Title: Focusing apparatus for adjusting focus of an optical instrument
Abstract: A focusing apparatus adjusting the focus of an optical apparatus includes an optical unit for forming a subject image, a contrast detecting unit for detecting contrast value of subject image acquired by the optical unit, a distance measuring unit for computing distance information indicating a distance to the subject, an adjustment command receiving unit for receiving command information indicating a request to adjust a focus of the optical unit, a focus control unit for performing contrast detection by hill-climbing method when the adjustment command receiving unit receives the command information, a difference information computing unit for computing difference information indicating a difference between a focusing position detected by the focus control unit, which performs the contrast detection by hill-climbing method, and an adjustment position of the optical unit corresponding to the distance information computed by the distance measuring unit, and a difference information storing unit for storing the difference information computed by the difference information computing unit, wherein the focus control unit determines a condition of the contrast detection by hill-climbing method on the basis of the difference information stored in the difference information storing unit and distance information.
Patent Number: 6,864,474 Issued on 03/08/2005 to Misawa
| Inventors:
|
Misawa; Atsushi (Saitama, JP)
|
| Assignee:
|
Fuji Photo Film Co., Ltd. (Kanagawa, JP)
|
| Appl. No.:
|
339331 |
| Filed:
|
January 10, 2003 |
Foreign Application Priority Data
| Feb 08, 2002[JP] | 2002-033157 |
| Current U.S. Class: |
250/201.4 |
| Intern'l Class: |
G02B 027//40 |
| Field of Search: |
250/201.2-201.8
|
References Cited [Referenced By]
U.S. Patent Documents
| 6473228 | Oct., 2002 | Toshimitsu | 359/368.
|
| Foreign Patent Documents |
| 10-293245 | Nov., 1998 | JP.
| |
Primary Examiner: Luu; Thanh X.
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A focusing apparatus for adjusting focus of an optical instrument
comprising:
an optical unit for acquiring light from a subject and forming a subject
image;
a contrast detecting unit for detecting contrast value of the subject image
acquired by said optical unit;
a distance measuring unit for computing distance information indicating a
distance from the focusing apparatus to the subject;
an adjustment command receiving unit for receiving command information
indicating a request to adjust the focus of said optical unit;
a focus control unit for performing contrast detection by hill-climbing
method by acquiring a contrast value step-by-step by moving at least a
part of said optical unit step-by-step, and detecting a position of said
optical unit, where the acquired contrast value becomes a maximum value,
as a focusing position, when said adjustment command receiving unit
receives the command information, said focus control unit determining an
adjustment range of said optical unit, which performs the contrast
detection by hill-climbing method, on the basis of the difference
information stored in said difference information storing unit and the
distance information newly computed by said distance measuring unit;
a difference information computing unit for computing difference
information indicating the difference between the focusing position
detected by said focus control unit, which performs the contrast detection
by hill-climbing method, and an adjustment position of said optical unit
corresponding to the distance information computed by said distance
measuring unit; and
a difference information storing unit for storing the difference
information computed by said difference information computing unit,
wherein said distance measuring unit newly computes distance information
when said adjustment command receiving unit receives new command
information, and
said focus control unit determines a condition for the contrast detection
by hill-climbing method on the basis of the difference information stored
in said difference information storing unit and distance information newly
computed by said distance measuring unit.
2. A focusing apparatus as claimed in claim 1, wherein said focus control
unit determines width of said adjustment range of said optical unit.
3. A focusing apparatus as claimed in claim 1, wherein said focus control
unit determines a center of said adjustment range of said optical unit.
4. A focusing apparatus according to claim 1, wherein the focus control
unit widens the adjustment range of the optical unit when the difference
information is large.
5. A focusing apparatus according to claim 1, wherein the focus control
unit narrows the adjustment range of the optical unit when the difference
information is small.
Description
The present application claims priority from a Japanese Patent Application
No. 2002-033157 filed on Feb. 8, 2002, the contents of which are enclosed
herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a focusing apparatus. More particularly,
the present invention relates to a focusing apparatus for adjusting focus
of optical instrument.
2. Description of the Related Art
Japanese Laid-Open Patent Application No. 10-293245 discloses an electronic
camera which performs supplemental focusing with contrast focus control
means after performing focusing with a focus control means by external
metering.
