Digital Camera Patent Abstract
A method of detecting motion is described. A first image is captured
and exposed by a digital camera. The first image information is
transferred to a control device. Gray level values of a specific
group in the first image are then stored. Real-time gray level values
corresponding to the specific group in a real time image are subsequently
captured. The real-time gray level values of the specific group
in a real time image are compared with the gray level values of
the specific group in the first image. An amount of specific points
with different gray level between the specific groups in the real-time
image and the first image greater than N indicates an object of
the real-time image is in motion or else the object of the real-time
image is motionless. A sequential step for the object detected to
be in motion is then performed. The real-time gray level values
of the specific group in the real-time image are stored as the gray
level values of the specific group in the first image. Digital Camera Patent Claims
What is claimed is:
1. A method of detecting motion for digital camera, said method
comprising the steps of: storing gray level values of a specific
group in a first image; capturing real-time gray level values corresponding
to said specific group in a real-time image; comparing said real-time
gray level values of said specific group in said real-time image
with said gray level values of said specific group in said first
image; determining whether gray level differences between said specific
groups in said real-time image and said first image are greater
than a predetermined threshold value, wherein said gray level differences
greater than said threshold value indicate an object of said real-time
image is in motion or else no motion is occurring in the real-time
image; performing a sequential step for the object detected to be
in motion when said gray level value differences are greater than
said threshold value; storing said real-time gray level values of
said specific group in said real-time image as said gray level values
of said specific group in said first image; setting a parameter
F equal to 1 when the object of said real-time image is determined
to be in motion; setting said parameter F equal to 0 when the object
of said real-time image is determined to be motionless; checking
said parameter F; sequentially performing the motion detection steps
when said parameter F is equal to 0; and stopping motion detection
steps for a predetermined time when said parameter F is equal to
1 and resetting said parameter F equal to 0 to continue the motion
detection steps.
2. The method according to claim 1, wherein said specific group
substantially includes one or a plurality of specific points selected
from said images.
3. The method according to claim 2, wherein said specific points
are uniformly distributed over entire image.
4. The method according to claim 2, wherein said specific points
are partially concentrated on a central portion of entire image
for enhancing detecting efficiency of the central portion of entire
image.
5. The method according to claim 2, wherein an amount of said specific
points is adjustable depending on the detecting efficiency.
6. The method according to claim 1, wherein the step of determining
whether gray level differences between said specific groups in said
real-time image and said first image are greater than a predetermined
threshold value further comprises: subtracting said gray level values
of said specific group in said first image from said real-time gray
level values of said specific group in said real-time image to generate
a plurality of gray level differences of said corresponding specific
groups; and determining whether said gray level differences are
greater than said predetermined threshold value; wherein any one
of said gray level differences being greater than said predetermined
threshold value indicates the object of said real-time image is
in motion.
7. The method according to claim 6, wherein said threshold value
is adjustable for changing a detection sensitivity of the digital
camera.
8. The method according to claim 1, wherein said sequential step
comprises taking photos, taking a motion picture, sounding an alarm,
or flashing a LED light to warn a system operator or a guard.
9. A method of detecting motion for a digital camera, said method
comprising the steps of: storing gray level values of a specific
group in a first image; capturing real-time gray level values corresponding
to said specific group in a real-time image; comparing said real-time
gray level values of said specific group in said real-time image
with said gray level values of said specific group in said first
image; determining whether an amount of specific points with different
gray levels between said specific groups in said real-time image
and said first image is greater than N, wherein the amount of specific
points with different gray levels greater than N indicates an object
of said real-time image is in motion or else no motion in the real-time
image; performing a sequential step for the object detected to be
in motion when the amount of specific points with different gray
levels is greater than N; and storing said real-time gray level
values of said specific group in said real-time image as said gray
level values of said specific group in said first image; setting
a parameter F equal to 1 when the object of said real-time image
is determined to be in motion; setting said parameter F equal to
0 when the object of said real-time image is determined to be motionless;
checking said parameter F; sequentially performing the motion detection
steps when said parameter F is equal to 0; and Stopping motion detection
steps for a predetermined time when said parameter F is equal to
1 and resetting said parameter F equal to 0 to continue the motion
detection steps.
