U.S. patent application number 13/198960 was filed with the patent office on 2011-11-24 for digital image capture device and brightness correction method thereof.
This patent application is currently assigned to ALTEK CORPORATION. Invention is credited to Chan-Min Chou, Chung-Pin Lu.
Application Number | 20110285876 13/198960 |
Document ID | / |
Family ID | 42240057 |
Filed Date | 2011-11-24 |
United States Patent
Application |
20110285876 |
Kind Code |
A1 |
Chou; Chan-Min ; et
al. |
November 24, 2011 |
DIGITAL IMAGE CAPTURE DEVICE AND BRIGHTNESS CORRECTION METHOD
THEREOF
Abstract
A digital image capture device and a brightness correction
method thereof are described. The digital image capture device is
adapted to correct the brightness value of a shot object in a
digital image through the compensation of a strobe during shooting.
The method includes setting a shooting magnification of the digital
image capture device to the shot object; capturing a pre-shot image
at least including the image of the shot object; triggering a
strobe to emit a main flash onto the shot object, so as to shoot a
digital image; setting a plurality of light measuring areas in the
digital image; calculating a corresponding object distance of the
shot object from each of the light measuring areas; establishing a
shading table according to each of the object distances; and
loading the shading table to adjust the brightness value of each of
the light measuring areas in the digital image.
Inventors: |
Chou; Chan-Min; (Banciao
City, TW) ; Lu; Chung-Pin; (Taipei County,
TW) |
Assignee: |
ALTEK CORPORATION
Hsinchu
TW
|
Family ID: |
42240057 |
Appl. No.: |
13/198960 |
Filed: |
August 5, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12420703 |
Apr 8, 2009 |
|
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13198960 |
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Current U.S.
Class: |
348/234 ;
348/E9.053 |
Current CPC
Class: |
H04N 5/243 20130101;
H04N 5/2351 20130101; H04N 5/2354 20130101 |
Class at
Publication: |
348/234 ;
348/E09.053 |
International
Class: |
H04N 9/68 20060101
H04N009/68 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2008 |
TW |
097149268 |
Claims
1. A brightness correction method of a digital image capture
device, adapted to correct the brightness value of at least one
digital image during shooting, the method comprising: capturing a
digital image comprising at least one frame of a shot object;
setting a plurality of light measuring areas in the digital image,
and calculating a corresponding object distance of the shot object
from each of the light measuring areas to obtain a plurality of
object distances; loading a shading table according to the
plurality of object distances; and adjusting the brightness value
of each of the light measuring areas in the digital image according
to the shading table.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This non-provisional application claims priority under 35
U.S.C. .sctn.119(a) on Patent Application No(s). 097149268 filed in
Taiwan, R.O.C. on Dec. 17, 2008 the entire contents of which are
hereby incorporated by this reference and also claims priority
under 35 U.S.C. .sctn.120 to U.S. patent application Ser. No.
12/420,703 filed on Apr. 8, 2009, the entire contents of which are
hereby incorporated by this reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of Invention
[0003] The present invention relates to a digital image capture
device and a brightness correction method thereof, and more
particularly to a method for correcting the brightness value of a
shot object at different distances and a digital image capture
device thereof.
[0004] 2. Related Art
[0005] With the development of digital cameras, photography is no
longer an expensive consumption. Users may shoot desired images at
will to record a memorial moment or scene. Due to physical
properties, the lens set in the digital image capture device may
cause the problem of non-uniform brightness distribution during the
imaging of the shot object under the light source. In other words,
the center of the digital image is brighter than the periphery.
Meanwhile, if the strobe is used for compensating the brightness,
the non-uniform brightness distribution becomes even more apparent.
The reason is that the strobe reflects all the lights from the
light source onto the shot object through the reflecting plate, and
the strobe and the lens set are located at different positions, so
that the shot object is under varied impacts due to its distance
from the camera. If the digital image capture device is closer to
the shot object, the brightness distribution of the digital image
is increased, and vice versa. In order to solve the above problem
of brightness distribution, a shading table is provided, in which a
digital image is represented by a two-dimensional array and
brightness compensation is performed on the digital image through
digital gain.
[0006] FIG. 1 is a schematic flow chart of the prior art. A digital
image is pre-captured (Step S110). It is determined whether to turn
on a strobe or not (Step S120). If the strobe is shot, an emission
time of the strobe is estimated (Step S130). If the strobe is not
shot, the digital image is directly shot and a shading table is
loaded for adjusting the digital image (Step S140). If only a
shading table is applied to all the shooting environments, the
problem that the long-shot gain is too much while the close-shot
gain is insufficient may occur to the digital image at different
focusing object distances, and vice versa. In this manner, the
modified digital image appears unnatural.