However, according to the above described conventional electronic camera,
the contrast focus control means performs contrast detection by
hill-climbing method, where the contrast focus control means measures
contrast value from solid state image pick-up device like a CCD or a CMOS
image sensor and finds out a focusing position on which the contrast value
becomes a maximum value by gradually pushing out the optical unit. Since
the contrast focus control means needs to move the optical unit for
several times intermittently to perform the contrast detection by
hill-climbing method, there is a problem that it takes time for the
optical unit to reach the focusing position.
Therefore, it is an object of the present invention to provide a focusing
apparatus, which is capable of overcoming the above drawbacks accompanying
the conventional art. The above and other objects can be achieved by
combinations described in the independent claims. The dependent claims
define further advantageous and exemplary combinations of the present
invention.
According to the first aspect of the present invention, a focusing
apparatus for adjusting focus of an optical instrument including: an
optical unit for acquiring light from a subject and forming a subject
image; a contrast detecting unit for detecting contrast value of the
subject image acquired by the optical unit; a distance measuring unit for
computing distance information indicating a distance from the focusing
apparatus to the subject; an adjustment command receiving unit for
receiving command information indicating a request to adjust the focus of
the optical unit; a focus control unit for performing contrast detection
by hill-climbing method by acquiring a contrast value step-by-step by
moving at least a part of the optical unit step-by-step, and detecting a
position of the optical unit, where the acquired contrast value becomes a
maximum values, as a focusing position, when the adjustment command
receiving unit receives the command information; a difference information
computing unit for computing difference information indicating the
difference between the focusing position detected by the focus control
unit, which performs the contrast detection by hill-climbing method, and
an adjustment position of the optical unit corresponding to the distance
information computed by the distance measuring unit; and a difference
information storing unit for storing the difference information computed
by the difference information computing unit, wherein the distance
measuring unit newly computes distance information when the adjustment
command receiving unit receives command information later, and the focus
control unit determines a condition for the contrast detection by
hill-climbing method on the basis of the difference information stored in
the difference information storing unit and distance information newly
computed by the distance measuring unit.
The focus control unit may determine width of an adjustment range of the
optical unit, which performs the contrast detection by hill-climbing
method, on the basis of the difference information stored in the
difference information storing unit and the distance information newly
computed by the distance measuring unit. Moreover, the focus control unit
may determine a center of an adjustment range of the optical unit, which
performs the contrast detection by hill-climbing method, on the basis of
the difference information stored in the difference information storing
unit and the distance information newly computed by the distance measuring
unit.
The summary of the invention does not necessarily describe all necessary
features of the present invention. The present invention may also be a
sub-combination of the features described above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a functional structure of an image capturing apparatus 10.
FIG. 2 shows a table stored in a difference information storing unit 150.
FIG. 3 shows a flowchart illustrating operation of the image capturing
apparatus 10 according to an embodiment of the present invention.
FIG. 4 shows a structure of a digital camera 12 equipped with the image
capturing apparatus 10.
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described based on the preferred embodiments,
which do not intend to limit the scope of the present invention, but
exemplify the invention. All of the features and the combinations thereof
described in the embodiment are not necessarily essential to the
invention. In addition, a "image capturing apparatus" used in the detailed
description of this specification is an example of "focusing apparatus"
described in the appended claims.
FIG. 1 shows an example of a characteristic functional structure of an
image capturing apparatus 10 of an embodiment of the present invention.
The image capturing apparatus 10 according to the present embodiment
adjusts a focus of an optical unit on the basis of contrast value of a
subject image and distance information indicating distance from the image
capturing apparatus 10 to the subject. The image capturing apparatus 10
performs the contrast detection by hill-climbing method where contrast
value is acquired step by step by moving at least a part of the optical
unit step by step, and a position, on which the acquired contrast value
becomes a maximum value, is detected as a focusing position.
The image capturing apparatus 10 includes a difference information storing
unit 150, an optical unit 160, an adjustment command receiving unit 170, a
focus control unit 180, a distance measuring unit 190, a difference
information computing unit 200 and a contrast detecting unit 210.
