U.S. patent application number 12/314664 was filed with the patent office on 2009-06-25 for image capturing apparatus.
This patent application is currently assigned to NIKON CORPORATION. Invention is credited to Toshihisa Kuroiwa.
Application Number | 20090160969 12/314664 |
Document ID | / |
Family ID | 40788134 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090160969 |
Kind Code |
A1 |
Kuroiwa; Toshihisa |
June 25, 2009 |
Image capturing apparatus
Abstract
An image capturing apparatus can use a reading time from an
image sensor efficiently. To achieve the object, the image
capturing apparatus includes an image capturing unit which
separates a color image of a subject being captured by an image
sensor having pixels of colors into three or more fields and
outputs said three or more fields successively, and an image
processing unit which generates a low-resolution image which is
lower in resolution than the color image obtained by the image
capturing unit, based on output of one or more fields among said
three or more fields, said one or more fields being able to extract
color information of all the colors, wherein the image processing
unit starts generation of the low-resolution image in a period in
which fields other than said one or more fields for generating the
low-resolution image are read.
Inventors: |
Kuroiwa; Toshihisa;
(Miura-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
NIKON CORPORATION
Tokyo
JP
|
Family ID: |
40788134 |
Appl. No.: |
12/314664 |
Filed: |
December 15, 2008 |
Current U.S.
Class: |
348/223.1 ;
348/222.1; 348/E5.031; 348/E9.052 |
Current CPC
Class: |
H04N 9/04557 20180801;
H04N 9/045 20130101; H04N 2209/046 20130101; H04N 5/2628 20130101;
H04N 9/04515 20180801; H04N 5/3456 20130101; H04N 5/23293
20130101 |
Class at
Publication: |
348/223.1 ;
348/222.1; 348/E05.031; 348/E09.052 |
International
Class: |
H04N 5/228 20060101
H04N005/228; H04N 9/73 20060101 H04N009/73 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2007 |
JP |
2007-332281 |
Claims
1. An image capturing apparatus comprising: an image capturing unit
which separates a color image of a subject being captured by an
image sensor having pixels of colors into three or more fields and
outputs said three or more fields successively; and an image
processing unit which generates a low-resolution image which is
lower in resolution than the color image obtained by the image
capturing unit, based on output of one or more fields among said
three or more fields, said one or more fields being able to extract
color information of all the colors, wherein the image processing
unit starts generation of the low-resolution image in a period in
which fields other than said one or more fields for generating the
low-resolution image are read.
2. The image capturing apparatus according to claim 1, wherein: the
low-resolution image is an image for checking a result of
capturing; and the image capturing apparatus further comprises a
display unit which displays the low-resolution image when the
low-resolution image is generated by the image processing unit.
3. The image capturing apparatus according to claim 1, further
comprising a field selecting unit which selects one field from the
fields, wherein: the image processing unit includes a
pre-processing part which performs pre-processing on the color
image output from the image capturing unit and a post-processing
part which directly receives an output of the pre-processing part
and performs post-processing on the pre-processed color image; and
when the low-resolution image is to be generated, the color image
of one field selected by the field selecting unit is directly
transferred from the pre-processing part to the post-processing
part to thereby perform the pre-processing and the post-processing
integrally and sequentially.
4. The image capturing apparatus according to claim 3, wherein: the
image processing unit generates a first image lower in resolution
and a second image lower in resolution; and the field selecting
unit selects one field for generating the first image and one field
for generating the second image, respectively.
5. The image capturing apparatus according to claim 1, wherein: the
image processing unit includes a pre-processing part which performs
pre-processing on the color image output from the image capturing
unit, a post-processing part which performs post-processing on the
pre-processed color image, and a pixel averaging part which
directly receives an output of the post-processing part and
averages any pixels of the post-processed color image; and when the
low-resolution image is to be generated, a first low-resolution
image is generated by the post-processing part and the generated
first low-resolution image is directly transferred from the
post-processing part to the pixel averaging part to thereby
generate a second low-resolution image which is lower in resolution
than the first low-resolution image simultaneously.
6. The image capturing apparatus according to claim 1, wherein: the
image processing unit includes a white balance adjusting part; and
when the low-resolution image is to be generated, the white balance
adjusting part performs white balance adjustment in accordance with
a white balance adjustment value decided in advance.
7. The image capturing apparatus according to claim 1, wherein: the
image processing unit includes a pre-processing part which performs
pre-processing on the color image output from the image capturing
unit and a post-processing part which performs post-processing on
the pre-processed color image; the image capturing apparatus
further comprises a plurality of buffer memory areas which store
the color image pre-processed by the pre-processing part and a
high-speed continuous capturing mode which performs, as parallel
processing, a process of performing the pre-processing on the color
image of one frame output from the image capturing unit and storing
the pre-processed color image in one of the buffer memory areas and
a process of performing the post-processing on the color image of a
previous frame stored in another of the buffer memory areas; and
the image processing unit does not start generation of the
low-resolution image in a period of reading of fields other than
said one or more fields for generating the low-resolution image
while image capturing is executed in the high-speed continuous
capturing mode.
Description
CROSS REFERENCE TO THE RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from Japanese Patent Application No. 2007-332281, filed on
Dec. 25, 2007, the entire contents of which are incorporated herein
by reference.
BACKGROUND
[0002] 1. Field
[0003] The present application relates to an image capturing
apparatus which obtains an image by capturing an image of a
subject.
[0004] 2. Description of the Related Art
[0005] An electronic camera having an image sensor which separates
a captured image of a subject into fields and reads the fields has
been popularized. The applicant of the present invention has
already proposed an electronic camera as an invention described in
Japanese Unexamined Patent Application Publication No. 2004-135225.
The proposed electronic camera can shorten the capturing interval
by generating an image suited to be displayed on a display device
for checking a captured result (hereinafter referred to as "quick
view image") or an image suited for list display (hereinafter
referred to as "thumbnail image") before completion of reading of
all the fields.
[0006] The number of fields to be read however has increased with
the recent advance of increase in the number of pixels used in the
image sensor. For this reason, the time up to completion of reading
of all the fields has become longer. As a result, the user's
waiting time has become longer problematically.
SUMMARY
[0007] A proposition of the present embodiments is to use the
reading time from an image sensor efficiently.
[0008] To achieve the proposition, the image capturing apparatus
includes an image capturing unit which separates a color image of a
subject being captured by an image sensor having pixels of colors
into three or more fields and outputs said three or more fields
successively, and an image processing unit which generates a
low-resolution image which is lower in resolution than the color
image obtained by the image capturing unit, based on output of one
or more fields among said three or more fields, said one or more
fields being able to extract color information of all the colors,
wherein the image processing unit starts generation of the
low-resolution image in a period in which fields other than said
one or more fields for generating the low-resolution image are
read.
