Digital Camera Patent AbstractThe present invention provides a digital camera which can adjust
the start-up time in accordance with an amount of an electric energy
of a power source being used at the time. The electric energy of
the power source and the type thereof are determined on the basis
of a voltage value of the power source which is inputted via a bus
(steps 202, 206 and 218). If it is determined that the amount of
the electric energy of the power source is large, the DC motor and
the stepping motor are driven simultaneously so as to reduce the
start-up time. If it is determined that the amount of the electric
energy of the power source is small, the DC motor and the stepping
motor are sequentially driven to save the electric energy.
Digital Camera Patent ClaimsWhat is claimed is:
1. A digital camera comprising: (a) a housing having a lens barrel
movable along an optical axis; (b) a zoom lens group and a focus
lens group movable relative to one another along the optical axis
in the lens barrel; (c) a zoom motor connected to the lens barrel
operable for moving the lens barrel to a position corresponding
to a selected magnification; (d) a focus motor connected to the
focus lens group operable for moving the focus lens group to a focus
position corresponding to the selected magnification; (e) a lens
cover movable between closed and open positions for protecting at
least one lens, and a lens cover driving motor connected to the
lens cover, operable for moving the lens cover between closed and
open positions; (f) an electric power source; (g) a controller connected
to the electric power source and controlling the zoom motor and
the focus motor, the controller determining during power initiation
whether an amount of voltage decrease from the electric power source
terminal voltage value caused by an operation of one of the lens
cover driving motor and the zoom motor is less than a predetermined
decrease amount value, and if so, controlling the zoom motor and
the focus motor to substantially overlap in operation to move the
lens groups to initialization positions; and (h) an image sensor
supported in the housing for receiving light through the lens groups,
and operable for producing data in correspondence with light received
through the lens groups for image recording, wherein the amount
of voltage decrease corresponds with a difference voltage between
a first power source voltage level at a start of power initiation
and a second power source voltage level during power initiation.
2. The digital camera according to claim 1, wherein if said voltage
decrease is greater than the predetermined value, said controller
drives one of said zoom motor and said focus motor to move one of
said zoom lens group and said focus lens group to an initialization
position, and then drives the other motor to move the other lens
group to an initialization position.
3. The digital camera according to claim 2, wherein when said voltage
decrease is greater than the predetermined value, said controller
drives said zoom motor to move said zoom lens group to an initialization
position, and then drives said focus motor to move said focus lens
group to an initialization position.
4. The digital camera according to claim 1, wherein said controller
includes a clock, the controller determining electric energy availability
of the power source on the basis of at least one of a power source
voltage value during power initiation and the voltage decrease when
one of the lens cover driving motor and said zoom motor is driven,
and when the electric energy energy availability is less than a
predetermined amount, sets a lower clock frequency for the clock.
5. A method for activating a digital camera having a zoom and focus
lens group respectively driven by a zoom and focus motor, a lens
cover driven by a lens cover driving motor, and a power source,
the method comprising: (a) determining a power source voltage available
upon power initiation prior to driving any of the motors; (b) operating
at least one of the lens cover driving motor and the zoom motor
during power initiation, and determining an amount of power source
voltage decrease from a terminal voltage value caused by the operation;
and (c) substantially overlapping operation of the zoom and focus
motors to drive the zoom and focus lens group to initialization
positions if the amount of power source voltage decrease is less
than a predetermined decrease amount value, wherein the amount of
power source voltage decrease corresponds with a difference voltage
between a first power source voltage level at a start of power initiation
and a second power source voltage level during power initiation.
6. The method of claim 5, further comprising operating one of said
zoom motor and said focus motor so as to move one of said lens groups
to an initialization position when said power source voltage decrease
is greater than a predetermined value, and then operating the other
motor so as to move the other lens group to an initialization position.
7. The method of claim 6, wherein said zoom motor is operated so
as to move said zoom lens group to an initialization position when
said power source voltage decreases is larger than the predetermined
value, and then operating said focus motor so as to move said focus
lens group to an initialization position.
8. The method of claim 6, wherein the digital camera includes a
clock, further comprising: determining an amount of electric energy
available from the power source on the basis of at least one of
a power source voltage value upon power initiation and the power
source voltage decrease; and setting a lower frequency for the clock
in the amount of electric energy determined to be available is less
than a predetermined amount.
9. The method of claim 5, further comprising ceasing operation
of said focus motor when said power source voltage is less than
a predetermined value when said zoom motor and said focus motor
are being operated simultaneously.
10. The method of claim 5, further comprising: determining whether
the power source is connected to an alternating power source upon
power initiation; and substantially overlapping operation of said
zoom motor and said focus motor so as to move said zoom lens group
and said focus lens group to initialization positions if the power
source is connected to an alternative power source.
11. The method of claim 10, wherein determining whether the power
source is connected to an alternating power source is determined
on the basis of the power source voltage available upon power initiation
and the amount of power source voltage decrease when one of said
lens cover driving motor and said zoom motor is driven.
12. The method of claim 10, wherein the power source is determined
to be connected to the alternating power source if the power source
voltage is at least 2.9 V.
13. The method of claim 10, wherein the digital camera includes
a clock, further comprising: determining an amount of electric energy
available from the power source on the basis of at least one of
a power source voltage value upon power initiation and the power
source voltage decrease; and setting a lower frequency for the clock
if the amount of electric energy determined to be available is less
than a predetermined amount.