The difference information storing unit 150 stores difference information
indicating difference between a position, which corresponds to distance
information, of the optical unit 160 and the focusing position, and the
difference information corresponds to focusing position information
indicating focusing position of the optical unit 160. The optical unit 160
forms a subject image by acquiring lights from the subject. The optical
unit 160 includes a plurality of lenses. The adjustment command receiving
unit 170 receives command information indicating a command for adjusting
the focusing position of the subject image formed by the optical unit 160.
The adjustment command receiving unit 170 sends the received command
information to the focus control unit 180.
If the focus control unit 180 receives command information from the
adjustment command receiving unit 170, the focus control unit 180 sends
distance computation requesting information indicating a request for
computing distance to the subject from the image capturing apparatus 10 to
the distance measuring unit 190. If the distance measuring unit 190
receives the distance computation requesting information from the focus
control unit 180, the distance measuring unit 190 produces distance
information indicating the distance to the subject from the image
capturing apparatus 10, and sends the distance information to the focus
control unit 180. Further, the distance measuring unit 190 sends the
distance information to the difference information computing unit 200.
The focus control unit 180 receives the distance information from the
distance measuring unit 190. Then, the focus control unit 180 computes an
adjustment position, which is a position of a lens of the optical unit 160
and is corresponding to the received distance information. Then, the focus
control unit 180 reads out difference information stored with
correspondence to the focusing position which is the closest to the
adjustment position from the difference information storing unit 150. The
focus control unit 180 determines a central position of an adjustment
range of the optical unit 160 which performs the contrast detection by
hill-climbing method on the basis of new distance information computed by
the distance measuring unit 190 and difference information readout from
the difference information storing unit 150. Concretely, the focus control
unit 180 determines a position of the lens of the optical unit 160, which
can be obtained by adding difference information to the adjustment
position, as the center position of the adjustment range of the optical
unit 160.
Moreover, the focus control unit 180 determines adjustment range of the
optical unit 160 which performs the contrast detection by hill-climbing
method on the basis of difference information read out form the difference
information storing unit 150. For example, if the difference indicated by
the difference information is large, the focus control unit 180 widens the
adjustment range of the optical unit 160. Moreover, if the difference
indicated by difference information is small, the focus control unit 160
may narrow the adjustment range of the optical unit 160. The focus control
unit 180 performs the contrast detection by hill-climbing method within
the determined adjustment range of the optical unit 160.
Then, the focus control unit 180 moves the lens of the optical unit 160 to
a position where the contrast value becomes a maximum value. The focus
control unit 180 sends difference requesting information indicating a
request for computing new difference information and focusing position
information indicating the focusing position on which the contrast value
detected by the contrast detecting unit 210 becomes a maximum value to the
difference information computing unit 200. The difference information
computing unit 200 receives the difference requesting information and the
focusing position information from the focus control unit 180. Then, the
difference information computing unit 200 receives distance information
from the distance measuring unit 190. Then, the difference information
computing unit 200 computes the adjustment position from received distance
information. The difference information computing unit 200 computes
difference information indicating the difference between the focusing
position and the adjustment position. The difference information computing
unit 200 stores newly computed new difference information as difference
information. Moreover, the difference information computing unit 200
stores the focusing position information corresponding to the new
difference information.
FIG. 2 shows a table stored in the difference information storing unit 150.
The difference information storing unit 150 includes a record number
field, a difference field, and a focusing position field. The record
number field stores numbers each of which identifies a record of a
difference. The difference field stores difference between the focusing
position of the optical unit 160 detected by hill-climbing method, where
the contrast value becomes a maximum value, and the position of the
optical unit 160 corresponding to distance information computed by the
distance measuring unit 190. The difference field stores difference
information computed by the difference information computing unit 200. The
focusing position field stores the focusing position of the optical unit
160 which is detected by performing the contrast detection by
hill-climbing method with the focus control unit 180. Here, each value
stored in the difference field and the focusing position field is, for
example, in a range of 1 to 100, where each of the values indicates a
position of the lens of the optical unit 160 when each possible position
of the lens of optical unit 160 is designated as one of total 100
positions.
FIG. 3 is a flowchart illustrating operation of the image capturing
apparatus 10 according to an embodiment of the present invention. The
adjustment command receiving unit 170 receives the adjustment command
information (step S102). Then, the distance measuring unit 190 computes
new distance information indicating a distance from the image capturing
apparatus 10 to the subject (step S104). Then, the focus control unit 180
computes an adjustment position which is a position of the optical unit
160 corresponding to the distance information. The focus control unit 180
reads out difference information stored with correspondence to the
focusing position, which is the closest to the adjustment position, from
the difference information storing unit 150 (step S106).
