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Digital Camera Patent Abstract
A method of focusing a digital camera module with an image sensor
including capturing an image of a test target with the digital camera
module, determining a focus quality of the image with the image
sensor, outputting a signal related to the focus quality of the
image from the digital camera module to a focusing station external
to the digital camera module, and determining whether a position
of a lens from the image sensor within the digital camera module
should be altered to improve a focus quality of subsequently captured
images.
Digital Camera Patent Claims
1. A method of focusing a digital camera module with an image sensor,
the method comprising: capturing an image of a test target with
the digital camera module; determining a focus quality of the image
with the image sensor; providing a signal related to the focus quality
of the image from the image sensor to a focusing station external
to the digital camera module; and determining whether a position
of a lens from the image sensor within the digital camera module
should be altered to improve a focus quality of subsequently captured
images.
2. The method of claim 1, wherein determining the focus quality
of the image includes determining a variance of a spatial first
derivative of the image.
3. The method of claim 2, wherein determining the variance of the
spatial first derivative of the image includes determining the spatial
first derivative of the image.
4. The method of claim 2, wherein the variance of the spatial first
derivative of the image is determined by analyzing only one or more
regions of interest of the image, and wherein the one or more regions
of interest collectively form less than 50% of the entire captured
image.
5. The method of claim 1, wherein the signal has a voltage level
directly proportionate to the focus quality of the image.
6. The method of claim 1, wherein the image is a second image captured
after a first image, and further wherein the signal is a binary
signal indicating that the focus quality of the second image is
one of improved focus quality, decreased focus quality, and the
same focus quality as compared to a focus quality of the first image.
7. The method of claim 1, further comprising: adjusting the position
of the lens from the image sensor to improve the focus quality of
subsequently captured images.
8. The method of claim 7, wherein adjusting the position of the
lens is repeated a plurality of times, wherein each time includes
moving the lens in an increment equal to a preset distance.
9. The method of claim 8, wherein repeatedly adjusting the position
of the lens includes positioning the lens relative to the image
sensor to optimize focus quality.
10. The method of claim 7, wherein adjusting the position of the
lens includes determining a direction the lens is to be adjusted
to improve the focus quality.
11. A digital camera module for capturing an image depicting a
test target, the digital camera module comprising: an image sensor
configured to operate in a focus mode in which the image sensor
is configured to determine a focus quality of the captured image
and to provide a signal relating to the focus quality; and a lens
spaced from the image sensor, wherein a distance the lens is spaced
from the image sensor is adjustable based upon the focus quality
of the captured image.
12. The digital camera module of claim 11, wherein the image sensor
is configured to determine the focus quality by determining a variance
of the image.
13. The digital camera module of claim 12, wherein the image sensor
is configured to determine the variance based upon one or more regions
of interest of the image, wherein the one or more regions of interest
collectively form less than 95% of the image.
14. The digital camera module of claim 13, wherein the one or more
regions of interest are selected based upon a position of the test
objects upon the test target.
15. The digital camera module of claim 11, wherein the digital
camera module is a fixed-focus camera module.
16. A focusing station for fixing the focus of a digital camera
module, the focusing station comprising: an actuating assembly configured
to interface with a barrel of a digital camera module; a microcontroller
configured to receive a signal from the digital camera relating
to a focus quality of an image captured by the digital camera module
and to determine which direction to rotate the barrel to improve
the focus quality of images based upon the signal received from
the digital camera module.
17. The focusing station of claim 16, wherein the signal is an
analog signal having a voltage directly proportional to the focus
quality of the image captured by the digital camera module.
18. The focusing station of claim 16, wherein the signal is a binary
signal indicating whether the focus quality of the image has improved
since a previous rotation of the barrel.
19. The focusing station of claim 16, wherein the microcontroller
not configured to receive video input from the digital camera module.
20. The focusing station of claim 16, further comprising: a test
target including a background and a plurality of discrete solid
color objects, each of the discrete solid color objects being of
a color contrasting the background; and wherein the focusing station
receives the camera module in a position to capture an image of
the test target.
21. A method of determining focus quality of a camera module, the
method comprising: providing a test target including a background
and at least one object on the background, wherein the background
and the at least one object have contrasting colors; capturing an
image of the test target with the camera module; and analyzing a
region of interest within the image to determine the focus quality
of the camera module, wherein the region of interest depicts a portion
of the background and a portion of the at least one object and is
less than the entire captured image.
