Autofocus apparatus

a technology of autofocus and apparatus, which is applied in the field of autofocus apparatus and camera, can solve the problems of reducing the s/n ratio of picture signal, the crest of this level has a tendency to become steeper with a higher frequency, and the image forming performance of the lens and the s/n ratio of the picture signal worsen, so as to prevent the decline in focusing accuracy, high precision, and effect of quick focusing

Inactive Publication Date: 2007-10-11
NIKON CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0033] It is a primary object of the present invention, which was contrived under such circumstances, to provide an autofocus apparatus, a camera and a lens barrel that are inexpensive and capable of focusing quickly with a high accuracy.
[0034] It is another object of the present invention to provide a lens barrel capable of actualizing an autofocus function even when attached to a camera body incorporating no autofocus function.
[0035] It is a further object of the present invention to provide an autofocus apparatus capable of focusing on a photographing target at a high efficiency.

Problems solved by technology

Further, a crest of this level has a tendency of becoming steeper with a higher frequency.
While on the other hand, an image forming performance of the lens and an S / N ratio of the picture signal worsen as the frequency gets higher.
Further, a crest of this level has a tendency of becoming steeper with a higher frequency.
While on the other hand, an image forming performance of the lens and an S / N ratio of the picture signal worsen as the frequency gets higher.
This might lead to a problem, in which it takes much time to attain the focusing.
Consequently, the focusing estimated value creating device 93 becomes harder to make the estimation.
The problem of requiring a good deal of time for focusing might bring about a possibility in which the photographer would miss an instantaneous photographing chance on the occasion of reporting news and so forth when, e.g., the above crest climbing type autofocus apparatus is used for the TV camera.
Hence, this leads to a problem of being incapable of focusing with a high accuracy.
Meeting this accuracy in the above image deviation type autofocus apparatus must involve a remarkable increase in costs.
Therefore, the problem is that the focusing might need much time.
Consequently, the time needed till the focusing is attained might extremely elongate in some cases.
The problem of requiring a good deal of time till the focusing is done might further conduce to the possibility, wherein the photographer would miss the instantaneous photographing chance on the occasion of reporting news when, e.g., the above-described crest climbing type autofocus apparatus is used for the TV camera.
Particularly the camera body of the TV camera employed by a professional cameraman is, however, very expensive and therefore causes such a problem that the user is forced to expend much in order to actualize the autofocus function in that TV camera.
Upon carrying out the tracking adjustment, there must be produced a deviation in an optical positional relationship between the imaging element surface of the video camera body and the predetermined focal surface 97 for estimating the focusing, resulting in a decline in terms of the focusing accuracy.

Method used

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Experimental program
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first embodiment

[0157] Moreover, in the present invention, a focal length of the optical system for forming images for detecting the image deviation on the line sensors 34a, 34b in the second focusing estimating part 3, is a synthetic focal length of the focus adjusting lens 11, the variable magnification lens 12, the correcting lens 13 and the image forming lens 32. On the other hand, a focal length of the optical system for forming an image for the picture signal on the imaging element 21, is a synthetic focal length of the focus adjusting lens 11, the variable magnification lens 12, the correcting lens 13 and the image forming lens 14. Therefore, the focal lengths of the optical system for forming the images for detecting the image deviation and of the optical system for forming the image for the picture signal, are varied by changing configurations of the image forming lenses 14 and 32, videlicet, the sizes of the images formed respectively by the individual optical systems can be changed. For ...

second embodiment

[0162] Next, the present invention will be described with reference to the drawings.

[0163]FIG. 12 is a schematic block diagram illustrating the autofocus apparatus in the second embodiment of the present invention. Note that the elements having the same functions as those in the first embodiment shown in FIG. 10 are marked with the like or corresponding numerals in the second embodiment of the present invention, and the detailed explanations thereof are omitted.

[0164] A different point of the autofocus apparatus in the second embodiment shown in FIG. 12 from the first embodiment shown in FIG. 10, is that a focusing method selecting device 4a is employed in place of the focusing method selecting device 4, and that an aperture value detecting device 80 for detecting an aperture value of the stop 16 of the photographing optical system 1. Other configurations are basically the same as those in the first embodiment.

[0165] A difference of the focusing method selecting device 4a from the...

third embodiment

[0170] Next, the present invention will be discussed with reference to the drawings.

[0171]FIG. 15 is a schematic block diagram illustrating the autofocus apparatus in the third embodiment of the present invention. FIG. 16 is an explanatory diagram showing a relationship between a focal length of the photographing optical system, a distance from the photographing optical system to the object, a dimension of the object on the imaging element, and a real dimension of the object. FIG. 17 is a diagram showing one example of an object dimension setting device used in the third embodiment. Note that the elements having the same functions as those in the first embodiment shown in FIG. 10 are marked with the like or corresponding numerals in the third embodiment of the present invention, and the detailed explanations thereof are omitted.

[0172] A different point of the autofocus apparatus in the third embodiment illustrated in FIG. 15 from the first embodiment shown in FIG. 10, is that there...

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PUM

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Abstract

An autofocus apparatus with a photographic optical system having a movably disposed focus adjusting lens, an optical element to split light beams received from an object, a plurality of image forming lenses to form images from portions of the split light beams, a plurality of focusing estimating portions to create focusing data for focusing the image of the object on the corresponding image forming lenses, a data detecting device to detect data for focusing the image, a data creating device to correct the detected focusing data, a selecting portion to select from among the focusing estimating portions, and a moving device to move the focus adjusting lens.

Description

[0001] This application is a continuation of divisional U.S. application Ser. No. 09 / 550,640, filed Apr. 14, 2000, and now allowed, which further claims the benefit of priority of U.S. application Ser. No. 08 / 834,926, filed Apr. 7, 1997, now abandoned, and Japanese Patent Application Nos. 8-85192, 8-85193, 8-116742, 8-116743, 8-154086 and 8-154087, the contents of all of the foregoing being incorporated herein by reference in their entirety.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an autofocus apparatus and a camera that are used for a camera, mainly for a video camera and particularly for a TV camera. The present invention also relates to a lens barrel and a camera that are used chiefly for a lens interchangeable type video camera and particularly for a lens interchangeable type TV camera. [0004] 2. Related Background Art [0005] There have hitherto been two kinds of autofocus apparatuses as an autofocus apparatus for a cam...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): H04N5/232G02B7/09
CPCG03B13/36H04N5/23212H04N5/23209H04N23/663H04N23/673
InventorKUROKAWA, HIROYUKINOZAKI, HIROTAKEMURAKAMI, KOUTAROU
OwnerNIKON CORP