U.S. patent application number 14/395083 was filed with the patent office on 2015-05-14 for focus detection device, focus adjustment device and camera.
This patent application is currently assigned to NIKON CORPORATION. The applicant listed for this patent is NIKON CORPORATION. Invention is credited to Naoyuki Ohnishi.
Application Number | 20150130986 14/395083 |
Document ID | / |
Family ID | 49483248 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150130986 |
Kind Code |
A1 |
Ohnishi; Naoyuki |
May 14, 2015 |
FOCUS DETECTION DEVICE, FOCUS ADJUSTMENT DEVICE AND CAMERA
Abstract
A focus detection device includes: a plurality of micro-lenses
at which light fluxes through an image forming optical system
enter, disposed in a two-dimensional array pattern; a plurality of
light receiving elements disposed in correspondence to each of the
plurality of micro-lenses; a focus detection unit that executes a
detection of a defocus quantity of the image forming optical system
by detecting, based upon outputs from the plurality of light
receiving elements, a phase difference of a plurality of light
fluxes through different areas of the image forming optical system;
and a recognition unit that recognizes, based upon the outputs from
the plurality of light receiving elements, characteristics of a
subject image formed onto the plurality of light receiving elements
via the plurality of micro-lenses, wherein: the focus detection
unit detects the defocus quantity through a method optimal for the
characteristics of the subject image recognized by the recognition
unit.
Inventors: |
Ohnishi; Naoyuki; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NIKON CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
NIKON CORPORATION
Tokyo
JP
|
Family ID: |
49483248 |
Appl. No.: |
14/395083 |
Filed: |
April 25, 2013 |
PCT Filed: |
April 25, 2013 |
PCT NO: |
PCT/JP2013/062220 |
371 Date: |
January 26, 2015 |
Current U.S.
Class: |
348/349 |
Current CPC
Class: |
G06K 9/209 20130101;
G02B 7/34 20130101; G03B 19/12 20130101; G03B 3/10 20130101; G03B
13/36 20130101; G06K 9/00543 20130101; H04N 5/23212 20130101; H04N
5/232122 20180801 |
Class at
Publication: |
348/349 |
International
Class: |
H04N 5/232 20060101
H04N005/232; G06K 9/00 20060101 G06K009/00; G03B 3/10 20060101
G03B003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2012 |
JP |
2012-100150 |
Jul 17, 2012 |
JP |
2012-158796 |
Claims
1. A focus detection device, comprising: a plurality of
micro-lenses at which light fluxes having been transmitted through
an image forming optical system enter, disposed in a
two-dimensional array pattern; a plurality of light receiving
elements disposed in correspondence to each of the plurality of
micro-lenses; a focus detection unit that executes a detection of a
defocus quantity of the image forming optical system by detecting,
based upon outputs from the plurality of light receiving elements,
a phase difference manifested by a plurality of light fluxes having
passed through different areas of the image forming optical system;
and a recognition unit that recognizes, based upon the outputs from
the plurality of light receiving elements, characteristics of a
subject image formed onto the plurality of light receiving elements
via the plurality of micro-lenses, wherein: the focus detection
unit detects the defocus quantity through a method optimal for the
characteristics of the subject image recognized by the recognition
unit.
2. A focus detection device according to claim 1, wherein: the
characteristics of the subject image manifest as a pattern in the
subject image.
3. A focus adjustment device, comprising: a plurality of
micro-lenses disposed in a two-dimensional array pattern so as to
allow light fluxes, having been transmitted through an image
forming optical system, to enter thereat; a plurality of light
receiving elements disposed in correspondence to each of the
plurality of micro-lenses on a rear side of the micro-lens; a
recognition unit that recognizes, based upon light reception
outputs from the plurality of light receiving elements, a pattern
in a subject image formed onto the plurality of light receiving
elements via the plurality of micro-lenses; and a focus adjustment
unit that executes focus adjustment for the image forming optical
system by detecting, based upon the light reception outputs, a
phase difference manifested by a pair of light fluxes having passed
through different areas of the image forming optical system,
wherein: the focus adjustment unit executes focus adjustment
optimal for the pattern in the subject image recognized by the
recognition unit.
4. A focus adjustment device according to claim 3, wherein: the
recognition unit is capable of recognizing at least a cyclical
pattern, an edge pattern and a gradation pattern.
5. A focus adjustment device according to claim 3, wherein: in
correspondence to the pattern in the subject image recognized by
the recognition unit, the focus adjustment unit switches at least
one of; positions of a plurality of light receiving elements
selected for purposes of generating a pair of signal strings for
phase difference detection, a width represented by the pair of
signal strings, a quantity of light receiving elements to be used
when generating the pair of signal strings and whether or not to
remove a low-frequency signal from the pair of signal strings.
6. A focus adjustment device according to claim 3, wherein: the
focus adjustment unit makes a decision, based upon the pattern in
the subject image recognized by the recognition unit, as to whether
or not the detected phase difference indicates a false focus
match.
7. A focus adjustment device according to claim 6, wherein: upon
deciding that the detected phase difference indicates the false
focus match, the focus adjustment unit again detects the phase
difference based upon the pair of light fluxes forming a smaller
opening angle.
8. A focus adjustment device according to claim 6, wherein: upon
deciding that the detected phase difference indicates the false
focus match, the focus adjustment unit reverses a direction along
which a focusing lens included in the image forming optical system
is driven.
9. A focus adjustment device according to claim 6, wherein: if the
recognition unit recognizes a nonuniform pattern formed, via each
of the plurality of micro-lenses, on the plurality of light
receiving elements disposed on the rear side of the micro-lens, and
the detected phase difference is equal to or less than a
predetermined threshold value, the focus adjustment unit decides
that the detected phase difference indicates the false focus
match.
10. A focus adjustment device, comprising: a plurality of
micro-lenses disposed in a two-dimensional array pattern so as to
allow light fluxes, having been transmitted through an image
forming optical system that includes a focusing lens, to enter
thereat; a plurality of light receiving elements disposed in
correspondence to each of the plurality of micro-lenses at
positions at which the light fluxes, having been transmitted
through the micro-lens, enter; a recognition unit that recognizes,
based upon light reception outputs from the plurality of light
receiving elements, a cyclical pattern in a subject image formed
via the plurality of micro-lenses on the plurality of light
receiving elements; a phase difference detection unit that detects,
based upon the light reception outputs, a phase difference
manifested by a pair of light fluxes having passed through
different areas of the image forming optical system; and the focus
adjustment unit that executes focus adjustment for the image
forming optical system by driving the focusing lens based upon the
phase difference detected by the phase difference detection unit,
wherein: if the cyclical pattern is recognized by the recognition
unit, the focus adjustment unit drives the focusing lens along a
direction in which cycles in the cyclical pattern are
lengthened.
11. A focus adjustment device according to claim 10, wherein: the
recognition unit executes a Fourier transform on the light
reception outputs and recognizes the cyclical pattern in a spatial
frequency range.
12. A focus adjustment device according to claim 10, wherein: the
recognition unit recognizes the cyclical pattern by detecting edges
from light reception outputs from the plurality of light receiving
elements corresponding to at least one micro-lens among the
plurality of micro-lenses.
13. A focus detection device according to claim 10, wherein: the
recognition unit recognizes the cyclical pattern by calculating
sums of light reception outputs from the plurality of light
receiving elements corresponding to at least two micro-lenses among
the plurality of micro-lenses and comparing the two sums.
14. A camera equipped with a focus adjustment device according to
claim 3.
Description
TECHNICAL FIELD
[0001] The present invention relates to a focus detection device, a
focus adjustment device and a camera.