22. The method of claim 21, wherein analyzing the region of interest
includes determining the variance of the region of interest.
23. The method of claim 21, wherein the method comprises: analyzing
a plurality of regions of interest, wherein each of the plurality
of regions of interest depicts a portion of the background and a
portion of the at least one object, and wherein the plurality of
regions of interest are collectively less than the entire captured
image.
24. The method of claim 23, wherein the at least one object is
a plurality of objects, and each of the plurality of regions of
interest depicts a portion of the background and a portion of a
different one of the plurality of objects.
25. The method of claim 23, wherein the plurality of regions of
interest are positioned to provide a collective focus quality of
the entire captured image upon analyzing the plurality of regions
of interest.
26. The method of claim 21, further comprising: programming an
image sensor of the camera module with knowledge of the positions
of the region of interest prior to capturing the image of the test
target, wherein the image sensor analyzes the region of interest
based upon the programmed knowledge.
Digital Camera Patent Description
BACKGROUND
[0001] Conventional digital cameras are configured to collect light
bouncing off of a subject onto an image sensor through a lens. The
image sensor immediately breaks the light pattern received into
a series of pixel values that are processed to form a digital image
of the subject.
[0002] Digital image technology is being used with increasing popularity
leading to increasing production volume. The increased production
volume is due not only to the increasing popularity of conventional
digital cameras but also due to miniature fixed-focused digital
cameras being incorporated into various end products, such as mobile
telephones (cellular telephones), personal digital assistants (PDAs),
and other electronic devices.
[0003] During the manufacture of fixed-focused digital camera modules,
it is desirable to optimize the positioning of the lens with respect
to the image sensor to provide for a relatively well-focused digital
image. Conventionally, a camera module is processed within a focusing
station. Once placed in the focusing station, the camera module
is activated to produce either a still picture or a video signal
output depicting a focus target. In order to analyze the picture
or video output, the focusing station utilizes a commercial piece
of hardware, such as a frame grabber or digital frame grabber, which
is used to capture the digital video signals from the camera module
for storage in memory of a computer processing unit, such as a personal
computer, within the focusing station.
[0004] The degree of focus of the images stored within the memory
of the station are analyzed by the personal computer to determine
the level of camera module focus and whether or not the camera module
focus needs to be adjusted. Accordingly, in this conventional operation,
the camera module merely outputs the same video or signal streams
that the camera module outputs during ordinary use of the camera
module. The focusing station breaks down, stores, and performs calculations
to the ordinary camera module output to determine the level of camera
module focus. In this regard, a fair amount of development and money
is spent to provide the focusing system.
SUMMARY
[0005] One aspect of the present invention provides a method of
focusing a digital camera module with an image sensor. The method
includes capturing an image of a test target with the digital camera
module, determining a focus quality of the image with the image
sensor, outputting a signal related to the focus quality of the
image from the digital camera module to a focusing station external
to the digital camera module, and determining whether a position
of a lens from the image sensor within the digital camera module
should be altered to improve a focus quality of subsequently captured
images.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Embodiments of the invention are better understood with
reference to the following drawings. Elements of the drawings are
not necessarily to scale relative to each other. Like reference
numerals designate corresponding similar parts.
[0007] FIG. 1 is a block diagram illustrating one embodiment of
the major components of a digital camera.
[0008] FIG. 2 is an exploded, perspective view of one embodiment
of a camera module assembly of the digital camera of FIG. 1.
[0009] FIG. 3 is a perspective view of one embodiment of the camera
module of FIG. 2 within a focus station.
[0010] FIG. 4 is a front view of one embodiment of a test target
of the focusing station of FIG. 3.
[0011] FIG. 5 is a focus optimization graph illustrating a general
focus optimization concept.
[0012] FIG. 6 is a flow chart illustrating one embodiment of a
focus optimization method for the camera module of FIG. 2 and based
upon the concept of FIG. 5.
[0013] FIG. 7 is a flow chart illustrating a process of determining
variance of an image within the focus optimization process of FIG.
6.
[0014] FIG. 8 is a front view illustrating shifting of a test target
according to the focus optimization process of FIG. 6.