[0009] Incidentally, the low-resolution image is an image for
checking a result of capturing, and the image capturing apparatus
may further include a display unit which displays the
low-resolution image when the low-resolution image is generated by
the image processing unit.
[0010] The image capturing apparatus may further include a field
selecting unit which selects one field from the fields, wherein the
image processing unit includes a pre-processing part which performs
pre-processing on the color image output from the image capturing
unit and a post-processing part which directly receives an output
of the pre-processing part and performs post-processing on the
pre-processed color image, and when the low-resolution image is to
be generated, the color image of one field selected by the field
selecting unit is directly transferred from the pre-processing part
to the post-processing part to thereby perform the pre-processing
and the post-processing integrally and sequentially.
[0011] The image processing unit may generate a first image lower
in resolution and a second image lower in resolution, and the field
selecting unit may select one field for generating the first image
and one field for generating the second image, respectively.
[0012] The image processing unit may include a pre-processing part
which performs pre-processing on the color image output from the
image capturing unit, a post-processing part which performs
post-processing on the pre-processed color image, and a pixel
averaging part which directly receives an output of the
post-processing part and averages any pixels of the post-processed
color image, and when the low-resolution image is to be generated,
a first low-resolution image is generated by the post-processing
part and the generated first low-resolution image is directly
transferred from the post-processing part to the pixel averaging
part to thereby generate a second low-resolution image which is
lower in resolution than the first low-resolution image
simultaneously.
[0013] The image processing unit may include a white balance
adjusting part, and when the low-resolution image is to be
generated, the white balance adjusting part performs white balance
adjustment in accordance with a white balance adjustment value
decided in advance.
[0014] The image processing unit may include a pre-processing part
which performs pre-processing on the color image output from the
image capturing unit and a post-processing part which performs
post-processing on the pre-processed color image, the image
capturing apparatus may further include a plurality of buffer
memory areas which store the color image pre-processed by the
pre-processing part and a high-speed continuous capturing mode
which performs, as parallel processing, a process of performing the
pre-processing on the color image of one frame output from the
image capturing unit and storing the pre-processed color image in
one of the buffer memory areas and a process of performing the
post-processing on the color image of a previous frame stored in
another of the buffer memory areas, and the image processing unit
does not start generation of the low-resolution image in a period
of reading of fields other than said one or more fields for
generating the low-resolution image while image capturing is
executed in the high-speed continuous capturing mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a block diagram showing the configuration of an
electronic camera 1 according to an embodiment.
[0016] FIG. 2 is a view for explaining a Bayer arrangement.
[0017] FIG. 3 is a block diagram showing the details of an image
processing part 13.
[0018] FIG. 4 is a view for explaining a view operation.
[0019] FIG. 5 is a view for explaining a still image capturing
operation.
[0020] FIG. 6 is a flow of image data during the view
operation.
[0021] FIG. 7 is a diagram for explaining an image buffer of an
SDRAM 19.
[0022] FIG. 8 is a view for explaining generation of a main
image.
[0023] FIG. 9 is a flow of image data during the still image
capturing operation.
[0024] FIG. 10 is another diagram for explaining an image buffer of
the SDRAM 19.
[0025] FIG. 11 is another diagram for explaining an image buffer of
the SDRAM 19.
[0026] FIGS. 12A to 12D are timing charts showing still image
capturing sequences respectively.
[0027] FIGS. 13A and 13B are timing charts of an image signal
output of a CCD 11 during the still image capturing operation.
[0028] FIGS. 14A and 14B are views for explaining generation of a
quick view image.
[0029] FIG. 15 is a flow of data during generation of a quick view
image.
[0030] FIG. 16 is a flow of data during generation of a thumbnail
image.
[0031] FIG. 17 is another flow of data during generation of a quick
view image and a thumbnail image.
[0032] FIGS. 18A and 18B are other timing charts showing still
image capturing sequences respectively.
[0033] FIG. 19 is another flow of data during generation of a quick
view image and a thumbnail image.
[0034] FIG. 20 is another flow of data during generation of a quick
view image and a thumbnail image.
[0035] FIG. 21 is another flow of data during generation of a quick
view image and a thumbnail image.
[0036] FIG. 22 is a view for explaining a high-speed continuous
image capturing mode.
[0037] FIG. 23 is another diagram for explaining an image buffer of
SDRAM 19.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0038] Embodiments of the present invention will be described below
with reference to the drawings.
[0039] The configuration of an electronic camera 1 according to an
embodiment will be described first with reference to FIG. 1.
[0040] As shown in FIG. 1, the electronic camera 1 includes
respective parts, i.e. an image-capturing lens 10, a CCD 11, an AFE
(Analog Front End) 12, and an image processing part 13. The
image-capturing lens 10 includes a focus lens, a zoom lens, a lens
drive motor, etc. which are not shown. As shown in FIG. 2, the CCD
11 has a Bayer arrangement color filter. Incidentally, the CCD 11
is not limited to this example. The CCD 11 may have another filter
arrangement such as a stripe arrangement or may be replaced with
another image sensor than the CDD. An image of a subject captured
by the CCD 11 through the image-capturing lens 10 is transformed
into an image signal by the CCD 11. The image signal is output to
the AFE 12. The output image signal is converted into digital data
(hereinafter referred to as "image data") by the AFE 12. The image
data is output to the image processing part 13.
[0041] The electronic camera 1 further includes respective parts,
i.e. a TG (Timing Generator) 14, an MDIC (Motor Driver IC) 15, an
SIO (Serial Input/Output) 16, and a PIO (Parallel Input/Output) 17.
The TG 14 drives the CCD 11 and the AFE 12 to perform exposure,
image signal output, etc. The MDIC 15 drives the lens drive motor
of the image-capturing lens 10. The SIO 16 controls the TG 14 and
the MDIC 15. The PIO 17 controls the MDIC 15.
[0042] The electronic camera 1 further includes respective parts,
i.e. a JPEG compression part 18, an SDRAM 19, an SDRAM controller
20, an LCD 21, and a display controller 22. The JPEG compression
part 18 compresses and expands image data subjected to image
processing by the image processing part 13. The SDRAM 19
temporarily stores image data when the image data is subjected to
image processing or image compression. The SDRAM controller 20 is
an interface with the SDRAM 19. The LCD 21 displays image data and
various kinds of information. The display controller 22 controls
the LCD 21. Incidentally, the respective parts, i.e. the image
processing part 13, the JPEG compression part 18, the SDRAM
controller 20 and the display controller 22 are coupled to one
another by an image bus.
[0043] The electronic camera 1 further includes respective parts,
i.e. a memory card 23, a card I/F part 24, a USB I/F part 25 and a
clock generator 26, and a CPU 27. The memory card 23 is removable
and used for recording image data, etc. The card I/F part 24 is an
interface with the memory card 23. The USB I/F part 25 can be
coupled to a host PC, etc. The clock generator 26 supplies
operating clocks to the respective parts. The CPU 27 controls the
respective parts. Incidentally, the respective parts, i.e. the
image processing part 13, the SIO 16, the PIO 17, the JPEG
compression part 18, the SDRAM controller 20, the display
controller 22, the card I/F part 24, the USB I/F part 25, the clock
generator 26 and the CPU 27 are coupled to one another by a CPU
bus.
