U.S. patent application number 13/054183 was filed with the patent office on 2011-05-19 for imaging device.
Invention is credited to Eiji Anno, Shinji Furuya, Yuichi Suzuki, Tomoaki Tsutsumi.
Application Number | 20110115971 13/054183 |
Document ID | / |
Family ID | 41529997 |
Filed Date | 2011-05-19 |
United States Patent
Application |
20110115971 |
Kind Code |
A1 |
Furuya; Shinji ; et
al. |
May 19, 2011 |
IMAGING DEVICE
Abstract
The present invention provides an image capture device that can
omit calculating a pulse signal that should otherwise be used to
get a flash fired during a flash-ON sequential shooting operation.
An image capture device includes: an image capturing section
configured to capture a subject's image; a flashing section
configured to store electricity and emitting flash light using the
electricity; a power supply configured to supply the electricity;
and a control section configured to control the supply of the
electricity to the flashing section. If the flashing section
performs preliminary flashing and main flashing sequentially, the
control section supplies no electricity to the flashing section
after the preliminary flashing is done and before the main flashing
is performed for a first time. But after the main flashing is done
for the first time, the control section continues to supply, in an
interval before a next main flashing, the electricity to the
flashing section until the flashing section recovers a quantity of
electricity stored there when the main flashing was performed for
the first time.
Inventors: |
Furuya; Shinji; (Osaka,
JP) ; Anno; Eiji; (Nara, JP) ; Suzuki;
Yuichi; (Osaka, JP) ; Tsutsumi; Tomoaki;
(Osaka, JP) |
Family ID: |
41529997 |
Appl. No.: |
13/054183 |
Filed: |
July 16, 2009 |
PCT Filed: |
July 16, 2009 |
PCT NO: |
PCT/JP2009/003366 |
371 Date: |
January 14, 2011 |
Current U.S.
Class: |
348/371 ;
348/E5.024 |
Current CPC
Class: |
H04N 5/351 20130101;
H04N 5/2354 20130101; G03B 15/05 20130101; H04N 5/243 20130101;
G03B 7/08 20130101; G03B 2215/05 20130101; H04N 5/343 20130101 |
Class at
Publication: |
348/371 ;
348/E05.024 |
International
Class: |
H04N 5/225 20060101
H04N005/225 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2008 |
JP |
2008186942 |
Claims
1. An image capture device comprising: an image capturing section
configured to capture a subject's image; a flashing section
configured to store electricity and emitting flash light using the
electricity; a power supply configured to supply the electricity;
and a control section configured to control the supply of the
electricity to the flashing section, wherein if the flashing
section performs preliminary flashing and main flashing
sequentially, the control section supplies no electricity to the
flashing section after the preliminary flashing is done and before
the main flashing is performed for a first time, and after the main
flashing is done for the first time, the control section continues
to supply, in an interval before a next main flashing, the
electricity until the flashing section recovers a quantity of
electricity stored there when the main flashing was performed for
the first time.
2. The image capture device of claim 1, wherein the control section
detects a quantity of electricity that has been stored in the
flashing section after the preliminary flashing is done and
supplies the electricity based on that quantity detected after the
main flashing is done for the first time.
3. The image capture device of claim 2, further comprising a
storage section for storing information, wherein the control
section detects the quantity of electricity that has been stored in
the flashing section after the preliminary flashing is done, gets
information about the quantity of electricity detected stored in
the storage section, and supplies the electricity by reference to
that information about the quantity of electricity stored in the
storage section after the main flashing is done for the first
time.
4. The image capture device of claim 3, wherein when the quantity
of electricity recovers the quantity of electricity stored when the
main flashing was performed for the first time, the control section
stops supplying the electricity.
5. The image capture device of claim 4, wherein the storage section
stores information about voltage values as the information about
the quantity of electricity.
Description
TECHNICAL FIELD
[0001] The present invention relates to an image capture device
such as a digital still camera or a digital movie camera.
BACKGROUND ART
[0002] A conventional image capture device is disclosed in Patent
Document No. 1.
[0003] The image capture device includes a means for setting a
flash-ON sequential shooting mode and a switching means for
switching the imager reading methods into a pixel mixing drive when
the flash-ON sequential shooting mode is selected. In this manner,
in performing sequential shooting with the flash fired, this image
capture device compensates for the lack of quantity of light
received by the imagers and increases the read rate of the
imagers.
[0004] According to Patent Document No. 1, a flash firing time is
determined first and then modified. Specifically, for that purpose,
the digital camera disclosed in Patent Document No. 1 reads an
appropriate correction coefficient, which is associated with the
number of image shots that are stored in the memory, from a table
of correction coefficients and then multiplies the flash firing
time determined by that correction coefficient. And the digital
camera uses the product as a modified flash firing time.
CITATION LIST
Patent Literature
[0005] Patent Document No. 1: Japanese Patent Application Laid-Open
Publication No. 2007-163561
SUMMARY OF INVENTION
Technical Problem
[0006] According to the technique disclosed in Patent Document No.
1, however, complicated processing should be done because every
time an image is shot, the flash firing time needs to be modified
by performing such a computation using the correction
coefficient.
[0007] On top of that, information about the number of image shots
is required to determine the correction coefficient. Furthermore,
to make the intensity of the flash light emitted during sequential
shooting as uniform as possible, the correction coefficient should
be adjusted according to the flash firing time for the first shot
and the voltages of a built-in capacitor right after the first and
second image shots have been taken, thus requiring overly
complicated computations, too.
[0008] The present invention has been made in view of the
aforementioned problems, and an objective thereof is to omit
calculating a pulse signal that should otherwise be used to get a
flash fired during a flash-ON sequential shooting operation.
Solution to Problem
[0009] An image capture device according to the present invention
includes: an image capturing section configured to capture a
subject's image; a flashing section configured to store electricity
and emitting flash light using the electricity; a power supply
configured to supply the electricity; and a control section
configured to control the supply of the electricity to the flashing
section. If the flashing section performs preliminary flashing and
main flashing sequentially, the control section supplies no
electricity to the flashing section after the preliminary flashing
is done and before the main flashing is performed for a first time.
