Claims
- 1. An image magnification control device for a camera having a photographic lens, comprising:
- distance detecting means for detecting a distance "X0" between a rear focal point of said photographic lens and an image taking plane of said camera;
- defocus detecting means for detecting a defocusing amount "dx" corresponding to a distance between said image taking plane and a surface on which an image is formed by said photographic lens;
- first calculating means for calculating a magnification ratio .gamma. of a control focal length "f1" required to maintain an image magnification to a present focal length "f0", based on said distance "X0" and said defocus amount "dx" in accordance with an equation: ##EQU6## second calculating means for calculating a driving amount of said photographic lens to maintain said image magnification, based on said magnification ratio .gamma.; and
- means for driving said photographic lens, based on said driving amount calculated by said second calculating means, to change a focal length of said photographic lens.
- 2. The device of claim 1, wherein said distance detecting means detects said distance "X0" based on a focus position and a zoom position of said photographic lens.
- 3. The device of claim 1, wherein said second calculating means calculates said driving amount based on said magnification ratio ".gamma." using coefficients that change according to a zoom position of said photographic lens.
- 4. The device of claim 1, wherein said driving means stops driving said photographic lens when said photographic lens reaches one of a tele terminus and a wide terminus.
- 5. An image magnification control device for a camera having a photographic lens, comprising:
- a distance detector that detects a distance "X0" between a rear focal point of said photographic lens and an image taking plane of said camera;
- a defocus detector that detects a defocusing amount "dx" corresponding to a distance between said image taking plane and a surface on which an image is formed by said photographic lens;
- an image magnification calculating system that calculates a magnification ratio .gamma. of a control focal length "f1" required to maintain an image magnification, to a present focal length "f0", based on said distance "X0" and said defocus amount "dx" in accordance with an equation: ##EQU7## a driving amount calculator that calculates a driving amount of said photographic lens to maintain said image magnification, based on said magnification ratio .gamma.; and
- a lens driver that drives said photographic lens, based on said driving amount calculated by said driving amount calculator, to change a focal length of said photographic lens.
- 6. The device of claim 5, wherein said driving amount calculator calculates said driving amount based on said magnification ratio ".gamma." using coefficients that change according to a zoom position of said photographic lens.
- 7. The device of claim 5, wherein said lens driver stops driving said photographic lens when said photographic lens reaches one of a tele terminus and a wide terminus.
- 8. The device of claim 5, wherein said driving amount calculator calculates said driving amount based upon said magnification ratio ".gamma.", according to an equation:
- A.gamma..sup.3 +B.gamma..sup.2 +C.gamma.,
- wherein
- A, B and C represent coefficients that change according to a zoom position of said photographic lens.
- 9. The device of claim 5, wherein said distance detector detects said distance "X0" based on a focus position and a zoom position of said photographic lens.
- 10. A method for controlling an image magnification of a camera having a photographic lens, comprising the steps of:
- detecting a distance "X0" between a rear focal point of the lens and an image taking plane of the camera;
- detecting a defocusing amount "dx" corresponding to a distance between the image taking plane and a surface on which an image is formed by the lens;
- calculating a magnification ratio .gamma. of a control focal length "f1" required to maintain an image magnification, to a present focal length "f0", based on the detected distance "X0" and the detected defocus amount "dx" in accordance with an equation: ##EQU8## calculating an amount to drive the lens to maintain the image magnification, based on the magnification ratio .gamma.; and
- driving the lens, based on the calculated drive amount, to change a focal length of the lens.
- 11. The method of claim 10, wherein the distance detecting step comprises the step of detecting the distance "X0" based on a focus position and a zoom position of the lens.
- 12. The method of claim 10, wherein the drive amount calculating step comprises the step of calculating the driving amount based on the magnification ratio ".gamma." using coefficients that change according to a zoom position of the lens.
- 13. The method of claim 10, further comprising the step of stopping the driving of the lens when the lens reaches one of a tele terminus and a wide terminus.
- 14. The method of claim 10, wherein the drive amount calculating step comprises the step of calculating the driving amount based upon the magnification ratio ".gamma.", according to an equation:
- A.gamma..sup.3 +B.gamma..sup.2 +C.gamma.,
- wherein
- A, B and C represent coefficients that change according to a zoom position of the lens.
Priority Claims (6)
Number |
Date |
Country |
Kind |
63-237570 |
Sep 1988 |
JPX |
|
63-237571 |
Sep 1988 |
JPX |
|
63-237572 |
Sep 1988 |
JPX |
|
63-237573 |
Sep 1988 |
JPX |
|
63-237574 |
Sep 1988 |
JPX |
|
63-237575 |
Sep 1988 |
JPX |
|
Parent Case Info
This application is a division of application Ser. No. 08/373,369, filed Jan. 17, 1995, now U.S. Pat. No. 5,541,702, which is a division of application Ser. No. 08/149,226, filed Nov. 2, 1993, which issued as U.S. Pat. No. 5,428,419 on Jun. 27, 1995, which is a continuation of application Ser. No. 07/881,785, filed May 11, 1992, which issued as U.S. Pat. No. 5,283,607 on Feb. 1, 1994, which is a continuation of application Ser. No. 07/652,038, filed Feb. 4, 1991, which issued as U.S. Pat. No. 5,159,377 on Oct. 27, 1992, which is a continuation of application Ser. No. 07/410,880, filed Sep. 22, 1989, which issued as U.S. Pat. No. 5,093,680 on Mar. 3, 1992.
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Divisions (2)
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Number |
Date |
Country |
Parent |
373369 |
Jan 1995 |
|
Parent |
149226 |
Nov 1993 |
|
Continuations (3)
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Number |
Date |
Country |
Parent |
881785 |
May 1992 |
|
Parent |
652038 |
Feb 1991 |
|
Parent |
410880 |
Sep 1989 |
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