[0044] FIG. 3 is a block diagram showing the details of the image
processing part 13. As shown in FIG. 3, the image processing part
13 has a pre-processing part 30, and a post-processing part 31. The
pre-processing part 30 has respective parts, i.e. a defect
correcting part 32, an OB clamp processing part 33, a
sensitivity-ratio adjusting part 34, a 3A-evaluated value
calculating part 35, and an output buffer 36. The defect correcting
part 32 applies defect pixel correction to image data input from
the AFE 12. The OB clamp processing part 33 decides the black level
of the image data corrected by the defect correcting part 32. The
sensitivity-ratio adjusting part 34 corrects the signal levels of
R, G and B by applying sensitivity ratio adjustment to the image
data processed by the OB clamp processing part 33. The 3A-evaluated
value calculating part 35 calculates respective evaluated values of
AWB (Auto White Balance) in addition to the aforementioned AE and
AF based on the output of the sensitivity-ratio adjusting part 34.
Calculation results of the 3A-evaluated value calculating part 35
are output to the CPU 27 through the CPU bus. The output of the
sensitivity-ratio adjusting part 34 is output to the
post-processing part 31 and output to the image bus via the output
buffer 36.
[0045] The post-processing part 31 has respective parts, i.e. a
horizontal decimation part 40, a WB adjusting part 41, a .gamma.
correcting part 42, a color interpolating part 43, a color
converting & color correcting part 44, a resolution converting
part 45, a spatial filtering part 46, a CbCr decimation part 47, an
input buffer 48, and an output buffer 49.
[0046] The horizontal decimation part 40 reduces the number of
horizontal pixels by applying horizontal decimation to the image
data pre-processed by the pre-processing part 30. The WB adjusting
part 41 applies white balance adjustment to the image data
decimated by the horizontal decimation part 40, based on the AWB
evaluated value, etc. calculated by the 3A-evaluated value
calculating part 35. The .gamma. correcting part 42 applies .gamma.
correction to the image data white-balance-adjusted by the WB
adjusting part 41. The color interpolating part 43 generates image
data having three colors per pixel from Bayer arrangement image
data having one color per pixel by applying color interpolation to
the image data corrected by the y correcting part 42. The color
converting & color correcting part 44 generates image data in a
target color space (e.g. sRGB) by applying color conversion and
color correction to the image data interpolated by the color
interpolating part 43. The image data is generally image data with
YCbCr=4:4:4.
[0047] The resolution converting part 45 generates image data with
a target size by applying a resolution conversion process to the
image data corrected by the color converting & color correcting
part 44. For example, for a view operation which will be described
later, image data with a QVGA (320.times.240) size or a VGA
(640.times.480) size is generated. The spatial filtering part 46
applies a spatial filtering process to the image data converted by
the resolution converting part 45. Specifically, the spatial
filtering part 46 applies an edge emphasizing process to a Y signal
and applies a low-pass filtering process to color-difference
signals (a Cb signal and a Cr signal). The CbCr decimation part 47
applies a decimation process to color-difference signals (a Cb
signal and a Cr signal) to generate image data, for example, with
YCbCr=4:2:2 and output the image data to the output buffer 49. The
output of the output buffer 49 is coupled to the image bus. While
the output from the image bus is coupled to the input buffer 48,
the output of the input buffer 48 is coupled to the horizontal
decimation part 40 and the color converting & color correcting
part 44.
[0048] In the electronic camera 1 having the aforementioned
configuration, there are a view operation and a still image
capturing operation as capturing operations. The view operation is
an operation of generating and displaying a through image to check
a composition in real time. The still image capturing operation is
an operation of generating an image (hereinafter referred to as
"main image") by main image capturing.
[0049] In the view operation, a high frame rate (e.g. 30 fps) is
obtained because a decimated image signal is output from the CCD 11
as shown in FIG. 4. The view operation is suited for real-time
observation of a subject on the LCD 21, photometric measurement for
AE (Auto Exposure) or execution of AF (Auto Focusing).
[0050] On the other hand, in the still image capturing operation,
an image signal with all pixels is output from the CCD 1 1 as shown
in FIG. 5. Accordingly, the image signal is high in resolution and
is output in the condition that the image signal is separated into
a plurality of fields. Although FIG. 5 shows an example where 4
fields are output, the number of fields has a tendency toward
increase with the advance of increase in number of pixels used in
the CCD 11.
[0051] In the aforementioned view operation, post-processing due to
the post-processing part 31 can be directly applied to the image
data pre-processed by the pre-processing part 30 because adjacent
lines of an image signal are output sequentially from the CCD 11 as
shown in FIG. 4. That is, in the view operation, the pre-processing
part 30 inputs the pre-processed image data to the post-processing
part 31 directly. Then, the image data post-processed by the
post-processing part 31 is temporarily stored in the SDRAM 19 via
the image bus and the SDRAM controller 20. Further, the image data
from the SDRAM 19 passes through the SDRAM controller 20, the image
bus and the display controller 22 successively and is displayed as
a through image on the LCD 21.
[0052] On the other hand, in the aforementioned still image
capturing operation, an interpolating process or the like in the
post-processing due to the post-processing part 31 cannot be
executed because the image signal is output from the CCD 11 in the
condition that the image signal is separated into a plurality of
fields as shown in FIG. 5. For example, in a first field shown in
FIG. 5, a line n+4 is output next to a line n. Since lines n+1, n+2
and n+3 are inserted between the lines n and n+4, a process such as
color interpolation, resolution conversion or spatial filtering
using adjacent lines of image data cannot be applied to image data
of the first field. In the aforementioned still image capturing
operation, therefore, image data of the fields are pre-processed by
the pre-processing part 30 respectively, temporarily stored in the
SDRAM 19 and combined into a frame image on the SDRAM 19 and then
post-processed by the post-processing part 31.
[0053] FIG. 6 shows a flow of image data during the view operation.
The CPU 27 performs image processing along an arrow (1) and
displays a through image along an arrow (2). Incidentally, in order
to display the through image continuously, the two image buffers of
a V1 buffer 60 and a V2 buffer 61 as shown in FIG. 7 are prepared
so that the two image buffers are switched alternately every frame.
When a release button is half-pushed, the CPU 27 performs AE
operation using an AE evaluated value and AF using an AF evaluated
value based on the 3A-evaluated value calculating part 35 in
preparation for the still image capturing operation. When the
release button is full-pushed after it is half-pushed, the CPU 27
performs exposure for still image capturing based on a result of
the aforementioned AE operation after completion of AF and goes to
the still image capturing operation.
