Automatic focusing device and the electronic image pickup apparatus using the same

• US 6,972,797 B2
• Filed: 10/17/2001
• Issued: 12/06/2005
• Est. Priority Date: 10/19/2000
• Status: Expired due to Fees

• Current Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Original Assignee: Fuji Electric Company Limited (Fuji Electric Systems Company Limited)
• Inventors: Izumi, Akio
• Primary Examiner(s): Garber, Wendy R.
• Assistant Examiner(s): WHIPKEY, JASON T
• Application Number:
  US09/978,839
• Publication Number:
  US 20020080259A1
• Time in Patent Office: 1,511 Days
• Field of Search: 396/81, 396/93, 396/80, 396/105, 348/348, 348/345, 348/350, 348/354, 348/355, 348/356
• US Class Current: 348/348
• CPC Class Codes: G02B 7/34 using different areas in a pupil plane
• CPC Class Codes: G03B 13/36 Autofocus systems
• CPC Class Codes: H04N 23/671 in combination with active ranging signals, e.g. using light or sound signals emitted toward objects
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method
• CPC Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming

Abstract

An auto-focusing device and an electronic image pickup apparatus facilitates realizing a high focusing accuracy and a quick focusing operation simultaneously using an inexpensive plastic lens mount. The auto-focusing device according includes a means for correcting the conversion reference, if necessary, for converting the object distance measured by the open-control range finding means to a focusing position of the focusing lens based on the conversion reference and for moving the focusing lens to the converted focusing position. The electronic image pickup apparatus includes the auto-focusing device.

Claims

1. An automatic focusing device comprising:

an image pickup lens including a moveable focusing lens, wherein the focusing lens moves to form an image of an object at an image plane;

an image pickup means, wherein the image pickup means picks up the image of the object at the image plane and outputs an electrical signal corresponding to the image of the object;

a TTL focus detecting means, wherein the TTL focus detects means detects a focusing state of the image pickup lens based on the electrical signal output from the image pickup means;

an open-control range finding means, wherein the open-control range finding means measures the distance of the object between the automatic focusing device and the object;

a focusing lens position detecting means, wherein the focusing lens position detecting means detects at least one of a focusing position and a shift length of the focusing lens;

a driving and controlling means, wherein the driving and controlling means obtains a focusing position of the focusing lens based on a conversion reference for converting the distance of the object measured by the open-control range finding means to the focusing position of the focusing lens, whereby to move the focusing lens to the focusing position thereof;

wherein the driving and controlling means moves the focusing lens based on the focusing state of the image pickup lens detected by the TTL focus detecting means when it is necessary to correct the conversion reference;

wherein the driving and controlling means makes the focusing lens position detecting means detect the focusing position or the shift length of the focusing lens;

wherein the driving and controlling means makes the open-control range finding means measure the distance of the object; and

wherein the driving and controlling means corrects the conversion reference based on at least one of the detected focusing position and the detected shift length of the focusing lens, and the measured distance of the object.

2. The automatic focusing device according to claim 1, wherein the conversion reference is a lens focusing curve relating the inverse of the distance of the object and the position of the focusing lens, and correcting the conversion reference comprises shifting the lens focusing curve such that the lens focusing curve passes the point defined by the inverse of the distance of the object measured by the open-control range finding means and the focusing position of the focusing lens detected by the focusing lens position detecting means or selecting a lens focusing curve that passes the point defined by the inverse of the distance of the object measured by the open-control range finding means and the focusing position of the focusing lens detected by the focusing lens position detecting means, from a plurality of lens focusing curves stored in advance.

3. The automatic focusing device according to claim 1, wherein the conversion reference is a lens focusing curve relating the inverse of the distance of the object and the position of the focusing lens, and correcting the conversion reference comprises calculating a new focusing position of the focusing lens by adding the shift length of the focusing lens detected by the focusing lens position detecting means to the focusing position not corrected yet, whereby to obtain a new lens focusing curve, that passes the point defined by the inverse of the distance of the object measured by the open-control range finding means and the new focusing position of the focusing lens, or selecting a lens focusing curve, that passes the point defined by the inverse of the distance of the object measured by the open-control range finding means and the new focusing position of the focusing lens, from a plurality of lens focusing curves stored in advance.

4. The automatic focusing device according to claim 1, wherein the image pickup lens comprises zoom lens, and the conversion reference is corrected one or more times when the zooming ratio of the image pickup lens exceeds a predetermined range.

