Segmented Flash Control via Forward Voltage Measurement

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Solution Overview

Problem

Conventional segmented flash systems experience unwanted color shifts due to temperature differences between flash segments caused by unequal current driving levels, leading to perceptible colorization in images, as they assume equilibrium temperature conditions for calculating drive currents.

Innovation Solution

Measuring the forward voltages of flash segments before or after a flash event and adjusting their brightness to equalize temperatures, allowing for optimal illumination profiles by adjusting current levels or duty cycles, and potentially using a dummy flash to correct temperature imbalances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If different current levels are used to drive flash segments to illuminate different scene regions, then the illumination profile is optimized for depth-based regions, but temperature differences cause spectrum shifts and colorization artifacts

Engineering Contradiction:

Improveillumination profileVSAvoidcolor shift

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by performing a dummy flash event before the actual flash to equalize the temperatures of all flash segments. This preliminary thermal equalization ensures that when the actual flash occurs, all segments are at similar temperatures and will not produce spectrum shifts or colorization artifacts, thus resolving the contradiction between optimized illumination profiling and color accuracy.

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If the flash system assumes equilibrium temperature conditions for calculating drive currents, then the calculation is simplified, but temperature imbalances from previous flashes cause perceptible colorization

Engineering Contradiction:

Improvecontrol calculationVSAvoidcolor accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The dummy flash event serves as a preliminary action that actively equalizes segment temperatures before the actual flash. This approach maintains the simplicity of equilibrium-based current calculations while ensuring temperature uniformity through the preliminary thermalization step, thus preserving both computational simplicity and color accuracy.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If a dummy flash is used to equalize segment temperatures, then color shifts are eliminated, but additional flash time is required

Engineering Contradiction:

Improvecolor accuracyVSAvoidflash timing

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements periodic action by inserting a dummy flash event at regular intervals or before specific flash operations. This periodic thermal equalization maintains color accuracy across multiple flash events while minimizing the overall time penalty by only performing equalization when necessary, rather than continuously.

Inventive Principle:

Principle #19Periodic 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 method effectively suppresses or eliminates color shifts by ensuring accurate illumination profiles, maintaining desired chromaticity coordinates and preventing colorization artifacts in images, even when temperature differences occur across flash segments.

Implementation Method 1

Each flash segment has an LED or other appropriate light source

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Implementation Method 2

Different temperatures in the flash segments may be the result of different current driving levels

Methodology Applied

Scientific EffectResistive heating: Joule Heating

Implementation Method 3

measuring the forward voltages of the flash segments prior to a flash event and/or following a flash event

Methodology Applied

Scientific EffectTemperature-dependent forward voltage:

Data Source

PatentUS11809064B2Method of controlling a segmented flash system

Publication Date: 2023.11.07 LUMILEDS SINGAPORE PTE LTD

AI summary

The invention describes a method of controlling a segmented flash (10) having a plurality of flash segments (S1, S2, . . . , Sn), which method comprises the steps of measuring the forward voltages (Vf1, Vf2, . . . , Vfn) of the flash segments (S1, S2, . . . , Sn); and adjusting the brightness of the flash segments (S1, S2, . . . , Sn) on the basis of the measured forward voltages (Vf1, Vf2, . . . , Vfn) to achieve a desired illumination profile (P) for the segmented flash (10). The invention further describes a segmented flash system (1) comprising a segmented flash (10) with a plurality of flash segments (S1, S2, . . . , Sn), wherein each flash segment (S1, S2, . . . , Sn) is arranged to illuminate a portion (20) of a scene (2); and a flash driver (11) adapted to perform the steps of the inventive method to adjust the brightness of the flash segments (S1, S2, . . . , Sn).