[0054] The exposure for still image capturing is terminated by the
closure of a mechanical shutter not shown, so that an image signal
separated into a plurality of fields as shown in FIG. 5 is output
from the CCD 11. While image data of each field is pre-processed by
the pre-processing part 30 and then stored in the SDRAM 19, the CPU
27 calculates an AWB evaluated value in the 3A-evaluated value
calculating part 35 in accordance with each field. When all the
pre-processed image data of the fields are stored in the SDRAM 19,
the CPU 27 sets a WB adjustment value obtained from the
aforementioned AWB evaluated values in the WB adjusting part 41.
Then, the CPU 27 reads image data stored in the SDRAM 19 in
(progressive) order of lines so that the image data is
post-processed by the post-processing part 31.
[0055] Incidentally, the three images of a quick view image for
checking capturing, a thumbnail image suited for list display and a
main image are generated in the still picture capturing. These
images are generated by post-processing the pre-processed image
data respectively. The size of the main image is so large that the
main image cannot be usually generated by one post-process.
Therefore, as shown in FIG. 8, the main image is generated in such
a manner that pre-processed image data is separated into narrow
strip blocks, each of the blocks is post-processed, and the
post-processed blocks are combined. However, the size of each
post-processed block is reduced because surrounding pixels are cut
off. Therefore, as shown in FIG. 8, boundary portions of adjacent
blocks are made to overlap with each other so that post-processed
images are combined correctly. Incidentally, when the main image is
to be generated, the horizontal decimation part 40 is generally
bypassed so that full-resolution pixels are fed to the post-stage.
On the other hand, the size of each of the quick view image and the
thumbnail image is small so that each of the quick view image and
the thumbnail image can be generated by one post-process (without
separation into strip blocks as described with reference to FIG. 8)
if it has been initially subjected to horizontal decimation.
[0056] A still picture capturing operation according to the related
art will be described first for the sake of comparison. FIG. 9
shows a flow of image data during the still image capturing
operation. The CPU 27 performs pre-processing along an arrow (1)
and performs post-processing along arrows (2) and (3). Each of the
pre-processing part 30 and the post-processing part 31 has one
image processing pipeline. Accordingly, each of the quick view
image, the thumbnail image and the main image is generated
sequentially. Each of the three images is stored in the SDRAM 19.
Incidentally, it is preferable that the quick view image is
generated first so that the user can check the contents of the
captured main image quickly. It is preferable that the thumbnail
image is then generated and the main image is finally generated.
This is because a general file format standard called Exif/DCF uses
data arrangement that the thumbnail image is recorded on a header
portion of a JPEG file and the main image is recorded on a tail
portion of the JPEG file. The CPU 27 displays image data of the
quick view image on the LCD 21 along an arrow (6).
[0057] The CPU 27 further records the thumbnail image and the main
image both in a JPEG compressed format. The CPU 27 performs JPEG
compression along arrows (4) and (5). Because one part is provided
as the JPEG compression part 18, compression of the thumbnail image
and compression of the main image are performed sequentially. In
this case, it is preferable that the thumbnail image and the main
image are compressed in this order. The CPU 27 combines compressed
data of the thumbnail image and compressed data of the main image
into one file on the SDRAM 19 in accordance with the Exif/DCF
format and records the file on the memory card 23 through the card
I/F part 24 along an arrow (7).
[0058] As described above, a plurality of data flows appear during
the still image capturing operation. Therefore, a plurality of
image buffers are prepared in the SDRAM 19 correspondingly to the
data flows. As shown in FIG. 10, the SDRAM 19 has respective image
buffers, i.e. an R buffer 62, a T buffer 63, an M buffer 64, a T-J
buffer 65, an M-J buffer 66, and a Q buffer 67.
[0059] As shown in FIG. 10, the CPU 27 stores pre-processed image
data in the R buffer 62. The image data stored in the R buffer 62
is post-processed so that image data of the thumbnail image thus
generated is stored in the T buffer 63. The image data stored in
the R buffer 62 is post-processed so that image data of the main
image thus generated is stored in the M buffer 64. The image data
stored in the T buffer 63 is JPEG-compressed by the JPEG
compression part 18 so that image data of the compressed image thus
generated is stored in the T-j buffer 65. The image data stored in
the M buffer 64 is JPEG-compressed by the JPEG compression part 18
so that image data of the compressed image thus generated is stored
in the M-J buffer 66. The image data stored in the T-J buffer 65
and the image data stored in the M-J buffer 66 are combined into
one file on one SDRAM 19 as described above, so that the file is
recorded on the memory card 23. In addition, the image data stored
in the R buffer 62 is post-processed so that image data of the
quick view image thus generated is stored in the Q buffer 67. The
image data stored in the Q buffer 67 is displayed on the LCD 21
through the display controller 22 as described above.
[0060] Although the data flow reaching the R buffer 62 is drawn as
one line in FIG. 10, a plurality of data flows as shown in FIG. 11
are actually provided because image data separated into fields as
shown in FIG. 5 are input to the R buffer 62 successively. As shown
in FIG. 11, the SDRAM 19 has respective image buffers, i.e. an R1
buffer 68, an R2 buffer 69, an R3 buffer 70 and an R4 buffer 71 in
place of the R buffer 62 shown in FIG. 10. These image buffers may
be configured so that the R buffers (R1 to R4) 62 of respective
fields have discrete addresses so that a one-frame image can be
read in (progressive) order of lines regardless of the number of
original fields. Image data of the fourth field is input to the R4
buffer. The CPU 27 starts post-processing due to the
post-processing part 31 after all image data of the four fields are
stored in the image buffers respectively.
[0061] FIG. 12A is a timing chart showing a sequence for capturing
a still image as described above. In FIG. 12A, "Q image", "T image"
and "M image" express a quick view image, a thumbnail image and a
main image respectively. As shown in FIG. 12A, outputting of an
image signal from the CCD 11 and pre-processing due to the
pre-processing part 30 are performed in parallel so that image data
of fields subjected to pre-processing are stored in the R buffers
(the R1 buffer 68 to the R4 buffer 71) successively. When image
data of all the fields are stored in the R buffers, post-processing
due to the post-processing part 31 is applied to the image data to
generate the three images of a quick view image, a thumbnail image
and a main image successively. Incidentally, the CPU 27 displays
the quick view image on the LCD 21 immediately after the CPU 27
generates the quick view image. Then, the CPU 27 applies JPEG
compression due to the JPEG compression part 18 to the thumbnail
image and the main image successively. Finally, the CPU 27 records
compressed data of the thumbnail image and compressed data of the
main image on the memory card 23 successively.
[0062] Incidentally, the thumbnail image and the main image are
generated successively and JPEG-compressed successively. Therefore,
when the thumbnail image is JPEG-compressed during generation of
the main image, and compressed data of the thumbnail image is
recorded during JPEG compression of the main image as shown in FIG.