But after the main flashing is done for the first time, the control
section continues to supply, in an interval before a next main
flashing, the electricity to the flashing section until the
flashing section recovers a quantity of electricity stored there
when the main flashing was performed for the first time.
[0010] The control section may detect a quantity of electricity
that has been stored in the flashing section after the preliminary
flashing is done and may supply the electricity based on that
quantity detected after the main flashing is done for the first
time.
[0011] The image capture device may further include a storage
section for storing information. The control section may detect the
quantity of electricity that has been stored in the flashing
section after the preliminary flashing is done, may get information
about the quantity of electricity detected stored in the storage
section, and may supply the electricity by reference to that
information about the quantity of electricity stored in the storage
section after the main flashing is done for the first time.
[0012] When the quantity of electricity recovers the quantity of
electricity stored when the main flashing was performed for the
first time, the control section may stop supplying the
electricity.
[0013] The storage section may store information about voltage
values as the information about the quantity of electricity.
Advantageous Effects of Invention
[0014] Once main flashing is done for the first time, an image
capture device according to the present invention continues to
supply, in an interval before the next main flashing, electricity
to the flashing section until the flashing section recovers a
quantity of electricity stored there when the main flashing was
performed for the first time. A pulse signal to be applied to get
the flashing section fired should ordinarily be calculated and
adjusted according to the quantity of electricity stored in the
flashing section. In the image capture device of the present
invention, however, every time main flashing is performed, the
quantity of electricity is the same as what was stored in the
flashing section when the main flashing was performed for the first
time. That is why there is no need to adjust the pulse signal and
the complicated pulse signal computing process can be omitted.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 illustrates the general appearance of a digital
camera 100 as a specific preferred embodiment of the present
invention.
[0016] FIG. 2 illustrates the internal configuration of the digital
camera 100.
[0017] FIG. 3 is a table defining a correlation between the ISO
sensitivity, the need of pixel mixing processing, and the increase
in gain by an AGC.
[0018] FIG. 4 shows ISO sensitivities at which gain adjustment
processing and pixel mixing processing are carried out.
[0019] FIG. 5 shows a variation in the voltage value of the
capacitor of a flash.
[0020] FIG. 6 is a flowchart showing the procedure of processing to
be done by the digital camera 100.
[0021] FIG. 7 is a flowchart showing the procedure of processing to
be done by the digital camera 100.
DESCRIPTION OF EMBODIMENTS
[0022] Hereinafter, preferred embodiments of an image capture
device according to the present invention will be described with
reference to the accompanying drawings.
1. How the Digital Camera 100 of this Preferred Embodiment Operates
in Principle
[0023] FIG. 1 illustrates the general appearance of a digital
camera 100 as a specific preferred embodiment of the present
invention, while FIG. 2 illustrates the internal configuration of
the digital camera 100. Hereinafter, it will be described with
reference to FIGS. 1 and 2 how this digital camera 100 operates in
principle.
[0024] When the user presses down a shutter release button 11
fully, the digital camera 100 of this preferred embodiment accepts
it as his or her instruction to start shooting. In accordance with
a single instruction to start shooting, this digital camera 100 can
sequentially perform a number of shooting sessions with the flash
fired for actual exposure (which will be referred to herein as
"main flashing"). As is well known in the art, the "flash" is a
light emitting member to be used for ensuring a sufficient amount
of light for shooting.
[0025] However, before starting the sequential shooting sessions
with the flash 8 fired for actual exposure, the digital camera 100
fires the flash 8 preliminarily (which will be referred to herein
as "preliminary flashing"). And during this preliminary flashing,
the controller 7 performs a photometry process on the light that
has been reflected from the subject. The photometry process may be
carried out based on the light that has been incident on a CCD
sensor 2 (to be described later) or on a dedicated photometric
sensor.
[0026] Based on the result of this photometry process, the digital
camera 100 acquires the sensitivity information (which will be
referred to herein as "ISO sensitivity") of a CCD image sensor 2
(which will be simply referred to herein as a "CCD") during the
main flashing, thereby setting shooting conditions according to the
ISO sensitivity acquired. Examples of the shooting conditions
include an intensity of the flash light emitted by the flash 8
during the main flashing, a method of reading out a pixel signal
from the CCD 2, and an amplification gain of an analog front end
(which will be abbreviated herein as "AFE") 3. In accordance with
these shooting conditions determined, the digital camera 100
controls the flash 8, the CCD driving section 4, and/or the AFE
3.
[0027] Following the instruction given by the controller 7, the CCD
driving section 4 controls the method of reading out a pixel signal
from the CCD 2. Then, the digital camera 100 controls the flash 8
and the CCD driving section 4, thereby getting shooting sessions
done sequentially with the main flashing. The CCD driving section 4
drives the CCD 2 so as to make the CDD 2 generate an image signal.
As used herein, "to drive the CCD 2" means supplying power to the
CCD 2 to read a signal and performing a readout control to read an
electrical signal representing the intensity of the light from a
particular line of photodiodes among a huge number of photodiodes
on the CCD 2.
[0028] The digital camera 100 can control the flash 8 and the CCD
driving section 4 so that the shooting sessions are sequentially
done with the main flashing. The image signal generated by the CCD
2 is converted into image data by the AFE 3 and an image processing
section 5. Then, the controller 7 stores the image data thus
obtained in a memory card 15. In this manner, the digital camera
100 can get sequential shooting done with the main flashing.
[0029] Also, after the flash 8 has been fired preliminarily, the
digital camera 100 detects the voltage value of a capacitor used in
the flash 8 and stores the voltage value in a buffer memory 6.
After that, the digital camera 100 fires the flash 8 for the main
flashing the first time. As a result, the CCD 2 receives the
incoming light, converts an analog signal representing the
intensity of the light received into a digital signal, and then
outputs it as image data. In this manner, the first shooting
session is done.
