Optical: systems and elements – Optical modulator – Light wave directional modulation
Reexamination Certificate
2003-03-07
2004-10-26
Phan, James (Department: 2872)
Optical: systems and elements
Optical modulator
Light wave directional modulation
C356S402000, C250S226000
Reexamination Certificate
active
06809855
ABSTRACT:
Cross-reference and incorporation by reference is also made to the following copending and commonly assigned U.S. patent applications: U.S. application Ser. No. 09/448,987, filed Nov. 24, 1999, Attorney Docket No. D/99511Q, now U.S. Pat. No. 6,351,3087, issued Feb. 26, 2002, and U.S. application Ser. No. 091449,263, filed Nov. 24, 1999, Attorney Docket No. D/99511Q1, both by Lingappa K. Mestha, now U.S. Pat. No. 6,538,770 issued Mar. 25, 2003; Continuation-In-Part application Ser. No. 09/535,007, filed Mar. 23, 2000, by the same Fred F. Hubble, Ill and Joel A. Kubby, Attorney Docket No. D/99511i, now U.S. Pat. No. 6,384,918 issued May 7, 2002, claiming priority from U.S. application Ser. No. 09/448,774, filed Nov. 24, 1999 Attorney Docket No. D/99511 (abandoned); and application Ser. No. 09/862,247, filed May 22, 2001, by Jagdish C. Tandon and Lingappa K. Mestha, Attorney Docket No. D/99660, now U.S. Pat. No. 6,621,576 issued Sep. 16, 2003.
Disclosed in the embodiments herein is an improved, low cost, color spectrophotometer for color calibration or correction systems, highly suitable to be used for, or incorporated into, the color calibration or control of various color printing systems or other on-line color control; or color processing systems.
In particular, the disclosed spectrophotometer provides improved accuracy for color test surfaces which may be tilted, curved, non-planer or otherwise varying in angular orientation relative to the spectrophotometer. That is particularly desirable for enhancement of the accuracy of a non-contact spectrophotometer which can measure the colors or color densities of test surfaces spaced from the spectrophotometer, especially moving surfaces, such as printed paper sheets in the output path of a color printer, or toner or liquid ink test patches on a moving photoreceptor or other surface, or other moving color objects, webs or materials, without requiring the test surface material to be constrained against a reference surface or against the spectrophotometer.
This freedom of movement of the test material, both transversely to, and variably spaced from, the spectrophotometer, can be quite desirable in various color measurement applications, such as allowing printed sheets to move freely between relatively widely spaced apart paper path baffles or guides. However, that freedom of movement can also allow the color test surface material or media to have variances in angular alignment relative to the spectrophotometer, which may be manifested by lead and trail edge curl or buckle induced by the media handling apparatus, or otherwise. The disclosed embodiments can desirably reduce measurement and output signal errors from such variances in angular alignment. There can also be azimuthal or media rotation measurement variances from differences in media reflectivity such as paper fiber orientation.
As will be further described, the improved angular and azimuthal insensitivity of the embodiment herein is fully compatible with, and is shown herein combinable with, various of the spectrophotometer features of the above-cross-referenced copending commonly owned U.S. applications, especially the displacement insensitivity system of the; above cross-referenced copending commonly owned U.S. application Ser. No. 09/535,007, filed Mar. 23, 2000, by the same Fred F. Hubble, III and. Joel A. Kubby. Also it is optionally compatible with the multiple different photo-sites detectors of the above cross-referenced, commonly owned and contemporaneously filed Application by Jagdish C. Tandon and Lingappa K. Mestha, Attorney Docket No. D/99660 (also, described herein, as an alternative embodiment).
In the specific exemplary spectrophotometer embodiment further described below, it may be seen that plural different color emission LEDs sequentially project their respective illuminations substantially in parallel, perpendicularly to the color test target surface, rather than at an angle thereto, so as to provide a substantially circular, rather than elliptical, commonly illuminated area of the test target. That is, with all the LEDs centrally located together, their illumination pattern on the test target may be formed from rays that hit the target at approximately 90 degrees, i.e., normal to the target. This will produce a circular or nearly circular irradiance pattern on a selected area of the target when the target surface is at 90 degrees thereto. One or more photo-sensors may be optically oriented at 45 degrees to the test target to receive the reflected light from the illuminated test target. As will be further explained herein, when the test target surface deviates from said 90 degrees, by factors such as paper lead or trail edge curl, paper buckle or corrugation, sensor mounting misalignment, or other effects, this circular LED irradiance pattern becomes only slightly elliptical, with little area change, and thus causes little variance in the target irradiance and, therefore, in the signals from the photo-sensors, hence providing improved spectrophotometer angular insensitivity.
An additional feature for improved spectrophotometer accuracy in the disclosed embodiment is to provide averaging of the outputs of plural photodetectors which are angularly viewing the target irradiance area from different positions around it, on opposing sides, so as to average any varying angular and/or azimuthal reflectivity of the target area, and thus further increase the insensitivity to changes in alignment with the target area.
Although not limited thereto, the exemplary spectrophotometer of the embodiments is shown and described herein as an integral part of an automatic on-line continuous color correction system of a color printer. That is because such a low cost spectrophotometer may be affordably provided and easily mounted in the output paths of color printers for automatic measurement of automatically printed color test sheets, without any manual effort or intervention being required, and without interfering with normal printing or the normal movement of printed sheets in the output path of the printer. Such color control systems are further described in the above and below cited co-pending applications and patents. For example, in Xerox Corp. U.S. Pat. No. 6,178,007 B1, issued Jan. 23, 2001, based on U.S. application Ser. No. 08/786,010, filed Jan. 21, 1997 by Steven J. Harrington, Attorney Docket No. D/96644, entitled “Method For Continuous Incremental Color Calibration For Color Document Output Terminals.” The European patent application equivalent thereof was published by the European Patent Office on Jul. 22, 1998 as EPO publication No. 0 854 638 A2. Also, Xerox Corp. U.S. Pat. No. 6,222,648, issued Apr. 24, 2001, based on U.S. application Ser. No. 08/787,524, also filed Jan. 21, 1997, by Barry Wolf, et al, entitled “On Line Compensation for Slow Drift of Color Fidelity in Document Output Terminals (DOT),” Attorney Docket No. D/96459. Also noted are Xerox Corp. U.S. Pat. No. 6,157,469, issued Dec. 5, 2000 and filed May 22, 1998, by Lingappa K. Mestha; Apple Computer, Inc. U.S. Pat. No. 5,881,209, issued Mar. 9, 1999; U.S. Pat. No. 5,612,902, issued Mar. 18, 1997 to Michael Stokes, and other patents and applications further noted below.
A low cost, relatively simple, spectrophotometer, as disclosed herein, is thus particularly (but not exclusively) highly desirable for such a “colorimetry” function for such an on-line printer color correction system. Where at least one dedicated spectrophotometer is being provided in each printer, its cost and other factors becomes much more significant, as compared to the high cost (and other unsuitability's for on-line use) of typical laboratory spectrophotometers.
An early patent of interest as to suggesting colorimetry in the printed sheets output of a color printer is Xerox Corp. U.S. Pat. No. 5,748,221, issued May 5, 1998 to Vittorio Castelli, et al, filed Nov. 1, 1995 (D/95398). This patent is also of particular interest here for its Col. 6, lines 18 to 28 description of measuring color:
“ . . . by imaging a part of an ill
Hubble, III Fred F.
Love Tonya L.
Robbins Daniel A.
Phan James
Xerox Corporation
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