5. The automatic focusing device according to claim 1, wherein the automatic focusing device further comprises a temperature measuring means that measures the temperature of the automatic focusing device, and a temperature storage means that stores the measured temperature, and the conversion reference is corrected one or more times when the difference between the present temperature measured by the temperature measuring means and the last temperature measured during the last correction and stored in the temperature storage means exceeds a predetermined range.

6. An electronic image pickup apparatus comprising:

an image pickup lens including a moveable focusing lens, wherein the focusing lens moves to form an image of an object at an image plane;

an image pickup means, wherein the image pickup means picks up the image of the object at the image plane and outputs an image signal;

a TTL focus detecting means, wherein the TTL focus detecting means detects a focusing state of the image pickup lens based on the image signal output from the image pickup means;

a storing and reproducing means, the storing and reproducing means storing the image of the object based on the image signal outputted from the image pickup means, the storing and reproducing means reproducing the stored image of the object;

an open-control range finding means, wherein the open-control range finding means measures the distance of the object between the electronic image pickup apparatus and the object;

a focusing lens position detecting means, wherein the focusing lens position detecting means detects at least one of a focusing position and a shift length of the focusing lens;

a driving and controlling means, wherein the driving and controlling means obtains a focusing position of the focusing lens based on a conversion reference for converting the distance of the object measured by the open-control range finding means to the focusing position of the focusing lens, whereby to move the focusing lens to the focusing position thereof;

wherein the driving and controlling means moves the focusing lens based on the focusing state of the image pickup lens detected by the TTL focus detecting means when it is necessary to correct the conversion reference;

wherein the driving and controlling means makes the focusing lens position detecting means detect at least one of the focusing position and the shift length of the focusing lens;

wherein the driving and controlling means makes the open-control range finding means measure the distance of the object; and

wherein the driving and controlling means corrects the conversion reference based on the detected focusing position, thereat the image of the object is focused, or the detected shift length of the focusing lens, thereat the image of the object is focused, and the measured distance of the object.

7. The electronic image pickup apparatus according to claim 6, wherein the conversion reference is a lens focusing curve relating the inverse of the distance of the object and the position of the focusing lens, and correcting the conversion reference comprises shifting the lens focusing curve such that the lens focusing curve passes the point defined by the inverse of the distance of the object measured by the open-control range finding means and the focusing position of the focusing lens detected by the focusing lens position detecting means or selecting a lens focusing curve, that passes the point defined by the inverse of the distance of the object measured by the open-control range finding means and the focusing position of the focusing lens detected by the focusing lens position detecting means, from a plurality of lens focusing curves stored in advance.

8. The electronic image pickup apparatus according to claim 6, wherein the conversion reference is a lens focusing curve relating the inverse of the distance of the object and the position of the focusing lens, and correcting the conversion reference comprises calculating a new focusing position of the focusing lens by adding the shift length of the focusing lens detected by the focusing lens position detecting means to the focusing position not corrected yet, whereby to obtain a new lens focusing curve, that passes the point defined by the inverse of the distance of the object measured by the open-control range finding means and the new focusing position of the focusing lens, or selecting a lens focusing curve, that passes the point defined by the inverse of the distance of the object measured by the open-control range finding means and the new focusing position of the focusing lens, from a plurality of lens focusing curves stored in advance.

9. The electronic image pickup apparatus according to claim 6, wherein the image pickup lens comprises zoom lens, and the conversion reference is corrected one or more times when the zooming ratio of the image pickup lens exceeds a predetermined range.

10. The electronic image pickup apparatus according to claim 6, wherein the electronic image pickup apparatus further comprises a temperature measuring means that measures the temperature of the electronic image pickup apparatus, and a temperature storage means that stores the measured temperature, and the conversion reference is corrected one or more times when the difference between the present temperature measured by the temperature measuring means and the last temperature measured during the last correction and stored in the temperature storage means exceeds a predetermined range.

11. The electronic image pickup apparatus according to claim 6, wherein the image pickup lens is exchangeable, and the conversion reference is corrected one or more times when image pickup lens is changed to another one.

12. The electronic image pickup apparatus according to claim 6, wherein the electronic image pickup apparatus further comprises a release switch capable of conducting a first stage of switching when the release switch is pressed halfway, and a second stage of switching when the release switch is fully pressed, the conversion reference is corrected one or more times when the first stage of switching is conducted, and the focusing lens is moved to the focusing position thereof calculated from the distance of the object measured by the open-control range finding means when the second stage of switching is conducted.