10. The method according to claim 9, wherein said specific group
substantially includes one or a plurality of said specific points
selected from said images.
11. The method according to claim 10, wherein said specific points
are uniformly distributed over entire image.
12. The method according to claim 10, wherein said specific points
are partially concentrated on a central portion of entire image
for enhancing detection efficiency of the central portion of entire
image.
13. The method according to claim 10, wherein an amount of said
specific points is adjustable depending on the detection efficiency.
14. The method according to claim 9, wherein the step of determining
whether an amount of specific points with different gray levels
between said specific groups in said real-time image and said first
image is greater than N further comprises: subtracting said gray
level values of said specific group in said first image from said
real-time gray level values of said specific group in said real-time
image to generate a plurality of gray level differences of said
corresponding specific groups; and determining whether an amount
of said gray level differences unequal to zero is greater than N;
wherein the amount of said gray level differences unequal to zero
being greater than N indicates the object of said real-time image
is in motion.
15. The method according to claim 14, wherein N is adjustable for
changing a detection sensitivity of the digital camera.
16. The method according to claim 9, wherein said sequential step
comprises taking photos, taking a motion picture, sounding an alarm,
or flashing a LED light to warn a guard.
Digital Camera Patent Description
FIELD OF THE INVENTION
This invention relates generally to digital cameras, and more particularly
to a method of detecting motion for a digital camera to improve
extra functions in the digital cameras.
BACKGROUND OF THE INVENTION
Conventional digital cameras can simply capture and input image
information. The image information should be further processed by
a general purpose computer and then transferred to a peripheral
apparatus or transferred from the peripheral apparatus into the
computer and then processed. As calculation capability of the computer
is enhanced increasingly, an advanced digital camera is provided
to take a photo image, digitalize the image and store the digital
image. In addition, the digital camera may have a function of taking
a motion picture. The motion image information is converted to a
video format to be filed or played. Thus, the digital camera can
create the video information except for the image information.
As information technology is rapidly developing, the digital camera
has already become a hot digital product in the past few years.
The image information can be directly input into a general-purpose
computer without using conventional film, The image information
may be edited in the computer to operate in coordination with the
popular application of the Internet. Further, the semiconductor
technology is enhanced continuously, causing the production cost
to decrease continuously. The functions of the digital camera are
newly and variously designed; consequently more and more people
expect to have a digital camera. A motion detection function is
especially distinctive for the digital camera.
The digital camera essentially includes four units as schematically
shown in FIG. 1. An image sensor 102 receives an optical image signal,
which is further converted to digital image information. A lens
unit 101 is used to form an image on the image sensor 102. A control
device 103 is used for controlling all units in the digital camera
to input/output image information or further process the image information.
A storage device is used for storing the digital image information.
The optical image signal of an object is formed through the lens
unit 101 on a light sensitive surface of the image sensor 102. The
control device 103 controls the image sensor 102 to convert the
optical image signal to digital image information. The digital image
information is further transferred to the control device 101 or
directly to the storage device 104 if the digital image information
will not be further processed. The storage device 104 can be a nonvolatile
memory, such as EEPROM, Flash, or a volatile memory, such as DRAM,
SRAM. The control device 103 processes or determines the image information
form the image sensor 102 and controls actions of all elements or
units and coordinating operation between the units.
A motion detection function has been available for quite some time.
However, some prior art detecting motion methods have employed expensive
external apparatus, such as infrared or microwave motion detector
devices, and a computer with mass calculation capability. Since
the conventional method of detecting motion utilizes a complicated
mathematical algorithm, the original microprocessor of the control
device of the digital camera is not burdened with the extra functions
for detecting motion. The microprocessor should be replaced by one
with a mass process capability, but this increases the cost of the
digital camera. Besides, the conventional method of detecting motion
needs a large capacity memory and a lot of time to detect motion.
