Image processing system having automatic focusing device

• US 5,508,825 A
• Filed: 12/06/1993
• Issued: 04/16/1996
• Est. Priority Date: 03/15/1990
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Kataoka, Tatsuhito
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): Stoll, Thomas L.
• Application Number:
  US08/161,445
• Time in Patent Office: 862 Days
• Field of Search: 358/471, 358/474, 358/489, 358/406, 355/53, 348/345, 348/354, 354/402, 354/407, 354/408, 354/406, 250/208.1
• US Class Current: 358/474
• CPC Class Codes: G02B 7/28 Systems for automatic generation of focusing signals
• CPC Class Codes: H04N 1/00795 Reading arrangements details of scanning heads H04N1/024; scanning arrangements therefor H04N1/04
• CPC Class Codes: H04N 1/02409 Focusing, i.e. adjusting the focus of the scanning head
• CPC Class Codes: H04N 1/193 using electrically scanned linear arrays , e.g. linear CCD arrays
• CPC Class Codes: H04N 2201/0404 Scanning transparent media, e.g. photographic film
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method

Abstract

An image processing device for processing an image formed by a lens on a sensor through an automatic focusing device is arranged to move the lens, in cases where no adequate image is formable on the sensor, to a position determined on the basis of a plurality of lens positions previously obtained with the image formed under the control of the automatic focusing device.

Claims

1. An image processing system having an automatic focusing device and arranged to process an optical image of an original formed through an image forming optical system, comprising:

a) a detecting circuit arranged to detect a state of focusing on an instant original;

b) a determining circuit arranged to determine whether or not the state of focusing is detectable by said detecting circuit; and

c) a control circuit arranged to operate either

(i) in a first mode in which, when the state of focusing is determined by said determining circuit to be detectable, said control circuit causes said image forming optical system to be set in an in-focus position by driving said optical system to a position corresponding to the result of a detection made by said detecting circuit, or

(ii) in a second mode in which, when the state of focusing is determined by said determining circuit to be undetectable, said control circuit computes a focal position for said optical system on the basis of in-focus position data set during previous image processing actions performed on preceding originals, and causes said optical system to be set in the computed focal position.

2. A system according to claim 1, wherein said detecting circuit includes a sensor part arranged to receive the optical image of the object and a processing part arranged to find the state of focusing according to an output of said sensor part, and wherein said determining circuit is arranged to determine the state of focusing to be undetectable on the basis of the output of said sensor part when said output fails to show an output state required for detection of the state of focusing.

3. A system according to claim 1, wherein said control circuit is arranged to determine said focal position, in said second mode, on the basis of a plurality of positions of said image forming optical system previously set by previous processing actions.

4. A system according to claim 3, wherein said control circuit is arranged to determine said focal position at an average point of said plurality of set positions.

5. A system according to claim 1, wherein said detecting circuit detects a state of focusing for each of a plurality of predetermined detecting areas of said object by renewing the detecting area from one area to another, wherein said determining circuit is arranged to determine whether the state of focusing is detectable or undetectable for each of said detecting areas, and wherein said control circuit operates, for every detecting area, in said second mode if the state of focusing is determined to be totally undetectable.

6. An image reading system for reading an image of each of a plurality of light-transmission originals by forming the image through an image forming lens on a sensor, comprising:

a) a focus adjusting device arranged to adjust the focus of said image forming lens every time an image reading action is performed on each of said originals, said focus adjusting device comprising;

1) a detecting circuit arranged to detect an imaged state of an instant image, corresponding to an instant original, formed on said sensor by said image forming lens;

2) a determining circuit arranged to determine whether said imaged state is detectable or undetectable by said detecting circuit; and

3) a control circuit arranged to operate either

(i) in a first mode in which said control circuit causes said image forming lens to be moved to a position corresponding to the result of detection made by said detecting circuit, when said imaged state is determined by said determining circuit to be detectable, or

(ii) in a second mode in which, when said imaged state is determined by said determining circuit to be undetectable, said control circuit computes a focal position based on focusing position data of said lens for previously-read originals, and causes said lens to be moved to the computed focal position.

7. A system according to claim 6, wherein said detecting circuit is arranged to detect an imaged state of each of predetermined parts of the original one after another, and wherein, when said imaged state of any of said predetermined parts is determined by said determining circuit to be undetectable, said lens is moved to the position obtained by said control circuit in said second mode thereof.

