Color image forming apparatus having function for correcting image density when image development system is deteriorated

• US 6,061,144 A
• Filed: 10/15/1996
• Issued: 05/09/2000
• Est. Priority Date: 10/19/1995
• Status: Expired due to Fees

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Mamizuka, Mitsuru
• Primary Examiner(s): VU, KIM Y
• Application Number:
  US08/732,598
• Time in Patent Office: 1,302 Days
• Field of Search: 358/500, 358/518-520, 358/521, 358/504, 358/1.9, 382/167, 382/274, 382/162
• US Class Current: 358/1.9
• CPC Class Codes: H04N 1/40006 Compensating for the effects of ageing, i.e. changes over time
• CPC Class Codes: H04N 1/60 Colour correction or control H04N1/54 takes precedence
• CPC Class Codes: H04N 1/6033 using test pattern analysis H04N1/6055 takes precedence

Abstract

A color copying apparatus includes a function for correcting image density when an image development system is deteriorated after a relatively long time of usage. A reference image including a number of color gray scales is stored in a memory, and is recorded on a recording medium. Each color gray scale corresponds to each of a yellow, a magenta, a cyan, and a black color for a letter image and each of a yellow, a magenta, a cyan, and a black color for a halftone image. When the image development system is deteriorated, the reference image recorded on the recording medium represents image density which is different from the reference image stored in the memory. This difference is detected by comparing the image density of two reference images, one stored in the memory and the other recorded on the recording medium. In accordance with a result of the comparison, a suitable data table of gamma data for each color element for a letter image and for each color element for a halftone image is selected from among a number of data tables of gamma data stored in the memory, so that the image density is corrected for each color element and for each image type and such that the image development system of the color copying apparatus is set again in a condition in which an image can be reproduced in a superior quality.

Claims

1. A color image forming apparatus, comprising:

original document reading means for reading an image of an original document and for generating image signals respectively representing color elements representing said image of said original document;

image signal processing means for processing said image signals output from said original document reading means and for separating said image signals into image signals for a letter image and image signals for a photo image;

image recording means for converting said image signals into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image including a plurality of color gray scales, each color gray scale including a plurality of blocks, each block having an image density stepwise different from an image density of other blocks, for each color element for said letter image and said photo image, and for pre-storing, prior to the original document reading means reading the reference image, at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density of each of said color elements between said reference image stored in said storing means and said reference image recorded on said recording medium.

2. A color image forming apparatus according to claim 1, wherein said image signal processing means includes switch means for switching a source of an image signal between said original document reading means and an external apparatus upon receiving at least one of a switch instruction from said operator through said interface means and another switch instruction from said external apparatus.

3. A color image forming apparatus according to claim 2, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

4. A color image forming apparatus according to claim 1, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

5. A color image forming apparatus comprising:

original document reading means for reading an image of an original document and for generating image signals respectively representing color elements representing said image of said original document;

image signal processing means for processing said image signals output from said original document reading means and for separating said image signals into image signals for a letter image and image signals for a photo image;

image recording means for converting said image signals into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image including a plurality of color gray scales, each color gray scale including a plurality of blocks, each block having an image density stepwise different from an image density of other blocks, for each color element for said letter image and said photo image, and for storing at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density of each of said color elements between said reference image stored in said storing means and said reference image recorded on said recording medium;

wherein said gamma selection control means determines that a value of image density includes an abnormal value upon detecting that said reference image recorded on said recording medium does not present a graded image density similar to said reference image stored in said storing means.

6. A color image forming apparatus according to claim 5, wherein said gamma selection control means generates a warning signal upon determining that a value of image density includes an abnormal value, and sends said warning signal to said interface means to provide an operator with a warning indicative of determination that the value of image density includes the abnormal value.

7. A color image forming apparatus according to claim 6, wherein said gamma selection control means selects at least one of a first condition in which said warning signal is sent to said interface means and a second condition in which said warning signal is not sent to said interface means, upon receiving a warning selection instruction from the operator through said interface means.

8. A color image forming apparatus according to claim 6, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

9. A color image forming apparatus according to claim 6, wherein said gamma selection control means determines that a value of image density includes an abnormal value upon detecting that any one of values of image density of said plurality of said blocks of said color gray scales of said reference image recorded on said recording medium exceeds a predetermined limit.

10. A color image forming apparatus according to claim 9, wherein said gamma selection control means generates a warning signal upon determining that a value of image density includes an abnormal value, and sends said warning signal to said interface means to provide an operator with a warning indicative of determination that the value of image density includes the abnormal value.

11. A color image forming apparatus according to claim 10, wherein said gamma selection control means selects at least one of a first condition in which said warning signal is sent to said interface means and a second condition in which said warning signal is not sent to said interface means, upon receiving a warning selection instruction from the operator through said interface means.