14. The method of claim 5, wherein the digital camera includes
a clock, further comprising: determining an amount of electric energy
available from the power source on the basis of at least one of
a power source voltage value upon power initiation and the power
source voltage decrease; and setting a lower frequency for the clock
if the amount of electric energy determined to be available is less
than a predetermined amount. Digital Camera Patent DescriptionBACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a digital camera, and in particular,
to a digital camera with a zoom lens.
2. Description of the Related Art
In general, a zoom lens of a zoom digital camera is formed with
a plurality of lens groups. When a power source is turned off, the
plurality of lens groups are accommodated all together within a
lens barrel which is retracted within a housing of the digital camera.
When the power source is turned on, a zoom motor is driven to extend
the lens barrel to a predetermined reference position, and the zoom
lens is set to be near to a wide position. Then, a focus lens in
the zoom lens is moved to a focusing position within a space formed
within the housing due to extension of the lens barrel, such that
the digital camera is in a stand-by state in which photographing
is possible.
Recently, there has been needed a digital camera in which the time
from when the power source is turned on and a lens cover is opened
by a motor to the time when the digital camera is in a state in
which photographing is possible (which time is referred to as a
startup time hereinafter) is short.
In order to make the start-up time shorter, at a time of start-up
processing, it is effective for the extension of the lens barrel
and movement of the focus lens to be carried out simultaneously.
In order to carry out the extension of the lens barrel and the movement
of the focus lens simultaneously, however, it is necessary to drive
a zoom motor which extends the lens barrel and a focus motor which
moves the focus lens simultaneously, and thus a large amount of
electric energy is needed at a time of start-up processing.
As a result, when a weak battery or a battery with a small amount
of charge is used as a power source, although there is sufficient
electric energy for photographing, the electric energy is insufficient
at a time of start-up processing. As a result, the start-up processing
cannot be carried out and photographing becomes difficult.
SUMMARY OF THE INVENTION
With the aforementioned in view, an object of the present invention
is to provide a digital camera which can adjust the start-up time
in accordance with an amount of electric energy of a power source
which is being used at the time.
In order to accomplish the above-described object, in accordance
with a first aspect of the present invention, there is provided
a digital camera comprising: (a) a housing having a lens barrel
movable along an optical axis; (b) a zoom lens group and a focus
lens group movable relative to one another along the optical axis
in the lens barrel; (c) a zoom motor connected to the lens barrel
operable for moving the lens barrel to a position corresponding
to a selected magnification; (d) a focus motor connected to the
focus lens group operable for moving the focus lens group to a focus
position corresponding to the selected magnification; (e) a lens
cover movable between closed and open positions for protecting at
least one lens, and a lens cover driving motor connected to the
lens cover, operable for moving the lens cover between closed and
open positions; (f) an electric power source; (g) a controller connected
to the electric power source and controlling the zoom motor and
the focus motor, the controller determining during power initiation
whether a voltage decrease from the electric power source during
operation of one of the lens cover driving motor and the zoom motor
is less than a predetermined value, and if so, controlling the zoom
motor and the focus motor to substantially overlap in operation
to move the lens groups to initialization positions; and (h) an
image sensor supported in the housing for receiving light through
the lens groups, and operable for producing data in correspondence
with light received through the lens groups for image recording.
In accordance with the first aspect of the present invention, at
a time of initialization, on the basis of the amount by which voltage
decreases when either a lens cover driving motor or a zoom motor
is driven, driving of the zoom motor and the focus motor is controlled.
That is, when the amount by which the voltage decreases is smaller
than a predetermined value, a power source with a large electric
energy is used, thus the drive controller drives the zoom motor
and the focus motor simultaneously. Therefore, the start-up time
which is the time from when a lens cover is opened until a digital
camera is in a state in which photographing is possible can be reduced.
When the zoom motor and the focus motor are driven simultaneously,
for example, the zoom motor is driven stepwise such that the zoom
lens group moves stepwise every fixed period of time or every fixed
period. Further, the focus motor can be driven such that the focus
lens group moves stepwise following the movement of the zoom lens
group.
In a case of a digital camera in which a lens cover is opened/closed
by the lens cover driving motor, the amount by which the voltage
decreases is the same amount by which the voltage decreases when
either the lens cover driving motor or the zoom motor is driven.
In a case of a digital camera with which the lens cover driving
motor is not provided and in which a lens cover is manually opened
or closed, the amount by which the voltage decreases is the amount
by which the voltage decreases when the zoom motor is driven.
"Simultaneous driving of the zoom motor and the focus motor"
described herein is not limited to a state in which both the zoom
motor and the focus motor are simultaneously driven (i.e., both
are started at the same time and stopped at the same time) and includes
at least a state in which the zoom motor and the focus motor are
driven simultaneously. For example, there may be included a case
in which the driving of focus motor is started after a constant
period of time has passed since the driving of zoom motor is started,
a case in which the driving of the zoom motor starts after a constant
period of time passes since the driving of focus motor starts and
a case in which during driving of the zoom motor and the focus motor,
either the zoom motor or the focus motor is stopped temporarily
and after a fixed period of time passes, the driving of the stopped
one is started again.