BACKGROUND ART
[0002] Focus detection devices that detect focus through a method
known as the phase difference detection method in the related art
detect an extent of image subject image shift based upon the
outputs from a plurality of light receiving elements arrayed in
correspondence to each of micro-lenses disposed in a
two-dimensional pattern. Patent literature 1, for instance,
describes a focus detection device that detects contrast along a
plurality of directions and selects an optimal focus detection
direction among the plurality of directions based upon the detected
contrast.
CITATION LIST
Patent Literature
[0003] Patent literature 1: Japanese Laid Open Patent Publication
No. 2009-198771
SUMMARY OF INVENTION
Technical Problem
[0004] There is an issue with the related art in that accurate and
efficient focus adjustment cannot always be assured, i.e., focus
adjustment for certain types of subjects may be less than accurate
or efficient.
Solution to Problem
[0005] According to the 1st aspect of the present invention, a
focus detection device comprises: a plurality of micro-lenses at
which light fluxes having been transmitted through an image forming
optical system enter, disposed in a two-dimensional array pattern;
a plurality of light receiving elements disposed in correspondence
to each of the plurality of micro-lenses; a focus detection unit
that executes a detection of a defocus quantity of the image
fowling optical system by detecting, based upon outputs from the
plurality of light receiving elements, a phase difference
manifested by a plurality of light fluxes having passed through
different areas of the image forming optical system; and a
recognition unit that recognizes, based upon the outputs from the
plurality of light receiving elements, characteristics of a subject
image formed onto the plurality of light receiving elements via the
plurality of micro-lenses, wherein: the focus detection unit
detects the defocus quantity through a method optimal for the
characteristics of the subject image recognized by the recognition
unit.
[0006] According to the 2nd aspect of the present invention, in the
focus detection device according to the 1st aspect, the
characteristics of the subject image may manifest as a pattern in
the subject image.
[0007] According to the 3rd aspect of the present invention; a
focus adjustment device comprises: a plurality of micro-lenses
disposed in a two-dimensional array pattern so as to allow light
fluxes, having been transmitted through an image forming optical
system, to enter thereat; a plurality of light receiving elements
disposed in correspondence to each of the plurality of micro-lenses
on a rear side of the micro-lens; a recognition unit that
recognizes, based upon light reception outputs from the plurality
of light receiving elements, a pattern in a subject image formed
onto the plurality of light receiving elements via the plurality of
micro-lenses; and a focus adjustment unit that executes focus
adjustment for the image forming optical system by detecting, based
upon the light reception outputs, a phase difference manifested by
a pair of light fluxes having passed through different areas of the
image forming optical system, wherein: the focus adjustment unit
executes focus adjustment optimal for the pattern in the subject
image recognized by the recognition unit.
[0008] According to the 4th aspect of the present invention, in the
focus adjustment device according to the 3rd aspect, the
recognition unit may be capable of recognizing at least a cyclical
pattern, an edge pattern and a gradation pattern.
[0009] According to the 5th aspect of the present invention, it is
preferred that in the focus adjustment device according to the 3rd
or 4th aspect, in correspondence to the pattern in the subject
image recognized by the recognition unit, the focus adjustment unit
switches at least one of; positions of a plurality of light
receiving elements selected for purposes of generating a pair of
signal strings for phase difference detection, a width represented
by the pair of signal strings, a quantity of light receiving
elements to be used when generating the pair of signal strings and
whether or not to remove a low-frequency signal from the pair of
signal strings.
[0010] According to the 6th aspect of the present invention, in the
focus adjustment device according to any one of the 3rd through 5th
aspects, the focus adjustment unit may make a decision, based upon
the pattern in the subject image recognized by the recognition
unit, as to whether or not the detected phase difference indicates
a false focus match.
[0011] According to the 7th aspect of the present invention, in the
focus adjustment device according to the 6th aspect upon deciding
that the detected phase difference indicates the false focus match,
the focus adjustment unit may again detect the phase difference
based upon the pair of light fluxes forming a smaller opening
angle.
[0012] According to the 8th aspect of the present invention, in the
focus adjustment device according to the 6th aspect upon deciding
that the detected phase difference indicates the false focus match,
the focus adjustment unit may reverse a direction along which a
focusing lens included in the image forming optical system is
driven.
[0013] According to the 9th aspect of the present invention, in the
focus adjustment device according to any one of the 6th through the
8th aspects if the recognition unit recognizes a nonuniform pattern
formed, via each of the plurality of micro-lenses, on the plurality
of light receiving elements disposed on the rear side of the
micro-lens, and the detected phase difference is equal to or less
than a predetermined threshold value, the focus adjustment unit may
decide that the detected phase difference indicates the false focus
match.
[0014] According to the 10th aspect of the present invention, a
focus adjustment device comprises: a plurality of micro-lenses
disposed in a two-dimensional array pattern so as to allow light
fluxes, having been transmitted through an image forming optical
system that includes a focusing lens, to enter thereat; a plurality
of light receiving elements disposed in correspondence to each of
the plurality of micro-lenses at positions at which the light
fluxes, having been transmitted through the micro-lens, enter; a
recognition unit that recognizes, based upon light reception
outputs from the plurality of light receiving elements, a cyclical
pattern in a subject image formed via the plurality of micro-lenses
on the plurality of light receiving elements; a phase difference
detection unit that detects, based upon the light reception
outputs, a phase difference manifested by a pair of light fluxes
having passed through different areas of the image forming optical
system; and the focus adjustment unit that executes focus
adjustment for the image forming optical system by driving the
focusing lens based upon the phase difference detected by the phase
difference detection unit, wherein: if the cyclical pattern is
recognized by the recognition unit, the focus adjustment unit
drives the focusing lens along a direction in which cycles in the
cyclical pattern are lengthened.
[0015] According to the 11th aspect of the present invention, in
the focus adjustment device according to the 10th aspect the
recognition unit may execute a Fourier transform on the light
reception outputs and recognizes the cyclical pattern in a spatial
frequency range.
[0016] According to the 12th aspect of the present invention, in
the focus adjustment device according to the 10th or 11th aspect
the recognition unit may recognize the cyclical pattern by
detecting edges from light reception outputs from the plurality of
light receiving elements corresponding to at least one micro-lens
among the plurality of micro-lenses.
[0017] According to the 13th aspect of the present invention, in
the focus detection device according to the 10th or 11th aspect the
recognition unit may recognize the cyclical pattern by calculating
sums of light reception outputs from the plurality of light
receiving elements corresponding to at least two micro-lenses among
the plurality of micro-lenses and comparing the two sums.
[0018] According to the 14th aspect of the present invention, a
camera equipped with the focus adjustment device according to any
one of the 3rd through 13th aspects.
Advantageous Effect of the Invention
[0019] The present invention enables accurate and efficient focus
adjustment in correspondence to a subject pattern.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] (FIG. 1) A sectional view of a camera system, used in
conjunction with interchangeable lenses, which may adopt the
present invention
[0021] (FIG. 2) Perspective of the focus detection unit 104
[0022] (FIG. 3) A schematic illustration of the ranges over which
light fluxes from the micro-lenses 13 enter, superimposed over the
light-receiving surface of the light receiving element array 12
[0023] (FIG. 4) An illustration of the focus detection method
adopted by the body control device 101
[0024] (FIG. 5) A schematic illustration showing a condition in
which focus match is achieved for the focus adjustment target
subject
[0025] (FIG. 6) A schematic illustration showing a condition in
which focus match is not achieved for the focus adjustment target
subject
[0026] (FIG. 7) Examples of patterns that may be recognized by the
body control device 101
[0027] (FIG. 8) A flowchart of focus adjustment control executed by
the body control device 101
[0028] (FIG. 9) A flowchart of the light reception pattern
recognition processing called up in step S130 in FIG. 8
[0029] (FIG. 10) An example of a cyclical pattern that may be
recognized by the body control device 101
[0030] (FIG. 11) A flowchart of focus adjustment control executed
by the body control device 101
[0031] (FIG. 12) A flowchart of the false focus match detection
processing called up in step S350 in FIG. 11
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0032] FIG. 1 is a sectional view of a camera system, used in
conjunction with interchangeable lenses, which adopts the present
invention. A camera 1 comprises a camera body 100 and an
interchangeable lens 200 that can be mounted at/dismounted from the
camera body 100.