12. A color image forming apparatus according to claim 10, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

13. A color image forming apparatus according to claim 9, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

14. A color image forming apparatus according to claim 5, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

15. A color image forming apparatus according to claim 5, wherein said gamma selection control means determines that a value of image density includes an abnormal value upon detecting that any one of values of image density of said plurality of said blocks of said color gray scales of said reference image recorded on said recording medium exceeds a predetermined limit.

16. A color image forming apparatus according to claim 15, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

17. A color image forming apparatus according to claim 15, wherein said gamma selection control means generates a warning signal upon determining that a value of image density includes an abnormal value, and sends said warning signal to said interface means to provide an operator with a warning indicative of determination that the value of image density includes the abnormal value.

18. A color image forming apparatus according to claim 17, wherein said gamma selection control means selects at least one of a first condition in which warning signal is sent to said interface means and a second condition in which said warning signal is not sent to said interface means, upon receiving a warning selection instruction from the operator through said interface means.

19. A color image forming apparatus according to claim 17, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

25. A color image forming apparatus according to claim 14, wherein said gamma selection control means generates a warning signal upon determining that a value of image density includes an abnormal value, and sends said warning signal to said interface means to provide an operator with a warning indicative of determination that the value of image density includes the abnormal value.

26. A color image forming apparatus according to claim 25, wherein said gamma selection control means selects at least one of a first condition in which said warning signal is sent to said interface means and a second condition in which said warning signal is not sent to said interface means, upon receiving a warning selection instruction from the operator through said interface means.

27. A color image forming apparatus according to claim 25, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

38. A color image forming apparatus according to claim 15, wherein said gamma selection control means selects at least one of a first condition in which said warning signal is sent to said interface means and a second condition in which said warning signal is not sent to said interface means, upon receiving a warning selection instruction from the operator through said interface means.

42. A color image forming apparatus according to claim 16, wherein said gamma selection control means selects at least one of a first condition in which said warning signal is sent to said interface means and a second condition in which said warning signal is not sent to said interface means, upon receiving a warning selection instruction from the operator through said interface means.

20. A color image forming apparatus comprising:

original document reading means for reading an image of an original document and for generating image signals respectively representing color elements representing said image of said original document;

image signal processing means for processing said image signals output from said original document reading means and for separating said image signals into image signals for a letter image and image signals for a photo image;

image recording means for converting said image signals into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image including a plurality of color gray scales, each color gray scale including a plurality of blocks, each block having an image density stepwise different from an image density of other blocks, for each color element for said letter image and said photo image, and for storing at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density of each of said color elements between said reference image stored in said storing means and said reference image recorded on said recording medium;

wherein said image signal processing means includes switch means for switching a source of an image signal between said original document reading means and an external apparatus upon receiving at least one of a switch instruction from said operator through said interface means and another switch instruction from said external apparatus;

wherein said gamma selection control means determines that a value of image density includes an abnormal value upon detecting that said reference image recorded on said recording medium does not a present graded image density similar to said reference image stored in said storing means.

21. A color image forming apparatus according to claim 20, wherein said gamma selection control means generates a warning signal upon determining that a value of image density includes an abnormal value, and sends said warning signal to said interface means to provide an operator with a warning indicative of determination that the value of image density includes the abnormal value.

22. A color image forming apparatus according to claim 21, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

23. A color image forming apparatus according to claim 21, wherein said gamma selection control means selects at least one of a first condition in which said warning signal is sent to said interface means and a second condition in which said warning signal is not sent to said interface means, upon receiving a warning selection instruction from the operator through said interface means.

24. A color image forming apparatus according to claim 21, wherein said gamma selection control means determines that a value of image density includes an abnormal value upon detecting that any one of values of image density of said plurality of said blocks of said color gray scales of said reference image recorded on said recording medium exceeds a predetermined limit.

28. A color image forming apparatus according to claim 24, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

29. A color image forming apparatus according to claim 20, wherein said gamma selection control means determines that a value of image density includes an abnormal value upon detecting that any one of values of image density of said plurality of said blocks of said color gray scales of said reference image recorded on said recording medium exceeds a predetermined limit.

30. A color image forming apparatus according to claim 29, wherein said gamma selection control means generates a warning signal upon determining that a value of image density includes an abnormal value, and sends said warning signal to said interface means to provide an operator with a warning indicative of determination that the value of image density includes the abnormal value.

31. A color image forming apparatus according to claim 30, wherein said gamma selection control means selects at least one of a first condition in which said warning signal is sent to said interface means and a second condition in which said warning signal is not sent to said interface means, upon receiving a warning selection instruction from the operator through said interface means.

32. A color image forming apparatus according to claim 30, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

33. A color image forming apparatus according to claim 29, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

34. A color image forming apparatus according to claim 20, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

35. A color image forming apparatus comprising;

original document reading means for reading an image of an original document and for generating image signals respectively representing color elements representing said image of said original document;

image signal processing means for processing said image signals output from said original document reading means and for separating said image signals into image signals for a letter image and image signals for a photo image;

image recording means for converting said image signals into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image including a plurality of color gray scales, each color gray scale including a plurality of blocks, each block having an image density stepwise different from an image density of other blocks, for each color element for said letter image and said photo image, and for storing at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density of each of said color elements between said reference image stored in said storing means and said reference image recorded on said recording medium;

wherein said gamma selection control means determines that a value of image density includes an abnormal value upon detecting that any one of values of image density of said plurality of said blocks of said color gray scales of said reference image recorded on said recording medium exceeds a predetermined limit.