SUMMARY OF THE INVENTION
[0007] Accordingly, to solve the above problem, the present
invention is mainly directed to a brightness correction method of a
digital image capture device, in which the brightness of a shot
object in a digital image is corrected when a strobe is used to
shoot the image.
[0008] In order to achieve the above objective, the present
invention provides a brightness correction method of a digital
image capture device, which includes capturing a pre-shot image at
least including an image of a shot object; triggering a strobe to
emit a main flash onto the shot object, so as to shoot a digital
image; setting a plurality of light measuring areas in the digital
image; calculating a corresponding object distance of the shot
object from each of the light measuring areas; establishing a
shading table according to each of the object distances; and
loading the shading table to adjust the brightness of each of the
light measuring areas in the digital image.
[0009] In another aspect, the present invention is further directed
to a brightness correction method of a digital image capture
device, which is adapted to correct the brightness of a shot object
in a digital image shot by using a strobe.
[0010] In order to achieve the above objective, the present
invention provides a brightness correction method of a digital
image capture device, which includes capturing a digital image
including at least one frame of a shot object; setting a plurality
of light measuring areas in the digital image, and calculating a
corresponding object distance of the shot object from each of the
light measuring areas; loading a corresponding shading table
according to the corresponding object distance of the shot object
in each of the light measuring areas; and adjusting the brightness
value of each of the light measuring areas in the digital image
according to the shading table.
[0011] In still another aspect, the present invention is directed
to a digital image capture device with brightness correction, which
is adapted to correct the brightness of a shot object in a digital
image shot by using a strobe.
[0012] In order to achieve the above objective, the present
invention provides a digital image capture device with brightness
correction, which includes a lens set, a strobe, a light sensing
element, a storage unit, and a processing unit. The lens set is
used to adjust a focal length of a shot object. The light sensing
element is electrically connected to the lens set, for receiving an
image signal of the shot object through the lens set. The storage
unit is electrically connected to the light sensing element, for
storing the digital image received by the light sensing element and
a shading table. The processing unit is electrically connected to
the strobe, the light sensing element, and the storage unit, for
adjusting an output value of the strobe according to the shading
table established through pre-shooting.
[0013] As described above, the present invention provides a method
for correcting the brightness of a digital image and a digital
image capture device thereof based on different light measuring
areas in the digital image. According to the distances from the
light measuring areas to the shot object, the digital image capture
device respectively sets a dedicated brightness correction value
for each light measuring area and records the brightness correction
values to a shading table. Directing to shot objects with different
distances/shooting magnifications, the shading table with the
corresponding distance is loaded to prevent over-exposure of some
areas of the digital image when a single gain value is employed to
compensate the whole digital image.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention will become more fully understood from
the detailed description given herein below for illustration only,
and thus are not limitative of the present invention, and
wherein:
[0015] FIG. 1 is a schematic view of a conventional brightness
adjustment method;
[0016] FIG. 2 is a schematic architectural view of the present
invention;
[0017] FIG. 3A is a schematic flow chart of the operation of the
present invention;
[0018] FIG. 3B is a schematic view of an implementation aspect with
different object distances;
[0019] FIG. 3C is a schematic view of an implementation aspect with
different object distances;
[0020] FIG. 3D is a flow chart of the loading operation of a
shading table;
[0021] FIG. 4 is a schematic view of a digital image with light
measuring areas; and
[0022] FIG. 5 is a schematic curved diagram showing the
relationship between a brightness correction value and a distance
of a shot object.
DETAILED DESCRIPTION OF THE INVENTION
[0023] FIG. 2 is a schematic architectural view of the present
invention. The digital image capture device 200 of the present
invention includes a lens set 210, a strobe 220, a light sensing
element 230, a storage unit 240, and a processing unit 250. The
lens set 210 is used to adjust a focal length and a zoom ratio of a
shot object. The light sensing element 230 is electrically
connected to the lens set 210, for receiving an image signal of the
shot object through the lens set 210. The storage unit 240 is
electrically connected to the light sensing element 230, for
storing the digital image received by the light sensing element 230
and a shading table 241. The processing unit 250 is electrically
connected to the strobe 220, the light sensing element 230, and the
storage unit 240, for adjusting an output value of the strobe 220
according to the shading table 241 established through
pre-shooting.
[0024] In order to explicitly describe the operation of the present
invention, a schematic flow chart of the operation of the present
invention is shown in FIG. 3A, and the operation of the present
invention includes the following steps.
[0025] A pre-shot image at least including an image of a shot
object is captured (Step S310).
[0026] A strobe is triggered to emit a main flash onto the shot
object, so as to shoot a digital image (Step S320).
[0027] A plurality of light measuring areas is set in the digital
image (Step S330).
[0028] A corresponding object distance of the shot object is
obtained from each of the light measuring areas (Step S340). A
brightness difference value between the reflection level of the
shot object and the pre-shot image in the digital image is obtained
when the strobe is triggered to shoot the object. Then, the object
distance of the shot object in each of the light measuring areas is
determined according to the brightness difference value.