[0033] At the interchangeable lens 200, a photographic optical
system comprising a plurality of lenses 202, 203 and 204, and an
aperture 205 having an opening portion are disposed. A light flux
departing a subject passes through the photographic optical system
and the opening portion of the aperture 205 before entering the
camera body 100. It is to be noted that while FIG. 1 shows the
photographic optical system made up with three lenses, the
photographic optical system may include any number of lenses. In
addition, while the aperture 205 in FIG. 1 is disposed between the
lens 203 and the lens 204, the aperture 205 may instead be disposed
further frontward or rearward relative to the photographic optical
system or between other lenses, as known in the related art.
[0034] The lens 203 included in the photographic optical system is
a focusing lens used to adjust the focusing position for the
photographic optical system. The focusing lens 203 is connected to
a lens drive device 206 via a drive mechanism (not shown)
configured with gears and the like. The lens drive device 206,
which includes an actuator (not shown) such as a stepping motor,
drives the focusing lens 203 in direction D running along an
optical axis L of the photographic optical system.
[0035] An aperture drive device 207 is connected to the aperture
205. The aperture drive device 207, which includes an actuator (not
shown) such as a stepping motor, alters the opening radius R at the
aperture 205 by driving a drive mechanism (not shown).
[0036] An image sensor 102 such as a CCD sensor or a CMOS sensor,
capable of capturing a subject image formed by the photographic
optical system, is disposed at the camera body 100. The image
sensor 102 is disposed so that its imaging plane matches a
pre-determined focal plane of the photographic optical system. A
half mirror 103 is disposed between the photographic optical system
and the imaging plane of the image sensor 102 within the camera
body 100. The half mirror 103, which may be configured with, for
instance, a pellicle mirror, allows part of the subject light
having departed the photographic optical system to be transmitted
toward the image sensor 102 and reflects the remaining subject
light toward the top of the camera body 100. The reflected light
enters a focus detection unit 104 disposed on the upper side in the
camera body 100. Structural features of the focus detection unit
104 will be described in detail later.
[0037] A body control device 101 comprising a microprocessor and
its peripheral circuits is disposed at the camera body 100. The
body control device 101 controls various units at the camera body
100 by executing a specific control program read out from a storage
medium (not shown) where the program is stored in advance. The
interchangeable lens 200 includes a lens control device 201
likewise comprising a microprocessor and its peripheral circuits.
The lens control device 201 controls various units in the
interchangeable lens 200 by executing a specific control program
read out from a storage medium (not shown) where the control
program is stored in advance. It is to be noted that the body
control device 101 and the lens control device 201 may each be
configured with an electronic circuit capable of executing
operation equivalent to the control program.
[0038] The body control device 101 and the lens control device 201
are configured so as to be able to communicate with each other via
an electric contact point (not shown) disposed in the vicinity of
the lens mount. Through data communication enabled via the electric
contact point, the body control device 101 transmits, for instance,
a drive command for the focusing lens 203 and a drive command for
the aperture 205 to the lens control device 201. It is to be noted
that the data communication may be carried out through a method
(e.g., wireless communication or optical communication) other than
the electrical signal exchange via the electric contact point.
[0039] In response to a specific focus adjustment operation (e.g.,
a halfway press operation of a shutter release switch (not shown))
the body control device 101 detects a defocus quantity representing
the extent of defocus based upon an output from the focus detection
unit 104 and transmits a drive command to the lens control device
201 so as to drive the focusing lens 203 by an extent corresponding
to the defocus quantity. In response to this drive command, the
lens control device 201 engages the lens drive device 206 to drive
the focusing lens 203. Consequently, a focus match is achieved for
a specific subject.
[0040] A monitor 110 constituted with, for instance, a liquid
crystal display element, is disposed on the rear surface of the
camera 1. The body control device 101 uses this monitor 110 when,
for instance, reproducing still image data or movie image data
obtained through a shooting operation, displaying a settings menu
in which photographing parameters (aperture number, shutter speed
and the like) can be selected for the camera 1, displaying a live
view image and the like.
[0041] An electronic viewfinder unit 108, which includes a display
element such as a liquid crystal display element, is disposed at an
upper portion of the camera body 1. The photographer is able to
view a subject image or the like displayed at the display element
of the electronic viewfinder unit 108 via an eyepiece lens 106
through a finder portion 107. When the camera 1 is set in the
photographing mode, the body control device 101 engages the image
sensor 102 so as to capture a subject image over predetermined
intervals (e.g., every 1/60 sec), generates a live view image based
upon the image capturing signals and displays the live view image
thus created at the monitor 110 or the electronic viewfinder unit
108.
[0042] In response to a specific still image shooting operation
(e.g., a full press operation of the shutter release switch (not
shown)) performed in the photographing mode, the body control
device 101 executes photographing control. At this time, the body
control device 101 engages the image sensor 102 to capture the
subject image by controlling the shutter and the like (not shown).
It then executes various types of image processing on image
capturing signals output from the image sensor 102 and stores still
image data generated through the image processing into a storage
medium (not shown) such as a memory card.
[0043] (Description of the Focus Detection Unit 104)
[0044] FIG. 2 shows the focus detection unit 104 in a perspective.
The focus detection unit 104 comprises a micro-lens array 11 and a
light receiving element array 12 disposed further rearward relative
to the micro-lens array 11.
[0045] Numerous micro-lenses 13 are disposed in a two-dimensional
pattern at the micro-lens array 11. Subject light having been
reflected at the half mirror 103 passes through a micro-lens 13
among the micro-lenses 13 and enters the light-receiving surface of
the light receiving element array 12. Numerous light receiving
element groups 14 where light fluxes having passed through
individual micro-lenses 13 enter are arrayed in a two-dimensional
pattern at the light-receiving surface (the surface facing toward
the micro-lens array 11) of the light receiving element array 12.
Each light receiving element group is made up with 25 light
receiving elements disposed in a 5 (row).times.5 (column) array. A
light flux having passed through a given micro-lens 13 enters one
of the light receiving element groups 14, and the plurality of
light receiving elements constituting the particular light
receiving element group 14 receives the light flux.
[0046] The area of the surface of the micro-lens array 11 (the
surface where the subject light enters) over which no micro-lens 13
is present is shielded with a light-blocking mask. For this reason,
only a light flux that has passed through a micro-lens 13 is
allowed to enter the light receiving element array 12.
[0047] The light receiving element array 12 is disposed at a
position set apart from the micro-lens array 11 by a distance equal
to the focal length of the micro-lenses 13. In order to assure
clarity in the illustration, the distance "d" between the
micro-lens array 11 and the light receiving element array 12 is
exaggerated in FIG. 2.
[0048] It is to be noted that FIG. 2 only shows part of the
micro-lens array 11 and part of the light receiving element array
12. Namely, the actual micro-lens array and light receiving element
array include greater numbers of micro-lenses 13 and light
receiving element groups 14. In addition, the quantity of light
receiving elements included in each light receiving element group
14 may be more than or fewer than 25 and the light receiving
elements may be arrayed in a pattern other than that shown in FIG.