[0030] Then, the digital camera 100 charges the capacitor (not
shown) in the flash 8 based on the voltage value stored in the
buffer memory 6. And when the capacitor is charged to the initially
detected value, the digital camera 100 fires the flash 8 for the
main flashing the second time and gets the second shooting session
done using the CCD 2.
2. Configuration of Digital Camera 100
[0031] Next, the general appearance of the digital camera 100 and
the respective components thereof will be described with reference
to FIGS. 1 and 2 again.
[0032] As shown in FIG. 2, the optical system 1 includes various
optical elements and components for driving those optical elements.
For example, the optical system 1 may include a focus lens, a zoom
lens, a diaphragm and an actuator for driving these elements.
[0033] The light collected by the optical system 1 is incident on
the CCD 2, which includes a number of photodiodes and receives the
incoming light at the photodiodes. In response, each of those
photodiodes transforms the incoming light into an electrical signal
representing its intensity. An image signal is generated based on
the electrical signals that have been generated by those
photodiodes. It is controlled by the CCD driving section 4 how to
read out the electrical signals from the CCD 2.
[0034] The image signal generated by the CCD 2 is input to the AFE
3, which has various components and performs multiple functions
using them. For example, the AFE 3 may include an AGC (automatic
gain control) amplifier, a CDS (correlated double sampling)
circuit, and an A/D converter (none of which is shown). The image
signal is amplified by the AGC amplifier, which is supposed to
amplify the image signal with the amplification gain that has been
determined by the controller 7. The CDS circuit reduces the noise
components of the image signal. And the A/D converter converts the
image signal supplied from the AGC (as an analog signal) into a
digital signal and outputs it as image data.
[0035] The image processing section 5 subjects the image data that
has been converted into a digital signal by the AFE 3 to image
processing. Examples of such image processing may include, but are
not limited to, gamma transformation, YC conversion, electronic
zooming, compression, and expansion. Then, the image processing
section 5 stores the image data that has been subjected to the
image processing in the buffer memory 6. The image data stored in
the buffer memory 6 is converted into a display image by the image
processing section 5 and then presented on an LCD 12.
[0036] The flash 8 may include a xenon lamp and a capacitor
(neither is shown). The capacitor stores the electrical charge
(i.e., electricity) supplied from a power supply 10. The flash 8
releases the electrical charge stored in the capacitor and applies
a voltage to the xenon lamp, thereby flashing the xenon lamp.
[0037] In a situation where a shooting session needs to be
performed with the flash 80N, when sensing the user press down the
shutter release button 11 fully, the controller 7 not only fires
the flash 8 but also drives the CCD driving section 4. At this
point in time, the controller 7 supplies a pulse signal to the
flash 8 for a main flashing. On the other hand, in a situation
where a shooting session needs to be performed with the flash 8
OFF, when sensing the user press down the shutter release button 11
fully, the controller 7 drives the CCD driving section 4 without
firing the flash 8.
[0038] The controller 7 stores the image data, represented by the
image signal that has been generated by the CCD 2, in either a
flash memory 13 or the memory card 15 loaded in a card slot 14.
2-1. Various Controls Performed by Controller 7
[0039] In a situation where a shooting session needs to be
performed with the flash 80N, after having sensed the user press
down the shutter release button 11 fully, the controller 7 controls
the flash 8 to fire preliminarily. The preliminary flash light is
emitted with a predetermined intensity (e.g., at a guide number
(GN) of 0.7). During the preliminary flashing, the controller 7
controls the CCD driving section 4 so that the CCD 2 generates an
image signal. In this case, an ISO 100 converted amplification gain
is supposed to be defined for the AGC of the AFE 3. As a result,
the controller 7 acquires image data based on the image signal.
Then, based on the image data thus obtained, the controller 7
measures the intensity of the light that has been reflected from
the subject during the preliminary flashing. Also, based on the
information about luminance that has been obtained by getting the
image data subjected to the YC conversion by the image processing
section 5, the controller 7 calculates the intensity of the
reflected light. In that case, the controller 7 calculates the
intensity of the reflected light by working out the average of
luminance values within a photometric range defined in a portion of
the image data. Such an operation is called a "photometry". As the
F number and the shutter speed to be set during the preliminary
flashing, values that are stored beforehand in the flash memory 13
may be used.
[0040] And based on the intensity of this reflected light, the
controller 7 determines the intensity of light during the main
flashing (which will be referred to herein as "main flash light").
In this preferred embodiment, to get sequential shooting sessions
done at a high rate, a GN of 2.0 is set as the maximum intensity of
the main flash light. However, the maximum intensity does not have
to be this value but could also be defined in advance or specified
by the user.
[0041] Hereinafter, it will be described how to calculate the
intensity of the main flash light.
[0042] First of all, the controller 7 calculates an appropriate
intensity of the main flash light (which will be referred to herein
as an "appropriate main flash light GN") without taking the maximum
intensity of the flash light into account.
[0043] According to this preferred embodiment, by reference to the
table that defines the relation between the intensity of the
reflected light during the preliminary flashing and the appropriate
main flash light GN, the appropriate main flash light GN is
obtained based on the intensity of the reflected light. In this
case, the table tabulates the relation between the intensity of the
reflected light and the main flash light GN in a situation where
the sensitivity of the CCD 2 is set to be ISO 100. Specifically, in
the table, multiple values are listed as the intensities of
reflected light (which will be referred to herein as "reflected
light intensities") and associated with respective main flash light
GNs. That is to say, the table associates the main flash light GNs
with the intensities of the reflected light in the descending
order. For example, main flash light GN #1, #2 and #3 are
associated with the reflected light intensities #1, #2 and #3,
respectively.
[0044] The following Table 1 is an example of such a table. This
table may be stored, along with another table shown in FIG. 3 (to
be described later), in an internal buffer (not shown) of the
controller 7 or in a flash memory 13, for example. It should be
noted that as values representing the reflected light intensities
will vary according to the output of the CCD 2 built in and other
factors, specific values are not presented in the following
table:
TABLE-US-00001 TABLE 1 Reflected light intensity #1 GN1 Reflected
light intensity #2 GN2 Reflected light intensity #3 GN3 . . . . . .
