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AssigneeNCS Pearson, Inc.
InventorsJames L. Maciey, Jack J. Raymakers, Jerry D. Wheeler
Estimating the term…
An optical reading head system has a calibrated pixel output, consisting of a discrete value for each of a plurality of pixels. The system has a scanning station with an exposure region that includes an image region and a detector including an array of photosensitive sites that sense reflected light from the exposure region during a detector exposure period to generate a pixel output profile of the image region. There are a plurality of light sources for lighting the exposure region. Each light source emits an individually controllable amount of light to the exposure region during a detector exposure period such that the system's pixel output is acceptably calibrated. A calibration medium is supplied with a calibration region, and a target pixel output profile is defined for the calibration. The individually controllable light sources are adjusted to make the pixel output profile acceptably within range of the target pixel output profile.
An optical reading head system having an acceptably calibrated pixel output, the system comprising:
An optical reading head system having a calibrated pixel output, the pixel output comprising a discrete value for each of a plurality of pixels, the system comprising:
A scannable sheet for receiving user indicia that are to be detected during scanning with an optical scanner system having a selectable first plurality of light sources emitting an individually controllable amount of light to the exposure region during a detector exposure period and a selectable second plurality of light sources, said second plurality of light sources having a different spectral quality than the first plurality of light sources and emitting an individually controllable amount of light to the exposure region during a detector exposure period, said sheet comprising:
Dependencies are inferred from the claim text.
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Scanning arrangements , i.e. arrangements for the displacement of active reading or reproducing elements relative to the original or reproducing…:…
Feeding arrangements: the sheet feeding apparatus serving an auxiliary function, e.g. as a white reference
Pictorial communication
Term ended 12 Dec 2016 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
The present invention relates generally to the field of optical mark reading (OMR) and data image-scanning and capture from one or both sides of documents that are transported across a scanning station by a mechanical feeding means. More particularly, the present invention relates to an improved optical light-source, digital reading or detecting head apparatus, and the supporting data processing logic to accurately and consistently calibrate the illumination source for the scanning station and/or the image detector such that the true darkness level of pre-printed or manually entered data may be extracted from each scanned document.
Optical read head systems (hereinafter referred to as ORHS), that capture information printed, stamped, photographed, photocopied, manually entered, or otherwise placed on either one or both sides of a document surface are well known in the prior art. There are numerous applications, in the field of document scanning—both OMR and image-capture—that require a spectral discrimination capability within the ORHS. For example, a given OMR form may be pre-printed in red ink (e.g., the data-entry marking “bubble” positions, etc.) and the user permitted to enter the data with any marking instrument but red: for example, a lead-pencil and/or black/blue/green ball-point pens or felt-tip markers. Spectral discrimination permits the user marks to be detected while the red ink is not detected.
It will be appreciated that users desire the flexibility to utilize OMR and image-capture forms that may be pre-printed with a wide variety of colored inks, and offer marking entry with a wide range of marking instruments. Accordingly, a sophisticated ORHS must offer the means to quickly and selectively set the spectral parameters to achieve the desired range of data detection and the desired range of pre-printed ink rejection or non-detection.
FIG. 1 is a perspective view of an optical reading head system scanning station.
FIG. 2 is a block diagram of a control system for an ORHS according to the present invention.
FIG. 3 is a cross-sectional, schematical representation of an embodiment of an ORHS according to the present invention.
A. Optical Reading Head System—General Overview
With reference to FIGS. 1 to 4 and 5A-5F, in pertinent part, the optical reading head system (ORHS) 100 of the type contemplated for the present invention generally includes a planar scanning station 10 through which a scanned document (or other sheet of media) 12 can be transported, one or more illumination strips 20a, 21a above the plane of the scanning station 10 (as seen in FIG. 3), a detector module 35, which includes a camera 30a, above the plane of the scanning station 10, and associated control/logic circuitry 32a. As seen in FIG. 1, a mirror assembly 31a is used to bring the image formed at the upper side of the scanning station 10 to the detector camera 30a.
Because many scanning applications require scanning of both sides of the document 12, below the plane of the scanning station 10 there is a symmetrically constructed configuration consisting of illumination strips 20b, 21b, detector camera 30b, mirror assembly 31b, and associated control/logic circuitry 32b. Because operations above and below the plane of the scanning station 10 are essentially identical (except for a slight relative displacement of the central viewing axes 34a, 34b of cameras 30a, 30b, the following discussion will be primarily with reference only to structures and operations above the plane of scanning station 10.