12B, a plurality of processes can be executed while overlapping
with one another so that the total processing time (capturing time)
can be shortened. Further, when odd fields are read from the CCD
11, a low-resolution color image such as a quick view image or a
thumbnail image can be generated from image data of only one field
in parallel with outputting of an image signal from the CCD 11 as
described above in the Related Art (see FIG. 12C).
[0063] FIG. 12D is a timing chart showing a high-speed still image
capturing sequence obtained by combination of FIG. 12B and FIG.
12C. As shown in FIG. 12D, generation of a quick view image from
image data of only one field is performed in parallel with
outputting of an image signal from the CCD 11. Further, JPEG
compression of a thumbnail image is started in the middle of
generation of a main image. As a result, there is a large merit
that the quick view image and the thumbnail image can be generated
earlier.
[0064] Further, an example in which generation of only a quick view
image is performed in parallel with outputting of an image signal
from the CCD 11 is shown in FIGS. 12C and 12D. However, if the CCD
11 is of a 3-field output type, an image signal of the three fields
is output successively in synchronization with a vertical
synchronizing signal (VD signal) from the TG 14 as shown in FIG.
13A. Accordingly, when a quick view image is generated during
reading of the first or second field and a thumbnail image is
generated during reading of the second or third field, the
generation of the quick view image and the thumbnail image can be
completed before the outputting of the image signal of all the
fields from the CCD 11 is completed.
[0065] Incidentally, as described above, the time required for
completion of reading of all the fields from the CCD has become
longer with the advance of increase in number of fields to be read.
Therefore, in this invention, generation of the quick view image
and the thumbnail image is started earlier in order to use the
reading time efficiently.
[0066] FIGS. 14A and 14B are views for explaining generation of a
quick view image in this embodiment. FIG. 14A shows an example
where the CCD 11 is of a 3-field output type. FIG. 14B shows an
example where the CCD 11 is of a 4-field output type. When the CCD
11 is of a 3-field output type, one field contains all color signal
components (R, G and B) as shown in FIG. 14A. Accordingly, a quick
view image and a thumbnail image can be generated from image data
of only one field (the first field in the example shown in FIG.
14A). On the other hand, when the CCD 11 is of a 4-field output
type, each field lacks one color signal component as shown in FIG.
14B. For example, the first field does not contain any B signal,
and the second field does not contain any R signal. Therefore, in
such a case, a quick view image and a thumbnail image are generated
from image data of two fields (the first and second fields in the
example shown in FIG. 14B) from which all color information can be
extracted. Although all color information can be extracted from the
image signal of two fields in the example shown in FIG. 14B, a
smallest number of fields allowed to extract all color information
may be properly used for a CCD etc. using color filters containing
three or more color components.
[0067] For example, as shown in FIG. 13B, when the CCD 11 is of a
4-field output type, a quick view image and a thumbnail image can
be generated from image data of the first and second fields without
waiting for completion of outputting of an image signal of all the
fields from the CCD 11, at the point of time of completion of
outputting of an image signal of the second field. Accordingly, the
period of reading of the third and fourth fields can be used
efficiently.
[0068] On this occasion, it is preferable that generation of the
quick view image has priority over generation of the thumbnail
image. This is because the user can check capturing based on the
quick view image earlier while the quick view image can be used for
generating the thumbnail image. In comparison between an image
obtained by combining the first and second fields and a quick view
image generated from the image, the size (resolution) of the quick
view image is generally smaller (lower). Accordingly, when the
quick view image is generated first and used for generating the
thumbnail image, processing can be accelerated.
[0069] FIG. 15 shows a flow of data during generation of a quick
view image. As shown in FIG. 15, the CPU 27 reads image data of the
first and second fields stored in the SDRAM 19 (the R1 buffer 68
and the R2 buffer 69) while storing image data of the third and
fourth fields in the SDRAM 19 (the R3 buffer 70 and the R4 buffer
71). Then, the read image data of the first and second fields are
post-processed by the post-processing part 31 to generate a quick
view image.
[0070] FIG. 16 shows a flow of data during generation of a
thumbnail image from the quick view image generated by the data
flow of FIG. 15. As shown in FIG. 16, the CPU 27 reads image data
of the quick view image stored in the SDRAM 19 (the Q buffer 67)
and applies a reduction process, etc. due to the resolution
converting part 45 of the post-processing part 31 to the read image
data of the quick view image to thereby generate a thumbnail
image.
[0071] As described above with reference to FIGS. 15 and 16, even
when the quick view image and the thumbnail image are generated
sequentially, the total processing time can be shortened. When, for
example, the total reading time of the third and fourth fields is
required for generating the quick view image, the whole processing
is performed in the same timing as in FIG. 12C or 12D. When the
quick view image is generated in a shorter time, the total
processing time can be further shortened because generation of the
thumbnail image can be executed ahead of schedule. For example,
this can be achieved when the frequency of processing clocks
concerned with the post-processing part 31 is set at a high
frequency. When generation of the quick view image is completed at
an early timing of the reading period of the fourth field,
generation of the thumbnail image can be completed before an end of
the reading period of the fourth field. In this case, generation of
the thumbnail image from the quick view image as described above
with reference to FIG. 16 is effective.
[0072] On the other hand, as described above with reference to FIG.
13A, when the CCD 11 is of a 3-field output type, a quick view
image and a thumbnail image can be generated from image data of
only the first field. Accordingly, the reading period of the second
and third fields can be used efficiently. In this case, as
described above with reference to FIG. 15, the CPU 27 reads image
data of the first field stored in the SDRAM 19 (the R1 buffer 68)
and applies post-processing due to the post-processing part 31 to
the read image data of the first field to generate a quick view
image and a thumbnail image.
[0073] As described above with reference to FIG. 14A, when one
filed contains all color signal components (R, G and B), generation
of a quick view image and a thumbnail image by a data flow shown in
FIG. 17 can make processing more efficient. That is, as shown in
FIG. 17, the CPU 27 transfers image data of one field pre-processed
by the pre-processing part 30 from the pre-processing part 30 to
the post-processing part 31 directly. Then, the image data is
post-processed by the post-processing part 31 to generate a quick
view image. The quick view image is stored in the SDRAM 19 (the Q
buffer 67).
[0074] The same processing as in the data flow during the view
operation shown in FIGS. 6 and 7 can be made to transfer image data
from the pre-processing part 30 to the post-processing part 31
directly. A plurality of quick view images are however generated
when image data is simply transferred from the pre-processing part
30 to the post-processing part 31 directly. A field selecting unit
for selecting one of the fields is therefore provided so that image
data of only one field set by the field selecting unit in advance
can be directly transferred to the post-processing part 31 to
thereby generate one quick view image. According to this
configuration, the image processing part 13 performs control
automatically (without necessity of the CPU 27's controlling the
operation/suspension of the post-processing part 31) to operate the
post-processing part 31 in the reading period of only one selected
field but suspend the post-processing part 31 in the reading period
of the other fields.