When the amount by which the voltage decreases is larger than a
predetermined value, since a power source with less electric energy
is being used, in a second aspect of the present invention, the
controller drives one of the zoom motor and the focus motor to move
one of the zoom lens group and the focus lens group to an initialization
position, and then drives the other motor to move the other lens
group to an initialization position.
That is, when a power source having little electric energy is used,
since a large amount of electric power cannot be supplied at one
time, either the zoom motor or the focus motor is driven. Thus a
large amount of electric power needs not be supplied at one time
and it is possible to prevent photographing from becoming difficult
due to a decrease in the electric power. There is no waste of a
battery such as a case in which although the electric power is sufficient
for photographing, it is insufficient for driving the zoom lens
such that photographing becomes difficult and the battery needs
to be replaced. As a result, the battery can be used efficiently.
Any of the zoom motor and the focus motor may be driven first when
the amount by which the voltage decreases is larger than the predetermined
value. In accordance with a third aspect of the present invention,
it is preferably controlled such that the zoom motor is driven first
and then the focus motor is driven. Because of the above-described
control, mechanical drawbacks such as a case in which a space formed
due to movement of the zoom lens is so small that the focus lens
cannot be moved to a predetermined position and the like can be
prevented.
In accordance with a fourth aspect of the present invention, there
is provided a digital camera comprising: (a) a housing having a
lens barrel movable along an optical axis; (b) a zoom lens group
and a focus lens group movable relative to one another along the
optical axis in the lens barrel; (c) a zoom motor connected to the
lens barrel operable for moving the lens barrel to a position corresponding
to a selected magnification; (d) a focus motor connected to the
focus lens group operable for moving the focus lens group to a focus
position corresponding to the selected magnification; (e) a lens
cover movable between closed and open positions for protecting at
least one lens, and a lens cover driving motor connected to the
lens cover, operable for moving the lens cover between closed and
open positions; (f) an internal electric power source connectable
to an AC power source; (g) a controller connected to the internal
electric power source, and controlling the zoom motor and the focus
motor, the controller controlling the zoom motor and the focus motor
to substantially overlap in operation upon power initiation to move
the lens groups to initialization positions if the internal electric
power source is connected to an AC power source; and (h) an image
sensor supported in the housing for receiving light through the
lens groups, the image sensor being operable for producing data
in correspondence with light received through the lens group for
image recording.
That is, when the alternating power source is connected, even if
the zoom motor and the focus motor are driven simultaneously, there
is no lack of the electric energy. Therefore, in accordance with
the fourth aspect of the present invention, a determination is made
as to whether the alternating power source is connected and if it
is determined that the alternating power source is connected, it
is controlled such that the zoom motor and the focus motor to be
driven simultaneously. In this way, the start-up time until the
digital camera is in a state in which photographing is possible
can be reduced.
Whether or not the alternating power source is connected is determined
by, for example, a detector in which when a socket of the alternating
power source is inserted, an amount of electric power supplied thereto
(the amount by which it is energized) changes so that whether or
not the socket of the alternating power source is inserted is detected.
Alternatively, it may be structured such that a user can manually
give instructions as to whether or not the alternating power source
is connected and a determination is made on the basis of the instructions.
In accordance with a fifth aspect of the present invention, a determination
is also made as to whether or not the alternating power source is
connected on the basis of a power source voltage value at a time
when the camera is energized and an amount by which the voltage
decreases when either the lens cover driving motor or the zoom motor
is driven.
That is, because the power source voltage value of the alternating
power source at a time of energizing is higher than that of a storage
battery and the amount by which the voltage decreases is smaller
than the predetermined value, a determination as to whether or not
the alternating power source is connected can be made on the basis
of the voltage value at a time of energizing and the amount by which
the voltage decreases.
In accordance with a sixth aspect of the present invention, in
the digital camera according to the first aspect through the fifth
aspect, the controller includes a clock, the controller determining
electric energy availability of the power source on the basis of
at least one of a power source voltage value during power initiation
and the voltage decrease when one of the lens cover driving motor
and the zoom motor is driven, and when the electric energy energy
availability is less than a predetermined amount, sets a lower clock
frequency for the clock. That is, by lowering the clock frequency
to one lower than the standard clock frequency, a clock rate becomes
slow, thus electric energy consumption can be decreased. Therefore,
there is no waste of the battery such as a case in which although
the electric power is sufficient for photographing, it is insufficient
for driving the zoom lens such that photographing becomes difficult
and a battery needs to be replaced. As a result, the battery can
be used efficiently.
In accordance with a seventh aspect of the present invention, the
controller determines whether or not an AC power source is connected
to the internal power source, on the basis of a power source voltage
value during power initiation and a voltage decrease when one of
the lens cover driving motor and the zoom motor is operated. That
is, by making the clock frequency lower than the standard clock
frequency, a clock rate becomes slow, thus electric energy consumption
can be decreased. Therefore, there is no waste of the battery such
as a case in which although the electric power is sufficient for
photographing, it is insufficient for driving the zoom lens such
that a photographing becomes difficult and a battery needs to be
replaced. As a result, the battery can be used efficiently.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a perspective view of an exterior of a digital camera
relating to a first embodiment of the present invention.