2.
[0049] FIG. 3 is a schematic illustration of the ranges of entry of
light fluxes, having departed micro-lenses 13, superimposed over
the light-receiving surface of the light receiving element array
12. When the f-number of the photographic optical system matches
the f-number of the micro-lenses 13, a light flux having departed a
given micro-lens 13 enters within the range of a circle 15
enclosing a light receiving element group 14. When the aperture 205
is constricted and the f-number at the photographic optical system
takes on a value greater than the f-number of the micro-lenses 13
(when the photographic optical system is darkened relative to the
micro-lenses 13), the size of the circles 15 becomes smaller than
that shown in FIG. 3.
[0050] It is to be noted that when the f-number at the photographic
optical system is set to a value smaller than the f-number of the
micro-lenses 13 (i.e., when the photographic optical system is
rendered lighter relative to the micro-lenses 13), the size of the
circles 15 becomes greater than that shown in FIG. 3 and individual
circles 15 overlap one another. Namely, crosstalk between light
fluxes having passed through the micro-lenses 13 occurs. If light
fluxes having passed through a plurality of micro-lenses 13 enter a
single light receiving element in this state, accurate focus
detection is no longer possible. During focus detection, the body
control device 101 in the embodiment adjusts the aperture 205 so as
to match the f-number at the photographic optical system with the
f-number of the micro-lenses 13. In other words, the crosstalk
phenomenon described above does not occur during focus detection
since it is ensured that each subject light flux enters within the
range of a circle 15 shown in FIG. 3.
[0051] (Description of the Focus Detection Method)
[0052] The body control device 101 detects the focal point through
the method known as the phase difference detection method whereby
an image shift quantity, i.e., the extent of image shift pertaining
to the subject image, is detected based upon an output from the
focus detection unit 104. The following is a description of the
focus detection method adopted by the body control device 101.
[0053] FIG. 4(a) shows a single row of light receiving element
groups 14 engaged in focus detection among the numerous light
receiving element groups 14 shown in FIG. 3. While FIG. 4(a) shows
only 5 light receiving element groups 14, it is desirable to select
a greater number of light receiving element groups 14 for focus
detection. In the following description, different reference
numerals 14a through 14e are used to refer to the individual light
receiving element groups 14.
[0054] FIG. 4(b) is a schematic illustration of the relationships
between the light receiving element groups 14a through 14e and the
focus detection pupils. The micro-lenses 13a through 13e are
disposed so that their apexes are substantially in alignment with a
predetermined focal plane 17 of the photographic optical system.
The micro-lens 13c projects the shapes of a pair of light receiving
elements 16lc and 16rc disposed to the rear thereof onto an exit
pupil 20 set apart from the micro-lens 13c by a projecting distance
d2, and the shapes of the light receiving elements thus projected
form focus detection pupils 21 and 22. The projecting distance d2
is determined in correspondence to the curvature and the refractive
index of the micro-lens 13c, the distance between the micro-lens
13c and the light receiving element array 12, and the like. The
pair of focus detection pupils 21 and 22 and the pair of light
receiving elements 161c and 16rc achieve a relationship conjugate
with each other via the micro-lens 13c.
[0055] It is to be noted that while an explanation has been given
above in reference to the pair of light receiving elements 16lc and
16rc belonging to the light receiving element group 14c set on the
optical axis L and the pair of focus detection pupils 21 and 22 so
as to simplify the description, a pair of light receiving elements
in a light receiving element group taking up a position away from
the optical axis L, too, receive a light flux arriving at the
corresponding micro-lens from a pair of focus detection pupils.
[0056] The light receiving element 16lc outputs a light reception
signal corresponding to the intensity of an image formed on the
micro-lens 13c with a focus detection light flux 24 having passed
through the focus detection pupil 22 and traveled toward the
micro-lens 13c. Likewise, the light receiving element 16rc outputs
a light reception signal corresponding to the intensity of an image
formed on the micro-lens 13c with a focus detection light flux 23
having passed through the focus detection pupil 21 and traveled
toward the micro-lens 13c.
[0057] Accordingly, information pertaining to intensity
distributions of a pair of images formed on the light receiving
element array 12 with focus detection light fluxes each passing
through the focus detection pupil 21 and 22 can be obtained by
acquiring the light reception outputs of each pair of light
receiving elements corresponding to the focus detection pupil 21
and the focus detection pupil 22 from the plurality of light
receiving element groups 14a through 14e disposed along a straight
line, as shown in FIG. 4(a). By executing an image shift detection
operation of the known art in conjunction with the information thus
acquired, an image shift quantity representing the extent of image
shift manifested by the pair of images is detected through a
detection method commonly referred to as the split pupil phase
difference detection method. Then, the image shift quantity is
converted in correspondence to the distance between the
gravitational centers of the pair of focus detection pupils 21 and
22 so as to calculate a defocus quantity representing the deviation
of the current imaging plane relative to the predetermined focal
plane.
[0058] The image shift detection operation and the conversion
operation will be described in more specific terms. The body
control device 101 first designates the value obtained by adding
together the light reception outputs of the three middle light
receiving elements 16la at the left end column in the light
receiving element group 14a as a(1). Likewise, it calculates the
sums a(2) through a(5) in correspondence to the light receiving
element groups 14b through 14e, each by adding together the light
reception outputs of the three middle light receiving elements
16lb, 16lc, 16ld or 16le at the left end column in the
corresponding light receiving element group. Next, for the light
receiving element groups 14a through 14e, it calculates sums by
adding together the light reception outputs of the three middle
light receiving elements 16ra through 16re at the right end columns
and designates the sums as b(1) through b(5). A pair of signal
strings a(i) and b(i) generated as described above constitutes
information pertaining to the intensity distribution of the pair of
images mentioned earlier. The body control device 101 executes a
correlation operation for the pair of signal strings by
individually offsetting the signal strings in small steps and
calculates a correlation quantity in correspondence to each offset
quantity. Then, based upon the correlation quantity calculation
results, it determines the offset quantity in correspondence to
which a minimum correlation quantity is calculated (the offset
quantity at which a maximum degree of correlation quantity
manifests). The body control device 101 multiplies the offset
quantity by a predetermined conversion coefficient in order to
calculate a defocus quantity representing the extent of defocusing
manifested by the subject image relative to the predetermined focal
plane.
[0059] It is to be noted that the row of light receiving element
groups 14 to be engaged in focus detection, among the numerous
light receiving element groups 14, may be selected through any
method. For instance, the user may be asked to specify the position
of the focusing target subject and light receiving element groups
14 present at the particular position may be selected. As an
alternative, light receiving element groups 14 present at a
predetermined position, such as the center of the photographic
field, may be selected.
[0060] (Description of a Cyclical Pattern Formed on the
Light-Receiving Surface)
[0061] For each session of focus detection and focus adjustment,
the body control device 101 recognizes, through a pattern-matching
technology of the known art, the pattern of an image formed via the
micro-lenses 13 onto the light-receiving surface of the light
receiving element array 12. Based upon the recognized pattern, it
alters the specific details of the focus detection and the focus
adjustment. The following is a description of the pattern of an
image formed on the light-receiving surface of the light receiving
element array 12.
[0062] FIG. 5 is a schematic illustration of a subject 31, a
photographing optical system 30, a subject image 33, the
predetermined focal plane 17, the micro-lens array 11 and the light
receiving element array 12 in a state in which the focus adjustment
target subject is in focus. It is to be noted that the photographic
optical system is represented by a single lens in the schematic
illustration in FIG. 5.
