News Column

Patent Issued for DLP Edge Blend Artefact Reduction

June 25, 2014

By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from Alexandria, Virginia, by VerticalNews journalists, a patent by the inventors Priede, Jordan Evalds Huxley (Waterloo, CA); Parachoniak, Jason Patrick (Waterloo, CA), filed on May 17, 2013, was published online on June 10, 2014.

The assignee for this patent, patent number 8749581, is Christie Digital Systems, Inc. (Cypress, CA).

Reporters obtained the following quote from the background information supplied by the inventors: "DLP projectors use one or more digital micromirror devices (DMD) to reflect light and produce a picture. Each DMD may contain more than 2 million pixel mirrors, and using pulse-width modulation (PWM), each pixel mirror is capable of producing various levels of light intensity, or shades between white and black. In PWM, each pixel mirror is rapidly repositioned (generally termed `on` for white, and `off` for black) in response to data bits. As such, each pixel within a picture appears to have an intermediate intensity proportional to the fraction of time the corresponding pixel mirror is on.

"While each individual pixel mirror is subjected to a unique pulse sequence to achieve a desired pixel shade, similar pixel shades can have similar pulse sequences. Where a grouping of pixel mirrors in a given area of the DMD are called to exhibit similar shades, the end effect within that region can be a 'block' of pixels in either an on state or an off state. This effect, herein referred to as 'patterning' results in large-scale patterns at any instantaneous moment.

"For single projector applications, patterning does not pose much of an issue to the viewer. Problems arise, however, in multiple-projector applications such as multiple-projector displays where electronic edge blending in the blend zone is used. It has been noted that in the blend zone, the overlapping of the aforementioned patterning results in visual artefacts most noticeable for solid colors (such as a blue sky) during eye saccades. While these visual artefacts may take on a variety of forms, they can generally be described as irregular banding patterns of increased and decreased light intensity relative to the regions adjacent the blend zone."

In addition to obtaining background information on this patent, VerticalNews editors also obtained the inventors' summary information for this patent: "According to a first aspect, in a blend zone that uses a blend curve for overlapping at least two projector images, provided is a method of reducing visual artefacts, comprising:

"determining a maximum intensity variance for each pixel group within said blend curve, said maximum intensity variance being based on a blend multiplier selected to achieve a net light intensity specific to the location of said pixel group within said blend curve;

"for each pixel group, determining a first adjusted blend multiplier wherein said blend multiplier is increased by at least a portion of said maximum intensity variance;

"for each pixel group, determining a second adjusted blend multiplier wherein said blend multiplier is decreased by at least a portion of said maximum intensity variance; and

"adjusting the light intensity of each pixel in each said pixel group using said first and second adjusted blend multipliers specific to each said pixel group;

"wherein the average pixel intensity of each said pixel group after application of said first and second adjusted blend multipliers remains equal to said net light intensity of said pixel group within said blend curve.

"Additional aspects and advantages will be apparent to a person of ordinary skill in the art, residing in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings."

For more information, see this patent: Priede, Jordan Evalds Huxley; Parachoniak, Jason Patrick. DLP Edge Blend Artefact Reduction. U.S. Patent Number 8749581, filed May 17, 2013, and published online on June 10, 2014. Patent URL:

Keywords for this news article include: Christie Digital Systems Inc.

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Source: Journal of Engineering

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