FIG. 1B is a front view showing the exterior of the digital camera
relating to the first embodiment of the present invention in a state
in which a lens is accommodated when a power source is turned off.
FIG. 2 is an exploded perspective view of lenses of the digital
camera shown in FIGS. 1A and 1B.
FIG. 3 is a cross-sectional view showing retraction positions of
the lenses in the digital camera shown in FIGS. 1A and 1B.
FIG. 4 is a cross-sectional view showing tele positions of the
lenses in the digital camera shown in FIGS. 1A and 1B.
FIG. 5 is a cross-sectional view showing wide positions of the
lenses in the digital camera shown in FIGS. 1A and 1B.
FIGS. 6A and 6B are block diagrams of the digital camera of the
first embodiment.
FIGS. 7A and 7B are flowcharts of drive control of a zoom motor
and a focus motor.
FIG. 8 is a graph showing changes in voltage when an alternating
power source, an alkaline battery, an alkaline battery with a small
amount of charge, an NiMH battery and an NiMH battery with a small
amount of charge are used as a power source of the digital camera
of the first embodiment.
FIGS. 9A and 9B are flowcharts of drive control of the zoom motor
and the focus motor relating to a second embodiment of the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
Hereinafter, a first embodiment of the present invention will be
described in detail with reference to the drawings. A digital camera
10 to which the present invention is applied is formed of, as shown
in FIGS. 1A and 1B, a photographing device 30 (see FIGS. 3 through
5) including a shutter button 12, a zoom lens 14 (details thereof
will be described later) and a CCD and the like, a flash 16, a memory
card drive 20 (see FIG. 6) and a control section 22 which controls
the driving of these components (see FIG. 6) and the like.
The zoom lens 14 is formed by, as shown in FIGS. 2 through 5, a
forward lens group 50, a backward lens group 52 a focus lens 53,
a first lens cylinder 54, a moving cylinder 58, a second lens cylinder
56, a fixed cylinder 60 and a rotating cylinder 62.
A gear portion 64 is formed at an outer circumferential surface
of the rotating cylinder 62 at a camera main body side thereof.
The driving force of a DC motor 70 (see FIG. 3) which is a zoom
motor is transmitted to the gear portion 64, thereby the rotating
cylinder 62 rotates while contacting the outer circumferential surface
of the fixed cylinder 60. A second lens cam unit 90 and a straight
advancing guide groove 92 for a moving cylinder are formed at an
inner circumferential surface of the rotating cylinder 62. The second
lens cam unit 90 moves the second lens cylinder 56 to be described
later in a direction of optical axis 100. The straight advancing
guide groove 92 for a moving cylinder applies rotational drive of
the rotating cylinder 62 to the moving cylinder 58 to be described
later and allows forward and backward movements of the moving cylinder
58 along the optical axis 100.
A straight advancing guide opening 86 for second lens which guides
the second lens cylinder 56 so that it can go straight in a direction
of optical axis 100 and a moving cylinder cam 88 which moves the
moving cylinder 58 in the direction of optical axis 100 are formed
at an inner circumferential surface of the fixed cylinder 60.
The second lens cylinder 56 has the backward lens group 52 and
the focus lens 53 therein. The backward lens 52 is held by a second
lens frame 57 provided within the second lens cylinder 56 (see FIGS.
3 through 5).
The second lens frame 57 is provided with a stepping motor 72 which
is a focus motor. Driving of the stepping motor 72 is transmitted
via a feed screw 65 to a focus lens frame 59 (see FIGS. 3 through
5).
The focus lens frame 59 is movable along the optical axis by a
guide pin 63 and the feed screw 65 which are provided at the second
lens frame 57. The focus lens frame 59 moves in the direction of
optical axis 100 in accordance with a lead of the feed screw 65
which rotates in accordance with a drive amount of the stepping
motor 72. The focus lens frame 59 moves between an original position
which is nearest to an imaging surface side with respect to the
second lens cylinder 56 and a position which is apart from the original
position toward a subject side. Driving of the stepping motor 72
will be described later.
A plurality of second lens cam follower units 80 and a plurality
of straight advancing guide protrusions 82 (FIG. 2) are provided
at the outer circumferential surface of the second lens cylinder
56. The second lens cam follower units 80 engage with the second
lens cam unit 90 provided at the rotating cylinder 62 and the straight
advancing guide opening 86 for second lens provided at the fixed
cylinder 60. The straight advancing guide protrusions 82 engage
with straight advancing guide grooves 66 of the first lens cylinder
54 to be described later. Accordingly, due to rotation of the rotating
cylinder 62, the second lens cylinder 56 moves straight in the direction
of optical axis 100 with respect to the fixed cylinder 60.
A plurality of springs 84 are provided between the second lens
cylinder 56 and the fixed cylinder 60 (see FIG. 2). The second lens
cylinder 56 is continuously urged to an imaging surface side of
a photographing device by the springs 84.
The moving cylinder 58 is provided with a first lens cam 76 and
a plurality of moving cylinder cam followers 78. The first lens
cam 76 engages with first lens cam followers 68 which will be described
later. The moving cylinder cam followers 78 engage with the moving
cylinder cam 88 of the above-described fixed cylinder 60 and the
straight advancing guide groove 92 of the above-described rotating
cylinder 62.