Reflected light intensities: #1 > # 2 > #3 > . . .
[0045] By reference to this table, the controller 7 calculates the
appropriate main flash light GN. Specifically, first of all, the
controller 7 detects the intensity of the reflected light. And if
the controller 7 has found an exactly matching reflected light
intensity on the table, then the controller 7 simply retrieves its
associated main flash light GN. On the other hand, if the
controller 7 has found no matching reflected light intensities on
the table, then the controller 7 performs a linear interpolation on
two closest reflected light intensities on the table, which are
respectively higher and lower than the reflected light intensity
detected, and their associated main flash light GNs, thereby
calculating an appropriate main flash light GN. For example, if the
reflected light intensity detected is between the reflected light
intensities #2 and #3 mentioned above, then the controller 7
performs a linear interpolation on the reflected light intensity
#2, which is closest to, and higher than, the reflected light
intensity detected, and its associated main flash light GN #2, and
the reflected light intensity #3, which is closest to, and lower
than, the reflected light intensity detected, and its associated
main flash light GN #3, thereby calculating the best main flash
light GN.
[0046] If the appropriate main flash light GN thus calculated is
smaller than the maximum value of the main flash light GN, the
controller 7 stores the former main flash light GN as the intensity
of the main flash light in the buffer memory 6. On the other hand,
if the appropriate main flash light GN thus calculated is greater
than the maximum value, then the controller 7 stores the maximum
value as the intensity of the main flash light in the buffer memory
6.
[0047] For example, if the appropriate main flash light GN is 1.9,
then the intensity of the main flash light should have a GN of 1.9.
On the other hand, if the appropriate main flash light GN is 2.9,
then the intensity of the main flash light should have a GN of 2.0.
According to this preferred embodiment, the image capture device is
designed such that multiple bursts of main flash light have the
same intensity.
[0048] Also, if the appropriate main flash light GN is greater than
the maximum intensity, then the controller 7 adjusts the ISO
sensitivity of the CCD 2 by controlling the CCD 2 and the AFE 3.
This adjustment is done in order to control the brightness of the
image captured with the ISO sensitivity of the CCD 2 for the excess
of the appropriate main flash light GN over the maximum value.
Specifically, the ISO sensitivity may be adjusted in the following
manner.
[0049] In this preferred embodiment, the rate of increase or
decrease in ISO sensitivity (ISO/100) is calculated by the
following Equation (1):
Rate of increase or decrease in ISO sensitivity=((appropriate main
flash light GN)/(maximum main flash light GN)).sup.2 (1)
Then, according to this rate of increase or decrease in ISO
sensitivity, the controller 7 determines what ISO sensitivity ISO
100 should be changed to.
[0050] For example, if the appropriate main flash light GN is 4.0
and if the maximum main flash light GN is 2.0, then the rate of
increase or decrease in ISO sensitivity is 4.0. In this example,
since the ISO sensitivity during the preliminary flashing is ISO
100, the ISO sensitivity of the CCD 2 during the main flashing
should be ISO 400.
[0051] According to the ISO sensitivity thus calculated, the
controller 7 controls the CCD 2 and the AFE 3 during the main
flashing. The controller 7 may store the table shown in FIG. 3, for
example. By reference to the table with the ISO sensitivity
calculated, the controller 7 determines whether the image signal
should be read by either pixel mixing reading method (e.g., 9-pixel
mixing according to this preferred embodiment) or standard reading
method with no pixel mixing, and also determines how much the AGC
gain should be increased. Using these tables and values, the
controller 7 controls the CCD 2 and the AFE 3.
[0052] For example, if the ISO sensitivity calculated is ISO 800,
the controller 7 may adopt a standard driving method with no pixel
mixing as the method of reading out an image signal from the CCD 2
and may set the amplification level of the AFE 3 to a value
associated with ISO 800. On the other hand, if the ISO sensitivity
calculated is ISO 1600, the controller 7 may adopt a pixel mixing
driving (e.g., 9-pixel mixing) as the method of reading an image
signal from the CCD 2 and may set the amplification level of the
AFE 3 to a value associated with ISO 178.
[0053] The amplification levels that are not listed on the table
may be calculated by linear interpolation. As for the reading
method, if the ISO sensitivity is equal to or higher than ISO 1001
that is a threshold value, the pixel mixing driving may be adopted.
On the other hand, if the ISO sensitivity is less than ISO 1001
(i.e., equal to or lower than ISO 1000), then the standard driving
method (i.e., every pixel reading driving) may be adopted. That is
to say, a threshold value may be set to determine whether the
reading method should be pixel mixing reading or standard reading
and may be stored in either the controller 7 or the flash memory
13.
[0054] Optionally, the table shown in FIG. 3 could be stored in the
flash memory 13, too. It should be noted that the table shown in
FIG. 3 does not have to be used. That is to say, it may be
determined by calculation, without using a table, which reading
method should be adopted and how much the gain of the AGC should be
increased.
[0055] Hereinafter, it will be described how the pixel mixing
driving may get done as being applied to the nine pixel mixing
described above. First of all, suppose the CCD 2 has multiple types
of pixel groups. As used herein, the "multiple types of pixel
groups" refer to pixel groups, of which the photoelectric
conversion abilities have mutually different sensitivity properties
according to the wavelength of the incoming light. For example,
those pixel groups may include a group of pixels with red (R)
sensitivity property, a group of pixels with green (G) sensitivity
property, and a group of pixels with blue (B) sensitivity
property.
[0056] The CCD 2 can read pixel signals that have been generated by
those multiple types of pixel groups independently of each other.
As a result, image signals are obtained and images (or frames) are
generated on a sensitivity property basis.
[0057] As an example, it will be described how to carry out pixel
mixing driving on red (R). The CCD 2 adds together the pixel
signals representing nine red (R) pixels, which are arranged as a
three (horizontal) by three (vertical) matrix, and outputs the sum
as a pixel signal representing a single pixel. As a result, even if
the intensity of the light falling on the entire CCD 2 is low, an
intensity that is high enough for a single pixel can still be
ensured. Nevertheless, since a pixel signal representing a single
pixel is formed of the nine pixels yet to be subjected to the pixel
mixing driving, the resolution will decrease to one-third both
vertically and horizontally.