Then, the focus control unit 180 determines a center of an adjustment range
of the optical unit 160 which performs contrast detection by hill-climbing
method on the basis of the new distance information computed by the
distance measuring unit 190 and the difference information read out from
the difference information storing unit 150 (step S108). Then, the focus
control unit 180 determines the adjustment range of the optical unit 160
which performs contrast detection by hill-climbing method on the basis of
difference information read out from the difference information storing
unit 150 (step S110). Then, the focus control unit 180 acquires contrast
value step-by-step by moving the optical unit 160 step-by-step, and
detects the position, where the acquired contrast value becomes a maximum
value, of the optical unit 160 as the focusing position (step S112).
Then, the focus control unit 180 adjusts the optical unit 160 to a position
where the contrast value becomes a maximum value (step S114). Then, the
difference information computing unit 200 newly computes difference
information indicating a difference between the focusing position of the
optical unit 160 corresponding to the contrast value newly detected by the
contrast detecting unit 210 and the adjustment position of the optical
unit 160 corresponding to the distance to the subject computed by the
distance measuring unit 190. The difference information computing unit 200
stores in the difference information storing unit 150 the computed
difference information corresponding to the focusing position information
indicating the focusing position of the optical unit 160 (step S116).
Like this, the image capturing apparatus 10 may determine a proper range
for performing the contrast detection by hill-climbing method by adding
difference information indicating the past difference to the adjustment
position. Therefore, the image capturing apparatus 10 may minimize the
required time to adjust focus of the optical unit 160 by performing the
contrast detection by hill-climbing method within the proper range.
FIG. 4 is a block diagram showing an example of a configuration of the
digital camera 12 according to the present embodiment. The digital camera
12 is an example of the image capturing apparatus 10 according to the
present embodiment. The digital camera 12 includes the image pick-up unit
20, an image pick-up control unit 40, a system control unit 60, a
displaying unit 100, a control unit 110, the storing unit 120, an external
connection unit 130 and the image processing unit 140.
The image pick-up unit 20 includes an optical unit 22, a diaphragm 24, a
shutter 26, optical LPF 28 (low pass filter), the CCD 30 (charge-coupled
device), the pick-up signal processing unit 32, a finder 34, and the
electric flash 36.
The optical unit 22 takes and processes a subject image. The optical unit
22 includes a focal lens, a zoom lens, etc., and forms the image of the
subject onto surface of the CCD 30. The diaphragm 24 limits the light
which passes the optical unit 22, and the optical LPF 28 passes light
having longer wavelength component than a predetermined wavelength. Each
of the sensor elements included in the CCD 30 stores charge according to
quantity of light of the formed subject image (the charge is referred to
as "stored charge" hereinafter).
The shutter 26 is a mechanical shutter and controls whether to form the
image of the light onto the CCD 30, the light passing the optical unit 22.
The digital camera 12 may include an electronic shutter function instead
of the mechanical shutter 26. In order to realize the electronic shutter
function, each of the sensor elements of the CCD 30 has a shutter gate and
a shutter drain. The stored charge is discharged to the shutter drain by
turning on the shutter gate. Duration of storing the charge to each of the
sensor elements, i.e., shutter speed, is controllable by controlling the
shutter gate. In the CCD 30, the stored charge is read by a shift register
by applying a readout gate pulse, and is read sequentially as a voltage
signal by applying the register transfer pulse.
The pick-up signal processing unit 32 separates the voltage signal
indicating the subject image outputted from the CCD 30, i.e., an analog
signal, into R, G, and B components. The pick-up signal processing unit 32
adjusts white balance of the subject image by adjusting R, G, and B
components. The pick-up signal processing unit 32 performs gamma
correction of the subject image. The pick-up signal processing unit 32
converts the analog signal, which is separated into R, G, and B
components, to a digital signal, and image data of the digital signal of
the subject image (referred to as "digital image data" hereinafter),
obtained by the A/D conversion, is outputted to the system control unit
60.