The first lens cylinder 54 holds the forward lens group 50 therein
by a lens holding frame which is provided within an opening end
of the first lens cylinder 54. A plurality of straight advancing
guide grooves 66 are formed at an inner circumferential surface
of the first lens cylinder 54. A plurality of first lens cam followers
68 are provided at an outer circumferential surface of the first
lens cylinder 54. The straight advancing guide grooves 66 engage
with the above-described straight advancing guides of the second
lens cylinder 56. The first lens cam followers 68 engage with the
first lens cam 76.
That is, the moving cylinder 58 moves along the optical axis 100
in accordance with rotation of the above-described rotating cylinder
62. In accordance with the movement of the moving cylinder 58, the
straight advancing guide protrusions 82 of the second lens cylinder
56 move within the straight advancing guide grooves 66. At the same
time, the first lens cam 76 of the moving cylinder 58 acts such
that the first lens cylinder 54 moves straight along the optical
axis 100 with respect to the moving cylinder 58.
The first lens cam followers 68, the moving cylinder cam followers
78, the second lens cam follower units 80, the straight advancing
guide opening 86 for second lens, the straight advancing guide grooves
92 for moving cylinder and the springs 84 are respectively provided
at positions which divide a circumference of a circle about the
optical axis 100 into three areas.
When a power source is turned off, as shown in FIG. 3, the first
lens cylinder 54, the moving cylinder 58, the second lens cylinder
56, the fixed cylinder 60 and the rotating cylinder 62 are retracted
within a housing of the digital camera 10. The forward lens group
50, the backward lens group 52 and the focus lens 53 are accommodated
within the retracted cylinders so as to be close with each other.
A front surface of the forward lens group 50 is covered with a lens
cover 61 which can open/close (see FIG. 1B).
The lens cover 61 is opened or closed by a lens cover motor 74.
Driving of the lens cover motor 74 is controlled by a control section
22 (see FIGS. 6A and 6B). That is, the lens cover motor 74 is controlled
by the control section 22 such that the lens cover 61 is opened
when the power source is turned on. Moreover, the lens cover motor
74 is driven by the control section 22 such that when the power
source is turned off, the zoom lens 14 is accommodated within the
digital camera 10 so as to be retracted therein and then the lens
cover 61 is closed.
As shown in FIGS. 6A and 6B, the control section 22 is formed of
a CPU 22a, a ROM 22b and a RAM 22c. Connected via a bus 88 to the
control section 22 are a shutter button 12, a memory card drive
20, a driving circuit 24, a distance measuring section 32, a photometric
section 34, a memory 42, a compression/decompression section 44,
a display 46 and an operation button 48.
A voltage value of a power source 94 inputted via the bus 88 is
temporarily stored in the RAM 22c. A program for controlling the
above-mentioned various types of components connected to the control
section 22 is stored in the ROM 22b. Further, also stored in the
ROM 22b is a program to be described later which determines an amount
of electric energy of the power source and the type thereof based
on the voltage value of the power source 94 stored in the RAM 22c
so as to control driving of the DC motor 70 and the stepping motor
72.
The CPU 22a reads out various types of programs from the ROM 22b
so as to control respective components. Further, the CPU 22a reads
the program for controlling the driving of the DC motor 70 and the
stepping motor 72 from the ROM 22b. Then, the CPU 22a determines
the type of the power source which is being used from the voltage
value of the power source 94 stored in the RAM 22c so as to set
the DC motor 70 and the stepping motor 72 to be driven simultaneously
or sequentially.
For example, the CPU 22a determines an automatic focusing (AF)
control value on the basis of a distance to a subject which is measured
in the distance measuring section 32 to output the resultant AF
control value to the driving circuit 24. Then, the driving circuit
24 drives the stepping motor 72 in accordance with the AF control
value to move the focus lens 53 such that focus adjustment is automatically
carried out.
At the photometric section 34, the CPU 22a determines exposure
control values such as a diaphragm value (an amount of opening of
diaphragm), a shutter speed, whether or not light is emitted by
the flash 16 and the like to output results to the driving circuit
24. If the shutter button 12 is pressed downward, the driving circuit
24 drives the shutter 26, the diaphragm 28, the flash 16 and the
photographing device 30 on the basis of the exposure control values
such that a subject image transmitted through the forward lens group
50, the backward lens group 52 and the focus lens 53 is photographed.
Further, the CPU 22a drives the DC motor 70 in accordance with
a selected magnification and moves the forward lens group 50 and
the backward lens group 52 to respective positions corresponding
to the selected magnification.
In the first embodiment, there are two methods for moving the focus
lens 53 at a time of start-up. One method is to move the focus lens
53 at the same time when the forward lens group 50 and the backward
lens group 52 are moved. Another method is to move the focus lens
53 after the forward lens group 50 and the backward lens group 52
have moved (i.e., after a lens barrel has been extended to an initialization
position). The CPU 22a selects a start-up method on the basis of
the program for controlling the driving of the DC motor 70 and the
stepping motor 72, which program is read from the ROM 22b, and controls
the DC motor 70 and the stepping motor 72. Control of the DC motor
70 and the stepping motor 72 by the CPU 22a at the time of start-up
will be described later.