[0075] Because a reduction process is generally performed when a
quick view image is generated, the horizontal decimation part 40
can be used efficiently in the same manner as in the view operation
described above with reference to FIGS. 6 and 7. On the other hand,
image data of all the fields pre-processed by the pre-processing
part 30 must be stored in the SDRAM 19 so that a high-resolution
main image can be generated afterward. As shown in FIG. 17, there
are hence provided two data flows corresponding to the quick view
image output from the post-processing part 31 and the image data
output from the pre-processing part 30.
[0076] According to the configuration described with reference to
FIG. 17, it is possible to expect a merit of generating the quick
view image in real time and a merit of reducing data traffic on the
SDRAM 19. For example, if generation of the quick view image is
completed in the reading period of the first field in FIG. 13A, two
reading periods of the second and third fields are free
sufficiently to generate the thumbnail image. In this case, the
thumbnail image can be generated from the quick view image as
described above with reference to FIG. 16. When the thumbnail image
is generated from the quick view image, completion of generation of
the thumbnail image in the reading period of the second field can
be achieved. That is, the processing time can be shortened as shown
in a timing chart of FIG. 18A. When the processing clock is further
adjusted appropriately, processing such as starting or terminating
compression of the thumbnail image in the reading period of the
third field can be performed further ahead of schedule.
[0077] Instead of generation of the thumbnail image from the quick
view image as described above with reference to FIG. 16, there may
be used a method in which the quick view image is generated from
the image data of the first field in the reading period of the
first field and the thumbnail image is then generated from the
image data of the second field in the reading period of the second
field. In this case, the field used for generating the quick view
image and the field used for generating the thumbnail image can be
set respectively by the aforementioned selection unit. According to
this configuration, the processing time can be shortened at the
same level as that in the case where the thumbnail image is
generated from the quick view image.
[0078] Alternatively, configuration may be made so that the quick
view image and the thumbnail image are generated simultaneously in
parallel. In most cases, the size of the quick view image is a QVGA
(320.times.240) size or a VGA (640.times.480) size. On the other
hand, the size of the thumbnail image is defined as a standard
(160.times.120) size in the Exif/DCF format. It is found from size
comparison between the quick view image and the thumbnail image
that the standard thumbnail image (160.times.120) in the Exif/DCF
format can be generated if the size of the quick view image is
reduced to "1/N" times (in which N is an integer). It is a matter
of course that this good compatibility is effective in the case
where the thumbnail image is generated from the quick view image as
described above with reference to FIG. 16. On the other hand, the
size reduction process is equivalent to a process of calculating an
average of pixel values in a block "N pixels" (horizontal) by "N
pixels" (vertical). Therefore, a bit shift technique which is a
known technique can be used for generating the quick view image and
the thumbnail image simultaneously in parallel. Specifically, 2
bits are shifted to the right for "1/4" times (N=4) and 1 bit is
shifted to the right for "1/2" times (N=2). Because such a circuit
for calculating an average of pixels has a very simple structure,
increase in cost and power consumption caused by the provision of
this circuit is allowable.
[0079] Therefore, as shown in a data flow of FIG. 19, a pixel
averaging part 50 is provided in the rear of the post-processing
part 31. Post-processed image data is input from the
post-processing part 31 to the pixel averaging part 50 directly.
FIG. 19 shows an example where the CCD 11 is of a 4-field output
type. When the quick view image has been generated in the
post-processing part 31, the pixel averaging part 50 calculates an
average of pixel values in a block 4 pixels (horizontal) by 4
pixels (vertical) (16 pixels in total) in the quick view image
(i.e. increases an integrated value of 16 pixels by 1/16 times
(4-bit shift)) or calculates an average of pixel values in a block
2 pixels (horizontal) by 2 pixels (vertical) in the quick view
image (4 pixels in total) (i.e. increase an integrated value of 4
pixels by 1/4 times (2-bit shift)). Then, the pixel averaging part
50 outputs the average as the value of one pixel of the thumbnail
image.
[0080] Then, the CPU 27 stores image data of the quick view image
generated by the post-processing part 31 in the SDRAM 19 (the Q
buffer 67) and stores image data of the thumbnail image generated
by the pixel averaging part 50 in the SDRAM 19 (the T buffer 63).
That is, the processing time can be shortened as shown in a timing
chart of FIG. 18B.
[0081] Although the averaging process executed by the pixel
averaging part 50 is effective for generating the quick view image
from image data of one field, the averaging process is particularly
effective for generating the quick view image from image data of
two or more fields. The start of generation of the quick view image
from image data of two or more fields is always delayed compared
with the start of generation of the quick view image from image
data of one field. The delay can be however compensated when the
quick view image and the thumbnail image are generated
simultaneously as described above. For example, when the CCD 11 is
of a 4-field output type, generation of the quick view image can be
started at the point of time of completion of outputting of the
image signal of the second field and generation of the thumbnail
image can be started at the same time as described above with
reference to FIG. 13B. Accordingly, both the quick view image and
the thumbnail image can be generated before the reading period of
all the fields is terminated.
[0082] To further improve the processing speed for generating the
quick view image from image data of two or more fields, image data
reduced for the quick view image in advance (i.e. low-resolution
RAW data) may be stored in the SDRAM 19. That is, as shown in a
data flow of FIG. 20, while image data of all fields pre-processed
by the pre-processing part 30 are stored in the SDRAM 19 (the R1
buffer 68 to the R4 buffer 71), image data of fields used for
generating the quick view image are transferred from the
pre-processing part 30 to the post-processing part 31 directly,
size-reduced by the post-processing part 31 and stored in the SDRAM
19 (a Q-R1 buffer 82 and a Q-R2 buffer 83). In this case, a
reduction ratio for the size reduction process in the horizontal
decimation part 40 in the post-processing part 31 is set so that an
image slightly larger than the quick view image can be
obtained.
[0083] Then, the horizontally size-reduced image data of the first
and second fields are stored in the SDRAM 19 (the Q-R1 buffer 82
and the Q-R2 buffer 83) via the output buffer 49. Therefore,
configuration is made so that the output of the horizontal
decimation part 40 can be connected to the output buffer 49.
Although the horizontal size reduction permits the quick view image
to be generated at a high speed, combination of the horizontal size
reduction and vertical size reduction permits the quick view image
to be generated at a higher speed when the total number of first
and second field lines is considerably larger than the number of
lines in the quick view image (e.g. when the total number of first
and second field lines is larger than twice as large as the number
of lines in the quick view image).
[0084] The data stored in the Q-R1 and Q-R2 buffers 82 and 83 in
FIG. 20 are Bayer arrangement image data. The color arrangement in
one field is however common to all the lines as described above
with reference to FIG. 14B. Accordingly, even when, for example,
the lines added up in FIG. 14B are first field lines n and n+4 or
second field lines n+1and n+5, the color arrangement is unchanged.