The finder 34 may have a displaying means and may display various
information from below-mentioned main CPU 62, etc. The electric flash 36
includes a discharge tube 37, which discharges energy stored in a
capacitor, and when the energy is supplied to the discharge tube 37, the
electric flash 36 functions by the discharge tube 37 emitting light.
The image pick-up control unit 40 includes a lens drive unit 42, a focal
drive unit 44, a diaphragm drive unit 46, a shutter drive unit 48, an
image pick-up system CPU 50 which controls the drive units above, a
focusing sensor 52, and the photometry sensor 54. The lens drive unit 42,
the focal drive unit 44, the diaphragm drive unit 46, and the shutter
drive unit 48 include driving means, such as a stepping motor, and drive
mechanical components in the image pick-up unit 20. According to
depression of the release switch 114, the focusing sensor 52 measures
distance to the subject, and the photometry sensor 54 measures brightness
of the subject. The focusing sensor 52 and the photometry sensor 54 supply
focusing data and photometry data to the image pick-up system CPU 50,
where the focusing data means the data of the measured distance to the
subject, and the photometry data means the data of the measured brightness
of the subject.
The image pick-up system CPU 50 controls the lens drive unit 42 and the
focal drive unit 44, and adjusts a zoom magnification and a focus of the
optical unit 22 based on photography information, such as a zoom
magnification directed by a user. Alternatively, the image pick-up system
CPU 50 may control the lens drive unit 42 and the focal drive unit 44, and
may adjust a zoom magnification and a focus based on the focusing data
received from the focusing sensor 52.
The image pick-up system CPU 50 determines stop and shutter speed based on
the photometry data received from the photometry sensor 54. The diaphragm
drive unit 46 and the shutter drive unit 48 control the aperture size of
the diaphragm 24, and the opening and closing of the shutter 26 in
accordance with the determined value.
The image pick-up system CPU 50 controls light emission of the electric
flash 36 based on the photometry data received from the photometry sensor
54, and adjusts the aperture size of the diaphragm 26 simultaneously. When
the user instructs to take an image, the CCD 30 starts to store the charge
and outputs the stored charge to the pick-up signal processing unit 32
after the shutter time calculated from the photometry data is elapsed.
The system control unit 60 includes main CPU 62, a character generating
unit 84, a timer 86, and a clock generating unit 88. The main CPU 62
controls whole parts of the digital camera 12, especially the system
control unit 60. The main CPU 62 sends and receives required information
to/from the image pick-up systems CPU 50 by serial communication or the
like.
The clock generating unit 88 generates an internal clock of the main CPU
62, and supplies it to the main CPU 62. The clock generating unit 88 also
generates internal clocks of the image pick-up system CPU 50 and the
displaying unit 100. The clock generating unit 88 may supply the clocks
having different frequencies to the main CPU 62, the image pick-up system
CPU 50, and the displaying unit 100, respectively.
The character generating unit 84 generates text and graphic information,
which is superimposed onto the captured image, such as date/time or a
title of the image. A timer 86 has backing of battery etc., counts time
always, and supplies time information, such as information about the
captured date/time of the captured image, to the main CPU 62 based on the
counted value. It is preferable that the power is supplied to the timer 86
from the battery so as to count time even when main power supply of the
digital camera is switched off. It is also preferable that the character
generating unit 84 and the timer 86 are annexed to the main CPU 62.
The storing unit 120 includes a memory control unit 64, nonvolatile memory
66, and main memory 68. The memory control unit 64 controls the
nonvolatile memory 66 and the main memory 68. The nonvolatile memory 66 is
composed of EEPROM (electrically erasable programmable read only memory)
or flash memories etc., and stores it with data which is to be held even
when the power supply of the digital camera 12 is switched off, such as
setting information set by a user or a factory preset value. The
nonvolatile memory 66 may store a boot program, a system program, etc. of
the main CPU 62.
It is preferable that the main memory 68 is composed of memory which is
relatively inexpensive and has large capacity, like DRAM. The main memory
68 has a function as frame memory to store the data outputted from the
image pick-up unit 20, a function as system memory which loads various
programs, and a function as a work area. The nonvolatile memory 66 and the
main memory 68 communicate with each part inside/outside the system
control unit 60 through a bus 82. The nonvolatile memory 66 may further
store the digital image data.