[0058] It should be noted that such a pixel mixing technique that
uses nine pixels is just an example. Alternatively, four, sixteen
or six pixels could be used as well. Also, the number of horizontal
pixels does not always have to be the same as, but may be different
from, that of vertical pixels.
[0059] Furthermore, although a group of pixels with the red (R)
sensitivity property has been described as an example, the same
processing will be performed on the green (G) and blue (B) pixels
as well.
[0060] According to this preferred embodiment, if the intensity of
the reflected light during the preliminary flashing is high, the
digital camera 100 will adjust the intensity of the main flash
light to cope with that as shown in FIG. 4. Meanwhile, as the
intensity of the reflected light during the preliminary flashing
decreases, the digital camera 100 not only adopts the maximum
intensity of the main flash light but also adjusts the ISO
sensitivity of the CCD 2. In that case, while the ISO sensitivity
is still low, the digital camera 100 adjusts the amplification gain
of the AFE 3. However, as the ISO sensitivity increases, the
digital camera 100 not only adjusts the amplification gain of the
AFE 3 but also changes the methods of reading the pixels of the CCD
2. As a result, if the ISO sensitivity of the CCD 2 is low, the
digital camera 100 performs a control operation so as to generate
an image signal with non-decreased resolution from the CCD 2. On
the other hand, if the ISO sensitivity of the CCD 2 is high, then
the digital camera 100 performs a control operation so as to
generate an image signal with high sensitivity from the CCD 2.
Since the amplification can be done by the AFE 3 within a narrower
range, the CCD 2 can generate an image signal with reduced noise
while taking the resolution into consideration.
[0061] Thereafter, the controller 7 detects the voltage value of
the capacitor in the flash 8. In the example illustrated in FIG. 5,
the voltage value detected at a time T1, when the preliminary
flashing is done, is 270 V. Then, the controller 7 stores that
voltage value detected in the buffer memory 6.
[0062] After that, the controller 7 instructs the flash 8 to emit
the main flash light and drives the CCD driving section 4, thereby
making the CCD 2 generate an image signal. In this case, the
controller 7 controls the flash 8 and drives the CCD driving
section 4 without a break, thereby getting the sequential shooting
done with the flash ON.
[0063] In the example illustrated in FIG. 5, the digital camera 100
starts the main flashing as soon as the preliminary flashing gets
done at the time T1. This is done to eliminate a shuttering time
lag by starting the shooting right after the preliminary flashing
is finished. In a situation where such a shuttering time lag is
permitted, however, the voltage level may be restored to a full
charge level of 290 V again when the preliminary flashing gets
done, and then the main flash light may be emitted.
2-2. How to Control Respective Sections when Sequential Shooting is
Performed with Main Flashing
[0064] The controller 7 not only instructs the flash 8 to emit the
main flash light but also drives the CCD driving section 4, thereby
getting the sequential shooting done with the main flash light
emitted. Hereinafter, it will be described exactly how to get these
operations done.
[0065] Specifically, the controller 7 controls the flash 8 so that
the flash 8 emits the main flash light based on the intensity of
the main flash light that is stored in the buffer memory 6. In this
case, the main flash light can be emitted based on the intensity of
the main flash light by changing the pulse signals to be supplied
to the flash 8.
[0066] Furthermore, the controller 7 also drives the CCD driving
section 4 to make the CCD 2 generate an image signal, while making
the flash 8 emit the main flash light. Then the controller 7
instructs the AFE 3 to generate image data in the digital form. The
image processing section 5 subjects the digitized image data to
image processing and then stores it in the buffer memory 6. Then,
the controller 7 writes the image data that has been stored in the
buffer memory 6 on the memory card 15.
[0067] Thereafter, to get the next main flash light emitted, the
controller 7 controls the power supply 10 so that electrical charge
is supplied to the flash 8. On sensing that the voltage value of
the flash 8 has reached the voltage value stored in the buffer
memory 6 due to the supply of the electrical charge from the power
supply 10, the controller 7 gets the supply of the electrical
charge from the power supply 10 to the flash 8 stopped.
[0068] Then, the controller 7 controls the flash 8 to get the next
main flash light emitted. Also, the controller 7 drives the CCD
driving section 4, thereby making the CCD 2 generate an image
signal. And then the controller 7 writes the image data that has
been digitized by the AFE 3 and then subjected to the image
processing by the image processing section 5 on the memory card
15.
[0069] The intensity of the main flash light to be emitted for the
second time and on is the same as that of the main flash light that
has been emitted previously. And the voltage value of the capacitor
charged is approximately the same as the voltage value when the
main flash light was emitted the last time. That is why the pulse
signal representing the intensity of the main flash light (i.e., a
signal to be input to fire the flash) is also the same.
[0070] It should be noted that the intensity of the flash light
emitted should be adjusted according to the voltage value of the
capacitor during the flashing. Suppose a voltage of 100 V should be
applied to emit flash light with certain intensity when the
capacitor has a voltage value of 270 V. In that case, to achieve
the same flash light intensity even when the capacitor has a
voltage value of 170 V, not a voltage of 100 V but a voltage of
approximately 110 V should sometimes be applied. That is to say, it
should be calculated how much voltage should be applied to achieve
the flash light intensity required. This is because the processing
of changing the pulse signals according to the voltage value of the
capacitor is so complicated that it would take a lot of time and
trouble to program such processing in advance.
[0071] For that reason, if the voltage value of the capacitor from
the second main flashing on is regulated to be approximately the
same as the one during the previous main flashing as is done in
this preferred embodiment, then there is no need to change the
pulse signals anymore. In other words, there is no need to
calculate the pulse signals (or the duration of the flashing in
Patent Document No. 1) using a correction coefficient and regulate
the voltage as shown in FIG. 5 of Patent Document No. 1. As a
result, a memory to store the correction coefficient and the
resources of the device that would otherwise be allocated for that
purpose can be saved.