Connected to the driving circuit 24 which is connected via the
bus 88 to the control section 22 are the flash 16, the shutter 26,
the diaphragm 28, the photographing device 30, the DC motor 70,
the stepping motor 72 and the lens cover motor 74. The photographing
device 30 includes, for example, a photographing element such as
a CCD or the like.
Electric charges corresponding to an amount of light entered in
accordance with the exposure control value are accumulated in the
photographing device 30. Accumulated electric charges, i.e., an
image signal is outputted to an analog signal processing section
36.
The analog signal processing section 36 carries out a predetermined
analog signal processing (for example, a noise reduction processing)
on the inputted image signal to output the resultant signal to an
A/D conversion section 38. In the A/D conversion section 38, the
inputted analog signal is converted into a digital signal and the
resultant digital signal is outputted to a digital signal processing
section 40. The digital signal processing section 40 carries out
a predetermined digital signal processing (for example, a shading
correction processing) on the inputted digital signal to output
image data to the memory 42. An image of the image data outputted
to the memory 42 is displayed on the display 46.
In the digital camera 10, an image photographed by carrying out
a predetermined operation with the operation button 48 can be stored
in a memory card such as a smart media, a floppy disc or the like.
In this case, image data stored in the memory 42 is outputted to
the compression/decompression section 44. In the compression/decompression
section 44, a predetermined image compression processing (for example,
a JPEG compression processing) is carried out. The compressed image
data is outputted to the memory card drive 20 and then written in
the memory card.
In the digital camera 10, the compressed image data stored in the
memory card can also be read out. In this case, the compressed image
data read from the memory card is outputted to the compression/decompression
section 44 and is subjected to decompression processing in the compression/decompression
section 44. In this way, the compressed image is converted into
an original image. The decompressed image is displayed on the display
46.
The digital camera 10 can not only photograph an image at a predetermined
point of time but also continuously display an image of a subject
which is being photographed like a video camera (which will be referred
to as a movie mode hereinafter).
A determination as to whether or not a photographed image can be
visually confirmed is carried out by, for example, determining whether
or not a light amount measured in the photometric section 34 is
at least a predetermined value. Also, whether or not an amount of
electric charges accumulated in the CCD of the photographing device
30 is at least a predetermined value can be determined.
Basically, respective components of the digital camera 10 are operated
by electricity being supplied thereto from a main power source which
is not shown (for example, an NiMH battery or an alkaline battery).
If the main power source is turned off, electricity is supplied
by a sub power source (for example, a lithium battery) so as to
suppress the consumption of power from the main power source.
In FIG. 8, there are shown a voltage change 122 when the power
source 94 is turned off, a voltage change 124 when the lens cover
motor 74 is driven, a voltage change 126 when only the DC motor
70 is driven, a voltage change 128 when the DC motor 70 and the
stepping motor 72 are simultaneously driven, using an alternating
power source (a power source with large electric energy) 110, a
fully-charged alkaline battery (a power source with small electric
energy) 112, an alkaline battery with a small amount of charge (a
power source with small electric energy) 114, a fully-charged NiMH
battery (a power source with large electric energy) 116 and an NiMH
battery with a small amount of charge (a power source with small
electric energy) 118.
Voltage values and amounts by which the voltage decreases described
herein are only examples and the present invention is not limited
to these values.
A description will be given of control by the CPU 22a at a time
of start-up with reference to flowcharts of FIGS. 7A and 7B. In
the zoom lens 14 in a retracted state before the power source is
turned on, as shown in FIG. 3, the forward lens group 50, the backward
lens group 52 and the focus lens 53 are close to each other and
are respectively disposed at their accommodated positions nearest
to the imaging surface side of the photographing device 30.
When the power source 94 is turned on, in step 200, a power source
voltage is fetched. Then, the process proceeds to step 202. In step
202, a determination is made as to whether the fetched power source
voltage value is larger than or equal to a first predetermined value.
That is, if the power source is the alternating power source 110
or the fully-charged NiMH battery 112, it is determined that the
power source voltage value is larger than or equal to the first
predetermined value. If the power source is the fully-charged alkaline
battery 116, the alkaline battery 114 with a small amount of charge
or the NiMH battery 118 with a small amount of charge, it is determined
that the power source voltage value is less than the first predetermined
value. The first predetermined value is 2.9 V as understood from
FIG. 8, but is not limited thereto.
If the power source voltage value is at least the first predetermined
value, the power source voltage is either the alternating power
source 110 or the fully-charged NiMH battery 112. Then, the process
proceeds to step 204 and in step 204, the lens cover motor 74 is
driven to open the lens cover 61. In step 206, an amount by which
the voltage decreases at that time, i.e., an amount by which the
voltage decreases from a power source terminal voltage value when
the power source is turned on is less than or equal to a first predetermined
amount. The first predetermined amount is an amount by which the
alternating power source and the fully-charged alkaline battery
can be distinguished, and is preferably 0.1 V from FIG. 8, but is
not limited thereto.
If the amount by which the voltage decreases is less than or equal
to the first predetermined amount, it is determined from FIG. 8
that the power source being used is an alternating power source
with a large amount of electric energy. In step 208, the DC motor
70 and the stepping motor 72 are driven simultaneously.
That is, the lens barrel is extended and the zoom lens is moved
due to driving of the DC motor 70 such that a space is formed within
the digital camera 10. The stepping motor 72 is driven substantially
simultaneously with the formation of the space such that the focus
lens 53 is moved to a focusing position within the space.