The image processing unit 140 includes an YC processing unit 70, an encoder
72, and a compression/decompression processing unit 78. The external
connection unit 130 includes an optional equipment control unit 74 and a
communication interface 80.
The YC processing unit 70 performs YC conversion to the digital image data,
and generates a luminance signal Y, a color difference signals B-Y and
R-Y. The main memory 68 stores the luminance signal and the color
difference signals based on control of the memory control unit 64.
The compression/decompression processing unit 78 reads the luminance signal
and the color difference signals sequentially from the main memory 68, and
compresses them. Then the optional equipment control unit 74 writes the
compressed digital image data (referred to as "compressed data") in a
memory card which is an example of the optional equipment 76.
The encoder 72 converts the luminance signal and the color difference
signals into a video signal (such as NTSC or PAL signal), and outputs the
video signal from a terminal 90. When generating the video signal from the
compressed data recorded on the optional equipment 76, the compressed data
is supplied to the compression/decompression processing unit 78 at first
through the optional equipment control unit 74. Then, the data is
decompressed in the compression/decompression processing unit 78 and the
encoder 72 converts the decompressed data into the video signal.
The optional equipment control unit 74 performs generation, logical
conversion, and/or voltage conversion of the signal that flows between the
bus 82 and the optional equipment 76, in order to conform the signal to
the specification of the optional equipment 76 and the bus 82. Other than
the above-mentioned memory card, the digital camera 12 may support a
standard PCMCIA I/O card, for example, as the optional equipment 76. In
this case, the optional equipment control unit 74 may be composed of bus
control LSI for PCMCIA standard or the like.
The communication interface 80 performs control such as protocol conversion
to comply with the communication specification supported by the digital
camera 12, e.g., USB, RS-232C, Ethernet, etc. The communication interface
80 may output the compressed data or the digital image data to external
equipment or to a network through a terminal 92. The communication
interface 80 includes a driver IC if necessary and communicates with
external equipment through the terminal 92. The communication interface 80
may be adapted to communicate with the external equipment, such as a
printer, a Karaoke machine or a video game machine, through an original
standard interface.
The displaying unit 100 includes an LCD display 102, an LCD panel 104, a
display driver 106, and a panel driver 108. The display driver 106
controls the LCD display 102. The panel driver 108 controls the LCD panel
104. The LCD display 102 is positioned on the back face of the camera, of
which the size is about 2 inches for example, and displays an image
currently captured, a playback image, zoom magnification of the captured
or playback image, remaining battery charge, date/time, mode selection
screen, a subject image, etc. The LCD panel 104 is a monochrome LCD, for
example, is positioned on top face of the camera, and displays
information, such as quality of the image (fine, normal, basic, etc.),
flash mode (forced flash, suppressed flash, etc), number of available
frames, number of pixels, and remaining battery charge.
The control unit 110 includes a power switch 112, the release switch 114, a
function setting unit 116, and a zoom switch 118. The power switch 112
switches the digital camera 12 on and off based on direction of a user.
The release switch 114 can be depressed in two levels, i.e., halfway
depression and full depression. For example, when the release switch 114
is depressed halfway, the image pick-up control unit 40 performs automatic
focusing and automatic exposure, and the image pick-up unit 20 captures a
subject image by depressing the release switch 114 fully. The release
switch 114 sends command information to request the image pick-up system
CPU to adjust the focus position when the release switch 114 is depressed
halfway.
The function setting unit 116 is, for example, a rotatable mode dial or a
4-direction button and accepts settings such as "file format", "special
effect", "print", "determine/save", "change display", etc. The zoom switch
118 accepts setting of zoom magnification of the subject image captured by
the image pick-up unit 20.
The digital camera 12 having the above-mentioned structure operates in the
following manner. First, the power switch 112 is depressed and power is
supplied to each part of the digital camera 12. The main CPU 62 judges
whether the digital camera 12 is in photography mode or in playback mode
by reading status of the function setting unit 116.
When a digital camera 12 is in photography mode, the main CPU 62 supervises
the depression status of the release switch 114. When the half-depression
of the release switch 114 is detected, the image pick-up system CPU 50
acquires photometry data and focusing data from the photometry sensor 54
and the focusing sensor 52, respectively. The image pick-up control unit
40 adjusts focus and stop of the image pick-up unit 20, etc. based on the
photometry data and the focusing data acquired by the image pick-up system
CPU 50. After the adjustment, the LCD display 102 informs a user about the
completion of the adjustment by displaying characters, such as "standby".