Comparing with the above-mentioned conventional method, the present
invention has an advantage of a simple mathematical algorithm. Therefore,
a need exists to provide a method of detecting motion for digital
cameras to solve the problems of the conventional detecting method.
SUMMARY OF THE INVENTION
A general object of the present invention is to provide a digital
camera with extra functions, including a motion detection function
in addition to the normal functions of a digital camera. The digital
camera will perform some corresponding action, such as take photos
automatically, take a motion picture, sound an alarm, or flash an
LED light to assist a system operator, if the camera detects that
an object is in motion.
An another object of the present invention is to provide a motion
detection method for digital cameras, which method utilizes the
original elements of the digital camera to achieve the motion detection
function and achieve certain accuracy.
In one embodiment of the present invention, a digital camera with
a motion detection function utilizes an image sensor for transferring
image information to a control device. The control device further
processes the image information as follows. Gray level values of
a specific group in the first image are stored. Real-time gray level
values corresponding to the specific group in a real-time image
are subsequently captured. The real-time gray level values of the
specific group in a real-time image are compared with the gray level
values of the specific group in the first image. Next, whether any
one of gray level differences between the specific groups in the
real-time image and the first image is greater than a predetermined
threshold value is determined. A gray level difference greater than
the threshold value indicates that an object of the real-time image
is in motion or else no motion occurs in the real-time image. A
sequential step for the object detected to be in motion is then
performed, such as taking photos automatically, taking a motion
picture, sounding an alarm, or flash an LED light. The real-time
gray level values of the specific group in the real-time image are
stored as the gray level values of the specific group in the first
image.
In another embodiment of the present invention, a method of detecting
motion is provided which includes preliminarily capturing and exposing
a first image by a digital camera. The first image information is
transferred to a control device. Gray level values of a specific
group in the first image are then stored. Real-time gray level values
corresponding to the specific group in a real time image are subsequently
captured. The real-time gray level values of the specific group
in a real time image are compared with the gray level values of
the specific group in the first image. An amount of specific points
with different gray levels between the specific groups in the real-time
image and the first image greater than N indicates that an object
of the real-time image is in motion or else no motion occurs in
the real-time image. A sequential step for the object detected to
be in motion is then performed, such as taking photos automatically,
taking a motion picture, sounding an alarm, or flashing an LED light.
The real-time gray level values of the specific group in the real-time
image are stored as the gray level values of the specific group
in the first image.
Therefore, the method of the present invention utilizes a low cost
digital camera and may be implemented on a simple microprocessor.
A region for detecting motion may be precisely defined by simply
adjusting or setting the lens of the digital camera.
As mentioned above, the present invention provides a method of
detecting motion that merely uses a simple and cheap microprocessor,
such as a PIC, for processing motion-detecting calculations. An
extra capacity memory isn't in necessary for motion detection according
to the present invention. The control device is used for receiving
the image information from the image sensor to further determine
whether an object of the captured image is in motion or not. Therefore,
an extra function of the digital camera is achieved without upgrading
the original elements of the digital camera.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and many of the attendant advantages of this
invention will become more readily appreciated as the same becomes
better understood by reference to the following detailed description,
when taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a schematic block diagram of a digital camera;
FIG. 2 is a drawing illustrating distribution of specific points
in an image in accordance with the method of detecting motion for
a digital camera according to the present invention; and
FIG. 3 is a flowchart of the method of detecting motion for a digital
camera in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention discloses a method of detecting motion for
use in a digital camera without any extra element or apparatus,
which merely utilizes the original elements of the digital camera.