DETAILED DESCRIPTION
[0015] In the following Detailed Description, reference is made
to the accompanying drawings, which form a part hereof, and in which
is shown by way of illustration specific embodiments in which the
invention may be practiced. In this regard, directional terminology,
such as "upon," etc., is used with reference to the orientation
of the Figure(s) being described. Because components of embodiments
of the present invention can be positioned in a number of different
orientations, the directional terminology is used for purposes of
illustration and is in no way limiting. It is to be understood that
other embodiments may be utilized and structural or logical changes
may be made without departing from the scope of the present invention.
The following Detailed Description, therefore, is not to be taken
in a limiting sense, and the scope of the present invention is defined
by the appended claims.
[0016] FIG. 1 is a block diagram illustrating major components
of a digital camera 10. Camera 10 includes a lens 12, an image sensor
14, a shutter controller 16, a processor 18, a memory 20, an input/output
(I/O) interface 22, a shutter button 24, a liquid crystal display
(LCD) 26, and a user input device 28. In operation, when a user
presses shutter button 24, processor 18 and shutter controller 16
cause image sensor 14 to capture light bouncing off of a subject
(not shown) through lens 12. Image sensor 14 converts the captured
light into pixel data, and outputs the pixel date representative
of the image to processor 18.
[0017] The pixel data is stored in memory 20, and captured images
may be displayed on LCD 26. In one embodiment, memory 20 includes
a type of random access memory (RAM) and non-volatile memory, but
can include any suitable type of memory storage. In one embodiment,
memory 20 includes a type or programmable read-only memory (PROM)
such as electrically erasable programmable read-only memory (EEPROM).
Memory 20 stores control software 30 for controlling processor 18.
[0018] I/O interface 22 is configured to be coupled to a computer
or other appropriate electronic device (e.g., a PDA, a mobile or
cellular telephone, etc), for transferring information between the
electronic device and digital camera 10 including downloading captured
images from camera 10 to the electronic device. User input device
28 allows a user to vary the user definable settings of the camera
10.
[0019] FIG. 2 illustrates an exploded view of a fixed-focus camera
module 40 for use in conventional digital cameras 10 or for incorporating
into other electronic devices such as components, PDAs, cellular
phones, etc. Camera module 40 includes image sensor 14, an optional
infrared filter (IRF) 42, a housing 44, lens 12, and a barrel 46.
In one embodiment, image sensor 14 is a charge couple device (CCD)
or a complimentary metal oxide semiconductor (CMOS) device. In one
embodiment, image sensor 14 not only is capable of capturing images
but also includes circuitry able to process the captured images.
Image sensor 14 is connected to an output pin 48 or other communication
device extending from image sensor 14 to a point external to housing
44. Output pin 48 permits signals or other information to be communicated
to other devices. In one embodiment, outlet pin 48 outputs an analog
of binary signal.
[0020] In one embodiment, image sensor 14 is adapted to function
under at least two modes including a general video or photograph
output mode and a focus test mode, as will be further described
below. In one embodiment, image sensor 14 is mounted to a substrate
or housing bottom 49. In one embodiment, IRF 42 is placed upon image
sensor 14. IRF 42 filters the light captured by camera module 40
to decrease the contamination of image sensor 14 with infrared (non-visible)
light.
[0021] In one embodiment, housing 44 includes a base portion 50
and an extension portion 52. Base portion 50 includes four side
walls 54 collectively assembled to form base portion 50 in a rectangular
manner. A planar member 56 partially extends between an edge of
side walls 54. Extension portion 52 extends from an external surface
58 of planar member 56.
[0022] In one embodiment, extension portion 52 is centered with
respect to side walls 54. Extension portion 52 is annular in shape
and defines an inner threaded surface 60. In one embodiment, extension
portion 52 is integrally and homogenously formed with base portion
50. In other embodiments, extension portion 52 is integrally secured
to base portion 50.
[0023] Barrel 46 defines a first annular portion 62 and a second
generally annular portion 64. First annular portion 62 defines an
outer threaded surface 66 configured to selectively interact with
inner threaded surface 60 of housing 44. First annular portion 62
is hollow or tubular in order to circumferentially encompass a lens
12. Second annular portion 64 of barrel 46 extends radially outward
and inwardly from first annular portion 62. An aperture 68 is defined
in the center of second annular portion 64. Aperture 68 is preferably
circular. Second annular portion 64 defines an overall outer diameter
greater than an overall outer diameter defined by threaded surface
66 of first annular portion 62. In one embodiment, an outer periphery
70 of second annular portion 64 defines a plurality of teeth 72
circumferentially spaced about outer periphery 70. As such, second
annular portion 64 substantially forms a toothed gear.
