Auto-Homing Tunable Filter for Projector Imaging Systems

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Solution Overview

Problem

Standard infrared (IR) projector imaging systems face challenges due to spectral shifts in light sources, leading to increased ambient light leakage and reduced system performance, as fixed IR band-pass filters are designed to accommodate these shifts but end up allowing excessive ambient light, compromising image quality.

Innovation Solution

The implementation of a tunable IR band-pass filter that automatically adjusts its full width at half maximum (FWHM) to match the light source's spectral drift, minimizing ambient light leakage while maintaining light transmission, which can be applied across various wavelength bands including IR and visible ranges.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If a fixed IR band-pass filter with wide FWHM is used to accommodate spectral drift, then light source transmission is improved, but ambient light leakage increases

Engineering Contradiction:

Improvelight source transmissionVSAvoidambient light leakage

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent employs a tunable band-pass filter instead of a fixed filter, allowing the filter's center wavelength and FWHM to be dynamically adjusted to match the light source's spectral characteristics. This dynamic adaptation enables the system to maintain optimal light transmission while minimizing ambient light leakage by precisely tracking the light source's spectral drift.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the filter parameters (center wavelength and FWHM) to match the light source's spectral parameters. By continuously or periodically adjusting these parameters based on the light source's actual spectral output, the system optimizes the energy ratio without requiring an excessively wide FWHM that would allow ambient light leakage.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If a fixed IR band-pass filter with narrow FWHM is used to reduce ambient light leakage, then ambient light rejection is improved, but light source transmission decreases

Engineering Contradiction:

Improveambient light leakageVSAvoidlight source transmission

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The tunable filter dynamically adjusts its FWHM to match the light source's spectral width, ensuring that the filter is neither too narrow (blocking light source) nor too wide (allowing ambient light). This dynamic matching optimizes both light source transmission and ambient light rejection simultaneously.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system uses feedback from spectral measurements to adjust the filter parameters. By measuring the light source's spectral output and using this information to tune the filter, the system ensures optimal transmission of the light source while maintaining rejection of ambient light.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If the FWHM is increased to accommodate spectral drift, then spectral drift tolerance is improved, but energy ratio decreases

Engineering Contradiction:

Improvespectral drift toleranceVSAvoidenergy ratio

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

Instead of using a statically wide FWHM to accommodate spectral drift, the system dynamically tracks the light source's spectral drift by continuously or periodically tuning the filter's center wavelength and FWHM. This dynamic approach provides spectral drift tolerance while maintaining a narrow enough FWHM to preserve the energy ratio.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system performs preliminary spectral measurements of the light source to determine the appropriate filter parameters before image capture. This preliminary action allows the filter to be pre-configured to match the light source's spectral characteristics, ensuring optimal performance without requiring an excessively wide FWHM.

Inventive Principle:

Principle #10Preliminary action

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 significantly improves image quality by reducing ambient light leakage, enhancing the energy ratio and overall system performance, allowing for better image capture and processing, especially in dynamic lighting conditions.

Implementation Method 1

a tunable filter configured to auto-home into a filter state that reduces ambient light leakage into the image sensor

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Data Source

PatentUS11092492B2Projector imaging system with auto-homing tunable filter

Publication Date: 2021.08.17 UNISPECTRAL LTD

AI summary

Some embodiments are directed to an imaging that includes an image sensor; a tunable filter; and a controller operatively connected to the tunable filter and to the image sensor. The imaging system is configured to: tune the tunable filter to a plurality of filter states. The image sensor acquires, at each state of the plurality of states, an image of an object, to provide different images of the object. The controller calculates a state related score, for each state that is indicative of one or more properties of at least one subset of pixels of the at least one image acquired at the state, to provide a plurality of state related scores; and determines, based on at least one of the plurality of state related scores, a desired state of the tunable filter that satisfies a desired state related score criterion; and sets the tunable filter.