabling efficient motion characterization and object tracking by comparing adjacent rows sequentially, thus improving throughput and maintaining sufficient image resolution for motion detection.
Implementation Method 1
motion of the object(s) is detected and tracked based on reflected source light, which is sensed by one or more cameras directed at the scene
Implementation Method 2
Both types of image sensor typically include an array of photosensitive elements (pixels) that collect charge carriers in response to illumination
Data Source
AI summary
An image sensor frame rate can be increased by “interlaced” mode operation whereby only half the number of lines of an image is transported to the readout circuitry. This halves the integration time but also halves the resolution of the sensor. Accordingly, in one embodiment, an image sensor operated in an interlaced fashion is first exposed to a scene under a first form of illumination (e.g., narrowband illumination), and a first set of alternating (horizontal or vertical) lines constituting half of the pixels is read out of the array; the sensor is then exposed to the same scene under a second form of illumination (e.g., existing ambient illumination with the illumination source turned off), and a second set of alternating lines, representing the other half of the pixel array, is read out. The two images are compared and noise removed from the image obtained under narrowband illumination.