[0072] The processing described above is carried out continuously
while the shutter release button 11 is pressed down fully or until
a predetermined number of image shots have been taken.
2-3. How Image Data to be Recorded Changes Depending on whether
Pixel Mixing Driving is Adopted or not
[0073] As described above, according to this preferred embodiment,
the CCD 2 is supposed to change the methods of reading an image
signal according to the ISO sensitivity calculated. Hereinafter, it
will be described how the image data to be recorded changes
depending on whether the pixel mixing driving is adopted or not.
Under the control of the CCD driving section 4, the CCD 2 operates
while switching between the pixel mixing reading mode and the every
pixel reading mode. The CCD 2 is supposed to be an imager with nine
mega (approximately nine million) effective pixels. In the
following description, "mega" will refer to either the number of
effective pixels of the CCD or the number of pixels of an image
shot with the CCD, not the data size of the image data.
[0074] First of all, it will be described what image data will be
generated unless the pixel mixing driving is adopted. In that case,
first, the CCD 2 reads the image signal from multiple pixels as it
is. That is why the image signal to be output from the CCD 2 will
have approximately nine million pixels. The AGC amplifier of the
AFE 3 amplifies that image signal with a preset amplification gain,
which is an amplification level that has been defined by the
controller 7. Thereafter, the A/D converter of the AFE 3 digitizes
the amplified image signal. Specifically, the AFE 3 outputs the
image data to the image processing section 5, which subjects the
image data to image processing, thereby compressing the image data
to three mega pixels. As used herein, the "compression" refers to
pixel thinning processing. Then, the controller 7 writes the image
data that has been subjected to that image processing on the memory
card 15.
[0075] Next, it will be described what image data will be generated
if the pixel mixing driving is adopted. In that case, first, when
reading image signals from multiple pixels, the CCD 2 mixes image
signals from pixels representing the same color. As described
above, according to the pixel mixing of this preferred embodiment,
three horizontal pixels by three vertical pixels (i.e., nine pixels
in total) are mixed together for each of the three primary colors
of R, G and B. Image signals that have been mixed together in this
manner are output from the CCD 2. Consequently, the image signals
output from the CCD 2 have approximately one million (i.e., one
mega) pixels, which is one-ninth compared to a situation where no
pixel mixing driving is adopted. The output image signals of the
CCD 2 are amplified and digitized by the AFE 3 and then output as
image data. Then, the image processing section 5 subjects the image
data supplied from the AFE 3 to image processing. In that case, the
image processing section 5 not only rearranges the R, G and B
pixels into a desired order but also increases the number of pixels
by interpolation so that the image data with one mega pixels comes
to have three mega pixels. In this case, any of various known
interpolation methods such as bi-cubic method and bilinear method
could be adopted.
[0076] According to the processing method just described, the
number of pixels is supposed to be increased by performing
interpolation on the image that has been obtained by the pixel
mixing reading method. However, interpolation does not always have
to be performed. Unless interpolation is carried out, the image
that has been obtained without performing the pixel mixing reading
may be compressed so that the number of its pixels is reduced from
nine mega pixels to one mega pixels. Speaking more generally, the
image obtained without performing the pixel mixing reading may be
compressed to have the smallest number of pixels to be obtained by
the pixel mixing reading.
[0077] By unifying the numbers of pixels of the images generated
into three mega pixels as described above, this image capture
device will come in handier for the user when he or she needs to
sort out, view or edit the image data afterward. Particularly for a
user who is not used to operating the digital camera 100, he or she
would find it troublesome if the numbers of pixels (i.e., the image
sizes) changed every shooting session. That is why it would be
useful to unify those numbers of pixels.
[0078] Meanwhile, it is also possible to let the number of pixels
of the image generated change depending on whether the pixel mixing
reading is adopted or not. For example, the image generated with
the pixel mixing reading could have 1 M (one mega) pixels and the
image generated without the pixel mixing reading could have 9 M
pixels. In that case, even though the numbers of pixels are not
unified, an image with high resolution can always be obtained.
[0079] Then, the controller 7 writes the image data that has been
subjected to such image processing on the memory card 15. It should
be noted that the pixel mixing method described above is just an
example and any other pixel mixing driving technique could also be
adopted as well.
[0080] According to the preferred embodiment described above, the
number of pixels of the image data to be recorded is supposed to
remain the same (e.g., 3 M pixels), no matter whether the pixel
mixing method is adopted or not. However, the present invention is
in no way limited to that specific preferred embodiment.
Optionally, the number of pixels of the image data to be recorded
could also change depending on whether the pixel mixing is adopted
or not.
3. Operation
[0081] Hereinafter, it will be described with reference to the
flowcharts shown in FIGS. 6 and 7 how the digital camera 100 with
such a configuration operates. The digital camera 100 will operate
as described below after the power of the digital camera 100 has
been turned from OFF into ON and if the mode of operation of the
digital camera 100 is set to be flash-ON sequential shooting mode.
It should be noted that the digital camera 100 is designed so as to
select one of multiple modes including the flash-ON sequential
shooting mode. Also, according to this preferred embodiment, if the
flash-ON sequential shooting mode is selected, the amplification
gain of the AGC amplifier is set to be an amplification level
associated with the ISO 100.
[0082] First of all, the controller 7 determines whether or not the
shutter release button 11 has been pressed down fully in Step A1.
If the answer is YES, the controller 7 instructs the flash 8 to
emit preliminary flash light in Step A2. Meanwhile, the controller
7 also drives the CCD driving section 4, thereby acquiring image
data based on the image signal supplied from the CCD 2. And then
based on the image data acquired, the controller 7 calculates the
intensity of the light reflected from the subject during the
preliminary flashing in Step A2.
[0083] Next, in Step A3, the controller 7 calculates the best
intensity of the main flash light based on the intensity of the
reflected light obtained. Then, in Step A4, the controller 7
determines whether or not the best main flash light intensity
calculated is greater than the value that has been stored as the
maximum intensity.
