Method for color balancing a computer input scanner incorporating multiple scanning modes

• US 5,295,204 A
• Filed: 07/18/1991
• Issued: 03/15/1994
• Est. Priority Date: 07/18/1991
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Parulski, Kenneth A.
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): Johns, Andrew W.
• Application Number:
  US07/731,967
• Time in Patent Office: 971 Days
• Field of Search: 382/59, 382/61, 382/62, 382/63, 358/27, 358/29, 358/29 C, 358/42, 358/76, 358/80, 358/473, 358/479, 358/512, 358/518, 358/523, 358/527
• US Class Current: 382/167
• CPC Class Codes: H04N 1/00 Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence
• CPC Class Codes: H04N 1/6011 with simulation on a subsidiary picture reproducer H04N1/622 takes precedence; matching two or more picture reproducers H04N1/6052
• CPC Class Codes: H04N 2201/0416 Performing a pre-scan

Abstract

A scanner useful as an input device for a computer is operable in two scanning modes: a prescanning mode in which subsampled images are composed and rapidly output to the computer for substantially real-time display, and an input scanning mode in which three successive high resolution color separations are obtained and displayed on a computer screen for color balance. A fixed color image is supported on a movable, hand-manipulated stage that interactively controls the conjugate distances of the optical system so that zooming and cropping is obtained in the prescanning mode without losing focus. The input scanning mode provides color separations useful in evaluating color balance. By defining a window overlying a selected area of the displayed color image containing neutral colors, color balance correction factors are automatically obtained for scanning values within the defined area. The exposure times of each of the color separations are then modified by the correction factors in order to preserve dynamic range in the color balanced image.

Claims

1. A color balance method for use with a scanner that generates scan values from a sensor sequentially exposed to a fixed color image for a plurality of initial exposure times corresponding to a plurality of color separations, the scanner inputting the scan values to a computer for display on a screen included therewith, said color balance method comprising the steps of:

generating scan values representative of color separations by sequentially exposing the sensor to the fixed color image for respective initial exposure times;

displaying a color image on the screen from the combination of the scan values of the several color separations;

establishing a window overlaying the displayed color image in an area where color balance is to be calculated;

executing color balance calculations upon the scan values within the window in order to generate color correction factors;

generating new exposure times for one or more of the color separations based on the color correction factors; and

using the new exposure times to generate new scan values from the fixed color image by exposing the sensor to the fixed color image to create new scan values.

2. A color balance method as claimed in claim 1 wherein said step of establishing a window comprises generating a window and moving the window to an area of the displayed color image overlying a combination of colors suitable for the color balance calculations.

3. A color balance method as claimed in claim 2 wherein the combination of colors suitable for the color balance calculations is a neutral color.

4. A color balance method as claimed in claim 1 wherein said step of generating scan values comprises generating red, green, and blue scan values by sequentially exposing the sensor through corresponding red, green, and blue filters for respective red, green, and blue initial exposure times.

5. A color balance method as claimed in claim 4 wherein said step of executing color balance calculations comprises normalizing the scan values of two of the colors with respect to the scan values of the third color, wherein said color correction factors are normalization factors.

6. A color balance method as claimed in claim 5 wherein said step of generating new exposure times comprises applying the normalization factors to the initial exposure times.

7. A scanning method incorporating color balance of the scan values generated by sequentially exposing a sensor to respective colors of a fixed color image for a corresponding sequence of initial exposure times, the scan values being input to a computer for display on a screen included therewith, the fixed color image further being positioned on a stage capable of movement in relation to the sensor to situate different parts of the fixed image on the display screen, said scanning method comprising the steps of:

actuating a prescan mode in which a monochrome image is displayed on the screen of the computer;

moving the stage until a composed image is displayed on the screen of the computer;

actuating a sequential input scan mode in which color separation images of the composed image are generated by the sensor and displayed on the screen of the computer;

establishing a window overlaying an area of the displayed image in which color balance will be calculated;

executing color balance upon the scan values in the window to generate color balance correction factors;

utilizing the color balance correction factors to adjust the exposure times to produce corrected exposure times for one or more of the color separations; and

reactivating the sequential input scan mode to generate corrected color separation images from the image sensor by using the corrected exposure times to control the time periods that the sensor is exposed to the fixed color image to create new scan values.

8. A scanning method as claimed in claim 7 in which the step of establishing a window comprises generating a window in a central area of the displayed image and then moving the stage until a neutral area of the displayed image is within the window.

9. A scanning method as claimed in claim 7 in which the step of establishing a window comprises generating a window and moving the window to a neutral area of the displayed image.