Then, the main CPU 62 supervises the depression status of the release
switch 114. When the full-depression of the release switch 114 is
detected, the shutter 26 is closed after a predetermined shutter time is
elapsed and the stored charge of the CCD 30 is discharged to the pick-up
signal processing unit 32. The digital image data, generated as a result
of processing by the pick-up signal processing unit 32, is outputted to
the bus 82. The digital image data is once stored in the main memory 68,
then it is processed in the YC processing unit 70 and the
compression/decompression processing unit 78, and is recorded in the
optional equipment 76 via the optional equipment control unit 74. The
captured image based on the recorded digital image data is displayed on
the LCD display 102 for a while, so that a user can check the captured
image. As described above, a sequence of the photographing operation is
finished.
On the other hand, when the digital camera 12 is in playback mode, the main
CPU 62 reads the captured image from the main memory 68, the nonvolatile
memory 66, and/or the optional equipment 76, and displays the image on the
LCD display 102 of the displaying unit 100.
In this state, when a user directs either "move forward" or "move backward"
on the function setting unit 116, the main CPU 62 reads another captured
image stored in the main memory 68, the nonvolatile memory 66, and/or the
optional equipment 76, and displays the image on the LCD display 102 of
the displaying unit 100.
In addition, function of the optical unit 22 shown in FIG. 4 is
corresponding to that of the optical unit 160 shown in FIG. 1. The CCD 30
and the pick-up signal processing unit 32 shown in FIG. 4 is corresponding
to the contrast detecting unit 210 shown in FIG. 1. Function of the
distance measuring sensor 52 shown in FIG. 4 is corresponding to that of
the distance measuring unit 190 shown in FIG. 1. Function of the image
pick-up system CPU 50 shown in FIG. 4 is corresponding to that of the
focus control unit 180 and the difference information computing unit 200
shown in FIG. 1. The main memory 68 shown in FIG. 4 is corresponding to
the difference information storing unit 150 shown in FIG. 1. The release
switch 114 shown in FIG. 4 is corresponding to the adjustment command
receiving unit 170 shown in FIG. 1.
Now, a modified embodiment of the present embodiment is described in
detail. The image capturing apparatus 10 according to the present
embodiment determines the adjustment range of the optical unit 160 and the
center of the adjustment range by using difference information
corresponding to the focusing position, which is the closest to the
adjustment position. However, instead of that, according to the modified
embodiment, the adjustment range of the optical unit 160 and the center of
the adjustment range may be determined by using an average value of a
plurality of difference information. By using the average value of the
plurality of difference information, the focus control unit 180 can
minimize the gap due to errors which occur while the distance measuring
unit 190 computes distance information or the focus control unit 180
performs the contrast detection by hill-climbing method.
Moreover, the image capturing apparatus 10 according to the present
embodiment determines the adjustment range of optical unit 160 and the
center of adjustment range by using difference information corresponding
to the focusing position, which is the closest to the adjustment position.
However, instead of that, according to the modified embodiment, the
difference information storing unit 150 may store one difference
information. In this case, the difference information computing unit 200
updates difference information stored in the difference information
storing unit 150 with newly computed difference information. The focus
control unit 180 determines the adjustment range of optical unit 160 by
using the newest difference information.
Moreover, in case difference indicated by difference information stored in
the difference information storing unit 150 is within a predetermined
range, the focus control unit 180 may narrow the adjustment range of
optical unit 160.
Moreover, the image capturing apparatus 10 according to the present
embodiment stores difference information in the difference information
storing unit 150 corresponding to the focusing position. However, instead
of that, according to the modified embodiment, the difference information
may be corresponding to distance information and stored in the difference
information storing unit 150. In this case, the focus control unit 180
reads out difference information corresponding to the distance
information, which is the closest to new distance information, from the
difference information storing unit 150.
As apparent from the above description, according to the present invention,
it is possible to perform a contrast detection by hill-climbing method in
a proper range.
Although the present invention has been described by way of exemplary
embodiments, it should be understood that those skilled in the art might
make many changes and substitutions without departing from the spirit and
the scope of the present invention which is defined only by the appended
claims.
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