[0084] If the answer to the query of Step A4 is NO (i.e., if the
best intensity of the main flash light is equal to or smaller than
the maximum intensity), then the controller 7 stores the best
intensity of the main flash light that has been calculated in the
previous processing step A3 as the main flash light intensity in
the buffer memory 6 (in Step A7). After that, the controller 7
starts the sequential shooting operation shown in FIG. 7 (in Step
A2).
[0085] On the other hand, if the answer to the query of Step S4 is
YES (i.e., if the best intensity of the main flash light is greater
than the maximum intensity), then the controller 7 stores the
intensity of the main flash light that has been stored as the
maximum value as the main flash light intensity in the buffer
memory 6 (in Step AS). Next, based on the best main flash light
intensity calculated, the controller 7 calculates the ISO
sensitivity of the CCD 2 during the main flashing.
[0086] Subsequently, the controller 7 determines in Step A9 whether
or not the ISO sensitivity thus calculated is equal to or greater
than a predetermined sensitivity. If the answer is YES, the
controller 7 adopts the pixel mixing driving as the method of
reading an image signal for the CCD 2 (in Step A10). On the other
hand, if the ISO sensitivity is less than the predetermined
sensitivity, then the controller 7 adopts a standard every pixel
reading driving method, not the pixel mixing driving, as the method
of reading out an image signal from the CCD 2 (in Step A11). In
these processing steps A10 and All, the controller 7 defines the
reading method for the CCD 2 by controlling the CCD driving section
4.
[0087] After having performed the processing step A10 or A11, the
controller 7 calculates an amplification gain based on the ISO
sensitivity obtained in the processing step A6 and the table shown
in FIG. 3 and sets the gain for the AFE 3 (in Step A12).
Thereafter, the controller 7 starts the sequential shooting
operation shown in FIG. 7 (in Step A13).
[0088] Hereinafter, the sequential shooting operation shown in FIG.
7 to be started in the processing step A8 or A13 will be
described.
[0089] First, the controller 7 detects the voltage value of the
capacitor in the flash 8 that has been fired preliminarily, and
then stores information about the voltage value detected in the
buffer memory 6 (in Step B1).
[0090] Next, the controller 7 instructs the flash 8 to emit main
flash light based on the main flash light intensity stored in the
buffer memory 6. Meanwhile, the controller 7 also drives the CCD
driving section 4, thereby making the CCD 2 generate an image
signal and acquiring image data based on the image signal generated
by the CCD 2. And then the controller 7 stores the image data on
the memory card 15 (in Step B2).
[0091] Subsequently, the controller 7 determines whether or not the
maximum allowable number of photos have been taken yet as the image
data and whether or not the full pressure on the shutter release
button 11 has been removed yet (in Step B3). If the answer is YES
(i.e., if the maximum allowable number of photos have already been
taken as the image data or if the pressure on the shutter release
button 11 has already been removed completely), then the controller
7 ends the sequential shooting operation.
[0092] On the other hand, if the maximum allowable number of photos
have not been taken as the image data yet and if the pressure on
the shutter release button 11 has not quite been removed yet, then
the controller 7 supplies electrical charge from the power supply
10 to the capacitor of the flash 8 until the voltage value stored
in the buffer memory 6 is reached (in Step B4). After that, the
process goes back to the processing step B2 and the sequential
shooting operation is repeatedly performed with the flash ON until
the answer to the query of the processing step B3 becomes YES.
[0093] Hereinafter, it will be described with reference to FIG. 5
how the voltage value varies in the capacitor.
[0094] First, on sensing the shutter release button 11 be pressed
down fully (at a time T0), the controller 7 supplies a pulse signal
representing the GN to the flash 8 to fire the flash 8 for the
preliminary flashing. In response, the flash emits a quantity of
electrical charge as defined by the pulse signal (in the period
from the time T0 through a time T1). When the preliminary flashing
is completed, the controller 7 determines, according to the ISO
sensitivity calculated, whether the every pixel reading or the
pixel mixing reading should be adopted as the driving method, and
makes settings to use the reading method selected (at the time T1).
Thereafter, to get the main flash light emitted without charging,
the controller 7 supplies a pulse signal, representing the
intensity (GN) of the main flash light, to the flash 8. In
response, the flash 8 emits a quantity of electrical charge as
defined by the pulse signal (in the period from the time T1 through
the end of the electrical charge emission). In this case, since the
controller 7 makes the CCD 2 perform an exposure process by driving
the CCD driving section 4, the controller 7 will not start
controlling the flash 8 until the CCD 2 finishes the exposure
process (in the period from the end of the electrical charge
emission through a time T2). On sensing the CCD 2 finish the
exposure process, the controller 7 instructs the power supply 10 to
supply electrical charge to the flash 8 (at the time T2). And on
finding that the voltage value of the flash 8 has reached the
stored voltage value, the controller 7 stops charging (at a time
T3). Then, the controller 7 supplies a pulse signal representing
the intensity (GN) of the main flash light to the flash 8 to emit
the next main flash light. In response, the flash 8 emits a
quantity of electrical charge as defined by the pulse signal (in
the period from the time T3 through the end of the electrical
charge emission). In this period, the same operation is carried out
as in the period from the time T1 through the time T2. After that,
the same processing will be carried out repeatedly, and the
description thereof will be omitted herein.
[0095] According to this preferred embodiment, the controller 7 of
the digital camera selects one of multiple reading methods,
including the mixing reading, according to the ISO sensitivity and
can drive the CCD 2 by the selected method. Thus, the digital
camera can get an image signal generated by the CCD with the noise
reduced and with the resolution taken into account.
[0096] Alternatively, the digital camera 100 may include: a flash 8
that stores electricity in itself and emits the electricity stored,
thereby irradiating a subject with main flash light; a CCD 2 for
capturing a subject's image that has been produced by an optical
system 1 and generating an image signal; and a controller 7 that
makes the CCD 2 generate multiple image signals sequentially by
having the flash 8 emit main flash light a number of times with the
same intensity each time, detects the quantity of electricity
stored in the flash 8 before making the flash 8 emit the main flash
light for the first time, and changes the quantities of electricity
supplied to the flash 8 according to the quantity of electricity
detected when the flash 8 is made to emit the main flash light for
the second time after having been made to emit the main flash light
for the first time.