[0063] When a focus match is achieved for the focus adjustment
target subject 31, the image (subject image) 33 of the subject 31,
formed by the photographic optical system 30, is substantially in
alignment with the predetermined focal plane 17, and a light flux
35, having departed a point 32 on the subject 31 and passed through
the photographic optical system 30, has converged so that its
section is smaller than the permissible circle of confusion on the
predetermined focal plane 17, as illustrated in FIG. 5(a).
[0064] FIG. 5(b) shows an area near the focus detection unit 104 in
an enlarged view. In this condition, a light flux having departed a
point 34 on the subject image 33 enters with substantial uniformity
on the rear side of the micro-lens 13c, as illustrated in FIG.
5(c). The light flux, having departed the point 34, does not enter
any of the other micro-lenses 13, and no light flux from any other
point on the subject image 33 enters on the rear side of the
micro-lens 13c.
[0065] FIG. 6 is a schematic illustration of the subject 31, the
photographic optical system 30, the subject image 33, the
predetermined focal plane 17, the micro-lens array 11 and the light
receiving element array 12 in a state in which the focus adjustment
target subject is not in focus.
[0066] When the image 33 of the subject 31, formed via the
photographic optical system 30, is set apart from the predetermined
focal plane 17 by a distance equal to or greater than twice the
focal length of the micro-lenses 30, the light flux 35, having
departed the point 32 on the subject 31 and passed through the
photographic optical system 30 reaches the predetermined focal
plane 17 as light widening over a certain range, as illustrated in
FIG. 6(a). This means that the light flux 35, having departed the
point 32, enters a plurality of micro-lenses 13. In addition, as
illustrated in the enlarged view in FIG. 6(b), light fluxes, having
departed a plurality of points on the subject image 33, enter a
single micro-lens 13c. As a result, an image 36 is projected onto
the rear side of the micro-lens 13c in correspondence to the shape
of the subject image 33 and the positional relationship between the
subject image 33 and the micro-lenses 13.
[0067] Next, patterns that may be recognized by the body control
device 101 to be used for focus detection and focus adjustment in
the embodiment will be described in reference to the examples
presented in FIG. 7.
[0068] FIG. 7(a1) shows a subject image 33a with vertical stripes.
If this subject image 33a is formed at a position somewhat set
apart from the predetermined focal plane 17, the pattern shown in
FIG. 7(a2) is formed on the light-receiving surface of the light
receiving element array 12. In this situation, the light reception
outputs obtained from light receiving elements set consecutively
along the lateral direction in a single row in a given light
receiving element group 14 will include a plurality of peaks each
in correspondence to a vertical stripe.
[0069] The body control device 101 determines that the subject 31
is a cyclic subject taking on a cyclical pattern in a case such as
this in which the light reception outputs of the light receiving
elements set side-by-side in a single row along a specific
direction within a given light receiving element group 14 include a
plurality of peaks. In this situation, if the absolute value of the
defocus quantity is less than a predetermined threshold value
(i.e., if the current condition is judged to be a focus match
state) in the subsequent focus detection operation, the particular
defocus quantity is determined to be incorrect (i.e., the current
condition is a false focus match state). The rationale for this
decision-making is that if a focus match was achieved for the
subject 31, a uniform light flux would enter at a single light
receiving element group 14 as illustrated in FIG. 5(c) and that a
pattern such as that shown in FIG. 7(a2) could never be formed in a
true focus match state.
[0070] Upon determining that the defocus quantity is incorrect
(i.e., the current condition is a false focus match state), the
body control device 101 re-executes the focus detection operation
by reducing the angle of detection range. Namely, instead of the
light receiving elements at the two end columns on the left side
and the right side shown in FIG. 4(a), light receiving elements at
inner positions are used to create a pair of signal strings and the
image shift detection operation and the conversion operation are
executed in conjunction with the pair of signal strings thus
created.
[0071] The subject image shown in FIG. 7(b1) will be explained
next. FIG. 7(b1) shows a subject image 33b with a clear boundary
(edge) dividing it along the left/right direction. If this subject
image 33b is formed at a position somewhat set apart from the
predetermined focal plane 17, the pattern shown in FIG. 7(b2) is
formed on the light-receiving surface of the light receiving
element array 12.
[0072] If outputs completely different from each other (e.g.,
circles 15a and 15c) are detected from a pair of light receiving
element groups 14 present in close proximity to each other and
these two different outputs are inverted in the output from a light
receiving group 14 (e.g., a circle 15b) present between the pair of
light receiving element groups, the body control device 101
determines that the subject 31 is an edge subject assuming an edge
pattern. In the subsequent focus detection operation, it generates
a pair of signal strings to be used in image shift detection
operation from light receiving element groups 14 set side-by-side
in a single row running perpendicular to the detected edge. In
addition, the light receiving element groups 14, the outputs from
which are to be sampled in order to generate the pair of signal
strings, are selected from a range narrower than normal and thus,
the signal strings assume a length smaller than normal. The
rationale for this is that since there is obviously a well-defined
edge, only an area around the edge needs to be the focus detection
target.
[0073] The subject image shown in FIG. 7(c1) will be explained
next. FIG. 7(c1) shows a subject image 33c with a gradation pattern
manifesting a gradual change in luminance or chromaticity along the
up/down direction. If this subject image 33c is formed at a
position somewhat set apart from the predetermined focal plane 17,
the pattern shown in FIG. 7(c2) is formed on the light-receiving
surface of the light receiving element array 12.
[0074] If a plurality of light receiving element groups 14 disposed
in close proximity to one another output light reception data
uniformly indicating a gradual change (or indicating hardly any
change), the body control device 101 determines that the subject 31
is a gradation subject with a gradation pattern. Subsequently,
after generating a pair of signal strings, it directly executes an
image shift detection operation without applying a high pass filter
processing, which would normally be executed on the signal strings
in order to remove an excess low-frequency component. In addition,
if the difference between the high signal level and the low signal
level in the pair of signal strings having been generated is less
than a predetermined value, it determines that the subject 31 is a
low contrast subject, requiring improved accuracy in the image
shift detection operation and, accordingly, it generates a pair of
signal strings by sampling data from a greater number of light
receiving elements. For instance, it may generate a pair of signal
strings by calculating the sum of the outputs from six light
receiving elements instead of the sum of outputs from three light
receiving elements as shown in FIG. 4(a).
[0075] As described above, the body control device 101 in the
embodiment customizes the details of the focus detection operation
so as to execute focus detection operation best suited for the
specific pattern of the image formed via the micro-lenses 13 onto
the light receiving element array 12. As explained earlier, the
body control device 101 recognizes three different patterns (a
cyclical pattern, an edge pattern and a gradation pattern) such as
those shown in FIG. 7(a1) through FIG. 7(c1) through a pattern
matching operation of the known art. There are no restrictions
imposed with regard to the mariner with which the pattern matching
operation is executed, as long as at least these three patterns can
be recognized through the operation.
[0076] (Description of Focus Adjustment Control)
[0077] FIG. 8 presents a flowchart of focus adjustment control
executed by the body control device 101. The processing shown in
FIG. 8 is included in a control program read out from a memory (not
shown) and executed by the body control device 101.
[0078] First, in step S100, the body control device 101 makes a
decision as to whether or not the user has performed a specific
focus adjustment operation (e.g., halfway press operation at the
shutter release switch). Until the user performs a focus adjustment
operation, the body control device 101 repeatedly executes step
S100 and once a focus adjustment operation is executed, the
operation proceeds to step S110. In step S110, the body control
device 101 executes charge control of the light receiving element
array 12 and then, in step S120, it reads out the light reception
outputs from the individual light receiving element groups 14. In
step S130, the body control device 101 executes light perception
pattern recognition processing (to be described later) based upon
the light reception outputs having been read out and recognize a
pattern that may be one of those shown in FIG. 7(a1) through FIG.