That is, this is the same as the case where two lines are added up
as described in the view operation in FIG. 4. Accordingly, the
aforementioned 10 vertical size reduction can be achieved by use of
line averaging (addition and division). A line memory is however
required when the line averaging is performed by both addition and
division. That is, image data of one line horizontally size-reduced
by the horizontal decimation part 40 is stored in the line memory
so that vertical size reduction can be performed by calculation of
an average (addition and division due to bit shift) of the image
data and image data of the next line horizontally size-reduced in
the same manner as described above.
[0085] Generally, the time required for image processing is
proportional to the size of an image which is a subject of image
processing. Therefore, the processing time can be shortened when
the quick view image is generated from the low-resolution RAW data
(reduced Bayer arrangement image data) as described above with
reference to FIG. 20. Incidentally, if it is difficult to provide
the aforementioned line memory, the quick view image can be
generated at a high speed because even horizontal size reduction
executed by the horizontal decimation part 40 can dispense with the
separation of image data into strip blocks as shown in FIG. 8 in
addition to reduction in number of horizontal pixels.
[0086] A data flow shown in FIG. 21 which is a modification of FIG.
20 is effective likewise. That is, as shown in FIG. 21, a quick
view image is generated first and then a thumbnail image is
generated from the quick view image. In this case, the processing
time becomes longer than that in the data flow shown in FIG. 20.
Elongation of the processing time can be however suppressed because
the thumbnail image is generated from the quick view image. In
addition, increase of hardware can be suppressed because it is
unnecessary to provide any new structure such as a pixel averaging
circuit.
[0087] Alternatively, the following measures may be taken in
consideration of accuracy in white balance adjustment executed by
the WB adjusting part 41 of the post-processing part 31. As
described above with reference to FIG. 3, it is necessary to set an
appropriate WB adjustment value in the WB adjusting part 41 when
image data is post-processed by the post-processing part 31. White
balance adjustment is an adjusting process for reproducing an
appropriate color by correcting change of the color temperature of
illuminating light on a subject when the color temperature changes.
For the white balance adjustment, the CPU 27 sets the WB adjusting
part 41 at the WB adjustment value obtained from the AWB evaluated
value calculated by the 3A-evaluated value calculating part 35 as
described above with reference to FIG. 3. In the view operation in
which a through image is displayed on the LCD 21, the AWB evaluated
value is updated at a constant rate (e.g. at a rate of 30 fps) in
accordance with new image data which is continuously input to the
pre-processing part 30. Generally, it is unnecessary to change the
WB adjustment value frequently because the color temperature of
illuminating light does not change rapidly. Accordingly, in the
view operation, the WB adjustment value can be updated at a
moderate rate.
[0088] On the other hand, in the still image capturing operation in
which a still image is generated, the WB adjustment value is
obtained based on the AWB evaluated value generally extracted from
image data per se of the still image because the still image is an
independent image of one frame. However, if the WB adjustment value
is obtained based on the AWB evaluated value extracted from image
data per se of a quick view image or a thumbnail image to be
generated, generation of the quick view image or the thumbnail
image is delayed. It is therefore preferable that the WB adjustment
value used for generating the quick view image or the thumbnail
image is decided in advance. For example, the WB adjustment value
may be the latest WB adjustment value used in the view operation
just before or may be obtained, as a WB adjustment value
corresponding to the color temperature of illuminating light, from
a database in the electronic camera 1 if the color temperature of
illuminating light can be found in advance (e.g. as in flash
photography). Then, the CPU 27 performs white balance adjustment
due to the WB adjusting part 41 in accordance with the WB
adjustment value decided in advance.
[0089] However, if the WB adjustment value can be calculated based
on the AWB evaluated value at a high speed, the WB adjustment value
may be obtained based on the AWB evaluated value extracted from
image data per se of the quick view image or the thumbnail image to
be generated. For example, when the CCD 11 is of a 3-field output
type as described above with reference to FIG. 13A, an AWB
evaluated value is extracted from image data of the first field in
the reading period of the first field, a WB adjustment value is
calculated based on the AWB evaluated value extracted in the
reading period of the first field, in the reading period of the
second field, and a quick view image is finally generated in the
reading period of the third field. Because it is conceived that
there is a high correlation between the respective fields, there is
no large problem when the quick view image is generated from image
data of the third field based on the AWB evaluated value extracted
in the reading period of the first field.
[0090] On the other hand, for example, when the CCD 11 is of a
4-field output type as described above with reference to FIG. 13B,
an AWB evaluated value is extracted from image data of the first
and second fields in the reading period of the first and second
fields, a WB adjustment value is calculated based on the AWB
evaluated value extracted in the reading period of the first and
second fields, in the reading period of the third field, and a
quick view image and a thumbnail image are generated in the reading
period of the fourth field. Incidentally, when a long time is
required for calculating the WB adjustment value, the WB adjustment
value may be calculated in the reading period of the third and
fourth fields so that the quick view image and the thumbnail image
can be generated simultaneously after final reading of the fourth
field is completed. Although the quick view image and the thumbnail
image cannot be generated in the period of reading of an image
signal from the CCD 11, the total processing time can be shortened
because the WB adjustment value can be calculated ahead of
schedule. In this case, processing may be made in accordance with
the data flow described with reference to FIG. 20.
[0091] Exceptional processing will be described below when the
electronic camera 1 has a high-speed continuous capturing mode. As
shown in FIG. 22, the high-speed continuous capturing mode is a
capturing mode where capturing of one frame of the latest still
image is made in parallel with image processing (post-processing)
of a previous frame, in parallel with JPEG compression of a further
previous frame and in parallel with recording of a further previous
frame. In the high-speed continuous capturing mode, the three
images of a quick view image, a thumbnail image and a main image
are generated in image processing (post-processing), the thumbnail
image and the main image are compressed in JPEG compression
processing, and compressed data of the thumbnail image and the main
image are recorded in recording processing. That is, in each step,
images are processed in parallel.
[0092] It is necessary to provide a plurality of image buffers so
that the four steps shown in FIG. 22 can overlap with one another.
For example, as shown in FIG. 23, an R1 buffer 68 and an R2 buffer
69 are provided in place of the R buffer 62 shown in FIG. 10, and a
Q1 buffer 72 and a Q2 buffer 73 are provided in place of the Q
buffer 67 shown in FIG. 10. Moreover, a T1 buffer 74 and a T2
buffer 75 are provided in place of the T buffer 63 shown in FIG.
10, and an M1 buffer 76 and an M2 buffer 77 are provided in place
of the M buffer 64 shown in FIG. 10. In addition, a T-J1 buffer 78
and a T-J2 buffer 79 are provided in place of the T-J buffer 65
shown in FIG. 10, and an M-J1 buffer 80 and an M-J2 buffer 81 are
provided in place of the M-J buffer 66 shown in FIG. 10. That is,
as shown in FIG. 23, all the image buffers are doubled. With the
configuration of the SDRAM 19, the four steps described with
reference to FIG. 22 can overlap with one other perfectly.
