Focus detection apparatus capable of detecting an in-focus position in a wide field of view by utilizing an image contrast technique

A focus detection apparatus comprising:

• a charge storage type photoelectric conversion element for receiving an object light beam and photoelectrically converting the object light beam;
• defocusing-amount changing means for changing a defocus amount of the object light beam received by said photoelectric conversion element;
• contrast signal peak value detection means for detecting a contrast signal corresponding to a reference detection frequency based on an output signal, corresponding to a set distance measurement area, of outputs from said photoelectric conversion element while said defocusing-amount changing means changes the defocus amount of the object light beam, and for detecting a defocusing position where the contrast signal exhibits a peak value;
• storage means for prestoring a deviation amount between the defocusing position with respect to the reference detection frequency and a defocusing position where a contrast signal of another detection frequency exhibits a peak value;
• and
• prediction means for correcting the defocusing position where the contract signal exhibits the peak value at the reference detection frequency using the deviation amount of the peak value stored in said storage means, thereby predicting an in-focus position.

A focus detection apparatus comprising:

• a charge storage type photoelectric conversion element for receiving an object light beam and photoelectrically converting the object light beam;
• defocusing-amount changing means for changing a defocus amount of the object light beam received by said photoelectric conversion element;
• contrast signal peak value detection means for detecting a contrast signal corresponding to a specific detection frequency based on an output signal, corresponding to a set distance measurement area, of outputs from said photoelectric conversion element while said defocusing-amount changing means changes a defocus amount of the object light beam, and for detecting a defocusing position where a peak value of the contrast signal is obtained, thereby determining a first in-focus position based on said defocusing position where said peak value is obtained;
• storage means for prestoring a deviation amount between the defocusing position with respect to the specific detection frequency and a defocusing position where a contrast signal of another detection frequency exhibits a peak value;
• prediction means for correcting the defocusing position where the contrast signal exhibits the peak value at the specific detection frequency using the deviation amount stored in said storage means, thereby predicting a second in-focus position;
• and
• calculation means for calculating based on said first in-focus position and the second in-focus position an aperture value with which said first and second in-focus positions fall within a depth of field.

A focus detection apparatus comprising:

• focus detection area setting means for selecting and setting one distance measurement area to be subjected to focus detection from a plurality of distance measurement areas in a photographing area;
• a photoelectric conversion element, arranged in correspondence with the plurality of distance measurement areas, for receiving an object light beam, and photoelectrically converting the object light beam;
• contrast signal peak value detection means for detecting a peak value of a contrast signal corresponding to a first detection frequency on the basis of an output from said photoelectric conversion element;
• peak position prediction means for predicting a peak position of a contrast signal corresponding to a second detection frequency in accordance with the detected peak value;
• in-focus point detection means for detecting a peak value of the contrast signal corresponding to the second detection frequency near the predicted peak position on the basis of the output from said photoelectric conversion element, and obtaining an in-focus point;
• and
• MTF characteristic value storage means for storing MTF characteristic values, each representing a difference between the peak positions of the contrast signals corresponding to the first and second detection frequencies, in correspondence with the plurality of distance measurement areas,
• wherein said peak position prediction means obtains the predicted peak position on the basis of a stored value corresponding to the distance measurement area stored in said MTF characteristic value storage means, and the output from said contrast signal peak value detection means.

A focus detection apparatus for obtaining an in-focus point on the basis of contrast data of an object corresponding to a plurality of detection frequencies, comprising:

• a plurality of photoelectric conversion elements, arranged in correspondence with a plurality of distance measurement areas in a photographing area, for photo-electrically converting an object light beam passing through a photographing lens;
• storage means for storing MTF characteristic values each representing a difference between a peak position of a contrast signal corresponding to a reference detection frequency, and a peak position of a contrast signal corresponding to another detection frequency, in correspondence with the plurality of distance measurement areas;
• selection means for selecting one of the plurality of distance measurement areas in the photographing area;
• readout means for reading out the MTF characteristic value corresponding to the distance measurement area selected by said selection means from said storage means;
• a relay lens arranged in an optical path between said photographing lens and said photoelectric conversion elements;
• relay lens driving means for driving said relay lens;
• peak value detection means for detecting a peak value of the contrast signal corresponding to the reference detection frequency on the basis of an output from the photoelectric conversion element corresponding to the selected distance measurement area upon driving of the driven relay lens;
• and
• means for limiting a driving area, which is used to detect a peak value of the contrast signal corresponding to another detection frequency, of said relay lens driving means on the basis of a detection result of said detection means, and the readout MTF characteristic value.

A focusing method of obtaining an in-focus point based on contrast data of an object in a distance measurement area which is selected from a plurality of distance measurement areas in a photographing area, and driving a photographing lens, comprising the steps of:

• (a) setting the selected distance measurement area;
• (b) reading out an MTF characteristic value corresponding to the selected distance measurement area stored in storage means;
• (c) obtaining a contrast peak value of a first detection frequency component, and detecting a position of a first peak value;
• (d) predicting an existing area of a contrast peak value of a second detection frequency component higher than the first detection frequency component on the basis of the readout MTF characteristic value and the detected position of the first peak value;
• (e) obtaining a contrast peak value of the second detection frequency component in accordance with the predicted existing area of the peak value, and detecting a second peak value;
• and
• (f) driving said photographing lens in accordance with the positions of the first and second peak values.

A focus detection apparatus comprising:

• an area type charge storage type photoelectric conversion element for receiving an object light beam and photoelectrically converting the object light beam;
• contrast signal peak value detection means for detecting a contrast signal corresponding to a specific detection frequency based on a signal output by said photoelectric conversion element, and detecting a defocus position where the contrast signal has a peak value;
• storage means for storing a deviation amount between a peak value of a contrast signal of a detection frequency and the peak value of the contrast signal of the specific detection frequency;
• and
• prediction means for correcting the peak value of the contrast signal detected at the specific detection frequency in accordance with the deviation amount stored in said storage means, thereby to predict an in-focus position.