Fresnel OpticsA Reflexite Company The Management of Light ®

Fresnel Lenses in Rear Fresnel Lenses in Rear Projection DisplaysProjection Displays

SID ProceedingsSID ProceedingsJune 2001June 2001

bybyArthur Davis, Robert C. Bush,Arthur Davis, Robert C. Bush,

John C. Harvey and Michael F. Foley, PhDJohn C. Harvey and Michael F. Foley, PhD

The Management of Light ®Fresnel A Reflexite Company

Fresnel OpticsA Reflexite Company The Management of Light ®

AbstractA plastic Fresnel lens positioned just before the diffusion screA plastic Fresnel lens positioned just before the diffusion screen en in a projection system can provide significantly superior cornerin a projection system can provide significantly superior cornerillumination, enhancing overall display luminance uniformity. illumination, enhancing overall display luminance uniformity. Fresnel lenses are also used within the light engine to collimaFresnel lenses are also used within the light engine to collimate te light through the LCD panel and focus light through the projectilight through the LCD panel and focus light through the projection on lens. Disadvantages include the added cost of the lenses, lens. Disadvantages include the added cost of the lenses, ghosting, printout of the Fresnel rings and moirghosting, printout of the Fresnel rings and moiréé patterns. patterns. Birefringence is important to control in polarizationBirefringence is important to control in polarization--sensitive sensitive applications.applications.

Without reduction of ghosting artifacts, Fresnel lenses will havWithout reduction of ghosting artifacts, Fresnel lenses will have e limited application in textlimited application in text--based RP systems. Ghosting is based RP systems. Ghosting is described in some detail including how it is caused, quantified described in some detail including how it is caused, quantified and reduced. Efforts to reduce cost and birefringence will also and reduced. Efforts to reduce cost and birefringence will also be be discussed.discussed.

Fresnel OpticsA Reflexite Company The Management of Light ®

Fresnel Lens Background•• Augustin Jean Augustin Jean

FresnelFresnel–– French PhysicistFrench Physicist–– 17881788--18271827–– Wave Theory of Wave Theory of

LightLight–– First use of First use of

Fresnels: Fresnels: Lighthouse Lighthouse LensesLenses

Fresnel OpticsA Reflexite Company The Management of Light ®

The Fresnel Lens

•• Periodic refractive Periodic refractive approximation to approximation to asphereasphere–– SlopesSlopes–– DraftsDrafts

Fresnel OpticsA Reflexite Company The Management of Light ®

Applications

•• Single Panel LCD Single Panel LCD ProjectorsProjectors

•• Overhead ProjectorsOverhead Projectors•• Rear Projection Rear Projection

DisplayDisplay–– Rear Projection Rear Projection

TelevisionsTelevisions–– Rear Projection Rear Projection

MonitorsMonitors

Fresnel OpticsA Reflexite Company The Management of Light ®

Single Panel LCD Projector

•• Fresnel Lenses can increase the Fresnel Lenses can increase the collected light in single panel LCD collected light in single panel LCD displaysdisplays

Fresnel OpticsA Reflexite Company The Management of Light ®

Overhead Projectors

Transmissive Reflective

Fresnel OpticsA Reflexite Company The Management of Light ®

Rear Projection Display

•• Collimation Collimation increases overall increases overall display luminancedisplay luminance

Luminance enhancement using Fresnel Lens

Fresnel OpticsA Reflexite Company The Management of Light ®

Fresnel Lens ImagingCorrect Orientation Incorrect Orientation

•• Minimize draft Minimize draft lossloss–– Judicious draft Judicious draft

designdesign–– Proper lens Proper lens

orientationorientation

Fresnel OpticsA Reflexite Company The Management of Light ®

Ghosting

•• Caused by Caused by internal internal reflectionsreflections

•• 3.9% 3.9% -- 10%10%•• Limits high Limits high

contrast contrast applicationsapplications

•• Multiple GhostsMultiple Ghosts

Fresnel OpticsA Reflexite Company The Management of Light ®

Ghost Suppression

•• Lens tintingLens tinting•• Draft blackeningDraft blackening•• Broadband antiBroadband anti--reflection coatingreflection coating•• Proprietary processes and designsProprietary processes and designs

–– Negligible ghostingNegligible ghosting–– Low f/#Low f/#–– High resolutionHigh resolution–– Successfully implemented in RPM Successfully implemented in RPM

applicationsapplications

Fresnel OpticsA Reflexite Company The Management of Light ®

Moiré•• Fresnel rings can Fresnel rings can

cause a moircause a moiréépatternpattern with the with the lines of a lenticular lines of a lenticular diffuserdiffuser

•• With proper With proper engineering of the engineering of the pitch, moirpitch, moiréé can be can be reduced to reduced to acceptable contrast acceptable contrast levelslevels

Fresnel OpticsA Reflexite Company The Management of Light ®

Metrology

Fresnel OpticsA Reflexite Company The Management of Light ®

ManufacturingReplication Processes

Cross section of injection molded Fresnel Cross section of compression molded Fresnel