Projector Lamp Drive Frequency Control for Flicker Reduction

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Solution Overview

Problem

Conventional projectors using alternating-current-driven discharge lamps face limitations in drive frequency synchronization with color wheel segments, leading to inaccurate image projection and flicker issues, especially when dealing with different television systems like NTSC and PAL.

Innovation Solution

The projector raises the drive frequency of the lamp during the period when the transparent segment of the color wheel is in the optical path, allowing for synchronized tone control and reduced flicker by adjusting the drive frequency and voltage in accordance with temperature conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the drive frequency is synchronized with color wheel segments, then accurate image projection is achieved, but the drive frequency is limited to integral multiples of 60 Hz or 50 Hz and not higher than 240 Hz or 200 Hz

Engineering Contradiction:

Improveimage projection accuracyVSAvoiddrive frequency range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent divides the color wheel rotation period into multiple segments corresponding to different color filters (R, G, B, W). By generating drive signals that are synchronized with these segments, the system achieves accurate image projection while enabling drive frequencies that are integral multiples of the base frequency, thus expanding the usable frequency range beyond traditional limitations.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs dynamic drive signals with varying high and low levels that are timed to coincide with the passage of different color segments through the optical path. This dynamic synchronization allows the system to adapt the drive frequency to different operating conditions while maintaining image accuracy, effectively resolving the contradiction between precision and frequency flexibility.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the drive frequency is increased to improve light-emitting efficiency and suppress flicker, then service life and brightness are improved, but synchronization with color wheel segments becomes difficult

Engineering Contradiction:

Improveservice life and flicker suppressionVSAvoidsynchronization accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes the drive frequency parameter to integral multiples of the base frequency (60 Hz or 50 Hz), allowing frequencies up to 240 Hz or 200 Hz. This parameter adjustment improves light-emitting efficiency and suppresses flicker while maintaining synchronization through the segment-based timing approach, thus resolving the contradiction between reliability and synchronization accuracy.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If the drive frequency is limited to integral multiples of 60 Hz or 50 Hz, then synchronization with color wheel is simplified, but the ability to optimize temperature conditions and suppress flicker is reduced

Engineering Contradiction:

Improvesynchronization control complexityVSAvoidflicker suppression and temperature optimization

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent creates a universal synchronization system that works with both NTSC (60 Hz) and PAL (50 Hz) television systems by designing the drive signal generation to adapt to either base frequency. The segment-based approach provides a unified method that simplifies control complexity while maintaining the ability to optimize temperature conditions and suppress flicker across different system types.

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 approach enables stable image projection with improved brightness and reduced flicker, maintaining the electrode temperature within an optimal range and extending the service life of the light source while allowing for adjustable frequency and voltage control.

Implementation Method 1

a light source lamp 19 which is an alternating-current-driven discharge lamp

Methodology Applied

Scientific EffectElectrical discharge: Electric Arc

Implementation Method 2

a color wheel 20 which includes color segments for transmitting color lights

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Data Source

PatentUS7841723B2Projector using lamp, method and program for controlling discharge lamp light source

Publication Date: 2010.11.30 CASIO COMPUTER CO LTD

AI summary

A projector comprises an alternating-current-drive lamp, a rotating color wheel which includes color segments for transmitting color lights and is disposed in an optical path from the lamp, the color segments including a transparent segment, a projection unit configured to form an optical image by the color lights transmitted through the color wheel, and a light source control unit configured to raise a drive frequency of the lamp in a period in which the transparent segment of the color wheel is present in the optical path from the lamp.