[0024] Upon assembly, IRF 42 is placed upon image sensor 14. Housing
44 is secured to substrate 49 to interpose IRF 42 between image
sensor 14 and housing 44. In one embodiment, threaded screws 74
or other fasteners, such as spring clips, etc., are used to couple
housing 44 to substrate 49. In an alternative embodiment, housing
44 is attached to substrate 49 or image sensor 14 with an adhesive
or other compound rather than with fasteners 74. In one embodiment,
housing 44 is coupled to substrate 49 with adhesive and fasteners
74.
[0025] Lens 12 is sized to be secured within first annular portion
62 of barrel 46. In particular, in one embodiment, lens 12 has a
circumferential outer perimeter that interacts with an inner circumference
of first annular portion 62. Barrel 46 is placed at least partially
within extension portion 52 of housing 44. In particular, barrel
46 is placed such that threaded outer surface 66 of barrel 46 interacts
with threaded inner surface 60 of extension portion 52 to selectively
secure lens 12 and barrel 46 to housing 44.
[0026] Rotation of barrel 46 causes barrel 46 to move either further
into or further out of extension portion 52 of housing 44. As a
result, rotation of barrel 46 also serves to move lens 12 either
closer to or further way from image sensor 14. Rotation of barrel
46 and the resulting movement of lens 12 with respect to image sensor
14, thereby, allows camera module 40 to be generally focused.
[0027] Following assembly of camera module 40, camera module 40
is forwarded to or placed within a focusing station 80, one embodiment
of which is illustrated in FIG. 3. Focusing station 80 includes
a microcontroller 82, an actuating assembly 84, a test target 86,
and a light source 88. Microcontroller 82 is adapted to interface
with camera module 40 and is electrically connected to actuating
assembly 84, such as via an electrical connection 90. In one embodiment,
microcontroller 82 includes a module interface 100 for coupling
with output pin 48 of camera module 40. Accordingly, in one embodiment,
module interface 100 is configured to receive at least one of analog
or binary communication signal from output pin 48. In one embodiment,
microcontroller 82 is characterized by an inability to receive video
communication from camera module 40.
[0028] One embodiment of actuating assembly 84 includes a motor
102, a shaft 104, and a toothed wheel or gear 106. Shaft 104 is
electrically coupled to motor 102, which is configured to selectively
rotate shaft 104 about its longitudinal axis as directed by microcontroller
82. Gear 106 is coupled to shaft 104 opposite motor 102. Thus, rotation
of shaft 104 also induces rotation to gear 106 about an axis of
shaft 104.
[0029] In one embodiment, gear 106 includes a plurality of teeth
108 extending radially from the remainder of gear 106 and circumferentially
spaced from each other about the entire periphery of gear 106. In
one embodiment, actuating assembly 84 is positioned with respect
to microcontroller 82 so a portion of teeth 108 of gear 106 interface
with a portion of teeth 72 of camera module 40 when microcontroller
82 is coupled with camera module 40. Accordingly, upon rotation
of gear 106, barrel 46 will be rotated at a similar speed but in
an opposite direction.
[0030] Test target 86 is generally planar and is spaced from microcontroller
82 such that upon selective coupling of microcontroller 82 with
camera module 40, camera module 40 will be directed toward test
target 86 to capture an image of test target 86. In particular,
test target 86 is positioned such that upon placement of camera
module 40 within focusing station 80, camera module 40 will be positioned
a distance D from test target 86. In one embodiment, distance D
is equal to about a hyperfocal distance of lens 12 of camera module
40.
[0031] Additionally referring to FIG. 4, in one embodiment, test
target 86 includes at least one high contrast figure or object.
In particular, in one embodiment, test target 86 includes a white
or generally white background 110 with at least one solid black
figure or object 112 having definite boundary lines from background
110. Otherwise stated, the boundary lines between background 110
and FIG. 112 are not blurred or gradual but are definite and crisp.
In one embodiment, object 112 is any solid color with high contrast
to the color of background 110.