7(c1).
[0079] In step S140, the body control device 101 executes an image
shift detection operation and a conversion operation by reflecting
the light reception pattern recognition results in the details
thereof in conjunction with part of the light reception outputs
having been read out in step S120, and calculates a defocus
quantity through these operations. In step S150, it calculates a
drive quantity representing the extent to which the focusing lens
203 needs to be driven to achieve a focus match based upon the
defocus quantity. In step S160, a decision is made as to whether or
not the focusing lens 203 needs to be driven, i.e., whether or not
a focus match state has already been achieved, and if the current
condition is already a focus match state, the processing in FIG. 8
ends. If a focus match state has not been achieved, the operation
proceeds to step S170, in which the body control device 101
executes lens drive control before the operation returns to step
110. The body controls device 101 executing the lens drive control
transmits a drive instruction to the lens control device 201 so
that the focusing lens 203 is driven by an extent corresponding to
the lens drive quantity having been calculated in step S150. In
response to this drive instruction, the lens control device 203
engages the lens drive device 206 in operation to drive the
focusing lens 203.
[0080] FIG. 9 presents a flowchart of the light reception pattern
recognition processing called up in step S130 in FIG. 8. As is the
processing shown in FIG. 8, this processing is included in the
control program executed by the body control device 101. First, in
step S200, the body control device 101 extracts a characteristic
quantity pertaining to the image projected via the micro-lenses 13
based upon the light reception outputs from the individual light
receiving element groups 14. The characteristic quantity is
determined in correspondence to a color, a shape, a height, a
position, a width, an area and the like pertaining to the image,
and no restrictions whatsoever are imposed with regard to the
characteristic quantity as long as it enables recognition of at
least three different types of patterns such as those shown in FIG.
7(a1) through FIG. 7(c1). In the following step S210, the body
control device 101 recognizes a pattern based upon the extracted
characteristic quantity
[0081] In step S220, the body control device 101 makes a decision
as to whether or not the recognized pattern is a cyclical pattern.
Upon deciding that a cyclical pattern has been recognized, the
operation proceeds to step S270 to select the focus detection/focus
adjustment setting for a cyclical subject. Namely, a setting
whereby a defocus quantity, the absolute value of which is less
than a predetermined threshold value (i.e., indicating a focus
match state) is determined to be incorrect (i.e., the current
condition is a false focus match state) is selected. Upon deciding
that the defocus quantity is incorrect (the current condition is a
false focus match state), the body control device 101 re-executes
the focus detection calculation by narrowing the angle of detection
range.
[0082] If a cyclical pattern has not been recognized, the operation
proceeds to step S230 to make a decision as to whether or not the
recognized pattern is an edge pattern. If an edge pattern has been
recognized, the operation proceeds to step S260, in which the focus
detection/focus adjustment setting for an edge subject is selected.
Namely, a pair of signal strings to be used for purposes of image
shift detection operation is generated by sampling data output from
light receiving element groups 14 set in a single row running
perpendicular to the direction in which the detected edge runs. In
addition, the light receiving element groups 14, the outputs from
which are to be sampled in order to generate the pair of signal
strings, are selected from a narrower range than normal, so as to
reduce the length of the signal strings relative to the regular
signal string length.
[0083] If an edge pattern has not been recognized, the operation
proceeds to step S240 to make a decision as to whether or not the
recognized pattern is a gradation pattern. If a gradation pattern
has been recognized, the operation proceeds to step S250, in which
the focus detection/focus adjustment setting for a gradation
subject is selected. Namely, once a pair of signal strings has been
generated, an image shift detection operation is executed without
applying a high pass filter to the signal strings. In addition, if
the difference between the high signal level and the low signal
level in the pair of signal strings having been generated is less
than a predetermined value, the subject 31 is judged to be a low
contrast subject requiring improved accuracy in the image shift
detection operation, and accordingly, a pair of signal strings is
generated by sampling data from a greater number of light receiving
elements.
[0084] The camera system in the first embodiment described above
achieves the following advantages.
[0085] (1) Based upon the light reception outputs from light
receiving element groups 14, each disposed on the rear side of one
of a plurality of micro-lenses 13 disposed in a two-dimensional
array and each made up with a plurality of light receiving
elements, the body control device 101 recognizes the pattern of a
subject image formed via the plurality of micro-lenses 13 onto the
light-receiving surface of the light receiving element array 12,
and executes focus adjustment optimal for the recognized pattern by
detecting the phase difference between a pair of light fluxes
having passed through different areas of the photographic optical
system based upon light reception outputs provided from the light
receiving element array 12. As a result, accurate and efficient
focus adjustment optimal for the subject pattern is enabled.
[0086] (2) After recognizing a cyclical pattern, the body control
device 101 determines that the current condition is a false focus
match state, even if a focus match state is detected, and
re-executes the focus detection operation by narrowing the angle of
detection range. Through these measures, accurate and efficient
focus adjustment is enabled even when the subject has, for
instance, a striped pattern, which tends to readily cause a false
focus match.
[0087] (3) Upon recognizing an edge pattern, the body control
device 101 selects fewer than usual light receiving element groups
14 from light receiving element groups 14 set consecutively in a
single row running perpendicular to the detected edge, and
generates a pair of signal strings to be used for purposes of image
shift detection operation, by sampling outputs from the selected
light receiving element groups 14. Through these measures, accurate
and efficient focus adjustment is achieved for a subject with a
clearly defined edge by excluding any influence of noise and the
like present in areas other than the edge area. In addition, since
signal strings that are shorter than normal are used, the focus
detection operation can be executed at higher speed.
[0088] (4) Upon recognizing a gradation pattern, the body control
device 101 generates a pair of signal strings and then immediately
executes an image shift detection operation without applying a high
pass filter to the signal strings. In addition, if the difference
between the high signal level and the low signal level in the pair
of signal strings having been generated is less than a
predetermined value, it decides that the subject 31 is a low
contrast subject requiring improved accuracy in the image shift
detection operation and accordingly, generates a pair of signal
strings by sampling outputs from a greater number of light
receiving elements. Through these measures, accurate and efficient
focus adjustment is achieved for a subject such as a gradation
subject for which focus detection cannot be easily executed.
Second Embodiment
[0089] The camera system in this embodiment adopts a structure
identical to that of the camera system achieved in the first
embodiment shown in FIG. 1. The second embodiment only differs from
the first embodiment in the focus detection processing executed by
the body control device 101. The following explanation will focus
on the feature of the current embodiment distinguishing it from the
first embodiment, and a repeated explanation of other aspects of
the embodiment similar to those of the first embodiment will not be
provided.
[0090] FIG. 10(a) shows a subject image 43a with vertical stripes
running along the up-down direction. The vertical stripes in the
subject image 43a are set over cycles T1 along the lateral
direction, thereby achieving a cyclical pattern. When the subject
image 43a is formed at a position somewhat set apart from the
predetermined focal plane 17, the cyclical pattern shown in FIG.
10(b) is formed onto the light-receiving surface of the light
receiving element array 12. By executing the pattern matching
processing explained earlier on the light reception outputs from
the light receiving element array 12, the body control device 101
recognizes the cyclical pattern such as that shown in FIG. 10(a) of
the subject 31. The body control device 101, having recognized such
a cyclical pattern, decides in the subsequent focus detection
operation that any defocus quantity, the absolute value of which is
less than a predetermined threshold value (i.e., indicating a focus
match state), is incorrect (i.e., the current condition is a false
focus match state).