Referring to FIG. 1, the present invention is stored in the storage
device 104 of the control device 103. Then, an extra function of
the digital camera, such as security, can be achieved. The method
of detecting motion in accordance with the present invention utilizes
the control device 103 to control the image sensor 102 performing
repeated actions of exposing images. The control device 103 then
receives the image information from the image sensor 102 after each
exposing action. The control device calculates the image information
including information of a specific group in the image. Confirmation
of the calculated result indicates an object of the image is in
motion. Otherwise, the object of the image is motionless or no motion
occurs in the captured image. The image information received from
the image sensor 102 does not need to be stored in a random access
memory before being calculated by the control device 103. Thus,
the image information may be directly calculated or be stored in
the image storage device to wait for further processing by another
peripheral apparatus.
A specific region selected from an image for detecting is defined
as the specific group in the present invention. The specific group
includes one specific point or a plurality of specific points, as
can be seen in FIG. 2. The amount of the specific points depends
on the user's demands; it may be one, ten, or more. A demand for
more specific points requires more complicated while accuracy increases.
The plurality of specific points on the image is arranged in order
to form the specific group. Referring to FIG. 2, the specific group
201 includes 12 specific points uniformly distributed over the image,
which indicates detection of an entire image. The specific group
202 includes 19 specific points of which 10 specific points are
distributed around the edge of the image and 9 specific point are
concentrated on a central portion of the image. This indicates that
the detection region is the entire image but is focused on the central
portion of the image. Selection of more points results in detection
of more points, which results in high detecting accuracy. The locations
of the specific points decide the detecting region in accordance
with the motion detection method of the present invention.
FIG. 3 shows a flowchart of the motion detection method for a digital
camera in accordance with the present invention. In one embodiment
of the present invention, a motion detection mode is automatically
set and started when the digital camera is turned on (step 301).
The image sensor 102 exposes, captures and then transfers image
information to the control device 103 (step 302). The control device
103 recognizes automatically the specific points of the specific
group in the first image and stores gray level values G1, G2, G3
. . . of specific points of the specific group in the first image
(step 303). The digital camera captures sequentially a real-time
image and transfers image information to the control device. The
control device 103 recognizes and stores real-time gray level values
P1, P2, P3 . . . corresponding to the specific points of the specific
group in the real-time image (step 304). The real-time gray level
values of the specific group in the real-time image are compared
with the gray level values of the specific group in the first image
(step 305). The gray level values of the specific group in the first
image are subtracted from the real-time gray level values of the
specific group in the real-time image to generate a plurality of
gray level differences D1, D2, D3 . . . of the corresponding specific
groups. Whether any one of gray level differences between the specific
groups in the real-time image and the first image is greater than
a predetermined threshold value T (step 306) is determined. The
predetermined threshold value is adjustable; selection of a lower
threshold value results in greater accuracy in motion detection.
In the specific group, any one of the gray level differences greater
than the threshold value (Dx>T) indicates that an object of the
real-time image is in motion (step 307). Otherwise, the object of
the real-time image is motionless or no motion occurs in the real-time
image (step 311). If any one of the gray level differences is determined
to be greater than the threshold value (Dx>T), a sequential step
is then automatically performed (step 308), such as taking photos,
taking a motion picture, sounding an alarm, or flashing an LED light
to assist a system operator or a guard.
In another embodiment of the present invention, a mode of detecting
motion is automatically set and started when the digital camera
is turned on (step 301). The image sensor 102 exposes, captures
and then transfers image information to the control device 103 (step
302). The control device 103 recognizes automatically the specific
points of the specific group in the first image and stores gray
level values G1, G2, G3 . . . of specific points of the specific
group in the first image (step 303). The digital camera captures
sequentially a real-time image and transfers image information to
the control device. The control device 103 recognizes and stores
real-time gray level values P1, P2, P3 . . . corresponding to the
specific points of the specific group in the real-time image (step
304). The real-time gray level values of the specific group in the
real-time image are compared with the gray level values of the specific
group in the first image (step 305). The gray level values of the
specific group in the first image are subtracted from the real-time
gray level values of the specific group in the real-time image to
generate a plurality of gray level differences D1, D2, D3 . . .