[0032] In one embodiment, test target 86 includes a plurality of
solid test objects 112 on background 110. For example, test target
86 includes object 112 in positioned near the center of test target
86 and additionally includes a plurality of additional test objects
114 positioned relatively nearer to and spaced about the periphery
of test target 86. With this in mind, test target 86 is formed in
a general checkerboard-like pattern. Referring to FIG. 3, light
source 88 is directed towards test target 86 and provides test target
86 with illumination and light, which will bounce off test target
86 to be captured by lens 12 of camera module 40.
[0033] During manufacture, camera module 40 is received by focusing
station 80. More particularly, camera module 40 is positioned within
focusing station 80 to couple output pin 48 with module interface
100 of microcontroller 82. Camera module 40 is also positioned to
be directed toward a test target 86 and so a portion of teeth 72
of barrel 46 interface with a portion of the teeth 108 of gear 106.
[0034] FIG. 5 graphically illustrates the relationship of the distance
between lens 12 and image sensor 14 with respect to focus quality.
More particularly, an X-axis 120 represents the distance between
lens 12 and image sensor 14. A Y-axis 122 indicates the focus quality.
The relationship between the two values resembles a bell curve as
illustrated by a curve or line 124. In this respect, an optimum
point of focus occurs at the top of curve 124 generally indicated
at point 126. In one embodiment, the point of optimum focus 126
is the best focus that can be achieved in camera module 40 under
existing conditions within focusing station 80 when being adjusted
in preset increments as will be described below.
[0035] Due to the relationship illustrated in FIG. 5, during the
manufacture of fixed-focus camera modules 40, the distance between
lens 12 and images sensor 14 is adjusted to achieve an optimum distance
that ensures the images captured by camera module 40 appear focused
on image sensor 14. As such, this optimum distance generally corresponds
to point of optimum focus 126. The terms "optimum focus,"
"point of optimum of focus," etc. as used herein refer
to the best relative focus level that can be achieved for camera
module 40 when the position of lens 12 is adjusted at predetermined
increments. Accordingly, optimum focus is not an absolute level
of best possible focus.
[0036] With this above relationships in mind, if camera module
40 was initially assembled to fall at point 128 upon line 124, then
lens 12 would not be positioned to provide the optimum focus quality.
If the distance between lens 12 and image sensor 14 is decreased
from point 128, focus quality would decrease accordingly. Alternatively,
if the distance between the lens 12 and image sensor 14 was increased
from point 128, focus quality of camera module 40 would increase.
[0037] However, if camera module 40 was initially constructed to
fall on point 130, then changes to the distance between lens 12
and image sensor 14 would have the opposite effect as described
above for adjustment from point 128. More specifically, an increase
in the distance between lens 12 and image sensor 14 would decrease
focus quality, while a decrease in the distance between lens 12
and image sensor 14 would increase focus quality. As such, the initial
position in which camera module 40 graphs upon line 124 (more specifically,
whatever the initial position is to the left or right of point of
optimization focus 126) indicates whether or not the distance between
lens 12 and image sensor 14 should be increased or decreased to
increase focus quality. The workings of this relationship illustrated
in FIG. 5 is relied upon to achieve an optimum focus of camera module
40.
[0038] For example, FIG. 6 is a flow chart illustrating one embodiment
of a focus optimization process generally at 150, which is best
described with additional reference to FIG. 3, based upon the concept
of FIG. 5. At 152, camera module 40 is placed within focusing station
80. In particular, camera module 40 is positioned to be selectively
coupled with microcontroller 82 and lens 12 is directed toward and
to capture test target 86. In particular, in one embodiment, camera
module 40 is spaced from but centered with respect to test target
86. In one embodiment, focusing station 80 additionally includes
a jig or other member (not illustrated) to assist in proper positioning
of camera module 40 within focusing station 80.
[0039] Once camera module 40 is properly positioned within focusing
station 80, a portion of gear teeth 108 of actuating assembly 84
interface with a portion of teeth 72 of camera module barrel 46.
At 154, camera module 40 is electrically coupled to focusing station
80. In particular, in one embodiment, microcontroller 82 module
interface 100 receives output pin 48 of camera module 40 to receive
at least one of analog or binary signals from camera module 40.
