Apparatus for detecting focusing status of taking lens

• US 7,030,927 B2
• Filed: 03/06/2002
• Issued: 04/18/2006
• Est. Priority Date: 03/28/2001
• Status: Active Grant

• Current Assignee: Fujinon Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujinon Corporation (Fujifilm Holdings Corporation)
• Inventors: Sasaki, Tadashi
• Primary Examiner(s): Ometz, David L.
• Assistant Examiner(s): Lam, Hung H.
• Application Number:
  US10/090,756
• Publication Number:
  US 20020140841A1
• Time in Patent Office: 1,504 Days
• Field of Search: 348/302, 348307-310, 348/311, 250/250, 250/204
• US Class Current: 348/345
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method

Abstract

The number of pixels of image pickup devices for detecting a focusing status is smaller than the number of pixels of an image pickup device for image-output, or an image pickup size of the image pickup devices for detecting the focusing status is smaller than the image pickup size of the image pickup device for image-output, so that the apparatus for detecting the focusing status that is inexpensive, consumes reduced power, and includes a circuit reduced in size is provided. Two image pickup devices for detecting the focusing status with different optical path lengths are provided with respect to an image pickup device for obtaining an image to be outputted, and subject light intended to be incident on the image pickup device is split to be incident on the image pickup devices for detecting the focusing status. Then, focusing evaluation values are obtained based on video signals from the image pickup devices for detecting the focusing status, and the focusing status is determined to be front focus, rear focus, or in focus based on the magnitudes of the focusing evaluation values. As the image pickup devices for detecting the focusing status, CCDs having less number of pixels and smaller image pickup size than the image pickup device for image-output is used.

Claims

1. A focusing status detecting apparatus which detects a focusing status of a taking lens with respect to a two-dimensional image pickup device for image-output of a camera that obtains an image to be outputted, the focusing status detecting apparatus determining that the focusing status is one of front focus, rear focus, and in focus, the focusing status detecting apparatus comprising:

a plurality of two-dimensional image pickup devices for detecting the focusing status which detect the focusing status, the plurality of image pickup devices receiving subject light incident through the taking lens with different optical path lengths, a focusing evaluation value being obtained according to a high frequency component of each of images obtained by the plurality of image pickup devices for detecting the focusing status, the focusing status being determined according to the obtained focusing evaluation value,

wherein a number of pixels of the plurality of image pickup devices for detecting the focusing status is smaller than a number of pixels of the image pickup device for image-output, and wherein of the digital signals of the images obtained by the image pickup devices for detecting focusing status only digital signals corresponding to pixels within a predetermined focus area are extracted, so that the focusing status is detected within a frame of the image smaller than the entire frame of the image to be outputted obtained by the image pickup device for image-output.

2. The focusing status detecting apparatus of claim 1 wherein said image pickup devices for detecting focusing status detect a frame.

3. The focusing status detecting apparatus of claim 2 wherein said predetermined focus area comprises a central portion of said frame.

4. A focusing status detecting apparatus which detects a focusing status of a taking lens with respect to a two-dimensional image pickup device for image-output of a camera that obtains an image to be outputted, the focusing status detecting apparatus determining that the focusing status is one of front focus, rear focus, and in focus, the focusing status detecting apparatus comprising:

a plurality of two dimensional image pickup devices for detecting the focusing status which detect the focusing status, the plurality of image pickup devices receiving subject light incident through the taking lens with different optical path lengths, a focusing evaluation value being obtained according to a high frequency component of each of images obtained by the plurality of image pickup devices for detecting the focusing status, the focusing status being determined according to the obtained focusing evaluation value,

wherein an image pickup size of the plurality of image pickup devices for detecting the focusing status is smaller than an image pickup size of the image pickup device for image-output, and wherein of the digital signals of the images obtained by the image pickup devices for detecting focusing status only digital signals corresponding to pixels within a predetermined focus area are extracted, so that the focusing status is detected within a frame of the image smaller than the entire frame of the image to be outputted obtained by the image pickup device for image-output.

5. The focusing status detecting apparatus of claim 4 wherein said image pickup devices for detecting focusing status detect a frame.

6. The focusing status detecting apparatus of claim 5 wherein said predetermined focus area comprises a central portion of said frame.

7. A focusing status detecting apparatus which detects a focusing status of a taking lens with respect to a first image pickup device for image-output of a camera that obtains an image to be outputted, the focusing status detecting apparatus adapted to determine whether the focusing status is front focus, rear focus, or in focus, the focusing status detecting apparatus comprising:

a plurality of second image pickup devices for detecting the focusing status by detecting a two-dimensional image, the plurality of second image pickup devices receiving light incident through the taking lens with different optical path lengths, a focusing evaluation value being obtained according to a high frequency component of each of images obtained by the plurality of first image pickup devices, the focusing status being determined according to the obtained focusing evaluation value,

wherein a number of pixels of the plurality of second image pickup devices is smaller than a number of pixels of the first image pickup device, and the focusing status is detected within a frame of the image smaller than the entire frame of the image to be outputted obtained by the first image pickup device.

8. The focusing status detecting apparatus of claim 7 wherein focusing status is detected using digital signals from fewer than all pixels of the plurality of second image pickup devices.

9. The focusing status detecting apparatus of claim 7 wherein focusing status is detected using digital signals from pixels in a predetermined focus area of the plurality of second image pickup devices.

10. The focusing status detecting apparatus of claim 9 wherein said predetermined focus area comprises a central area of a frame.