Incidentally, each step includes smaller sub-steps which are
executed sequentially.
[0093] In execution of image capturing in the high-speed continuous
capturing mode described above, outputting of an image signal
corresponding to one frame of the latest still image from the CCD
11 is performed in parallel with image processing (post-processing)
of a previous frame performed by the post-processing part 31.
Accordingly, a quick view image or a thumbnail image corresponding
to one frame of the latest still image cannot be generated in
parallel with the outputting of the image signal from the CCD 11.
Therefore, in execution of image capturing in the high-speed
continuous capturing mode, generation of the quick view image and
the thumbnail image is not started during outputting of the image
signal from the CCD 11. The quick view image and the thumbnail
image are generated collectively and subsequently. In this case,
the processing time of each step becomes longer than that in image
capturing in a single capturing mode but the total processing time
can be shortened because new frames are captured successively. When
it is difficult to provided doubled image buffers as shown in FIG.
23 in terms of memory capacity, etc., at least the R buffer may be
doubled (as an R1 buffer 68 and an R2 buffer 69) so that image
capturing of the next frame can be continued.
[0094] An example of combination of the aforementioned processes
will be described finally. When the CCD 11 is configured so that
the reading mode can be switched in accordance with whether one
field contains all color signal components (R, G and B) or not,
processing modes corresponding to the respective cases may be
provided so that one of the processing modes selected in accordance
with switching of the reading mode can be executed. That is,
configuration may be made so that a quick view image and a
thumbnail image are generated from image data of one field when one
field contains all color signal components (R, G and B), whereas a
quick view image and a thumbnail image are generated from image
data of two or more fields when one field does not contain all
color image components (R, G and B). With this configuration,
optimum processing can be performed regardless of the configuration
of the CCD 11, the number of fields to be read and the switching of
the reading mode.
[0095] As described above, according to this embodiment, generation
of a low-resolution image is started in the reading period of
remaining one(s) of all fields except part of the fields.
Accordingly, the reading time from the image sensor can be used
efficiently.
[0096] Moreover, according to this embodiment, a display unit is
further provided for displaying an image for checking a result of
capturing as a lower-resolution image when the image is generated.
Accordingly, the waiting time of the user can be shortened.
[0097] Moreover, according to this embodiment, a field selecting
unit for selecting one of fields is further provided so that a
color image of one field selected by the field selecting unit to
generate a low-resolution image is transferred from the
pre-processing part to the post-processing part directly to thereby
unify pre-processing and post-processing. Accordingly, the
low-resolution image can be generated efficiently and quickly.
[0098] Moreover, according to this embodiment, a first
low-resolution image and a second low-resolution image are
generated in such a manner that the field selecting unit selects
either of a field used for generating the first image and a field
used for generating the second image. Accordingly, low-resolution
images can be generated sequentially and quickly without necessity
of adding any special configuration.
[0099] Moreover, according to this embodiment, for generation of
low-resolution images, a first image with a low resolution is
generated by the post-processing part and directly transferred from
the post-processing part to the image averaging part to thereby
simultaneously generate a second image with a lower resolution than
that of the first image. Accordingly, low-resolution images can be
generated efficiently and quickly.
[0100] Moreover, according to this embodiment, for generation of
the low-resolution images, the white balance adjusting part
performs white balance adjustment in accordance with a white
balance adjustment value decided in advance. Accordingly,
low-resolution images can be generated quickly while white balance
adjustment can be performed appropriately.
[0101] Moreover, according to this embodiment, a high-speed
continuous capturing mode is provided so that generation of any
low-resolution image is not started in the reading period of the
remaining fields during execution of image capturing in the
high-speed continuous capturing mode. Accordingly, the reading time
from the image sensor can be used efficiently regardless of the
image capturing mode.
[0102] Although the respective sub-steps are drawn in the timing
charts of FIGS. 12A to 12D and FIGS. 18A and 18B so as to have
equalized lengths for the sake of simplification in the
aforementioned embodiment, the lengths of the respective sub-steps
have no correlation with actual processing lengths. Generally, the
processing time required for processing such as image processing,
JPEG compression processing, data recording, etc. is proportional
to the amount of data used for the processing. That is, the longest
processing time is required for generation and JPEG compression
processing of the main image compared with generation of the quick
view image and the thumbnail image. With respect to JPEG
compression, the longest time is required for compression of the
main image. Accordingly, the three sub-steps of image processing
(post-processing), JPEG compression processing and data recording
are dedicated to processing of the main image so that reduction of
the image capturing time can be achieved. As described above in
this embodiment, generation of the quick view image and the
thumbnail image can be quickened to thereby achieve reduction of
the image capturing time.
[0103] When the quick view image which was heretofore used only for
checking image capturing is JPEG-compressed and recorded on the
memory card 23 while associated with the main image, the quick view
image can be displayed on the LCD 21 at the time of reproduction of
the main image. As a result, in comparison with the case where the
main image was heretofore size-reduced before displayed on the LCD
21, the waiting time of the user can be shortened in this case. In
this case, JPEG compression processing may be applied to the quick
view image as well as the main image. A private area (maker note
area) of Exif/DCF can be used for recording the quick view
image.
[0104] In JPEG compression processing, bit rate control has been
heretofore made to keep the size of data of one frame almost
constant. The bit rate control can keep the number of image
capturing frames constant in accordance with the recording capacity
of the memory card 23. There is however some case where JPEG
compression must be repeated several times under the bit rate
control, so that the image capturing time may become remarkably
long. It is therefore desired that the amount of data is brought
close to a target value while the number of times in repetition of
compression is reduced as sufficiently as possible. On this
occasion, the number of times in repetition of compression can be
reduced when a quantization table for JPEG compression of the main
image is decided with reference to information concerned with JPEG
compression of the quick view image or the thumbnail image
generated before the main image.
[0105] In each of the above-described embodiments, in the case of
using an image signal having minimum number of fields (for example,
2 fields in the embodiment) which can extract color information of
all the colors in the CCD to generate low-resolution images such as
quick view images. However, the present invention is not limited to
such an example. The number of the fields of the image signal which
is used for generating low-resolution images may be any numbers as
long as the number of the fields of the image signal is more than
the number of the minimum fields but less than the number of all
fields of the CCD.
[0106] The many features and advantages of the embodiments are
apparent from the detailed specification and, thus, it is intended
by the appended claims to cover all such features and advantages of
the embodiments that fall within the true spirit and scope thereof.
Further, since numerous modifications and changes will readily
occur to those skilled in the art, it is not desired to limit the
inventive embodiments to the exact construction and operation
illustrated and described, and accordingly all suitable
modifications and equivalents may be resorted to, falling within
the scope thereof.
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