The rotating cylinder 62 rotates in an accommodation rotation range
from an initial position to an intermediate position so as to move
the zoom lens 14 from the retracted position shown in FIG. 3 to
a tele (far off) position shown in FIG. 4. Further, the rotating
cylinder 62 rotates in a magnification-changing rotation range from
the intermediate position to an end position so as to move the zoom
lens 14 from the tele position to a wide position shown in FIG.
5. The forward lens group 50, the backward lens group 52 and the
focus lens 53 are moved to predetermined initialization positions.
The stepping motor 72 is driven during driving of the DC motor
70 by a predetermined drive amount every fixed period of time which
is determined in advance or every predetermined fixed clock so as
to move the focus lens 53 such that when the zoom lens has moved
(i.e., when the lens barrel has extended to the initialization position),
the focus lens 53 is disposed at the initialization position. By
driving the DC motor 70 as described above, it is possible to reduce
the start-up processing time which is the time from when the power
source is turned on until the digital camera is in a state in which
photographing is possible.
In step 210, it is determined whether the voltage when the DC motor
and the stepping motor are driven simultaneously is smaller than
or equal to a second predetermined value (for example, less than
or equal to 2.3 V). If the voltage is smaller than or equal to the
second predetermined value, the electric energy of the power source
which is being currently used may be decreasing. If the DC motor
and the stepping motor continue to be driven simultaneously, there
are possibilities that sufficient amount of electric energy may
not be obtained at a time of photographing or the motors may stop
due to lack of electric energy. Thus, the process proceeds to step
215 and in step 215 the stepping motor 72 stops. Then, the process
proceeds to step 222 to be described later.
If the voltage is not smaller than or equal to the second predetermined
value, the electric energy of the power source which is being used
at that time is sufficient. Thus, the DC motor and the stepping
motor continue to be driven simultaneously. The process proceeds
to the subsequent step 212 and in step 212 a determination is made
as to whether the forward lens group 50, the backward lens group
52 and the focus lens 53 have reached the initialization positions.
In step 212, if it is determined that the forward lens group 50,
the backward lens group 52 and the focus lens 53 have not reached
the initialization positions, the process returns to step 210 and
the above-described processing in step 210 is repeated. If it is
determined that the forward lens group 50, the backward lens group
52 and the focus lens 53 have reached the initialization positions,
in step 214 the driving of the DC motor 70 and the stepping motor
72 stop and then the present routine ends.
On the other hand, in step 202, when the fetched power source voltage
value is smaller than the first predetermined value, the process
proceeds to step 216 and in step 216 the lens cover motor 74 is
driven to open the lens cover 61. In step 218, it is determined
that the amount by which the voltage decreases at that time, i.e.,
the amount by which the voltage is less than the power source terminal
voltage value when the power source is turned on is larger than
the second predetermined amount. The second predetermined amount
is an amount to distinguish between the fully-charged NiMH battery
116, the alkaline battery 114 which is charged by a small amount
and the NiMH battery 118 which is charged by a small amount and
is preferably 0.15 V from FIG. 8, but is not limited thereto.
If the amount by which the voltage decreases is less than the second
predetermined amount, it is determined that the fully-charged NiMH
battery 116 is used. Then, the process proceeds to step 208 and
the above-described processings are repeated. If the amount by which
the voltage decreases is larger than the second predetermined amount,
it is determined that the alkaline battery 114 with a small amount
of charge or the NiMH battery 118 with a small amount of charge
is used and the process proceeds to step 220.
In step 220, the DC motor 70 is driven to move the forward lens
group 50 and the backward lens group 52. In the subsequent step
222, if it is determined that the forward lens group 50 and the
backward lens group 52 have reached the predetermined initialization
positions, the process proceeds to the subsequent step 224. In step
224, driving of the DC motor 70 stops and the stepping motor 72
is driven to move the focus lens 53 to the focusing position.
In step 226, a determination is made as to whether the focus lens
53 has reached the initialization position which is the focusing
position and if it is determined that the focus lens 53 has reached
the initialization position, in step 228, driving of the stepping
motor 72 stops and the present routine ends.
In this way, in a case of a power source with a small amount of
electric energy, the DC motor 70 and the stepping motor 72 are controlled
to be driven sequentially. Thus a load on the power source is reduced
and the digital camera 10 can be set to a state in which photographing
is possible.
In the above-described first embodiment, a determination is made
as to whether or not the power source voltage decreases while the
DC motor 70 and the stepping motor 72 are being driven simultaneously.
Then if the power source voltage decreases, the DC motor 70 and
the stepping motor 72 are separately driven. Thus even if a high
load is exerted when the DC motor 70 and the stepping motor 72 are
driven simultaneously such the amount of electric energy used becomes
large, abrupt decreases in the amount of electric energy can be
avoided. It may also be structured such that a determination is
not made as to whether or not the power source voltage decreases
while the DC motor 70 and the stepping motor 72 are being driven
simultaneously.