[0040] At 156, camera module 40 is operated to capture an image
depicting test target 86. However, while in focusing station 80,
camera module 40 is in a focus mode, rather than the general photography
or video mode. Accordingly, upon capturing the image of test target
86, camera module 40 does not directly output a digital representation
of the image or video storage. In one embodiment, the image depicting
test target 86 captures the entirety of test target 86. For example,
when using test target 86 illustrated in FIG. 4, the image depicting
test target 86 depicts background 110 as well as an entirety of
objects 112 and 114.
[0041] At 158, a variance of a spatial first derivative of the
image is determined by image sensor 14 (illustrated in FIG. 2) within
camera module 40. Additionally referring to FIG. 7, in one embodiment,
determining the variance of the image at 158 includes deriving a
spatial first derivative of the image at 160. The first step of
deriving the spatial first derivative of the image is shifting the
original image by one pixel at 162. As generally illustrated in
FIG. 8, the initial or original image 164 depicts test target 86
and accordingly includes representations 167 and 168 depicting objects
112 and 114 (illustrated in FIG. 4), respectively. The original
image 164, which is temporarily stored by image sensor 14, is shifted
in one direction by one pixel. In the embodiment illustrated in
FIG. 8, original image 164 is shifted one pixel in a negative X
direction as indicated by arrow 170 to produce a shifted image,
which is generally indicated with broken lines at 164'.
[0042] At 166, shifted image 164' is subtracted from original image
164 at each pixel being analyzed. For example, in a properly focused
image 164, pixel 174 appears as a black pixel. Alternatively, in
shifted image 164', pixel 174 appears as a white pixel similar to
the target background 110 (illustrated in FIG. 4). By subtracting
shifted image 164' from original image 164 at pixel 174, a large
positive difference is found at pixel 174 due to the extreme difference
between black and white.
[0043] At other pixels, such as pixel 176, original image 164 provides
pixel 176 as white, while shifted image 164' provides pixel 176
as black. Upon subtracting images at 166, a large negative difference
is found. For yet other pixels, the pixels remain either one of
black or white in each of images 164 and 164' resulting in zero
difference upon subtraction.
[0044] Notably, if original image 164 was blurry, pixel 174 may
appear gray in original image 164 and/or shifted image 164'. Therefore,
upon subtraction of shifted image 164' from original image 164,
a relatively lesser positive difference and lesser negative difference
would be derived at pixels 174 and 176, respectively. Accordingly,
the larger the absolute value for the pixel difference or derivative
generally indicates that original image 164 is in better focus than
an alternative low absolute value for the difference or derivative
at each pixel. Accordingly, once shifted image 164' is subtracted
from original image 164 at each pixel, the first derivative, otherwise
known as a spatial derivative, is determined for the image 164.
[0045] At 180, the difference or derivative found at each pixel
in 166 is squared to account for the negative or positive characteristic
of the result. By squaring the difference at each pixel, negative
differences can be compared directly with positive differences wherein
higher absolute or squared values generally indicate a higher degree
of focus. At 182, the squared values arrived at 180 are added together
to determine a sum of the squared pixel derivatives or differences
to arrive at the variance of the spatial first derivative of the
image. The variance provides a focus metric of the image 164 is
a direct indication of the focus quality of camera module 40. More
specifically, the higher the variance of the spatial first derivative
of image 164 the better the focus quality of camera module 40.
[0046] At 184, the variance is output from camera module 40 to
microcontroller 82 via the electrical connection between microcontroller
82 and camera module 40. In one embodiment, the variance is output
to microcontroller 82 as an analog signal. More specifically, the
relative variance level is output with differing levels of voltage
to microcontroller 82, where higher voltages indicate higher variances
and vice versa. Accordingly, the voltage level output is directly
proportionate to the variance and focus quality. In one embodiment,
rather than outputting a voltage indicating variance level to the
microcontroller, in one embodiment, the camera module outputs binary
communication, such as a +1 value when variance is improving at
-1 value when variance is decreasing. In this embodiment, additional
comparative steps of the focus optimization process are completed
by the image sensor rather than the focusing station microcontroller.
[0047] At 186, microcontroller 82 determines if this was the first
time through the focus optimization process 150. If it is determined
this was the first time through the focus optimization process 150,
then at 188, microcontroller 82 signals motor 102 to rotate gear
106 in a first direction by a predetermined increment of rotation.