[0097] The digital camera 100 changes the quantities of electricity
supplied to the flash 8 according to the quantity of electricity
detected by the controller 7 before the flash 8 is made to emit the
main flash light the next time. That is to say, when making the
flash 8 emit the main flash light for the second time, the
controller 7 substantially equalizes the quantity of electricity
stored in the flash 8 with the quantity during the first main
flashing. As a result, the digital camera does not have to
calculate a pulse signal to make the flash emit the main flash
light at the same intensity, although such calculation would
otherwise have to be done if the quantities of electricity stored
in the flash were different.
[0098] Hereinafter, another preferred embodiment of the present
invention will be described as a modified example of the preferred
embodiment that has already been described.
[0099] In the preferred embodiments described above, a CCD image
sensor is supposed to be used as an exemplary imaging means.
However, this is just an example. Alternatively, the imaging means
could also be a CMOS image sensor. In that case, the power
dissipation could be cut down.
[0100] Also, in the preferred embodiments described above, the
emission means is supposed to be a flash. However, the present
invention. is in no way limited to that specific preferred
embodiment. Alternatively, an LED flash could also be used.
[0101] Also, in the preferred embodiment described above, the ISO
sensitivity is supposed to be determined by the intensity of the
reflected light that has been detected during the preliminary
flashing. However, this is just an example. Alternatively, the ISO
sensitivity may also be determined in accordance with the user's
command that has been entered through an interface such as some
keys or buttons (like cross arrow keys) on the camera. In other
words, the user may set the ISO sensitivity of the digital camera
by operating such an interface. In response, the controller is
given the ISO sensitivity that he or she has chosen and determines,
according to the ISO sensitivity selected, which pixel reading
method should be adopted for the CCD.
[0102] Furthermore, according to the preferred embodiment described
above, the CCD is supposed to change the pixel reading methods
during the main flashing. However, the present invention is in no
way limited to that specific preferred embodiment. Optionally, even
an image signal supplied continuously from the CCD (i.e., an image
signal representing a through-the-lens image on the LCD) may also
be generated with the pixel reading methods changed.
[0103] Also, in the preferred embodiment described above, the
appropriate main flash GN (i.e., the intensity of the main flash
light) is supposed to be obtained by reference to the table.
However, this is just an example. Alternatively, the intensity of
the main flash light could also be calculated by some equation that
is used generally.
[0104] Furthermore, in the preferred embodiment described above,
the rate of increase or decrease in ISO sensitivity (ISO/100) is
supposed to be calculated by Equation (1). However, the present
invention is in no way limited to that specific preferred
embodiment. If necessary, the rate of increase or decrease in ISO
sensitivity could also be obtained by any other method.
[0105] Also, in the preferred embodiment described above, the
capacitor is supposed to be charged in the interval between the
emissions of main flash light based on the voltage value of the
capacitor that has been detected after the preliminary flashing.
However, the present invention is in no way limited to that
specific preferred embodiment. Alternatively, a predetermined
voltage value (of 270 V, for example) could be stored in a flash
memory 13, which is an exemplary storage medium, and the capacitor
could also be charged between the emissions of main flash light
based on the predetermined voltage value stored. There is no need
to detect the voltage value of the capacitor after the preliminary
flashing.
[0106] In that case, if the voltage value of the capacitor when the
main flashing is performed for the first time is predictable, then
the voltage value can be approximately the same when the main flash
light is emitted next time. As a result, there is no need to
calculate any pulse signals during the next main flashing. The
voltage value of the capacitor during the first emission of the
main flash light is predictable in a situation where the GN of the
preliminary flash light has been defined as a predetermined value
with no shooting control performed or in a situation where the
digital camera is designed so as to be able to charge the capacitor
fully in a predetermined amount of time (e.g., 10 seconds), for
example.
[0107] In the preferred embodiments described above, the decision
whether to perform pixel mixing or not is supposed to be made
according to the sensitivity information only when the flash-ON
sequential shooting mode is selected. However, this is only an
example. Alternatively, it may also be determined, according to the
sensitivity information, whether the pixel mixing should be done or
not in any other shooting mode. Nevertheless, if the decision
whether or not to perform the pixel mixing is made according to the
sensitivity information only in a particular shooting mode such as
the flash-ON sequential shooting mode but if no such decisions are
made in any other mode as in the preferred embodiment described
above, then the following effect will be achieved. Specifically, in
that particular mode, the image capture device will operate with
the SNR of the colors of the image captured taken into account. But
in another mode, the image capture device will operate with a
higher priority put on the resolution of the image captured. That
is to say, the user can get an image captured with the color SNR
increased in a certain mode and with the resolution increased in
another mode.
[0108] That is to say, the present invention is in no way limited
to those specific preferred embodiments described above but may be
modified in numerous ways and may assume many embodiments other
than those specifically described above.
[0109] For example, if the controller 7 described above is
implemented as a microcomputer, the processing that has been
described above with reference to the flowcharts of the
accompanying drawings could be implemented as a program to be
executed by the microcomputer. Such a computer program may be
circulated on the market by being stored on a storage medium such
as a CD-ROM or downloaded over telecommunications lines such as the
Internet.
INDUSTRIAL APPLICABILITY
[0110] The present invention is applicable to various kinds of
image capture devices including digital still cameras, digital
movie cameras and cellphones with a built-in camera.
REFERENCE SIGNS LIST
[0111] 100 digital camera [0112] 1 optical system [0113] 2 CCD
[0114] 3 AFE [0115] 4 CCD driving section [0116] 5 image processing
section [0117] 6 buffer memory [0118] 7 controller [0119] 8 flash
[0120] 10 power supply [0121] 11 shutter release button [0122] 12
LCD [0123] 13 flash memory [0124] 14 card slot [0125] 15 memory
card
* * * * *