In the first embodiment, a determination is made as to whether
or not the alternating power source is connected and the magnitude
of the electric energy of the power source is determined using the
amount by which the voltage decreases when the lens cover motor
74 is driven so as to control the driving of the DC motor 70 and
the stepping motor 72. The present invention is not limited to the
above-described structure. For example, the driving of the DC motor
70 and the stepping motor 72 may be controlled based on the amount
by which the voltage decreases when the DC motor 70 which is a zoom
motor is driven.
In the above-described case, for example, it may be structured
such that the amount by which the voltage decreases after a predetermined
time elapses since the driving of the DC motor 70 starts is used.
The voltage value which varies due to the driving of the DC motor
70 is detected continuously or every time a predetermined time elapses
such that the amount by which the voltage decreases with respect
to a previously detected voltage or to a voltage detected in the
beginning can be used. When the amount by which the voltage decreases
based on the driving of the DC motor 70 is used, the present invention
can be applied to a digital camera in which a lens cover which opens/closes
by a driving means is not provided.
As a practical application of the present invention, a determination
may be made as to whether or not the alternating voltage is connected
and the magnitude of the electric energy of the power source may
be determined using the amount by which the voltage decreases caused
by, in addition to the lens cover motor 74 and the DC motor 70,
components which are driven at first at a time of start-up so as
to control the driving of the DC motor 70 and the stepping motor
72.
The digital camera 10 is structured such that either an AA battery
such as an NiMH battery, an alkaline battery or the like or an alternating
power source is selected as a main power source. The battery to
be used is not limited to the NiMH battery or the alkaline battery.
Although the AA battery is used as the alkaline battery, batteries
other than the AA battery can be used.
In the first embodiment, a zoom lens consisting of two groups is
used, but the present invention is not limited to this zoom lens
and the zoom lens may include three groups or more. The present
invention can be applied not only to a zoom lens camera but also
to a two-focus camera in which switching between a tele position,
a wide position and a retracted position is carried out. Further,
although the tele position is set between the retracted position
and the wide position, the wide position can be set between the
retracted position and the tele position.
Second Embodiment
A second embodiment of the present invention will be described
hereinafter with reference to FIGS. 9A and 9B. The second embodiment
is the same as the first embodiment except that control by the CPU
22a at a time of start-up is different. Thus only the control by
the CPU 22a at a time of start-up will be described and other descriptions
will be omitted. The steps in FIGS. 9A and 9B which are the same
as in FIGS. 7A and 7B are denoted by the same reference numerals
and descriptions thereof will be omitted, only portions that differ
will be described.
The stepping motor 72 stops in step 215 in FIGS. 9A and 9B. Then,
the process proceeds to step 230. In step 218 in FIGS. 9A and 9B,
if an amount by which the voltage decreases at a time of driving
the lens cover motor 74 is larger than the second predetermined
amount, the process proceeds to step 230.
In step 230, a determination is made as to whether or not the voltage
value when driving the lens cover motor 74 is smaller than a predetermined
third value. The third predetermined value is an upper limit of
the amount of electric energy which is insufficient if the DC motor
70 is driven at a standard clock (for example, 100 MHz), but sufficient
to drive the DC motor 70 if the DC motor 70 is driven at a low speed
clock (for example, 50 MHz). Setting of the standard clock or the
low speed clock can be appropriately changed in accordance with
specifications. Further, a plurality of low speed clocks may be
set. In this case, smaller the electric energy becomes, slower the
start-up processing becomes. Moreover, the electric energy of the
power source is determined and if the electric energy is less than
a predetermined amount, a lower clock frequency than the standard
clock frequency of a CPU, a photographing system or a signal processing
system, may be set.
In step 230, if the voltage value at a time of driving the lens
cover motor 74 is smaller than the third predetermined value, the
process proceeds to step 232. In step 232, a clock is set to a low
speed clock. Then, in step 220, the DC motor is driven. On the other
hand, in step 230, the voltage value when driving the lens cover
motor 74 is larger than the third predetermined value, the process
proceeds to step 234 and in step 234 a clock is set to a standard
clock. Then, in step 220 the DC motor is driven.
As described above, in the second embodiment, a clock frequency
is changed in accordance with the electric energy of the power source.
Thus, the present invention has an effect in which batteries with
low electric energy are effectively used so as not to waste the
electric energy.
As described above, the digital camera according to the first aspect
of the present invention has an effect in which when the power source
which is being used is a power source with a large amount of electric
energy, the zoom motor and the focus motor are driven simultaneously
so as to reduce the start-up time.
In accordance with the second aspect of the present invention,
an effect can be obtained in which when the power source which is
being used is a power source with a small amount of electric energy,
the zoom motor is driven to move the zoom lens to the initialization
position and then the focus motor is moved, thus energy in a battery
can be used with little waste.
Further, in accordance with the third aspect through the fifth
aspect of the present invention, an effect can be obtained in which
when the power source which is being used is an alternating power
source, the zoom motor and the focus motor are driven simultaneously
so as to reduce the start-up time.
Particularly, in accordance with the fifth aspect of the present
invention, an effect can be obtained in which since a determination
as to whether or not the alternating power source is connected is
made on the basis of the voltage value when the power source is
turned on and the amount by which the voltage decreases, it is not
necessary to add a device for determining whether or not the alternating
power source is connected, resulting in a simpler structure.
In accordance with the sixth and seventh aspects of the present
invention, an effect in which a battery can be fully used without
wasting energy can be obtained. |