Since teeth 108 of gear 106 interact with teeth 72 of barrel 46,
rotating of the gear 106 causes barrel 46 of image controller to
also rotate. Due to the threaded connection between barrel 46 and
housing 44, the rotation of barrel 46, and therefore lens 12, moves
both barrel 46 and lens 12 further into housing or further out of
housing 44 a predetermined increment or amount.
[0048] Once the distance of lens 12 from image sensor 14 has been
altered in a first direction (i.e. either closer to or further away)
from image sensor 14 at a predetermined increment, steps 156, 158,
184, and 186 are repeated. If at 186, it is determined that this
is not the first time through the focus optimization process 150,
then at 190, microcontroller 82 determines if the variance related
signal is improving as compared to the variance related signal received
the previous time through the sequence. In particular, if the second
variance related signal is higher than the first variance related
signal, then the variance related signal is improving. Conversely,
if the second variance related signal is less than the first variance
related signal, then the variance related signal is not improving.
[0049] If the variance related signal is found to be improving,
then at 192, the microcontroller 82 signals actuating assembly 84
to adjust the distance between lens 12 and image sensor 14 in the
same direction lens 12 was previously adjusted at step 188. For
example, if actuating assembly 84 rotates gear 106 clockwise at
step 188, then at step 192, actuating assembly 84 would once again
rotate gear 106 clockwise. In one embodiment, upon each adjustment
the distance between lens 12 and image sensor 14 is changed by a
predetermined increment in the range of about 2 microns to about
20 microns. In a more particular embodiment, each predetermined
increment is in the range of about 5 microns to about 10 microns.
[0050] Following the second adjustment at 192, steps 156, 158,
184, 186, and 190 are repeated. If at 190, it is determined that
the variance related signal is not improving, then at 194, microcontroller
82 signals actuating assembly 84 to adjust the distance lens 12
extends from image sensor 14 (illustrated in FIG. 2) in a direction
opposite the direction lens 12 was adjusted in the most recent previous
step 188 or 192. Otherwise stated, if the motor 102 rotated gear
106 in a clockwise direction in previous step 188 or 192, then at
194, motor 102 rotates gear 106 in a counterclockwise direction.
Accordingly, barrel 46 with lens 12, which was initially moved one
increment closer to image sensor 14 via the clockwise rotation of
gear 106, would now be moved one increment further away from image
sensor 14 via the counterclockwise rotation of gear 106.
[0051] Following the adjustment of lens 12 at 194, then at 196,
microcontroller 82 determines if the variance related signal was
improving prior to the most recent completion of step 190. If is
determined at 196 that the variance related signal was previously
improving, it indicates that the focus quality or variance was increasing
towards the point of optimum focus (see point 126 in FIG. 5) and
actually passed beyond the point of optimum focus 126 to decrease
overall focus quality. Therefore, the adjustment of the distance
between lens 12 and image sensor 14 back by a single increment at
194 returns lens 12 to a distance from image sensor 14 corresponding
to the point of optimum module focus. Therefore, focus testing and
fixing is complete, and at 198, the camera module is forwarded to
the next stage of manufacture.
[0052] Conversely, if at 196 it is determined the variance related
signal was not previously improving, it indicates that lens 12 was
previously being adjusted in the wrong direction to increase focus
quality, in other words, lens 12 was being adjusted to actually
decrease focus quality as described above with respect to FIG. 5.
Therefore, by moving lens 12 in a different direction at 194, lens
12 is now being adjusted in the proper direction to increase focus
quality (i.e. to move toward point of optimum focus 126 illustrated
in FIG. 5). Following the determination at 196 that the variance
related signal was not previously improving and that lens 12 is
now being adjusted in the proper direction, process 150 returns
to step 156 where steps 156, 158, 184, 186, and 190 as well as steps
192 or 194 are complete. The process is continued until focus optimization
process 150 continues to step 198, described above, where optimum
focus of camera module 40 is achieved and the focus of camera module
40 is fixed (i.e. the distance between lens 12 and image sensor
14 is fixed so as not to be adjustable during use of camera module
40).