36. A color image forming apparatus according to claim 35, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

37. A color image forming apparatus according to claim 35, wherein said gamma selection control means generates a warning signal upon determining that a value of image density includes an abnormal value, and sends said warning signal to said interface means to provide an operator with a warning indicative of determination that the value of image density includes the abnormal value.

39. A color image forming apparatus according to claim 37, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

40. A color image forming apparatus comprising:

original document reading means for reading an image of an original document and for generating image signals respectively representing color elements representing said image of said original document;

image signal processing means for processing said image signals output from said original document reading means and for separating said image signals into image signals for a letter image and image signals for a photo image;

image recording means for converting said image signals into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image including a plurality of color gray scales, each color gray scale including a plurality of blocks, each block having an image density stepwise different from an image density of other blocks, for each color element for said letter image and said photo image, and for storing at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density of each of said color elements between said reference image stored in said storing means and said reference image recorded on said recording medium;

wherein said image signal processing means includes switch means for switching a source of an image signal between said original document reading means and an external apparatus upon receiving at least one of a switch instruction from said operator through said interface means and another switch instruction from said external apparatus;

wherein said gamma selection control means determines that a value of image density includes an abnormal value upon detecting that any one of values of image density of said plurality of said blocks of said color gray scales of said reference image recorded on said recording medium exceeds a predetermined limit.

41. A color image forming apparatus according to claim 40, wherein said gamma selection control means generates a warning signal upon determining that a value of image density includes an abnormal value, and sends said warning signal to said interface means to provide an operator with a warning indicative of determination that the value of image density includes the abnormal value.

43. A color image forming apparatus according to claim 41, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

44. A color image forming apparatus according to claim 40, wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.

45. A color image forming apparatus, comprising:

original document reading means for reading an image of an original document;

image recording means for converting said read image of the original document into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for pre-storing, prior to the original document reading means reading the image of the original document, data representing a reference image and for pre-storing, prior to the original document reading means reading the reference image, at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density between said reference image stored in said storing means and said reference image recorded on said recording medium.

46. A color image forming apparatus comprising:

original document reading means for reading an image of an original document;

image recording means for converting said read image of the original document into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image and for pre-storing, prior to the original document reading means reading the reference image, at least one data table for gamma data;

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density between said reference image stored in said storing means and said reference image recorded on said recording medium, and

switch means for switching a source of an image signal between said original document reading means and an external apparatus upon receiving at least one of a switch instruction from said operator through said interface means and another switch instruction from said external apparatus.

47. A color image forming apparatus comprising:

original document reading means for reading an image of an original document;

image recording means for converting said read image of the original document into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image and for storing at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density between said reference image stored in said storing means and said reference image recorded on said recording medium.

48. A color image forming apparatus comprising:

original document reading means for reading an image of an original document;

image recording means for converting said read image of the original document into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image and for storing at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing the gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density between said reference image stored in said storing means and said reference image recorded on said recording medium,

wherein said gamma selection control means generates a warning signal upon determining that a value of image density includes an abnormal value, and sends said warning signal to said interface means to provide an operator with a warning indicative of determination that the value of image density includes the abnormal value.

49. A color image forming apparatus comprising:

original document reading means for reading an image of an original document;

image recording means for converting said read image of the original document into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image and for storing at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data and for analyzing a difference of image density between said reference image stored in said storing means and said reference image recorded on said recording medium,

wherein said gamma selection control means selects at least one of a first condition in which a warning signal is sent to said interface means and a second condition in which said warning signal is not sent to said interface means, upon receiving a warning selection instruction from the operator through said interface means.

50. A color image forming apparatus comprising:

original document reading means for reading an image of an original document;

image recording means for converting said read image of the original document into a visual form of a color image on a recording medium;

interface means for receiving an instruction entered by an operator and for informing said operator of a state of said color image forming apparatus;

storing means for storing data representing a reference image and for pre-storing, prior to the original document reading means reading the reference image, at least one data table for gamma data; and

gamma selection control means for controlling said image recording means to record said reference image stored in said storing means on a recording medium upon receiving a recording instruction through said interface means, for controlling said original document reading means to read said reference image recorded on said recording medium, for detecting an input of a change instruction for changing said gamma data through said interface means, for changing said gamma data, and for analyzing a difference of image density between said reference image stored in said storing means and said reference image recorded on said recording medium,

wherein said storing means stores a plurality of personal identification numbers, and said gamma selection control means enables the instruction for changing the gamma data only when a personal identification number entered by an operator is verified by a personal identification number stored in said storing means.