8. A system according to claim 6, wherein said detecting circuit is arranged to detect the imaged state of the image by moving said image forming lens, and wherein said control circuit is arranged to cause, in said first mode thereof, said lens to be moved to a position where an optimum imaged state is detected by said detecting circuit.

9. An image reading system for reading an image of each of a plurality of light-transmission originals by forming the image through an image forming lens on a sensor, comprising:

a) a focus adjusting device arranged to adjust the focus of said image forming lens every time an image reading action is performed on each of said originals, said focus adjusting device comprising;

1) a detecting circuit arranged to detect an imaged state of an instant image, corresponding to an instant original, on the basis of an output of said sensor while moving said image forming lens;

2) a determining circuit arranged to determine whether said imaged state is detectable or undetectable by said detecting circuit; and

3) a control circuit arranged to operate either

(i) in a first mode in which said control circuit causes said image forming lens to be set in a position where an optimum imaged state is detected by said detecting circuit, when said imaged state is determined by said determining circuit to be detectable, or

(ii) in a second mode in which, when said imaged state is determined by said determining circuit to be undetectable, said control circuit computes a lens position on the basis of lens position data previously set by focusing actions performed for previously-read originals, and causes said lens to be moved to the computed position.

10. A system according to claim 9, wherein said control circuit is arranged, in said second mode, to cause said detecting circuit to perform a detecting action on the imaged state of the image by further moving said lens within a predetermined range, after said lens is set in said lens position determined on the basis of said previous lens positions, and to cause said lens to be set in a lens position where an optimum imaged state is detected by said detecting circuit.

11. A system according to claim 9, wherein said detecting circuit is arranged to detect the degree of sharpness of the image on the basis of the output of said sensor part, and wherein said determining circuit is arranged to determine said imaged state to be undetectable when said degree of sharpness is less than a given value.

12. An image reading system for reading an image of each of a plurality of light-transmission originals by forming the image through an image forming lens on a sensor part, comprising:

a) a focus adjusting device arranged to adjust the focus of said image forming lens every time an image reading action is performed on each of said originals, said focus adjusting device comprising;

1) a detecting circuit arranged to detect an imaged state of an instant image, corresponding to an instant original, formed on said sensor by said image forming lens;

2) a determining circuit arranged to determine whether said imaged state is detectable or undetectable by said detecting circuit; and

3) a control circuit arranged to operate either

(i) in a first mode in which said control circuit causes said image forming lens to be moved to a position corresponding to the result of detection made by said detecting circuit, when said imaged state is determined by said determining circuit to be detectable, or

(ii) in a second mode in which, when said imaged state is determined by said determining circuit to be undetectable, said control circuit computes a focal position based on data concerning previously-read originals, and causes said lens to be moved to the computed focal position.

13. An automatic focusing device comprising:

a) a detecting circuit arranged to detect a state of focusing on an instant original;

b) a determining circuit arranged to determine whether or not the state of focusing is detectable by said detecting circuit; and

c) a control circuit arranged to operate either

(i) in a first mode in which, when the state of focusing is determined by said determining circuit to be detectable, said control circuit causes said image forming optical system to be driven to a position corresponding to the result of detection made by said detecting circuit, or

(ii) in a second mode in which, when the state of focusing is determined by said determining circuit to be undetectable, said control circuit causes said image forming optical system to be driven to a position computed on the basis of the results of a plurality of automatic focusing actions conducted on previous originals.

14. An image reading system for reading an image of each of a plurality of light-transmission originals by forming the image through an image forming lens on a sensor, comprising:

a) a focus adjusting device arranged to adjust the focus of the image through said image forming lens every time an image reading action is performed on each of said originals, said focus adjusting device comprising;

1) a detecting circuit arranged to detect an imaged state of an instant image, corresponding to an instant original, formed on said sensor;

2) a determining circuit arranged to determine whether said imaged state is detectable or undetectable by said detecting circuit; and

3) a control circuit arranged to operate either

(i) in a first mode in which said control circuit performs a focus adjusting operation based on the result of detection made by said detecting circuit, when said imaged state is determined by said determining circuit to be detectable, or

(ii) in a second mode in which, when said imaged state is determined by said determining circuit to be undetectable, said control circuit performs a focus adjusting operation in accordance with a computed focal position, the computed focal position being computed based on the results of focus adjustments for previously-read originals.