[0029] A shading table is established according to each of the
object distances (Step S350).
[0030] Finally, the brightness value of each of the light measuring
areas in the digital image is adjusted according to the shading
table (Step S360).
[0031] In order to explicitly describe the establishment of the
shading table, the following method is provided, and the present
invention is not limited thereto. FIGS. 3B and 3C are schematic
views of implementation aspects with different object distances.
Both in FIGS. 3B and 3C, a wall is shot. In FIG. 3B, an object
distance between the digital image capture device and the wall is
d1, and in FIG. 3C, an object distance between the digital image
capture device and the wall is d2. Several digital images are shot
at different object distances (for example, at an interval of 30
cm). Then, a shading table is established according to the
decreasing level from the center to the periphery of the digital
image with different object distances. Besides the above method of
shooting a planar wall for establishing a shading table, images of
persons or articles at different object distances may also be shot
to establish a shading table.
[0032] During shooting, the digital image capture device loads in
the shading table at a suitable time according to the current
object distance of the shot object, so as to compensate the
brightness of the shot object. FIG. 3D is a flow chart of the
loading operation of the shading table, including the following
steps.
[0033] In Step S410, a digital image including at least one frame
of a shot object is captured.
[0034] In Step S420, a plurality of light measuring areas is set in
the digital image, and a corresponding object distance of the shot
object is calculated from each of the light measuring areas.
[0035] In Step S430, a corresponding shading table is loaded
according to the corresponding object distance of the shot
object.
[0036] In Step S440, the brightness value of each of the light
measuring areas in the digital image is adjusted according to the
shading table.
[0037] FIG. 4 is a schematic view of a digital image with light
measuring areas. The number and coverage of the light measuring
areas are not limited to the aspect in FIG. 4. The compensation
ratio of each of the light measuring areas (indicated by dotted
line frames 520 in FIG. 4) in the digital image (indicated by a
solid line frame 510 in FIG. 4) is determined according to the
distance between the light measuring area in the center and the
light measuring areas on the periphery as well as the brightness
differences there-between. For example, the farther the shot object
is, the higher the brightness correction value will be, and vice
versa. FIG. 5 is a schematic curved diagram showing the
relationship between the brightness correction value and the
distance of the shot object. The distance of the shot object, the
brightness difference, and the compensation ratio are in positive
correlation. That is, the farther the shot object is, the greater
the brightness difference will be, so that the compensation ratio
of the shot object is also increased.
[0038] In order to explicitly describe the operation of the present
invention, the following implementation aspect is used for
illustration. First, the digital image capture device 200 focuses
on a first shot object and captures a pre-shot image. Then, the
digital image capture device 200 triggers the strobe 220 and shoots
a digital image. The output of the strobe is set at the main flash.
The digital image capture device 200 estimates the object distance
of the first shot object to the digital image capture device 200
according to the reflecting strength of the strobe 220 to the shot
object. The digital image capture device 200 further divides the
captured digital image into a plurality of light measuring areas.
In the present invention, the central and surrounding light
measuring areas are taken as an example. Other implementation
aspects are already known to those skilled in the art, so the
details will not be described herein again.
[0039] The digital image capture device 200 estimates the distance
from the central light measuring area to the first shot object, and
generates a light metering compensation value corresponding to the
central light measuring area. Then, the digital image capture
device 200 estimates the distances of other neighboring light
measuring areas, and records the corresponding light metering
compensations, respectively. The light measuring compensation
values of the central and neighboring light measuring areas are
estimated according to the distances from the shot object by means
of interpolation calculation, as shown in FIG. 5. Moreover, in the
present invention, after each of the light measuring areas is shot,
a brightness correction value of each light measuring area is set
correspondingly. After setting the brightness correction value of
each of the light measuring areas, the brightness correction values
are recorded in a shading table 241. In other words, the digital
image capture device 200 calculates the corresponding shading table
241 at different object distances.
[0040] Afterward, the digital image capture device 200 shoots a
second object, and repeats the above operations of setting a
brightness correction value and establishing a shading table 241.
The digital image capture device establishes the corresponding
shading table 241 for different shot objects, so as to load in the
corresponding shading table 241 directing to the shot objects with
different distances/shooting magnifications.
[0041] The present invention provides a method for correcting the
brightness of a digital image based on different light measuring
areas in the digital image. According to the distances from the
light measuring areas to the shot object, the digital image capture
device 200 respectively sets a dedicated brightness correction
value for each light measuring area and records the brightness
correction values to a shading table 241. Directing to shot objects
with different distances/shooting magnifications, the shading table
241 with the corresponding distance is loaded to prevent
over-exposure of some areas of the digital image when a single gain
value is employed to compensate the whole digital image.
* * * * *