White reference calibration in a dual digitizer

Details White reference calibration in a dual digitizer White reference calibration in a dual digitizer

2002-10-15

2004-02-24

Coles, Edward (Department: 2622)

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

C358S474000, C358S406000, C250S208100

Reexamination Certificate

active

06697173

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to a dual digitizer capable of digitizing both transparent and reflective data media, and in particular to establishing a white reference point before reflective scans in such dual digitizers.
BACKGROUND OF THE INVENTION
A dual digitizer that can digitize both transparent media, e.g., X-ray films and overheads, as well as reflective media, e.g., paper products, has been developed. Before a reflective scan of a reflective media takes place, such dual digitizers typically require some form of calibration to establish a white and black reference point. One method of doing this in a platen scanner is to provide a white reference strip either on the bottom or top of the platen, and usually at the start of the scan position. When calibration is required, the imaging apparatus moves under the white reference providing a representative white level signal across the width of the platen. The black calibration point can be established by turning off the reflective illuminator.
In a situation where the imaging apparatus is stationary and the data medium to be digitized is moved past an optical axis, a transparent illumination system typically provides little room for insertion of a white reference material. Some applications have remedied this by feeding some form of a white calibration sheet into the imaging apparatus for calibration. However, a user has to remember to insert such a white sheet before each reflective scan. This inevitably leads to human error as users forget this extra step. In addition, this extra step takes additional time to accomplish.
Accordingly, there is a need in the art for an alternative calibration technique for establishing a white reference level in a dual digitizer to overcome the above deficiencies in the prior art.
BRIEF SUMMARY OF THE INVENTION
A dual digitizer is configured to digitize a data medium, where the data medium is a transparent data medium or a reflective data medium, the digitizer consistent with the invention includes: a reflective illuminator configured to generate a first light beam to illuminate the reflective data medium; and a transparent illuminator configured to generate a second light beam to illuminate the transparent data medium, whereby the transparent illuminator is also configured to provide a white reference signal for use in calibrating the dual digitizer for digitizing the reflective data medium when the transparent illuminator is off.
Another dual digitizer configured to digitize a data medium consistent with the invention includes: a transparent illuminator configured to generate a first light beam to illuminate a transparent medium; a reflective illuminator configured to generate a second light beam to illuminate a reflective medium; a light sensitive element configured to accept the first light beam or the second light beam and convert the first light beam and the second light beam into an analog signal representative of data recorded on the transparent data medium or the reflective data medium; and electronic processing circuitry configured to accept the analog signal and provide a digital signal representative of the data recorded on the transparent data medium or the reflective data medium, wherein the transparent illuminator is configured to reflect a first portion of the second light beam from the reflective illuminator when the transparent illuminator is off, the first portion of the second light beam providing a white reference signal for use in calibrating the dual digitizer for digitizing the reflective data medium.
A method of calibrating a dual digitizer configured to digitize a data medium, the data medium being a transparent data medium or a reflective data medium, the method consistent with the invention including the steps of: generating a light beam; and reflecting a portion of the light beam with a transparent illuminator, wherein the portion of the light beam establishes a white calibration reference signal.
Another method of digitizing a data medium consistent with the invention includes the steps of: digitizing a transparent data medium; calibrating the dual digitizer to establish a white reference signal, the calibrating step including generating a light beam, reflecting a first portion of the light beam off a transparent illuminator, and utilizing the first portion of the light beam to establish the white reference signal; and digitizing a reflective data medium.


REFERENCES:
patent: 5241406 (1993-08-01), Johnston et al.
patent: 5392100 (1995-02-01), Yoshida
patent: 5892590 (1999-04-01), Ida et al.
patent: 5995243 (1999-11-01), Kerschner et al.
patent: 6023348 (2000-02-01), Bosse et al.

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