of the corresponding specific groups. Whether an amount of specific
points with different gray level between the specific groups in
the real-time image and the first image is greater than N (step
306) is determined. In other words, whether the amount of the non-zero
gray level differences of the specific points is greater than the
N value is determined. The N value is adjustable; selection of a
lower N value results in a more accurate motion detection. In the
specific group, the amount of specific points with non-zero gray
level differences greater than N indicates that an object of the
real-time image is in motion (step 307). Otherwise, the object of
the real-time image is motionless or no motion occurs in the real-time
image (step 311). If the amount of specific points with non-zero
gray level differences greater than N is determined, a sequential
step is then automatically performed (step 308), such as taking
photos, taking a motion picture, sounding an alarm, or flashing
an LED light to assist a system operator or a guard.
An example of the specific group 201 having 12 specific points
in FIG. 2 is illustrated as follows. P1 is representative of the
gray level value of a specific point 1, P2 is representative of
the gray level value of a specific point 2 . . . P12 is representative
of the gray level value of a specific point 12. G1 is representative
of the gray level value of the specific point 1 in the first image,
G2 is representative of the gray level value of a specific point
2 in the first image . . . G12 is representative of the gray level
value of a specific point 12 in the first image. Then, G1 is compared
with P1, G2 with P2 . . . G12 with P12, respectively, to generate
a plurality of gray level differences D1, D2 . . . D12. In the first
preferred embodiment of the present invention, whether any of the
gray level differences D1, D2 . . . D12 is greater than the threshold
value T is determined to indicate that the object in the detecting
region is in motion. For example, T=25, any one of the gray level
differences D1, D2 . . . D12 greater than 25, which indicates the
object in the detecting region is in motion. On the other hand,
all the gray level differences D1, D2 . . . D12 are smaller than
25, which indicates that no motion has occurred in the detecting
region. In the second embodiment of the present invention, an amount
of the corresponding specific points with different gray level greater
than N value is determined to indicate that the object in the detecting
region is in motion. For example, N=5, 5 specific points of the
12 specific points with different gray level value indicate that
the object in the detecting region is in motion. On the other hand,
the amount of the specific points with different gray level values
is less than 5, which indicates that no motion has occurred in the
detecting region.
The above threshold value T and N value both are adjustable to
represent a sensitivity of the motion detection function for the
digital camera. If the values are set large, which means that any
motion of the object is detected when variation of the gray level
value is large enough or the amount of the specific points with
different gray level value is large enough. If the values are set
small, which means that any motion of the object is detected when
few of the specific points with different gray level value are detected,
the sensitivity is higher than the above.
Finally, the real-time gray level values of the specific group
in the real-time image are stored as the gray level values of the
specific group in the first image (step 312). The original gray
level values of the specific group in the first image described
above are replaced to continue with the next detecting motion. Furthermore,
to avoid detecting repeatedly when the object is in motion, a flag
parameter F is introduced in the procedure. The parameter F is set
equal to 0 when no motion occurs, whereas the parameter F is set
equal to 1 when the object is in motion. The parameter F is first
checked when proceeding with the next detecting motion procedure
(step 313). If the parameter F is equal to 0, the motion detection
steps are then sequentially performed. If the parameter F is equal
to 1, the motion detection steps are stopped for a few seconds (step
314). The parameter F is reset equal to 0 (step 315) to continue
the motion detection steps.
As is understood by a person that skilled in the art, the foregoing
preferred embodiment of the present invention are illustrative rather
than limiting of the present invention. It is intended to cover
various modifications and similar arrangements included within the
spirit and scope of the appended claims, the scope of which should
be accorded the broadest interpretation so as to encompass all such
modifications and similar structure.
While the preferred embodiment of the invention has been illustrated
and described, it will be appreciated that various changes can be
made therein without departing from the spirit and scope of the
invention. |