[0053] In one embodiment, rather than moving past point of optimum
focus 126 in a first direction and backing up a single increment
to return to point 126 as described above, lens 12 is moved from
the first discovery of decreasing variance following previous improvements
in variance a known offset distance in either direction to achieve
a desired level of optimum focus. In one embodiment, after passing
point of optimum focus 126 in a first direction, lens 12 is moved
in the opposite direction to once again pass point of optimum focus
126 to effectively define a range of optimum focus. Upon identifying
the range of optimum focus, in one embodiment, lens 12 is moved
either to the midpoint of the identified range of optimum focus
or moved a predetermined offset from the midpoint to rest at the
desired point of optimum focus. In one embodiment, the method chosen
to determine the desired point of optimum focus is dependent at
least in part upon the mechanical tolerance and precision of camera
module 40 and focusing station 80.
[0054] A focus optimization process and system as described above
permits a large amount of the test process to be actually completed
by the image sensor rather than by the focusing station. By utilizing
processing elements already generally disposed on the image sensor,
the hardware and assembly time of the focusing station can be decreased.
More particularly in one embodiment, the focusing station would
no longer require a computer processing unit with complicated hardware,
such as frame grabbers, and associated software.
[0055] Rather, in one embodiment, the focusing system merely requires
a microcontroller to perform nominal processing tasks and to signal
actuating assembly to alter the distance the lens is spaced from
the image sensor. By decreasing the hardware and preparation needed
to prepare each focusing station, the overall cost of providing
a focusing station is decreased. In addition, by eliminating a frame
grabber step in the focus optimization process, the speed of the
focus optimization process is increased.
[0056] The speed of the focus optimization process 150 can further
be increased by additionally altering the process of determining
the variance of the image depicting test target 86. For example,
as illustrated with additional reference to FIG. 4, rather than
analyzing the entire area of the original image depicting the test
target 86, only the areas of the image depicting at least one region
of interest generally indicated by broken lines 200 are analyzed.
[0057] For example, the focus test mode of camera module 40 may
be configured to only analyze region of interest 200 of the original
image. Since region of interest 200 depicts at least a portion of
the background 110 as well as a portion of the object 112 including
a boundary line between background 110 and object 112, a similar
method of determining the variance is completed as that described
above except for only region of interest 200 rather than the entire
original image is considered. Accordingly, since less pixels are
analyzed, the overall time needed to complete the focus optimization
process is decreased. In this embodiment, image sensor 14 is programmed
with prior knowledge of the layout of test target 86 to ensure the
analyzed region of interest 200 includes a portion of background
120 and a portion of test object 112 as well as the boundary line
formed therebetween.
[0058] In one embodiment, multiple regions of interest are selected
from within the original image and are used to determine the variance
of the image. For example, in one embodiment, not only is region
of interest 200 identified but additional regions of interest 202
are also identified and analyzed. In one embodiment, regions of
interest 200 and 202 are spaced throughout the original image so
the overall focus level achieved by focus optimization method 150
is more indicative of the focus of the image being captured.
[0059] In particular, due to the normally rounded or spherical
cut of lens 12, optimized focus in the center of the image (such
as at region of interest 200) may not indicate optimum focus near
the edges of the image (such as at region of interest 202). Accordingly,
by spacing the regions of interest 200 and 202 at various positions
within the original image, the resulting variance is indicative
of the overall or collective focused quality of the entire image.
Notably, each region of interest 200 or 202 includes at least a
portion of background 110 and object 112 or 114 including a boundary
between background 110 and object 112 or 114. In one embodiment,
regions of interest 200 and 202 collectively define less than 50%
of the entire captured image. In one embodiment, each region of
interest 200 and 202 individually define less than 25% of the captured
image. In one example, each region of interest 200 and/or 202 individually
defines about 5% of the captured image. In this respect, by utilizing
regions of interest 200 and 202, the same general focus optimization
method 150 described above is utilized. In a more particular embodiment,
each region of interest defines less than 2% of the captured image,
and the plurality of regions of interest collectively define less
than 10% of the captured image. However, since a smaller portion
of the captured image is analyzed at each step, the overall speed
of completing the focus optimization method 150 is increased.
[0060] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that a wide variety of alternate and/or equivalent implementations
may be substituted for the specific embodiments shown and described
without departing from the scope of the present invention. This
application is intended to cover any adaptations or variations of
the specific embodiments discussed herein. Therefore, it is intended
that this invention be limited only by the claims and the equivalents
thereof.
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