Image data processing method and apparatus therefor

• US 4,807,045 A
• Filed: 07/17/1987
• Issued: 02/21/1989
• Est. Priority Date: 07/18/1986
• Status: Expired due to Term

• Current Assignee: SCREEN Holdings Co., Ltd.
• Original Assignee: SCREEN Holdings Co., Ltd.
• Inventors: Shimano, Noriyuki
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US07/075,835
• Time in Patent Office: 585 Days
• Field of Search: 358/284, 358/282, 358/283, 358/280
• US Class Current: 358/461
• CPC Class Codes: H04N 1/401 Compensating positionally unequal response of the pick-up or reproducing head H04N1/403 takes precedence
• CPC Class Codes: H04N 1/4076 dependent on references outside the picture

Abstract

A white reference density plate and a black reference density plate are provided in the vicinity of an original. A linear image sensor reads respective optical density of the white reference density plate and of the black reference density plate, whereby reference level data are fetched in an image data processing apparatus. The reference level data are subtracted from image data of the original for eliminating background components from the image data, so that new image data are obtained.

Claims

1. An image data processing method for processing first image data obtained by optically reading the image of an original having gradation thereby to obtain second image data correctly reflecting said gradation of said original, said image data processing method comprising the steps of:

(a) preparing a reference density plane having a known optical density;

(b) reading the optical density of said reference density plane with a photoelectric converter while detecting an output level of said photoelectric converter to obtain a reference level data expressing said output level;

(c) reading said image of said original by said photoelectric converter thereby to obtain the first image data; and

(d) removing a background component from said first image data on the basis of said reference level data, thereby to obtain the second image data, said background component being outputted from said photoelectric converter independently of said image of said original including the step of obtaining a difference between said first image data and said reference level data whereby said background components included in both of said first image data and said reference level data cancel each other;

wherein said reference density plane includes a white reference density plane and a black reference density plane respectively having known optical density,

said reference level data include white reference level data and black reference level data,

step (b) includes the steps of;

(b-1) reading the optical density of said white reference density plane by said photoelectric converter to obtain said white reference level data; and

(b-2) reading the optical density of said black density reference plane by said photoelectric converter to obtain said black reference level data, and

step (d) includes the steps of;

(d-1) obtaining a first difference between said first image data and said black reference level data;

(d-2) obtaining a second difference between said white reference level data and said black reference level data; and

(d-3) dividing said first difference by said second difference.

2. An image data processing method in accordance with claim 1, wherein

said background component is removed from said first image data through a shading correction of said first image.

3. An image data processing method in accordance with claim 2, wherein

said first image data are converted into data having positive/negative sign in said shading correction.

4. An image data processing apparatus for processing first image data obtained by optically reading the image of an original having gradation thereby to obtain second image data correctly reflecting said gradation of said original, said image data processing apparatus comprising:

(a) a reference density plane having a known optical density;

(b) photoelectric conversion means for reading said optical density of said reference density plane and said image of said original;

(c) memory means for storing reference level data obtained by reading said optical density of said reference density plane by said photoelectric conversion means;

(d) shading correction means for receiving the first image data obtained by reading said image of said original by said photoelectric conversion means for performing shading correction on said first image data, said shading correction means having;

(d-1) read means for reading said reference level data from said memory means; and

(d-2) arithmetic means for obtaining a difference between said first image data and said reference level data to output a signal responsive to said difference; and

(e) means for generating the second image data on the basis of the output signal from said shading correction means

said reference density plane includes a white reference density plane and a black reference density plane respectively having known optical density,

said reference level data include white reference level data and black reference level data,

said arithmetic means includes;

first subtraction means for obtaining a first difference between said black reference level data and said first image data,

second subtraction means for obtaining a second difference between said white reference level data and said black reference level data;

dividing means for dividing said first difference by said second difference to provide a difference ratio signal, and

means for generating said second image data in response to said difference ratio signal.

5. An image data processing aparatus in accordance with claim 4, wherein

said first image data are converted into data having positive/negative sign in said shading correction means.

6. An image data processing apparatus for processing first image data obtained by optically reading the image of an original having gradation thereby to obtain second image data correctly reflecting said gradation of said original, said image data processing apparatus comprising:

(a) photoelectric conversion means for reading said image of said original;

(b) memory means for previously storing the value of a background parameter expressing the intensity of a background component outputted from said photoelectric conversion means, where said background component corresponds to the intensity of a background light indirectly coming from said original to said photoelectric conversion means, and said background parameter is previously obtained by reading reference density planes having finite optical densities to obtain reference level data and then transforming said reference level data through a transformation function which expresses said background parameter with the value of said reference level data and respective known values of said finite optical densities; and

(c) background correction means for performing background correction on the first image data obtained by reading said image of said original by said photoelectric conversion means in response to said value of said background parameter read from said memory means thereby to obtain the second image data.

7. An image data processing apparatus in accordance with claim 6 wherein

said background correction means also serves as gradation correction means for performing a gradation correction on said first image data, said background correction means having:

(c-1) storage means for storing first gradation correction data previously prepared for a case of an absence of said background component,

(c-2) arithmetic means for obtaining second gradation correction data for a case of a presence of said background component on the basis of said first gradation correction data read from said strage means and said value of said background parameter read from said memory means; and

(c-3) a look-up table memory for storing said second gradation correction data for performing said background correction and said gradation correction on said first image data.

8. An image data processing method for processing first image data obtained by optically reading the image of an original having gradation thereby to obtain second image data correctly reflecting said gradation of said original, said image data processing method comprising the steps of:

(a) preparing reference density planes having known finite optical densities, respectively;

(b) reading the optical densities of said reference density planes with a photoelectric converter while detecting an output level of said photoelectric converter to obtain reference level data expressing said output level for said reference density planes;

(c) obtaining a value of a background parameter expressing the intensity of a background component by transforming said reference level data through a predetermined transformation function, said background component corresponding to background light indirectly coming from said original to said photoelectric converter;

(d) modifying a previously given image correction curve by an amount in accordance with said value of said background parameter to obtain a modified image correction curve;

(e) reading said image of said original by said photoelectric converter thereby to obtain the first image data; and

(f) correcting said first image data through said modified image correction curve, thereby to obtain the second image data in which said background component is removed.

9. An image data procesing method in accordance with claim 8, wherein

said image correction curve is a gradation correction curve, and

said image data correcting includes gradation correcting.

10. An image data processing method in accordance with claim 9, wherein

said value of said background parameter is employed in common for each original.

11. An image data processing method in accodance with claim 9, wherein

said value of said background parameter is independently obtained for each original.