Projection Device Light Source Driving Synchronization

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Solution Overview

Problem

In digital light processing (DLP) projection systems, high-pressure mercury vapor lamps used as white light sources often experience image flicker when their driving frequency is not synchronized with the rotation frequency of the color wheel, limiting the use of high-luminance lamps due to synchronization requirements, and existing solutions restrict the arbitrary setting of color wheel segment periods.

Innovation Solution

A projection device and method utilizing a color wheel with color segments at arbitrary sector angles, where the light source is driven with alternating current at a period shorter than the color wheel's rotation period, reversing polarity to synchronize with segment switching, allowing for increased discharge times and improved temperature control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If the driving frequency of the light source lamp is set to be integer times as much as the rotation frequency of the color wheel, then image flicker is prevented, but the emission luminance is reduced because high-luminance lamps cannot be employed

Engineering Contradiction:

Improveemission luminanceVSAvoidimage stability

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The invention applies periodic action by driving the light source lamp at a frequency that is integer times the color wheel rotation frequency, creating synchronized periodic cycles. This ensures that each rotation of the color wheel corresponds to complete discharge cycles of the lamp, preventing image flicker while maintaining stable color reproduction. The periodic synchronization between lamp discharge and color wheel rotation resolves the contradiction between high luminance and image stability.

Inventive Principle:

Principle #19Periodic action

2Illumination intensity

If a lamp having high emission luminance is employed, then brighter projected image is realized, but the lamp cannot be synchronized with the color wheel rotation frequency

Engineering Contradiction:

Improveprojected image brightnessVSAvoidfrequency synchronization capability

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The invention changes the driving frequency parameter of the light source lamp to be integer times the color wheel rotation frequency. This parameter adjustment allows high-luminance lamps to operate in synchronization with the color wheel, enabling both bright projected images and proper frequency synchronization. By modifying the frequency parameter, the system achieves adaptability between high-power lamps and the color wheel mechanism.

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If the driving frequency of the lamp is set to be 0.75 time as much as the rotation frequency of the color wheel, then the lamp can be driven, but the period of each segment of the color wheel is influenced and cannot be arbitrarily set

Engineering Contradiction:

Improvelamp driving capabilityVSAvoidcolor wheel segment period flexibility

Core Design Contradiction:

Ease of operationVSAdaptability or versatility

Solution Approach 1:

Instead of setting the color wheel rotation frequency to match the lamp driving frequency (conventional approach), the invention inverts the relationship by setting the lamp driving frequency to be integer times the color wheel rotation frequency. This inversion allows arbitrary setting of color wheel segment periods while maintaining proper lamp synchronization, providing both ease of operation and segment flexibility simultaneously.

Inventive Principle:

Principle #13The other way round (Inversion)

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 prevents image flicker and color drift, enables higher luminance projections, and allows for arbitrary setting of color wheel segment periods, enhancing image quality and temperature control without reducing lamp life.

Implementation Method 1

a high-pressure mercury vapor lamp which performs arc discharge is used as the white light source

Methodology Applied

Scientific EffectArc discharge: Electric Arc

Implementation Method 2

the mercury vapor lamp is driven with an alternating current

Methodology Applied

Scientific EffectAlternating current:

Implementation Method 3

a color wheel which is inserted into an optical path of the light source and in which a plurality of color segments are formed... the color segments being configured to transmit a plurality of wavelength band components in the white light in a time division manner

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Data Source

PatentUS8040440B2Projection device and projection method

Publication Date: 2011.10.18 CASIO COMPUTER CO LTD

AI summary

A projection device comprises a light source, a color wheel which is inserted into an optical path of the light source and in which a plurality of color segments are formed along a peripheral direction of the color wheel. The color segments are configured to transmit a plurality of wavelength band components in the white light in a time division manner during a rotation of the color wheel. A light source driving unit alternating-current discharges the light source at a period shorter than a rotation period of the color wheel while reverses a polarity at a timing to switch the segment of the color wheel inserted into the optical path.