Back-Side Illuminated Image Sensor Light Capture Layer

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Solution Overview

Problem

Conventional imaging devices in augmented and virtual reality systems face interference from background ambient light, which affects the signal-to-noise ratio and requires costly filtering mechanisms or background light subtraction algorithms, limiting light collection efficiency.

Innovation Solution

A back-side illuminated time-of-flight image sensor with a light capture layer that captures ambient light and converts it to an electrical current before it reaches the image sensor, allowing only specific wavelengths, such as infrared light, to pass through, thereby preventing interference and improving signal-to-noise ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional optical filtering techniques are used to limit ambient light interference, then ambient light interference is reduced, but manufacturing cost increases

Engineering Contradiction:

Improveambient light interferenceVSAvoidmanufacturing cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent extracts and removes the harmful ambient light (visible spectrum) from the light path before it reaches the image sensor, while allowing the desired infrared light to pass through. This is achieved by eliminating the need for costly optical filters by using the semiconductor substrate itself to absorb visible light.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent converts the harmful effect of ambient light into a beneficial function by using the light capture layer to absorb visible light and generate electrical current that is then discarded. The harmful ambient light becomes a source of electrical current that can be safely removed, protecting the image sensor without requiring expensive filters.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Object-affected harmful factors

If background light subtraction algorithms are used at the circuit level, then ambient light interference is accounted for, but light collection efficiency decreases

Engineering Contradiction:

Improveambient light interferenceVSAvoidlight collection efficiency

Core Design Contradiction:

Object-affected harmful factorsVSProductivity

Solution Approach 1:

The patent performs preliminary action by capturing and removing ambient light before it reaches the image sensor, rather than attempting to subtract it afterward. The light capture layer absorbs visible light and converts it to electrical current that is discarded, preventing ambient light from interfering with the image sensor in the first place.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If a light capture layer is added to convert ambient light to electrical current, then signal-to-noise ratio improves, but device complexity increases

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent merges the light capture layer with the existing semiconductor substrate of the image sensor, creating an integrated structure where the substrate serves dual purposes: as both the imaging element and the ambient light filter. This integration avoids adding separate components and leverages the existing semiconductor material properties.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The semiconductor substrate is given multiple functions: it serves as both the image sensor element that detects infrared light and the light capture layer that absorbs visible light. The same material and structure perform both imaging and filtering functions, eliminating the need for separate filter components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 enhances the signal-to-noise ratio by eliminating ambient light interference and reduces the need for ambient-light-blocking filters and background light subtraction algorithms, increasing light collection efficiency while reducing costs.

Implementation Method 1

the light capture layer may include a photosensitive material that is dimensioned such that (1) a first portion of light having less than a predetermined wavelength is captured by the light capture layer, producing a current in the light capture layer

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS10438986B1Apparatuses, systems, and methods for selectively suppressing ambient light in an image sensor

Publication Date: 2019.10.08 META PLATFORMS TECHNOLOGIES LLC

AI summary

An imaging device may include (1) an aperture, (2) a lens positioned to direct light received through the aperture to a front side of an image sensor; and (3) the image sensor. The image sensor may include (1) a light capture layer including a photosensitive material that is dimensioned such that (a) a first portion of the light having less than a predetermined wavelength is captured by the light capture layer, producing a current, and (b) a second portion of the light having at least the predetermined wavelength passes through the light capture layer, (2) a conduction pathway that conducts the produced current to a current sink, and (3) an image sensor layer that includes at least one image sensor element positioned to receive the second portion of the light that passes through the light capture layer. Various other devices, systems, and methods are also disclosed.