Imaging Pixel Pulse Detection Bandpass Filter

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Solution Overview

Problem

Conventional imaging pixels are limited in distinguishing and capturing signals with high temporal frequency content, such as laser pulses, from background signals with low temporal frequency content, leading to inadequate sensitivity in capturing laser-coded images.

Innovation Solution

An imaging pixel with a photodetector and a detector biasing circuit that filters low-frequency signals from high-frequency signals, combined with adaptive low-pass and high-pass filters and a gain stage to enhance sensitivity and separate signal components, allowing for effective bandpass processing of multiband signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a conventional pixel is used to capture both laser pulse signals and background signals, then the pixel can capture the background image, but the sensitivity to detect laser pulse signals is inadequate due to inability to distinguish high-frequency laser signals from low-frequency background signals

Engineering Contradiction:

Improvesignal detection sensitivityVSAvoidsignal frequency discrimination capability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The pixel circuit is segmented into multiple independent signal paths: a first path processes high-frequency laser pulse signals while a second path processes low-frequency background signals. This segmentation allows each path to be optimized for its specific frequency range, enabling the pixel to simultaneously capture both laser-coded images and background images with high sensitivity without interference between signal types.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If the pixel attempts to capture high-frequency laser pulse signals, then signal detection sensitivity improves, but the ability to maintain stable background image capture deteriorates due to signal interference

Engineering Contradiction:

Improvelaser pulse detection sensitivityVSAvoidbackground signal stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

Frequency-selective filtering circuits act as intermediaries between the photodetector output and the respective signal processing paths. These filters selectively pass high-frequency laser pulse signals to the first path and low-frequency background signals to the second path, preventing signal interference and maintaining stable background image capture while enabling sensitive laser pulse detection.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If a single signal path is used for both laser pulses and background signals, then the device complexity is low, but the signal separation and processing effectiveness is poor

Engineering Contradiction:

Improvecircuit structure simplicityVSAvoidsignal separation capability

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The circuit is divided into separate processing paths with dedicated filtering and amplification circuits for each signal type. The first path includes a high-pass filter and first amplifier for laser pulses, while the second path includes a low-pass filter and second amplifier for background signals. This segmentation achieves effective signal separation without excessive complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different circuit parameters are optimized for each signal path: the first path uses high-pass filtering and amplification parameters suited for high-frequency laser pulses, while the second path uses low-pass filtering and amplification parameters suited for low-frequency background signals. This parameter differentiation enables effective signal separation while maintaining manageable circuit complexity.

Inventive Principle:

Principle #35Parameter changes

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 solution enables high-sensitivity capture of laser pulse signals while minimizing noise from background variations, preserving charge information and improving the ability to distinguish high-frequency signals from low-frequency background signals.

Implementation Method 1

a photodetector that outputs charge signals in response to incident light and laser pulses

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Implementation Method 2

A detector biasing circuit is further provided that biases high-frequency signals of the charge signals that are associated with the laser pulses to follow the high frequency path. The detector biasing circuit effectively filters low-frequency signals of the charge signals from following the high-frequency path.

Methodology Applied

Scientific EffectFrequency-dependent impedance filtering: Filter (electronic)

Data Source

PatentUS9769400B2Pulse detection bandpass filter with gain stage

Publication Date: 2017.09.19 SENSORS UNLIMITED INC

AI summary

An imaging pixel is provided. The imaging pixel includes a photodetector that outputs charge signals in response to incident light and laser pulses and a high-frequency path. A detector biasing circuit is further provided that biases high-frequency signals of the charge signals that are associated with the laser pulses to follow the high frequency path. The detector biasing circuit effectively filters low-frequency signal components of the charge signals from following the high-frequency path.