[0091] Upon deciding that the defocus quantity is incorrect (i.e.,
the current condition is a false focus much state), the body
control device 101 engages the lens drive device 203 in operation
so as to drive the focusing lens 203 by a specific extent along the
direction in which the cycles of the cyclical pattern having been
recognized are lengthened and then re-executes the focus detection
operation. For instance, if the current false focus match state
results from focus adjustment having been executed by driving the
focusing lens 203 along the direction toward infinity, it will
drive the focusing lens 203 along the opposite direction (toward
close-up). Through these measures, the cyclical pattern with the
cycles T2 shown in FIG. 10(b) is altered to a cyclical pattern
shown in FIG. 10(c) with cycles T3, longer than the cycles T2.
[0092] (Description of Focus Adjustment Control)
[0093] FIG. 11 presents a flowchart of the focus adjustment control
executed by the body control device 101. The processing shown in
FIG. 11 is included in a control program read out from a memory
(not shown) and executed by the body control device 101.
[0094] First, in step S300, the body control device 101 makes a
decision as to whether or not the user has performed a specific
focus adjustment operation (e.g., a halfway press operation at the
shutter release switch). Until the user performs a focus adjustment
operation, the body control device 101 repeatedly executes step
S300 and once a focus adjustment operation is executed, the
operation proceeds to step S310. In step S310, the body control
device 101 executes charge control of the light receiving element
array 12 and then, in step S320, it reads out the light reception
outputs from the individual light receiving element groups 14.
[0095] In step S330, the body control device 101 executes an image
shift (phase difference) detection operation and a conversion
operation in conjunction with part of the light reception outputs
having been read out in step S320 and calculates a defocus quantity
through these operations. Then, in step S360, a decision is made as
to whether or not the focusing lens 203 needs to be driven, i.e.,
whether or not the current condition is already a focus match
state, and if it is decided that a focus match state has already
been achieved, the operation proceeds to step S350. If, on the
other hand, it is decided that a focus match state has not been
achieved, the operation proceeds to step S370 to calculate a drive
quantity representing the extent to which the focusing lens 203
needs to be driven to achieve a focus match, based upon the defocus
quantity having been calculated. The body control device 101 then
executes lens drive control before the operation returns to step
S310. The body control device 101 executing the lens drive control
transmits a drive instruction to the lens control device 201 so
that the focusing lens 203 is driven by an extent corresponding to
the lens drive quantity having been calculated in step S370. In
response to this drive instruction, the lens control device 203
engages the lens drive device 206 in operation to drive the
focusing lens 203.
[0096] In step S350, the body control device 101 executes the false
focus match decision-making processing to be described later. In
step S360, a decision is made as to whether or not a false focus
match has been detected. If it is decided that a false focus match
has not been detected, the current condition is a true focus match
state and, accordingly, the processing shown in FIG. 11 ends. If,
on the other hand, it is decided that a false focus match has been
detected, the operation proceeds to step S390, in which the body
control device 101 determines the direction along which the
focusing lens 203 needs to be driven in order to lengthen the
cycles of the cyclical pattern formed on the light receiving
element array 12.
[0097] For instance, if following the start of the processing shown
in FIG. 11, the operation has proceeded to step S390 after
deciding, in step S340, that the current condition is not a focus
match state, and accordingly, driving the focusing lens 203 so as
to achieve a focus match state, "the drive direction along which
the cycles of the cyclical pattern are lengthened" is the direction
opposite from the direction in which the focusing lens 203 has been
driven.
[0098] It is to be noted that if, following the start of the
processing in FIG. 11, the operation has proceeded to step S390
without driving the focusing lens 203 even once, the focusing lens
203 should first be driven along a specific direction and then the
cycles in the cyclical pattern should be checked to determine if
the cycles have been lengthened. At this time, if the cycles have
been shortened, the focusing lens 203 should be driven along the
direction opposite from the direction in which the focusing lens
203 was initially driven and thus, it is possible that the focusing
lens 203 should be driven along the "drive direction along which
the cycles of the cyclical pattern are lengthened".
[0099] In step S395, the body control device 101 executes drive
control for the focusing lens 203 so as to drive the focusing lens
203 by a specific extent along the particular direction having been
determined in step S390. In more specific terms, it transmits a
drive instruction to the lens control device 201 so as to drive the
focusing lens 203 by a specific extent along the direction.
Subsequently, the operation returns to step S310 to repeatedly
execute the processing starting with the charge control for the
light receiving element array 12.
[0100] FIG. 12 presents a flowchart of the false focus match
detection processing called up in step S350 in FIG. 11. As is the
processing shown in FIG. 11, this processing is included in the
control program executed by the body control device 101. First, in
step S400, the body control device 101 detects the light receiving
element achieving the greatest light reception output (i.e., the
peak position in the light reception outputs) among the various
light receiving elements having been used in the phase difference
detection in step S330 in FIG. 11. In the following step S405, the
body control device 101 extracts a characteristic quantity
pertaining to the image having been projected via the corresponding
micro-lens 13 from the light reception outputs from the light
receiving element group 14 (the light receiving element group 14
covered by the micro-lens 13 that covers the light receiving
element) to which the light receiving element, having been detected
in step S400 belongs. The characteristic quantity is determined in
correspondence to a color, a shape, a height, a position, a width,
an area and the like pertaining to the image, and no restrictions
whatsoever are imposed with regard to the characteristic quantity
as long as it enables recognition of at least a cyclical pattern
such as that shown in FIG. 10(b). In the following step S410, the
body control device 101 recognizes the cyclical pattern based upon
the extracted characteristic quantity.
[0101] In step S420, the body control device 101 makes a decision
as to whether or not a cyclical pattern has been recognized. Upon
deciding that a cyclical pattern has been recognized, the operation
proceeds to step S410 to decide that the current condition is a
false focus match state. In other words, it is decided that the
defocus quantity, having been calculated in step S330 in FIG. 11,
is not correct.
[0102] The camera system in the second embodiment described above
achieves the following advantages.
[0103] (1) Based upon the light reception outputs from light
receiving element groups 14, each disposed on the rear side of one
of a plurality of micro-lenses 13 disposed in a two-dimensional
array and each made up with a plurality of light receiving
elements, the body control device 101 recognizes the pattern of a
subject image fowled via the plurality of micro-lenses 13 onto the
light-receiving surface of the light receiving element array 12,
and executes focus adjustment optimal for the recognized pattern by
detecting the phase difference between a pair of light fluxes
having passed through different areas of the photographic optical
system based upon light reception outputs provided from the light
receiving element array 12. As a result, accurate and efficient
focus adjustment optimal for the subject pattern is enabled.
[0104] (2) After recognizing a cyclical pattern, the body control
device 101 determines that the current condition is a false focus
match state, even if a focus match state is detected, and
re-executes the focus detection operation by narrowing the angle of
detection range. Through these measures, accurate and efficient
focus adjustment is enabled even when the subject has, for
instance, a striped pattern, which tends to readily cause a false
focus match.
[0105] (3) Upon recognizing an edge pattern, the body control
device 101 selects fewer than usual light receiving element groups
14 from light receiving element groups 14 set in a single row
running perpendicular to the detected edge, and generates a pair of
signal strings to be used for purposes of image shift detection
operation, by sampling outputs from the selected light receiving
element groups 14. Through these measures, accurate and efficient
focus adjustment is achieved for a subject with a clearly defined
edge by excluding any influence of noise and the like present in
areas other than the edge area. In addition, since signal strings
that are shorter than normal are used, the focus detection
operation can be executed at higher speed.
