Angular, azimuthal and displacement insensitive spectrophotometer for color printer color control systems

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. An improved and lower cost color spectrophotometer, especially suitable for an on-line color printer color control system, in which plural different spectra LEDs sequentially perpendicularly illuminate a common and substantially circularly illuminated color test area, which may be variably spaced and variably oriented relative to the spectrophotometer, through a common central lens system, and also the reflected illumination therefrom may be measured at 45 degrees thereto by averaging the outputs of photodetectors spaced around that circularly illuminated color test area, to provide reduced sensitivity to the variable angular or azimuthal orientation of the color test area relative to the spectrophotometer, and which photodetectors may be so illuminated by 1:1 optics for spatial insensitivity.