[0106] (4) Upon recognizing a gradation pattern, the body control
device 101 generates a pair of signal strings and then immediately
executes an image shift detection operation without applying a high
pass filter to the signal strings. In addition, if the difference
between the high signal level and the low signal level in the pair
of signal strings having been generated is less than a
predetermined value, it decides that the subject 31 is a low
contrast subject requiring improved accuracy in the image shift
detection operation and accordingly, generates a pair of signal
strings by sampling outputs from a greater number of light
receiving elements. Through these measures, accurate and efficient
focus adjustment is achieved for a subject such as a gradation
subject for which focus detection cannot be easily executed.
[0107] The following variations are also within the scope of the
present invention, and any one of or a plurality of the variations
may be adapted in combination with either of the embodiments.
[0108] (Variation 1)
[0109] While five light receiving element groups 14a through 14c,
taking up consecutive positions along the lateral direction, are
selected for purposes of focus detection in the example described
in reference to FIG. 3, focus detection may be executed by using
light receiving element groups 14 set side-by-side in a single row
running along a different direction. In addition, more or fewer
than five light receiving element groups 14 may be selected and it
is not strictly necessary to select consecutive light receiving
element groups 14. For instance, light receiving element groups 14
disposed at every second position may be selected.
[0110] (Variation 2)
[0111] Instead of re-executing the focus detection operation by
narrowing the angle of detection range upon deciding that the
current condition is a false focus match state after recognizing a
cyclical pattern, the direction in which the focusing lens 203 is
driven may be reversed. For instance, if it is decided that the
current condition is a false focus match state after or while the
focusing lens 203 is driven toward the close-up position, focus
detection may be re-executed by driving the focusing lens 203
toward the infinity position.
[0112] (Variation 3)
[0113] The patterns recognized by the body control device 101 in
the embodiments described above, i.e., a cyclical pattern, an edge
pattern and a gradation pattern, are examples and the body control
device 101 may recognize another pattern and execute focus
detection operation and focus adjustment control optimal for the
particular pattern. In addition, the body control device 101 may
recognize a cyclical pattern only or an edge pattern only.
[0114] (Variation 4)
[0115] The present invention may be adopted in conjunction with a
micro-lens array 11 and a light receiving element array 12
different from those shown in FIG. 2. For instance, the
micro-lenses 13 and the light receiving element groups 14 may be
arrayed with array patterns different from those shown in FIG. 2.
They may, for instance, be disposed in a square array pattern. In
addition, the micro-lenses 13 may assume the shape other than the
circular shape (e.g., a hexagonal shape). The light receiving
elements constituting the light receiving element groups 14 may be
disposed in a pattern other than the square array pattern. For
instance, light receiving elements may be disposed so that the
light receiving element groups 14 assume a shape better
approximating the circular shape of the micro-lenses 13, or light
receiving elements may be disposed in in a single lateral row or in
a single longitudinal column. Furthermore, the light-blocking mask
present between the micro-lenses 13 may be omitted.
[0116] (Variation 5)
[0117] Light receiving elements other than the three light
receiving elements at the left end and the three light receiving
elements at the right end of each light receiving element group
shown in FIG. 4(a) may be selected and used when generating a pair
of signal strings for purposes of focus detection. In addition, it
is not strictly necessary that sums of pixel values be calculated.
Namely, while the values a(1), a(2) and the like are each
calculated by adding up the light reception outputs from three
light receiving elements in the example presented in FIG. 4(a), the
light reception output from a single light receiving element may
instead be designated as a(1), a(2) or the like.
[0118] (Variation 6)
[0119] The current condition may be determined to be a false focus
match state if it is decided, through focus detection executed
after recognizing a pattern other than a cyclical pattern, that a
focus match has been achieved. It is because a uniform image is
bound to be formed on the rear side of a single micro-lens 13, as
illustrated in FIG. 5(c) in a true focus much state.
[0120] (Variation 7)
[0121] A cyclical pattern may be recognized through a method other
than the pattern matching method described earlier. For instance, a
cyclical pattern may be recognized by detecting, via a single light
receiving element group 14 covered by a given micro-lens 13, edges
that run along a specific direction (e.g., the lateral direction,
the longitudinal direction or a diagonal direction) in the light
reception outputs from the light receiving element group. The term
"edge" in this context refers to a point at which the light
reception outputs of two adjacent light receiving elements indicate
a significant change (exceeding a predetermined threshold value).
In this situation, the intervals between the edges that are
detected represent the pattern cycles.
[0122] In addition, a cyclical pattern may be recognized by
calculating the sums of outputs, each in correspondence to one of a
plurality of light receiving element groups 14, which, in turn, are
each covered by one of a plurality of micro-lenses 13 disposed
along a specific direction, and comparing the plurality of sums
thus calculated. When the photographic optical system is in a focus
match state, the rear surface of a given micro-lens 13 is uniformly
irradiated with light as shown in FIG. 5(c). This means that if the
subject image assumes a cyclical pattern, the difference between
the sums of the outputs from two light receiving element groups 14
set next to each other is bound to be large, as shown in FIG.
10(c). Namely, an edge can be detected based upon the sums of the
outputs from two adjacent light receiving element groups 14. In a
false focus much state, in contrast, a cyclical pattern is formed
on the rear surface of each micro-lens 13 and in such a case, the
difference between the sums of the outputs from two adjacent light
receiving element groups 14 is bound to be relatively small. Thus,
by adding up the light reception outputs from each light receiving
element group 14 and detecting edges through comparison of the sums
of the outputs each corresponding to a light receiving element
group 14, a cyclical pattern can be recognized.
[0123] (Variation 8)
[0124] The present invention may be adopted in a camera, widely
known as a single lens reflex camera, that includes a quick return
mirror. The quick return mirror in the single lens reflex camera
adopting the present invention should be configured by disposing a
sub mirror at the rear surface of a quick return mirror so as to
ensure that part of the subject light having entered the quick
return mirror is transmitted through the quick return mirror and
enters the sub mirror, and that the subject light reflected at the
sub mirror enters the focus detection unit 104. In addition, the
present invention may be adopted in conjunction with an image
sensor 102 configured with a micro-lens array 11 and a light
receiving element array 12, as is the focus detection unit 104, and
in such a case, focus detection and still image capturing may both
be executed via the light receiving element array 12 in the image
sensor 102.
[0125] (Variation 9)
[0126] The lens drive device 206 and the aperture drive device 207
may be disposed at the camera body 100 instead of at the
interchangeable lens 200. In such a configuration, the actuators
(not shown) in the lens drive device 206 and aperture drive device
207 will adopt structures that allow the drive forces imparted
thereby to be respectively transmitted to the focusing lens 203 and
the aperture 205 in the interchangeable lens 200 via drive
mechanisms (not shown).
[0127] As long as the features characterizing the present invention
are not compromised, the present invention is in no way limited to
the particulars of the embodiments described above, and other modes
that are conceivable within the technical scope of the present
invention are also within the scope of the invention.
[0128] The disclosures of the following priority applications are
herein incorporated by reference: [0129] Japanese Patent
Application No. 2012-100150 filed Apr. 25, 2012 [0130] Japanese
Patent Application No. 2012-158796 filed Jul. 17, 2012
EXPLANATION OF REFERENCE NUMERALS
[0131] 1 . . . camera, 100 . . . camera body, 101 . . . body
control device, 102 . . . image sensor, 103 . . . half mirror, 104
. . . focus detection unit, 106 . . . eyepiece lens, 108 . . .
electronic viewfinder unit, 110 . . . monitor, 200 . . .
interchangeable lens, 201 . . . lens control device, 202, 204 . . .
lens, 203 . . . focusing lens, 205 . . . aperture, 206 . . . lens
drive device, 207 . . . aperture drive device
* * * * *